- Biofuel defined broadly is solid, liquid, or gas fuel
consisting of, or derived from biomass. The more narrow
definition is liquid or gas fuel derived from biomass and used
as a fuel in transportation. This article uses the narrow
definition. When biomass used directly as a fuel is commonly
called biomass fuel
Biomass is recently living organisms or their metabolic
byproducts - such as feces from cows. It is a renewable energy
source, unlike other natural resources such as petroleum, coal,
and nuclear fuels. Agricultural products specifically grown for
use as biofuels include corn and soybeans, primarily in the
United States; flaxseed and rapeseed, primarily in Europe; sugar
cane in Brazil; palm oil in South-East Asia; and jatropha (though
not an agricultural product) in India. Biodegradable outputs
from industry, agriculture, forestry and households can be used;
examples include straw, timber, manure, rice husks, sewage,
biodegradable waste, and food leftovers; they can be converted
to biogas through anaerobic digestion. Biomass used as fuel
often consists of underutilized types, like chaff and animal
waste. The quality of timber or grassy biomass does not have a
direct impact on its value as an energy-source.
Biofuels are currently significantly less carbon neutral than
other forms of renewable energy due to the high use of fossil
fuels in the production of biofuels. The combustion of biofuels
produce carbon dioxide and other greenhouse gases. The carbon in
biofuels is often taken to have been recently extracted from
atmospheric carbon dioxide by plants as they have grown. The
potential for biofuels to be considered to be "carbon neutral"
depends upon the carbon that is emitted being reused by further
plant growth. Clearly however, cutting down trees in forests
that have grown for hundreds, or thousands of years for use as a
biofuel, without the replacement of this biomass would not have
a carbon neutral effect. Many people believe that a way to
reduce the amount of carbon dioxide released into the atmosphere
is to use biofuels to replace non-renewable sources of energy.
Much research is being done about the use of microalgae as an
energy source, with applications for biodiesel, ethanol,
methanol, methane, and even hydrogen. The production of biofuels
to replace oil and natural gas is in active development,
focusing on the use of cheap organic matter (usually cellulose,
agricultural and sewage waste) in the efficient production of
liquid and gas biofuels which yield high net energy gain. One
advantage of biofuel over most other fuel types is that it is
biodegradable, and so relatively harmless to the environment if
Solid biofuels such as wood or dried waste have been used since
man learned to control fire.
Liquid biofuels for industrial applications was used since the
early days of the car industry. Nikolaus August Otto, the German
inventor of the combustion engine, conceived his invention to
run on ethanol. Rudolf Diesel, the German inventor of the Diesel
engine, conceived it to run on peanut oil. Henry Ford originally
had designed the Ford Model T, a car produced from 1903 to 1926,
to run completely on ethanol, after surreptitious
efforts were successful at thwarting Ford's
desires to mass produce electric cars. However, when crude oil
was cheaply extracted from deeper in the soil (thanks to oil
reserves discovered in Pennsylvania and Texas), cars began using
fuels from oil.
Nevertheless, before World War II, biofuels were seen as
providing an alternative to imported oil in countries such as
Germany, which sold a blend of gasoline with alcohol fermented
from potatoes, called Reichskraftsprit. In Britain, grain
alcohol was blended with petrol by the Distillers Company
Limited under the name Discol and marketed through Esso's
After the war, cheap Middle Eastern oil lessened interest in
biofuels. But the oil shocks of 1973 and 1979 increased interest
from governments and academics. The counter-shock of 1986 again
reduced oil prices and interest. But since about 2000, rising
oil prices, concerns over the potential oil peak, greenhouse gas
emissions (global warming), and instability in the Middle East
are pushing renewed interest in biofuels. Government officials
have made statements and given aid in favour of biofuels. For
example, US president George W. Bush said in his 2006 State of
the Union speech that he wants the US to replace 75% of the oil
it imports from the Middle East by biofuels by 2025.
Bioenergy from wastes
The use of waste derived biofuels (biowastes) has many benefits.
A recent publication by the European Union projected the
potential of waste derived bioenergy to contribute to prevention
of global warming. It concluded that 19 million tons of oil
equivalent is available from biomass by 2020, 46% of which would
be derived from bio-wastes: MSW, agricultural residues, farm
wastes and other biodegradable waste streams.
