Microalgae as an Attractive Source for Biofuel Production - Environmental Sustainability: Role of Green Technologies - page 126

Biofuels

First generation

Second generation

Third generation

Ethanol-based fuels obtained
from the fermentation of sugars
(corn, beet, sugarcane etc.)

By conventional methods,
production of bioethanol or
butanol based on novel starch, oil
and sugar crops such as

Biodiesel from microalgae

Bioethanol from microalgae and
seaweeds

Jatropha ,

Vegetable oil-based (raw oil,
biodiesel and renewable diesel
produced from catalytic
hydrodeoxygenation)

Cassava or Miscanthus

Biohydrogen from green
microalgae and microbes

Lignocellulosic materials (eg.
straw, wood, leaves, grass, etc.)
used for the production of
bioethanol, biobutanol and
syndiesel

Oleaginous plants (colza, palm,
canola etc.) and biogas emitted
from raw materials or landfills

Although fi rst-generation biofuel production
capacities have increased, they have considerable
economic and environmental limitations. A lack
of agricultural land and deforestation (National
Research Council 2007 ; Goldemberg and
Guardabassi 2009 ) has led to competition with
agriculture for arable land used for food produc-
tion. For example, in some European countries
such as France, production of fi rst-generation
biofuels using arable land available from the cul-
tivation of oleaginous plants will not be able to
support demand for biofuels by 2015 unless fal-
low land is saturated, which in turn would create
soil impoverishment problems. According to the
International Energy Agency (IEA 2008 ), about
1 % (14 million hectares) of the world's available
arable land is used for the production of biofuels,
providing 1 % of global transport fuels. This
clearly shows that an increase in the share to any-
where near 100 % is unfeasible due to the severe
impact on the world's food supply and the large
areas of production land required.
Second-generation biofuels contain high
amounts of free fatty acids; however, additional
production steps demand increased energy and
production costs (Demirbas 2008 ). The major
limitation associated with the use of second-
generation biofuels is the issue of sustainability.
For biodiesel to be produced from Jatropha , half

of the land area of the UK (17.5 million hect-
ares) would be required to fulfi ll the diesel
requirement of the UK (estimated 25 billion
liters in 2008). The total energy input for the life
cycle of rapeseed and soybean is estimated to be
half the total energy of the fuel (Scott et al.
2010 ). The third largest biodiesel feedstock is
palm oil. Universally, 10 % of palm oil is being
used as a biodiesel source. The major disadvan-
tage of palm oil biodiesel is poor cold fl ow prop-
erties, which can be overcome by blending with
triglycerides to improve cold fl ow and cloud
point properties (Sarin et al. 2009 ). High produc-
tion of palm oil requires vast areas of natural
vegetation; it can also indirectly cause damage to
the ecosystem due to devastating fi res. In addi-
tion, it has a negative impact on terrestrial and
aquatic environments due to palm mill effl uent
(Ahmad et al. 2011 ).
Production of fi rst- and second-generation
biodiesel from crops is not affordable. Therefore,
competition between biodiesel feedstock pro-
duction and food production mean it is neces-
sary to fi nd other ways to lower the cost of
biodiesel production and reduce the pressure on
food and feed supplies. Biodiesel also has one
major limitation: it does not fully replace other
petroleum diesel and biomass-based diesels,
meaning that one gallon of biodiesel does not