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Bioenergy is renewable energy produced by living things like plant matter or by the waste that living creatures produce, such as manure. These living things and their waste products are called biomass. Biomass is organic matter (which comes from living things), just like fossil fuels (coal, oil, or natural gas, which are formed in the earth from plant and/or animal remains), but it is much more recently created and is renewable on a time scale that is useful to humans. Fossil fuels take millions of years to form. During this time they accumulate large amounts of carbon, which is returned to the atmosphere during burning. Plants grow continuously, animals constantly produce manure, and people throw away waste material all the time. Using these items for fuel does not deplete them because they are always being made.

For this reason, many experts believe that bioenergy will be a major source of power in the future. Besides being renewable, many kinds of bioenergy are considered less polluting than fossil fuels. They can be used as direct substitutes for fossil fuels, powering diesel or gasoline engines, heating buildings, and producing electricity. They can be made and used locally, which can make individual areas more self-sufficient and less reliant on foreign suppliers for energy. Bioenergy is created by using biofuels. Biofuels are made from sources of biomass including wood, plant matter, and other waste products. These sources can then be turned into biofuels. There are three types of biofuels: solid, liquid, and gas.

Types of bioenergy

Biofuels come in all three forms of matter: solid, liquid, and gas. Solid biofuels are solid pieces of organic matter that release their energy through burning. Solid biofuels include the following:

  • Animal waste (dung or manure)
  • Bagasse (plant waste left after a product like juice or sugar has been removed)
  • Charcoal
  • Garbage
  • Straw, dried plants, and the shells of grains
  • Wood

Words to Know

Without air; in the absence of air or oxygen.
Diesel fuel made from vegetable oil.
Energy produced through the combustion of organic materials that are constantly being created, such as plants.
A fuel made from organic materials that are constantly being created.
Organic materials that are constantly being created, such as plants.
Distiller's grain
Grain left over from the process of distilling ethanol, which can be used as inexpensive high-protein animal feed.
A substance used as a raw material in the creation of another substance.
Flexible fuel vehicle (FFV)
A vehicle that can run on a variety of fuel types without modification of the engine.
The framework that is necessary to the functioning of a structure; for example, roads and power lines form part of the infrastructure of a city.

Liquid biofuel is any kind of liquid derived from matter that has recently been alive and that can be used as fuel. Types include the following:

  • Biodiesel, which is diesel fuel made of vegetable oils and animal fats instead of petroleum.
  • Vegetable oil fuel, including straight vegetable oil, or SVO, and waste vegetable oil, or WVO.
  • Ethanol and other alcohol fuels, which are made from corn, grain, and other plant matter and can be mixed with or substituted for gasoline.
  • New fuels, such as P-Series fuels, which combine ethanol, natural gas traces or leftovers, and a substance made from garbage.

Biofuel can also come in the form of a gas, or biogas, particularly that is emitted (given off) by decaying plants, animals, and manure. This gas is largely methane, which is the main component of the fuel natural gas. Most methane used in 2005 comes from fossil fuels, but scientists are currently researching ways to collect methane from decaying garbage. Scientists are also investigating the possibility of using biofuels to generate hydrogen, which could then be used in fuel cells. Gasification of solid biofuels (transforming their energy into natural gas) is also a possibility.

Whale Oil

Whale oil was an important liquid biofuel in the eighteenth and nineteenth centuries. Whalers traveled the world's oceans searching for right whales and sperm whales in order to kill them and remove the oil from their bodies. This oil was used to light lamps and to make candles, cosmetics, and drugs. People still hunted whales in the twentieth century, and new uses were developed for whale oil. However, synthetics and fossil fuels replaced whale oil for almost all purposes by the mid-twentieth century. They were cheaper and more plentiful, especially as whales were hunted to near extinction and became more difficult to find and catch. Most of the world's countries in the twenty-first century have declared whaling, and the taking of whale oil, illegal.

Historical overview: Notable discoveries and the people who made them

People began experimenting with bioenergy in motors in the mid-1800s. In 1853 scientists used a chemical process with vegetable oil that created biodiesel. Rudolf Diesel (18581913), inventor of the diesel engine, gave a speech in 1912 in which he suggested that vegetable oil fuels were destined to become as important as petroleum and coal. However, diesel engine manufacturers in the 1920s geared their engines to run on thicker petrodiesel (diesel made from fossil fuels) because it was cheaper than biodiesel at the time. As a result, manufacturers ignored vegetable oil fuels for most of the twentieth century. Nevertheless, a few people used biodiesel and vegetable oil fuels throughout the 1900s.

Ethanol, too, generated interest in the early 1900s. Henry Ford (18631947) believed ethanol made from grain would be a valuable fuel. No one used much ethanol, however, until the oil embargo of 1973 led to an oil crisis. Convinced that the world was running out of oil, some people decided to use ethanol instead of gasoline. The movement was small in the United States and focused mainly in corn-growing states, but it became a big business in Brazil, which had ample sugarcane to use in making ethanol. Ethanol-burning automobiles were popular in Brazil until the late 1980s, when oil prices came down and sugar prices went up.

In the late 1900s, as people grew increasingly concerned about the limited supply of fossil fuels and the pollution caused by burning them, scientists and consumers once again turned their attention to bioenergy. In the 1990s France began producing biodiesel fuel locally, using rapeseed oil to make the fuel. By the end of the twentieth century a large number of French vehicle manufacturers were producing vehicles intended to use some biodiesel in their fuel mixes. Increasing numbers of ethanol fuel plants were being built in the early 2000s. Biofuels may become big business in the twenty-first century as the supply of fossil fuels dwindles and the price of fossil fuels goes up. Biofuels such as biodiesel are increasingly part of European union legislation, so there is much pressure to develop and use them.

How bioenergy works

Biofuels work by burning either directly (such as putting wood logs on a fire) or indirectly as through an engine. They are similar to fossil fuels, which also release their energy when they burn. Biofuels are the alternative fuels most similar to fossil fuels. In many cases they function as direct replacements of, or supplements to, fossil fuels.

The 1973 Oil Crisis

On October 17, 1973, the nations that belonged to the Organization of Petroleum Exporting Countries, better known as OPEC (OH-pek), announced that they would no longer sell petroleum to nations that had supported Israel in its fight with Egypt. These nations included most of Western Europe and the United States. Oil suddenly cost four times more than it had the month before. Gasoline appeared to be in short supply, and nations began limiting people's access to fuel. The government of the United States realized how dependent it was on Middle Eastern oil and responded by increasing efforts at U.S. oil exploration and extraction. The crisis spurred a new interest in fuel economy and alternate sources of energy. The national speed limit was reduced to 55 miles per hour, Daylight Savings Time was lengthened to save electricity, and the Department of Energy was created.

The internal combustion engine

Gasoline is the main fuel used in automobiles, which are powered by internal combustion engines. The basic principles of internal combustion have not changed in over one hundred years. They are the same whether the fuel is petroleum-based or biofuel. An internal combustion engine burns a fuel to power pistons, which make the engine turn. An engine contains several cylinders (most cars have between four and eight) that make the whole engine move.

One complete cycle of a four-stroke engine will turn the crank-shaft twice. The crankshaft is a shaft connected to a crank that turns and moves the pistons in an engine up and down. A car engine's cylinders can fire hundreds of times in a minute, turning the crank-shaft, which transmits its energy into turning the car's wheels. The more air and fuel that can get into a cylinder, the more powerful the engine will be. An engine using methanol is a bit different than one using petroleum or propane, but the concept is similar.

