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Manufacturing Biofuels

Hurricane Bill strengthened today as it bore down on Bermuda, the strongest of three tropical storms that formed this week. My wife took advantage of the cash-for-clunkers program last week to buy a Prius that gets 50 miles per gallon.  Down the road, I find that my local BP (British Petrolium) gas station has rebranded itself as “Beyond Petrolium.” What do these three events have in common?  Global warming.

For decades global warming had been a reality only to scientists, something I taught in my college classroom to alert students to a changing future.  The public was little concerned, largely adopting President Bush’s view that the claims were controversial and the fuss premature.  I credit Al Gore with jarring the American public out of its complacency.  Few could view his video An Inconvenient Truth and not be convinced that global warming is a real and present danger.

Since then, talk of global warming has come to dominate political discussion of our country’s future, particularly since the change of administrations this year.  Energy legislation is being seriously debated in congress that would place caps on carbon emissions to limit how much greenhouse gases our factories spew out.  Tax incentives are being offered to spur use of solar and wind energy. Starting in January Missouri homes will be given tax credits for installing solar panels.

One of the biggest and best-advertised pushes to fight global warming has been a partnership of government and the agricultural industry to replace the gasoline our cars burn with ethanol.  While both fuels emit the greenhouse gas CO2 (carbon dioxide) when they are burned, the CO2 emitted burning gasoline is an addition to what’s already in the atmosphere, having spent the last few million years locked away far below ground.  The CO2 emitted burning ethanol, by contrast, does not add to what’s already in the atmosphere, as that’s exactly where it was until it was made part of a plant by photosynthesis this year. 

Seems like a no-brainer, substituting ethanol for gasoline.  It has not proven an easy transition, however.  The problem is not the ethanol.  Ethanol is a good fuel, with most of the energy content of gasoline. Just mixing it with 15% gasoline (so-called E85) produces a fine car fuel. The big problem has been getting enough of it -- finding a practical source for an awful lot of ethanol.

Where are we getting our ethanol fuel?  From corn.  Corn kernels are stuffed with starch, long chains of sugar molecules joined end-to-end.  Industrially, it’s no big thing to break starch into sugars, and then ferment the sugars into alcohol.  That’s how Budweiser makes beer. The problem is with the agriculture.  To get a lot of alcohol takes a lot of corn, tying up land that otherwise would have been used producing food.  As the market for ethanol has grown, so has the price of corn, and the impact on those who eat corn in the third world has been devastating.  When pennies separate a family from starvation, there is simply no way the poor can compete with you and I for the corn. We drive our cars a little greener, and they starve. 

I don’t think anyone who has thought about global warming seriously thinks corn ethanol is the solution for the future.  Clever advertising by Big Agriculture (which produces the corn) has led many Americans to equate corn ethanol with “biofuel,” although in fact ethanol can be obtained from many other plants -- sugar from beets, for example, offers a much better opportunity. In Europe biodiesel fuel is now being made from rape, an oil-rich grass grown extensively over there.

However, beets and rape, like corn, are major commercial food crops.  We are not going to be able to divert enough of the world’s cropland to energy production, not on a scale that will really address the problem. Said flat out, the only hope that biofuels will make a significant contribution to the global warming problem is if we find a way to utilize something other than a commercial crop as a source of plentiful cheap fuel.

There are two approaches that stand out to me as particularly promising: cellulosic ethanol and algae-manufactured oils.

The first promising approach is to extract ethanol from the nonstarchy parts of plants, the stems, branches, leaves and roots.  These body parts of a plant are made almost entirely of cellulose and hemicellulose, two sugar-chain molecules that like starch can be broken into sugars for fermenting into ethanol.  And because the entire body mass of the plant is being used, there is no need for the plant to contain starch. Any old plant will do. What you want is a plant that grows very fast, preferably on marginal soils unsuited for growing crops. Hard to find such a plant?  Not at all.  Evolution has selected strongly for such weedy growth, and many candidate biomass crops are available, most notably switchgrass. 

Cellulosic ethanol, as the ethanol made from biomass is called, hasn’t taken off as an industry yet—the science of making ethanol from biomass is a little more complex and harder to scale up than making ethanol from corn kernel starch or beet sugar.  But the science is solid, and the approach has real potential.

