Environmental Engineering Reference
In-Depth Information
B
iodiesel
•
An employee was killed while using an oxyacetylene torch on a storage tank
containing residual glycerin and methanol vapors in a biodiesel facility.
•
An employee was killed when his power tool ignited methanol vapors in an
impure glycerin tank in a biodiesel facility.
BIOFUELS: THE BOTTOM LINE
With near record oil prices, the future of biofuel—made from plant material (bio-
mass)—is of keen interest worldwide. Using biofuels to power industry, private
vehicles, and personal appliances offers several benefits over the use of conventional
fuels. For example, environmental benefits include the use of biomass energy to
greatly reduce greenhouse gas emissions. Burning biomass releases about the same
amount of carbon dioxide as burning fossil fuels. However, fossil fuels release car-
bon dioxide captured by photosynthesis millions of years ago—an essentially “new”
greenhouse gas. Biomass, on the other hand, releases carbon dioxide that is largely
balanced by the carbon dioxide captured in its own growth (depending on how much
energy was used to grow, harvest, and process the fuel).
Another benefit of biomass use for fuel is that it can reduce dependence on for-
eign oil because biofuels are the only renewable liquid transportation fuels available.
Moreover, biomass energy supports U.S. agricultural and forest-product industries.
The main biomass feedstocks for power are paper mill residue, lumber mill scrap,
and municipal waste. For biomass fuels, the feedstocks are corn (for ethanol) and
soybeans (for biodiesel), both surplus crops. In the near future—and with developed
technology—agricultural residues such as corn stover (the stalks, leaves, and husks
of the plant) and wheat straw will also be used. Long-term plans include growing and
using dedicated energy crops, such as fast-growing trees and grasses that can grow
sustainably on land that will not support intensive food crops.
The preceding lists many of the benefits of using biomass fuel; that is all well and
good, but the reality is that the future role of biofuels depends on profitability and new
technologies. Technological advances and efficiency gains—higher biomass yields per
acre and more gallons of biofuel per ton of biomass—could steadily reduce the eco-
nomic cost and environmental impact of biofuel production. Biofuel production will
likely be most profitable and environmentally benign in tropical areas where growing
seasons are longer, per-acre biofuel yields are higher, and fuel and other input costs are
lower. For example, Brazil uses
bagasse
, which is a byproduct from sugar production,
to power ethanol distilleries, whereas the United States uses natural gas or coal.
Biofuels will most likely be part of a portfolio of solutions to high oil prices, includ-
ing conservation and the use of other alternative fuels. The role of biofuels in global fuel
supplies is likely to remain modest because of their land intensity. In the United States,
replacing all current gasoline consumption with ethanol would require more land in
corn production than is currently used for all agricultural production. Technology will
be central to boosting the role of biofuels. If the energy of widely available, cellulose
materials could be economically harnessed around the world, biofuel yields per acre
could more than double, reducing land requirements significantly (USDA, 2012).
