Department of Energy Biofuel Roadmap Barriers

This is a partial summary of biofuel barriers from Department of Energy. Unless otherwise footnoted, the problems with biomass fuel production are from the Multi Year Program Plan DOE Biomass Plan or Roadmap for Agriculture Biomass Feedstock Supply in the United States. (DOE Biomass Plan, DOE Feedstock Roadmap).

Resource and Sustainability Barriers
1) Biomass feedstock will ultimately be limited by finite amounts of land and water
2) Biomass production may not be sustainable because of impacts on soil compaction, erosion, carbon, and nutrition.
3) Nor is it clear that perennial energy crops are sustainable, since not enough is known about their water and fertilizer needs, harvesting impacts on the soil, etc.
4) Farmers are concerned about the long-term effects on soil, crop productivity, and the return on investment when collecting residues.
5) The effects of biomass feedstock production on water flows and water quality are unknown
6) The risks of impact on biodiversity and public lands haven’t been assessed.

Economic Barriers (or Investors Aren’t Stupid)
1) Biomass can’t compete economically with fossil fuels in transportation, chemicals, or electrical generation.
2) There aren’t any credible data on price, location, quality and quantity of biomass.
3) Genetically-modified energy crops worry investors because they may create risks to native populations of related species and affect the value of the grain.
4) Biomass is inherently more expensive than fossil fuel refineries because
a) Biomass is of such low density that it can’t be transported over large distances economically. Yet analysis has shown that biorefineries need to be large to be economically attractive – it will be difficult to find enough biomass close to the refinery to be delivered economically.
b) Biomass feedstock amounts are unpredictable since unknown quantities will be lost to extreme weather, sold to non-biofuel businesses, rot or combust in storage, or by used by farmers to improve their soil.
c) Ethanol can’t be delivered in pipelines due to likely water contamination. Delivery by truck, barge, and rail is more expensive. Ethanol is a hazardous commodity which adds to its transportation cost and handling.
d) Biomass varies so widely in physical and chemical composition, size, shape, moisture levels, and density that it’s difficult and expensive to supply, store, and process.
e) The capital and operating costs are high to bale, stack, palletize, and transport residues
f) Biomass is more geographically dispersed, and in much more ecologically sensitive areas than fossil resources.
g) The synthesis gas produced has potentially higher levels of tars and particulates than fossil fuels.
h) Biomass plants can’t benefit from the same large-scale cost savings of oil refineries because biomass is too dispersed and of low density.
5) Consumers won’t buy ethanol because it costs more than gasoline and contains 34% less energy per gallon. Consumer reports wrote they got the lowest fuel mileage in recent years from ethanol due to its low energy content compared to gasoline, effectively making ethanol $3.99 per gallon. Worse yet, automakers are getting fuel-economy credits for every E85 burning vehicle they sell, which lowers the overall mileage of auto fleets, which increases the amount of oil used and lessens energy independence. (Consumer Reports)

Equipment and Storage Barriers
1) There are no harvesting machines to harvest the wide range of residue from different crops, or to selectively harvest components of corn stover.
2) Current biomass harvesting and collection methods can’t handle the many millions of tons of biomass that need to be collected.
3) How to store huge amounts of dry biomass hasn’t been figured out.
4) No one knows how to store and handle vast quantities of different kinds of wet biomass. You can lose it all since it’s prone to spoiling, rotting, and spontaneous combustion

Preprocessing Barriers
1) We don’t even know what the optimum properties of biomass to produce biofuels are, let alone have instruments to measure these unknown qualities.
2) Incoming biomass has impurities that have to be gotten out before grinding, compacting, and blending, or you may damage equipment and foul chemical and biological processes downstream.
3) Harvest season for crops can be so short that it will be difficult to find the time to harvest cellulosic biomass and pre-process and store a year of feedstock stably.
4) Cellulosic biomass needs to be pretreated so that it’s easier for enzymes to break down. Biomass has evolved for hundreds of millions of years to avoid chemical and biological degradation. How to overcome this reluctance isn’t well enough understood yet to design efficient and cost-effective pre-treatments.
5) Pretreatment reactors are made of expensive materials to resist acid and alkalis at high temperatures for long periods. Cheaper reactors or low acid/alkali biomass is needed.
6) To create value added products, ways to biologically, chemically, and mechanically split components off (fractionate) need to be figured out.
7) Corn mash needs to be thoroughly sterilized before microorganisms are added, or a bad batch may ensue. Bad batches pollute waterways if improperly disposed of. (Patzek Dec 2006).

Cellulosic Ethanol Showstoppers
1) The enzymes used in cellulosic biomass production are too expensive.
2) An enzyme that breaks down cellulose must be found that isn’t disabled by high heat or ethanol and other end-products, and other low cost enzymes for specific tasks in other processes are needed.
3) If these enzymes are found, then cheap methods to remove the impurities generated are needed. Impurities like acids, phenols, alkalis, and salts inhibit fermentation and can poison chemical catalysts.
4) Catalysts for hydrogenation, hydrgenolysis, dehydration, upgrading pyrolysis oils, and oxidation steps are essential to succeeding in producing chemicals, materials, and transportation fuels. These catalysts must be cheap, long-lasting, work well in fouled environments, and be 90% selective.
5) Ethanol production needs major improvements in finding robust organisms that utilize all sugars efficiently in impure environments.
6) Key to making the process economic are cheap, efficient fermentation organisms that can produce chemicals and materials. Wald writes that the bacteria scientists are trying to tame come from the guts of termites, and they’re much harder to domesticate than yeast was. Nor have we yet convinced “them to multiply inside the unfamiliar confines of a 2,000-gallon stainless-steel tank” or “control their activity in the industrial-scale quantities needed” (Wald 2007).
7) Efficient aerobic fermentation organisms to lower capital fermentation costs.
8) Fermentation organisms that can make 95% pure fermentation products.
9) Cheap ways of removing impurities generated in fermentation and other steps are essential since the costs now are far too high.