Biofuels developed from plant biomass and purpose-grown crops can substantially move California toward its ambitious energy goals, a new report says, but only through the wise allocation of feedstocks and the success of energy efficiency measures throughout the state.

That's the conclusion of "California Energy Future: the Potential for Biofuels," a report of the California Council on Science and Technology (CCST) co-authored by Energy Biosciences Institute scientists Heather Youngs and Chris Somerville. The study is one of seven produced by the CCST's California's Energy Future Committee, which was tasked with understanding how the state can meet aggressive reductions in greenhouse gas (GHG) emissions required by California policy by 2050.

The biofuels paper, according to lead author Youngs, a Senior Fellow at the EBI, addressed six scenarios of varied supply and demand options. They illustrate that the degree to which biofuels may help California meet its emissions goals depends upon how future demand for fuels rises or falls and what technologies are developed. Other factors include energy crop availability, investment decisions, public acceptance, and competing demands for renewable energy resources.

"The concerns regarding large-scale use of biomass for energy in California are largely a matter of sustainable resource management," Youngs said. "Judicious use of feedstocks will be required to obviate long-term sustainability concerns and maximize efficient resource management."

The researchers concluded that next-generation biofuels can reduce greenhouse gas emissions of transportation to meet the target GHG reduction goals of the state, but deep replacement of fossil fuels through implementation of low-carbon lignocellulosic ethanol and advanced biomass-derived hydrocarbons (drop-in fuels), and reduction in demand, are required.

The challenge for California lies in landmark State Executive Order S-03-05, signed by Arnold Schwarzenegger in 2005. The target: reduce greenhouse gases (GHGs) more than 80 percent from 1990 levels by 2050. The California Legislature has also enacted legislation to encourage low-carbon technologies.

Assembly Bill 32, The Global Warming Solutions Act of 2006, put a 2020 GHG target officially on the books. It also paved the way for the Renewable Portfolio Standard that requires 33 percent renewable electricity by 2020, and for adoption of California's landmark 2009 Low Carbon Fuel Standard.

The CCST's first report in its California Energy Future series summarized the conclusions of a two-year study -- in order to reach those goals, a little bit of everything will be required.

This includes increased efficiency through reduced demand, shifts to electrification, decarbonized electricity production, and decarbonized liquid and gaseous fuels. Subsequent reports reveal the details, delving into nuclear power, transportation and building efficiency, electricity from renewable sources, and advanced technologies.

One key finding of the Committee was that low-carbon fuels are absolutely required to reach the GHG reduction goals. Even with electrification of some vehicles, liquid fuels will still be required for aviation, marine and heavy-duty transportation.

"Substantial amounts of low-carbon biofuels would be required even with optimistic efficiency, electrification, and implementation of other renewable energy sources," the authors state.

California has a policy goal of producing 75 percent of its biofuels from in-state resources. Biofuels can be produced using agricultural wastes, forest thinnings and harvest residues, municipal wastes, and purpose-grown energy crops such as perennial grasses and short rotation woody crops. According to the report, this could be difficult. The state could produce 40-120 million tons of biomass or 3 to 10 billion gallons of fuel each year, meeting up to 60 percent of the 2050 demand in the most optimistic case. Success will depend upon overcoming a number of economic, social and sustainability barriers, Youngs said.

"Biofuels could reasonably be imported from other states or countries like Brazil," she noted. "While imported biomass could supply in-state biorefineries to meet the 75 percent goal, this solution would be more costly than the import of biofuels themselves to meet the GHG reduction goals. Decisions regarding biomass use and biofuel import will greatly affect the ability of the state to meet its policy goals."

The authors expressed confidence that future technologies could be deployed to produce a new generation of low-carbon biofuels, like cellulosic ethanol and drop-in biofuels, to meet the demand by 2050. They also urged the proper choice of species and production criteria for feedstocks and fuel conversion technologies by region in the state.

This includes development of arid-tolerant feedstocks, water-minimizing conversion technologies, use of grasses that sequester soil carbon and recycle nutrients, and use of plants that can tolerate poor soils and do not compete with food or feed production. All of these issues are being studied at the EBI in Berkeley and Illinois.