At the moment, most of the ethanol produced in the United States starts out as corn. Only the starchy part of the corn kernel is used; the leftover oils, fibers, and proteins are used as animal feed. But most biofuel experts believe that corn ethanol is a transitional technology. In the near future, greater amounts of ethanol will be derived from cellulose – the tough structural material found in a plant’s leaves, stalk, and roots.

Cellulose is the most common organic compound on earth,¹⁸ present in everything from paper pulp to hog manure. Because cellulose is fibrous, it has to be broken down into simpler molecules before it can be fermented, a requirement that has made cellulosic ethanol more difficult to produce.¹⁹ Now, thanks to new technologies like ours that generate no toxic waste and very few greenhouse gases, a growing number of companies believes it makes economic sense to produce fuel from materials that have no future on the dinner plate: wood slash, grasses, corn stover (the stalks and cobs left after processing), sawdust, garbage, and even manure.

The exciting thing about cellulosic ethanol is that the raw materials are all around us. Biomass feedstock is created every time someone prunes a tree, flushes a toilet, or mills a log. Dedicated biomass crops like switchgrass, willow, or poplar trees can be grown expressly for the purpose of providing feedstock for ethanol production. But cellulosic ethanol can also be made from materials that currently clog up landfills: agricultural and timbering leftovers, urban wood wastes, scrap paper, animal manure, sewage sludge, and industrial residue from wood pulping or food processing.

Ethanol’s critics have suggested that demand for the fuel could outstrip the agricultural land available to grow the corn to make it. That objection vanishes when cellulosic sources are factored in. The U.S. Department of Energy estimates that the nation’s forest and agricultural lands can sustainably produce 1.3 billion tons of biomass each year – biomass which could be converted into 100 billion gallons of ethanol. That’s enough to reduce our nation’s gasoline consumption by more than half.²⁰

Cellulosic ethanol has an extremely favorable net energy balance, which means that it takes very little energy to create it. Feedstocks such as switchgrass, and agricultural and industrial wastes are produced without the need for a lot of fertilizers or other fossil-fuel inputs. Switchgrass, for example, yields four units of energy for every unit of energy used to grow it, and the ratio of energy output to input for waste feedstock may be even higher.²¹

Researchers at Argonne National Laboratory studied the production process of gasoline, corn ethanol, and cellulosic ethanol, measuring everything from the petroleum used in fertilizer to the energy used in refineries. Their conclusion: from start to finish, or well to wheels, cellulosic ethanol could slash the consumption of fossil fuels – petroleum, natural gas, or coal – by 70 percent.²² Enterprising ethanol producers can build their plants close to the biomass source – whether it’s a harvested field or a city dump, eliminating the need to truck feedstock to the plant, or waste to the recycler.

Consider these facts:

• If the waste products of all American farms were converted into cellulosic ethanol, it would provide as much fuel as we currently import from Venezuela and the Persian Gulf combined.²³
• Burning leftover wheat straw in eastern Oregon and Washington after the harvest is a major cause of air pollution in those regions. Yet when used as a feedstock, wheat straw can produce 90 gallons of ethanol per dry ton.²⁴
• Burning leftover rice straw in California’s Sacramento Valley is such a serious source of air pollution that it has been banned. Now a manufacturer of cellulosic ethanol has set up shop in the area, with plans to use 120,000 tons of waste rice straw per year as feedstock.²⁵
• The nation’s largest dry-mill corn ethanol producer has already announced plans to convert one of its Iowa facilities to produce cellulosic ethanol from corn fiber, corn stover, and corn kernels. The company expects the conversion to result in 27 percent more ethanol per acre of corn while using 83 percent less energy than a conventional corn-to-ethanol plant.²⁶
• Switchgrass, a deep-rooted perennial American prairie grass, can be grown without irrigation or fertilizer on land unsuitable for food farming. We know that growing it actually prevents soil erosion and restores degraded land.²⁷ We also know that 15 percent of the North American continent is marginal for conventional agriculture. If we planted it with switchgrass, we could make enough cellulosic ethanol to replace every gallon of gasoline consumed in the United States.²⁸
• Energy crops grown to produce cellulosic ethanol yield two to three times more biomass per acre than corn. That means far less land will be needed to produce far more cellulosic ethanol. Researchers from the Rocky Mountain Institute explain it this way: “Cellulosic ethanol will typically have twice the ethanol yield of corn-based ethanol, at lower capital cost, with far better net energy yield.”²⁹
• Because plants remove carbon dioxide from the atmosphere during photosynthesis, and because new cellulosic ethanol technology uses plant materials to fuel the fermentation and distilling processes, cellulosic ethanol has the potential to be 100 percent carbon neutral – removing as much carbon dioxide from the atmosphere as it creates.³⁰