Switchgrass may have even more potential than corn as a source for ethanol.

From Grass to Gas

On the road to energy independence,
how soon will cellulosic ethanol be a factor?

By Anthony Crooks,Ag Economist
USDA Rural Development

ur nation used more than 140 billion gallons of gasoline last year and imported about 60 billion from the Middle East. The 4.3 billion gallons of fuel ethanol produced largely by our nation’s farmers was a good start toward extending the nation’s fuel supply, but really is just a baby step.

“America is addicted to oil,” President Bush stressed in his State of the Union Address, during which he outlined the Advanced Energy Initiative (AEI) to address this serious problem. “We will increase our research in better batteries for hybrid and electric cars, and in pollution-free cars that run on hydrogen. We’ll also fund additional research in cutting- edge methods of producing ethanol, not just from corn, but from wood chips and stalks, or switchgrass. Our goal is to make this new kind of ethanol practical and competitive within six years.” For more on the AEI, visit: http://www. whitehouse.gov/news/releases/2006/05/20060524-4.html.

Speaking at a Senate Foreign Relations Committee meeting in June, former Federal Reserve Chairman Alan Greenspan said: “Corn ethanol, though valuable, can play only a limited role, because its ability to displace gasoline is modest at best. But cellulosic ethanol, should it fulfill its promise, would help to wean us off our petroleum dependence.”

Advocates of cellulosic ethanol have been saying its day would arrive “within the next five years” since the mid-1990s. But this time they just may be right. They too were encouraged by President Bush’s remarks. And while everything turns on oil prices, rising oil prices encourage new technologies by making them economical — including, perhaps, cellulosic ethanol within five or six years.

Is industry heading to cellulose?
Cellulosic ethanol is fuel ethanol made from cellulose, the inedible fiber that forms the stems and branches of plants. As the main component of plant cell walls, cellulose is the most common organic compound on earth. Crop residue (corn stover, wheat straw and rice straw), wood waste, and even municipal solid waste are sources of cellulose. High-biomass dedicated energy crops — think of President Bush’s reference to switchgrass in his State of the Union Address — are also promising cellulose sources that can be produced in many regions of the United States.

Switchgrass is noteworthy for ethanol production because of its potential for high fuel yields, hardiness and ability to be grown in diverse areas. Trials show current average yields to be about five dry tons per acre. However, crop experts say that progressively applied breeding techniques could more than double that yield. Its long root system helps to make switchgrass drought-tolerant, growing well even on marginal land, and it requires little to no fertilizing. Its expected ethanol yield ranges from 60 to 140 gallons per ton; with typical yields in the 80-to- 90 gallon range.

The potential energy from cellulosic ethanol is significant. A recent study estimates that a gallon of ethanol produced from corn provides about 20,000 Btu (British thermal units) more energy than the energy that went into making it. The net gain from cellulose, however, from a crop such as switchgrass, which doesn’t require fertilizer, irrigation, or other energyintensive activities, is triple that of corn, about 60,000 Btu per gallon. Not only that, but an acre of land planted in switchgrass can produce four times the cellulosic material as can land planted to corn.

Cellulose is among the most undervalued and underused energy assets in the United States. The Natural Resources Defense Council recently reported that by 2030, cellulosic ethanol could supply half of U.S. transportation fuel needs without reducing food and animal feed production.

Moreover, the unrealized potential of industrial biotech, completely apart from ethanol, is astonishing. Once plant sugars become abundantly available, any number of substances that now contribute to our “oil addiction” may be replaced with sugar molecules. residue is available for conversion. Right now, ethanol, blended into gasoline, accounts for only about 2.5 percent of the nation’s fuel supply. The potential from forestland and agricultural land, the two largest sources for biomass, exceeds an estimated 1.3 billion dry tons per year. That’s a cellulosic ethanol replacement equivalent of about 30 percent of the demand for gasoline without affecting food production.

Ethanol in the United States is made primarily from the sugar that makes up the starch in corn. Ethanol manufacturers process the corn kernel using enzymes that break down the starch into simple sugars. Those sugars are then fed into a fermentation tank, where yeast digests them to produce ethanol. The corn stalk and leaves, actually about half of the plant material, is disposed of.

Ethanol from cellulose is more complicated because cellulose forms a more complex chain of sugar molecules (6-carbon sugar molecules, a.k.a. C6) than those from corn starch (5-carbon molecules, C5). Breaking down cellulose into fermentable sugars for ethanol production therefore, requires a “pretreatment” process to open the cellulosic structure in order for conversion to occur.