Landfills generate a by-product known as landfill gas, which is
an excellent source of renewable energy. Landfill gas (LFG) can
be used either directly by industry or to generate electricity
for public consumption. In fact, when handled effectively, this
previously ignored resource has a lot to offer. Landfill gas
contains approximately 50 percent methane, which makes it an
excellent source of energy. On the down side, methane has a
global warming potential of 21 relative to CO2. In other words,
one ton of methane produces the same greenhouse gas (GHG) effect
as 21 tons of CO2.
Biofuels in developing countries
Unfortunately, much cooking with biofuels is done indoors, with
inefficient ventilation, and fuels such as dung cause airborne
pollution. This can be a serious health hazard; 1.3 million
deaths were attributed to this cause by the International Energy
Agency in its World Energy Outlook 2006.
Proposed solutions include improved stoves (including those with
inbuilt flues) and alternative fuels. But most of these have
difficulties. One is that flues are easily damaged. Another is
that alternative fuels tend to be expensive, and people who use
biofuels often do so precisely because they cannot afford
Organizations such as Intermediate Technology Development Group
work to make improved facilities for biofuel use and better
alternatives accessible to those who cannot get them. This is
done by improving ventilation, switching to different uses of
biomass such as the creation of biogas from solid biomatter, or
switching to other alternatives such as micro-hydro power.
Many environmentalists are concerned that first-growth forest
may be felled in countries such as Indonesia to make way for
palm oil plantations, driven by rising demand for diesel in SE
Asia and Europe.
First Generation Biofuels
'First-generation fuels refer to biofuels made from sugar,
starch, vegetable oil, or animal fats using conventional
Biofuels are commonly used throughout the world. The most common
use for biofuels is automotive transport. Essentially a biofuel
can be produced from any short term carbon cycle organic
compound; due to this there is a high variety of resources and
therefore many types of biofuels, below is a list of the more
commonly used biofuels.
Vegetable oil used as a fuel is produced using the same methods
as vegetable oil used for consumption. The quality of the oil
may be a lot lower for fuel use. Vegetable oil can be used in
many older diesel engines (equipped with indirect injection
systems), but only in the warmest climates. Usually it is turned
into biodiesel instead. No engine manufacturer explicitly allows
any use of vegetable oil in their engines.
Biodiesel is the most common biofuel in Europe. It is produced
from any oil or fat using transesterification to get a liquid
similar to mineral diesel. It can be used in any diesel engine
and can be mixed with mineral diesel in any percentage. In some
countries manufacturers cover many of their diesel engines under
warranty for 100% biodiesel use, although Volkswagen Germany,
for example, asks drivers to make a telephone check with the VW
environmental services department before switching to 100%
biodiesel (see biodiesel use). Many people have run thousands of
miles on biodiesel without problem, and many studies have been
made on 100% biodiesel. In many European countries, 5% biodiesel
blend is widely used and is available at thousands of gas
Ethanol is the most common biofuel worldwide. It is an alcohol
fuel. It can be produced from wheat, corn and sugar cane and
many other biomass stocks. The production methods used are
fermentation of the sugars, distillation and drying. Ethanol can
be used in the petrol engine as a replacement to gasoline; it
can be mixed with gasoline to any percentage, see common ethanol
fuel mixtures for information on ethanol. However, until the
recent introduction of new engines, cars would need to have
their engines modified in order to run with 100% alcohol.
Butanol is often claimed as a direct replacement for gasoline.
It is not in wide spread production at this time, and engine
manufacturers have not made statements about its
use[verification needed]. While on paper (and a few lab tests)
it appears that butanol has sufficiently similar characteristics
with gasoline such that it should work without problem in any
gasoline engine, no widespread experience exists. Butanol is
formed by ABE fermentation (acetone, butanol, ethanol) and
experimental modifications of the process show potentially high
net energy gains with butanol as the only liquid product.
Allegedly, butanol can be burned "straight" in existing gasoline
engines (without modification to the engine or car), produces
more energy and is less corrosive and less water soluble than
ethanol, and can be distributed via existing infrastructures.
Methanol, which is now produced from natural gas, can also be
produced from biomass — although this is not economically viable
at present. The methanol economy is an interesting alternative
to the hydrogen economy.
Biologically produced alcohols, most commonly ethanol and less
commonly propanol and butanol, are produced by the action of
microorganisms and enzymes through fermentation.
