A BIOFUEL is a fuel that is produced through contemporary biological processes, such as agriculture and anaerobic digestion , rather than a fuel produced by geological processes such as those involved in the formation of fossil fuels , such as coal and petroleum, from prehistoric biological matter.
Biofuels can be derived directly from plants, or indirectly from agricultural, commercial, domestic, and/or industrial wastes. Renewable biofuels generally involve contemporary carbon fixation , such as those that occur in plants or microalgae through the process of photosynthesis . Other renewable biofuels are made through the use or conversion of biomass (referring to recently living organisms, most often referring to plants or plant-derived materials). This biomass can be converted to convenient energy-containing substances in three different ways: thermal conversion, chemical conversion, and biochemical conversion. This biomass conversion can result in fuel in solid , liquid , or gas form. This new biomass can also be used directly for biofuels.
Bioethanol is an alcohol made by fermentation , mostly from
carbohydrates produced in sugar or starch crops such as corn ,
sugarcane , or sweet sorghum . Cellulosic biomass , derived from
non-food sources, such as trees and grasses, is also being developed
as a feedstock for ethanol production.
In 2010, worldwide biofuel production reached 105 billion liters (28
billion gallons US), up 17% from 2009, and biofuels provided 2.7% of
the world's fuels for road transport. Global ethanol fuel production
reached 86 billion liters (23 billion gallons US) in 2010, with the
There are various social, economic, environmental and technical issues relating to biofuels production and use, which have been debated in the popular media and scientific journals. These include: the effect of moderating oil prices , the "food vs fuel " debate, poverty reduction potential, carbon emissions levels, sustainable biofuel production, deforestation and soil erosion , loss of biodiversity , impact on water resources , rural social exclusion and injustice, shantytown migration, rural unskilled unemployment, and nitrogen dioxide (NO2) emissions.
* 1.1 First-generation biofuels * 1.2 Second-generation biofuels * 1.3 Third-generation biofuels * 1.4 Fourth-generation biofuels
* 2 Types of biofuels
* 5 Debates regarding the production and use of biofuel
* 6 Current research
* 7 See also * 8 References * 9 Further reading * 10 External links
"First-generation" or conventional biofuels are biofuels made from food crops grown on arable land. With this biofuel production generation, food crops are thus explicitly grown for fuel production , and not anything else. The sugar, starch, or vegetable oil obtained from the crops is converted into biodiesel or ethanol, using transesterification, or yeast fermentation.
Main article: Second-generation biofuels
Second generation biofuels are fuels manufactured from various types of biomass . Biomass is a wide-ranging term meaning any source of organic carbon that is renewed rapidly as part of the carbon cycle . Biomass is derived from plant materials, but can also include animal materials.
Whereas first generation biofuels are made from the sugars and vegetable oils found in arable crops, second generation biofuels are made from lignocellulosic biomass or woody crops, agricultural residues or waste plant material (from food crops)
This has both advantages and disadvantages. The advantage is that, unlike with regular food crops, no arable land is used solely for the production of fuel. The disadvantage is that unlike with regular food crops, it may be rather difficult to extract the fuel. For instance, a series of physical and chemical treatments might be required to convert lignocellulosic biomass to liquid fuels suitable for transportation.
From 1978 to 1996, the US NREL experimented with using algae as a biofuels source in the " Aquatic Species Program ". A self-published article by Michael Briggs, at the UNH Biofuels Group, offers estimates for the realistic replacement of all vehicular fuel with biofuels by using algae that have a natural oil content greater than 50%, which Briggs suggests can be grown on algae ponds at wastewater treatment plants. This oil-rich algae can then be extracted from the system and processed into biofuels, with the dried remainder further reprocessed to create ethanol. The production of algae to harvest oil for biofuels has not yet been undertaken on a commercial scale, but feasibility studies have been conducted to arrive at the above yield estimate. In addition to its projected high yield, algaculture — unlike crop-based biofuels – does not entail a decrease in food production , since it requires neither farmland nor fresh water . Many companies are pursuing algae bioreactors for various purposes, including scaling up biofuels production to commercial levels. Prof. Rodrigo E. Teixeira from the University of Alabama in Huntsville demonstrated the extraction of biofuels lipids from wet algae using a simple and economical reaction in ionic liquids .