Stoves, campfires, and grills

The simplest technology using solid biofuels is a fire, such as a campfire, which consists of a pile of sticks, logs, or animal dung set on fire. There are many ways to arrange the pile of sticks, logs, or dung for safety and efficiency of burning, but basically the construction of a fire is simple and does not require the addition of complex equipment. Charcoal is often the preferred fuel because some of the other fuels give off smoke that can be harmful to the environment.

There are also devices that make it easier for people to use fires for heat or cooking. Grills placed on top of a fire, or devices that can hold a fire in a bowl with a grill on top of that, make it easy to cook food. Woodstoves come in a variety of styles. Some woodstoves make it possible to heat a large house with a small fire. Others contain both stove tops and ovens for cooking flexibility.

Gas pipes

Gaseous fuels travel through pipes from the place where they are produced to the place where they burn. In London in the 1800s, pipes delivered biogas from the sewers to street lamps. In 2005 some dairy farmers collect biogas from fermenting tanks of manure and run it to their appliances through pipes. The biogas can be lit at the pipe's end, powering a light, a stove, or another appliance.

Current and future technology

Biofuels are already widely used in many parts of the world. Germany, Britain, France and Brazil all use biofuels in different ways. Biodiesel and ethanol are increasingly common. Scientists are working to develop new technologies that can take advantage of currently inaccessible sources of bioenergy.

Vegetable oil was one of the first fuels used in internal combustion engines. Today most vegetable oil is consumed in the form of biodiesel, which functions almost exactly like diesel made from petroleum, called petrodiesel. Vegetable oil, either new or used, can be used for fuel by itself in diesel engines, though the engines must be modified for this to work well. In the twenty-first century large companies are taking more of an interest in biodiesel; commercially prepared biodiesel is becoming more widely available, either straight or mixed with petrodiesel.

Ethanol, which is the same alcohol used in alcoholic beverages, has a long history of use as a fuel. Other alcohols, such as methanol, can also be used as fuel. Ethanol is easy to make from corn, grain, sugarcane, or other plant material. Ethanol can be mixed with gasoline to power internal combustion engines. Normal cars can use small amounts of ethanol in their fuel. Flexible fuel vehicles (FFVs) can use fuel that is nearly all ethanol. (Few vehicles in the early twenty-first century can use straight ethanol with no gasoline in it.) In some parts of the world, ethanol is routinely mixed in fuel, reducing the use of fossil fuels.

Scientists are also working to develop new types of fuels. P-Series fuel is a fuel that is made from a combination of ethanol, the leftovers from natural gas processing, and a substance made from garbage. It works in flexible fuel vehicles and appears to be a stable substitute for gasoline. Whether these fules are pollutants or not has not been concluded. Some scientists believe that they are non-polluting, but others believe that they give off significant nitrogen oxide emissions.

Benefits and drawbacks

Biofuels appear likely to furnish at least some of the world's energy needs. There are many good reasons to use biofuels:

  • They are environmentally much cleaner than fossil fuels, producing less air pollution and consuming materials that would otherwise be considered garbage.
  • They are renewable; the supply of biofuels is less likely to run out, while the supply of fossil fuels probably will.
  • They can be made locally using local materials.
  • They can be flexible, easily mixed with other fuels.
  • They can be cheaper than fossil fuels and will certainly become less expensive as the price of fossil fuel rises.
  • Ethanol and biodiesel are better for car engines than fossil fuels. They can be used as additives to improve performance even if they are not the main fuel source.

But biofuels are not without some disadvantages:

  • To make large amounts of biofuels would require cultivating more land than is currently farmed. This could be a very large problem to try to overcome.
  • Some kinds of biofuels require modifications to vehicle engines.
  • Making biodiesel at home or processing vegetable oil for home use is messy and inconvenient.
  • Biofuels are not widely available.
  • Some biofuels still require the use of fossil fuels; for example, most vehicles must have some gasoline mixed into ethanol to work and cannot run on ethanol alone.

Environmental impacts

Bioenergy is less polluting than fossil fuel-produced energy in respect to carbon dioxide. Biofuels contain carbon that only recently was in Earth's atmosphere, so the carbon dioxide released through burning them does not add to total carbon dioxide in the air. Fossil fuels, however, contain carbon that was removed from the atmosphere millions of years ago, and they emit large amounts of extra carbon dioxide when they burn. Replacing some fossil fuels with biofuels may help ease global warming, lessen air pollution, and clean the world's air.

Bioenergy, however, may be a contributor of formaldehyde to urban air. Biodiesel fuels are potentially high emitters of nitrogen oxides, which are a major component of smog. People with respiratory illnesses and small children are most affected by these air pollutants.

Flexible Fuel Vehicles

Flexible fuel vehicles, or FFVs, are vehicles that can run on various kinds of fuels, such as ethanol-gasoline blends, methanol, gasoline, P-Series fuels, or combinations of those, without having to be physically modified. The engine contains sensors that identify the type of fuel and adjust the timing of the spark plugs and fuel injectors to provide the optimum combustion.

In 2005 some common FFVs included the Ford Explorer, the GM Yukon, and the Mercedes-Benz C320. The owner's manual of the car states if the vehicle is indeed an FFV. Most FFVs are in the sport utility vehicle or light truck category. Sedans that are FFVs are usually made specifically to be fleet vehicles, one of many identical cars owned and used by a large company or organization.

Biofuels are renewable. They come from plants and other currently growing organic material, so it is possible to generate new ones constantly. This makes them more environmentally appealing than fossil fuels, which are, for all practical purposes, not renewable and are even in the process of being depleted.

Biofuels can use waste for feedstocks (starting materials). For example, waste vegetable oil from fast food restaurants or potato chip factories can be turned into biodiesel. This prevents the waste material from being disposed of in a landfill.

On the other hand, biofuels require large amounts of land to be cultivated and harvested. This can cause major environmental problems, such as habitat destruction and fertilizer runoff. Farmers use large amounts of fossil fuels to grow crops such as corn, which decreases the value of the energy made from those crops. In some cases, producing biofuels such as ethanol actually uses more energy than the ethanol yields.

Economic impacts

In the early 2000s production of biofuels increased very rapidly. In the United States production of ethanol rose 30 percent each year between 2000 and 2005. During the same period Germany's production of biodiesel increased by 40 to 50 percent annually. France planned to triple its output of ethanol and biodiesel between 2005 and 2007, while Britain built two major biodiesel plants during the first few years of the century. As of 2005 China had built the world's largest ethanol plant and intended to build another just like it. A Canadian company planned to build a plant to make ethanol out of straw.

The reason for this increase was simple. Biofuels had previously been more expensive than fossil fuels, making them uneconomical during most of the twentieth century. Some people had supported biofuels all along because they wanted the world to use fuels that they believed were not as damaging to the environment as fossil fuels, and they persuaded governments to back them. But in the early 2000s it became clear that biofuels also made good economic sense. The price of fossil fuels went up, making biofuels comparatively cheaper. Depending on location, biofuels even became cheaper in real terms, that is, without governmental supports.

For individual consumers, biofuels can be more or less expensive than fossil fuels depending on how they are used. People who make their own biodiesel using free waste vegetable oil from restaurants spend very little money on fuel, though they do spend a certain amount of time in the pursuit of energy. Wood heat can be less expensive than electrical or gas heat. In the past, purchasing biofuels was usually more expensive than purchasing fossil fuel equivalents. That is changing in the twenty-first century, and more people are finding that biofuels make economic sense.

