A major challenge mankind is facing in this century is the gradual and inescapable
exhaustion of the earth's fossil energy resources. The combustion of those fossil
energy materials lavishly used as heating or transportation fuel is one of the key
factors responsible for global warming. One of the most readily applicable alternative
energy resources is biodiesel, which is a potential substitute for petroleum-based
diesel fuel. Biodiesel is made from renewable biomass mainly by alkali-catalysed
transesterification of plant oils. Biodiesel offers a number of interesting and attractive
beneficial properties compared to conventional petroleum-based diesel. Most
importantly, the use of biodiesel maintains a balanced carbon dioxide cycle since it
is based on renewable biological materials. Pure biodiesel or biodiesel mixed in any
ratio with petroleum-based diesel can be used in conventional diesel engines with no
or only marginal modifications, and it can be distributed using the existing
A number of aspects of biodiesel production, by-product glycerol utilization and
utilisation in a test diesel engine facility are examined in the work described here.
The kinetics of biodiesel production by transesterification of plant oils with methanol
are described with reference to a novel solubility model that took into account the
phase behaviour of the reacting mixture. It was revealed that the formation of
methyl esters during the course of reaction promotes the dissolution of the oil in the
methanol phase. Using ternary phase diagrams (oil/methanol/methyl esters) a new
kinetic model that accounts for product-facilitated oil dissolution was developed. The
model described the experimentally obtained kinetics well and scope for further
future improvements to the model were identified.
The microbial conversion of by-product glycerol to alcohols could potentially reduce
dependency on methanol and improve process economics by re-cycling what will
increasingly become a waste product as biodiesel production gains greater prominence. Two species of bacteria, Pantoea agglomerans and Clostridium
pasteuranium were used in a fully instrumented bioreactor to investigate conversion
of glycerols to alcohols. Overall alcohol yields were promising and it is possible that
optimising the fermentation conditions for P. agglomerans still further could result in
still higher alcohol yields.
Bio diesel fuels in pure form and blended with mineral diesel in this study were
tested in a four cylinder direct injection engine, typically used in small diesel genset
applications. Engine performance and emissions were recorded at five load
conditions and at two different speeds. Results were obtained for measurements of
emission and smoke at the different speed and load conditions for the different bio
diesel fuels The findings show that there is an increase in the over all specific fuel
consumption at higher blends of bio diesel, but emissions were reduced at all blends
and oils used with the exception of NOx which increased. A simple combustion
analysis was also performed where ignition delay, position and magnitude of peak
cylinder pressure and heat release rate were examined to asses how the variation of
chemical structure and blend percentage affects engine performance.
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.