Page 148 - Biofuels Refining and Performance

Raw Materials to Produce Low-Cost Biodiesel 131

a direct-injection diesel engine. Results indicated that the biodiesel burned
more efficiently with less specific fuel consumption. Furthermore,
50% of the blends produced less CO and fewer unburned hydrocarbons
than diesel [155]. Also, Mittelbach and Junek stated that it improves
exhaust gas emissions, as compared to esters made from fresh oil [156].
However, despite the exhaust emission reduction, there are some dis-
emission related to the process and raw
crepancies in terms of NO x
material [1, 105, 157]. In general terms, most studies show a slight
decrease in brake power output, besides an increase in specific fuel
consumption [158, 159]. To solve this problem, Kegl and Hribernik
have proposed to modify injection characteristics at different fuel
temperatures [160].
Several authors have worked on related topics. Kato et al. have used
ozone treatment to reduce the flash point of biodiesel from fish waste
oil, resulting in easy combustibility [161]. The immiscibility of canola oil
in methanol provides a mass-transfer challenge in the early stages of
transesterification. To exploit this situation, Dubé et al. developed a
two-phase membrane reactor. The reactor was particularly useful in
removing unreacted oil [162].

4.5 Animal Fats
Bovine spongiform encephalopathy (BSE), commonly known as mad
cow disease, is a fatal neurodegenerative disease of cattle. BSE has
attracted wide attention because it can be transmitted to humans.
Pathogenic prions are responsible for transmissible spongiform
encephalopathies (TSE), and especially for the occurrence of a new
variant of Creutzfeldt-Jakob disease (nvCJD), a human brain-wasting
disease. Due to this problem, the specified risk material is burned under
high temperatures to avoid any hazards for humans and animals.
However, another possibility could be to consider this material as a
source for producing biodiesel by transesterification. In fact, production
of biodiesel from the risk material could represent a more economic
usage than its combustion. Siedel et al. have found that almost every
single step of the process leads to a significant reduction in the concen-
Sc
tration of the pathogenic prion protein (PrP ) in the main product and
by-products. They concluded that biodiesel from materials with a high
concentration of pathogenic prions can be considered safe [163]. Animal
fats, such as tallow or lard, have been widely investigated as a source
of biodiesel [164–169]. Muniyappa et al. have found that transesterifi-
cation of beef tallow produced a mixture of esters with a high concen-
tration in saturated fatty acids, but with physical properties similar to
esters of soybean oil [37]. Ma et al. found that 0.3% NaOH completed