Because I think this is an important issue, and because I will likely write more about it in the future, I’m reposting this short piece I wrote for the IATP Think Forward blog. Here is the original link.
In February of this year, the Chinese government released results of the first ever national pollution census （全国污染源普查). The most startling finding of this nearly 3-year, 737 million RMB investigation was that agriculture is today 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% of chemical oxygen demand (COD – the main measure of organic compounds in water), 67% of phosphorus discharges, and 57% of nitrogen discharges was big news. The New York Times and The Guardian published articles on the 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 this 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 at right is and 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 the country 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 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 worry in all of this is that of scale. According to a water expert at the Asian Development Bank, presently less than 1% of the 4.2 million large-scale pig, cattle, and poultry farms use biogas digesters to process manure. As these commercial farms using CAFO technologies that pack more and more animals into smaller and smaller spaces continue to take an increasing share of production and markets, surely they are the operations to watch…and to regulate. Biogas digester projects to date have focused on small-scale production, such that 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 the central government should mandate that all new CAFOs (and there are new ones coming into production all the time) must install digesters from the get go, while at the same time, requiring the existing 99% of commercial farms that don’t already use them to do so.