PLANT OILS
A variety of
oils can be used to produce biodiesel. These include:
• Virgin oil feedstock;
rapeseed and soybean oils are most commonly used, soybean oil alone accounting
for about ninety percent of all fuel stocks in the US. It also can be obtained
from field pennycress and jatropha and other crops such as mustard, flax, sunflower,
palm oil, coconut, hemp (see list of vegetable oils for biofuel for more
information);
• Waste vegetable oil
(WVO);
• Animal fats including
tallow, lard, yellow grease, chicken fat,[48] and the by-products of the
production of Omega-3 fatty acids from fish oil.
• Algae, which can be grown
using waste materials such as sewage[49] and without displacing land currently
used for food production.
• Oil from halophytes such
as Salicornia bigelovii, which can be grown using saltwater in coastal areas where
conventional crops cannot be grown, with yields equal to the yields of soybeans
and other oilseeds grown using freshwater irrigation[50]
Many advocates suggest that waste vegetable oil is
the best source of oil to produce biodiesel, but since the available supply is
drastically less than the amount of petroleum-based fuel that is burned for
transportation and home heating in the world, this local solution does not
scale well.
Animal fats are
a by-product of meat production. Although it would not be efficient to raise
animals (or catch fish) simply for their fat, use of the by-product adds value
to the livestock industry (hogs, cattle, poultry). However, producing biodiesel
with animal fat that would have otherwise been discarded could replace a small
percentage of petroleum diesel usage. Today, multi-feedstock biodiesel
facilities are producing high quality animal-fat based biodiesel.[citation
needed] Currently, a 5-million dollar plant is being built in the USA, with the
intent of producing 11.4 million litres (3 million gallons) biodiesel from some
of the estimated 1 billion kg (2.2 billion pounds) of chicken fat[51] produced
annually at the local Tyson poultry plant.[48] Similarly, some small-scale
biodiesel factories use waste fish oil as feedstock.[52][53] An EU-funded
project (ENERFISH) suggests that at a Vietnamese plant to produce biodiesel
from catfish (basa, also known as pangasius), an output of 13 tons/day of
biodiesel can be produced from 81 tons of fish waste (in turn resulting from
130 tons of fish). This project utilises the biodiesel to fuel a CHP unit in
the fish processing plant, mainly to power the fish freezing plant.[54]
Quantity of feedstocks required
Current
worldwide production of vegetable oil and animal fat is not sufficient to
replace liquid fossil fuel use. Furthermore, some object to the vast amount of
farming and the resulting fertilization, pesticide use, and land use conversion
that would be needed to produce the additional vegetable oil. The estimated
transportation diesel fuel and home heating oil used in the United States is
about 160 million tons (350 billion pounds) according to the Energy Information
Administration, US Department of Energy.[55] In the United States, estimated
production of vegetable oil for all uses is about 11 million tons (24 billion
pounds) and estimated production of animal fat is 5.3 million tonnes (12
billion pounds).[56]
If the entire
arable land area of the USA (470 million acres, or 1.9 million square
kilometers) were devoted to biodiesel production from soy, this would just
about provide the 160 million tonnes required (assuming an optimistic 98 US
gal/acre of biodiesel). This land area could in principle be reduced
significantly using algae, if the obstacles can be overcome. The US DOE estimates
that if algae fuel replaced all the petroleum fuel in the United States, it
would require 15,000 square miles (38,849 square kilometers), which is a few
thousand square miles larger than Maryland, or 1.3 Belgiums,[57][58] assuming a
yield of 140 tonnes/hectare (15,000 US gal/acre). Given a more realistic yield
of 36 tonnes/hectare (3834 US gal/acre) the area required is about 152,000
square kilometers, or roughly equal to that of the state of Georgia or England
and Wales. The advantages of algae are that it can be grown on non-arable land
such as deserts or in marine environments, and the potential oil yields are
much higher than from plants.
Yield
Feedstock yield
efficiency per unit area affects the feasibility of ramping up production to
the huge industrial levels required to power a significant percentage of
vehicles.
