Heat, Power and Biofuels from Biomass Agricultural Sustainable Energy Education Network Renewable Energy Curriculum Introduction Also known as agrofuel Mainly derived from biomass or bio waste These fuels can be used for any purposes, but the main use for which they have to be brought is in the transportation sector. The most important feature of biomass is that they are renewable sources of energy unlike other
natural resources like coal, petroleum and even nuclear fuel. Introduction Today, the use of biofuels has expanded throughout the globe. Some of the major producers and users of biogases are Asia, Europe and America. There are several factors that decide the balance between biofuel and fossil fuel use around the world. Those factors are cost, availability, and food supply . There is only so much land fit for farming in the world and growing biofuels necessarily detracts from the process of growing food. As the population grows,
our demands for both energy and food grow. At this point, we do not have enough land to grow both enough biofuel and enough food to meet both needs. Introduction Some of the agricultural products that are specially grown for the production of biofuels are: United States- switchgrass, soybeans and corn Brazil-sugar cane Europe- sugar beet and wheat China- cassava and sorghum Asia- miscanthus and palm oil
India- jatropha Current Trends Most gasoline and diesel fuels in North America and Europe are blended with biofuel. Biodiesl accounts for about 3% of the German market and 0.15% of the U.S. market. About 1 billion gallons of biodiesel are produced annually. Bioethanol is more popular in the Americas while biodiesel is more popular in Europe. The U.S. and Brazil produce 87% of the world's fuel ethanol. More than 22 billion gallons of fuel ethanol are produced each year. Ethanol is added to gasoline to improve octane and reduce emissions. Biodiesel is added to petroleum-based diesel to reduce emissions and improve engine life. Concerns about the global price of food have resulted in many nations revising
(downward) plans for biofuel production and use. Applications of Biofuels Transportation Leading application because vehicles require clean, dense, high power fuels in a liquid state Liquids can be easily pumped and stored Power Generation solid biomass fuel like wood Heat What is a Biofuel? Biofuel (AKA agrofuel): any fuel whose energy is obtained through a process of
biological carbon fixation Carbon Fixation A chemistry process that converts carbon dioxide into a hydrocarbon molecule (a source of energy) that would be found in a living organism If this process occurs in a living organism, it is referred to as biological carbon fixation A Lesson Learned from Nature Photosynthesis is a biological carbon fixation process utilized by plants to obtain energy in the form of carbohydrates What is Biomass?
Biomass is dead organic matter Examples: kernels of corn, mats of algae, stalks of sugar cane Types of biomass Woody Examples: coconut, oil palm, poplar, pine Generally burned to heat space or heat water to produce steam to generate electricity via a turbine generator When utilized directly: direct biomass Non-Woody Examples: corn, sugar cane, soybeans, algae Generally processed to produce different liquid biofuels Indirect biomass Producing Biofuel from
Biomass Biomass energy can be converted into liquid biofuels generally in two methods: Method I Sugar crops or starch are grown and through the process of fermentation, ethanol is produced. Method II Plants are grown which naturally produce oil, such as jatropha and algae These oils are heated to reduce their viscosity after which they are directly used as fuel for diesel engines This oil can be further treated to produce biodiesel which can be used for various purposes Biofuels Are Counterparts
Biofuels are counterparts to traditional fossil fuels Biofuel Fossil Fuel Ethanol Gasoline/Ethane Biodiesel Diesel Methanol Methane
Biobutanol Gasoline/Butane Comparing Energy Content The energy content of biodiesel is about 90% that of its counterpart petroleum diesel The energy content of butanol is about 80% that of gasoline The energy content of ethanol is about 50% that of gasoline
Biofuel Carbon Footprint Most biofuels are at least as energy dense as coal, but produce less carbon dioxide when burned Why Renewable? Biofuels are produced from biomass or bio waste, which can be replenished year after year through sustainable farming practices Biomass and biofuel are renewable Fossil fuels require millions of years to form Fossil fuels are NOT renewable Green Energy?
