With technical guidance from the university, he constructed a six cubic-meter (212 cubic foot) brick-and-mortar underground plant near his cowshed and connected it to his existing 12 horsepower irrigation pump. By turning the gases emitted by cow dung slurry into a clean, renewable fuel that Patel uses to run his irrigation system, the plant saves him money, increases his productivity, and boosts his profits.
Experts say biogas plants like Patel's are easy to build, operate, and maintain. And in a country dealing with changing rainfall patterns, and where only 35 percent of agricultural land is irrigated, they could transform the lives of India's small farmers.
Biogas plants, or digesters, work by encouraging the breakdown of organic matter (cow dung, in Patel's case) by bacteria in the absence of oxygen. The resulting methane gas can then be stored and burned as fuel. Each day, Patel's plant converts the 200 kg (440 pounds) of dung his livestock produce into 8 to 10 hours of power. It takes 30 kgs of dung to generate one cubic meter of gas. "But, yes, collecting all that dung from the cowshed unfailingly every day is highly labor intensive," he admits.
Before turning to biogas, Patel would struggle to come up with enough power to run his home and his farm. "The eight hours of power that the government grid supplies daily to a single tube used by 10 neighboring farms would always be usurped by large-holding farmers," says Patel. "Every day I would have to buy 1.7 liters of diesel to run my pump." For irrigation alone, Patel was spending 22,000 rupees ($400) annually and had to limit his farmed area in the summer to keep down costs.
Today, Patel's diesel bill is a fraction of what it was. His biogas plant produces more power than he can use, so after his farm and home requirements are met he sells the remaining power to area farmers, charging 60 rupees ($1) an hour.
He is forced to keep his rates competitive with the government-subsidized power supply to farmers in the area, which caps his profits. But he still has an edge when it comes to timing: The government supply is available for limited and often inconvenient night-time hours; Patel can give his clients power whenever they need it.