Similarly to third-generation biofuels, fourth-generation biofuels are made using non-arable land. However, unlike third-generation biofuels, they do not require the destruction of biomass. This class of biofuels includes electrofuels . and photobiological solar fuels . Some of these fuels are carbon-neutral .The conversion of crude oil from the plant seeds into useful fuels is called transesterification
TYPES OF BIOFUELS
The following fuels can be produced using first, second, third or fourth-generation biofuel production procedures. Most of these can even be produced using two or three of the different biofuel generation procedures.
Biologically produced alcohols , most commonly ethanol , and less
commonly propanol and butanol , are produced by the action of
microorganisms and enzymes through the fermentation of sugars or
starches (easiest), or cellulose (which is more difficult). Biobutanol
(also called biogasoline) is often claimed to provide a direct
replacement for gasoline, because it can be used directly in a
gasoline engine. U.S. President
George W. Bush
Ethanol fuel is the most common biofuel worldwide, particularly in
Corn-to-ethanol and other food stocks has led to the development of cellulosic ethanol . According to a joint research agenda conducted through the US Department of Energy, the fossil energy ratios (FER ) for cellulosic ethanol, corn ethanol, and gasoline are 10.3, 1.36, and 0.81, respectively.
With current subsidies, ethanol fuel is slightly cheaper per distance traveled in the United States.
Electronically controlled 'common rail ' and 'unit injector ' type
systems from the late 1990s onwards may only use biodiesel blended
with conventional diesel fuel. These engines have finely metered and
atomized multiple-stage injection systems that are very sensitive to
the viscosity of the fuel. Many current-generation diesel engines are
made so that they can run on B100 without altering the engine itself,
although this depends on the fuel rail design. Since biodiesel is an
effective solvent and cleans residues deposited by mineral diesel,
engine filters may need to be replaced more often, as the biofuel
dissolves old deposits in the fuel tank and pipes. It also effectively
cleans the engine combustion chamber of carbon deposits, helping to
maintain efficiency. In many European countries, a 5% biodiesel blend
is widely used and is available at thousands of gas stations.
In the USA, more than 80% of commercial trucks and city buses run on diesel. The emerging US biodiesel market is estimated to have grown 200% from 2004 to 2005. "By the end of 2006 biodiesel production was estimated to increase fourfold to more than" 1 billion US gallons (3,800,000 m3).
In France, biodiesel is incorporated at a rate of 8% in the fuel used
by all French diesel vehicles.
Avril Group produces under the brand
Diester , a fifth of 11 million tons of biodiesel consumed annually by
9OH) 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. Butanol will
produce more energy and allegedly can be burned "straight" in existing
gasoline engines (without modification to the engine or car), and is
less corrosive and less water-soluble than ethanol, and could be
distributed via existing infrastructures.
Green diesel is produced through hydrocracking biological oil
feedstocks, such as vegetable oils and animal fats.
a refinery method that uses elevated temperatures and pressure in the
presence of a catalyst to break down larger molecules , such as those
found in vegetable oils , into shorter hydrocarbon chains used in
diesel engines. It may also be called renewable diesel, hydrotreated
vegetable oil or hydrogen-derived renewable diesel. Green diesel has
the same chemical properties as petroleum-based diesel. It does not
require new engines, pipelines or infrastructure to distribute and
use, but has not been produced at a cost that is competitive with
In 2013 UK researchers developed a genetically modified strain of
Escherichia coli (
Filtered waste vegetable oil
Walmart 's truck fleet logs
millions of miles each year, and the company planned to double the
fleet's efficiency between 2005 and 2015. This truck is one of 15
based at Walmart's
Buckeye, Arizona distribution center that was
converted to run on a biofuel made from reclaimed cooking grease
produced during food preparation at
Walmart stores. Main article:
Straight unmodified edible vegetable oil is generally not used as fuel, but lower-quality oil has been used for this purpose. Used vegetable oil is increasingly being processed into biodiesel, or (more rarely) cleaned of water and particulates and then used as a fuel.