Renewable is NOT the same as Green A renewable energy source simply does not deplete Example: solar, wind, hydroelectric A green energy is ALSO good for the planet because it does not harm ecosystems, contribute to acid rain, or worsen global warming Solar energy is green and renewable All 'green' energy is considered renewable, but not all renewable energy is green Biofuels are examples of renewable energy sources that are not always green because they produce greenhouse gases Woody Biomass Coconut - In areas with abundant coconut trees, after harvesting the meat or edible part of the coconut, the hull is converted into a bio
briquette. The benefit of this biomass is that it burns efficiently and leaves very little residue. This has resulted in bio briquettes being used for cooking, particularly in underdeveloped countries. Oil Palm - The oil palm provides biomass in two ways. The fruit produces oil, which can be harvested and chemically converted to produce biodiesel. After the oil is harvested, however, the hulls can be burned directly. Thus, oil palm provide both direct and indirect biomass. Poplar - The poplar family includes trees like the Aspen and Cottonwood. These trees are valued for their rapid growth, reasonable resistance to disease, ability to provide habitat, and ability to be cultivated from sprouts cut from adult trees (reduces overall cost in the long term). Pine - Pine is valued for many of the same reasons as poplar. It grows fast, it's easy to cultivate, and is relatively inexpensive to grow. History of Biofuels Biofuels are nothing new. In fact, they've been around as long as cars have. Henry
Ford originally designed the Model T to run on ethanol. And people have been running diesel engines on vegetable oil much longer than they have been running diesel engines on petroleum-based diesel fuel. Rudolf Diesel, inventor of the diesel engine, originally designed it to run on vegetable oil. In fact, one of his early demonstrations, at the World Exhibition in Paris in 1897, had a diesel engine running on peanut oil. Petroleum based fuel originally won out over biofuel because of cost. The table is slowly turning though as fossil fuels become more expensive. During World War II, the demand for biofuel increased once again as fossil fuels became less abundant. Biofuel surged in popularity during the energy crisis of the 1970s. The most recent surge in biofuel popularity occurred in the 1990s in response to tougher emissions standards and increasing demands for enhanced fuel economy. History Ancient times-late 1800s People use biomass
materials (which today include plants and plant-derived materials, manure and even garbage) in the form of burning wood for cooking, warmth and steam production. By the late 1800s, wood was being replaced by coal as the primary means of steam generation. 1826 Ethanol was first prepared synthetically through the independent efforts of Henry Hennel in Britain and S.G. Srullas in France. Samuel Morey developed an engine that ran on ethanol and turpentine. History 1850s Ethanol is used as a lighting fuel. 1860s During the US Civil War, a liquor tax was placed on ethanol whisky to raise money for the war. The tax increased the price of ethanol so
much that it could no longer compete with other fuels such as kerosene in lighting devices. Ethanol production declined sharply because of this tax and production levels did not begin to recover until the tax was repealed in 1906 History 1919 When Prohibition began in the US, ethanol was banned because it was considered a liquor. It could only be sold when it was mixed with petroleum. 1920s Standard Oil began adding ethanol to gasoline to increase octane and reduce engine knocking. With 9 million automobiles in the United States, gas stations are opening everywhere. 1933 Prohibition ended in the US and ethanol was used as a fuel again. 1940s Ethanol use increases temporarily during World War II
when oil and other resources are scarce. First US fuel ethanol plant is built in Omaha, Nebraska. History 1970s Interest in ethanol as a transportation fuel was revived when embargoes by major oil producing countries cut gasoline supplies. Since that time ethanol use has been encouraged by offering tax benefits for producing ethanol and for blending ethanol into gasoline. 1975 Brazil formed the Pro-lcool Program (Programa Nacional do lcool, or National Alcohol Program) to reduce foreign oil dependence. This program used government financing to move toward ethanol use in lieu of fossil fuels. Brazil began making ethanol from sugar cane.
