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The world is presently confronted with the twin crises of fossil fuel depletion and environmental
degradation. Excessive use of fossil fuels has led to global environmental degradation effects
such as greenhouse effect, acid rain, ozone depletion and climate change. The search for
alternative fuels, which promise a harmonious correlation with sustainable development,
energy conservation, efficiency and environmental preservation, has become highly pronounced
in the present context. Biodiesel is a globally bio renewable liquid transportation fuel. Biodiesel
has become more attractive recently because of its environmental benefits. It provides more
usable energy than the fossil energy needed for its production, reduces greenhouse gases
(GHGs), reduces several major air pollutants, and has minimal impact on human and
environmental health through N, P, and pesticide release.
(Advantages of biodiesel
The advantage of biodiesel as diesel fuel are its portability, ready availability, renewability,
higher combustion efficiency, lower Sulphur and aromatic content, higher cetane number and
higher biodegradability.
Disadvantages of biodiesel
Disadvantages of biodiesel as diesel fuel are its higher viscosity, lower energy content, higher
cloud point and pour point, higher nitrogen oxide emission, lower engine speed and power,
injector coking, engine compatibility, high price, and higher engine wear.
https://www.ripublication.com/ijeem_spl/ijeemv4n4_11.pdf
Environmental effect :
Biofuels are renewable and sustainable. That means that farmers can dedicate land to growing
energy crops -- plants that will one day be used to create fuel. Potential crops include corn, soy,
rapeseed and switchgrass. Some of these plants, such as switchgrass, can grow in conditions
unsuitable for other crops.
Biofuels burn cleaner than fossil fuels. They don't produce sulfur or aromatics, so there's no
unpleasant smell associated with burning biofuels. They still release greenhouse gases like
carbon dioxide but do so at reduced levels. According to a report by the National Renewable
Energy Laboratory (NREL), biodiesel produce 78.5 percent fewer carbon dioxide emissions than
petroleum diesel. In addition, biofuels act as carbon sinks while they grow -- they capture
carbon. When you factor both the reduced emissions and the carbon capture factor, biofuels
come out on top.
Another benefit to biofuels is the reduced danger of an environmental disaster. In 2010, an
underwater oil well burst in the Gulf of Mexico. It released millions of gallons of oil, causing an
unknown amount of damage in the process. Biofuels are safer -- a field of corn isn't going to
poison the ocean.
So why don't we switch to biofuels now?
It would require a fundamental shift in farming. Energy consumption is at an all-time high. To

meet demand, we would have to devote more land to growing energy crops than we have
available. At best, we can only supplement our current need for energy using biofuels.
In addition, extensive use of chemical fertilizer to grow energy crops could create nitrate-rich
runoff that could encourage algae to bloom and choke out other water-borne species. Mining
phosphorus for fertilizer can be hazardous to the environment, too -- the process leaves behind
radioactive material.
While reducing our use of fossil fuels would help the environment, we would need to either
reduce our energy consumption or invest in other forms of renewable energy to stop using
them completely.
https://auto.howstuffworks.com/fuel-efficiency/biofuels/environmental-benefits-
biofuel.htm
Health Effects
Biodiesel is safer for people to breathe. Research conducted in the US shows biodiesel
emissions have decreased levels of all target polycyclic aromatic hydrocarbons (PAH) and
nitrited PAH compounds, as compared to petroleum diesel exhaust. PAH and nPAH compounds
have been identified as potential cancer causing compounds. Targeted PAH compounds were
reduced by 75 to 85 percent, with the exception of benzo(a) anthracene, which was reduced by
roughly 50 percent. Target nPAH compounds were also reduced dramatically with biodiesel fuel,
with 2-nitrofluorene and 1-nitropyrene reduced by 90 percent, and the rest of the nPAH
compounds reduced to only trace levels. All of these reductions are due to the fact the biodiesel
fuel contains no aromatic compounds.
Energy Balance
Biodiesel helps preserve and protect natural resources. For every one unit of energy needed to
produce biodiesel, 5.5 units of energy are gained. Because of this high 350 Mohd Moiz Khan et
al energy balance and since it is domestically produced, biodiesel use can greatly contribute to
domestic energy security. Among current food-based biofuels, soybean biodiesel has major
advantages over corn grain ethanol. Biodiesel provides 93% more usable energy than the fossil
energy needed for its production.
Biodegradability and Toxicity

Biodiesel is nontoxic and biodegradable. Tests sponsored by the United States Department of
Agriculture confirm that biodiesel is ten times less toxic than table salt and biodegrades as fast
as dextrose (a test sugar)
Effect of biofuels on emissions

