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Technical Issues Associated with Future Large-Scale Cellulosic Biofuels Production

Part 1: The Argument for Biofuels

00:00:01.18 00:00:05.29 Hello. My name is Chris Somerville.
00:00:06.00 00:00:09.28 I am a Director at an Institution called the Carnegie Institution
00:00:09.29 00:00:12.25 at Stanford University and a Professor at Stanford.
00:00:12.26 00:00:15.11 I am also a scientist at Lawrence Berkeley National Laboratory.
00:00:15.12 00:00:20.03 Today I am going to talk about the argument for biofuels.
00:00:20.04 00:00:24.26 In brief, I am going to first describe why I and a number of other people have
00:00:24.27 00:00:26.26 recently become interested in the possibility
00:00:26.27 00:00:31.06 of obtaining significant amounts of our energy needs through biofuels.
00:00:31.07 00:00:37.08 And then I am going to briefly describe some of the technical issues associated with realizing that vision.
00:00:37.09 00:00:44.04 This slide shows where humans currently get all of our energy.
00:00:44.05 00:00:46.26 We use about 13 terawatts each year.
00:00:46.27 00:00:48.22 And a terawatt is 10 to the 12 watts.
00:00:48.23 00:00:58.05 The red bars on that side show that we get about 85% of our energy from oil, coal, and gas.
00:00:58.06 00:01:01.25 Additionally we get about 10% from biomass,
00:01:01.26 00:01:05.00 that is mostly in the developing world where wood mostly is used.
00:01:05.01 00:01:08.23 And we get a significant amount from nuclear.
00:01:08.24 00:01:12.02 So because we are mostly dependent on fossil fuels-
00:01:12.03 00:01:16.23 and of course the way we use fossil fuels is to burn them,
00:01:16.24 00:01:19.16 but burning releases CO2 into the atmosphere-
00:01:19.17 00:01:23.13 atmospheric CO2 concentration has been increasing during the last century
00:01:23.14 00:01:29.00 and that in turn has recently been shown to be associated with an increase in global mean temperature.
00:01:29.01 00:01:36.13 And this is not unexpected. Arrhenius, a famous chemist of the previous century,
00:01:36.14 00:01:42.29 predicted in 1895 from first principles that increasing the CO2 concentration would be
00:01:43.00 00:01:48.15 associated with or could be associated with increased thermal loading
00:01:48.16 00:01:51.19 because CO2 is a strong infrared absorber.
00:01:51.20 00:01:57.23 The amount of CO2 being released into the atmosphere is projected
00:01:57.24 00:02:01.02 to increase quite strongly in the coming years
00:02:01.03 00:02:02.21 because as shown on this slide, there is
00:02:02.22 00:02:06.12 a relationship between energy use and CO2 released per capita
00:02:06.13 00:02:09.10 and per capita income.
00:02:09.11 00:02:14.05 So this slide, or this graph, shows on a log/log scale
00:02:14.06 00:02:17.13 that for example in the developed world such as the United States,
00:02:17.14 00:02:22.25 we're releasing, or the average person is releasing about 7000 kilograms of CO2 per year,
00:02:22.26 00:02:30.01 and that is associated with a certain degree of average income.
00:02:30.02 00:02:34.06 Whereas a country such as China shown over here,
00:02:34.07 00:02:38.23 they are releasing less CO2 per capita, but they also have a lower income,
00:02:38.24 00:02:41.26 and of course during the coming years it is expected that their economy
00:02:41.27 00:02:43.11 and the economy of China and other developing countries
00:02:43.12 00:02:48.20 will increase strongly and therefore their CO2 emissions will increase strongly.
00:02:48.21 00:02:54.14 So as a result there's been broad interest in modeling
00:02:54.15 00:02:59.21 what this projected increase in CO2 emissions will do to the climate.
00:02:59.22 00:03:05.17 This slide shows a simulation by the Hadley Center in England
00:03:05.18 00:03:10.29 of what's expected to happen as a result of carbon forcing of the climate
00:03:11.00 00:03:14.07 or increased CO2 concentrations in the climate during the next century.
00:03:14.08 00:03:16.21 You can see that by 2100,
00:03:16.22 00:03:20.16 they are projecting as much as a three degree increase
00:03:20.17 00:03:22.12 in mean annual temperature,
00:03:22.13 00:03:29.20 It's generally thought that that will be in most regions of the world deleterious
00:03:29.21 00:03:37.10 because the changes in temperature will alter the flow of, for example, of water around the world,
00:03:37.11 00:03:40.21 rainfall patterns, and changes in rainfall patterns may be very deleterious
00:03:40.22 00:03:44.03 because it will make it difficult to grow enough food
00:03:44.04 00:03:46.04 to feed people in many regions of the world.
00:03:46.05 00:03:53.16 Additionally of course, as other commentators have noted, there are many other changes associated with this such as
00:03:53.17 00:03:59.18 melting of ice packs that could decrease flow of water,
00:03:59.19 00:04:02.02 and other environmental effects.
00:04:02.03 00:04:04.16 Therefore there is broad interest in the possibility
00:04:04.17 00:04:09.13 of finding carbon free or carbon neutral energy sources.
00:04:09.14 00:04:16.26 This slide shows most of the conceivable sources including nuclear.
00:04:16.27 00:04:20.14 So on the far side I have a sort of icon of nuclear
00:04:20.15 00:04:25.06 because one of the ways I like to think about the challenge here
00:04:25.07 00:04:32.02 is the following: that the current rate of increase in energy use world wide is about half a gigawatt,
00:04:32.03 00:04:33.11 that is half a billion watts per day,
00:04:33.12 00:04:38.07 and the average nuclear power plant will produce about 1 gigawatt of energy.
00:04:38.08 00:04:40.18 So one way of thinking about the problems is that
00:04:40.19 00:04:43.15 in order to just keep carbon emissions where they currently are
00:04:43.16 00:04:47.23 we would need to build a new nuclear power plant every two days for the next 50 years.
00:04:47.24 00:04:53.15 That is very challenging so certainly though nuclear may be a part of the long term solution,
00:04:53.16 00:04:55.03 we need to look at the other possibilities.
00:04:55.04 00:05:01.02 This slide shows that hydro, for example over here on the lower corner,
00:05:01.03 00:05:05.11 has mostly been utilized. There is a small amount of capability.
00:05:05.12 00:05:12.21 There's... We could get about two terawatts around the world from tides and currents theoretically.
00:05:12.22 00:05:19.15 That's a calculation done by the Department of Energy in a study published several years ago.
00:05:19.16 00:05:27.03 Similarly we can get about 4 terawatts by using wind, although currently we use very little of that.
00:05:27.04 00:05:33.15 We can get quite a lot, almost all of our needs in principle from geothermal
00:05:33.16 00:05:38.00 but the problem with geothermal is that most of the heat...
00:05:38.01 00:05:42.28 the regions where geothermal is available such as Yellowstone National Park, or Iceland, or New Zealand,
00:05:42.29 00:05:47.22 where there's kind of volcanic activity, are not accessible to big population centers
00:05:47.23 00:05:51.00 and it's hard to transmit that energy to the population centers.
00:05:51.01 00:05:59.21 So although each of these carbon neutral sources has some role to play
00:05:59.22 00:06:03.29 the really big opportunity is solar, and you can see on this scale that solar is off the scale.
00:06:04.00 00:06:06.26 So I am going to go to my next slide and put everything on a log scale
00:06:06.27 00:06:13.06 And now what you can see from this is that solar dwarfs all the other possibilities.
00:06:13.07 00:06:18.09 And the reason for that is that we receive each year about 10,000 times as much energy
00:06:18.10 00:06:20.29 from the sun as all human energy needs.
00:06:21.00 00:06:31.27 So if we go to the next slide when one thinks of solar, inevitably people think that means photovoltaic.
00:06:31.28 00:06:34.29 Photovoltaics are solar cells.
00:06:35.00 00:06:39.12 And indeed, photovoltaics are an important technology,
00:06:39.13 00:06:42.09 but it's somewhat old technology.
00:06:42.10 00:06:46.05 Einstein won the Nobel Prize for the photoelectric effect in 1923.
00:06:46.06 00:06:53.23 And today since that time only three square kilometers of photovoltaics have been manufactured
00:06:53.24 00:06:56.00 in the whole history of the planet.
00:06:56.01 00:06:58.19 To put that in perspective just to meet US energy needs,
00:06:58.20 00:07:02.09 we would need about 26,000 square kilometers
00:07:02.10 00:07:09.18 of photovoltaics to meet our energy needs. So there is a pretty big gap between what we've been able to do so far
00:07:09.19 00:07:10.19 and our needs. And in fact
00:07:10.20 00:07:15.03 the black square over on one side of the United States
00:07:15.04 00:07:19.06 shows the size of that photovoltaic if it was all in one piece.
00:07:19.07 00:07:24.16 In fact if we covered every roof in America with photovoltaics we could get about 7% of our energy.
00:07:24.17 00:07:27.19 So while that is good, but I don't think
00:07:27.20 00:07:30.16 that it is practical to rely on photovoltaics
00:07:30.17 00:07:34.27 as the only way of harvesting solar in the foreseeable future.
00:07:34.28 00:07:40.17 Before I go on to biofuels I do want to mention one other technology
00:07:40.18 00:07:43.08 that I think is going to be important and
00:07:43.09 00:07:45.03 is now under study and that is the idea
00:07:45.04 00:07:51.07 that we may be able to continue using fossil fuels on a fairly large scale as long as we
00:07:51.08 00:07:53.28 remove the CO2 from combustion.
00:07:53.29 00:07:59.04 And so the opportunity here is kind of illustrated in this slide
00:07:59.05 00:08:03.19 in which one can imagine for example in large electricity generating plants
00:08:03.20 00:08:07.07 it may be possible to strip the CO2 out of the smokestack
00:08:07.08 00:08:16.00 and then pump it back into something like a subterranean aquifer or perhaps an old gas and oil fields.
00:08:16.01 00:08:18.09 And the questions that are under study here
00:08:18.10 00:08:21.23 are the degree to which it is possible to do that economically
00:08:21.24 00:08:26.06 but also the degree to which it is possible to keep the CO2 underground.
00:08:26.07 00:08:30.06 And in fact worldwide there are about three big experiments going on.
00:08:30.07 00:08:32.06 This is an illustration of one of them
00:08:32.07 00:08:35.04 called the Sleipner Experiment, which is in the North Sea.
00:08:35.05 00:08:39.02 In this particular experiment there's a gas well
00:08:39.03 00:08:42.07 where they are bringing gas up from a deep gas well
00:08:42.08 00:08:45.15 and then they are stripping CO2 that is contaminating the gas
00:08:45.16 00:08:48.23 and pumping it back into an aquifer at about 1000 meters.
00:08:48.24 00:08:51.26 And so far this experiment suggests that this kind
00:08:51.27 00:08:56.00 of sequestration in saline aquifers can be a promising approach.
00:08:56.01 00:09:00.27 However, in this particular site they are putting a million tons a year into the aquifer
00:09:00.28 00:09:03.04 just to give you a sense of the magnitude of it,
00:09:03.05 00:09:09.13 but we would need 7000 such sites to de-carbonize our fossil fuels.
00:09:09.14 00:09:12.26 While that is possible in theory,
00:09:12.27 00:09:14.22 I think a lot more work is going to be required before we
00:09:14.23 00:09:17.09 know whether that is really practical on a large scale.
00:09:17.10 00:09:20.19 It may be that on a regional scale it may be part of the solution.
00:09:20.20 00:09:23.11 An important part of that
00:09:23.12 00:09:31.14 is to just mention, is that it is also possible when converting fossil fuels
00:09:31.15 00:09:34.10 to instead of just burning them on the spot,
00:09:34.11 00:09:37.13 it is possible to strip hydrogen from the fossil fuels
00:09:37.14 00:09:40.17 and also sequester the CO2. So much of the discussion
00:09:40.18 00:09:43.27 that took place in the last several years about the so-called hydrogen economy
00:09:43.28 00:09:50.02 is mostly associated with that idea which is that it may be possible to re-form fossil fuels
00:09:50.03 00:09:54.06 where we remove the hydrogen, sequester the CO2 and then use the hydrogen as fuel.
00:09:54.07 00:09:56.03 So there are a number of possibilities,
00:09:56.04 00:09:59.02 and the one I really want to focus on however
00:09:59.03 00:10:01.20 is the solar opportunity using plants
00:10:01.21 00:10:06.25 rather than some sort of mechanical devices as a solar collector.
00:10:06.26 00:10:15.25 So the basic story in higher plants is shown here and that is that sunlight
00:10:15.26 00:10:18.01 is of course received by plants through photosynthesis.
00:10:18.02 00:10:22.23 And during photosynthesis plants take energy, photons from sunlight,
00:10:22.24 00:10:26.21 they reduce carbon dioxide and make polysaccharides.
00:10:26.22 00:10:31.07 so higher plants as I'll show in a few moments are mostly composed of polysaccharides.
00:10:31.08 00:10:34.05 And then of course those polysaccharides can be burned to produce work.
00:10:34.06 00:10:39.06 And the combustion releases CO2, so the CO2 cycles around
00:10:39.07 00:10:44.11 and in that respect fuels made from plants can be considered carbon neutral.
00:10:44.12 00:10:47.19 The question that arises, of course,
00:10:47.20 00:10:50.02 and the most important question is
00:10:50.03 00:10:53.04 is there enough land to produce a significant amount of biofuels.
00:10:53.05 00:10:55.06 There is a sense that somehow we need that land
00:10:55.07 00:10:59.20 for food or other purposes and while that is true,
00:10:59.21 00:11:04.13 I think that there is enough land to make a substantial amount of fuel.
00:11:04.14 00:11:06.00 The argument is as follows.
00:11:06.01 00:11:09.29 One can look at the planet as shown in this pie chart
