A bus fueled by biodiesel
Information on pump regarding ethanol fuel blend up to 10%, California
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. If the
source biomatter can regrow quickly, the resulting fuel is said to be a
form of renewable energy.
Biofuels can be derived directly from plants (i.e. energy crops), 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.
Biofuels are in theory carbon-neutral
because the carbon dioxide that is absorbed by the plants is equal to
the carbon dioxide that is released when the fuel is burned.
However, in practice, whether or not a biofuel is carbon-neutral also
depends greatly on whether the land which is used to grow the biofuel
(with 1st and 2nd generation biofuel) needed to be cleared of carbon-holding vegetation or not..
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. Ethanol can be used as a fuel for vehicles in its pure form (E100), but it is usually used as a gasoline additive to increase octane and improve vehicle emissions. Bioethanol is widely used in the United States and in Brazil. Current plant design does not provide for converting the lignin portion of plant raw materials to fuel components by fermentation.
Biodiesel can be used as a fuel for vehicles in its pure form (B100), but it is usually used as a diesel additive to reduce levels of particulates, carbon monoxide, and hydrocarbons from diesel-powered vehicles. Biodiesel is produced from oils or fats using transesterification and is the most common biofuel in Europe.
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 United States and Brazil as the world's top producers,
accounting together for about 90% of global production. The world's
largest biodiesel producer is the European Union, accounting for 53% of all biodiesel production in 2010. As of 2011, mandates for blending biofuels exist in 31 countries at the national level and in 29 states or provinces. The International Energy Agency
has a goal for biofuels to meet more than a quarter of world demand for
transportation fuels by 2050 to reduce dependence on petroleum and
coal.
The production of biofuels also led into a flourishing automotive
industry, where by 2010, 79% of all cars produced in Brazil were made
with a hybrid fuel system of bioethanol and gasoline.
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.
Generations
First-generation biofuels
"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.
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 that have already fulfilled their food purpose). The feedstock used to generate second-generation biofuels thus either grows on arable lands,
but are just byproducts of the actual harvest (main crop) or they are
grown on lands which cannot be used to effectively grow food crops
and in some cases neither extra water or fertilizer is applied to them.
Non-human food second generation feedstock sources include grasses,
jatropha and other seed crops, waste vegetable oil, municipal solid
waste and so forth.
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.
Third-generation biofuels
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.
Fourth-generation biofuels
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.
Types
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.
Biogas
Pipes carrying 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.
Syngas
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.
Ethanol
Neat ethanol on the left (A), gasoline on the right (G) at a filling station in Brazil
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 looks at sugar cane, a source of biofuel, with Brazilian President Luiz Inácio Lula da Silva during a tour on biofuel technology at Petrobras in São Paulo, Brazil, 9 March 2007.
Ethanol fuel is the most common biofuel worldwide, particularly in Brazil. Alcohol fuels are produced by fermentation of sugars derived from wheat, corn, sugar beets, sugar cane, molasses and any sugar or starch from which alcoholic beverages such as whiskey, can be made (such as potato and fruit waste, etc.). The ethanol production methods used are enzyme digestion (to release sugars from stored starches), fermentation of the sugars, distillation and drying. The distillation process requires significant energy input for heat (sometimes unsustainable natural gas fossil fuel, but cellulosic biomass such as bagasse,
the waste left after sugar cane is pressed to extract its juice, is the
most common fuel in Brazil, while pellets, wood chips and also waste heat are more common in Europe) Waste steam fuels ethanol factory – where waste heat from the factories also is used in the district heating grid.
Ethanol can be used in petrol engines as a replacement for
gasoline; it can be mixed with gasoline to any percentage. Most existing
car petrol engines can run on blends of up to 15% bioethanol with
petroleum/gasoline. Ethanol has a smaller energy density
than that of gasoline; this means it takes more fuel (volume and mass)
to produce the same amount of work. An advantage of ethanol (CH
3CH
2OH) is that it has a higher octane rating than ethanol-free gasoline available at roadside gas stations, which allows an increase of an engine's compression ratio for increased thermal efficiency. In high-altitude (thin air) locations, some states mandate a mix of gasoline and ethanol as a winter oxidizer to reduce atmospheric pollution emissions.
3CH
2OH) is that it has a higher octane rating than ethanol-free gasoline available at roadside gas stations, which allows an increase of an engine's compression ratio for increased thermal efficiency. In high-altitude (thin air) locations, some states mandate a mix of gasoline and ethanol as a winter oxidizer to reduce atmospheric pollution emissions.