Ready for commercialization?
One of the keys to progress has been to reduce the cost of converting cellulosic materials into fermentable sugars. The Department of Energy’s National Renewable Energy Laboratory (NREL) has partnered with private biotech companies to make important advances in conversion technology. Novozymes, a biotech company based in Denmark with operations in the United States, began collaborative research with NREL in January 2001 to cut the cost of converting corn stover into sugars for the production of ethanol. Recently, the two partners announced a monumental achievement — a 30-fold reduction in the costs of the enzymes needed to produce ethanol from cellulosic sources. Now costing between 10 – 18 cents per gallon in laboratory trials, enzymes are no longer an economic barrier to the commercialization of cellulosic ethanol.

NREL has also partnered with other firms to make improvements in pre-treatment technology. But the industry is only at the earliest stages of commercialization. There are still many technical hurdles to be overcome to make cellulosic ethanol production commercially competitive. Recent spikes in oil prices and energy policy initiatives help to encourage the continuation of research and development. Developments may have come piecemeal, but at least they are now in place. The key is to integrate the pieces into an economically competitive process and commercialize it.

Iogen Corporation, headquartered in Ottawa, Canada, the only company in North America operating a stand-alone, demonstration-scale, 1-million-gallon-per-year (1 MMGY) plant, is planning its first full-scale facility to produce ethanol from cellulosic biomass sources. Drawing on its partnership with Novozymes, Iogen has formulated an enzymatic “cocktail” that can break down wheat straw into sugars that can be transformed into ethanol.

EcoEthanol™ is the patented name of Iogen’s cellulose ethanol process which uses enzymatic hydrolysis to convert the cellulose into sugars.

Executive Vice President Jeff Passmore said the effort has been a painstaking exercise in going back and forth between developing the enzymes and scaling up the process to industrial levels. But with support from its partners — Royal Dutch Shell, Volkswagen AG, the Canadian government and a recent commitment of $30 million from Goldman Sachs (representing a combined investment of more than $130 million) — Iogen hopes to build the world’s first commercialscale cellulosic ethanol plant.

The company is considering sites for the facility in Idaho or in Canada, and has met with Idaho farmers to ensure they can contract enough wheat and barley straw to make that location feasible. In Idaho, 320 farmers stand ready to supply the 500,000 tons of straw for the proposed plant. (See Rural Cooperatives, Jan/Feb ‘06.)

Iogen officials say the proposed plant could produce between 40 million and 50 million gallons of cellulosebased ethanol annually and would add a considerable revenue stream to the local area for the straw feedstock required. Although the plant’s size is relatively modest by today’s standards of 100 – 200 MMGY, its price tag certainly isn’t. Because cellulosic ethanol requires not one but three processing facilities — an ethanol distillery, a pretreatment facility and a power generation plant, Iogen’s commercial-scale enterprise is expected to cost from $350 to $400 million, or roughly six times the cost of a corn (dry mill) ethanol plant of the same scale.

To finance such a formidable undertaking may require a shared risk/investment arrangement among Iogen, its present partners, and the U.S. federal government (DOE and USDA). A federal grant of as much as $80 million and a guaranteed loan to hedge against the risks associated with unproven technologies were provided specifically for cellulosic ethanol plant development in the Energy Policy Act of 2005.

But, despite its substantial upfront costs, the plant’s day-to-day operating costs are expected to be about the same as, or even a bit less, than an equivalent corn plant. Furthermore, a cellulosic plant has a number of alternative coproducts and potential revenue streams that would otherwise be unavailable to a corn dry mill. In addition to ethanol and alcohol, fertilizers, acids, ultrahigh- quality sugars, and other products may also be produced or sold to help recover the higher capital outlay. The plant will have its own power generator fueled by a waste material of the pretreatment processor, called lignin, to offset its energy costs.

Technological revolution
or evolution?
Cellulosic ethanol production may one day dominate the renewable fuels industry. A recent study called for CE to completely replace U.S. oil imports (around 50 billion gallons) by the year 2050. Until that day, emerging CE facilities will compete alongside corn dry mill plants.

But what if instead of a dichotomous path of development, CE on one side and grain-based ethanol on the other, the industry developed along an integrated path where grain-based plants included technologies to process the whole corn plant?

Three of the larger ethanol companies are betting that the future of cellulosic ethanol will follow this evolutionary path instead of a wholesale revolution. Abengoa Bioenergy, Broin and Co. and DuPont are developing processes that will help to integrate cellulose conversion technologies into their existing dry mill ethanol plants. Each company is involved in a formalized Research and Development Agreement with U.S. DOE to push its respective technologies along.