00:11:10.00 00:11:13.15 as about 70% water and 30% land.
00:11:13.16 00:11:17.00 We are getting about 90,000 terawatts of energy from the sun,
00:11:17.01 00:11:25.12 so if we could just capture 1% of that, on the land we would need about 5% of the land at 1% efficiency
00:11:25.13 00:11:27.11 to fulfill all human energy needs.
00:11:27.12 00:11:31.18 Now 1% is feasible.
00:11:31.19 00:11:39.10 This slide shows a plant called Miscanthus giganteus growing on the University of Illinois campus.
00:11:39.11 00:11:42.09 There is a student named Emily Heaton standing in front of it
00:11:42.10 00:11:43.15 to give you a sense of how big it is.
00:11:43.16 00:11:45.07 It is standing about 14 feet tall.
00:11:45.08 00:11:48.23 And this plant is a perennial grass
00:11:48.24 00:11:52.10 that has been growing on the University of Illinois campus for some years.
00:11:52.11 00:11:54.21 And the amount of biomass that accumulates
00:11:54.22 00:11:57.24 above ground during the annual growing season
00:11:57.25 00:12:06.04 represents more than 1% solar efficiency. That is the plants are receiving enough energy
00:12:06.05 00:12:10.10 and storing it in the forms of polysaccharides that it is 1% efficient.
00:12:10.11 00:12:13.27 So I believer that it is possible from first principles
00:12:13.28 00:12:21.11 to obtain enough energy. This slide actually shows how all land is used on the planet.
00:12:21.12 00:12:26.14 And what it shows is that we have about 7% in non-cereals
00:12:26.15 00:12:30.16 and about 5% of the land used in cereals.
00:12:30.17 00:12:34.22 So altogether we use about 12% of the surface of the earth for food production,
00:12:34.23 00:12:37.21 ignoring pasture and range land.
00:12:37.22 00:12:42.10 Therefore from first principles, it seems possible that we might be able
00:12:42.11 00:12:44.11 to afford a few percent for energy production,
00:12:44.12 00:12:46.27 though that needs to be studied in more detail.
00:12:46.28 00:12:55.11 But that would be, at a high level viewpoint, that would be my argument as to why there may be enough land.
00:12:55.12 00:13:00.25 Another important factor in considering the land question is shown here.
00:13:00.26 00:13:04.18 And that is of course the population has expanded very strongly
00:13:04.19 00:13:05.16 and will continue to expand
00:13:05.17 00:13:08.23 very strongly for the next three years.
00:13:08.24 00:13:09.14 We added about 3 billion people to the planet
00:13:09.15 00:13:11.18 during the last fifty years and we
00:13:11.19 00:13:15.18 are expected to add about 3 billion more in the next fifty years.
00:13:15.19 00:13:18.27 So we are certainly going to need to feed these people,
00:13:18.28 00:13:21.23 and what this slide shows is something very fascinating.
00:13:21.24 00:13:24.08 So what the red line shows
00:13:24.09 00:13:27.16 is the amount of the land used to produce cereals
00:13:27.17 00:13:29.22 which are the main staple.
00:13:29.23 00:13:31.25 And by cereals I mean rice and wheat and corn and things like that.
00:13:31.26 00:13:37.12 And you can see that in the early 60s we were using about 600 million hectares.
00:13:37.13 00:13:40.29 A hectare is about two and a half acres.
00:13:41.00 00:13:44.28 And if we were still using the same cultivars
00:13:44.29 00:13:47.15 of cereals today as in the 1960s,
00:13:47.16 00:13:51.06 today we would be using about 1.6 billion hectares
00:13:51.07 00:13:56.13 of land for cereals. But because plant breeders and agronomists
00:13:56.14 00:13:58.25 have made improvements in the productivity of our plants
00:13:58.26 00:14:01.05 you can see that today actually we are still only using
00:14:01.06 00:14:02.24 about 600 million hectares worldwide.
00:14:02.25 00:14:06.08 So plant breeders and agronomists have saved
00:14:06.09 00:14:11.06 about a billion of hectares in land from cereal production.
00:14:11.07 00:14:14.28 And that process needs to continue as we go forward
00:14:14.29 00:14:16.12 so that we can continue to feed peoplem
00:14:16.13 00:14:19.03 but it also, I think, conveys something
00:14:19.04 00:14:21.19 very interesting about the importance of basic research
00:14:21.20 00:14:24.23 on plant productivity which is that if you care about the environment
00:14:24.24 00:14:28.02 one of the really largest effects you can have
00:14:28.03 00:14:30.24 is to contribute to our continued ability
00:14:30.25 00:14:33.08 to increase plant productivity in a sustainable way.
00:14:33.09 00:14:39.04 And I... so this will be true broadly in terms of biofuels as well,
00:14:39.05 00:14:43.20 while that is land use is fungible so knowledge about plants
00:14:43.21 00:14:47.03 can be used to make food or can be used to make fuels now.
00:14:47.04 00:14:52.07 So I think the imperative for understanding plant biology has gotten more important.
00:14:52.08 00:14:57.27 Now another way of looking at the problem of whether there is enough land is shown here.
00:14:57.28 00:15:00.23 Although this just deals with the US situation.
00:15:00.24 00:15:08.11 In 2005, the Department of Energy and the US Department of Agriculture asked some scientists
00:15:08.12 00:15:12.16 in those organizations to analyze what the capability of the United States is
00:15:12.17 00:15:16.14 to produce biofuels. And this pie chart shows the results of their study
00:15:16.15 00:15:19.06 in which they went sort of county by county around the United States
00:15:19.07 00:15:21.27 and they analyzed land use and productivity.
00:15:21.28 00:15:24.27 And they concluded that in the United States
00:15:24.28 00:15:29.09 we could produce about 1.3 billion dry tons
00:15:29.10 00:15:33.00 of plant biomass that is excess to all of our other needs.
00:15:33.01 00:15:37.18 And this would not include any invasion of the national forests
00:15:37.19 00:15:41.25 or anything that would be considered environmentally destructive,
00:15:41.26 00:15:45.01 or any change in our ability to produce food.
00:15:45.02 00:15:48.01 To put that in perspective, 1.3 billion dry tons
00:15:48.02 00:15:54.04 can theoretically be converted into about 130 billion gallons of ethanol
00:15:54.05 00:15:58.00 using projected technical improvements that I will talk about later.
00:15:58.01 00:16:05.12 And to put that in perspective we currently use about 140 billion gallons of gasoline.
00:16:05.13 00:16:08.23 So on a gallon for gallon basis this study
00:16:08.24 00:16:14.26 would suggest that just with existing excess biomass productivity in the United States,
00:16:14.27 00:16:19.08 we could produce almost all, about two thirds in fact of our energy needs.
00:16:19.09 00:16:23.09 As you can see from the pie chart
00:16:23.10 00:16:28.23 the sources of the projected biomass vary a bit.
00:16:28.24 00:16:31.16 So for example it is projected that corn stover,
00:16:31.17 00:16:34.18 meaning the stalks and leaves of corn plants,
00:16:34.19 00:16:36.04 could produce about 20% of that.
00:16:36.05 00:16:39.28 We have about 90 million acres of corn.
00:16:39.29 00:16:44.12 And we could get about 3.5 tons per acre of corn stalks.
00:16:44.13 00:16:50.26 Additionally we actually pay farmers, you can see down here in the so called orange zone,
00:16:50.27 00:16:54.09 we pay farmers not to farm about 36 million acres
00:16:54.10 00:16:57.24 in the so called CRP lands.
00:16:57.25 00:17:00.18 And in theory these lands could be brought into production
00:17:00.19 00:17:03.22 for the production of perennial grasses
00:17:03.23 00:17:06.12 that could contribute a certain amount as well.
00:17:06.13 00:17:09.19 So by this analysis also it seems as though there is enough
00:17:09.20 00:17:12.21 land to meet any of our needs.
00:17:12.22 00:17:18.09 Now while I applaud the DOE study and the USDA study,
00:17:18.10 00:17:24.20 I think that in the long run we may not
00:17:24.21 00:17:28.08 end up using crop residues because in many cases
00:17:28.09 00:17:29.29 the cost of collecting them
00:17:30.00 00:17:35.01 because there are not a very large amount per acre,
00:17:35.02 00:17:40.00 the cost of collecting them and processing them may not be worthwhile.
00:17:40.01 00:17:42.00 And I think it likely that in the long run
00:17:42.01 00:17:44.04 because land use is fungible
00:17:44.05 00:17:48.19 we are going to evolve towards the use of a new type of crop,
00:17:48.20 00:17:49.28 which I would call an energy crop.
00:17:49.29 00:17:53.02 A highly productive plant species that can be
00:17:53.03 00:17:55.17 grown specifically for energy production.
00:17:55.18 00:17:59.25 And one of the reasons for this, and furthermore, these crops are going to be,
00:17:59.26 00:18:03.08 I believe, mostly perennial grasses.
00:18:03.09 00:18:05.12 C4 grasses, that Is what we call them.
00:18:05.13 00:18:10.09 So C4 refers to a type of photosynthesis that makes very efficient use of water.
00:18:10.10 00:18:11.20 And I'll come back to that in a moment.
00:18:11.21 00:18:17.15 This slide shows one of the reasons that we are interested in perennial crops
00:18:17.16 00:18:18.13 as opposed to annuals.
00:18:18.14 00:18:24.02 So you can see that the blue line shows the annual photosynthesis rate
00:18:24.03 00:18:28.24 of corn during the cycle during the year.
00:18:28.25 00:18:31.11 And what you observe by looking at it is
00:18:31.12 00:18:35.03 that in the beginning of the spring the corn seedlings come up
00:18:35.04 00:18:37.06 and they begin photosynthesizing
00:18:37.07 00:18:41.08 and then as the crop fills out the field the photosynthesis rate peaks
00:18:41.09 00:18:46.11 and then the crop starts to decline as it senesces.
00:18:46.12 00:18:51.17 The yellow line shows the same cycle for, the annual photosynthetic cycle,
00:18:51.18 00:18:54.25 for two perennial crops,
00:18:54.26 00:18:58.15 Miscanthus and Spartina, and you can see that
00:18:58.16 00:19:00.25 the area under the curve of the perennials
00:19:00.26 00:19:03.06 is much higher than the area under the curve of the annual,
00:19:03.07 00:19:07.14 and that is because the perennial grasses start the year off
00:19:07.15 00:19:11.08 from a large root that overwinters in the soil.
00:19:11.09 00:19:13.09 And that root is pretty full of nutrients that stimulate rapid
00:19:13.10 00:19:17.22 growth of the plant at the beginning of the annual cycle.
00:19:17.23 00:19:22.12 So you can see just by looking at the area under these curves
00:19:22.13 00:19:24.23 that the perennial grasses can be much more
00:19:24.24 00:19:27.28 productive per acre than any annual crop.
00:19:27.29 00:19:31.15 So I've introduced Miscanthus once before,
00:19:31.16 00:19:36.16 and I just want to say this is a good example of a perennial C4 grass.
00:19:36.17 00:19:41.18 This plant has been cut every year for the past 7 years to the ground,
00:19:41.19 00:19:45.11 had the biomass removed and processed.
00:19:45.12 00:19:48.11 No irrigation is required in this particular case.
00:19:48.12 00:19:50.09 No fertilizer has yet been applied to it.
00:19:50.10 00:19:56.25 And so in general terms the input costs of producing this are quite low.
00:19:56.26 00:20:00.24 There is no runoff because it's not fertilized.
00:20:00.25 00:20:06.05 And the immense root system captures nutrients.
00:20:06.06 00:20:09.28 Additionally because this plant is usually harvested at the end of the cycle,
00:20:09.29 00:20:12.03 as I'll show in a moment,
00:20:12.04 00:20:14.00 it supports wildlife during the year
00:20:14.01 00:20:16.19 so it is generally considered environmentally attractive.
00:20:16.20 00:20:18.26 Another species that is much talked about as
00:20:18.27 00:20:22.02 a dedicated energy crop is switch grass shown here.
00:20:22.03 00:20:29.17 And switch grass is not quite as big and impressive as Miscanthus,
00:20:29.18 00:20:33.23 but in certain regions it may be preferable
00:20:33.24 00:20:38.03 because plants of course, the growth of plants responds to temperature,
00:20:38.04 00:20:42.05 climate, and water availability.
00:20:42.06 00:20:44.09 So these are two examples.
00:20:44.10 00:20:45.14 They are both C4 grasses,
00:20:45.15 00:20:48.08 and they both make efficient use of water.
00:20:48.09 00:20:53.18 As I mentioned a few moments ago it is envisioned that these plants will be
00:20:53.19 00:20:55.27 left standing throughout the year and
00:20:55.28 00:20:59.17 in the winter you can see that there is actually snow on the ground here
00:20:59.18 00:21:01.12 when this Miscanthus crop is being harvested.
00:21:01.13 00:21:04.08 They can be harvested at this time of year.
00:21:04.09 00:21:08.08 And one of the advantages of this late season harvesting
00:21:08.09 00:21:14.08 is that these perennial grasses have this tendency to withdraw their mineral nutrients out of the vegetative
00:21:14.09 00:21:17.19 parts of the plant and store it back in the roots.
00:21:17.20 00:21:20.16 And that is very attractive for sustainability
00:21:20.17 00:21:24.27 because it means that the nutrients are recycled each year
00:21:24.28 00:21:26.16 and the harvesting of the biomass
00:21:26.17 00:21:29.04 to produce fuel doesn't remove nutrients,
00:21:29.05 00:21:30.26 or it removes fewer nutrients
00:21:30.27 00:21:35.09 from the field than with an annual crop that doesn't go through
00:21:35.10 00:21:38.10 this annual cycle of withdrawing the nutrients back into the roots.
00:21:38.11 00:21:42.02 It is one of the arguments, another argument, for using perennials.
00:21:42.03 00:21:46.23 So I believe that during the next 25 years or so
00:21:46.24 00:21:49.26 we may see some new crops appear
00:21:49.27 00:21:52.29 and indeed this image of the US
00:21:53.00 00:21:55.02 It is from a Department of Energy study
00:21:55.03 00:22:01.03 showing that in different zones of the US new crops may appear.
00:22:01.04 00:22:03.05 So for example down here in the green zone