Societal impacts

One of the biggest impacts that biofuels can have on society is increased self-sufficiency for areas and individuals that use them. Individual consumers and most nations do not have fossil fuels readily available. People and countries must buy their oil, gas, or coal from large companies that drill and process them. Consumers are vulnerable to changes in the price or supply of oil. Using biofuels allows people or nations to make their own fuel on the spot. This is especially useful to developing nations that have a large need for energy but do not have much money to buy fossil fuels.

Barriers to implementation and acceptance

Few people used biofuels during the twentieth century because fossil fuels were readily available and inexpensive. By the early twenty-first century biofuels were becoming more attractive to large companies, which suddenly saw biodiesel and ethanol as potential sources of profit. Oil and gas companies still have little interest in pursuing sources of bioenergy, and their influence on national and state governments could prevent biofuels from being used in public transportation fleets.

Most people still know little about biofuels and so do not seek them out. Biofuels are not readily available in many places, so it is difficult for people to use them. Few people want to go to the trouble of making their own biodiesel or modifying their car engines to run on vegetable oil. As biofuels become more commercially available and user-friendly, consumers are likely to adopt them in increasing numbers.


Solid biomass was the first fuel humans ever used. Prehistoric humans used wood and animal dung to make their first fires, over which they cooked food and kept themselves warm. Ever since, solid biomass has played an important role in human energy needs.

Biomass energy is energy derived from solid organic matter other than fossil fuels. This can include charcoal, wood, straw, hulls of grains, animal manure, and bagasse (solids left over from the processing of sugarcane or fruit). The fuel can be used directly as for fire or used to power other devices such as electrical generators.

Solid biomass fuel can be used as it is found, but it often benefits from some processing to make it drier or denser than it is in nature. For example, the process of making charcoal transforms wood into a dry substance that is nearly pure carbon. Removing impurities can also improve efficiency.

Whether solid biomass is renewable or not depends entirely on how rapidly it is used. Wood met human energy needs for millennia, but once a forest is completely cut down, it becomes useless until the trees grow back, if they do.

Current uses of solid biomass

Solid biomass is still widely used around the world. Most developed nations have moved away from using solid fuels for their day-to-day energy needs, favoring more efficient and readily available fossil fuels, but in much of the world wood for the fire is still a daily necessity. People in developed countries still use solid biomass as a source of fuel for some purposes.

Animal waste

Animal feces, also called manure or dung, is an important source of fuel around the world. Manure contains large amounts of carbon and nutrients that can be used as fertilizer, but it also contains ample plant fiber that will burn. Dried dung is widely used as fuel for fires in areas where there are many animals. People use dung from cattle, buffalo, horses, llamas, kangaroos, and other creatures. Biomass sources such as garbage and manure can be allowed to decay to produce methane, or natural gas.


Bagasse is the solid material left behind after removing a product from its source, such as juice from oranges or grapes and the sugar from sugarcane. About 30 percent of the sugarcane is left over after processing, and this solid fibrous material has long been used as fuel. In the earliest days of sugarcane processing, the bagasse was used as fuel for the sugar mill; in some cases, the processors would not extract as much sugar as they could from the bagasse so that they would have more bagasse left over to burn.

Bagasse is now an important source of fuel in Brazil. Brazil expanded its sugar industry in the 1970s to make sugar to produce ethanol. The ethanol plants use bagasse to power their machinery. Brazilian sugar growers sell excess bagasse to other industries, such as juice and vegetable oil factories, which burn it instead of fuel oil. This saves the nation several million dollars a year in oil import costs.

The Problem with Poop

Manure is a big problem for anyone who raises large numbers of farm animals such as cattle. A herd of cattle produces a tremendous amount of manure. Modern farmers gather the manure from barns or pastures and collect it in large heaps. Manure, like any pile of organic matter, gets hot as it decomposes. It can get so hot that it catches on fire, which results in a dangerous situation and very stinky smoke. Piles of poop also breed flies, which can spread disease. Though manure has many uses, on large farms it quickly becomes too much of a good thing. That is why scientists are investigating uses for manure such as the production of biogas.


Charcoal is a black combustible material made by removing the water and volatile substances from wood or other organic materials. It consists almost entirely of carbon, usually between 85 and 98 percent. The main reason to make wood into charcoal is to make it burn hotter and more efficiently. Wood contains a great deal of water, which cools the fire; volatile compounds such as methane and hydrogen; and tars. To make charcoal, wood is buried to prevent oxygen from reaching it and allowing it to catch fire and then baked at a moderate heat for many hours. The impurities burn off in smoky clouds. Commercial charcoal manufacturers add borax to bind (hold together) the charcoal, nitrate to help it catch fire, and lime to color the ashes white.

Most twenty-first century Americans use charcoal only on outdoor grills, but charcoal has a long history of use. Bronze Age Europeans five thousand years ago used charcoal to melt metals. Blacksmiths used charcoal because it produced more heat than wood, important for heating metal. Charcoal was fuel in glassmaking and cooking. Artists use charcoal to create soft gray or black lines that blend easily. Charcoal is an ingredient in gunpowder. Charcoal in the metallurgy industry (metal industry) has now largely been replaced by fossil fuels such as coke and anthracite coal.


Compost is organic material that has decomposed and turned into humus (material that results from partially decomposed plant and animal matter). It is added to soil as fertilizer and to improve the soil's structure. Plant matter that falls to the ground, such as leaves from trees, naturally decomposes and becomes part of the soil. Composting is the practice of consolidating this matter and controlling the conditions under which it decomposes, which speeds up the decomposition greatly. A compost bin or pile can contain dried leaves, green plant matter, table scraps such as vegetable skins, animal manure, and even paper. The mix needs water and oxygen to decompose properly. Microbes and insects such as ants break down the organic matter and turn it into a substance that looks very much like dirt. Though a simple trash heap will eventually produce usable compost over many months, a skilled composter will use techniques that make the pile grow very hot, killing seeds and germs and producing usable compost in just a few weeks.

Compost is not itself an energy source, but it can be a valuable replacement for fertilizers made with fossil fuels like natural gas. Farmland enriched with compost is more fertile than uncomposted land because the nutrients from the compost become part of the soil. Organic gardeners use compost to recycle yard and table waste and to make their soil richer. About one-third of landfill space is occupied by yard waste and table scraps. Putting yard waste and table scraps into compost saves landfill space by turning those materials into dirt.


Garbage is usually seen as a problemas waste material that must be dumped somewhere, but preferably not close to anyone's home. Some scientists, however, have been experimenting with ways to turn garbage into fuels or useful substances. Some types of garbage can be converted into biogas, which can be used as fuel. Garbage is also a component of P-Series fuel.

Straw, dried plants, and shells of grains

There is some possibility that dried plant matter could be used to manufacture ethanol. Making ethanol from this kind of cellulose (cellular material in plants) is more difficult than making it from sugarcane or grain. Straw and hulls do not contain as much sugar, and it is more difficult to remove the sugar from them, but it is possible. These dried substances can also be made into compost or converted into biogas. They are usually not the best fuels for fires because they burn quickly and cannot produce long-lasting heat.


