In February of this year, the Chinese government released results of the first national pollution census （全国污染源普查). The most startling finding of this nearly three-year, 737 million RMB investigation was that agriculture is a bigger source of water pollution in China than industry. Because agriculture had never before been included in official pollution measures, the finding that farming is responsible for 44 percent of chemical oxygen demand (COD—the main measure of organic compounds in water), 67 percent of phosphorus discharges and 57 percent of nitrogen discharges was big news. The New York Times and The Guardian published articles on the Chinese pollution census.
In addition to fertilizer-, pesticide- and herbicide-containing runoff from crop fields, the census found that manure from livestock and poultry farms is a major source of agricultural pollution. An article this week in the China Daily further details animal waste problems, citing incidents of blue-green algae outbreaks in lakes and waterways because of excessive amounts of phosphorus and nitrogen from livestock farms. The photo to the right is an example of this phenomenon near a commercial pig farm I visited in Sichuan Province. Given the lack of effective water treatment methods and facilities, combined with the ever-increasing scale of livestock production, this is indeed a serious problem for China to address.
In response to the census, the Ministry of Agriculture (MOA) is promoting biogas digesters as a possible solution to the current “manure problem.” The ministry is currently executing and administering a $66.08 million (USD) loan from the Asian Development Bank to expand the use of biogas technologies. By 2020, plans are to construct an additional 80 million household methane digesters and 10,000 large-scale biogas plants. These projects build on technologies that have been used in China for decades. (Here is a report by Professor Li Kangmin and Dr. Mae-Wan Ho that gives a brief history of biogas use in China, dating from the late nineteenth century.)
The concern is scale. According to a water expert at the Asian Development Bank, presently less than 1 percent of the 4.2 million large-scale pig, cattle and poultry farms use biogas digesters to process manure. As these commercial farms follow the Confined Animal Feeding Operation (CAFO) model by packing more and more animals into smaller and smaller spaces and continue to take an increasing share of production and markets, surely they are the operations to watch—and to regulate. But to date, biogas digester projects have focused on small-scale production. The MOA estimates that 35 million of the 140 million rural households were using digesters at the end of 2008. While digesters can bring certain benefits to rural communities, particularly production of cooking gas and nutrient-rich fertilizer, these small-scale farms are not the ones contributing most to the manure-in-water problem.
The real challenge for addressing manure-based water pollution comes from the rivers of waste running out of commercial livestock farms and directly into bodies of water. If biogas digesters are to be the chosen path to correct this ill, perhaps there should be a mandate that all new CAFOs (and there are new ones coming into production all the time) must install digesters from the beginning. At the same time, the existing 99 percent of commercial farms that don’t already use them should be urged to do so.
Mindi Schneider is blogging from China. She is a native Midwesterner currently living in China and working on her PhD in Development Sociology at Cornell.