Ethanol is also used to fuel bioethanol fireplaces. As they do not require a chimney and are "flueless", bioethanol fires
are extremely useful for newly built homes and apartments without a
flue.
The downsides to these fireplaces is that their heat output is slightly
less than electric heat or gas fires, and precautions must be taken to
avoid carbon monoxide poisoning.
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.
Ethanol has roughly one-third lower energy content per unit of
volume compared to gasoline. This is partly counteracted by the better
efficiency when using ethanol (in a long-term test of more than 2.1
million km, the BEST project found FFV vehicles to be 1–26% more energy
efficient than petrol cars, but the volumetric consumption increases by
approximately 30%, so more fuel stops are required).
With current subsidies, ethanol fuel is slightly cheaper per distance traveled in the United States.
Other bioalcohols
Methanol is currently produced from natural gas, a non-renewable fossil fuel. In the future it is hoped to be produced from biomass as biomethanol. This is technically feasible, but the production is currently being postponed for concerns of Jacob S. Gibbs and Brinsley Coleberd that the economic viability is still pending. The methanol economy is an alternative to the hydrogen economy, compared to today's hydrogen production from natural gas.
Butanol (C
4H
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. DuPont and BP are working together to help develop butanol. Escherichia coli strains have also been successfully engineered to produce butanol by modifying their amino acid metabolism. One drawback to butanol production in E. coli remains the high cost of nutrient rich media, however, recent work has demonstrated E. coli can produce butanol with minimal nutritional supplementation.
4H
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. DuPont and BP are working together to help develop butanol. Escherichia coli strains have also been successfully engineered to produce butanol by modifying their amino acid metabolism. One drawback to butanol production in E. coli remains the high cost of nutrient rich media, however, recent work has demonstrated E. coli can produce butanol with minimal nutritional supplementation.
Biodiesel
Biodiesel is the most common biofuel in Europe. It is produced from oils or fats using transesterification
and is a liquid similar in composition to fossil/mineral diesel.
Chemically, it consists mostly of fatty acid methyl (or ethyl) esters (FAMEs). Feedstocks for biodiesel include animal fats, vegetable oils, soy, rapeseed, jatropha, mahua, mustard, flax, sunflower, palm oil, hemp, field pennycress, Pongamia pinnata and algae.
Pure biodiesel (B100, also known as "neat" biodiesel) currently reduces
emissions with up to 60% compared to diesel Second generation B100.
Targray Biofuels Division railcar transporting Biodiesel.
Biodiesel can be used in any diesel engine
when mixed with mineral diesel. It can also be used in its pure form
(B100) in diesel engines, but some maintenance and performance problems
may then occur during wintertime utilization, since the fuel becomes
somewhat more viscous at lower temperatures, depending on the feedstock used. In some countries, manufacturers cover their diesel engines under warranty for B100 use, although Volkswagen of Germany,
for example, asks drivers to check by telephone with the VW
environmental services department before switching to B100. In most
cases, biodiesel is compatible with diesel engines from 1994 onwards,
which use 'Viton' (by DuPont) synthetic rubber in their mechanical fuel injection
systems. Note however, that no vehicles are certified for using pure
biodiesel before 2014, as there was no emission control protocol
available for biodiesel before this date.
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. Biodiesel is also an oxygenated fuel, meaning it contains a reduced amount of carbon and higher hydrogen and oxygen content than fossil diesel. This improves the combustion of biodiesel and reduces the particulate emissions from unburnt carbon. However, using pure biodiesel may increase NOx-emissions.
Biodiesel is also safe to handle and transport because it is non-toxic and biodegradable, and has a high flash point of about 300 °F (148 °C) compared to petroleum diesel fuel, which has a flash point of 125 °F (52 °C).
In the US, 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 [from 2004] 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 the European Union. It is the leading European producer of biodiesel.
Green diesel
Green diesel is produced through hydrocracking biological oil feedstocks, such as vegetable oils and animal fats.
Hydrocracking is 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. Unlike biodiesel, green diesel has exactly 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 petroleum. Gasoline versions are also being developed. Green diesel is being developed in Louisiana and Singapore by ConocoPhillips, Neste Oil, Valero, Dynamic Fuels, and Honeywell UOP as well as Preem in Gothenburg, Sweden, creating what is known as Evolution Diesel.
Straight vegetable oil
Filtered waste vegetable oil
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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.