Wood is perhaps the oldest solid biomass fuel. For most of human existence people have burned wood for heat and cooking. In many parts of the world wood is still the primary or the only available source of power. In the United States, wood is still a common source of heat in colder climates where it is plentiful. Some homes have wood stoves that burn wood to heat the house. Others have boilers outside the house that pipe heat into the home. Wood had a brief resurgence in popularity after the 1973 oil crisis.

The residues of wood and other forms of biomass can be used as a source of gaseous fuel. For example, wood residue inside a reactor vessel can be heated to make it break down and produce gas. This gaseous fuel can be burned on the spot as fuel for a turbine or other device.

Benefits and drawbacks of solid biomass

Solid biomass is renewable, at least as long as plants keep growing and are not harvested faster than they can replace themselves. Solid biomass is flexible; a stove that can burn wood can probably also burn charcoal, dung, or other solid matter, though the results may be different. It can be used for simple purposes such as heating a home directly or complex ones such as generating electricity.

Ancient Central Heating: The Hypocaust

The ancient Romans used wood to create central heating for their homes. They used a system called a hypocaust. A hypocaust was a structure of tunnels under the floor of a building leading up into ducts in the walls of rooms. People would light a fire in the hypocaust, and the warm air would flow through the tunnels and air ducts, heating the building. This system was also used in public baths to heat floors, rooms, and water. A hypocaust was not a practical solution for most people because it required several slaves to feed the fires and remove ashes, and it could only be implemented in buildings made of stone or brick.

Yet solid biomass is only renewable as long as it is not consumed faster than it can be replaced. Solid biomass fuels have much lower energy content than fossil fuels, which means that people using them must acquire large quantities of them to do the same jobs that much smaller quantities of fossil fuels can achieve. Coal, for example, burns much hotter than wood and lasts longer. Anyone using solid biomass for home heating and energy must have access and transportation for large quantities of fuel and must be able to store it until it is needed, such as in a woodpile.

Preparing solid biomass fuels can take a great deal of work. Wood is heavy to move and must be cut into small pieces to fit into stoves or fireplaces. Dung must be collected and carried to wherever it will be burned, and bagasse takes up a great deal of space. A fire fed by solid biomass fuels must be fed regularly or it will go out. Fireplaces and stoves fill with ashes that must be removed from time to time. Ventilation can be a problem, because these fuels all produce smoke. In addition, smoke from woodstoves can be very high in carcinogenic substances.

Environmental impact of solid biomass

Burning wood does not contribute to greenhouse gases because burning wood releases no more carbon dioxide than can be consumed by growing trees. Modern heating stoves are designed to emit few greenhouse gases. Burning wood does produce ash, but ash can be used as fertilizer or in soap making. Bagasse likewise produces few greenhouse gases. However, burning any renewable biomass fuel causes smoke that can seriously cloud the air in the immediate area. Sugarcane cutters often burn cane fields before cutting down the sugarcane. The resulting smoke can linger in nearby towns for weeks. Animal dung causes especially bad air pollution; the World Health Organization estimates that 1.5 million people have died of inhaling air polluted by burning dung.

Issues, challenges, and obstacles of solid biomass

Deforestation (the destruction of forests) is a growing problem around the world. Without enough trees to provide wood, solid biomass fuel will not be a practical source of energy. Tree farming has largely solved this problem in the developed world, but in places where solid biomass fuel is still the main fuel source, lack of trees is a serious problem.

Woodstoves experienced a surge of popularity in the 1970s, after the oil crisis of 1973. Since then other sources of fuel have once again grown in popularity. Solid biomass fuels do not contain as much energy per weight as fossil fuels, so they are not the focus of most research into future energy sources. Wood, charcoal, bagasse, and other solids will probably still be used in the future but only for small-scale purposes such as home heating and cooking. Though biomass fuels have the potential to be a valuable source of energy in some places, such as Brazil's bagasse electricity industry, in most areas they do not seem to be practical sources of large-scale power.


Biodeisel is diesel fuel made from renewable sources of carbon such as used vegetable oil or animal fats used in cooking. In diesel engines it can be used as a direct substitute for petrodiesel fuel made from petroleum.

Biodiesel is a clear amber liquid. Its consistency is similar to that of petrodiesel. Biodiesel can be used on its own in a diesel engine or mixed with petrodiesel. Some people mix small amounts of biodiesel into gasoline to decrease its air-polluting qualities.

Biodiesel is usually made out of the vegetable oil that is most readily available in a particular area. In France most commercial biodiesel is made from rapeseed oil. Other kinds of oil used to make biodiesel include palm, mustard, Jatropha, and soybean.

In the United States, soybeans make up the biggest source of biodiesel fuel because they are widely grown. Soybeans are not a particularly good source of biodiesel, but soybean growers have been able to expand the market for soybean-based biodiesel. Rapeseed, mustard, and Jatropha all produce two or three times as much oil as soybeans. Palm oil is an excellent source of oil to make biodiesel, and there has been some research into growing algae to use in making the fuel. Scientists are working on developing crops that produce larger amounts of oil for use in making biodiesel.

Biodiesel users sometimes refer to biodiesel or biodiesel blends by the letter B followed by a number indicating the percentage of biodiesel in the mix. For example, B20 is petrodiesel that contains 20 percent biodiesel. B100 is pure biodiesel.

Vegetable oil into diesel fuel

It is possible to run a diesel vehicle on plain vegetable oil from the grocery store. The first diesel engine ran on straight peanut oil. In diesel engines, however, unprocessed vegetable oil is not very good for the engine because it eventually clogs the filters. In order to keep running the vehicle on vegetable oil, the owner must modify the engine; this is generally true even if the owner mixes the vegetable oil with petrodiesel or kerosene. If the vegetable oil is transformed into biodiesel, however, it becomes so similar to petrodiesel that it can be used in an unmodified diesel engine with no ill effects.

Biodiesel can be made from either new or used vegetable oil or from animal fat. Vegetable oil is the most common feedstock. Waste oil is more difficult to process into biodiesel than virgin oil because it must first be filtered to remove impurities. On the other hand, it is cheaper, often free, and is a good way of recycling a product that otherwise would be thrown away.

How biodiesel is made

Making biodiesel involves joining the fatty acids of the vegetable oil or animal fat into long chains of triglycerides in a process called transesterification. This process converts the oil into long chains of mono-alkyl esters and glycerin. To transform the fats into biodiesel, a processor mixes an alcohol with a lye catalyst (something which causes a chemical reaction faster or at a different rate than it normally would) and then combines the mixture with warm oil. The most common alcohol used in this process is methanol, or methyl alcohol, but ethanol will work as well. The fatty acids float to the top of the mix and are siphoned off as biodiesel, while the glycerin stays at the bottom of the mixing vessel. The biodiesel must then be washed to remove any contaminants that could damage an engine.

Many people make their own biodiesel at home. There are many recipes available, easily found on the Internet. Though biodiesel fans claim that whipping up a weekly batch is no problem, the procedure involves a certain amount of trouble, mess, and danger.

Current use of biodiesel

Biodiesel will work in any diesel engine, with no modifications necessary. This means it can be used as a substitute for petrodiesel fuel. It can be mixed into petrodiesel to reduce emissions, improve engine performance, and clean engine parts.

