Energy crops

Energy crops are those grown to produce biofuels or to be combusted to produce energy. Corn, an annual crop, is one of the most widely grown and used energy crops, although perennial crops such as grasses and trees are also used.

Organic matter including trees, crops, crop waste, and algae are examples of biomass, or renewable sources of stored energy from the sun. Burning biomass releases the chemical energy as heat. Biomass can also be converted to other forms of useable energy, such as ethanol.

Some energy crops, such as wood, are used in their natural state as fuel, while oil is extracted from crops such as sunflowers. Other crops are converted to biofuels. Ethanol or grain alcohol is a biofuel made from plant grains such as barley, corn, and wheat by fermenting sugars with yeast. It is often combined with gasoline to produce a fuel that burns with fewer emissions. As of 2022, the United States produced almost 15 billion gallons of ethanol annually.

Background

Biofuels were used at least as early as the eighteenth century. Vegetable oils and fats were burned for illumination, and alcohol was used to fuel stoves to provide heat. Some early inventors of engines used alcohol or ethanol as fuel.

Biofuels became increasingly popular during the twentieth century. Germany produced potato crops to make alcohol fuel. Ethanol was used in lamps and powered home appliances. In the United States, automaker Henry Ford responded to an oil shortage during World War I (1914–1918) by designing automobiles and tractors that could run on alcohol or gasoline. Brazil and the Philippines processed sugarcane to make alcohol biofuel and reduce their dependency on foreign fuels. Brazil built the first biofuel plant in 1927, and within ten years, ethanol accounted for 7 percent of the country's fuel use.

Ethanol was important to the United States during World War II (1939–1945), but it was largely sidelined when oil from the Middle East became plentiful and inexpensive. Political instability in the Middle East led to oil embargoes during the 1970s and caused US leaders to support ethanol production. This cycle continued whenever the cost of oil increased.

During the twenty-first century, a number of issues swirled around biofuels. The United Nations was concerned that growing food-based energy crops could divert farmland from food production and lead to food shortages. The issue of global climate change also caused concerns because burning fossil fuels contributed carbon to the atmosphere, so world leaders again focused on ethanol as a cleaner alternative. However, the world continued to depend on biofuels. By 2024, nearly 200 billion liters of biofuel were produced in the world each year.

Focus in the twenty-first century also shifted to the types of energy crops that should be developed. Some researchers focused on perennial crops that grow quickly, are noninvasive and resistant to pests, and are easy to harvest, store, and transport. The biofuels industry also developed new enzymes and yeasts to boost production.

Overview

Energy crops have become increasingly important in the twenty-first century, as concerns about global climate change have grown. Efforts to reduce atmospheric carbon have led automakers to reconsider Henry Ford's early ideas about alcohol. Many have produced flexible-fuel vehicles, or flex-fuel vehicles, which are fueled by gasoline or a blend of gasoline and ethanol. E85, or 85 percent ethanol to 15 percent gasoline, is a common blend. Many ordinary vehicles are fueled with E10, a 10 percent ethanol blend that improves emissions quality and increases octane.

Although grains have been the most produced energy crops for much of the twentieth and early twenty-first centuries, researchers have been working to develop ways to use other plant materials, in particular grasses and other non-food crops. This has been especially important in the United States, where such crops are readily grown. Plants can be used as biofuel because they contain carbohydrates, which are made of sugar molecules. Sugar in some crops, such as grains, is easily obtained through fermentation, in which microorganisms produce ethanol by metabolizing plant sugars. Other parts of plants, such as stems and leaves, also contain sugar that is less easily accessed. All plants contain sugar molecules within carbohydrates, which contain carbon, hydrogen, and oxygen. Plants create carbohydrates using sunlight through a chemical process called photosynthesis. The simple carbohydrates, or simple sugars, in plants are monosaccharides. The complex carbohydrates or complex sugars, including starches, cellulose, and hemicellulose, are polysaccharides. Researchers have found ways to break down the long molecular chains of the complex carbohydrates in plants, which releases the sugars. Such developments allow them to produce cellulosic ethanol from material such as corn stover, or the cobs, leaves, and stalks of the corn plant.

Trees have proven to be a useful renewable fuel crop. Varieties that regrow readily after they are cut are the most useful. Trees such as cottonwood, poplar, sweetgum, sycamore, and willow grow quickly and may provide 40 feet (12 meters) of regrowth in less than eight years. They can be harvested multiple times over their life spans of up to twenty years with minimal effort.

Energy crops can benefit farmers and consumers. They can provide farmers with an additional market for crops and additional financial support because the government pays many American farmers to grow corn for ethanol production. This funding can help support more jobs. At the same time, producing these crops helps the United States become more energy independent because it reduces dependence on foreign oil and produces less pollution.

Growing energy crops can have some drawbacks as well. Corn, the most common crop used to produce ethanol, requires a great deal of fertilizer and herbicides. Some experts believe the cost of producing corn for fuel could become too high, and many have concerns about the effects to the environment from producing and using large quantities of synthetic fertilizers. Annual crops require more labor to produce than perennial crops. Ethanol also poses some environmental risks. When it is burned in a combustion engine, ethanol produces formaldehyde and other substances that increase ozone, a pollutant, at ground level.

Bibliography

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