00:22:03.06 00:22:04.28 you see things like Miscanthus and switch grass,
00:22:04.29 00:22:09.10 whereas up in the Northern regions where it is a bit colder
00:22:09.11 00:22:16.17 and the terrain is different, there are things such as willows may be used as an energy crop.
00:22:16.18 00:22:18.22 They can be cut each year at ground level and they will regrow.
00:22:18.23 00:22:24.25 Now the main limitation as to where these crops are going to grown
00:22:24.26 00:22:27.09 is actually shown here.
00:22:27.10 00:22:28.25 This is a rain fall map of the United States.
00:22:28.26 00:22:35.12 And what it shows is that over here on the left-hand side,
00:22:35.13 00:22:41.21 the colors indicate that there is very little water whereas
00:22:41.22 00:22:45.02 all the green regions show where the rainfall occurs.
00:22:45.03 00:22:52.16 So in general terms it is likely that the biomass crops are going to grown here east of the Mississippi
00:22:52.17 00:22:54.15 where there is adequate rainfall.
00:22:54.16 00:22:56.16 This is also true globally.
00:22:56.17 00:22:59.27 So in this particular image of the world
00:22:59.28 00:23:03.00 The regions that are colored blue
00:23:03.01 00:23:06.29 are where it is too cold to get large amount of biomass.
00:23:07.00 00:23:09.05 Regions where it is red it is too dry,
00:23:09.06 00:23:14.14 so you can see for example the Amazon basin and parts of Argentina
00:23:14.15 00:23:20.20 also the US Midwest have adequate rainfall to produce enough plants.
00:23:20.21 00:23:24.12 Similarly on this... if we look at the rest of the world
00:23:24.13 00:23:28.01 you can see there are regions of Africa, China, or Southeast Asia
00:23:28.02 00:23:34.06 and Europe that have adequate amounts of rainfall and temperature,
00:23:34.07 00:23:38.24 whereas unfortunately much of the former Soviet Union is a bit too cold.
00:23:38.25 00:23:46.06 So if I were to summarize what I am trying to say over the last few minutes.
00:23:46.07 00:23:50.12 I think I've mentioned most of these points, but I would like to just reiterate.
00:23:50.13 00:23:54.17 I think we are moving towards a situation where we are going to develop perennials
00:23:54.18 00:23:59.15 grasses or other perennial plants as energy crops and that these will
00:23:59.16 00:24:03.08 be more environmentally benign than field crops.
00:24:03.09 00:24:06.08 They have low fertilizer and chemical inputs.
00:24:06.09 00:24:09.18 The late harvest supports biodiversity.
00:24:09.19 00:24:14.24 Something I didn't mention yet, unlike field crops which are generally one genotype,
00:24:14.25 00:24:21.05 we envision that the perennial energy crops will certainly be mixed genotypes,
00:24:21.06 00:24:25.10 so that pest and pathogen pressures don't build up.
00:24:25.11 00:24:28.27 If you only have one genetic type in a field,
00:24:28.28 00:24:34.01 pests and pathogens will get specialized on it and it could be very destructive.
00:24:34.02 00:24:39.19 So we will certainly have mixed genotypes with regard to disease and pest resistance,
00:24:39.20 00:24:45.24 possibly even mixed species to decrease those pressures.
00:24:45.25 00:24:48.22 Indeed, the work of an ecologist named David Tilghman ???
00:24:48.23 00:24:52.20 has emphasized the importance of mixed species
00:24:52.21 00:24:54.23 in grass land productivity.
00:24:54.24 00:24:57.00 And I think we don't really know yet
00:24:57.01 00:24:59.15 what the species that will actually
00:24:59.16 00:25:02.15 be used are. There's interest in many species.
00:25:02.16 00:25:05.05 I showed two that are high interest right now,
00:25:05.06 00:25:07.16 but there are many more very highly productive species
00:25:07.17 00:25:09.25 that have not really been investigated in the past
00:25:09.26 00:25:12.21 because they weren't useful for food products.
00:25:12.22 00:25:16.23 So this is an emerging area that I think will be quite interesting.
00:25:16.24 00:25:18.18 I think a big issue is going to be
00:25:18.19 00:25:22.04 to make sure that these plants can be grown and harvested
00:25:22.05 00:25:23.18 year after year in a sustainable way.
00:25:23.19 00:25:25.28 There’s not a lot of information on this,
00:25:25.29 00:25:28.13 however this slide shows
00:25:28.14 00:25:31.19 that at least in the case of corn there are concerns.
00:25:31.20 00:25:35.07 So this is some unpublished data from a USDA scientist named Ken Vogel.
00:25:35.08 00:25:40.18 And what Ken is showing in this slide is that in the year 2000
00:25:40.19 00:25:41.18 when this experiment started,
00:25:41.19 00:25:47.13 he began removing half of the corn stalks from a corn field and leaving the other half in the soil.
00:25:47.14 00:25:50.14 And you can see that actually be year 2 or 3
00:25:50.15 00:25:58.01 after that the yield of the corn was declining relative to the controls where they left all the corn stalks on the land.
00:25:58.02 00:26:05.11 The thinking about or the rationale about the explanation for this is that Ken thinks that the cornstalks
00:26:05.12 00:26:09.13 are required to support microbial diversity in the soil,
00:26:09.14 00:26:13.09 or just microbial processes I should say more generally.
00:26:13.10 00:26:18.08 Those are required for correct nutrient flow in the soils.
00:26:18.09 00:26:20.13 So this is now an area of active study.
00:26:20.14 00:26:23.15 Experiments that are being carried out are things such as
00:26:23.16 00:26:27.01 taking soil samples from crops that have been harvested
00:26:27.02 00:26:30.18 in different ways with different amounts of biomass left on the field
00:26:30.19 00:26:34.15 and then analyzing the species composition in the soil by, for example,
00:26:34.16 00:26:36.20 sequencing all the organisms present
00:26:36.21 00:26:39.25 so that they can be identified based on their DNA sequence.
00:26:39.26 00:26:48.09 I think another area that is going to need a lot of work I alluded to it earlier
00:26:48.10 00:26:51.15 is that pests and pathogens can be very devastating.
00:26:51.16 00:26:55.14 We don't really know yet since no energy crops,
00:26:55.15 00:26:57.23 dedicated energy crops, have been grown on a large scale.
00:26:57.24 00:27:02.28 Whether... the degree to which they will be susceptible to pests and pathogens.
00:27:02.29 00:27:09.16 This slide is showing a soy bean field that is being devastated
00:27:09.17 00:27:13.11 as you can see there's a lot of sort of yellowish plants here,
00:27:13.12 00:27:15.21 being devastated by a sort of new pathogen
00:27:15.22 00:27:19.10 that has arrived in the United States called Asian Soy Rust.
00:27:19.11 00:27:22.06 So this is a continuing problem in agriculture
00:27:22.07 00:27:24.23 and forestry. There's a continuing battle
00:27:24.24 00:27:29.16 between production of plants and the pests and pathogens
00:27:29.17 00:27:33.10 that tend to specialize on them as the acreage increases.
00:27:33.11 00:27:40.26 I think the... there are many questions associated with this.
00:27:40.27 00:27:44.20 This is a... the whole area of biofuels has been under investigation
00:27:44.21 00:27:48.29 for thirty years really, ever since the first oil shocks of the 1970s,
00:27:49.00 00:27:55.12 but in a fairly low way. And so now that there is renewed interest
00:27:55.13 00:27:57.18 there are a lot of unanswered questions.
00:27:57.19 00:28:00.26 Among those that typically come up
00:28:00.27 00:28:02.29 in discussions are:
00:28:03.00 00:28:04.28 What are the probable effects on food security?
00:28:04.29 00:28:09.21 It is certainly true that in some regions of the world
00:28:09.22 00:28:12.01 people have difficulty feeding themselves
00:28:12.02 00:28:16.15 and they are dependent on food exports from the developed world.
00:28:16.16 00:28:19.26 I don't know the answer to that and I and colleagues
00:28:19.27 00:28:26.13 are just beginning to really try and understand those effects.
00:28:26.14 00:28:29.03 It is possible for example that it is actually
00:28:29.04 00:28:30.24 the exports of food from the developing world
00:28:30.25 00:28:33.23 that are the source of the food production problems
00:28:33.24 00:28:34.08 elsewhere in the world.
00:28:34.09 00:28:40.11 That it is because the United States and Europe heavily subsidize agriculture,
00:28:40.12 00:28:42.12 we are able to sell grain around the world
00:28:42.13 00:28:45.28 or even give it away below the cost of production.
00:28:45.29 00:28:48.07 And that may suppress the formation
00:28:48.08 00:28:51.16 of indigenous agricultural production systems.
00:28:51.17 00:28:54.03 That needs to be understood.
00:28:54.04 00:28:58.18 There is concern whether there will be tradeoffs in environmental effects.
00:28:58.19 00:29:03.05 For example we need to in order to expand the amount
00:29:03.06 00:29:11.21 of land available for biofuels, will that lead to destruction of important ecological zones. Deforestation.
00:29:11.22 00:29:14.21 And indeed there are examples where that has taken place.
00:29:14.22 00:29:18.12 For example, during the past several years
00:29:18.13 00:29:23.16 the European Union has mandated that fuels in Europe
00:29:23.17 00:29:26.13 require a certain percentage of bio-diesel.
00:29:26.14 00:29:32.06 Unfortunately Europe cannot produce enough oils, biological oils,
00:29:32.07 00:29:37.09 or fats to meet that, so they have been importing palm oil,
00:29:37.10 00:29:42.10 and that in turn has led to the expansion of tropical oil palm elsewhere in the world,
00:29:42.11 00:29:44.19 in Malaysia, leading to deforestation
00:29:44.20 00:29:46.28 which is an undesirable effect.
00:29:46.29 00:29:51.14 So I think that although there is some promise and from first principles
00:29:51.15 00:29:53.00 it seems that there is enough land,
00:29:53.01 00:29:57.19 we need to really look at around... at the global situation and make sure
00:29:57.20 00:30:00.01 that demand for biofuels in the developed world
00:30:00.02 00:30:03.05 doesn't lead to undesirable ecological
00:30:03.06 00:30:06.09 or even social effects in other regions of the world.
00:30:06.10 00:30:12.12 For example, when I mentioned social effects,
00:30:12.13 00:30:15.14 land ownership is not equitable in many regions of the world.
00:30:15.15 00:30:20.09 And it could be that large landowners may decided to devote
00:30:20.10 00:30:22.26 their land to the production of biofuels
00:30:22.27 00:30:24.24 at the expense of food production in those countries.
00:30:24.25 00:30:28.10 So one of the ways of dealing with that can be
00:30:28.11 00:30:31.24 to have international trade policies that discourage
00:30:31.25 00:30:36.26 that kind of activity that is essentially restricting the market
00:30:36.27 00:30:40.20 for biofuels from certain regions.
00:30:40.21 00:30:45.10 where land use is not equitable.
00:30:45.11 00:30:51.05 I think that these are just a few examples of the issues before us.
00:30:51.06 00:30:53.26 I think they illustrate the fact that
00:30:53.27 00:30:58.11 as with any large change such as is anticipated
00:30:58.12 00:31:02.11 with the production of biofuels on a large scale,
00:31:02.12 00:31:11.26 there are many issues that need to be discovered across a range of scientific and non-scientific disciplines.
00:31:11.27 00:31:15.17 So social studies and economics now
00:31:15.18 00:31:18.09 need to be integrated with our technical vision
00:31:18.10 00:31:22.28 of what is possible before we actually engage in a large scale activity.
00:31:22.29 00:31:30.14 As I am going to say in the next segment of this series,
00:31:30.15 00:31:32.17 since there are a number of technical issues
00:31:32.18 00:31:36.13 that are preventing the adoption of large scale biofuels today,
00:31:36.14 00:31:40.26 I think we have time to think through what the issues are
00:31:40.27 00:31:46.16 and to implement appropriate regulatory and trade policies.
00:31:46.17 00:31:54.23 So from first principles, or I have tried to illustrate sort of what I see
00:31:54.24 00:31:59.19 as the possible future in terms of biofuels.
00:31:59.20 00:32:03.14 This slide sort of illustrates a situation in which we can imagine
00:32:03.15 00:32:09.12 sustainable production of cellulosic biomass or other types of biomass
00:32:09.13 00:32:16.24 being processed and recycled so that we do move towards a world in which
00:32:16.25 00:32:21.19 we are able to produce energy in a sustainable way.
00:32:21.20 00:32:27.13 Having said that, I do want to emphasize that although I said earlier we could probably produce
00:32:27.14 00:32:31.28 all human energy needs from biological sources,
00:32:31.29 00:32:37.23 the goals of everybody that I know of, including the Secretary of Energy,
00:32:37.24 00:32:41.07 that are currently working in this field are to
00:32:41.08 00:32:44.16 merely try to substitute for a significant part of our transportation fuel.
00:32:44.17 00:32:50.14 The transportation fuels are the most difficult ones because they are used in relatively small amounts.
00:32:50.15 00:32:52.24 and in highly distributed systems.
00:32:52.25 00:32:55.22 It seems likely for example that we
00:32:55.23 00:33:01.21 can meet our electricity needs or any kind of needs that can be met with electricity
00:33:01.22 00:33:04.18 can be dealt with through photovoltaics or wind,
00:33:04.19 00:33:06.08 or to some extent hydro or nuclear,
00:33:06.09 00:33:10.21 and sequestration from fossil fuel utilization.
00:33:10.22 00:33:14.12 So the main target right now is biofuels
00:33:14.13 00:33:17.12 and indeed the Secretary of Energy's goals
00:33:17.13 00:33:24.11 in the United States is that we will obtain thirty percent of our transportation fuels from biofuels by 2030.
00:33:24.12 00:33:29.22 That gives you some sense of the time frame in which we expect these transitions to take place.