For the current vehicle fleet, the available emission data show large variation, both positive and
negative. This is caused by variations in biofuel properties, vehicle technology, engine
management and the driving cycle. It applies to both petrol and diesel engines and especially to
light duty vehicles, i.e. passenger cars and delivery vans. Due to these many influencing factors
and to relatively small amount of available emission data it is not possible to draw firm
conclusions regarding the emission impact of biofuels on a national scale. For future vehicles,
the emission levels of petrol engines are expected to improve as biofuels will be implemented in
Euro 5 (2010/2012), but petrol engine emissions are low anyhow. For diesel engines, the
variability is likely to persist, due to the large sensitivity of the emission control technologies
needed to meet the Euro 5/V legislation. In particular for NOx, there appears a risk of a steep
rise in emissions with the use of biodiesel. The extent to which this will pose problems with
future engines depends strongly on the way biofuels are implemented in future emission
legislation. For synthetic diesel (BTL, GTL) the picture is brighter. Generally reductions of both
NOx and particulate matter are seen, but at the expense of a slightly lower fuel economy and
power. For future engines positive effects on emissions are expected to diminish.
https://english.rvo.nl/sites/default/files/2013/11/Rapport%20Impact%20of
%20biofuels%20on%20air%20pollutant%20emissions%20from%20road
%20vehicles%20TNO-08-06.pdf
Diesel engines as a source of air pollution & associated health effects
 Exposure to the extremely tiny particles and gaseous pollutants generated by the
combustion of petroleum diesel fuel is associated with a wide array of negative human
health effects.
Biodiesel: a better alternative for air quality?
 Studies have shown use of biodiesel blends in diesel engines reduces tailpipe emissions
of particulate matter, total hydrocarbons and total polycyclic aromatic hydrocarbons.
However, other studies have reported that biodiesel combustion reduces particle size,
changes particle-associated metal composition and increases or decreases
concentrations of certain air toxics. Toxicological studies are limited.
Biodiesel: comparing emissions versus exposures
 The real-world variability in engines and driving cycles, fate and transport processes, and
other factors make it difficult to predict exposure to biodiesel based solely on emissions
data sets. Exposure assessment techniques can provide important data connecting
sources of emissions to health effects.
Biodiesel’s impact on exposure in an occupational setting
 While there have been few biodiesel exposure studies performed, recent research
supports that biodiesel use in heavy-duty equipment reduces occupational exposure to
fine particulate matter.
future perspective
 As biodiesel fuel feedstocks, blend percentages and engine after treatment technologies
rapidly change, both emissions and exposure research are needed to develop a fuller
understanding of biodiesel’s impact on air quality and human health.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3622266/
Other Methods of Biodiesel Production:

During last two decades, efforts are being made to produce biodiesel not only by
transesterification but also by various other processes like thermal depolymerization. Great
efforts are being made throughout the world to develop new cost effective methods producing
superior product in terms of quality as well as quantity. One such method involves hydro
processing of vegetable oils to produce biofuel named bio distillate, production of which
involves same straight-chain vegetable oils (SVO) as reactants. However, unlike biodiesel
production where SVO are processed via transesterification reaction, bio distillates are put
through hydro treatment process. Green diesel name has been coined for hydro processed fuel.
Blending of bio distillates with petroleum diesel result in reduction of all regulated emissions,
including NOx. Lack of aromatics and sulfur accompanied by a high cetane number make green
diesel/bio distillate a premium blend stock28.Hydroprocessed green diesel has potential to
displace more petroleum resources per energy content in fuel as compared to biodiesel.
Decrease of lifecycle greenhouse gas (GHG) emissions resulting from bio distillate use will vary
based on feedstock used for production. On an average, greater reductions in GHG emissions
are obtained from the use of bio distillates than biodiesel29.
(PDF) Effect of impurities on performance of biodiesel: A review. Available from:

https://www.researchgate.net/publication/228859806_Effect_of_impurities_on_
performance_of_biodiesel_A_review [accessed Sep 18 2018].

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The world is presently confronted with the twin crises of fossil fuel depletion and environmental

So why don't we switch to biofuels now?

It would require a fundamental shift in farming. Energy consumption is at an all-time high. To

Biodegradability and Toxicity

Effect of biofuels on emissions

Diesel engines as a source of air pollution & associated health effects

Biodiesel: comparing emissions versus exposures

Biodiesel’s impact on exposure in an occupational setting

Other Methods of Biodiesel Production:

(PDF) Effect of impurities on performance of biodiesel: A review. Available from:

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