Abengoa Bioenergy
Abengoa received a $10 million DOE grant to develop a next-generation dry mill corn ethanol plant. The $17.7 million project is titled “Advanced Biorefining of Distillers’ Grain and Corn Stover Blends: Pre- Commercialization of a Biomass- Derived Process Technology.” The project involves a partnership of Abengoa-owned High Plains Ethanol in York, Neb., Novozymes North America Inc., VTT-Finland and the NREL. The project goal is to develop and demonstrate an integrated biorefining process which includes the fermentation of both pentose (C5) and glucose sugars (C6). Such an ambitious undertaking involves two significant steps: The twin York facilities are expected to mimic what Abengoa is demonstrating with its enzymatic hydrolysis technology on a larger scale in Spain. In a partnership with Ebro Puleva and the European Union 5th Framework Programme, Abengoa’s 2 MMGY biomass commercial demonstration facility uses wheat straw and is co-located with a starch plant in Salamanca with the two sharing utilities and support systems. However, just as with the Iogen wheat straw demonstration facility in Canada, the plant in Spain will not ferment the pentose (C5) sugars and glucose (C6) sugars simultaneously. Only glucose (C6) from the cellulose hydrolysis will be fermented into alcohol. The pentose-laden residue will be mixed with animal feed and incorporated into other studies.

Broin’s efforts
Before this next-generation plant will be capable of producing ethanol from the entire corn plant, it must first produce ethanol from the whole kernel — both starch (the only portion currently utilized for ethanol) and the residual fiber (what is now the distillers grains). Converting the residual fiber requires processing with cellulose enzymes. The application of cellulosic technology could dramatically increase the ethanol yield of the nation’s more than 100 existing dry-mill ethanol facilities.

NREL collaborates with Broin and Associates Inc. of Sioux Falls, S.D., on a $5.4 million project entitled “A Second Generation Dry Mill Biorefinery,” to separate bran, germ and endosperm from corn kernels prior to making ethanol from the remaining starch. Trademarked as BFrac®, the technology is expected to be merged with cellulosic technologies.

Broin’s progress on this frontier has been encumbered by the same difficulties shared by Iogen and Abengoa. The conversion of the BFrac fiber fraction into ethanol has been hindered by the absence of an organism that will ferment C5 and C6 sugars simultaneously. The optimum pretreatment process will require the development (discovery) of an elusive multitasking ethanologen (fermentationinducing agent).

Broin has already experienced some success in integrating other technologies into its plants. Broin’s Project X (BPX), the company’s own raw starch hydrolysis technology, has been successfully implemented on a commercial scale in 10 plants and the BFrac technology has been integrated into two. Given that BPX and BFrac are complementary processes, Broin’s experience in technological integration could very well give it an edge in the integration of cellulosic ethanol.

DuPont takes a different approach
The $18.2 million equity investment DuPont project is titled: “Integrated Corn-Based Biorefinery.” With help from Diversa, NREL, Michigan State University and Deere & Co., DuPont has taken a decidedly different approach in its cellulosic research-developmentcommercialization. DuPont expects to lead the way in developing a bio-refinery concept that converts both starch and lignocellulose to fermentable sugars for production of value-added chemicals and fuel ethanol.

DuPont has bio-engineered an organism to produce enzymes that break C6 sugars into a compound called Bio-PDO (a bio polymer, 1,3 propanediol), which is used to produce its Sorona-brand apparel fabric. Sorona was once made from a petroleum-based polymer. Bio-PDO is now expected to be the first of many future purified sugar products.

Exploiting the idea that “the cell is a factory” unleashes a seemingly boundless array of possibilities. This is essentially what happens in the fermentation stage of ethanol production. But just because the sugar is the feedstock doesn’t necessarily mean that ethanol is the final product. DuPont uses both processes to make its cellulosic ethanol plant work — polymers, where the value lies, and ethanol as the plant’s ‘cash cow’. And just as with Iogen and Abengoa, DuPont will also build a power plant to burn the high-energy lignin generated in the pretreatment facility.

Don’t ignore the synergies
The integration of cellulose process technology within existing dry mill (grain based) ethanol facilities seems to be the most practical approach to commercialization. It just makes sense to make use of the whole corn plant and get all the sugar from stalk and all, not just the starch.

The primary differences between the dry mill fuel ethanol processing system and the cellulosic processes are the required pretreatment (hydrolysis). An ideal integrated facility would integrate the three key unit operations: hydrolysis (pretreatment), fermentation and distillation and share utilities and support systems, wherever possible. The glucose from starch and biomass processes would, of course, require bigger fermentation tanks. And a separate process would be required to use/preserve the recombinant organism necessary to ferment the pentose.

Perhaps the most practical approach at this moment would be to follow Broin’s lead in recovering the corn fiber through the waste stream and produce ethanol from the lignocellulosic material. Processing the corn-fiber stream into ethanol will become increasingly attractive as excess supply continues to put downward pressure on distillers grain prices. Corn-fiber streams are typically comprised of 20 percent starch, 20 percent cellulose, and 25–30 percent hemi-cellulose — and priced below distillers grains.

Editor’s note: For article references, email anthony.crooks@wdc.usda.gov.



September/October Table of Contents