History 1980s After investing heavily in renewable fuels in the 1970s, Brazil kept the program alive during the 1980s. With its robust ethanol program, Brazil developed an extensive ethanol industry. By the mid-1980s, ethanolonly cars accounted for almost 90 percent of all new-auto sales in Brazil, making the country the biggest alternative fuel market in the world. History 1984 Burlington Electric in Vermont builds a 50megawatt wood-fired plant to produce electricity. 1988 Ethanol began to be added to gasoline for the purpose of reducing carbon monoxide emissions. 1989 Canada and the United States conduct pilot
trials of direct wood-fired gas turbine plants. 1990 Biomasss electricity generation reaches 6 gigawatts. History 2000 Brazil deregulated the ethanol market and removed its subsidies. However, depending on market conditions, all fuels are required to be blended with 20-25% ethanol. 2003 Since 2003, ethanol has grown rapidly as the oxygenating factor for gasoline in the US. Flex-fuel vehicles were introduced. These vehicles can run on straight ethanol, straight gasoline or a blend of the two. Today, the majority of new cars sold in Brazil are flex-fuel.
Classification of Biofuels Biofuels are classified into three generations 1 Generation Biofuels st 1st generation biofuels are also called conventional biofuels. They are made from things like sugar, starch, or vegetable oil. Note that these are all food products. Any biofuel made from a feedstock that can also be consumed as a human food is considered a first generation biofuel. It is important to note that the structure of the biofuel itself does not change between generations, but rather the source from which the fuel is derived changes. 1st generation biofuels suffer from the same problems including threatening the food chain, increasing carbon emissions when planted outside traditional agricultural settings, and intense growth requirements.
Ultimately, first generation biofuels have given way to second and third generation fuels. Though they will continue to provide biofuel for the foreseeable future, their importance is waning and new, better alternatives are being developed. Corn US is the world leading producer of corn and ethanol made from corn As of 2012, more than 40% of US corn crop was being used to produce corn-based ethanol Benefits: Existing infrastructure for planting, harvesting, and processing corn Corn starch to ethanol conversion is relatively simple No indirect land use costs Disadvantages Low ethanol yield per acre of corn produced
Requires large amounts of pesticides and fertilizers soil and water contamination, expensive Takes a significant amount of corn away from the global food supply raising global food prices and leading to hunger in underdeveloped countries Sugar Cane The majority of the world's sugar cane is grown in Brazil, which was the world's largest producer of alcohol fuel until very recently went it was eclipsed by the United States. Brazil produces roughly 5 billion gallons or 18 billion liters of fuel ethanol annually. The country adopted a very favorable stance on ethanol derived from sugar cane as a result of the oil embargo of the 1970s. Brazil has a policy of at least 22% ethanol in its gasoline, though 100% ethanol is available for purchase. Unlike corn, sugar cane provides sugar rather than starch, which is more easily converted to alcohol. Where as corn requires heating and then fermentation, sugar cane requires only fermentation.
