Most ethanol in the United States is produced from starch-based crops by dry- or wet-mill processing. Dry-milling is a process that grinds corn into flour and ferments it into ethanol with co-products of distillers grains and carbon dioxide.
Wet-mill plants primarily produce corn sweeteners, along with ethanol and several other co-products such as corn oil and starch. Wet mills separate starch, protein, and fiber in corn prior to processing these components into products, such as ethanol.
Making ethanol from cellulosic feedstocks—such as grass, wood, and crop residues—is a more involved process than using starch-based crops. There are two primary pathways to produce cellulosic ethanol: biochemical and thermochemical. The biochemical process involves a pretreatment to release hemicellulose sugars followed by hydrolysis to break cellulose into sugars. Sugars are fermented into ethanol and lignin is recovered and used to produce energy to power the process. The thermochemical conversion process involves adding heat and chemicals to a biomass feedstock to produce syngas, which is a mixture of carbon monoxide and hydrogen.
Syngas is mixed with a catalyst and reformed into ethanol and other liquid co-products. More than , flights have used biofuel, but the amount of aviation biofuel produced in accounted for less than 0. In shipping, too, adoption of biofuel is at levels far below the targets set by the International Energy Agency.
Renewable natural gas, or biomethane , is another fuel that potentially could be used not only for transportation but also heat and electricity generation. Gas can be captured from landfills, livestock operations, wastewater, or other sources.
This captured biogas then must be refined further to remove water, carbon dioxide, and other elements so that it meets the standard needed to fuel natural-gas-powered vehicles. A variety of materials, or feedstocks, can be used to make biofuels. Though corn and sugarcane are well-established ethanol feedstocks, the process of growing the crops, making fertilizers and pesticides, and processing the plants into fuel consumes a lot of energy—so much energy that there is debate about whether ethanol from corn actually provides enough of an environmental benefit to be worth the investment.
So scientists and startups are exploring other materials that have the potential to serve as fuel without the accompanying concerns about food supply and environmental impact. Cellulosic ethanol , for example, uses corn stover, wood waste, or other plant material that would not be used otherwise.
Other potential biofuel feedstocks include grasses , algae , animal waste , cooking grease , and wastewater sludge , but research continues to find the most efficient and cost-effective ways to transform them into usable fuel. All rights reserved. Share Tweet Email. Why it's so hard to treat pain in infants. This wild African cat has adapted to life in a big city. Animals Wild Cities This wild African cat has adapted to life in a big city Caracals have learned to hunt around the urban edges of Cape Town, though the predator faces many threats, such as getting hit by cars.
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It therefore helps to anchor the soil during a time when fields would otherwise lie fallow. It requires much less nitrogen fertilizer than, for example, corn. It shows potential as a biofuel feedstock, particularly in regions where the market for barley is not so big. Rye is a rather robust grain that also grows on poorer soils.
Fermentation efficiencies in the tested millet varieties ranged from 84 percent to 91 per cent compared to 97 per cent from the highly fermentable corn hybrid. In recent years, the food versus fuel debate, has focused attention on the use of waste from potato processing industries as a biofuels feedstock.
Cassava is an important food and feed crop in many tropical countries. It can also be cultivated on drier or poorer soils. China is a big promoter of cassava as biofuel feedstock. The USDA gain report published that in Thailand, the amount of ethanol produced from cassava was expected to double to 3 million tonnes in
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