Algae fuel
yields have not yet been accurately determined, but DOE is reported as saying
that algae yield 30 times more energy per acre than land crops such as
soybeans.[60] Yields of 36 tonnes/hectare are considered practical by Ami
Ben-Amotz of the Institute of Oceanography in Haifa, who has been farming Algae
commercially for over 20 years.[61]
Jatropha has
been cited as a high-yield source of biodiesel but yields are highly dependent
on climatic and soil conditions. The estimates at the low end put the yield at
about 200 US gal/acre (1.5-2 tonnes per hectare) per crop; in more favorable
climates two or more crops per year have been achieved.[62] It is grown in the
Philippines, Mali and India, is drought-resistant, and can share space with
other cash crops such as coffee, sugar, fruits and vegetables.[63] It is
well-suited to semi-arid lands and can contribute to slow down desertification,
according to its advocates.[64]
Efficiency and economic arguments
According to a
study by Drs. Van Dyne and Raymer for the Tennessee Valley Authority, the
average US farm consumes fuel at the rate of 82 litres per hectare (8.75 US
gal/acre) of land to produce one crop. However, average crops of rapeseed
produce oil at an average rate of 1,029 L/ha (110 US gal/acre), and high-yield
rapeseed fields produce about 1,356 L/ha (145 US gal/acre). The ratio of input
to output in these cases is roughly 1:12.5 and 1:16.5. Photosynthesis is known to
have an efficiency rate of about 3-6% of total solar radiation[65] and if the
entire mass of a crop is utilized for energy production, the overall efficiency
of this chain is currently about 1%[66] While this may compare unfavorably to
solar cells combined with an electric drive train, biodiesel is less costly to
deploy (solar cells cost approximately US$1,000 per square meter) and transport
(electric vehicles require batteries which currently have a much lower energy
density than liquid fuels). A 2005 study found that biodiesel production using
soybeans required 27% more fossil energy than the biodiesel produced and 118%
more energy using sunflowers.[67]
However, these
statistics by themselves are not enough to show whether such a change makes
economic sense. Additional factors must be taken into account, such as: the
fuel equivalent of the energy required for processing, the yield of fuel from
raw oil, the return on cultivating food, the effect biodiesel will have on food
prices and the relative cost of biodiesel versus petrodiesel, water pollution
from farm run-off, soil depletion[citation needed], and the externalized costs
of political and military interference in oil-producing countries intended to
control the price of petrodiesel.
The debate over
the energy balance of biodiesel is ongoing. Transitioning fully to biofuels
could require immense tracts of land if traditional food crops are used
(although non food crops can be utilized). The problem would be especially
severe for nations with large economies, since energy consumption scales with
economic output.[68]
If using only
traditional food plants, most such nations do not have sufficient arable land
to produce biofuel for the nation's vehicles. Nations with smaller economies
(hence less energy consumption) and more arable land may be in better
situations, although many regions cannot afford to divert land away from food
production.
For third world
countries, biodiesel sources that use marginal land could make more sense;
e.g., honge oil nuts grown along roads or jatropha grown along rail lines.[69]
In tropical
regions, such as Malaysia and Indonesia, plants that produce palm oil are being
planted at a rapid pace to supply growing biodiesel demand in Europe and other
markets. Critics argue[citation needed] that the removal of rainforest for palm
plantations is not ecologically sound. It has been estimated in Germany that
palm oil biodiesel has less than one third of the production costs of rapeseed
biodiesel.[70] The direct source of the energy content of biodiesel is solar
energy captured by plants during photosynthesis. Regarding the positive energy
balance of biodiesel[citation needed]:
When straw was
left in the field, biodiesel production was strongly energy positive, yielding
1 GJ biodiesel for every 0.561 GJ of energy input (a yield/cost ratio of 1.78).
When straw was
burned as fuel and oilseed rapemeal was used as a fertilizer, the yield/cost
ratio for biodiesel production was even better (3.71). In other words, for
every unit of energy input to produce biodiesel, the output was 3.71 units (the
difference of 2.71 units would be from solar energy).
Energy security
One of the main
drivers for adoption of biodiesel is energy security. This means that a
nation's dependence on oil is reduced, and substituted with use of locally
available sources, such as coal, gas, or renewable sources. Thus a country can
benefit from adoption of biofuels, without a reduction in greenhouse gas
emissions. While the total energy balance is debated, it is clear that the
dependence on oil is reduced. One example is the energy used to manufacture
fertilizers, which could come from a variety of sources other than petroleum.
The US National Renewable Energy Laboratory (NREL) states that energy security
is the number one driving force behind the US biofuels programme,[71] and a
White House "Energy Security for the 21st Century" paper makes it
clear that energy security is a major reason for promoting biodiesel.[72] The
EU commission president, Jose Manuel Barroso, speaking at a recent EU biofuels
conference, stressed that properly managed biofuels have the potential to
reinforce the EU's security of supply through diversification of energy
sources.[73]