Environmental Engineering Reference
In-Depth Information
co-product of the process. The characteristics of biodiesel fuels vary significantly
depending upon the production technology and feedstock used.
Biodiesel is a diesel replacement fuel that can be used in compression-ignition
engines, and it is produced from renewable, non-petroleum-based sources such as
vegetable oils (soy, mustard, castor, canola, rapeseed, and palm oils), animal fats
(poultry offal, tallow, fish oils), and used cooking oils and fat grease (from restaur-
ants and industries). The production of biodiesel from non-food feedstock is gain-
ing special interest. In the United States and European Union, algae-based biodies-
el promises very high yields per area—15 times more than palm oil, 60 times that
of rapeseed, and 200 times that of soybeans.
Biodiesel production depends on feedstock and land availability even more than
bioethanol production. Although biodiesel is considered a “renewable” fuel, one
of the materials needed for its production is methanol produced from natural gas,
which is a fossil fuel. Advanced processes include the replacement of methanol of
fossil origin by Fischer-Tropsch technology.
Biodiesel is also usually considered “sulfur-free,” which is the case unless
the biofuel is produced by catalysis with sulfuric acid. Biofuels are hygroscopic
and easily biodegradable, which may be an environmental advantage, but also a
quality-control problem, mainly when stored in hot and humid places. Overall,
biodiesel combustion produces fewer pollutants than conventional fossil fuels, ex-
cept for NO
x
.
In Indonesia and Malaysia, palm oil biodiesel has been heavily criticized as be-
ing responsible for the clearance of native rainforests, with consequent biodiversity
losses and land-use change, in addition to greenhouse gas emissions. These criti-
cisms seem to have been exaggerated because less than 10% of the palm oil pro-
duced today is used for the production of biodiesel.
The rise in the prices of agricultural products between 2007 and 2008, after several
decades of declining real prices, is often seen as a cause of famine, and it has led to
the politically laden controversy of fuel “versus” food.
Arguments have been made that the competition between land for fuel (namely
ethanol) and land for food, in both the United States and Europe, is one of the
causes of famine around the world and leads indirectly to deforestation in the
Amazon and other tropical areas. In the aggregate, grain prices have more than
doubled since January 2006, with over 60% of the rise occurring since January
