Page 279 - Synthetic Fuels Handbook

CHAPTER 9

FUELS FROM CROPS

Burning coal, oil, and gas inevitably produces carbon dioxide, a key greenhouse gas, as
well as other pollutants, including acid-rain-related gases. By contrast, growing and burn-
ing energy crops is greenhouse gas neutral, as long as the regrowth rate balances the use
rate, so that as much carbon dioxide is absorbed as is produced by combustion.
Crops have essentially many functions and benefit particularly for the human animal!
Their products are not only a primary source of human food and animal feed, but also as
source of timber, fiber, and biomass energy (BioCap Canada, 2004). In addition, crops have
also an essential function to maintain ecological systems and natural environment.
Grain crops include corn, wheat, rice, barley, and other cereals. The seeds of these
plants are typified by their high starch content that can be hydrolyzed to fermentable sugars
for ethanol production. The sugar crops, including sugar cane, beet, and sweet sorghum, are
preferable to the starch crops to the extent that sucrose is more readily hydrolyzed to ferment-
able sugars. However, sugar cane production is restricted to warm climates, and requires both
high-quality land and irrigation. Sweet sorghum has considerable advantages over sugar cane
as an energy crop. It can grow in a variety of soils and climatic conditions and its production
costs have been estimated to be just over half those for sugar cane.
Most of crop production is used as foods and the concern is that biofuels can consume
these crops. However, more crops are being cultivated for nonfood use such as pharma-
ceutical and nutritional products, chemical derivative products such as adhesives, paints,
polymers, plastics, and industrial oils in forms of biodiesel, ethanol, two-cycle oils, trans-
mission fluids, and lubricants.
Many efforts have been carried out to grow crops for food production in order to
strengthen food security, and to alleviate the hunger and poverty particularly in developing
countries. However, attention should also be directed toward cultivation of crops for nonfood
use. Since, in some cases, cultivating for nonfood products may provide a higher value
added product, a higher profit, and a higher income, that is, an increase in farm income.
The hunger and poverty problems do not essentially rely on the incapability of individual
to produce foods by themselves, but depend on capability of individual to access foods by
their income.
Energy crops are plants grown specifically for use as a fuel. Although growing crops
for fuel dates from medieval times, in their modern form energy crops are the most recent
and innovative renewable energy option. Energy crops are important as a renewable energy
technology because their use will produce a variety of economical, environmental, and
energy benefits.
Wood is the oldest fuel known to man. Burning wood rather than fossil fuels can reduce
the carbon dioxide emissions responsible for global climate changes. Wood fuel is carbon
dioxide (CO ) neutral. It gives off only as much CO when burnt as it stores during its
2 2
lifetime. In addition, wood fuel has very low levels of sulfur, a chemical that contributes
to acid rain.
Biomass like wood can be used to produce electricity by direct combustion or gasifica-
tion. It includes short rotation coppice and forestry waste. Biomass has some attractions as a

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