Part 2: Cellulosic Biofuels

00:00:02.14 00:00:04.08 My name is Chris Somerville.
00:00:04.09 00:00:08.24 I am a scientist in the Carnegie Institution and a Professor at Stanford University,
00:00:08.25 00:00:11.08 and a scientist at Lawrence Berkeley National Laboratory.
00:00:11.09 00:00:13.13 In this segment I am going to be talking about
00:00:13.14 00:00:17.04 the technical aspects of making cellulosic biofuels.
00:00:17.05 00:00:22.22 To begin with I want to just address what's meant by biofuels.
00:00:22.23 00:00:30.18 And in general terms there are 4 ways that are currently... or 4 types of biofuels.
00:00:30.19 00:00:36.05 The first one, of course, is just to burn plant biomass
00:00:36.06 00:00:40.01 to produce heat, and the heat can be used for various purposes.
00:00:40.02 00:00:45.14 Diesel can be made by plants, and I'll illustrate that in a moment.
00:00:45.15 00:00:50.15 Sugars can be converted to ethanol by fermentation
00:00:50.16 00:00:56.01 and cellulose can be converted to ethanol or other fuels by fermentation.
00:00:56.02 00:01:01.11 So I am going to start off by just briefly describing some of the issues associated with
00:01:01.12 00:01:05.20 these, and then I am going to focus mostly on cellulosic biofuels
00:01:05.21 00:01:09.29 because that's where the really large scale opportunity seems to be.
00:01:10.00 00:01:13.22 If we look at this slide what one sees
00:01:13.23 00:01:18.20 is a section of a single cell. So you can see over here, here's a piece of a cell wall.
00:01:18.21 00:01:26.14 And these white bodies are fat globules inside the cell.
00:01:26.15 00:01:28.22 And the cell is from an embryo in a plant seed.
00:01:28.23 00:01:31.27 So many plants store large amounts of oil
00:01:31.28 00:01:38.24 as carbon reserves for embryo development during germination.
00:01:38.25 00:01:42.22 So these oils can be produced in relatively large amounts
00:01:42.23 00:01:47.11 and in fact are responsible for about thirty percent of the calories in the human diet.
00:01:47.12 00:01:51.19 In plants, the principal component of the oils is triglyceride.
00:01:51.20 00:01:55.11 So a molecule in which the glyceride backbone
00:01:55.12 00:01:59.19 or glycerol backbone is esterified with three long chain fatty acids.
00:01:59.20 00:02:05.20 And these fatty acids can be cleaved off and converted to methyl esters with very high efficiency.
00:02:05.21 00:02:13.05 It is something that can be done on your kitchen counter with reagents you can buy in a grocery store.
00:02:13.06 00:02:21.09 So for that reason there's a lot of interest in making so-called biodiesel
00:02:21.10 00:02:24.16 by reclaiming used cooking vegetable oils for example,
00:02:24.17 00:02:32.23 or tallow from animal processing and indeed there's currently about 65 biodiesel plants
00:02:32.24 00:02:35.12 in the United States and many more elsewhere in the world.
00:02:35.13 00:02:38.03 And there's about fifty more currently in development.
00:02:38.04 00:02:41.20 And it's a concept that is much in the news.
00:02:41.21 00:02:46.15 And indeed it is a good... if the vegetable oil
00:02:46.16 00:02:50.25 or the tallow is available, it is a good technology.
00:02:50.26 00:03:00.07 The diesel engine was in fact invented... when it was first invented the fuel was vegetable oil.
00:03:00.08 00:03:05.01 So it's very compatible with the current engine design.
00:03:05.02 00:03:11.24 However, if one is looking at the big picture in terms of to what degree
00:03:11.25 00:03:14.12 biodiesel can contribute to our energy needs,
00:03:14.13 00:03:15.18 it is not very promising.
00:03:15.19 00:03:20.05 This slide is from the Congressional Research Office
00:03:20.06 00:03:25.29 and it is showing basically that we use about 140 million gallons of gasoline in the United States each year.
00:03:26.00 00:03:30.29 We use about 60 billion gallons of diesel.
00:03:31.00 00:03:34.06 And according at least to the Congressional Research Office, if we convert
00:03:34.07 00:03:39.11 all the plant and animal fats in the United States to fuel. We could only get about
00:03:39.12 00:03:42.22 3 and a half billion gallons.
00:03:42.23 00:03:47.27 Now of course that would remove a large amount of the calories
00:03:47.28 00:03:50.15 from the human food supply,
00:03:50.16 00:03:54.25 so that is probably not really feasible.
00:03:54.26 00:03:57.19 And in fact the 65 plants that I referred to are shown over here
00:03:57.20 00:04:04.15 and as you can see they don't even really come above the line in the national needs.
00:04:04.16 00:04:09.14 So there's probably not a very good opportunity in biodiesel.
00:04:09.15 00:04:15.13 One of the reasons is that the main oil seed crops, for example,
00:04:15.14 00:04:17.26 soy bean in the United States is the big oil seed crop,
00:04:17.27 00:04:21.22 it will only produce about 70 gallons per acre of oil.
00:04:21.23 00:04:26.09 By contrast, in the previous segment I talked about cellulosic biofuel plants
00:04:26.10 00:04:30.21 or cellulosic plants which could make biofuels.
00:04:30.22 00:04:39.02 And on an acre of a really productive grass we could only get about 2500 gallons of ethanol.
00:04:39.03 00:04:42.21 So because land use is fungible it seems very unlikely that in the future
00:04:42.22 00:04:49.05 we will be satisfied making 650 gallons of biofuel when we could be making 2500 gallons of ethanol.
00:04:49.06 00:04:55.24 Now there is one plant that does have much higher productivity, and that is oil palm,
00:04:55.25 00:04:59.09 which is a tropical plant that grows within 15 degrees of the equator.
00:04:59.10 00:05:08.12 And this plant, because in those regions the growing season is all year round
00:05:08.13 00:05:12.02 and the plants have a long life span,
00:05:12.03 00:05:17.07 these plants are very efficient accumulators of oil.
00:05:17.08 00:05:20.16 You can see that up in the crown of the plant they have a fruit
00:05:20.17 00:05:22.24 that's a lot like an avocado.
00:05:22.25 00:05:30.04 And as with an avocado, the mesocarp tissue contains about 35% oil,
00:05:30.05 00:05:32.09 and the kernel, this white region in the center,
00:05:32.10 00:05:35.26 is also used for... contains a lot of oil.
00:05:35.27 00:05:41.22 So these plants can produce up to 10 metric tons of oil per hectare per year.
00:05:41.23 00:05:48.26 And in fact, a very large amount of palm oil is used worldwide.
00:05:48.27 00:05:54.13 Of course the problem with the oil palm
00:05:54.14 00:05:56.03 is that in those regions of the world where it can work,
00:05:56.04 00:06:00.10 there are a lot of tropical forests that are under pressure
00:06:00.11 00:06:07.00 and it needs to be examined the degree to which
00:06:07.01 00:06:11.21 it could be expanded without seriously impairing biodiversity.
00:06:11.22 00:06:15.19 I mean that's the story about palm.
00:06:15.20 00:06:18.28 In the context of biodiesel,
00:06:18.29 00:06:23.17 another idea or another opportunity for producing biodiesel at least in theory
00:06:23.18 00:06:26.27 is that many algae, marine algae,
00:06:26.28 00:06:33.01 produce fairly large amounts of lipid within their cells as lipid droplets.
00:06:33.02 00:06:39.09 So there's interest in the possibility of large scale cultivation of algae for that purpose.
00:06:39.10 00:06:43.25 And indeed a number of companies have sprung up during the past several years
00:06:43.26 00:06:50.14 that are cultivating or trying to establish conditions for large scale cultivation.
00:06:50.15 00:06:56.22 This slide shows a reactor on the roof of a building in Massachusetts.
00:06:56.23 00:07:01.12 I think this is a green fuel reactor as it is called, the name of the company.
00:07:01.13 00:07:06.18 And in this case what they are doing, you may just be able to see that
00:07:06.19 00:07:11.05 these tubes are transporting the algae around, and then there's a kind of a
00:07:11.06 00:07:16.07 big place where sunlight is incident on the algae and the algae are constantly swirling through it.
00:07:16.08 00:07:19.24 And indeed... and there's a smokestack in the background in which
00:07:19.25 00:07:28.20 gases are CO2 enriched. Gases are being bubbled through the cultures to stimulate photosynthesis.
00:07:28.21 00:07:34.01 Although this looks promising, the challenge is the following
00:07:34.02 00:07:39.25 with algae, and that is that sunlight contains on average worldwide
00:07:39.26 00:07:41.28 about two hundred watts per meter squared.
00:07:41.29 00:07:50.13 And since photosynthesis by algae is only maximally about 9 percent efficient,
00:07:50.14 00:07:55.13 it means that actually per meter of algal culture
00:07:55.14 00:08:01.12 the energy that is being captured at maximum efficiency is below 20 watts per square meter.
00:08:01.13 00:08:05.05 And it can be very challenging to build devices such as this
00:08:05.06 00:08:08.13 or many of the other devices that are currently under development
00:08:08.14 00:08:14.01 when the return is only about 20 watts per square meter.
00:08:14.02 00:08:24.13 To put that in perspective, electricity currently sells for as little as 3 cents per thousand watt-hours.
00:08:24.14 00:08:27.12 And so that gives you some sense of what the current challenge is.
00:08:27.13 00:08:39.14 It's been... the idea of actually releasing algae into large open ponds is also discussed,
00:08:39.15 00:08:43.11 but there seems to be a biological problem there because if one tries to grow
00:08:43.12 00:08:50.03 large amounts of algae and apply sort of pressure on the population by harvesting it repetitively
00:08:50.04 00:08:56.03 that leads to selection for strains that can propagate rapidly
00:08:56.04 00:08:59.09 and that in turn leads to strains that don't produce any oil.
00:08:59.10 00:09:06.20 So right now that's the kind of problem with generating large scale algal culture,
00:09:06.21 00:09:11.23 although it may be possible to solve it with some innovative designs in the future.
00:09:11.24 00:09:17.29 When one talks of biofuels today in general it means ethanol,
00:09:18.00 00:09:20.21 produced from one of two main sources.
00:09:20.22 00:09:30.04 In regions such as Brazil, ethanol can be produced from sugar, which is from sugarcane.
00:09:30.05 00:09:33.22 Sugarcane is a very highly productive plant.
00:09:33.23 00:09:39.08 And the canes can be harvested and crushed to release the sugar,
00:09:39.09 00:09:41.08 and the sugar can be fermented with very high efficiency.
00:09:41.09 00:09:51.03 So indeed Brazil currently gets about 40 percent of its transportation fuels by fermentation of sugarcane.
00:09:51.04 00:09:57.09 And that's done on only about 1 percent of the land acreage of Brazil.
00:09:57.10 00:10:04.10 So for Brazil that's been a very important way of establishing energy security
00:10:04.11 00:10:08.17 and stimulating the indigenous industry.
00:10:08.18 00:10:10.24 I think it supports about a million jobs in Brazil.
00:10:10.25 00:10:18.20 In the United States during the past several years we have seen a rapid expansion of production of ethanol from corn grain.
00:10:18.21 00:10:23.05 And this map of the US from the National Corn Growers Association
00:10:23.06 00:10:28.11 shows the location of about more than a hundred of plants.
00:10:28.12 00:10:32.09 You can see all the little dots scattered around the Midwest in particular.
00:10:32.10 00:10:37.18 are the sites where corn grain ethanol plants either exist or are being built.
00:10:37.19 00:10:46.03 And in general terms these plants are mostly owned by farmers or farmer co-ops,
00:10:46.04 00:10:50.08 so farmers are gathering together to process their grain into ethanol
00:10:50.09 00:10:57.24 and these have proven to be very profitable because corn prices have been low over the past 25-30 years.
00:10:57.25 00:11:06.08 The reason that corn is an attractive crop is that it is quite productive and the grain is mostly starch.
00:11:06.09 00:11:09.08 So you can see over here, this is a corn sectioned
00:11:09.09 00:11:14.13 through a corn grain, and everything above the embryo is starch.
00:11:14.14 00:11:19.12 And starch is just a polymer of glucose which can be fermented by yeast with very high efficiency
00:11:19.13 00:11:20.17 to make ethanol.
00:11:20.18 00:11:27.14 So the remaining part of the corn embryo by the way is fed to cattle as cattle food,
00:11:27.15 00:11:32.11 so it is all used, but only the starch is used for ethanol production.
00:11:32.12 00:11:40.27 In general terms, making ethanol from corn is, while it's proven to be very profitable for farmers,
00:11:40.28 00:11:45.03 is not considered very desirable from an environmental standpoint because
00:11:45.04 00:11:51.07 corn uses quite a lot of energy during the growth and harvesting
00:11:51.08 00:11:54.26 and the land manipulations.
00:11:54.27 00:12:02.02 So typically it is thought that if one does a full life cycle analysis of how much growth goes into growing
00:12:02.03 00:12:04.25 harvesting and processing corn
00:12:04.26 00:12:09.06 and compares it to how much energy is returned,
00:12:09.07 00:12:15.12 from the ethanol produced, it's currently estimated that there's only about 1.3 times as much energy
00:12:15.13 00:12:20.14 recovered from the corn as goes into growing it.
00:12:20.15 00:12:24.01 So from an environmental standpoint, that doesn't seem very optimal.
00:12:24.02 00:12:30.13 There are some negative environmental effects with the large scale mono cultures of corns,
00:12:30.14 00:12:33.20 such as quite a lot of run off from fertilizer, for example.
00:12:33.21 00:12:43.21 So recent sort of predictions of where the
00:12:43.22 00:12:47.22 ethanol industry in the United States or in North America
00:12:47.23 00:12:50.15 is likely to go during the coming decades is shown here,
