Instead of using electric cars, we can lower our dependence on foreign oil by con­verting plant matter into ethanol. About 10 billion gallons of ethanol were produced in the USA in 2009, a small but growing fraction of the 140 billion gallons of gaso­line consumed. Ethanol burns 22% more cleanly than gasoline because it contains more oxygen, but it contains only two-thirds the energy per gallon. Most ethanol is sold as E10, a 10% mixture of ethanol with gasoline. Most cars can run on E10 without modification. E85, which is 85% ethanol, requires modified “flex-fuel” engines, which are installed in many trucks. In Brazil, the leader in biofuels, all cars are so modified because the country is completely independent of foreign oil, having started 25 years ago to produce biofuels from sugarcane.

In the USA at the present time, ethanol is produced from corn, not the stalks but the good part, the ears that we and the cows eat. This has played havoc with the prices of corn and soybeans. The corn is ground up, fermented, and then distilled to evaporate off the alcohol. The beer industry knows this well. What is left is still good for cattle feed. The first distillation yields only 8% ethanol, so it has to be repeated many times to get to 99.5% high octane fuel. This takes energy, at present coming mainly from fossil fuels. More energy is used in planting and harvesting the corn, in making the fertilizers, and in trucking the corn and the fuel. Pipelines cannot be used for ethanol because it is soluble in water, and water in the pipes would cause them to rust. Gasoline does not have this problem. The use of fossil energy also entails GHG emission, negating the cleanliness of ethanol exhaust. There has been controversy as to whether making ethanol from corn actually provides more energy than it consumes, and whether there is any saving of GHG emissions. Early reports in the popular literature were rather negative toward ethanol.6364 Much of the pessimism came from papers by Pimentel [36], which indicated that the energy in corn ethanol is 30% less than the energy used to make and transport it. However, other data, mostly recent ones, show a net gain in energy, though much smaller for corn than for cellulosics, which we will describe shortly. Wang’s [37] life-cycle analysis shows that to produce one energy unit of corn ethanol, 0.7 energy units of fossil energy has to be used. This means that about 40% (=0.3/0.7) more energy comes out than goes in. When blended with gasoline, E85 of course has better energy savings than E10. As for GHG emissions, E85 saves 29% and E10 26%. Wang also gives a chart showing all the studies made so far on this topic. Twelve of these showed an energy gain, while nine showed an energy deficit. The breakeven is still marginal, but the saving grace is that only 15% of the fossil fuel used is in the form of oil, the scarce commodity that depends on the Middle East. The stance of the US government is that the energy balance is positive, but no firm numbers are given.65

How does Brazil do it? Because they have the climate and labor, they can grow sugar directly instead of extracting it from corn. Sugarcane yields twice as much ethanol per acre than corn. Biofuels from sugarcane give 370% more energy than is used in production.63 The stalk is 20% sugar, and the rest can be burned to generate electricity. One factory is self-supporting; it can generate enough electricity to run the whole operation. This huge plant produces 300 million liters of ethanol and 500,000 tons of sugar per year. Between the biofuel and the electricity, the plant produces eight times the energy that it uses.64 But there is a big problem: deforesta­tion. An area the size of the state of Rhode Island was razed in half of 2007 to plant sugarcane, and the acreage is to double in the next 10 years.66 Worldwide, deforesta­tion accounts for 20% of carbon emissions, which is why Brazil ranks fourth in the world on carbon emissions.66 There is more bad news. Sugarcane has to be cut by hand, and it is hard work in the heat. It is so hard that many workers die at it. To make the cutting easier, the cane is burned every year even though it does not have to be. This releases large amounts of soot and strong GHGs to pollute the air. This sours the sugar business.

The USA cannot grow so much sugarcane, but it cannot grow enough corn either. If all the present corn and soybean crops are used to produce biofuels, there would be only enough to supply 12% of the gasoline and 6% of the diesel oil that we consume.64 But why use only the sweet part of the corn? We could also use the stalks. The stalks are made of cellulose, as are many other plants. Cellulosics are our best hope for a source of biofuel. Cellulose has a rigid molecular structure that is stiff and can allow plants to grow vertically. This is how corn can grow high as an elephant’s eye. The very structure of cellulosics makes them very hard to break down into alcohol. At present, it takes 30% more energy to make the fuel than it gives back [37]. There is an intense effort to find more efficient ways to do this, including using high-speed computers to model the chemical reactions. The Obama administration in 2009 allotted $800 million to the Department of Energy’s biomass program, and $6 billion in loan guarantees to start biofuel projects begin­ning in 2011.63

Cellulosics can be found everywhere in corn stalks, wood chips and sawdust, wheat straw, paper, leaves, and specially grown crops of grasses and other fast­growing plants. The Departments of Energy and Agriculture in the USA estimate that 1.3 billion tons of cellulosics can be gathered and grown each year without affecting food crops for either humans or animals. It is possible to produce ethanol, gasoline, diesel oil, and even jet fuel from cellulosics. The amount of cellulosics available equate to 100 billion gallons of gasoline equivalent per year, about half of our needs [38]. To do this, of course, is very hard.

