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Plethora of crops holds potential for Western biofuels production boom

Assemble three University of California (UC) energy and crop experts knowledgeable about biofuels. The result is a standing-room-only crowd at World Ag Expo in Tulare, Calif., interested in crops that can add the word ‘energy’ to their farm production portfolio.

The Energy Independence and Security Act of 2007 signed into law last December by President Bush will increase the supply of alternative fuels to at least 36 billion gallons by 2022, nearly a five-fold increase over current biofuels production.

While corn will remain a solid crop for ethanol production, eyes are sharpening on more feedstocks for ethanol like woody plant material (cellulose), grasses, and crop residues.

There is plenty of agricultural biomass in California. According to Dan Putnam, UC Extension agronomist, there are two million acres of different irrigated forage crops in the state, including about a million acres of alfalfa, 450,000 acres of corn silage, 500,000 acres of miscellaneous hays, and other forages including irrigated pastures.

“That’s why I am interested in the cellulosic business. It will either complement or compete with alfalfa and other forage crops we produce,” said Putnam at the biofuels workshop at World Ag Expo. “As far as candidates for cellulosic biofuels, my suggestion is don’t start with the answer — keep asking the questions. What is the best energy crop for the region?”

Energy crops fall into four areas: starchy grains, sugar crops, oil seed crops, and cellulosic crops primarily from stovers, corn, other grains, waste materials, and woody forest products — plus dedicated cellulosic crops like switchgrass and sudangrass, Putnam said.

He added that each has its positives and negatives.

“We have to look at different crop features like high yields, conversion quality, energy balance, water use efficiency, nitrogen requirements, the impact on food production, adaptation, utilization of waste materials on marginal lands, resistance to pests and diseases, and multiple use scenarios.”

Other issues are ecosystem related like sequestration and nitrate absorption. “Are we solving a problem with agriculture or creating one?” Putnam asked. “That is the fundamental question.”

Putnam called the federal government’s biofuels goal “very ambitious.” Expectations are for modest growth in ethanol from grain and incredible 80 percent growth through cellulosic fermentation.

Forestry and residues would make up a large part of this, with perennial crops playing a role in some parts of the country and the world. A critical criterion for cellulosic production is high increases in yields, Putnam said.

Dedicated perennials have many advantages for biofuels in terms of sustainable issues in crop production, Putnam said. In addition to high yields, crop growth requirements should include full-season growth, reduced runoff, lower nutrient losses over all, reduced soil erosion, less tillage-related dust, and a deep root system to improve soil quality and carbon sequestration.

Perennials can even play a role in mitigating groundwater contamination, Putnam noted.

“The more important cellulosic crops for California include switchgrass, elephantgrass, miscanthus, rhodesgrass, bermudagrass, tall fescue grass, tall wheat grass, and alfalfa.

“Factors to consider in cellulosic crops for biofuels include processing costs, potential impediments, yield potential, production, pests, environmental impacts, processing, transportation, fuel prices, and public policy,” Putnam said.


The U.S. Department of Energy believes switchgrass is the most promising of the cellulosic-type biofuels. Yet the choice is likely to be location specific.

“Switchgrass is native to North America, and estimated yields vary from 500 to 1,000 gallons (of ethanol) per acre. Several cellulosic conversion production plants are in the planning stages in the U.S.”

Putnam was involved in four California switchgrass trials in 2007 located from the Tule Lake, Calif. area south to El Centro. Planted in the summer, the warm-season grass generated good yields, and depending on varieties, yields ranged from 3-5 tons per acre from Tule Lake to Davis, Calif. Yields to the south were lower.

“Switchgrass has its benefits — it’s a perennial crop with good water use efficiency,” Putnam said. “Drawbacks include the lack of breeding history compared to crops like corn, a year to establish the field, the need for nitrogen fertilizers, and the current lack of a switchgrass infrastructure.”

Miscanthus, others

Miscanthus is another potential cellulosic crop. Tests in Kansas have generated higher yields than switchgrass. Putnam is planning miscanthus trials in California this year.

Research conducted on elephantgrass by California State University, Fresno showed high yields. Like miscanthus, it takes a year to establish elephantgrass. Other cellulosic candidates are commonly known forages including bermudagrass and rhodesgrass — plus cool season perennials like fescues, orchard grass, tall wheat grass, and alfalfa.

Alfalfa as a biofuel

A concept exists that alfalfa could have a high-value leaf co-product for biofuels development, Putnam said. The University of Wisconsin and the USDA forage center at Madison, Wis. are testing machinery that separates alfalfa leaves and stems in the field to create a high value forage stream and a low value cellulosic stemmy fraction. Other alfalfa co-products could include animal feed, lutein and industrial proteins.

Other alfalfa strong points include existing seed and breeding technology and lower input costs.


The California Biomass Collaborative (CBC) is a UC Davis-administered organization that collaborates with government, industry, environmental, and educational groups. The CBC’s purpose is to promote sustainable California biomass management and the development of renewable energy, biofuels, and related products.

Bryan Jenkins and Stephen Kaffka, CBC co-directors, shared their insight at the World Ag Expo forum. Jenkins defined sustainability as making developments sustainable to meet the needs of current and future generations. “It’s not possible to make bioenergy — commercial useful energy forms from biomass without having an environmental impact,” Jenkins said. “We will have an environmental impact. The question in a sustainable system is whether we can continue to mitigate that impact.”

The CBC is charged with developing sustainability standards for California — standards that would impact growers of biomass products. The underlying questions are whether the standards should be exclusionary, should certain biomass or processes be weeded out, or be based on whatever a grower wants to produce as long as certain environmental and social standards are achieved, Jenkins said.

“On sustainability — if you’re a grower then you are a resource manager,” Jenkins said. “If you can produce biomass in a sustainable way in the future, there will probably be people knocking at your door to buy biomass to meet the 36 billion gallon target for biofuels.”

As a CBC co-director, Kaffka also serves as a UC Davis Extension agronomist. He posed questions on whether California farmers should produce crops and related residue for biofuels, and if so, what, when, where, and how much? “There are no firm answers,” Kaffka said. “We are in the process of trying to re-imagine and then reinvent one of the most fundamental parts of our economy — our energy system.”

Corn will be a survivor in biofuels production because it’s grown efficiently, Kaffka said. Transportation systems allow the convenient movement of large amounts of corn across the country, plus corn is a convenient commodity for manufacturers. The downside of corn ethanol, Kaffka noted, is its lack of energy efficiency domestically with a 30 percent net return energy for the energy investment required to make the product.

Kaffka believes the most likely biofuels crops in the short term in California are corn and sorghum, oilseeds (safflower, canola, and soybeans), possibly wheat and small grains, and possibly sugar crops.”

At least three groups are looking at sugarcane production for ethanol in California’s Imperial County which has the highest sugar yields in the world, Kaffka said.

In the longer run, cellulosic sources could include residues like straw and stover.

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