00:12:50.16 00:12:54.00 and in general terms it is thought that corn grain
00:12:54.01 00:13:01.19 or corn grain ethanol will probably saturate at about 12 billion gallons a year.
00:13:01.20 00:13:04.05 We are currently making six billion gallons.
00:13:04.06 00:13:09.18 And the reason for that is that of course until the ethanol boom began corn grain
00:13:09.19 00:13:12.11 was used to feed cattle mostly,
00:13:12.12 00:13:17.00 and so that need has not gone away
00:13:17.01 00:13:17.01 
00:13:17.02 00:13:24.28 so as the use for making fuel has increased then the price of producing animals
00:13:24.29 00:13:28.26 has gone up and a new equilibrium will be established
00:13:28.27 00:13:35.09 in which it won't become economically feasible to use corn grain for fuel.
00:13:35.10 00:13:39.23 In that respect, I think it is worth noting that we have just witnessed or we are witnessing
00:13:39.24 00:13:43.11 a historic, what I think of as a historic event
00:13:43.12 00:13:47.18 in which the value of a bushel of grain and a barrel of oil
00:13:47.19 00:13:51.28 have come into some sort of equilibrium based on the Btu content of those two,
00:13:51.29 00:13:56.05 that is the intrinsic energy content of those two commodities.
00:13:56.06 00:13:59.26 And so even though it is true that the boom in ethanol
00:13:59.27 00:14:02.21 from corn and sugarcane during the last several years
00:14:02.22 00:14:08.01 has priced up, has pushed up the price of food, that will not continue indefinitely.
00:14:08.02 00:14:11.20 I think from about here on it should track the price of oil,
00:14:11.21 00:14:19.24 though because until large scale production of corn ethanol started,
00:14:19.25 00:14:25.14 there was the grain and energy were in different economic sectors,
00:14:25.15 00:14:27.04 but now they are conjoined.
00:14:27.05 00:14:31.26 And so a new equilibrium should be reached approximately.
00:14:31.27 00:14:36.00 Alright so, in thinking about where this is going
00:14:36.01 00:14:39.18 since we can't meet our energy needs with corn grain,
00:14:39.19 00:14:42.19 it is generally thought that what will happen is that during the
00:14:42.20 00:14:47.01 coming years we will start to see an increase in the production of ethanol from cellulose,
00:14:47.02 00:14:49.09 or lignocellulose as it is sometimes called.
00:14:49.10 00:14:53.17 And so mostly what I want to address now is what does that mean
00:14:53.18 00:14:57.18 in a practical sense and what are the challenges with doing that.
00:14:57.19 00:15:07.21 Before I do I want to address one of the general criticisms that is often voiced about making biofuels,
00:15:07.22 00:15:12.16 and that is authors such as Pimental and Patzek have argued
00:15:12.17 00:15:17.22 that, it's generally summarized in the press as,
00:15:17.23 00:15:21.26 that the amount of energy we get out of biofuels
00:15:21.27 00:15:27.11 is less than the amount that goes in, and indeed that's probably not true,
00:15:27.12 00:15:29.23 but I want everyone to understand what their argument really is
00:15:29.24 00:15:31.27 because it has two components.
00:15:31.28 00:15:34.17 And so even though they are critical of the technology,
00:15:34.18 00:15:42.07 Pimental and Patzek would agree that from their paper that if you just grow and harvest
00:15:42.08 00:15:45.06 and burn a plant such as switchgrass, a perennial grass,
00:15:45.07 00:15:46.20 it's of interest to biofuels,
00:15:46.21 00:15:50.10 you can get about a 15-fold energy return. So there's not really any argument
00:15:50.11 00:15:54.00 whether plants can be grown as net energy sources.
00:15:54.01 00:15:59.20 The real argument is the degree to which when one converts the cellulosic biomass
00:15:59.21 00:16:03.25 to liquid fuels you lose a lot of that energy content.
00:16:03.26 00:16:13.14 And so in their analysis, Pimental and Patzek sort of look at the current process and they add up all the energy costs
00:16:13.15 00:16:15.19 that go into actually processing the biomass.
00:16:15.20 00:16:18.19 And you can see from this pie chart which I constructed
00:16:18.20 00:16:24.18 from their paper, they project that a lot of steam and electricity goes into making the biofuels,
00:16:24.19 00:16:29.27 which is true. And so it certainly is... although there is a lot of disagreement
00:16:29.28 00:16:38.14 about their numbers, it is generally true that the current processing of biomass to fuels requires a lot of input energy.
00:16:38.15 00:16:44.19 And so people that are interested in making biofuels a possibility
00:16:44.20 00:16:46.14 are really focused on this general issue.
00:16:46.15 00:16:51.06 How can we decrease the amount of energy that goes into converting cellulosic biomass to fuels
00:16:51.07 00:16:53.23 and that is mostly what I am going to address.
00:16:53.24 00:16:57.29 I think that we can make a lot of improvements.
00:16:58.00 00:17:05.07 So to understand that in general terms we need to sort of look at the overall process of making cellulosic ethanol.
00:17:05.08 00:17:11.11 Shown here. So over on this side, we start with a bale. It's ground up,
00:17:11.12 00:17:17.08 and then typically the biomass fragments are then boiled in hot acid.
00:17:17.09 00:17:20.01 And I'll show you in a few moments what that accomplishes,
00:17:20.02 00:17:26.12 but in general terms it breaks down the biomass into... partially breaks it down,
00:17:26.13 00:17:30.20 into free sugars and fragments of biomass.
00:17:30.21 00:17:36.22 The free sugars can then be neutralized and fermented
00:17:36.23 00:17:39.25 to produce a certain amount of ethanol.
00:17:39.26 00:17:44.18 The remaining solids are then usually treated with enzymes such as cellulases
00:17:44.19 00:17:46.22 that break down the remaining polysaccharides,
00:17:46.23 00:17:49.00 and then those sugars are neutralized and fermented,
00:17:49.01 00:17:52.27 so that at the end one ends up with ethanol.
00:17:52.28 00:17:55.28 And the ethanol is then frequently distilled.
00:17:55.29 00:18:02.14 This is a pretty well known process that emerged from 5000 years or probably more
00:18:02.15 00:18:03.28 of making wine and beer.
00:18:03.29 00:18:08.10 Now to understand what the technical issues are
00:18:08.11 00:18:12.02 in carrying out that process, let's start at the most basic level.
00:18:12.03 00:18:13.20 What is plant biomass made of?
00:18:13.21 00:18:17.03 And you can see that if we take a typical grass composition,
00:18:17.04 00:18:21.13 about 40% of it is cellulose. Then there's a large component
00:18:21.14 00:18:24.00 of something called hemicellulose, which I'll introduce in a moment.
00:18:24.01 00:18:27.12 Another major component is lignin, and then everything else,
00:18:27.13 00:18:33.24 basically the protein and the mineral nutrients are actually quite a small proportion of the total biomass.
00:18:33.25 00:18:41.27 So this slide is a blown up image of a piece of a pine board
00:18:41.28 00:18:46.07 and what we are seeing here for example, there's a cell.
00:18:46.08 00:18:51.06 And where my finger is, that's a cell wall that is surrounding the pine cell.
00:18:51.07 00:18:55.25 And if we look up close at what that cell wall is in this image,
00:18:55.26 00:18:59.15 you can see... this is an electron micrograph by the way, in which
00:18:59.16 00:19:03.20 we are looking down on the surface now of a plant cell wall.
00:19:03.21 00:19:10.04 And what one sees here is a highly interdigitated network of fibers
00:19:10.05 00:19:14.19 that have a dimension of about three to five nanometers.
00:19:14.20 00:19:22.20 And I'll just tell you sort of in advance that those fibers are mostly cellulose that we can see,
00:19:22.21 00:19:26.10 although there are other polymers in the wall, they are a bit small to see.
00:19:26.11 00:19:31.18 So cellulose is a composite material.
00:19:31.19 00:19:37.06 The fibers, the 3 to 5 nanometer in diameter fibers, are made by hydrogen bonding
00:19:37.07 00:19:41.27 approximately 36 chains of beta-1-4 linked glucose.
00:19:41.28 00:19:47.18 So to just remind you, starch is alpha-1-4 linked glucose.
00:19:47.19 00:19:49.25 Cellulose is beta-1-4 linked glucose.
00:19:49.26 00:19:56.02 And so although they have the same sugar, it turns out one is easy to break down.
00:19:56.03 00:19:58.01 The alpha linkage is easy to break down.
00:19:58.02 00:20:00.12 We have enzymes, alpha-amylases, that will degrade it.
00:20:00.13 00:20:02.19 But the beta linkage turns out to be more challenging.
00:20:02.20 00:20:08.28 Cellulose is actually made in the plasma membrane.
00:20:08.29 00:20:13.20 You see here there is a complex, and actually this is what my laboratory mostly is focused on.
00:20:13.21 00:20:15.11 The research I work on specifically
00:20:15.12 00:20:19.23 is we are interested in how it is that the cellulose fibers are made.
00:20:19.24 00:20:22.21 So what we have learned during the past few years is that there's a large,
00:20:22.22 00:20:26.19 probably a 30, sorry, 3 million Dalton complex
00:20:26.20 00:20:30.08 sitting in the plasma membrane with about 36 active sites
00:20:30.09 00:20:33.06 and those active sites spin out these glucan chains
00:20:33.07 00:20:36.25 which hydrogen bond to form the cellulose microfibrils.
00:20:36.26 00:20:39.12 The hydrogen bonding in these microfibrils is
00:20:39.13 00:20:44.10 one of the reasons that cellulose is a very hard and tough material.
00:20:44.11 00:20:47.04 It's not well hydrated.
00:20:47.05 00:20:48.16 In addition, these fibrils are very big.
00:20:48.17 00:20:53.23 So work from our lab has shown that the complexes
00:20:53.24 00:20:58.18 can actually make about 350 nanometers a minute of these fibrils.
00:20:58.19 00:21:04.22 And they make chains that are in full length up to 12 microns in length,
00:21:04.23 00:21:10.00 so I guess that is about 14 or 15 thousand individual sugars per chain.
00:21:10.01 00:21:12.12 So they are pretty big molecules as these things go.
00:21:12.13 00:21:18.22 Okay, well here is a very oversimplified image of what the cell wall actually
00:21:18.23 00:21:23.10 looks like in my favorite model by Maureen McCann and Keith Roberts.
00:21:23.11 00:21:30.06 What this is showing is the cellulose fibrils, the big green things,
00:21:30.07 00:21:38.27 and they in turn are kind of coated with another material, these little red fibrils.
00:21:38.28 00:21:44.25 Those are single molecules of hemi-cellulose, and hemi-cellulose, the most abundant one
00:21:44.26 00:21:51.06 is actually a xylan. What that means is it's a beta-1-4 linked xylose polymer.
00:21:51.07 00:21:55.02 And each of those molecules is about a thousand sugars long
00:21:55.03 00:21:56.10 to give you some sense of the dimension.
00:21:56.11 00:22:02.23 And they hydrogen bond to the surface of the cellulose fibrils, as you can see
00:22:02.24 00:22:06.10 and then they may hydrogen bond in fact to several cellulose microfibrils.
00:22:06.11 00:22:09.28 Additionally there can be, depending on the type of cell wall,
00:22:09.29 00:22:12.17 there can be other polymers in the matrix.
00:22:12.18 00:22:18.02 So in this image there is some sort of filmy looking material called pectins.
00:22:18.03 00:22:22.26 And these are charged poly-saccharides made of uronic acids mostly.
00:22:22.27 00:22:30.13 Additionally in certain types of cell walls, and in mostly the cell walls that are of interest for making biofuels,
00:22:30.14 00:22:33.17 such as the stalks of grasses and wood,
00:22:33.18 00:22:37.21 about a third or a quarter to a third of the material
00:22:37.22 00:22:43.00 is a polyphenolic called lignin shown here,
00:22:43.01 00:22:51.07 and this is kind of a typical example. And if you stare at it what's striking about it
00:22:51.08 00:22:52.26 is that there are a large number of linkages.
00:22:52.27 00:22:58.28 It's very complex. And in fact it is very durable.
00:22:58.29 00:23:02.24 So some of you may have heard of lignite coal?
00:23:02.25 00:23:09.04 Well, lignite and lignin have the same root, and indeed much of the soil is also highly enriched in lignin,`
00:23:09.05 00:23:13.12 because it, because the large number of linkages
00:23:13.13 00:23:16.14 and the types of linkages typically ether or carbon-carbon linkages
00:23:16.15 00:23:19.06 are quite hard to degrade.
00:23:19.07 00:23:25.21 So it is a very durable material, and its role in the plant is probably to provide compressive resistance.
00:23:25.22 00:23:32.13 So on this slide to give you a sense of how this all assembles now at the nanoscale,
00:23:32.14 00:23:39.29 I made a kind of a variant of the nice drawing by McCann and Roberts,
00:23:40.00 00:23:45.02 and then amplified a small region of it to give you a sense of the high resolution
00:23:45.03 00:23:46.13 how these things all fit together.
00:23:46.14 00:23:50.20 So maybe you can just barely see there's the green cellulose microfibril,
00:23:50.21 00:23:53.15 and then it is covered with the hemicellulose strands,
00:23:53.16 00:23:58.15 and then the lignin is in some way covering or wrapped into this material.
00:23:58.16 00:24:03.10 And in fact we know that the lignin is in fact crosslinked to the hemi-cellulose,
00:24:03.11 00:24:05.06 typically through several ferulic esters.
00:24:05.07 00:24:12.24 So this is a very difficult material to really understand.
00:24:12.25 00:24:17.26 The size of most of the components is below our ability
00:24:17.27 00:24:20.15 to image with current imaging technologies,
00:24:20.16 00:24:24.28 and we don't really know what the fine scale structure of this is,
00:24:24.29 00:24:28.05 and in fact that is one of the big research objectives that people in the field have right now
00:24:28.06 00:24:31.16 is trying to see what the nanoscale structure is
