Biomass was the first fuel that mankind learned to use for energy through the burning of wood for warmth and cooking. Biomass is the waste of recently living orgasms including both animals, as well as plants. Biomass is carbon-cycle based renewable energy source. The term ‘biomass’ covers all plant and animal matter on the Earth’s surface. Heat, electricity, or automotive energy generated from crops, trees, or agricultural waste, is referred to as ‘bioenergy’.Biomass is a sustainable resource that it is constantly being formed by the interaction of air, water, soil and sunlight. If biomass is not used for chemical or energy purposes, it is broken down again by microorganisms into its elementary constituent parts: water, CO2 and energy in the form of heat. There are almost no limits on how much biomass can be grown. The continuous growth of plants on our planet exceeds our primary energy requirements many times over.
Bioenergy, produced through Biomass is amongst the world’s most important renewable energy sources, generating heat and electricity for various applications at different scales.
The Net Primary Production, i.e. the radiation energy emanating from the sun that is biologically absorbed in biomass amounts to approximately 50 billion t of crude oil equivalent units every year. Compare this with mankind’s current primary energy requirements of approximately 9.7 billion t of crude oil equivalent units every year. Of course, only part of the biomass that grows can actually be supplied for energy use, both for ecological, technical and economic reasons. Yet there remains a huge amount of biomass that is very suitable for exploitation.
Biofuels can be originated from dead biological materials. Biofuels are found in the form of solid, liquid or gas. These are derived from photosynthetic plant. Biofuel is any fuel that derives from biomass i.e. recently living organisms or their metabolic byproducts. Thus it could be oils from plants, manure from cows, wood from trees and so on. It is a renewable energy source unlike other natural resources such as petroleum, coal and nuclear fuels.The most important fact about Biofuels is that Biofuels increases energy security by reducing dependence on petroleum. These offer the possibility of producing energy without a net increase of carbon into the atmosphere because the plants used in to produce the fuel have removed CO2 from the atmosphere, unlike fossil fuels which return carbon which was stored beneath the surface for millions of years into the air. Thus these are more nearly carbon neutral and less likely increase atmospheric concentrations of greenhouse gases.
Agricultural products specifically grown for use as biofuels include corn and soybeans, primarily in the United States, and flaxseed and rapeseed, primarily in Europe. Waste from industry, agriculture, forestry, and households can also be used to produce bioenergy; i.e. manure, straw, sewage, lumber, garbage and food leftovers. There are many ways of producing biofuels, but two ways are most commonly approached. These are :
1. To grow crops high in either sugar (sugar cane, sugar beet, and sweet sorghum) or starch (corn/maize), and then use yeast fermentation to produce ethyl alcohol i.e. “ethanol”.
2. To grow plants containing high amounts of vegetable oil, such as oil palm, soybean, algae, or jatropha. When these oils are heated, their viscosity is reduced, and they can be burned directly in a diesel engine, or the oils can be chemically processed to produce fuels such as biodiesel.
Wood and its byproducts can also be converted into biofuels such as woodgas, methanol or ethanol fuel. Cellulosic ethanol from can be made from non-edible plant parts, but it is rather a difficult, as well as expendible process. The production of biofuels to replace petroleum-based oil and natural gas is in active development. The carbon in biofuels was recently extracted from atmospheric carbon dioxide by growing plants, so burning it does not result in a net increase of carbon dioxide in the Earth’s atmosphere. As a result, biofuels are seen by many as a way to reduce the amount of carbon dioxide released into the atmosphere by using them to replace non-renewable sources of energy.
