Biofuels in Perspective

44 Biofuels
Despite these concerns, a growing list of corn ethanol facilities is also emerging outside
the traditional Midwest corn belt. California’s central valley, which is another strong cornproducing
area, now features several biorefineries to feed California’s voracious appetite
for fuel. Texas, a state usually synonymous with petroleum, is also experiencing an ethanol
boom. Northwest Texas has only a modest corn harvest, but biorefinery developers have
been lured by the abundant supply of renewable power available from the region’s highdensity
cattle operations – cow manure is an emerging alternative to natural gas and coal
as a climate-friendly non-fossil source of heat and power for ethanol production.
Other facilities, such as those under construction along the Columbia River separating
Washington State and Oregon, and two planned facilities along the shores of the Great
Lakes in New York State, have been sited to take advantage of existing transportation
infrastructure. Transportation – both of feedstocks and finished product – is a considerable
component of the cost of ethanol production. The ability to ship by barge or rail is
increasingly important as the cost of gasoline in the US continues to rise.
While corn is likely to remain the dominant ethanol feedstock for the duration of this
decade, high fossil energy costs are now converging with breakthroughs in biotechnology
and supportive government policy to drive a new generation of ethanol production. Cellulosic
ethanol, produced from lignocellulosic biomass found in agricultural residues such as
corn stalks or wheat straw, or in dedicated energy crops such as switchgrass or hybrid tree varieties,
has tremendous potential to greatly expand ethanol production in the United States.
A comprehensive analysis by the US Department of Energy (DOE) and the US Department
of Agriculture (USDA) 12 found that, through collection of agricultural, municipal
and forestry residues and a shift towards greater use of dedicated energy crops, more than
1.3 billion dry tons of biomass could be available on an annually sustainable basis for
biofuels production by 2030. This volume of biomass would be enough to supply over
half of current US gasoline demand of 145 billion gallons annually, even at current earlystage
ethanol yields for cellulosic biomass. 13 Nearly one billion dry tons of this could be
produced by American farmers.
By far the largest near-term source of available cellulosic biomass is corn stover – the
stalks and leaves that remain on the field after corn kernels are harvested (see Figure 3.3). A
fraction of this stover must remain on the fields to maintain soil quality and prevent erosion,
but an estimated 75 million to 200 million dry tons of excess corn stover could be sustainably
collected each year in the United States, enough to triple current ethanol production. 14 Corn
stover grows at a very high density – yields can exceed 5 dry tons per acre, 3–5 times greater
than cereal straw for example – making it an attractive source of biomass. However, corn
stover also presents several challenges for collection and processing.
Unlike wheat straw, which already has an established harvesting and collection infrastructure,
very little corn stover is currently collected. Potentially costly new harvesting and
baling equipment will likely be needed, which could hinder farmer participation initially.
Corn stover also contains as much as 50 % moisture and must remain in the field to dry
before collection. Research is underway to address these concerns.
In the meantime, despite its lower yields, the presence of an existing collection infrastructure
is likely to mean that cereal straw, primarily from wheat, will be one of the
first cellulosic biomass crops to be collected for biofuels production. A variety of waste resources,
including wood and pulp mill waste and municipal solid waste also offer promising
sources of cellulosic biomass.