Treated excrement from turkeys, chickens, and other poultry, when converted to combustible solid biomass fuel, could replace approximately 10% of coal used in electricity generation, according to a timely new study by Ben-Gurion University of the Negev (BGU) scientists.
Environmentally safe disposal of poultry excrement has become a significant problem. During their short life, a broiler chicken will typically generate about two pounds of litter, which includes excrement, feathers, and bedding materials. One poultry house, which usually contains around 20,000 birds, can generate about 40,000 pounds of litter, which can be used as fertilizer, cattle feed, and also fuel.
In the study, which was published earlier this month in Applied Energy, researchers at the Zuckerberg Institute for Water Research at BGU evaluated two biofuel types to determine which is the more efficient poultry waste solid fuel.
They compared the production, combustion, and gas emissions of biochar, which is produced by slow heating of the biomass at a temperature of 450°C (842°F) in an oxygen-free furnace with hydrochar. Hydrochar is produced by heating wet biomass to a much lower temperature of up to 250 °C under pressure using a process called hydrothermal carbonization (HTC). HTC is mimics natural coal formation within several hours.
"We found that poultry waste processed as hydrochar produced 24 percent higher net energy generation," says student researcher Vivian Mau and Professor Amit Gross, chair of the department of environmental hydrology and microbiology at BGU's Zuckerberg Institute. "Poultry waste hydrochar generates heat at high temperatures and combusts in a similar manner to coal, an important factor in replacing it as renewable energy source."
The researchers also showed that higher HTC production temperatures resulted in a significant reduction in emissions of methane and ammonia and an increase of carbon dioxide and carbon monoxide.
"This investigation helped in bridging the gap between hydrochar being considered as a potential energy source toward the development of an alternative renewable fuel," Gross explains. "Our findings could help significantly reduce greenhouse gas emissions associated with electricity generation and agricultural wastes. Field-scale experiments with HTC reactor should be conducted to confirm the assessments from this laboratory-scale study."
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