Thanks to the solar heater, a shower is a daily possibility, and the biogas digester -- which converts human and pig waste to a clean gas that can be pressurized -- has enabled cooking and lighting.

CNN: 'Green' revolution under way in rural China

More time is then left to devote to his income-generating greenhouse, which uses waste slurry left over from the biogas digester as fertilizer for his grapes, strawberries, apples, plums, cherries, peaches, eggplant, cucumber, tomatoes and squash.

CNN: 'Green' revolution under way in rural China

In an off-grid village in India, for example, biogas from an anaerobic digester could be burned to drive the Stirling engine to generate power.

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It is also developing an anaerobic digester that acts like a giant cow stomach, creating biogas from solid food and plant waste.

FORBES: Technology