CONVERTING COW MANURE TO FUEL

The stench of cow feces, urine and ammonia forces residents to keep windows and doors closed in parts of California's farming country. Some people constantly run air purifiers at home to counter the smell and, they say, fight off air-related ailments.

Industrial-scale dairy farms already are among the biggest polluters in the San Joaquin Valley, a premier U.S. agricultural region with poor air quality. Now residents like Whitfield worry methane digesters, which can turn manure into a biofuel that is cleaner than traditional fuels like gasoline, could exacerbate health issues. Biofuel experts say digesters can reduce air pollution.

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