As with 100% biodiesel (B100), to ensure the fuel injectors atomize the vegetable oil in the correct pattern for efficient combustion, vegetable oil fuel must be heated to reduce its viscosity to that of diesel, either by electric coils or heat exchangers. This is easier in warm or temperate climates. MAN B"> Pipes carrying biogas Main article: Biogas
Biogas is methane 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 be used as a biofuel or a fertilizer.
Biogas can be recovered from mechanical biological treatment waste processing systems. Landfill gas , a less clean form of biogas, is produced in landfills through naturally occurring anaerobic digestion. If it escapes into the atmosphere, it is a potential greenhouse gas .
Farmers can produce biogas from manure from their cattle by using anaerobic digesters.
Main article: Gasification
Syngas , a mixture of carbon monoxide , hydrogen and other hydrocarbons, is produced by partial combustion of biomass, that is, combustion with an amount of oxygen that is not sufficient to convert the biomass completely to carbon dioxide and water. Before partial combustion, the biomass is dried, and sometimes pyrolysed . The resulting gas mixture, syngas, is more efficient than direct combustion of the original biofuel; more of the energy contained in the fuel is extracted.
Syngas may be burned directly in internal combustion engines, turbines or high-temperature fuel cells. The wood gas generator , a wood-fueled gasification reactor, can be connected to an internal combustion engine.
Syngas can be used to produce methanol , DME and hydrogen , or converted via the Fischer-Tropsch process to produce a diesel substitute, or a mixture of alcohols that can be blended into gasoline. Gasification normally relies on temperatures greater than 700 °C.
Lower-temperature gasification is desirable when co-producing biochar , but results in syngas polluted with tar .
SOLID BIOMASS FUELS
Examples include wood , sawdust , grass trimmings, domestic refuse , charcoal , agricultural waste , nonfood energy crops , and dried manure .
When solid biomass is already in a suitable form (such as firewood ), it can burn directly in a stove or furnace to provide heat or raise steam. When solid biomass is in an inconvenient form (such as sawdust, wood chips, grass, urban waste wood, agricultural residues), the typical process is to densify the biomass. This process includes grinding the raw biomass to an appropriate particulate size (known as hogfuel), which, depending on the densification type, can be from 1 to 3 cm (0.4 to 1.2 in), which is then concentrated into a fuel product. The current processes produce wood pellets , cubes, or pucks. The pellet process is most common in Europe, and is typically a pure wood product. The other types of densification are larger in size compared to a pellet and are compatible with a broad range of input feedstocks. The resulting densified fuel is easier to transport and feed into thermal generation systems, such as boilers.
Sawdust, bark and chips are already used for decades for fuel in industrial processes; examples include the pulp and paper industry and the sugar cane industry. Boilers in the range of 500,000 lb/hr of steam, and larger, are in routine operation, using grate, spreader stoker, suspension burning and fluid bed combustion. Utilities generate power, typically in the range of 5 to 50 MW, using locally available fuel. Other industries have also installed wood waste fueled boilers and dryers in areas with low-cost fuel.
One of the advantages of solid biomass fuel is that it is often a byproduct, residue or waste-product of other processes, such as farming, animal husbandry and forestry. In theory, this means fuel and food production do not compete for resources, although this is not always the case.
A problem with the combustion of solid biomass fuels is that it emits considerable amounts of pollutants , such as particulates and polycyclic aromatic hydrocarbons . Even modern pellet boilers generate much more pollutants than oil or natural gas boilers. Pellets made from agricultural residues are usually worse than wood pellets, producing much larger emissions of dioxins and chlorophenols .
A derived fuel is biochar , which is produced by biomass pyrolysis .
