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Farmers are now being offered opportunities not only to produce on their land as they have always done, but now to enter other business ventures on their land by generating renewable energy. Wind power is one of the most rapidly growing renewable energy types in the world today. From 1998 to 2002, its annual growth rate worldwide was 32 percent. The DOE's Wind Powering America initiative has set a goal of producing 5 percent of the nation's electricity from wind by 2020. The DOE projects meant to achieve this goal will provide $60 billion in capital investment to the rural United States, $1.2 billion in new income to farmers and rural landowners, and 80,000 new jobs during the next 20 years.

Wind power can provide an important economic boost to farmers. Large wind turbines typically use less than half an acre of land, including access roads, so farmers can continue to plant crops and graze livestock right up to the base of the turbines.

Another form of clean energy that can be used on a farm is solar energy. According to the Union of Concerned Scientists (UCS), solar energy can be used in agriculture in a number of ways. One of the simplest ways is to design or renovate buildings and barns to use natural daylight instead of electric lights. Dairy operations using long day lighting to increase production can save money with skylights and other sunlighting options. Solar energy can also be used to warm homes and livestock buildings. Active solar heating systems, which use heat boxes and fans, can warm the air, saving fuel. Passive solar designs, where the building is situated to take advantage of the Sun automatically, are usually the most cost-effective approach.

The Sun can also be used to dry crops and grain, as well as heat greenhouses. Sunlight can also be used to generate electricity. Photovoltaic (PV) panels are often a cheaper option for providing electricity and are often used successfully for pond aeration, small irrigation systems, and remote livestock water supply.

Conversion technologies also exist now to convert perennial grasses into biofuels. According to the Pew Center on Global Climate Change, improvements in conversion technology could be achieved with additional research. They believe that dedicated energy crops could supply up to 12 percent of the current U.S. energy demand without significantly raising food prices. The biomass could be used to produce heat, power, and transportation fuels.

The largest use of biomass for energy today is cogeneration of steam and electricity by the forest products industry. Ethanol made from corn grain is the largest source of biomass-derived fuel in the transportation market. The Pew Center has calculated that crops could be grown specifically for use in energy production, with perennial grasses being the most commonly used vegetation source. They also support the idea that if aggressive research and development programs are put in place and move forward and successfully increase yields of bioenergy crops while reducing the current costs of biomass-to-fuel technologies, biomass from agricultural sources could supply as much as 19 percent of the total current U.S. demand for energy. This includes energy from dedicated energy crops, dual-purpose crops (such as corn and soybeans),

A combine harvesting corn to be converted into biofuels (Warren Gretz, DOE/NREL)

agricultural residues, and animal wastes. This amount of bioenergy represents an amount equivalent to more than 80 percent of the petroleum energy used for transportation in the United States.

The U.S. ethanol industry has grown from being almost nonexistent in the late 1970s to a current production level of more than 2.8 billion gallons—which equals about 2 percent of the energy consumed on America's highways each year. Ethanol made from corn grain is the largest source of biomass-derived fuel in the U.S. transportation market. Grain ethanol is made by converting the starch in the corn kernel to sugar and then using yeast to ferment the sugars to ethanol.

USDA and DOE researchers published a joint study of the potential magnitude of biomass supplies. They conservatively estimated the maximum economically feasible supply of ethanol from cornstarch at approximately 10 billion gallons (38 billion liters) per year. Some critics have argued that the process of creating ethanol from cornstarch requires more energy to make than it was worth, but according to the Pew Center, over the past 20 years, technology has advanced to the point that it provides more power than it takes to produce, making it a positive energy source.

Ethanol is also made from sugarcane. The energy balance for sugar-derived ethanol is even better than that for corn-based ethanol. It has a better energy balance because its bagasse (biomass that remains after the sugar has been extracted from the cane), rather than a fossil fuel, is used as the energy source in the conversion process. For corn-starched derived ethanol, fossil fuels are used in the conversion process.

A Hawaiian biomass gasifier that uses residue from the nearby sugarcane mill as its energy source (Rich Bain, DOE/NREL)

Agricultural areas are now considered prime targets for producing four types of renewable energy: biodiesel, biomass, ethanol, and biogas. The diesel engine, created in 1892 by Rudolf Diesel, was originally designed to run on peanut oil. Today, diesel engines can be run on vegetable oil, even if it has already been used for cooking. Over the years, this has generated an interest in alternative fuels and the subsequent creation of biodiesel. Biodiesel is comprised of methyl esters of long-chain fatty acids and is derived from vegetable oil or animal fat by removing the glycerin in a reactive refinery process. Today, with little or no modification, diesel engines can run on a blend of petroleum diesel and biodiesel.

Biodiesel can also be burned in furnaces to heat homes, hothouses, or barns with only slight modifications to hose connectors and nozzles. The benefits of biodiesel include better air quality because of a reduction in particulates, volatile organic compounds, sulfur dioxide, carbon monoxide, and mercury. Biodiesel is also biodegradable and nontoxic. It also has increased lubricity and therefore reduces engine wear. The recent availability of biodiesel has improved, and prices are at least competitive, but often better, than regular diesel prices.

Biomass consists of a family of fuels whose plant-based feedstocks are either burned directly—such as wood or woody crops, corn, and chipped/palletized residue—or refined so that fuel in the form of sugar and starches are separated from the cellulose.

Cellulose—the primary component in biomass fuels—is found in all plants. When processed, it is the cellulose that provides the energy for heating, transportation, and electrical generation. Many types of materials can be converted to biomass, such as wood, wood crops, waste wood, wood residue, grains, grasses, and agricultural residue.

Biorefineries for biomass are currently being researched as many scientists are focusing on them, seeing their importance long into the future. In the future, scientists expect to be able to extract from plants chemicals and fuels through the depolymerization of the cellulose and hemicellulose and the conversion of lignin to fuel and synfuels. While the technology is not ready yet, the pressure to develop this, in light of global warming and the need for greenhouse gas reductions, as well as opportunities for a new farm economy, should lead to rapid development in this area.

Napier Grass

Napier grass (also called elephant grass) is used for the production of ethanol. (Warren Gretz, DOE/NREL)

Ethanol, like biodiesel, is a biofuel that can serve as an alternative to petroleum fuels, although it can only be added to or substituted for gasoline, not diesel. Most of today's ethanol is produced from starch-based feedstock such as corn or sugarcane. It can also be produced from cel-lulosic feedstock such as fast-growing grasses like the perennial switchgrass or short-rotation woody crops like poplar.

Biogas is a gas produced by the biological breakdown of organic matter in anaerobic conditions. It originates from biogenic material and is a type of biofUel. One type is produced by the anaerobic digestion or fermentation of biodegradable materials such as sewage, manure, municipal waste, or energy crops. The gas is composed mostly of carbon dioxide (CO2) and methane. Another principal type of biogas is called wood gas, which is created by gasification of wood or other biomass. This biogas is composed of nitrogen, hydrogen, and carbon monoxide, with small amounts of methane.

Biogas is commonly used for heating, to run heat engines, and to generate mechanical or electrical power. It can also be compressed like natural gas and used as a fuel in cars. Biogas is also referred to as swamp, marsh, or landfill gas.

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