The Advantages of sugar cane include: Infrastructure for planting, harvesting, and processing that is already in place. No land use changes provide plantations sizes remain stable. The yield is higher than that of corn at an average of 650 gallons per acre. Carbon dioxide emissions can be 90% lower than for conventional gasoline when land use changes do not occur. The disadvantages of sugar cane include: Despite having a higher yield than corn, it is still relatively low Few regions are suitable to cultivation Sugar cane is a food staple in countries of South and Central America Soybeans Unlike corn and sugar cane, soybeans are grown throughout much of North America, South America, and Asia. In other words, soybeans are a global food crop. The United States produce roughly 32 percent of all soybeans in the world, followed by Brazil at 28
percent. Despite its relatively high price as a food crop, soybean is still a major feedstock for the production of biofuel. In this case, rather than ethanol, soybean is used to produce biodiesel. Soybean is probably the worst feedstock for biofuel production. The Advantages of soybeans include: Grows in many regions Relatively easy to maintain The disadvantages of soybeans include: A yield of only about 70 gallons of biodiesel per acre, which is the worst yield of any crop. Palm oil produces almost 10 times as much biodiesel per acre at 600 gallons (note palm oil is considered a second generation feedstock). Soybean is a common food source and thus its use as a biofuel directly threatens the food chain. It faces a number of disease and pest burdens It is generally not a profitable biofuel feedstock. More energy is usually required to cultivate soybeans than can be derived from the fuel
produced from them. Jatropha and other seed crops In the early Part of the 21st century, a plant known as Jatropha became exceedingly popular The plant was praised for its yield per seed, which could return values as high as 40 percent. When compared to the 15 percent oil found in soybean, Jatropha look to be a miracle crop. Adding to its allure was the misconception that it could be grown on marginal land. As it turns out, oil production drops substantially when Jatropha is grown on marginal land. Interest in Jatropha has waned considerably in recent years. Other, similar seed crops have met with the same fate as Jatropha. Examples include Cammelina, Oil Palm, and rapeseed. In all cases, the initial benefits of the crops were quickly realized to be offset
by the need to use crop land to achieve suitable yields. 2 nd Generation Biofuels 2nd generation biofuels are produced from sustainable feedstock. The sustainability of a feedstock is defined by its availability, its impact on greenhouse gas emissions, its impact on land use, and by its potential to threaten the food supply. To qualify as a second generation, a feedstock must not be suitable for human consumption and Should grow on marginal (non-agricultural) land Should not require a great amount of water or fertilizer
Certain food products can become second generation fuels when they are no longer useful for consumption waste vegetable oil (2nd generation feedstock) Virgin vegetable oil (1st generation feedstock) Second generation biofuels are also referred to as advanced biofuels Second Generation Extraction Technology Because second generation biofuels are derived from different feed stock, Different technology is often used to extract energy from them. This does not mean that second generation biofuels cannot be burned directly as the biomass. In fact, several second generation biofuels, like Switchgrass, are cultivated specifically to act as direct biomass. For the most part, second generation feedstock are processed differently than first generation biofuels. This is particularly true of lignocellulose feedstock, which tends to require several processing steps prior to being fermented (a first generation technology) into
ethanol. An outline of second generation processing technologies follows. Thermochemical Conversion The first thermochemical route is known as gasification. Gasification is not a new technology and has been used extensively on conventional fossil fuels for a number of years. Second generation gasification technologies have been slightly altered to accommodate the differences in biomass stock. Through gasification, carbon-based materials are converted to carbon monoxide, hydrogen, and carbon dioxide. This process is different from combustion in that oxygen is limited. The gas that result is referred to as synthesis gas or syngas. Syngas is then used to produce energy or heat. Wood, black liquor, brown liquor, and other feedstock are used in this process. The second thermochemical route is known as pyrolysis. Pyrolysis also has a long history of use with fossil fuels. Pyrolysis is carried out in the absence of oxygen and often in the presence of an inert gas like halogen. The fuel is generally converted into two products: tars and char. Wood and a number of other energy crops can be used as feedstock to produce bio-oil through pyrolysis. A third thermochemical reaction, called torrefaction, is very similar to pyrolysis, but is carried out at lower temperatures. The process tends to yield better fuels for further use in gasification or combustion. Torrefaction is often used to convert biomass feedstock into a form that is more easily transported and stored. Biochemical Conversion A number of biological and chemical processes are being adapted for the production of biofuel from second generation feedstock.