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&W Diesel, Wärtsilä, and Deutz AG, as well as a number of smaller companies, such as Elsbett, offer engines that are compatible with straight vegetable oil, without the need for after-market modifications.
Vegetable oil can also be used in many older diesel engines that do not use common rail or unit injection electronic diesel injection systems. Due to the design of the combustion chambers in indirect injection
engines, these are the best engines for use with vegetable oil. This
system allows the relatively larger oil molecules more time to burn.
Some older engines, especially Mercedes, are driven experimentally by
enthusiasts without any conversion, a handful of drivers have
experienced limited success with earlier pre-"Pumpe Duse" VW TDI engines and other similar engines with direct injection. Several companies, such as Elsbett or Wolf, have developed professional conversion kits and successfully installed hundreds of them over the last decades.
Oils and fats can be hydrogenated to give a diesel substitute. The resulting product is a straight-chain hydrocarbon with a high cetane number, low in aromatics and sulfur and does not contain oxygen. Hydrogenated oils
can be blended with diesel in all proportions. They have several
advantages over biodiesel, including good performance at low
temperatures, no storage stability problems and no susceptibility to
microbial attack.
Bioethers
Bioethers (also referred to as fuel ethers or oxygenated fuels) are cost-effective compounds that act as octane rating enhancers."Bioethers are produced by the reaction of reactive iso-olefins, such as iso-butylene, with bioethanol." Bioethers are created by wheat or sugar beet. They also enhance engine performance, while significantly reducing engine wear and toxic exhaust emissions.
Although bioethers are likely to replace petroethers in the UK, it is
highly unlikely they will become a fuel in and of itself due to the low
energy density. Greatly reducing the amount of ground-level ozone emissions, they contribute to air quality.
When it comes to transportation fuel there are six ether additives: dimethyl ether (DME), diethyl ether (DEE), methyl teritiary-butyl ether (MTBE), ethyl ter-butyl ether (ETBE), ter-amyl methyl ether (TAME), and ter-amyl ethyl ether (TAEE).
The European Fuel Oxygenates Association (EFOA) credits methyl
Ttertiary-butyl ether (MTBE) and ethyl ter-butyl ether (ETBE) as the
most commonly used ethers in fuel to replace lead. Ethers were
introduced in Europe in the 1970s to replace the highly toxic compound.
Although Europeans still use bio-ether additives, the US no longer has
an oxygenate requirement therefore bio-ethers are no longer used as the
main fuel additive.
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.
Biochar made from agricultural waste can substitute for wood charcoal.
As wood stock becomes scarce, this alternative is gaining ground. In
eastern Democratic Republic of Congo, for example, biomass briquettes are being marketed as an alternative to charcoal to protect Virunga National Park from deforestation associated with charcoal production.
By region
Bio Diesel Powered Fast Attack Craft Of Indian Navy patrolling during IFR 2016. The green bands on the side of the vessel are indicative of the fact that the vessel is powered by bio-diesel.
There are international organizations such as IEA Bioenergy, established in 1978 by the OECD 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 UN International Biofuels Forum is formed by Brazil, China, India, Pakistan, South Africa, the United States and the European Commission.
The world leaders in biofuel development and use are Brazil, the United
States, France, Sweden and Germany. Russia also has 22% of world's
forest,
and is a big biomass (solid biofuels) supplier. In 2010, Russian pulp
and paper maker, Vyborgskaya Cellulose, said they would be producing
pellets that can be used in heat and electricity generation from its
plant in Vyborg by the end of the year. The plant will eventually produce about 900,000 tons of pellets per year, making it the largest in the world once operational.
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.
Air pollution
Biofuels are similar to fossil fuels in that biofuels contribute to air pollution. Burning produces carbon dioxide, airborne carbon particulates, carbon monoxide and nitrous oxides. The WHO estimates 3.7 million premature deaths worldwide in 2012 due to air pollution. Brazil burns significant amounts of ethanol biofuel. Gas chromatograph
studies were performed of ambient air in São Paulo, Brazil, and
compared to Osaka, Japan, which does not burn ethanol fuel. Atmospheric
Formaldehyde was 160% higher in Brazil, and Acetaldehyde was 260%
higher.
