The International Energy Agency want biofuels to meet more than a quarter of world demand for transportation fuels by , in order to reduce dependency on petroleum. 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.
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 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. 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.
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. 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 [15] and photobiological solar fuels. 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 is methane produced by the process of anaerobic digestion of organic material by anaerobes.
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, 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.
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. 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.
Lower-temperature gasification is desirable when co-producing biochar, but results in syngas polluted with tar.
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.
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 [36] — 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. 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 3 CH 2 OH 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 [37] 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, [38] the fossil energy ratios FER for cellulosic ethanol, corn ethanol, and gasoline are 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. With current subsidies, ethanol fuel is slightly cheaper per distance traveled in the United States. 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 that the economic viability is still pending.
Butanol C 4 H 9 OH 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 , [43] 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.
Biodiesel is the most common biofuel in Europe. 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.
Biodiesel can be used in any diesel engine when mixed with mineral diesel. It can also be used in its pure form B 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 most cases, biodiesel is compatible with diesel engines from 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 , 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 s 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 B 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. This improves the combustion of biodiesel and reduces the particulate emissions from unburnt carbon. However, using pure biodiesel may increase NO x -emissions [50]. Green diesel is produced through hydrocracking biological oil feedstocks, such as vegetable oils and animal fats. 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. This is easier in warm or temperate climates. 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 also referred to as fuel ethers or oxygenated fuels are cost-effective compounds that act as octane rating enhancers.
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. Ethers were introduced in Europe in the s to replace the highly toxic compound. There are international organizations such as IEA Bioenergy, [71] established in by the OECDInternational Energy Agency IEA , with the aim of improving cooperation and information exchange between countries that have national programs in bioenergy research, development and deployment.
In , 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. Requirements and additional information:. Antony Peel. Software languages. Author Scott Cawthon. Updated Over a year ago. Last revision More than a year ago. Hello Neighbor. Watch Dogs 2. Ok We use our own and third-party cookies for advertising, session, analytic, and social network purposes.
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