China should tap power of sludge
Print Edition
CHINA can cut greenhouse gas emissions and generate electricity by treating the 30 million tons of sludge its wastewater plants produce each year, the think tank World Resources Institute said.
If just 10 percent of the sludge was treated in bioenergy plants instead of being trucked to landfills, China’s carbon emissions would be reduced by 380 million tons a year, roughly the equivalent of Ukraine’s emissions, WRI experts said.
Bioenergy — or sludge-to-power — plants convert organic matter left over from treated sewage into electricity by heating the solid waste and using microbes to digest it.
The process produces methane which then can be burnt to generate power, while sterilized leftover solid waste can be used as fertilizer or to grow potted trees to restore landscapes and improve air quality.
“You can treat it as normal waste (or) can use technology to produce methane. Once you capture methane, you reduce emissions released into the air,” Zhong Lijin, senior associate and water lead at WRI China office, told the Thomson Reuters Foundation.
“At the same time you still have the extra biogas, which you can use for vehicles, heating systems or power generation,” she said by phone from Beijing yesterday.
China in June 2015 formally committed to halting the rise in its greenhouse gas emissions within the next 15 years, saying they would peak about 2030.
It has also set a target to spend about US$16 billion between 2013 and this year to improve sewage disposal and garbage treatment as the government struggles to find ways of treating the enormous amounts of refuse the world’s most populous country generates.
China has already started to invest in bioenergy plants, with four cities — Beijing, Changsha, Chengdu and Hefei — already installing or planning such systems, the experts said.
Once in operation, together they would be able to reduce emissions by 700,000 tons a year — the equivalent of a third of the emissions produced by cars in the United States each day, they said.
The plants would also produce enough compressed natural gas to power the plants and fill the tanks of 2 million taxis.
But this relatively small contribution leaves room for more efforts to curb emissions in China, one of the world’s largest energy consumers that accounts for a quarter of global greenhouse gas emissions.
“You can treat sludge as waste, but if you change your mind the sludge is not waste but a source of energy,” Zhong said.
“If you can recover your energy, if you can recover resources from waste, then you are doing something to close the (ecological) loop of the city.”
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