The Environmental Protection Agency has acknowledged in April
2007 that the increased use of bio-ethanol will lead to worse air
quality. The total emissions of air pollutants such as nitrogen oxides
will rise due the growing use of bio-ethanol. There is an increase in
carbon dioxide from the burning of fossil fuels to produce the biofuels
as well as nitrous oxide from the soil, which has most likely been
treated with nitrogen fertilizer. Nitrous oxide is known to have a
greater impact on the atmosphere in relation to global warming, as it is
also an ozone destroyer.
Debates regarding the production and use of biofuel
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 Fuel Standard (RFS) set by congress
for 2010 was pushed back to at best 2012 to produce 100 million gallons
of pure ethanol (not blended with a fossil fuel).
Banning of first-generation biofuels
In
the EU, the revised renewable energy directive calls for a complete ban
on first-generation biofuels by 2030. Particularly fuels made from such
oils such as palm oil and soy oil are being targeted.
Sustainable biofuels
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.
In 2008, the challenge 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 represented an opportunity to
enhance sustainable economic prospects in Africa, Latin America and
Asia.
Now, biofuels in the form of liquid fuels
derived from plant materials are entering the market, driven 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.
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.
Water Use
In addition to crop growth requiring water, biofuel facilities require significant process water.
Forests and Carbon Sequestration
Scientific
research (20th century) shows that carbon dioxide emissions from all
forms of surface transport are converted in a few weeks by forests,
farms and oceans into biomass. This implies that a greater emphasis on
sustainable forestry is very relevant for climate protection and
sustainable, energy-efficient transport.
Current research
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.
The NFESC, with Santa Barbara-based
Biodiesel Industries, is working to develop biofuels technologies for
the US navy and military, one of the largest diesel fuel users in the
world.
A group of Spanish developers working for a company called Ecofasa
announced a new biofuel made from trash. The fuel is created from
general urban waste which is treated by bacteria to produce fatty acids,
which can be used to make biofuels. Before its shutdown, Joule Unlimited was attempting to make cheap ethanol and biodiesel from a genetically modified photosynthetic bacterium.
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-Ethanol Research Center (NCERC) is a research division of Southern Illinois University Edwardsville dedicated solely to ethanol-based biofuel research projects.
On the federal level, the USDA
conducts a large amount of research regarding ethanol production in the
United States. Much of this research is targeted toward the effect of
ethanol production on domestic food markets. A division of the U.S. Department of Energy, the National Renewable Energy Laboratory (NREL), has also conducted various ethanol research projects, mainly in the area of cellulosic ethanol.
Cellulosic ethanol commercialization
is the process of building an industry out of methods of turning
cellulose-containing organic matter into fuel. Companies, such as Iogen, POET, and Abengoa, are building refineries that can process biomass and turn it into bioethanol. Companies, such as Diversa, Novozymes, and Dyadic, are producing enzymes that could enable a cellulosic ethanol
future. The shift from food crop feedstocks to waste residues and
native grasses offers significant opportunities for a range of players,
from farmers to biotechnology firms, and from project developers to
investors.
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
sugarcane. In India, and other places, sweet sorghum stalks are used to produce biofuel by squeezing the juice and then fermenting into ethanol.
A study by researchers at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT)
found that growing sweet sorghum instead of grain sorghum could
increase farmers incomes by US$40 per hectare per crop because it can
provide fuel in addition to food and animal feed. With grain sorghum
currently grown on over 11 million hectares (ha) in Asia and on 23.4
million ha in Africa, a switch to sweet sorghum could have a
considerable economic impact.
Jatropha
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 Sustainable Energy Farming (CfSEF) is a Los Angeles-based
nonprofit research organization dedicated to jatropha research in the
areas of plant science, agronomy, and horticulture. Successful
exploration of these disciplines is projected to increase jatropha farm
production yields by 200-300% in the next 10 years.
Fungi
A group at the Russian Academy of Sciences in Moscow,
in a 2008 paper, stated they had isolated large amounts of lipids from
single-celled fungi and turned it into biofuels in an economically
efficient manner. More research on this fungal species, Cunninghamella japonica, and others, is likely to appear in the near future.
The recent discovery of a variant of the fungus Gliocladium roseum (later renamed Ascocoryne sarcoides) points toward the production of so-called myco-diesel from cellulose. This organism was recently discovered in the rainforests of northern Patagonia, and has the unique capability of converting cellulose into medium-length hydrocarbons typically found in diesel fuel.
Many other fungi that can degrade cellulose and other polymers have
been observed to produce molecules that are currently being engineered
using organisms from other kingdoms, suggesting that fungi may play a
large role in the bio-production of fuels in the future (reviewed 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.