For many years the only people using biodiesel were enthusiastic environmentalists who made their own biodiesel at home, but that has changed. Commercial suppliers have been making biodiesel and selling it to the public for several years. Biodiesel is widely used in Europe and Asia. France is the world's largest producer of biodiesel. All petrodiesel fuel sold in France contains at least 5 percent biodiesel. In Germany over 1,500 filling stations sell biodiesel, which is less expensive than petrodiesel. The European Union, of which France and Germany are members, passed legislation to require all member states to mix biodiesel into their petrodiesel. Public transportation fleets are often the first vehicles to adopt the use of biodiesel or biodiesel-petrodiesel blends as their standard fuel.

In the early 2000s biodiesel is becoming more common in the United States. Several states have passed laws requiring biodiesel to be mixed into diesel fuel. Over five hundred commercial fleets use biodiesel. Users include the United States Postal Service, the United States Marine Corps, the National Aeronautics and Space Administration (NASA), the United States Department of Agriculture, numerous state departments of transportation, and the San Francisco International Airport.

The use of biodiesel is increasing rapidly worldwide. In 1998, for instance, 380,000 gallons of commercially manufactured biodiesel were sold in the United States. That amount increased to thirty million gallons in 2004. Biodiesel production is fast becoming a viable economic opportunity and is attracting investors and inventors.

Benefits and drawbacks of biodiesel

Biodiesel has many benefits. It is very easy to substitute for petrodiesel. Employees do not need special training to use it and no equipment needs to be modified. Unlike petrodiesel, biodiesel will not catch fire or explode. It is not poisonous to humans. It is completely biodegradable (capable of being broken down into harmless products). It is environmentally much cleaner than petrodiesel.

In addition, bodiesel is an excellent engine cleaner. It will remove dirt and residue left in a tank and fuel system by petrodiesel. Biodiesel can be added to ultra-low-sulfur petrodiesel to improve its lubricity (ability to reduce friction or rubbing). It makes the diesel fuel flow more smoothly and prevents the accumulation of contaminants within the engine and fuel system.

One reason many people make their own biodiesel is that they take pride in being independent of oil companies and being able to create their own fuel. Many of them save a great deal of money as well, but for many the feeling of independence and environmental virtue is the real attraction.

One major problem with biodiesel is that it is not widely available. France, Germany, and other European countries have many filling stations that sell it, but biodiesel is rare in the United States. For this reason, many people make their own, which itself presents problems. Making biodiesel is time-consuming and can be dangerous. Waste oil must be filtered before it can be used. The chemicals used to make biodiesel are poisonous to humans. Anyone making biodiesel must purchase safety equipment, including gloves, aprons, and respirators, and must have access to a secure work area that children and animals cannot enter.

Another drawback is that biodiesel can be more expensive than petrodiesel, depending on its ingredients. Purchasing new vegetable oil can be expensive, and biodiesel users must often purchase other ingredients and equipment to make the fuel. Converting a diesel engine to run on SVO (straight vegetable oil) can cost money.

Also, biodiesel is not as effective as petrodiesel in cold weather. Both kinds of diesel fuel get cloudy and full of small wax crystals that can clog fuel filters, but biodiesel is more sensitive to this problem than petrodiesel. When biodiesel gets cold enough, it turns into a solid and will not flow at all. Biodiesel made from virgin oil stays fluid at lower temperatures than biodiesel made from waste oil. Most biodiesel users find that they have difficulty with their fuel when temperatures fall below freezing. Some people get around this problem by adding 30 percent petrodiesel to their biodiesel. Others add anti-gel agents to winterize the fuel. Some people worry that biodiesel will decay rubber parts within the fuel system. This can happen, but rubber parts have been uncommon since the 1980s and are easily replaced in any case.

Environmental impact of biodiesel

Biodiesel is much better for the environment than petrodiesel. It is completely biodegradable and non-toxic. It poses no threats to human health. It does not emit the pollutants produced by fossil fuels, which makes it very appealing for areas trying to improve air quality. It does not emit the black smoke that petrodiesel does. It is safe to store and transport. Its flash point (the temperature at which it will catch fire) is over 257°F (125°C), as opposed to 136°F (58°C) for petrodiesel, so it is harder to start a fire with biodiesel.

Making biodiesel is a good way to recycle waste oil that would otherwise end up in a landfill. Though there is a large amount of waste vegetable oil (WVO) produced daily, it is nowhere near the amount of diesel fuel used every day. Likewise, waste animal fat is not nearly plentiful enough to meet major energy needs. Some WVO is already converted into other products, such as soap. Nevertheless, a large amount of WVO and animal fats currently end up in landfills and could profitably be converted to biodiesel.

Economic impact of biodiesel

Biodiesel can function as a substitute for petrodiesel, so economic costs depend partly on what a person or company would be spending on petrodiesel. Nations that use a great deal of biodiesel do not have to purchase petrodiesel from foreign suppliers, which can mean a tremendous savings. The cost of biodiesel to individual consumers varies depending on where they are and how they get it. In Europe biodiesel is widely available and in many places is less expensive than petrodiesel. In the United Kingdom, taxes on biodiesel are lower than those on petrodiesel. Biodiesel is still more expensive than petrodiesel in the United States, but use is increasing and the price is dropping as a result. Several states are considering laws that would require all petrodiesel to include a portion of biodiesel. There are tax credits available to businesses that use biodiesel.

The first users of biodiesel made their own, and this practice is still popular. People who make their own biodiesel using freely donated waste vegetable oil claim to be able to run their vehicles on just a few dollars a month. Integrating biodiesel into an existing petrodiesel infrastructure is not expensive because very few things need to be changed. The equipment is the same, and no training is necessary. Because biodiesel is better for engines than petrodiesel, using biodiesel can make an engine last longer and break down less often. Making biodiesel commercially is becoming more profitable as more people purchase it. Thus, producers are taking a much greater interest in making biodiesel for sale as it becomes more profitable.

Issues, challenges, and obstacles of biodiesel

Biodiesel is growing in popularity. In 2006 it is far past the experimental stage and is in the process of being accepted as a mainstream fuel. But public officials and consumers are sometimes resistant to change for various reasons. Public transportation fleets must often coordinate their fuels so that they all use the same ones, which can make it difficult to introduce new fuels. Politicians make promises to various industries, which can also hamper efforts to introduce biofuels.


It is possible to power a diesel engine on plain vegetable oil. This usually requires the engine's owner to modify it slightly. There are two main types of vegetable oil fuels. Straight vegetable oil, or SVO, is exactly what it seems: vegetable oil, just like the kind available in the grocery store. In fact, many people buy vegetable oil from the grocery store to use as fuel. SVO will work in a diesel engine, though for best results the engine needs to be modified. The second type is waste vegetable oil, or WVO, which is oil that has already been used for cooking and can no longer be used for that purpose. Fast food establishments and potato chip factories produce huge amounts of WVO. This oil can be collected, purified, and used as SVO fuel. Waste vegetable oil can also be used as animal feed.

Both SVO and WVO can be used just as they are in engines modified to use them. They can also be mixed with diesel fuel or kerosene to combine the benefits of biofuels with the advantages of fossil fuel. Or they can also be converted to biodiesel.

Current use of vegetable oil fuels

Vegetable oils are mainly used in diesel engines. If the vegetable oil is not converted into biodiesel, which can be used in an ordinary diesel engine, the engine must be modified to get the best results.