00:24:31.17 00:24:36.20 so that we can try to envision ways of breaking it down.
00:24:36.21 00:24:41.17 For example, if it has this kind of structure shown here,
00:24:41.18 00:24:45.12 one explanation for why biomass is so hard to degrade
00:24:45.13 00:24:50.20 is that perhaps the lignin occludes the biomass,
00:24:50.21 00:24:53.14 the polysaccharides, so that enzymes can't get at it.
00:24:53.15 00:24:58.00 And indeed that would be compatible with the evidence such as shown in this slide.
00:24:58.01 00:25:00.05 So what this slide is showing is that
00:25:00.06 00:25:06.05 the rate of hydrolysis, so on that axis is hydrolysis.
00:25:06.06 00:25:10.19 This axis on the bottom is the amount of lignin in the biomass.
00:25:10.20 00:25:13.28 And you can see that there is an inverse relationship between the amount of lignin
00:25:13.29 00:25:16.00 and the rate of enzyme mediated hydrolysis.
00:25:16.01 00:25:21.10 And we think that's due to the fact that because the lignin is kind of coating the cellulose
00:25:21.11 00:25:23.10 and hemicellulose, the enzymes just can't get at it.
00:25:23.11 00:25:28.19 So one of the things then that the pretreatment that I mentioned earlier,
00:25:28.20 00:25:31.19 the boiling in hot acid or related kinds of treatment,
00:25:31.20 00:25:35.17 what we think that does is that it first of all it disrupts hydrogen bonding,
00:25:35.18 00:25:38.18 which causes things to loosen up,
00:25:38.19 00:25:44.01 and secondly, it causes sort of non-specific hydrolysis of the hemi-cellulose.
00:25:44.02 00:25:46.05 So the hemi-cellulose sugars start diffusing away,
00:25:46.06 00:25:49.03 and the linkages to lignins start getting broken,
00:25:49.04 00:25:52.05 so everything starts to loosen up and the enzymes can penetrate.
00:25:52.06 00:26:02.24 So then typically when, or in the past, at least, until we were a bit further along in our
00:26:02.25 00:26:08.20 thinking, the original approach to that idea was to say, well, let's get rid of the lignin.
00:26:08.21 00:26:12.12 So actually a great deal of research has gone into understanding how lignin is made.
00:26:12.13 00:26:14.15 It's shown, the pathway, is shown on this slide.
00:26:14.16 00:26:20.07 So up in this corner you can see that lignin starts from phenylalanine.
00:26:20.08 00:26:23.26 And then through a series of transformations, one ends up
00:26:23.27 00:26:27.03 with a series of so called phenyl-propanoids,
00:26:27.04 00:26:35.09 so phenyl groups, hydroxymethyl, or hydroxylated phenyl groups
00:26:35.10 00:26:36.28 with propane side chains.
00:26:36.29 00:26:39.16 These are secreted out into the cell wall, and then they are polymerized
00:26:39.17 00:26:43.29 in a free radical polymerization reaction.
00:26:44.00 00:26:47.25 And in fact that is why so many different linkages exist in the lignin,
00:26:47.26 00:26:52.19 is that there's about four major phenyl-propanoids, and then they get secreted
00:26:52.20 00:26:55.05 into the wall where they polymerize in all possible combinations.
00:26:55.06 00:27:02.21 It's one of the few processes that I know of in which
00:27:02.22 00:27:06.11 non-enzymatic polymerization takes place on a very large scale.
00:27:06.12 00:27:12.16 Now many years ago, I and other people made mutants of
00:27:12.17 00:27:15.10 higher plants that were defective in lignin,
00:27:15.11 00:27:18.00 and one of them is shown here.
00:27:18.01 00:27:23.29 And this is a... these represent two sections through stems of Arabidopsis.
00:27:24.00 00:27:28.17 And what one sees here, those cells, those are the xylem cells.
00:27:28.18 00:27:32.12 And the blue color reflects actually lignification of these cells.
00:27:32.13 00:27:35.28 So these are cells that transmit water, and down here
00:27:35.29 00:27:39.29 you can see actually right there, there's some cells that are kind of collapsed.
00:27:40.00 00:27:43.22 And so those are the cells in a mutant, a type of mutant,
00:27:43.23 00:27:50.09 that's defective in lignifying the secondary cell wall, so what happens is
00:27:50.10 00:27:55.01 if the lignin is not present, the walls don't have enough compressive resistance,
00:27:55.02 00:27:57.24 and they collapse under the negative pressure of transpiration.
00:27:57.25 00:28:00.00 That is that as the water moves through the vascular tissue,
00:28:00.01 00:28:04.19 and out the top of the plant, a negative gradient is formed, a pressure gradient
00:28:04.20 00:28:11.14 in the tissues, so this in turn causes the plants to have growth defects.
00:28:11.15 00:28:14.12 So unfortunately it doesn't seem very likely
00:28:14.13 00:28:20.06 that we can simply solve the recalcitrance problem as it is called,
00:28:20.07 00:28:22.21 by significantly eliminating lignin.
00:28:22.22 00:28:26.16 There are many conceivable alternative approaches,
00:28:26.17 00:28:29.23 but one approach that we are exploring, I mean, that the field is exploring right now,
00:28:29.24 00:28:34.20 is to make a different type of lignin.
00:28:34.21 00:28:40.27 And to explain that, our basic idea is that because lignin is made in free radical process,
00:28:40.28 00:28:46.12 it's possible that if we made a kind of a molecule
00:28:46.13 00:28:49.04 or engineered plants to make a type of molecule that could be incorporated
00:28:49.05 00:28:52.29 into lignin, but then had a cleavable linkage,
00:28:53.00 00:28:55.03 we might get lignin that still has the right physical properties,
00:28:55.04 00:28:57.20 but could be degraded more easily.
00:28:57.21 00:29:00.24 To give you a sense of that, this molecule, pinoresinol,
00:29:00.25 00:29:06.28 is a normal component of lignin and we can show, or it has been shown by other laboratories,
00:29:06.29 00:29:10.25 that if one feeds this molecule to a plant cell,
00:29:10.26 00:29:14.08 it gets incorporated into the lignin as expected.
00:29:14.09 00:29:19.03 So we think there is a possibility that we could develop plants
00:29:19.04 00:29:23.04 that produce other types of related types of molecules,
00:29:23.05 00:29:25.12 such as this molecule here called rosmarinic acid.
00:29:25.13 00:29:29.02 It's made by many plants, but it is not secreted into the cell wall.
00:29:29.03 00:29:34.07 The nice thing about rosmarinic acid is that it looks a lot like things like pinoresinol,
00:29:34.08 00:29:39.03 in that it's got a pair of phenyl groups with hydroxyls,
00:29:39.04 00:29:42.12 but it has an ester linkage, and that ester linkage
00:29:42.13 00:29:50.24 is readily cleavable both enzymatically or by simple chemical treatments.
00:29:50.25 00:29:54.15 So one possibility is that we may be able to engineer plants to make and secrete
00:29:54.16 00:29:59.14 rosmarinic acid, and then we would get a lignin that has good properties,
00:29:59.15 00:30:02.16 but we can remove it under much more benign circumstances.
00:30:02.17 00:30:14.01 Another general problem in the field is that once lignin and hemicellulose is removed,
00:30:14.02 00:30:17.01 by the hot acid treatment... So I just want to make it clear,
00:30:17.02 00:30:19.17 in case I haven't up to this point, one of our goals
00:30:19.18 00:30:22.10 in making modified lignins would be to get rid of the hot acid treatment.
00:30:22.11 00:30:28.21 The hot acid treatment is one of the things that imposes a lot of costs on the overall process,
00:30:28.22 00:30:32.08 since you have to heat it up to a rather high temperature, and you have to
00:30:32.09 00:30:36.06 engineer containers, you might say,
00:30:36.07 00:30:40.04 that can withstand highly corrosive treatments,
00:30:40.05 00:30:43.15 so that imposes a lot of cost on the overall process.
00:30:43.16 00:30:47.28 So we would like to move towards a system that is basically physiological,
00:30:47.29 00:30:53.12 and the reason we think that it may be possible to move towards a much more physiological circumstance is
00:30:53.13 00:30:57.05 that first of all many organisms such as cattle and termites are
00:30:57.06 00:30:59.05 able to degrade lignocellulose
00:30:59.06 00:31:02.11 and compost heaps do it, and forest floors,
00:31:02.12 00:31:07.18 so there is lots of reason to believe that since nature can do it,
00:31:07.19 00:31:10.04 we can find a more benign route.
00:31:10.05 00:31:18.00 Now a component of doing that is going to be able to find more effective enzymes.
00:31:18.01 00:31:23.00 So under the current process,
00:31:23.01 00:31:26.28 assuming we could deal with the lignin problem by some other method,
00:31:26.29 00:31:30.08 we are still going to have the problem of breaking down the cellulose.
00:31:30.09 00:31:34.17 And there's a class of enzymes called cellulases that can do this,
00:31:34.18 00:31:36.21 but they are... they have very low turnover numbers.
00:31:36.22 00:31:42.07 And that results in a very large amount of enzyme being used.
00:31:42.08 00:31:46.08 So ten years ago just the cost of the enzyme for making a gallon of cellulosic
00:31:46.09 00:31:50.05 ethanol was about five dollars just for the enzyme.
00:31:50.06 00:31:52.20 During the past ten years that has been brought down to about fifty cents a gallon
00:31:52.21 00:31:54.28 for the enzyme, but that is still quite a lot of enzyme.
00:31:54.29 00:32:01.17 To put it in perspective, the starch based cellulose, or sorry, starch based ethanol production,
00:32:01.18 00:32:03.25 requires about 2 cents worth of enzyme.
00:32:03.26 00:32:13.27 So this rather fanciful slide shows an artist's rendition of a cellulase
00:32:13.28 00:32:19.29 sort of extracting a molecule of glucan from a piece of cellulose and hydrolyzing it.
00:32:20.00 00:32:22.14 In fact, of course this can never happen.
00:32:22.15 00:32:27.14 Cellulose can't be sort of pulled out of... or the glucan can't be sort of pulled out of the cellulose chain,
00:32:27.15 00:32:28.16 but that's part of the problem.
00:32:28.17 00:32:35.25 In terms of finding the optimal enzymes, recent advances in high-throughput sequencing
00:32:35.26 00:32:39.22 have created entirely new possibilities. So for example,
00:32:39.23 00:32:44.09 these days it is possible to sequence a whole microbial genome
00:32:44.10 00:32:51.04 in a morning and to annotate it with quite high efficiency at relatively low costs.
00:32:51.05 00:32:56.16 So experiments are underway to understand for example how termites
00:32:56.17 00:33:01.07 are able to chew wood and extract sugars and nutrients from them.
00:33:01.08 00:33:06.21 It turns out it's been known for many years that the termites have about a hundred species of bacteria
00:33:06.22 00:33:12.13 in their guts and now these are being systematically explored to find out what it is,
00:33:12.14 00:33:18.08 what kinds of enzymes those bacteria produce and secrete into the termite gut.
00:33:18.09 00:33:23.29 Similarly, ruminants, such as cattle, also have about a hundred species of bacteria
00:33:24.00 00:33:28.11 that work as consortium to break down hay in the rumen.
00:33:28.12 00:33:33.26 And those are being sequenced, and the enzymes will be characterized in the coming years.
00:33:33.27 00:33:39.19 Compost heaps and forest floors carry out the same process and are similarly being explored
00:33:39.20 00:33:42.15 by metagenomic approaches. In some cases,
00:33:42.16 00:33:46.26 the organisms can't be sequenced, or sorry, they can't be cultivated,
00:33:46.27 00:33:57.22 so the whole mixture of microbial biomasses, the DNA is extracted and is being sequenced,
00:33:57.23 00:34:03.04 and then with a certain probability the genomes can be re-assembled from the total sequence.
00:34:03.05 00:34:12.08 Additionally during the past decade or so, there have been tremendous advances
00:34:12.09 00:34:17.25 in structural biology and protein evolution methods
00:34:17.26 00:34:23.09 that have raised the possibility that we may be able to improve
00:34:23.10 00:34:28.19 the catalytic activity of cellulytic enzymes by rational methods
00:34:28.20 00:34:32.28 or by selecting for improved enzymes in high throughput screens.
00:34:32.29 00:34:41.28 And finally, I think there's a distinct possibility that we can synthesize novel, non-enzymatic catalysts
00:34:41.29 00:34:48.18 that might be useful. Most of the organic chemistry that is done on an industrial scale
00:34:48.19 00:34:53.13 in the world is actually done with synthetic catalysts, rather than biological catalysts.
00:34:53.14 00:34:58.05 And so that's not really been explored yet in the context of biofuels,
00:34:58.06 00:35:04.19 so I think there's a very interesting possibility to see whether a new organometallic catalyst
00:35:04.20 00:35:09.05 can be developed that are able to hydrolyze glycosidic linkages with a high efficiency.
00:35:09.06 00:35:17.08 So I see a lot of opportunities that really build on modern advances in biology and chemistry.
00:35:17.09 00:35:25.02 Finally, I think a very interesting area that illustrates
00:35:25.03 00:35:27.24 how little we know in some respects about what the possibilities
00:35:27.25 00:35:31.07 might be is kind of illustrated in this slide,
00:35:31.08 00:35:34.19 of a drawing of what's called the cellulosome.
00:35:34.20 00:35:41.00 And the importance of this is that, or what the authors are trying to illustrate with this slide
00:35:41.01 00:35:44.22 is that many micro-organisms don't simply secrete enzymes,
00:35:44.23 00:35:49.10 into the milieu around them, where they have some activity,
00:35:49.11 00:35:55.00 but they actually secrete a complex that they then attach as you can see over here,
00:35:55.01 00:36:00.10 this complex is attached through this scaffold to the surface of the microbial cell,
00:36:00.11 00:36:04.19 and then a series of enzymes act in some synergistic way
