Environmental Engineering Reference
In-Depth Information
some believe that using B20 lowers a vehicle's fuel economy. It is generally hypothesized that
vehicles running on B20 achieve 2.2% fewer miles per gallon of fuel (Radich 2004).
In contrast, research now indicates that the difference in fuel economy is insignificant during
actual road tests. If used under the guidelines of such authoritative bodies as American Society of
Testing and Materials (ASTM), B20 might actually enhance the performance of the vehicle. Since
2005, The National Renewable Energy Laboratory in Colorado has been working with Regional
Transport District of Denver to test the performance of B20 as compared to conventional diesel.
Initial research on buses indicates that after one year of observation and more than 150,000 mi,
there seemed to be neither significant difference in the average fuel economy nor any disparity
in the maintenance costs (Proc et al. 2005). Furthermore, the laboratory test, conducted at a 99%
confidence level, indicated that greenhouse gas emissions from B20 were lower than the conventional
diesel bus. Similarly, the St. Louis Metro Biodiesel Transit Bus Evaluation Project helped shatter
the myths surrounding the performance of B20. The study involved a comparison between eight
transit buses running on B20 and seven using conventional diesel. At the end of a 12-month period,
the fuel economy of the diesel buses with a total mileage of 325,407 was calculated to be 3.58 mpg.
The numbers were just slightly higher than the buses operating on B20, which after approximately
634,268 cumulative kilometers reported 5.66 km/gal. In fact, the MBRC (miles between road calls)
were better for B20 than their counterparts predicting a better performance of engines in buses
using B20 (Barnitt et al. 2008). Likewise, the difference between total maintenance costs for both
groups of buses was insignificant. Assuming labor costs at U.S.$50/h, the cost for B20 group of
vehicles were only $0.0012/mi higher than that of the pure petrodiesel-powered fleet.
The Denver study also revealed minor drawbacks to the use of B20. It provided evidence that
using B20 or any kind of vegetable oil blend will necessitate more frequent fuel injector and
fuel filter replacement in the vehicles. For the study, filter replacements were done regularly to
avoid plugging and to keep the engine running smoothly under subzero temperatures. Without
this precaution, the failure of fuel injectors in B20 group occurred within the expected mileage
range. The frequent filter replacement can be costly, particularly at a point when no long-term
data exist.
Biodiesel is commonly prepared by mixing vegetable oil and methanol or ethanol in the
presence of sodium hydroxide, a process called transesterification (www.biodiesel.org/pdf_files/
fuelfactsheets/prod_quality.pdf). One of the primary reasons for the limited use of biodiesel is its
production cost. Using soybean oil to produce biodiesel is currently the easiest of all methods but
according to U.S. Department of Agriculture statistics, the cost of producing a gallon of soybean
oil biodiesel will increase from U.S.$2.4 in 2004 to almost $2.8 in 2013, which is approximately
four times more expensive than producing a gallon of petroleum. Instead of soybean oil, the use of
yellow grease to produce biodiesel is more economical. Yellow grease (waste oil from restaurants)
is currently half the cost of soybean oil
,
but the U.S. Energy Information Administration predicts
that yellow grease will only be produced in limited amounts (Pearl 2001).
The total demand for diesel fuel in the United States and Europe amounts to 490 million t whereas
the capacity to produce biodiesel totaled 16 million t, with an average annual growth rate of 40%
from 2002 to 2006 (http://www.martinot.info/RE2007_Global_Status_Report.pdf). Even with high
production costs associated with producing biodiesel, the demand continues to rise, accompanied
by growing interest in producing biodiesel around the world. Such interest can be attributed to
federal tax credits, public awareness of greenhouse gas emissions, pollution control requirements,
government subsidies, and an increase in the production of diesel engines. In Europe, Germany is
the largest consumer of biodiesel with a total consumption reaching 34,395 GWh (gigawatt hours)
followed by France at 13,506 GWh (http://www.biofuelpowerandlight.com). Because of active
Government and Public contributions, the price of biodiesel at fuel pumps around the world has
already decreased in comparison to conventional diesel, but its utilization as a replacement to diesel
is still hampered by lack of availability, required engine modifications, frequent maintenance of
selected engine parts, and a scarcity of conclusive literature on its long-term effects.