Kinds Of Biofuels
Many kinds of Biofuels can be produced through Biomass as Biomass is the most important biological energy resource. Some of these are :
Hydrogen gas is an interesting alternative fuel because it completely eliminates carbon as an energy carrier.Therefore it obviously cannot contribute to the green house effect. Although hydrogen is currently being produced by either thermally decomposing natural gas or by electrolysis of water there is also a potential for biological hydrogen production. Some microorganisms produce hydrogen naturally, and biotechnologies based on these microbial systems could lead to the development of clean, renewable sources of hydrogen. Biohydrogen is hydrogen produced via biological processes or from
biomass The enzyme which is responsible for the production of hydrogen, hydrogenase, however is extremely sensitive to oxygen so that hydrogen is only produced in anaerobic habitats. Biohydrogen plants are proposed industrial plants for the production of hydrogen, such as “Algae”. Algae grows prolifically in adverse conditions, and can store large amounts of oils or starches useful for making biodiesel or ethanol. But some strains also use an enzyme called hydrogenase to produce small amounts of hydrogen gas. Scientists think this is the organism’s way of getting rid of excess energy under high-light conditions.They would typically involve processes such as thermophillic fermentation, photofermentation and gas cleaning. Hydrogen can be produced by bacterial species such as Rhodobacter sphaeroides and Enterobacter cloacae. Biohydrogen can be produced through dark fermentation either by mix culture of hydrogen producing sludge or pure culture of anaerobic bacteria such as Clostridium butyricum.
Bioethanol and biodiesel are interesting because they can be directly used in an existing technology, the internal combustion engine, hydrogen has the potential to be used in a far more efficient way in the hydrogen fuel cell. In a conventional engine all the energy is released in an explosive way by burning. In a fuel cell however the oxidation is accomplished in steps at an electrode in a process which closely resembles the functioning of an everyday battery. In this process the energy is not explosively released as heat but produces an electric current with high efficiency which can be used to run an electric engine. However because hydrogen is one of the smallest molecules known a number of engineering problems arise with storing and transporting it. Because it is a gas it takes up a greater volume than an equivalent bioethanol or biodiesel. Although it can be adsorbed by certain metals, these metals themselves like platinum are toxic and prohibitively expensive for large scale use. It represents a bigger danger for explosions and because of its small size it can get lodged in crystal defects in the metal pipes through which it is conducted making them brittle.
Biodiesel is a natural and renewable domestic fuel alternative for diesel engines made from vegetable oils, mostly soy and corn. It contains no petroleum, is nontoxic and biodegradable. It is the name of a clean burning alternative fuel, produced from domestic, renewable resources. Biodiesel can be produced from straight vegetable oil, animal oil/fats, tallow and waste cooking oil. The process used to convert these oils to Biodiesel is called transesterification. Biodiesel contains no petroleum, but it can be blended at any level with petroleum diesel to create a biodiesel blend. It can be used in compression-ignition (diesel) engines with little or no modifications. Biodiesel is simple to use, biodegradable, nontoxic, and essentially free of sulfur and aromatics.
Fuel-grade biodiesel must be produced to strict industry specifications (ASTM D6751) in order to insure proper performance. Biodiesel is the only alternative fuel to have fully completed the health effects testing requirements of the 1990 Clean Air Act Amendments. Biodiesel that meets ASTM D6751 and is legally registered with the Environmental Protection Agency is a legal motor fuel for sale and distribution. Raw vegetable oil cannot meet biodiesel fuel specifications, it is not registered with the EPA, and it is not a legal motor fuel. Biodiesel is better for the environment because it is made from renewable resources and has lower emissions compared to petroleum diesel. It is less toxic than table salt and biodegrades as fast as sugar. Since it is made in the USA from renewable resources such as soybeans, its use decreases our dependence on foreign oil and contributes to our own economy. The largest possible source of suitable oil comes from oil crops such as rapeseed, palm or soybean. In the UK rapeseed represents the greatest potential for biodiesel production. Most biodiesel produced at present is produced from waste vegetable oil sourced from restaurants, chip shops, industrial food producers such as Birdseye etc. Though oil straight from the agricultural industry represents the greatest potential source it is not being produced commercially simply because the raw oil is too expensive. After the cost of converting it to biodiesel has been added on it is simply too expensive to compete with fossil diesel. Waste vegetable oil can often be sourced for free or sourced already treated for a small price.