00:36:04.20 00:36:10.06 that's poorly understood to accelerate the hydrolysis of cellulosic biomass.
00:36:10.07 00:36:14.21 It's not really known how these work, and in fact it's not really known yet what the structures are
00:36:14.22 00:36:18.02 or even what all the enzyme activities are that are associated with them are,
00:36:18.03 00:36:20.13 but it's an active area of research that I think
00:36:20.14 00:36:26.13 illustrates one of the many opportunities that exists
00:36:26.14 00:36:28.10 to use modern biology to discover new principles
00:36:28.11 00:36:31.22 of how biological systems are carrying this out.
00:36:31.23 00:36:37.29 Now another important component of getting, of increasing the overall efficiency
00:36:38.00 00:36:46.04 of the process is that as I have noted earlier, biomass is not just composed of cellulose or glucose,
00:36:46.05 00:36:51.15 but in fact there are other poly-saccharides containing other sugars such as xylose.
00:36:51.16 00:36:59.07 And to make an efficient process, all the sugars in fact have to be converted to fuels.
00:36:59.08 00:37:03.28 So, at present, although we know many micro-organisms that can utilize the other sugars,
00:37:03.29 00:37:09.05 we don't have any industrial strains that are able to
00:37:09.06 00:37:12.29 utilize all of the sugars to make ethanol at an acceptable level.
00:37:13.00 00:37:18.18 So this rather complex pathway illustrates the fact that
00:37:18.19 00:37:25.19 it is possible to imagine integration of glucose and xylose fermentation to ethanol.
00:37:25.20 00:37:31.06 And now much of the work in this field is associated with understanding
00:37:31.07 00:37:34.21 the regulation of these and several other related pathways
00:37:34.22 00:37:40.26 and understanding how to integrate them into an integrated pathway for sugar fermentation
00:37:40.27 00:37:44.01 of all sugars into industrial micro-organisms.
00:37:44.02 00:37:51.24 And I think that these are the kind of problems that probably just reflect our...
00:37:51.25 00:37:55.10 the fact that not enough work has been done.
00:37:55.11 00:38:00.02 I think no miracles are going to be required to understand how to integrate these pathways.
00:38:00.03 00:38:05.21 This is where recent advances in synthetic biology and systems biology
00:38:05.22 00:38:09.07 are likely to be very important for making progress.
00:38:09.08 00:38:16.06 Now to return to this scheme, what I talked about so far was several elemental aspects of the process
00:38:16.07 00:38:20.26 such as altering the amount of energy that has to go into breaking down the biomass,
00:38:20.27 00:38:23.27 and utilizing all of the sugars.
00:38:23.28 00:38:25.22 There are other places in the overall process where improvements are possible.
00:38:25.23 00:38:29.26 And probably the big one, or the one I would like to talk about next is
00:38:29.27 00:38:34.09 the question about whether ethanol is even a desirable end-product.
00:38:34.10 00:38:38.17 I would say that although ethanol is the big biofuel today
00:38:38.18 00:38:45.24 that is primarily a historical accident that we had a kind of brewing and alcohol industry
00:38:45.25 00:38:49.13 that was able to use sugar to make ethanol with pretty high efficiency.
00:38:49.14 00:38:58.28 But in fact at this moment in the development of the biofuels industry,
00:38:58.29 00:39:01.29 it is good to step back and say what is it that we would really like as a fuel?
00:39:02.00 00:39:04.10 Ethanol has a number of problems.
00:39:04.11 00:39:11.01 For example, if you get to ethanol in this process, it is usually about twelve percent ethanol,
00:39:11.02 00:39:16.10 and 88% water. To turn that into fuel, you have to distill the ethanol.
00:39:16.11 00:39:19.29 So of course distilling requires a lot of input of heat, and that decreases the overall efficiency.
00:39:20.00 00:39:25.12 So, from first principles, what you would like is something that is a lot more hydrophobic than ethanols,
00:39:25.13 00:39:29.16 so that, for example, it will partition out of the aqueous phase spontaneously.
00:39:29.17 00:39:34.29 That would also create improvements in the overall fermentation process,
00:39:35.00 00:39:37.12 because unlike ethanol which is toxic to the cells,
00:39:37.13 00:39:41.23 it is possible to imagine having cells produce hydrophobic compounds that
00:39:41.24 00:39:46.28 partition out of the aqueous phase, and are therefore not toxic to the culture.
00:39:46.29 00:39:53.17 And the culture could then be presumably maintained in a continuous culture for a long period of time.
00:39:53.18 00:39:58.09 And the amount of energy that goes into creating the cellular biomass of the culture would be decreased.
00:39:58.10 00:40:04.20 Additionally, ethanol is not desirable because it is miscible with water,
00:40:04.21 00:40:13.08 and therefore it corrodes pipelines or containers and indeed in the United States,
00:40:13.09 00:40:16.27 we have about 240 million cars or vehicles of various types
00:40:16.28 00:40:22.11 and only about five million of those can use more than about 10% ethanol in their fuel
00:40:22.12 00:40:25.26 because of the miscibility issues.
00:40:25.27 00:40:30.11 So if we are ever going to move towards the Secretary of Energy's goal
00:40:30.12 00:40:34.06 of having 30% of our fuels from biofuels,
00:40:34.07 00:40:40.02 if that were ethanol, if that fuel is ethanol, then we are going to have to ultimately replace most of the fleet
00:40:40.03 00:40:43.08 which would be a huge infrastructure cost.
00:40:43.09 00:40:44.12 The fleet turns over rather slowly.
00:40:44.13 00:40:46.25 I think the half life is seven or eight years.
00:40:46.26 00:40:50.06 So from first principles then, it would be desirable
00:40:50.07 00:40:52.27 to make something that is a lot more hydrophobic than ethanol.
00:40:52.28 00:40:55.28 Now nature offers many such alternatives.
00:40:55.29 00:41:05.20 For example as shown here, plants, algae and bacteria all synthesize compounds such as alkanes,
00:41:05.21 00:41:08.19 and long chain alcohols and waxes that are very hydrophobic.
00:41:08.20 00:41:14.23 And indeed the principal component of our current fuels are alkanes.
00:41:14.24 00:41:19.09 I think I have already mentioned the second point on this slide,
00:41:19.10 00:41:22.15 which is if we could produce such hydrophobic compounds,
00:41:22.16 00:41:28.22 that would alleviate the energy required for dehydration and could reduce toxicity.
00:41:28.23 00:41:32.28 So here's an example of how organisms make alkanes.
00:41:32.29 00:41:40.08 On the top is shown a typical fatty acid. All living organisms make fatty acids,
00:41:40.09 00:41:44.07 because the membrane lipids are composed of long chain fatty acids.
00:41:44.08 00:41:50.17 It is known that many organisms have a class of enzymes called de-carbonylases
00:41:50.18 00:41:55.04 that are able to remove the carboxylic acid function in a two step process
00:41:55.05 00:41:58.09 to produce an alkane as shown on the bottom.
00:41:58.10 00:42:01.15 For example, the surface of all plants is covered with alkanes
00:42:01.16 00:42:04.15 as part of the wax that prevents plants from evaporating.
00:42:04.16 00:42:08.23 Similarly many micro-organisms make such things.
00:42:08.24 00:42:15.06 However, interestingly the identification of the de-carbonylase has never been accomplished,
00:42:15.07 00:42:19.26 mostly because really, very few people have tried since the mid-1970s
00:42:19.27 00:42:23.27 when these enzymes were discovered as an activity in crude extracts.
00:42:23.28 00:42:27.13 And I think it is a perfect example of an opportunity, a scientific opportunity
00:42:27.14 00:42:32.08 that could fundamentally change the whole bio-energy spectrum
00:42:32.09 00:42:36.16 that has emerged, or re-emerged I should say, as an interesting problem.
00:42:36.17 00:42:41.11 Something that has just been sitting unexplored basically for the last 25 years.
00:42:41.12 00:42:46.24 So if I were to summarize what I tried to convey
00:42:46.25 00:42:53.08 up to this point, I would say that in order to make biofuels,
00:42:53.09 00:42:57.07 cellulosic biofuels feasible, no miracles are required.
00:42:57.08 00:43:01.09 There's about four things, four main things that need to be done.
00:43:01.10 00:43:07.26 One is it would be desirable in the long run to modify plant composition to minimize the energy required
00:43:07.27 00:43:13.09 for de-polymerization. And I tried to give you the example of well, maybe we could modify the structure of lignin
00:43:13.10 00:43:15.26 so that we could remove it under physiological conditions.
00:43:15.27 00:43:21.02 We need to identify better catalysts for breaking down the poly-saccharides.
00:43:21.03 00:43:27.14 And I would say that that's an area also that has been very poorly explored.
00:43:27.15 00:43:30.11 There has been quite a bit of work on a small number of enzymes,
00:43:30.12 00:43:37.24 for very mechanistic reasons, but we don't really know yet how much diversity exists in nature.
00:43:37.25 00:43:42.01 And so now there's an opportunity using the high throughput methodologies
00:43:42.02 00:43:47.14 to go out and explore what's possible or what nature produces and bring them back to the process.
00:43:47.15 00:43:53.13 I think we need to develop new industrial micro-organisms that can ferment all the sugars,
00:43:53.14 00:43:57.11 and also organisms that can be resistant to certain inhibitors
00:43:57.12 00:44:00.27 that arise during the degradation of biomass
00:44:00.28 00:44:06.08 and can thrive in large scale industrial reactors.
00:44:06.09 00:44:13.23 And finally, I think there is a big opportunity to develop micro-organisms that can secrete
00:44:13.24 00:44:18.28 what I am going to call second-generation fuels, such as alkanes or turpines,
00:44:18.29 00:44:21.05 or various other hydrophobic compounds
00:44:21.06 00:44:25.24 that will not require replacement of the current infrastructure.
00:44:25.25 00:44:33.13 I think the field has many questions,
00:44:33.14 00:44:39.08 although the general field of biofuels has been around for some decades,
00:44:39.09 00:44:47.20 it's been very poorly populated. There haven’t been a very large number of people working in the field.
00:44:47.21 00:44:55.15 The price of oil was too low to really encourage societal support of research in these areas.
00:44:55.16 00:45:02.25 So many questions remain. I think one question that comes up
00:45:02.26 00:45:08.20 is how challenging are the technical problems that I have alluded to.
00:45:08.21 00:45:12.02 And there is no short answer to that until the problems are really solved,
00:45:12.03 00:45:15.01 but based on my experience as a scientist,
00:45:15.02 00:45:21.03 I personally believe that we will be able to make a price-competitive
00:45:21.04 00:45:26.02 biofuel process probably within the next five years.
00:45:26.03 00:45:31.14 And I think we will be able to make biofuels actually much less expensively
00:45:31.15 00:45:36.10 than we currently can make fossil fuels,
00:45:36.11 00:45:39.22 at least from petroleoum, within twenty years.
00:45:39.23 00:45:46.04 I don't see any immense technical barriers.
00:45:46.05 00:45:51.12 That will also address what the time frame is... I think we will have plants in five years,
00:45:51.13 00:45:57.14 I think we will have big plants and quite wide-spread cellulosic biofuels within ten years.
00:45:57.15 00:46:11.02 It's frequently also asked, well, why is there a focus on biofuels as opposed to other things like conservation
00:46:11.03 00:46:17.04 or wind or photovoltaics? I want to make it clear that I am not
00:46:17.05 00:46:21.22 proposing biofuels as an alternative to any of those things.
00:46:21.23 00:46:25.02 My own experience and perspective on our energy needs
00:46:25.03 00:46:28.16 is that we need all possible carbon neutral technologies.
00:46:28.17 00:46:32.00 We need to put them on the shelf so that they are available to us.
00:46:32.01 00:46:36.18 Biofuels are of particular importance in the context of transportation fuels,
00:46:36.19 00:46:40.05 where it is very challenging for example to use electricity,
00:46:40.06 00:46:44.03 which can be generated from wind or nuclear or other sources,
00:46:44.04 00:46:47.10 as a transportation energy source.
00:46:47.11 00:46:52.05 So the remaining type of question that comes up is the degree to which
00:46:52.06 00:46:55.15 there are risks. From the technical side,
00:46:55.16 00:47:00.23 I don't see any particular risks associated with this.
00:47:00.24 00:47:02.25 I think that the kind of work that needs to be done
00:47:02.26 00:47:11.26 is typical industrial microbiology and protein engineering and enzymology.
00:47:11.27 00:47:20.08 So I see this as a kind of technology that can go forward within the existing structures
00:47:20.09 00:47:25.12 and shouldn't create any unusual social, societal concerns.
00:47:25.13 00:47:29.29 Well, I hope that gave you some sense of what's going to be required
00:47:30.00 00:47:34.14 to make biofuels a part of our energy economy.
00:47:34.15 00:47:39.28 It's a very interesting topic because it is so multi-disciplinary.
00:47:39.29 00:47:47.22 There's elements of chemistry, and genetics, and agronomy, and microbiology, and socio-economics.
00:47:47.23 00:47:53.13 I find it to be one of the most interdisciplinary kinds of
00:47:53.14 00:47:56.29 endeavor that I have experienced in my career as a scientist,
00:47:57.00 00:48:02.01 and I think it is in some ways a very interesting insight into
00:48:02.02 00:48:06.26 perhaps how going forward the new technologies of the future
00:48:06.27 00:48:09.08 are going to be very multidisciplinary.
00:48:09.09 00:48:12.10 Thank you very much. I hope that was informative.