Biogas is produced by the process of anaerobic digestion of
organic material by anaerobes. It can be produced either from
biodegradable waste materials or by the use of energy crops fed
into anaerobic digesters to supplement gas yields. The solid
byproduct, digestate, can also be used as a biofuel.
Biogas contains methane and can be recovered in industrial
anaerobic digesters and mechanical biological treatment systems.
Landfill gas is a less clean form of biogas which is produced in
landfills through naturally occurring anaerobic digestion. If it
escapes into the atmosphere it is a potent greenhouse gas.
Oils and gases can be produced from various biological wastes:
* Thermal depolymerization of waste can extract methane and
other oils similar to petroleum.
* GreenFuel Technologies Corporation developed a patented
bioreactor system that uses nontoxic photosynthetic algae to
take in smokestacks flue gases and produce biofuels such as
biodiesel, biogas and a dry fuel comparable to coal.
Solid Biofuels Examples include wood, charcoal, and dried
Second Generation Biofuels
'Second-generation fuels are made from lignocellulosic biomass
feedstock using advanced technical processes'
Second generation biofuels use biomass to liquid technology. The
following second generation biofuels are under development:
* HTU diesel
* Fischer-Tropsch diesel
* Mixed Alcohols (i.e., mixture of mostly ethanol, propanol and
butanol, with some pentanol, hexanol, heptanol and octanol)
Bio-DME, Fischer-Tropsch, BioHydrogen diesel, Biomethanol and
Mixed Alcohols all use syngas for production. This syngas is
produced by gasification of biomass. HTU (High Temperature
Upgrading) diesel is produced from particularly wet biomass
stocks using high temperature and pressure to produce an oil.
BioHydrogen is the same as hydrogen except it is produced
from a biomass feedstock. This is done using gasification of the
biomass and then reforming the methane produced. BioHydrogen can
be used in fuel cells to produce electricity.
Bio-DME is the same as DME but is produced from a
bio-sources. Bio-DME can be produced from Biomethanol using
catalytic dehydration or it can be produced from syngas using
DME synthesis. DME can be used in the compression ignition
Biomethanol is the same as methanol but it is produced
from biomass. Biomethanol can be blended with petrol up to
10-20% without any infrastructure changes.
HTU diesel is produced from wet biomass. It can be mixed
with fossil diesel in any percentage without need for
Fischer-Tropsch diesel (FT) diesel is produced using
gas-to-liquids technology. FT diesel can be mixed with fossil
diesel at any percentage without need for infrastructure change.
Mixed Alcohols are produced from syngas with catalysts
similar to those used for methanol. Most R&D in this area is
concentrated in producing mostly ethanol. However, some fuels
are marketed as mixed alcohols. Mixed alcohols are superior to
pure methanol or ethanol, in that the higher alcohols have
higher energy content. Also, when blending, the higher alcohols
increase compatibility of gasoline and ethanol, which increases
water tolerance and decreases evaporative emissions. In
addition, higher alcohols have also lower heat of vaporization
than ethanol, which is important for cold starts. (For another
method for producing mixed alcohols from biomass see
bioconversion of biomass to mixed alcohol fuels)
Recognizing the importance of implementing bioenergy, there are
international organizations such as IEA Bioenergy, established
in 1978 by the International Energy Agency (IEA), with the aim
of improving cooperation and information exchange between
countries that have national programs in bioenergy research,
development and deployment.
The European Union has set a goal:
* For 2010 that each member state should achieve at least 5.75%
biofuel usage of all used traffic fuel.
* For 2020, 10 %.
UN Biofuel Report
The recent UN biofuel report raises the issues about the link
between biofuels, deforestation and food production. It warns
western policy makers that a too rapid change to biofuels could
be harmful if communities are excluded from ownership. It
emphasizes that biofuels can be part of the solution to climate
change but that current methods of biofuel crop growth in third
world countries can have damaging effect to both the local
communities and ecology. It also brings up the food crop over
fuel crop question. What is the right balance between food and
fuel and how can it be insured that western countries are not
funding hungry third world countries to grow inedible fuel
crops. For the actual report please follow.
Rising food prices
Due to rising demand for biofuels, farmers in countries with
limited agricultural potential are enticed to convert from
production of food to production of raw material for biofuels.
