Biofuels in Perspective

Bio-Ethanol Development in the USA 49
One of the most transformative technologies for dry mill ethanol facilities may be the
arrival of ‘raw starch’ or ‘no cook’ hydrolysis. Enzyme manufacturers Novozymes and
Genencor have both introduced enzymes that can break down corn starch at or near room
temperatures rather than the 105–150 degrees Celsius typically required, greatly reducing
energy inputs. Some challenges remain in implementing this process, but a growing number
of dry mills may soon be adopting this more efficient technology. The combination of new
fractionation technologies and ‘no cook’ enzyme technology can yield approximately a
6 % increase in ethanol yield.
Even with these and other technological advances, the upper limit on sustainable ethanol
production from corn remains well below the levels required to establish bio-ethanol as a
true alternative fuel in the United States. The greenhouse gas benefits of corn starch ethanol,
while better than petroleum, are also likely to remain modest relative to the challenges of
global climate change. As a result, a growing coalition of environmentalists, rural advocates
and national security groups is instead urging policy makers to invest in ethanol production
from cellulosic biomass. The US government is listening.
3.5 Cellulosic Ethanol
January 31, 2006, began as an ordinary day in the United States ethanol industry, but by
the time the evening was over the identity of bio-ethanol in the US had changed forever.
President George W. Bush in his State of the Union address declared that ‘America is
addicted to oil’ and that to break the addiction, the United States must invest ‘in cuttingedge
methods of producing ethanol, not just from corn, but from wood chips and stalks, or
switch grass’. He set a national goal of practical and competitive cellulosic ethanol within
six years. Suddenly, ripples went out through the venture capital community and overnight
‘cellulosic’ was a household word. The race to the first commercial production of ethanol
from cellulose was on.
Scientists have long recognized that cellulosic biomass has tremendous potential to
reduce fossil fuel dependence. Agricultural and other residues essentially offer what could
be considered a ‘free’ or much cheaper source of energy. (Since this material is otherwise
unutilized, no fossil energy or other inputs are consumed for their production.) Most
dedicated energy crops under consideration also require minimal inputs, since the leading
candidate species tend to be perennials needing little or no tillage or fertilizer – though
some concerns have been raised regarding the consumption of water by fast-growing tree
varieties.
Because cellulosic biomass also contains lignin, a fibrous material with similar energy
qualities to coal, cellulosic biorefineries are expected to be energy self-sufficient, with the
production of cellulosic ethanol powered by the burning of lignin. Thus, little or no fossil
energy is needed for processing.
As a result, cellulosic ethanol is estimated to provide over 10 units of useful energy
for every unit of fossil energy input – a 7-fold improvement over current corn starch
ethanol production and more than 12 times better than gasoline. Net greenhouse gas
emissions from cellulosic ethanol are expected to be on average 85 % lower than gasoline.
Cellulosic ethanol from switchgrass, a species of perennial grass native to the American
prairie that sequesters carbon in the soil as it grows, may even provide a net greenhouse