Videos in this Talk
  • Part 1: The Argument for Biofuels
    Part 1: The Argument for Biofuels
    Audience:
    • Student
    • Researcher
    • Educators of H. School / Intro Undergrad
    • Educators of Adv. Undergrad / Grad
  • Part 2: Cellulosic Biofuels
    Part 2: Cellulosic Biofuels
    Audience:
    • Researcher
    • Educators of Adv. Undergrad / Grad
Speaker: Chris Somerville
Total Duration: 1:21:47
Recorded: May 2007
All Talks in Plant Biology

Talk Overview

The first segment of this presentation describes the rationale for using plant biomass as a source of fuels and presents information about how much energy could be obtained in this way. Examples of the kinds of plants that are likely to be used are presented along with comments on some of the issues, such as losses to disease and effects of various cropping systems on soil quality, that need additional research. In the second segment, the potential for various types of biofuels are compared and some of the technical challenges in production of cellulosic fuels are outlined.

Speaker Bio

Chris Somerville

Chris Somerville

In 2007, Chris Somerville became the Director of the Energy Biosciences Institute at the University of California, Berkeley where he is also a professor in the Department of Plant and Microbial Biology and a visiting professor at Lawrence Berkeley National Laboratory. Prior to joining EBI, Somerville was Director of the Carnegie Institution, Department of Plant… Continue Reading

Playlist: Environmental Sciences

Related Resources

Somerville, C.R (2007) Biofuels. Current Biology 17 (4), R115-119.
Breaking the Biological barriers to Cellulosic Ethanol. DOE/SC-0095 (2006).

Basic Research Needs for Solar Energy Utilization. Report of the basic Energy Sciences Workshop on Solar Energy Utilization, April 18-21 (2005).

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