Fermentation with unique or genetically modified bacteria is particularly popular for second generation feedstock like landfill gas and municipal waste. Waste Vegetable Oil (WVO) WVO have been used as a fuel for more than a century. In fact, some of the earliest diesel engines ran exclusively on vegetable oil. Waste vegetable oil is considered a second generation biofuels because its utility as a food has been expended. In fact, recycling it for fuel can help to improve its overall environmental impact. The advantages of WVO are: It does not threaten the food chain It is readily available It is easy to convert to biodiesel It can be burned directly in some diesel engines It is low in sulfur There are no associated land use changes The disadvantages of WVO are:
It can decrease engine life if not properly refined WVO is probably one of the best sources of biodiesel and, as long as blending is all that is required, can meet much of the demand for biodiesel. Collecting it can be a problem though as it is distributed throughout the world in restaurants and homes. Non-Woody Biomass: Grasses A number of different grasses have been suggested as potential biofuel feedstock. The most commonly discussed is Switchgrass. Switchgrass has the potential to be used both directly and indirectly. Its high cellulose content makes it an ideal direct biomass. In some settings it is burned directly whereas in others it is mechanically converted into pellets for easy transportation and storage. As the ability to generate ethanol from cellulosic continue to advance, Switchgrass become a more and more attractive option for this as well. The benefits of switch grass over other biomass include:
Perennial (lowers costs) Improved soil quality from not plowing each year Relatively high yield on marginal land not suitable for food production Drought and pest resistant Low water and fertilizer needs Non-Woody Biomass: Municipal Solid Waste This refers to things like landfill gas, human waste, and grass and yard clippings. All of these sources of energy are, in many cases, simply being allowed to go to waste. Though not as clean as solar and wind, the carbon footprint of these fuels is much less than that of traditionally derived fossil fuels. Municipal solid waste is often used in cogeneration plants, where
it is burned to produce both heat and electricity. 3 Generation Biofuels rd Unofficial category reserved for biofuels derived from algae Previously, algae were considered second generation biofuels. However, when it became apparent that algae are capable of much higher yields with lower resource inputs than other feedstock, many suggested that they be moved to their own category Algae-based biofuels require a unique production mechanism and potentially offer solutions to mitigate most of the drawbacks of 1st and 2nd generation biofuels
The Potential of Algae-based Biofuels No feedstock can match algae In terms of quantity or diversity. Algae produce an oil that can easily be refined into diesel or even certain components of gasoline Algae can be genetically manipulated to produce everything from ethanol and butanol to even gasoline and diesel fuel directly Butanol is of great interest because the alcohol is exceptionally similar to gasoline. In fact, it has a nearly identical energy density to gasoline and an improved emissions profile. Until the advent of genetically modified algae, scientists had a great deal of difficulty producing butanol Outstanding yields Algae have been used to produce up to 9000 gallons of biofuel per acre, which is 10fold what the best traditional feedstock have been able to generate
People who work closely with algae have suggested that yields as high as 20,000 gallons per acre are attainable According to the US Department of Energy, yields that are 10 times higher than second generation biofuels mean that only 0.42% of the U.S. land area would be needed to generate enough biofuel to meet all of the U.S. needs. Techniques for Cultivating Algae Algae can adventitiously be cultivated in diverse ways: Open ponds Algae is grown in a pond in the open air Simple design and low capital costs Less efficient than other systems Other organisms can contaminate the pond and potentially damage or kill the algae Closed-loop systems
Similar to open ponds but not exposed to the atmosphere and use of a sterile source of carbon dioxide Could potentially be directly connected to carbon dioxide sources (such as smokestacks) and thus use the gas before it is every released into the atmosphere Photobioreactors Complex, expensive, closed systems Significantly higher yield and better control Cultivating Algae For all three cultivation techniques, algae are able to be grown almost anywhere that temperatures are warm enough. This means that no farm land need be threatened by algae. Closed-loop and photobioreactor systems have even been used in desert settings. What is more, algae can be grown in waste water,
