Digester technology cleans up after pigs
Australian science is helping to solve one of China’s biggest and smelliest problems – what to do with the waste produced by its 700 million pigs.
Working with Chinese scientists and technology firm HLM Asia Ltd, Australia’s CRC for Contamination Assessment and Remediation of the Environment (CRC CARE) has helped develop novel digester technology to help deal with the estimated 1.4 million tonnes of manure and 7mt of urine produced by the burgeoning Chinese pork industry annually.
CRC CARE managing director Professor Ravi Naidu said the new technology can produce clean energy (biogas), fertiliser and other valuable products from nutrient-rich waste, in a system with great potential for application in other industries worldwide.
China has 700 million pigs in 1.8 million farms, which supply two thirds of the country’s rapidly-growing meat consumption.
"However these piggeries also produce enormous volumes of waste, only a tenth of which is currently being treated," he explained.
Despite tighter regulations, large amounts of nitrogen, phosphorous and contaminants are being discharged into the environment where they damage ecosystems and pose a threat to human health.
The nutrients lost in the waste of one pig alone are worth about $50 a year, but there is no technology in place yet to recover and use this vital resource.
Professor Naidu says the joint project has developed a two-step underground anaerobic bioreactor for treating piggery waste, and established the settings for load and digestion time. It has identified a particular combination of anaerobic treatments that can recover the nutrients and produce clean biogas energy as well.
"The technology has been demonstrated in the field and is now being scaled up to treat large volumes of wastes from a number of piggery farms," Professor Naidu said.
The technology is expected to have widespread application not only in China but throughout Asia, wherever animals are farmed intensively, and to create fresh export opportunities for Australian technology solutions to similar contamination problems.
In this project the CRC is providing scientific expertise, including supervision of six PhD students at Huazhong University of Science and Technology in Wuhan Province with links to research skills at the University of South Australia.
The project is being managed by HLM Ltd on the ground, taking advantage of the relatively low cost of technology trials and scale-up work in China.
"It’s a perfect partnership between Australian science and Chinese technical expertise," Professor Naidu said.
He said the main scientific and technical challenges solved by this project are the high N and P loads in pig waste compared with domestic sewage, the current small size of biogas reactors, their slow rate of digestion, the limiting influence of temperature, and the presence of heavy metal contaminants which restrict the use of residues as fertiliser.
So far, the technology has been able to overcome each of these, and is now moving to full-scale trials.
"The market for a successfully packaged solution to this suite of problems is clearly very large – both in Asia and around the world. Besides handling livestock wastes, similar bioreactor technology can be used to manage and cleanse the runoff from urban landfills and organic waste streams from other industries," Professor Naidu said.
"We anticipate that the scientific and technical knowledge gained in the course of CRC CARE’s research will have real value for Australia’s intensive livestock and food industries – and will help protect our environment from these types of wastes.
"At the same time we are producing a new source of clean energy for industry or domestic use, and a vital supply of nutrients to help secure the future of food production."
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