CCST report: an integral role for next-gen biofuels in meeting California GHG targets requires advanced biofuels and demand reduction
Next-generation biofuels can reduce greenhouse gas emissions of transportation to meet California’s target greenhouse gas (GHG) reduction goal, but deep replacement of fossil fuels through implementation of low-carbon lignocellulosic ethanol and advanced biomass derived hydrocarbons (drop-in biofuels) and reduction in demand is required, according to a new report from the California Council on Science and Technology (CCST).
The study, “California Energy Future: the Potential for Biofuels,” co-authored by Energy Biosciences Institute (EBI) scientists Heather Youngs and Chris Somerville, is the seventh and final report in its California’s Energy Future (CEF) project. The CEF project seeks ways the State could meet the mandated reductions of greenhouse gas (GHG) emissions to 80% below 1990 levels by 2050, exploring possible energy strategies for California through in-depth examinations of different technology scenarios.
|Key Finding of the California’s Energy Future Summary Report|
|One of the key findings in the California’s Energy Future Summary Report is that implementation of key efficiency efforts could reduce fuel demand in 2050 to roughly 2005 levels (half of the business-as-usual scenario).|
|Electrification of industry and transportation, to the extent reasonable by 2050, could further reduce demand to roughly 75% of 2005 levels for gaseous fuels and 66% for liquid fuels.|
|While most of the light-duty fleet and rail transportation could be electrified, liquid fuels would still be required for aviation, marine, and heavy duty transportation. Gaseous fuel would be required for some heavy industry and load-following in electricity generation from intermittent renewable sources such as wind and solar.|
|Thus, substantial amounts of low-carbon biofuels would be required even with optimistic efficiency, electrification, and implementation of other renewable energy sources.|
The focus of the biofuels report—which is a supplement to the earlier Summary Report, “California’s Energy Future – The View to 2050”—is an assessment of the potential for fuels produced from renewable biological resources to contribute to the energy needs of California, particularly for transportation.
In the report, Youngs and Somerville examined six scenarios involving two demand cases and three supply cases. The first analysis set was a “stress test” case, in which biofuels were used to meet a business-as-usual (BAU) demand case of 44 billion gallons of gasoline equivalent (bgge), nearly double the 2005 demand. Three supply cases were then examined to meet this demand.
The first supply case consisted of a business-as-usual fossil fuel mix, which starts with a projection of the current distribution of fossil gasoline and diesel usage, with 10% blending of corn ethanol in fossil gasoline and 20% blending of soy biodiesel in fossil diesel.
This was compared with two future next-generation biofuel scenarios requiring deployment of near and far-term technologies. These scenarios assumed no limitation in infrastructure and no limitation of biomass feedstock to supply the demanded hypothetical fuel mixtures.
The near-term biofuel scenario uses cellulosic ethanol blended at 85% with fossil gasoline (E85) to meet the gasoline demand. Similarly, conventional biodiesel from soy and waste oils is blended at 85% with fossil diesel (B85) to meet the diesel demand.
The far-term biofuel scenario uses advanced biomass-derived hydrocarbons (drop-in renewable gasoline and diesel) to replace conventional fuels with 10% blending of cellulosic ethanol and conventional soy biodiesel.
They concluded that in the business-as-usual (BAU) demand case, only deployment of the far-term advanced bio-derived hydrocarbons have the potential to meet the GHG reduction goals for liquid fuels.
Youngs and Somerville then evaluated the changes in demand of fuels that would result from implementation of efficiency measures in building and transportation and widespread electrification of light industrial activities, residential heating, light-duty vehicles, bus and rail. Demand was adjusted to account for other low-carbon technologies including efficiency and electrification.
Under the scenario conditions, the amended liquid fuels demand for all uses was reduced from 44 billion gallons in gasoline equivalents (bgge) in the business-as-usual case to 16 bgge, 14.8 bgge of which is used in transportation.
Under this modified demand case, both the near-term (cellulosic E85 and biodiesel) scenario and far term (drop-in bio-hydrocarbons) have the potential to reach emission goals with the reduced demand.
Because California has a policy goal of producing 75% of biofuels from in-state resources, the authors constructed two additional scenarios to determine the potential of in-state biomass to meet the 2050 demand cases. The first scenario assumed modest recovery (40% on average) of residual biomass from agricultural and forestry activities with no growth in municipal waste and very little production of purpose-grown biomass for energy.
The second, highly optimistic scenario assumed higher recovery of residues (66% on average). This scenario also projected growth of both dedicated herbaceous and woody biomass crops for bioenergy production. Growth of bioenergy crops was restricted to half the acreage that had been cultivated previously for either crop or timber production but which is no longer used for such purposes.
Using these projections, in-state biomass could meet 7-21% of the BAU demand and 22-61% of the amended demand under the high efficiency and electrification scenario. In other words, neither scenario was sufficient to meet the policy goal of 75% in-state production transportation fuel from in-state biomass supplies.
While import of biomass could supply in-state biorefineries to meet this goal, this solution would be more costly than import of biofuels themselves to meet the GHG reduction goals, the authors found. Biofuels could reasonably be imported from other states and/or other countries such as Brazil to meet some of the BAU demand or all of the amended demand in 2050. Decisions regarding biomass use and biofuel import will greatly affect the ability of the State to meet its policy goals, they suggested.
Previous CEF reports have focused on nuclear power, transportation energy use, electricity from renewable energy and fossil fuels with carbon capture and sequestration, and advanced technologies for achieving deep GHG reductions. The CEF project is funded by the California Energy Commission, the S.D. Bechtel Foundation and the California Air Resources Board (ARB); reports have been completed by committees of volunteers from major energy research institutions in the state.
The biofuels report, like the earlier ones in the series, notes that no matter what strategy or combination of strategies are employed, achieving California’s emissions targets by 2050 will require significant levels of research, development, invention and innovation.
With the completion of the last subject-specific report in the first CEF series, the focus is now on the California’s Energy Future Policy project, which is undertaking a similarly detailed analysis of specific policy requirements to achieve California’s goals of reduced emissions by 2050, with funding from the Cummings Family Foundation.