which means they can offer secondary benefits by helping to digest municipal waste while avoiding taking up any additional land. All of the factors above combine to make algae easier to cultivate than traditional biofuels. Challenges of Algae Production Algae require large amounts of water, nitrogen and phosphorus to grow So much in fact that the production of fertilizer to meet the needs of algae used to produce biofuel would produce more greenhouse gas emissions than were saved by using algae based biofuel to begin with. It also means the cost of algae-base biofuel is much higher than fuel from other sources. Currently, the net energy invested into producing biofuel using algae is greater than the
amount of energy that can be extracted from the fuel This single disadvantage means that the large-scale implementation of algae to produce biofuel will not occur for a long time, if at all. In fact, after investing more than $600 million USD into research and development of algae, Exxon Mobil came to the conclusion in 2013 that algae-based biofuels will not be viable for at least 25 years. What is more, that calculation is strictly economical and does not consider the environmental impacts that have yet to be solved. A minor drawback regarding algae is that biofuel produced from them tends to be less stable than biodiesel produced from other sources. This is because the oil found in algae tends to be highly unsaturated. Unsaturated oils are more volatile, particularly at high temperatures, and thus more prone to degradation. Unlike the fertilizer requirements above, this is a problem that has a potential solution. Advantages of Biofuels They are renewable sources of energy unlike other natural resources like coal, petroleum
and even nuclear fuel. Biofuels are the best way of reducing the emission of the greenhouse gases. Energy density: fossil fuels carry enough energy in a small enough space to make them very practical for a number of uses. Advantages of Biofuels Availability of Biofuels Environmental Impact http://biofuel.org.uk/advantages-of-biofuels.h tml Disadvantages of Biofuels
Regional Suitability Food Security Land Use Changes Impact on Biodiversity Global Warming http://biofuel.org.uk/disadvantages-of-biofuel s.html Sustaining Biodiversity There is one last problem presented by biofuels that needs to be addressed: biodiversity. Biodiversity refers to the variety of different living things in an environment. For instance, if you
grow only sweet corn in a field, you have low biodiversity. If, however, you grow sweet corn, dent corn, flint corn, flour corn, and popcorn, then you have high biodiversity. Why should we care? Growing a single type of corn is easier for producing biofuels because we can select that type that yields the best raw product, is easiest to grow, and which requires the least amount of water and other resources. This sounds great, but then down side to this is that pests that eat this type of corn will begin to proliferate. What is worse, if we spray with pesticide to kill these pests, some will inevitably be resistant to the pesticide. Over time, these pests will grow in number and we will be left with pests that are resistant to our chemical defenses. In the end, we have a bigger problem that what we started with and probably no corn because the new super pest ate it all. Biodiversity is important to ensuring that pests do not grow out of control. The type of farming needed to produce large quantities of biofuels is generally not amendable to high levels of biodiversity. This presents a fundamental problem in producing biofuels that is enhanced by the fact that super pests produced in the effort to grow biofuels can also threaten food crops.
Land Use and Biofuels The amount of land required to meet the worlds energy needs using biofuels is a major concern. Depending on the feedstock, the requirements can be massive. The following numbers reflect the amount of land that would be needed to meet the requirements of just the global aviation industry. Jatropha would need to be planted over 2.7 million square kilometers. That is an area roughly 1/3 the size of Australia. Camelina would require an area of 2 million square kilometers. Algae would need 68,000 square kilometers to meet the needs of the aviation industry. That is an area roughly the size of all of Ireland. The aviation industry accounts for only 13% of all fuel consumption, so the values above would need to be increased 10-fold to encompass global fuel demand. Jatraopha would need to be planted over 27 million square kilometers just to meet all fuel demands. An area that vast would cover all of Russia and the United States and still need a little more room. Algae would require an area of 680,000 square kilometers, or all of France plus some.