BIOFUELS BY REGION
Biofuels by region See also:
There are international organizations such as IEA Bioenergy,
established in 1978 by the
Biofuels currently make up 3.1% of the total road transport fuel in the UK or 1,440 million litres. By 2020, 10% of the energy used in UK road and rail transport must come from renewable sources – this is the equivalent of replacing 4.3 million tonnes of fossil oil each year. Conventional biofuels are likely to produce between 3.7 and 6.6% of the energy needed in road and rail transport, while advanced biofuels could meet up to 4.3% of the UK's renewable transport fuel target by 2020.
Main articles: Biomass § Environmental damage , and Ethanol_fuel § Air_pollution
Biofuels are different from fossil fuels in regard to greenhouse
gases but are similar to fossil fuels in that biofuels contribute to
air pollution . Burning produces airborne carbon particulates , carbon
monoxide and nitrous oxides . The WHO estimates 3.7 million premature
deaths worldwide in 2012 due to air pollution.
DEBATES REGARDING THE PRODUCTION AND USE OF BIOFUEL
Main article: Issues relating to biofuels
There are various social, economic, environmental and technical issues with biofuel production and use, which have been discussed in the popular media and scientific journals. These include: the effect of moderating oil prices , the "food vs fuel " debate, food prices , poverty reduction potential, energy ratio , energy requirements , carbon emissions levels, sustainable biofuel production, deforestation and soil erosion , loss of biodiversity , impact on water resources , the possible modifications necessary to run the engine on biofuel, as well as energy balance and efficiency. The International Resource Panel , which provides independent scientific assessments and expert advice on a variety of resource-related themes, assessed the issues relating to biofuel use in its first report Towards sustainable production and use of resources: Assessing Biofuels. "Assessing Biofuels" outlined the wider and interrelated factors that need to be considered when deciding on the relative merits of pursuing one biofuel over another. It concluded that not all biofuels perform equally in terms of their impact on climate, energy security and ecosystems, and suggested that environmental and social impacts need to be assessed throughout the entire life-cycle.
Another issue with biofuel use and production is the US has changed
mandates many times because the production has been taking longer than
expected. The Renewable
Main article: Sustainable biofuels
Biofuels in the form of liquid fuels derived from plant materials are entering the market, driven mainly by the perception that they reduce climate gas emissions, and also by factors such as oil price spikes and the need for increased energy security . However, many of the biofuels that were being supplied in 2008 (using the first-generation biofuel production procedure) have been criticised for their adverse impacts on the natural environment , food security , and land use . In 2008, the Nobel-prize winning chemist Paul J. Crutzen published findings that the release of nitrous oxide (N2O) emissions in the production of biofuels means that overall they contribute more to global warming than the fossil fuels they replace.
The challenge back then was to support biofuel development, including the development of new cellulosic technologies , with responsible policies and economic instruments to help ensure that biofuel commercialization is sustainable . Responsible commercialization of biofuels represents an opportunity to enhance sustainable economic prospects in Africa, Latin America and Asia.
According to the Rocky Mountain Institute , sound biofuel production practices would not hamper food and fibre production, nor cause water or environmental problems, and would enhance soil fertility. The selection of land on which to grow the feedstocks is a critical component of the ability of biofuels to deliver sustainable solutions. A key consideration is the minimisation of biofuel competition for prime cropland.
GREENHOUSE GAS EMISSIONS
Some scientists have expressed concerns about land-use change in response to greater demand for crops to use for biofuel and the subsequent carbon emissions. The payback period, that is, the time it will take biofuels to pay back the carbon debt they acquire due to land-use change, has been estimated to be between 100 and 1000 years, depending on the specific instance and location of land-use change. However, no-till practices combined with cover-crop practices can reduce the payback period to three years for grassland conversion and 14 years for forest conversion.