However, in the developing world, where a majority of people are
farmers and where a vast mass of unused agricultural land
exists, the biofuels opportunity may benefit millions of farmers
and fuel economic development. If managed in a careless manner,
the situation may lead to a rise in food prices, which may hurt
In early 2007 there were a number of reports linking stories as
diverse as food riots in Mexico due to rising prices of corn for
tortillas and reduced profits at Heineken, the large
international brewer, to the increasing use of corn (maize)
grown in the US Midwest for bio-ethanol production. (In the case
of beer, it is more that barley acreage was cut to meet growing
demand for corn, rather than the direct conversion of barley to
ethanol, although the latter is technically possible.)
Ecologist and environmental campaigner George Monbiot has argued
in the British newspaper The Guardian for a 5 year freeze on
biofuels while their impact on poor communities and the
environment is assessed.
It is, however, important to note that the edible portions of
the food crops are not the most desirable portion of the plant
for creating biofuel. The cellulose contained in the inedible
stalks of these plants, while more difficult to process, contain
far more complex hydrocarbons (the basis of any diesel-type
fuel) Much research is currently being done into processes to
turn these waste products into fuel, without having to deplete
the much-needed food supply.
Energy efficiency of biodiesel
Production of biofuels from raw materials requires energy (for
farming, transport and conversion to final product as well as
the production of fertilizers and many types of pesticides and
herbicides)and this varies greatly from one location to another.
For example, in the US and Australia, farmers use much more oil
to power their equipment than farmers in Brazil. However, in
some areas where forests are being thinned for forest fire fuels
reduction projects, the production of the necessary biomass
would occur whether or not a biomass industry existed. Therefore
only the transport of the biomass from the field to a processing
facility is a net energy cost. The costs of transporting wood
chip have proven to be difficult to overcome.
Also studies on the energy balance of these fuels show large
differences depending on the biomass feedstock used and
location. Biofuels made from crops grown in temperate climates
(such as corn or canola) have a relatively low energy
efficiency, whereas biofuels made from crops grown in the
subtropics and the tropics (such as sugarcane, sweet sorghum,
palm oil, cassava) show a very high energy efficiency. For some
biofuels (like ethanol made from corn) the energy balance may
even be negative.
A European study on the greenhouse gas emissions found that
well-to-wheel(WTW) CO2 emissions of biodiesel from seed crop,
like rapeseed could be almost as high as fossil diesel. It
showed a similar result for bio-ethanol from starch crops which
could have almost as many WTW CO2 emissions as fossil petrol. It
also showed that second generation biofuels have a much fewer
WTW CO2 emissions.
Biofuels offer one of the few options to substantially mitigate
climate change. Since the effects of global warming can be
devastating to world agriculture, the ecological impacts of
growing biofuel crops may be small compared to the potentially
much larger impacts of unmitigated climate change.
Biofuels are based on natural renewable organic compounds. These
compounds are made by plants or animals. The energy that is
stored in these chemicals originally comes from the sun
(photosynthesis). When the fuels are burned the "exhaust"
created is only something that was already in the atmosphere to
begin with. Carbon dioxide is converted to sugar, this sugar is
then used as a fuel or used to make the fuel that is eventually
burned releasing the carbon dioxide back into the atmosphere.
Since vast amounts of raw material are needed for biofuel
production, monocultures and intensive farming may become more
popular, which may cause environmental damages and undo some of
the progress made towards sustainable agriculture. On the other
hand, in the developing world poverty is the main cause of
environmental destruction. If farmers in the developing world
become energy farmers who sell biofuels on the international
market, their incomes would increase substantially, and
pressures on the environment would decrease. In this sense, the
biofuels opportunity offers a way to lower the indirect impacts
of poverty on the environment.
All crops consume nutrients and organic matter. For a
sustainable system these must be replenished. The major food
producers use intensive farming methods with continuous cropping
being a common practice. Intensive farming precludes the
sustainable techniques of rotation and fallow and therefore
requires importation to replenish the soil. Importation
establishes a process of mining nutrients and matter that are in
themselves finite just as is oil. Therefore the crop is
renewable but the imports and consumables are not renewed. There
is the hazard that mass production of crops for bio fuel will
further cause the consuming of natural resources and a
degradation of soil that will bring about erosion and
desertification creating a decline in plant production.
Even though biofuels can have a positive effect regarding the
carbon cycle they can still cause local pollution; smog is one
of those. Biodiesel can have this particular problem when used
in certain unmodified diesel engines; due to the higher Nox