There is not enough land currently in use to meet fuel needs. That means forested areas would need to be cleared. This would release vast amounts of carbon and create a carbon debt that could take centuries to repay. The impacts of biofuels on greenhouse gas emissions were originally measured by considering only direct land use changes. When indirect land-use changes were considered, the green house gas savings from biofuels increased as follows (note that negative and positive values are in comparison to current fossil fuels): Corn ethanol From -20% to +93% Cellulosic ethanol From -70% to +50% Air and Water Concerns with Biofuels
Biofuels burn cleaner than fossil fuels, resulting in fewer tailpipe emissions of greenhouse gases, particulate emissions, and substances that cause acid rain such as sulfur. Biofuel production uses anywhere from 2 to 84 times as much water as fossil fuel production. Water use can be mitigated by planting crops that do not require irrigation. When the entire life cycle of a biofuel is considered, it may actually generate more greenhouse gases than fossil fuel. The following comparison of various fuel sources by gram of carbon dioxide produced per megajoule of energy produced. Note that the ranges provided for biofuels result from the location in which the feedstock is grown. For instance, sugarcane grown in Brazil as far less impact than sugarcane grown in South Africa. Coal - 112 Gasoline - 85 Diesel fuel - 86 Natural gas - 62
Biofuel made from sugar cane 18-107 Biofuel made from wheat 58 - 98 Biofuel made from corn 49-103 Biodiesel is sulfur free, but contains nitrates that contribute to acid rain. Biodiesel has fewer polycyclic aromatic hydrocarbons, which have been linked to cancer. The Carbon Equation Assuming we can overcome the problem of biofuels interrupting the food supply (such as growing algae in the ocean), can we overcome the problem of biofuels contributing to global warming? The answer, surprisingly, may be yes. It is true that biofuels produce carbon dioxide, which is a potent greenhouse gas and the one most often blamed for global warming. However, it is also true that growing plants consumes carbon dioxide. Thus, the equation becomes a simple balancing act. If the plants we grow utilize the same amount of carbon dioxide that we produce, then we will have a net increase of zero and no global warming. How realistic is this view? It may seem like a simple matter to only produce as much carbon dioxide as plants use. After all, couldnt we only burn biofuels and thus keep the equation balanced? Well, the math actually doesnt quite add up. Research has
shown that energy must be invested into producing crops and converting them into biofuels before any energy is obtained. A 2005 study from Cornell University found that producing ethanol from corn used almost 30% more energy than it produced. In other words, you cant produce a perpetual motion machine using biofuels because you lose the energy you invest in creating them in the first place. In fact, you cant even break even. The other problem that we run into with biofuels is that carbon dioxide is not the only greenhouse gas we have to worry about. Other chemicals, like nitrous oxide, are also greenhouse gases and growing plants using fertilizer produces a lot of nitrous oxide. Basically, fertilizer contains nitrogen, which plants need to grow. However, most plants cannot convert molecular nitrogen into the elemental nitrogen they need. For this process, plants rely on bacteria. As it turns out, bacteria not only produce nitrogen that plants can use, they also produce nitrogen products like nitrous oxide, and probably more than was previously thought. The net result is that we may be balancing the CO2 equation by using biofuels, but we are unbalancing the N 2O part of the equation and still causing global warming. Prospects for Biofuel A decade ago, subsidies for biofuel growth and development in many countries (especially the U.S.) were high.
However, better understanding of global warming, increased awareness of the fragility of the food supply, and a general trend toward greener alternatives have all led to a decline in the popularity of biofuels. In 2011, The U.S. Senate voted 73 to 27 to end tax credits and trade protections for corn-based ethanol production. As the second largest producer of ethanol, this is a substantial move that reflects the changing pressures on our energy needs and shifted focus to environmentally friendly energy sources. References
http://biofuel.org.uk/advantages-of-biofuels.html http://biofuel.org.uk/disadvantages-of-biofuels.html http://biofuel.org.uk/biofuel-facts.html http://www.energy4me.org/energy-facts/energy-sources/biofuels/3/ http://www.energy4me.org/energy-facts/energy-sources/biofuels/3/ http://biofuel.org.uk/biofuel-facts.html https://www.google.com/search?q=Biofuels&biw=790&bih=639&source=lnms&tbm=isch&sa =X&ei=mZROVOfXE-PuigLu5oGYCQ&ved=0CAcQ_AUoAg#imgdii=_