There are three ways to make fuel from cellulosics [38]. At an extreme tempera­ture of 700°C, steam or oxygen can turn the biomass into syngas which is carbon monoxide and oxygen. This is done under pressures of 20-79 atm in the presence of a special catalyst. Coal plants are already set up to produce syngas (see Chap. 2). But a reactor to do this with cellulosics would be so expensive that the capital cost would not be paid back for perhaps 30 years. A second method reproduces the conditions in the earth which made fossil fuels in the first place. At temperatures of 300-600°C in an oxygen-free environment, the biomass turns into a biocrude oil. This crude oil cannot be used directly because it is acidic and would ruin the engine. It would have to be converted to usable fuel. A new idea called catalytic fast pyrolysis is being investigated which would convert biomass into gasoline in a few seconds! Fast means that the biomass is heated to 500°C in one second. The mol­ecules then fall into the pores of a catalyst which turns them into gasoline. The whole process takes 2-10 seconds.

The third, more promising way to treat cellulosics is slow and less dramatic; but it could move out of the laboratory into industry. In the ammonia fiber expansion process, the fiber is softened by pressure-cooking at 100°C in a strong ammonia solution. When the pressure is released, the ammonia evaporates and is captured and recycled. The cellulose is than fermented with enzymes into sugar with 90% yield. Distillation then yields ethanol. What is left is lignin, which burns well and can be used to boil water to generate electricity. Of course, burning generates CO2, but with biomass this CO2 was taken from the air when it was growing, so there is no CO2 added to the atmosphere. What spoils this rosy picture? It’s the enzyme.

The bacteria that make the enzyme can be found in only a few places, the best of which is in the guts of termites! We know that termites eat wood. They have an enzyme in their stomachs that turns that into something digestible. The enzyme is not easy to reproduce, unlike the yeast that makes yogurt. Presently, they cost $0.25/gallon of ethanol.67 To mass-produce either the enzyme or the termites is unthinkable. People are finding mushrooms in Guam or other bugs that could make such enzymes.63

If we can get over that hurdle, we can think about switchgrass, which you have heard of. A fast-growing source of cellulose, switchgrass needs no fertilizer and little water. It grows in places not suitable for other activity. Its roots grow 8-10 feet down, stabilizing the soil and also drawing CO2 into the ground.68 It grows for 5-10 years before reseeding. It has four times the energy potential of corn. The US Department of Energy’s goal is to make cellulosic ethanol cost-competitive with gasoline by 2012. The 100 billion gallons of gasoline equivalent per year quoted above will also lower our GHG emissions by 22% relative to our 2002 emissions. Even if switchgrass is grown outside of farm land, it will still take a lot of land. To supply all the transportation fuel for the USA would take 780 billion liters of ethanol per year.69 At the rate of 4,700 L of ethanol per year per hectare, it would take 170 million hectares or 650,000 square miles. Only Alaska, more than twice the size of Texas, has that much area.

Fortunately, new ideas are coming from people thinking out of the box. James Liao [39] has found a way to make more complex alcohols which contain more energy than does ethanols and, moreover, are miscible with gasoline but not water. Such an alcohol is isobutanol. The enzymes that ferment sugar into isobutanol are more common than those in termites: they are found in E. coli. Yes, this is the same bug that causes food poisoning, but its use can be controlled, and it is surely not hard to reproduce. The problem is not entirely solved because biomass has first to be converted to sugar before the process can start. To get around this, Liao has engineered a cyanobacterium [40] that can turn CO2 and H2O into a biofuel! Plants do this all the time by photosynthesis, but the result is cellulose. A bacterium has been engineered that can photosynthesize isobutyraldehyde, which boils at a low temperature so that it can be separated from water. That chemical can then be easily converted into isobutanol. To be competitive with current production of bio­diesel from algae, the rate has to exceed 3,420 qg/L/h. The best achieved so far is 2,500, which is promising and can be improved with further research [1]. However, making diesel from algae is very slow and space consuming — only 100,000 L (26,000 gallons) per hectare per year. Two companies, LS9 and Amyris, both in California, are involved in this development.70 It remains to be seen if this process is economically feasible.

To make transportable fuel, it would seem simpler to make electricity in fission and fusion power plants and develop smaller and lighter batteries for electric cars. Government policy, however, has to take economic stimulus into account. Farmers in Iowa and Nebraska have to be kept happy. The subsidies for ethanol production in Midwest states resulted from strong lobbies. It would seem that our corn is stored not in silos but in pork barrels.