SVO can run an engine on its own. So can WVO, which functions just like SVO once it has been cleaned. There are two main ways to convert an engine to run on SVO. One way is to use a single tank fitted with different filters, temperature controls, injectors, injector pumps, glow plugs, and a fuel pre-heater. Some single-tank systems can run on SVO, biodiesel, or regular petrodiesel. Other vehicles use a two-tank system; one tank holds petrodiesel or biodiesel, and the other contains SVO. The vehicle uses the tank holding diesel to start and warm the SVO and then switches to the SVO to provide power. Using SVO without modifying the engine will gradually result in clogged injectors.

It is possible to use SVO in a diesel engine without modifying it. This is not a practical long-term practice, however. The filters and fuel injectors gradually get clogged up and can cause engine failure.

Some people mix vegetable oil into diesel fuel or kerosene. These blends can contain various proportions of vegetable oil to petrodiesel, mixed according to personal preference and what is available. Though mixed fuel can work in an ordinary diesel engine, the best results come from using a two-tank system such as the one that can be used with SVO.

People who use biofuels often see mixes as a poor compromise. The engine still must be modified as if it were running on SVO, and the user is still consuming fossil fuels and emitting pollutants. On the other hand, mixing SVO with petrodiesel or kerosene offers some advantages over straight SVO. It avoids some pollution caused by burning straight fossil fuel, and the engine starts better in cold weather than when it's powered by either biodiesel or SVO.

Benefits and drawbacks of vegetable oil fuels

Using vegetable oil for fuel has many benefits. It is environmentally clean. If WVO is used, it prevents that oil from ending up in a landfill. It is not a fossil fuel, so its use can make regions more self-sufficient and less dependent on foreign sources of oil. People who use SVO as fuel tend to be independent experimenters; they especially enjoy the sense of freedom they get from using fuel that they can acquire themselves.

But using SVO or WVO in engines requires modifying them, which is inconvenient and expensive. SVO is not a direct substitute for diesel, unlike biodiesel, and cannot be used alternately with petrodiesel. Even though using SVO does not require the user to make biodiesel, it still must be prepared before it is burned; WVO especially must be cleaned of all food particles.

Liquid biofuels have a higher viscosity (a level of stickiness) than diesel fuel. This means they do not flow as well in the engine, especially at cold temperatures. Below about 40° Fahrenheit (4.5° Celsius), vegetable oil can solidify, making it useless.

One side effect of using cooking oil in diesel engines is that the exhaust fumes smell like cooking food. Most people do not consider this a major drawback, especially because diesel exhaust fumes also have an odor.

Environmental impact of vegetable oil fuels

SVO is a very clean fuel. SVO mixed with diesel or kerosene is not as clean and still releases the emissions of fossil fuels. Yet it does reduce somewhat the amount of fossil fuels consumed and burned.

In the year 2000 the United States produced over 11 billion liters of waste vegetable oil, most of it from deep fryers in potato chip factories and fast food restaurants. This oil is usually thrown away. Using WVO for fuel is an excellent way of getting rid of waste oil and avoiding the consumption of fossil fuels. On the other hand, vegetable oil must come from plants, and these plants must be grown. Substituting vegetable oil for fossil fuels will require as much land as possible to be devoted to growing crops that can produce it.

Economic impact of vegetable oil fuels

The economics of using vegetable oil for fuel depend somewhat on whether the oil fuel is new or used. Purchasing new vegetable oil can potentially cost more than purchasing diesel fuel. However, in many cases WVO is free for the taking. Factories and restaurants must pay to dispose of their WVO in the garbage. Therefore, they are often willing to donate it to anyone who wants to collect it. Some enterprising individuals retrieve WVO from local shops and use it in their vehicles, either straight or converted to biodiesel. These people can run their cars for as little as $8 a month, much less than the cost of fueling a gasoline- or diesel-powered vehicle. Even purchasing WVO is inexpensive; in 2003 it sold for about 40 cents a gallon.

Issues, challenges, and obstacles of vegetable oil fuels

SVO, WVO, and animal fats are popular substances for experimentation. There are many people who would love to be able to run their vehicles and equipment on unmodified cooking oils. As fossil fuels grow more expensive, more commercial enterprises have taken an interest in alternative fuels. Most of this interest, however, seems to be focused on biodiesel, not on SVO. Biodiesel is a much more practical alternative to petrodiesel than SVO because it does not force people to change their vehicles. For that reason, SVO as a fuel by itself is a less likely alternative fuel than biodiesel.

Do Not Steal that Oil!

Even though WVO is often freely donated to people who ask for it, it is a bad idea to take WVO directly from a dumpster without asking first. The WVO usually belongs to the company that owns the dumpster, and anyone who takes oil out of it without permission can be charged with stealing. The best approach is to ask individual restaurant owners if they would mind pouring their used oil back into the containers it came in and putting it out for collection by people who want it for fuel. Oil fuel hobbyists claim that Asian restaurants are often a good source of oil because they have the best quality WVO. Hamburger restaurants often have the worst quality WVO. Biodiesel hobbyists also emphasize the importance of maintaining a good relationship with the restaurants that supply them with WVO.


Biogas is a mixture of gases produced by the fermentation of waste material in anaerobic (without air) conditions. Biogas technology is also called "anaerobic digestion technology." The gases include methane, carbon dioxide, and trace gases such as ammonia, nitrogen, hydrogen, sulfur dioxide, and hydrogen sulfide. Generally the methane content is between 60 and 70 percent. Methane works like natural gas drilled from the ground as a fossil fuel, but unlike natural gas, biogas is renewable. Many people think biogas is an ideal form of energy because it turns waste material into a source of power that produces few pollutants.

Biogas develops in nature all the time. The distinctive smell of swamps is caused by marsh gas, or methane and other gases that develop when vegetation that settles to the bottoms of wetlands is anaerobically digested by bacteria. The manure of cattle in particular contains a great deal of biogas produced by bacteria living in their intestines. These bacteria digest the cellulose in the plant matter that the cattle eat and release methane and carbon dioxide. To collect biogas from manure, a processor collects the manure in a closed tank called a digester. The bacteria digest the cellulose through anaerobic digestion and release methane and other gases into the tank. The biogas can then be collected or piped to wherever it is needed. Biogas can also be made from garbage in landfills or from sewage. Scientists have been developing many different techniques of capturing and using biogas.

Current uses of biogas

Because biogas contains so much methane, it can be used to power appliances that run on natural gas. In many parts of the world biogas is used as a substitute for natural gas, either to run appliances and vehicles or as a source of electricity. A digester on a large dairy farm can produce between four and six million cubic feet of biogas annually, resulting in 124,000 to 198,000 kilowatt-hours of electricity.

Biogas is commonly used in rural areas where there is a ready supply of manure or garbage. In the Netherlands and Denmark biogas is a common source of power. In the United States some dairy farms have begun using biogas systems as a way of managing their increasing manure supplies. In Canada, landfill gas is a major source of energy for electricity generation.

Benefits and drawbacks of biogas

Biogas offers many benefits. It is a good way to get rid of waste materials. The energy it produces is powerful and clean. It does not pollute groundwater or air. Methane can power appliances and vehicles and can be used to generate electricity. Biogas is also quite safe. Homemade biogas does not present any risk of explosion because the gas accumulates slowly and dissipates (goes away) quickly if it leaks instead of pooling on the ground as gasoline does.

But biogas has only one-half the heating value of natural gas. There is not much biogas infrastructure available, so the use of biogas is limited. In addition, using biogas requires the installation of expensive new equipment.