A study conducted in the Tocantis State, in northern Brazil, found that many families were cutting down forests in order to produce two conglomerates of oilseed plants, the J. curcas (JC group) and the R. communis (RC group). This region is composed of 15% Amazonian rainforest with high biodiversity, and 80% Cerrado forest with lower biodiversity. During the study, the farmers that planted the JC group released over 2193 Mg CO2, while losing 53-105 Mg CO2 sequestration from deforestation; and the RC group farmers released 562 Mg CO2, while losing 48-90 Mg CO2 to be sequestered from forest depletion. The production of these types of biofuels not only led into an increased emission of carbon dioxide, but also to lower efficiency of forests to absorb the gases that these farms were emitting. This has to do with the amount of fossil fuel the production of fuel crops involves. In addition, the intensive use of monocropping agriculture requires large amounts of water irrigation, as well as of fertilizers, herbicides and pesticides. This does not only lead to poisonous chemicals to disperse on water runoff, but also to the emission of nitrous oxide (NO2) as a fertilizer byproduct, which is three hundred times more efficient in producing a greenhouse effect than carbon dioxide (CO2).
Converting rainforests, peatlands, savannas, or grasslands to produce food crop–based biofuels in Brazil, Southeast Asia, and the United States creates a “biofuel carbon debt” by releasing 17 to 420 times more CO2 than the annual greenhouse gas (GHG) reductions that these biofuels would provide by displacing fossil fuels. Biofuels made from waste biomass or from biomass grown on abandoned agricultural lands incur little to no carbon debt.
In addition to crop growth requiring water, biofuel facilities require significant process water.
Research is ongoing into finding more suitable biofuel crops and improving the oil yields of these crops. Using the current yields, vast amounts of land and fresh water would be needed to produce enough oil to completely replace fossil fuel usage. It would require twice the land area of the US to be devoted to soybean production, or two-thirds to be devoted to rapeseed production, to meet current US heating and transportation needs.
Specially bred mustard varieties can produce reasonably high oil yields and are very useful in crop rotation with cereals, and have the added benefit that the meal left over after the oil has been pressed out can act as an effective and biodegradable pesticide.
NFESC , with Santa Barbara -based
ETHANOL BIOFUELS (BIOETHANOL)
As the primary source of biofuels in North America, many
organizations are conducting research in the area of ethanol
production. The National Corn-to-
As of 2013, the first commercial-scale plants to produce cellulosic biofuels have begun operating. Multiple pathways for the conversion of different biofuel feedstocks are being used. In the next few years, the cost data of these technologies operating at commercial scale, and their relative performance, will become available. Lessons learnt will lower the costs of the industrial processes involved.
In parts of Asia and Africa where drylands prevail, sweet sorghum is
being investigated as a potential source of food, feed and fuel
combined. The crop is particularly suitable for growing in arid
conditions, as it only extracts one seventh of the water used by
A study by researchers at the International Crops Research Institute
for the Semi-Arid Tropics (
Main article: Jatropha biofuel
Several groups in various sectors are conducting research on Jatropha curcas , a poisonous shrub-like tree that produces seeds considered by many to be a viable source of biofuels feedstock oil. Much of this research focuses on improving the overall per acre oil yield of Jatropha through advancements in genetics, soil science, and horticultural practices.
SG Biofuels , a San Diego-based jatropha developer, has used molecular breeding and biotechnology to produce elite hybrid seeds that show significant yield improvements over first-generation varieties. SG Biofuels also claims additional benefits have arisen from such strains, including improved flowering synchronicity, higher resistance to pests and diseases, and increased cold-weather tolerance.
Plant Research International, a department of the Wageningen
University and Research Centre in the Netherlands, maintains an
ongoing Jatropha Evaluation Project that examines the feasibility of
large-scale jatropha cultivation through field and laboratory
experiments. The Center for
A group at the
Russian Academy of Sciences in
ANIMAL GUT BACTERIA
Microbial gastrointestinal flora in a variety of animals have shown potential for the production of biofuels. Recent research has shown that TU-103, a strain of Clostridium bacteria found in Zebra feces, can convert nearly any form of cellulose into butanol fuel. Microbes in panda waste are being investigated for their use in creating biofuels from bamboo and other plant materials. There has also been substantial research into the technology of using the gut microbiomes of wood-feeding insects for the conversion of lignocellulotic material into biofuel.
PORTALS Access related topics
* RENEWABLE ENERGY PORTAL * ENERGY PORTAL * SUSTAINABLE DEVELOPMENT PORTAL * ECOLOGY PORTAL
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