 FIRE AND ICE: To make biogas work in cold climates, this plant in Kyangjin Gompa in Langtang uses a compost heap to insulate the underground digester so the yak dung can be converted into cooking gas. |
In the past 50 years, over 205,000 households have built biogas plants to turn farm manure into methane gas for cooking and lighting. The simplicity of the Nepali-designed technology that allows bacteria already inside the cow's stomach to turn cowdung into a clean and safe gas is only half the story.
The other half is a successful government-subsidised soft credit scheme. There is almost 100 per cent payback, the effluent is excellent pathogen-free fertiliser, and the elimination of indoor pollution from kitchen fires has reduced child mortality.
The Nepali fixed-dome biogas design is cheap and maintenance free, and proved to be superior to Indian and Chinese models. After initial support from the United Mission to Nepal, the Dutch group SNV stepped in with the Biogas Support Program (BSP), and millions of farmers in nearly all districts of Nepal have benefited in the past decades.
Today, 98 per cent of the plants are still functioning, some of them nearly 30 years old. Nearly 20,000 new plants are being added every year and BSP's goal is to have a total of 500,000 plants in Nepal. The organisation won the prestigious Ashden Award for Sustainable Energy in 2005.
One of the limiting factors is that biogas doesn't work as well in the cold climate at higher elevations. But with its new pilot plants in Langtang, BSP has found a simple way to generate methane from yak dung even at higher altitudes.
Pasang Demdi Sherpa, a trekking guide, is happy with the biogas plant in his hometown. "It saves us a lot of firewood, and I wish more people would use it," he says.
What Pasang Demdi and other high-altitude biogas users have done is to pile a compost heap on top of the underground digester so that it heats and insulates the� digester from the chill of the Langtang winter.
Kyanjin Gompa, the highest settlement in Langtang Valley at 3,850m, is where no biogas plant has gone before. At first, the plant at Hotel Yala Peak just looks like a pile of rubbish, but beneath the heap of steaming compost is the underground dome digester that supplies methane to the kitchen even in winter.
"We've considered many other methods of heating the digester, from using solar heaters to building biogas plants within greenhouses, but those are very expensive solutions," explains Hari Bahadur KC, an engineer with BSP.
Heap composting to insulate digesters is a small-is-beautiful solution that needs no added cost, and the compost itself can be recycled for fertiliser. Biogas can now go to mountain regions, where replacing firewood for cooking is even more important to protect the environment.
BSP's executive director Saroj Rai is not someone who rests on his laurels. He is happy that Nepal's biogas program is an internationally acclaimed success story because of the 'ecology of support' it has from the government, banks, donors, technicians and farmers. But he wants to concentrate on making the technology even more widely available, and maintain the quality of the construction and after-sales service.
Says Rai: "Biogas is perfect energy solution for rural Nepal, and it is regarded as a model for other countries as well."
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HOW DOES BIOGAS WORK?
The technology couldn't be simpler. All you need is four cows for a four-member household, mix the cowdung with an equal amount of water, allow it to ferment in an underground digester and the carbohydrates are decomposed into flammable methane gas. The spent slurry is very good fertiliser, and the process is completely organic. The beauty of it is that the technology has no movable parts and needs very little maintenance. Larger families with fewer cows have also successfully linked their latrines to the digester.
Usually, BSP provides a Rs 12,000 subsidised credit to defray the cost of building the plants and most farmers offset that cost by the Rs 10,000 a year they save in not buying firewood and kerosene. an 8 cubic m plant usually costs between 50-100,00 rupess depending on road-access. Plants in roadless areas of Nepal cost more.
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