Impact of biogas

Biogas appears to offer many environmental benefits. It uses waste materials that would otherwise take up space in landfills or pollute the landscape to generate fuel. The fuel it creates is far less polluting than most fossil fuels. When methane burns, it produces carbon dioxide and water, so it does not cause the same degree of air pollution as fossil fuels. It does not produce the sludge that results from coal-burning emissions. Burning methane releases no ash and only small amounts of sulfur dioxide or nitrogen oxides and does not contribute to the formation of smog. Methane and carbon dioxide, the main components of biogas, are themselves pollutants, but burning the biogas prevents these pollutants from being released into the atmosphere.

On an economic level, biogas technology can save individual producers a great deal of money on power costs. For example, a dairy farm that implements biogas technology can save thousands of dollars every year on electricity, heating, and manure pit maintenance. On the other hand, installing the technology is very expensive; it can take several years to earn back the investment. Maintenance costs are also a factor. Some estimates predict that it would take a dairy farm more than five years to earn back the investment in a biogas operation, which is too long for most businesses to find financially acceptable.

Issues, challenges, and obstacles of biogas

Biogas technology is still being developed. It is difficult to persuade people to invest a great deal of money in equipment to collect and use biogas when they already have good equipment that uses fossil fuels. Few people know about biogas so there is not yet great demand for biogas appliances. China has used biogas from sewage fairly widely in the mid-twentieth century, on cooperative farms. There were successes, but the appliances have been difficult to maintain.


It is possible to use alcohol to power engines, either by itself or mixed with gasoline or other fuels. Ethanol is the most common of the alcohols that can be used to power engines. Ethanol is also known as ethyl alcohol and is the same kind of alcohol found in alcoholic beverages. It is clear and looks like water. but it is not the only one.

Methanol, or methyl alcohol, and butanol can also be used as fuel. Methanol is an alcohol made from fermentation of cellulose or from fossil fuels, particularly methane. It is used mainly as a fuel for race cars. Butanol is an alcohol made from fermenting plants. It can also be used as a fuel for internal combustion engines. Propanol is another kind of alcohol fuel. Methanol, butanol, and propanol all have the disadvantage of being toxic to humans and highly volatile (explosive). Ethanol is also volatile and toxic, but the toxicity level is lower, and so is considered more acceptable. Regardless of which one is used, alcohol combined with gasoline results in a fuel called gasohol.

Blends of gasoline and alcohol are often identified by abbreviations that combine the letter E with a number indicating the percentage of ethanol in the blend. For example, E10 contains 10 percent ethanol, E5 contains 5 percent ethanol, and E7 contains 7 percent ethanol.

How to make ethanol

Ethanol can be made from a large number of organic materials, including corn, wheat, grass, sugarcane, seaweed, cellulose left over from making paper, and nearly any other source of carbon. It can also be made from leftover petroleum feedstocks.

To make ethanol, a producer grinds up the feedstock, such as corn. This exposes the starch in the plant material. The ground-up corn is mixed with water and enzymes and heated to convert the starch to sugar. The producer adds yeast to the mix to help the sugars ferment into ethanol. The alcohol is then removed by a process called distillation: The producer boils the mixture so that the alcohol evaporates and then catches the alcohol in a container and cools it back into a liquid.

Sugarcane is the best source of ethanol because it naturally contains the sugars that ferment into alcohol. Scientists are working on better methods of making ethanol from cheaper biomass materials, such as wood and straw. It is harder to make ethanol from these substances because they do not release their sugars as easily as corn or sugarcane.

Current uses of ethanol and other alcohol fuels

Ethanol and other alcohols can be used to power motor vehicles instead of gasoline. In almost all cases the ethanol is mixed with gasoline. Gasoline-powered vehicles have no difficulty using gasoline that contains small amounts of ethanol. Generally this mix must contain at least 10 percent ethanol to qualify as gasohol. Gasohol is widely available in Denmark, Brazil, and the American Midwest. The state of Minnesota requires all gasoline sold there to contain at least 10 percent ethanol.

Increasing numbers of light trucks are sold as flexible fuel vehicles, capable of burning a variety of fuels, including mixes of gasoline and ethanol and other alternative fuels such as P-Series fuels. Vehicles that can run on pure ethanol are rare and require special engineering to function, which is why fuels for FFVs usually contain at least some gasoline.

Do Not Drink the Ethanol

Humans long ago figured out how to make ethyl alcohol. It is fairly easy to do; any source of sugar will create the fermentation that results in drinkable alcohol. Ethanol producers, however, ruin their liquid for human consumption. First they add benzene to the ethanol to remove any water that might be lingering in it, which would impair its ability to function as a fuel. Drinking ethanol with benzene in it can damage the liver. Before the ethanol is sold, the producer "denatures" it by adding some poisonous substance to it. A popular choice for this poison is methanol, also known as methyl alcohol or wood alcohol, which is terribly toxic to humans.

One common ethanol blend is called E85, which contains 15 percent gasoline and 85 percent ethanol. Producers add this small amount of gasoline to the ethanol to make the vehicle start better in cold weather. E85 is generally priced at about the same level as gasoline.

Many scientists also hope that ethanol can be an important source of fuel for fuel cells in the future. Ethanol and methanol can both be used as fuels in fuel cells, though ethanol is a less efficient source than methanol. Fuel cells would use the energy stored and released by hydrogen.

Ethanol also has many other uses. It has a low melting point, so it can be added to liquids as an antifreeze. In addition, it can be added to gasoline as an anti-knocking agent. It can also be a safe replacement for MBTE, a fuel additive that has been found to present environmental problems.

Benefits and drawbacks of ethanol

Because ethanol can be made from so many different substances, it can be made nearly anywhere from nearly any raw material. Most ethanol is made from corn and sugarcane, but scientists have been investigating other sorts of biomass as a source of ethanol. Cellulose from grass or hay, cardboard, paper, farm wastes, and other waste products could potentially produce much more energy per source than is currently possible, with the side benefit of using up organic waste matter that would otherwise be thrown into landfills.

Ethanol is less flammable than gasoline and thus may be less of a fire hazard. When it does catch on fire, however, its flame and smoke are very hard to see, which presents another set of risks. Ethanol and other alcohol fuels dissolve in water, so water will put out alcohol fires, unlike gasoline fires, which require special fire extinguishers.

Ethanol will dissolve rubber and plastic, so pure ethanol cannot be used in unmodified gasoline engines. Also, ethanol's octane rating is higher than gasoline, which can require modifications to spark timing, carburetor jets, and starting systems. Gasohol does not present the same problems and can be used in ordinary vehicles without modification.

Environmental impact of ethanol

The environmental implications of making and using ethanol are the source of much debate. While burning ethanol has many environmental advantages over gasoline, particularly in reduced air pollution, the production of ethanol can be decidedly un-green.

Ethanol does not emit the same greenhouse gases that gasoline does. When it burns, it emits only carbon monoxide and water. Air quality improves quickly when ethanol replaces gasoline. Minnesota, which requires all its gasoline to contain 10 percent ethanol, has met Environmental Protection Agency (EPA) carbon monoxide targets partly because the ethanol has reduced the amount of gasoline burned.

Ethanol has the potential to reduce garbage in landfills. If ethanol can be made from waste paper or wood, that would supply a use for what has historically been a big source of trash. On the other hand, the process of creating ethanol from waste cellulose itself creates waste products that cannot be used.