The second promising approach – producing fuel from algae – is being pioneered by famous molecular geneticist Craig Venter.  You may recognize his name as the first scientist to sequence the genome (all the DNA) of a living organism (a bacterium called Haemophilus influenzae).  Later he became the leader of the privately-financed team that sequenced the human genome in the late 1990s.  Venter has a track record of success at difficult tasks that any scientist would envy.

So what is Craig Venter doing with algae?  At first, getting fuel from algae seems sort of similar to the biomass approach we have just described, but Venter’s approach is actually radically different, in two respects. 

First, the fuel produced by Venter from algae is not ethanol.  Of all things, it is fat! This isn’t so silly as it at first may sound.  To see why, you need to step back for a minute and think like a plant. A plant captures energy from sunlight by focusing light photons like a magnifying glass on individual electrons, goosing the electrons  to jump to a higher energy level.  In effect, the now-high-energy electron has stored the light photon’s  energy, a little atomic battery if you will. What’s important about this is that the energy goes wherever the atoms carrying the energized electrons go. In photosynthesis, they end up linking carbon atoms to hydrogen atoms. A chemist would say they form C-H chemical bonds.

Sorry for the chemistry lesson, but now you get the point: the energy in plant fuel (and in human food, for that matter) is in C-H bonds.  The richer a molecule is in these bonds, the better fuel it makes.  Gasoline is a complex mixture of “hydrocarbons,” long chains of carbon atoms each bearing C-H bonds.  Ethanol is a far shorter carbon chain, with two carbon atoms bearing C-H bonds linked to an oxygen atom. 

Fats, called triglycerides by chemists, are a little bit like each of these.  Each fat molecule has three long hydrocarbon chains like the ones found in gasoline.  The three chains are each linked to an oxygen atom like the one found in ethanol -- the oxygen serves as a leash holding the chains to a three-carbon core.  As you can imagine, fats make good fuel. In fact, if you were to cleave off the core of the fat by removing the oxygen atoms, you would be left with – gasoline.

THAT is the opportunity Venter has seen. 

Many algae utilize photosynthesis to make oil (liquid fats are called oils), which they store as a foodstuff against hard times.  Why not, Venter asked, convert that oil to hydrocarbon fuel? 

Now comes Venter’s second radical innovation.  Instead of harvesting oil-rich algae to get the oil, Venter abandons the whole agricultural approach of harvesting a crop, and instead adopts a manufacturing approach. Venter has used the genetic engineering technology at which he is a master to add the genes for a secretion pathway from another organism to the genome of an oil producing algae.  The genetically engineered single-celled algae now secrete the oil they make into the culture medium in which the algae are being raised.  In effect, the algae cells become tiny factories, squirting out oil. The oil floats to the surface of the culture vessel, where it can be easily collected.  “Bio-manufacturing,” Venter calls it.

This all sounds wildly promising, but is there any commercial reality to Venter’s dream?  Yep.  Last month, on July 14th, the oil giant EXXON MOBIL announced it was putting 300 million dollars into Venter’s SYHTHETIC GENOMICS, the San Diego firm he has formed to commercialize his venture, with another $300m if things go well. 

First on the list of things Venter will do is to genetically engineer the algae so that they snip the fat molecules from their cores, leaving pure hydrocarbons.  Then changes will be made to improve the algae’s abilities to withstand the intense illumination and heat that full-bore production will likely entail.  Other changes to be sought will increase resistance to viruses, which might otherwise devastate concentrated algae cultures.

Other than sunlight, the only raw material Venter’s algae will require is carbon dioxide.  And that is where we came in, isn’t it, with carbon dioxide in the atmosphere responsible for global warming.  Carbon dioxide can be force-fed to Venter’s algal cultures as the exhaust from industrial plants, power stations, and oil refineries!  Of course this doesn’t prevent the fossil fuel CO2 from eventually reaching the atmosphere.  When the algal oil is burned as fuel it will get there.  But it will have been made to do double duty as fuel first. 

Venter’s dream isn’t going to become reality tomorrow.  But its promise is exciting.  I certainly wish him well.  And I cannot help but be encouraged when oil companies become invested on the side of the global warming good guys. The irony is inescapable, but the trend very welcome indeed.

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