Chemical Technology February 2015

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Life Cycle Assessment (LCA)
of biodiesel
Biodiesel may be defined as a monoalkyl ester of
long chain fatty acids derived from a renewable
lipid feedstock, such as vegetable oil or animal fat
(Basheer et al, 2012). Biodiesel production has received
considerable interest in the recent years as an alternative
to the diesel produced from fossil fuels. This is because
not only is biodiesel biodegradable and non-toxic, it also
has a higher flash point (about 423 K) making it less
volatile, safe to handle and to transport (Morais et al,
2010). It is compatible with currently existing technology
of diesel production, eliminating the need to reconstruct
and redesign equipment. Biodiesel has lower carbon mon-
oxide, NOx, SOx and particulates emissions as compared
to conventional diesel. Carbon dioxide emissions are not
considered important because they can be absorbed by
terrestrial plants through photosynthesis provided the highly
productive ecosystems are not replaced by the less photo-
synthetically active biodiesel crop (Kiwjaroun et al, 2008).
Biodiesel, however, has its disadvantages: its production
rate accounts for only 15 % of the transportation demands.
The reason why the conventional diesel cannot be replaced
completely by biodiesel is because its production competes
with the food crop; the only solution is to use more land for
biodiesel agriculture which leads to high costs. The costs of
vegetable oil can be up to 75 % of the whole process and
thus leading to the biodiesel process being 1,5 times more
expensive than conventional diesel (Morais et al, 2010).
Biodiesel utilises various feed-stocks, including waste
cooking oil, clean vegetable oil and animal fat. The advantage
of using waste cooking oil is that it serves as a waste treat-
ment process, thus solving waste disposal problems. Waste
cooking oil also leads to the reduction in the production costs
as compared to the vegetable oil.
The trans-esterification process is used in the production
of biodiesel. It involves a catalysed chemical reaction with
oil or fat (triglyceride) and alcohol as reactant. The reaction
products are biodiesel and glycerol.
Life Cycle Assessment (LCA)
A Life Cycle Assessment is a tool that is used to determine
or assess the impact of a product or a process on the en-
vironment. It evaluates the use of energy and raw material
consumption, wastes and emissions of a product's life cycle
(Navigant Consulting, Inc, 2012).
An LCA assesses a material or a product from 'cradle to
grave', meaning that a material is assessed from the mo-
ment raw materials are extracted from the environment,
its production, use, to the time the material is returned to
earth as waste (SAIC, 2006). An LCA is used to evaluate the
amount of energy, rawmaterials consumed, emissions to the
atmosphere as well as the amount of waste generated during
a product’s entire life cycle (Navigant Consulting, Inc, 2012).
Showing the environmental impacts of a product’s life cycle
using an LCA is helpful to decision makers when choosing
themost feasible process or whenmaking improvements. An
LCA is carried out using a method that has four stages which
Chemical Technology • February 2015 6
by T Sebitso, M Kharidzha and KG Harding, all of the School of
Chemical and Metallurgical Engineering, University of the
Witwatersrand, Johannesburg, South Africa
Although biodiesel is seen as an
eco-friendly alternative to fossil fuels,
the processing methods can vary its
environmental impact.