Ethanol production does come with some environmental problems, however. Many experts contend that ethanol made from corn is actually worse for the environment than fossil fuels. This is because it can take more energy to raise the corn and make ethanol than the resulting ethanol can itself provide. Commercial farms use vast amounts of fossil fuels in planting, harvesting, and fertilizing their crops and making ethanol. In the United States the corn ethanol industry has been heavily subsidized (supported) by the government, which makes it inexpensive to manufacture ethanol from corn crops. If, however, the industry uses more energy to make ethanol than ethanol can provide, then ethanol is in fact not a workable alternative to gasoline.

Economic impact of ethanol

For states that produce corn, ethanol adds a great deal of value to local corn crops. For example, in Minnesota about 14 percent of the corn crop is made into ethanol. Exporting ethanol instead of raw corn doubles the value of the corn. Many midwestern states have subsidized ethanol production from corn since the 1970s, when Middle Eastern nations instituted an oil embargo in 1973. The U.S. federal government has guaranteed loans to build ethanol plants and since 1978 has made gasohol exempt from (free of) certain taxes.

For individual consumers, the cost of running a vehicle on gasohol is about the same as running it on gasoline, though that varies widely with the price of oil. As oil prices rose in the early 2000s, ethanol became comparatively cheaper. During this time, as it became apparent that biofuels were becoming widely accepted, production of ethanol increased very rapidly around the world. Ethanol appeared poised to become a giant and lucrative (money-making) industry.

Issues, challenges, and obstacles of ethanol

In areas where it is easy to make ethanol, such as Brazil, with its ample water and warm climate that makes it easy to grow sugarcane, ethanol is an entirely viable fuel. The nation powers its ethanol plants by burning bagasse, the sugarcane solids, which can generate enough power to have some left over. Hydroelectric power is also a good way of making ethanol without using fossil fuels.

The main source of debate about ethanol is whether or not making and using ethanol is actually more efficient than using straight fossil fuels. The problem is that producing ethanol consumes a great deal of energy. First, a farmer must grow the grain or sugarcane that provides the source of most ethanol, which takes up agricultural land and consumes water and fertilizers, many of them made from fossil fuels. The process of making and transporting ethanol consumes energy. Natural gas is a commonly used fuel in the distillation process, and it is itself a fossil fuel. Critics of ethanol have long insisted that making ethanol from corn costs more energy than the resulting ethanol can produce.

Critics also claim that corn-growing states in the United States have been emphasizing the importance of corn-based ethanol to get subsidies from the federal government that are far out of proportion to ethanol's value to the economy. Corn growers have exerted a great deal of political power, and agricultural states have used ample influence in national politics. Critics fear that ethanol producers will persuade the government to invest in their industry despite the fact that it may not have real environmental benefits.


P-Series fuels are a new type of renewable fuel that use up an extremely common and little-valued resource: garbage. P-Series fuel is a blend of 35 percent natural gas liquids, 45 percent ethanol, and 20 percent methyltetrahydrofuan (MeTHF). The natural gas liquid is a substance called pentanes-plus, a liquid left over from the processing of natural gas, with butane added in winter months. MeTHF is made from biomass such as waste paper, food wastes, agricultural waste, or yard waste, and serves as a co-solvent (substance that turns another into liquid). The fuel is a colorless clear blend with octane between 89 and 93, the same octane as gasoline. It can be formulated for winter or summer use. It can be used alone or mixed with gasoline in a flexible fuel vehicle (FFV).

P-Series fuel was developed in the 1990s by Princeton University thermonuclear physicist Stephen Paul. He wanted to create a substitute for gasoline and thought that using garbage as fuel could work. He gave the fuel its name in honor of Princeton University. Paul and fellow investors have bought a sludge plant in New Jersey that they intend to use to make enough P-Series fuel to power about fifteen thousand vehicles.

Current uses of P-Series fuels

P-Series fuels are not currently widely used. They are still quite new, and no car manufacturer has yet produced a "P-Seriesspecific" FFV. If consumers begin buying these fuels, however, they could be a good substitute for gasoline.

Benefits and drawbacks of P-Series fuels

Using P-Series fuels has several benefits. It decreases the amount of petroleum used to power vehicles. It makes use of waste that would otherwise have to be placed in a landfill, incinerated, or transported to some other location. P-Series fuels are easy to use. Fueling an FFV with P-Series fuel is identical to fueling a vehicle with gasoline. There is no need to monitor fuels because gasoline and P-Series fuels will work mixed together, so a car owner can fuel up at ordinary gas stations or at P-Series pumps without thinking about which is which. This is especially useful when traveling to areas where P-Series fuels are unavailable.

But P-Series fuels cannot be used in vehicles designed to burn gasoline only. FFVs designed to burn methanol or ethanol can burn it, but ordinary cars cannot. P-Series fuels are slightly more efficient than gasoline, but in practice, mileage for vehicles using P-Series fuels is about 10 percent less per gallon than those using gasoline.

Environmental impact of P-Series fuels

The feedstock used to make MeTHF is chemically digested by the process of making it; as a result, the raw material is completely consumed and no emissions enter the air. Burning P-Series fuels in vehicles releases many fewer emissions than burning fossil fuels. In fact, P-Series fuels were added to the list of alternative fuels under the U.S. Energy Policy Act in 1999.

Economic impact of P-Series fuels

In 2003 P-Series fuels cost about $1.49 per gallon, which was then slightly lower than gasoline. Because P-Series fuels provide slightly less power than gasoline, the resulting operating cost is about the same for a P-Series-powered car and a gasoline-powered car. It is possible that as fossil fuels become more expensive, P-Series fuels will seem less expensive.

Manufacturers of P-Series fuels usually buy their natural gas liquids and ethanol in bulk from companies that produce those products. MeTHF is made by hydrolysis; the process basically involves mixing garbage with some acid and heat and agitating (mixing) it until it turns into liquid. The feedstock, or raw material, for MeTHF actually has a negative cost, because it is made from materials that would otherwise cost a city money to dispose of. As a result, it is fairly easy for a P-Series plant to recoup (get back) its investments and become profitable. Small P-Series plants are viable because it is not very expensive for them to operate. This makes it possible for many small P-Series plants to be distributed throughout a geographic area. This distribution would have the added advantage of preventing any one location from becoming the region's dumping ground.

Issues, challenges, and obstacles of P-Series fuels

P-Series fuels are still very new and appear to be unproven. Producers of the fuel have a hard time finding investment capital for their enterprises because banks or companies investing in the project want to be sure they can collect a return on their money. The developer of the fuel insists that it burns cleanly and that it will in fact be inexpensive to make. Without a provable record, however, it is difficult to persuade investors that this is true.

For More Information


Carter, Dan M., and Jon Halle. How to Make Biodiesel. Winslow, Bucks, UK: Low-Impact Living Initiative (Lili), 2005.

Pahl, Greg. Biodiesel: Growing a New Energy Economy. Brattleboro, VT: Chelsea Green Publishing Company, 2005.

Tickell, Joshua. From the Fryer to the Fuel Tank: The Complete Guide to Using Vegetable Oil as an Alternative Fuel. Covington, LA: Tickell Energy Consultants, 2000.


Anderson, Heidi. "Environmental Drawbacks of Renewable EnergyAre They Real or Exaggerated?" Environmental Science and Engineering (January 2001).

Parfit, Michael. "Future Power: Where Will the World Get Its Next Energy Fix?" National Geographic (August 2005): 2-31.

"Stirrings in the Corn Fields." The Economist (May 12, 2005).

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