Almost all biodiesel is produced using base catalyzed transesterification as it is the most economical process requiring only low temperatures and pressures and producing a 98% conversion yield. For this reason only this process will be described in this report. The Transesterification process is the reaction of a triglyceride (fat/oil) with an alcohol to form esters and glycerol. A triglyceride has a glycerine molecule as its base with three long chain fatty acids attached. The characteristics of the fat are determined by the nature of the fatty acids attached to the glycerine. The nature of the fatty acids can in turn affect the characteristics of the biodiesel. During the esterification process, the triglyceride is reacted with alcohol in the presence of a catalyst, usually a strong alkaline like sodium hydroxide. The alcohol reacts with the fatty acids to form the mono-alkyl ester, or biodiesel and crude glycerol. In most production methanol or ethanol is the alcohol used (methanol produces methyl esters, ethanol produces ethyl esters) and is base catalysed by either potassium or sodium hydroxide. Potassium hydroxide has been found to be more suitable for the ethyl ester biodiesel production, either base can be used for the methyl ester. A common product of the transesterification process is Rape Methyl Ester (RME) produced from raw rapeseed oil reacted with methanol.
Ethanol is a liquid alcohol made of oxygen, hydrogen and carbon and is obtained from the fermentation of sugar or converted starch contained in grains and other agricultural or agri-forest feedstocks. Ethanol fuel is an alternative fuel to gasoline. Typically, ethanol fuel is made either from a grain such as corn or maize or from sugarcane. Corn is primarily used to make ethanol fuel, while in other generally warmer locations, sugarcane is the preferred source of biomaterial for making ethanol fuel. It is also possible to distill ethanol fuel from petroleum oil, though mention of ethanol fuel usually refers to bio-ethanol. Fuel ethanol, which is sometimes referred to as “gasohol”, has been distilled and dehydrated to create a high-octane, water-free alcohol. All water must be removed because a water-alcohol mixture cannot dissolve in gasoline. Fuel ethanol is made unfit for drinking by adding a small amount of a noxious substance such as gasoline.
Ethanol fuel can be used unmixed in an modified gasoline engine, but it is much more common to find an 85% gasoline and 15% ethanol fuel mixture. This mixture can be used directly in any gasoline engine. This mixture burns cleaner in the engine, causing less pollution. If the ethanol is made from renewable bio-sources, then it also reduces the use of fossil fuels. Ethanol fuel does have a few disadvantages; it has a lower energy density than gasoline, so a tank of ethanol fuel will not go as far as a tank of gasoline, and ethanol fuel can be more difficult to start in very cold temperatures. Some vehicles are specially manufactured to operate on an ethanol blend that contains up to 85 percent ethanol and at least 15 percent gasoline. (The 15 percent gasoline is needed to assist in engine starting because pure ethanol is difficult to ignite in cold weather.) This E-85 blend cannot be used in standard gasoline vehicles, however vehicles designed to run with a high ethanol blend can also operate using gasoline when necessary.
Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naphtha or wood spirits, is a chemical compound with chemical formula CH3OH (often abbreviated MeOH). It is poisonous, flammable and relatively volatile. It has no taste or color, but it does have a slight scent. Methanol is used as a fuel and an antifreeze, and to make formaldehyde. It is also added to ethanol to make it unpalatable so that it avoids taxes on drinkable alcohol, as ethanol without a denaturant of some sort is consumable by humans. Methanol was first discovered in 1661, though it had been used without isolation by peoples as far back as the Egyptians in their embalming processes. The name comes from methy, meaning wine, and hyle, meaning trees.
Methanol has been used for decades in a wide variety of industrial and consumer applications, and has been used as a racing fuel in Indy cars, dragsters and other high power applications. Only recently has methanol been investigated for use in ordinary cars and light trucks, and as a replacement for diesel fuel in heavy-duty trucks and buses. When used in a properly prepared engine, methanol could combust more completely than gasoline. This would result in lower levels of the exhaust emissions that contribute to urban pollution and global warming. Methanol contains no aromatic compounds and therefore produces no benzene emissions. Full analysis of all of the energy and materials required to produce and distribute methanol must be done, however, before the true environmental impact of large scale methanol use can be determined.
Pure methanol is not sold as a stand-alone motor fuel, although in its pure form it is commonly used as racing fuel. As a motor fuel for general transportation it is mixed with gasoline to produce M85 (85% methanol and 15% gasoline). It is also the primary alcohol used to mix biodiesel.