The biogas capital of Bhutan

Gauri Shankar’s six cows not only provide him butter, cheese and milk, but also the energy to heat and cook food.

Since November last year, it has become an early morning routine for the 31-year old farmer of Hangay village in Sipsu to collect cow dung and fill it into a concrete pit a few metres from his kitchen.

The farmer gathers 45kg of dung in a tin, which is churned with water, and poured into the airtight digester pit. The gas from the pit comes up through a pipe with several valves that connects to a stove in the kitchen. The gas will last the entire day.

Having received a month-long hands-on training for trainers on biogas technology through the UNDP GEF small grants programme, Gauri Shankar now assists other members of the Hangay farmers group to build biogas plants.

Since November, they have completed 16 of the 25 plants funded by UNDP GEF small grants programme.

Farmers said earlier they had to travel to Samtse, about 50km from Sipsu, to refill their liquefied petroleum gas (LPG) cylinders, spending about Nu 800, including travel expenses. “Not anymore now,” Gauri Shankar said.

The 91 households of Hangay village are prone to wild elephants destroying their crop, which is why most farmers largely depend on livestock. Each household owns between two to 20 cattle each.

Another farmer Devi Maya, who recently installed biogas plant at her home, said rearing livestock was advantageous. “Apart from dairy products, there’s a lot more my cattle give me,” she said, excited.

Other farmers, who are not a part of the group, have also shown interest, said Gauri Shankar, who is also the group’s treasurer. “But they’ll have to bear their own expenses, if they want to build one and we shall assist them.”

Construction of a biogas plant is expected to cost between Nu 40,000 to 45,000 depending on the location; and includes the cost of the cement pit, stove, pipes and valves. A properly constructed and well-maintained biogas plant is said to last at least 20 years.

In fixed dome biogas plants, two underground pits are built – a digester pit with a dome shaped cover and the slurry reservoir, built above the digester. As the reservoir emits gas, it collects in the dome and displaces some of the slurry into the reservoir. As gas is used, the slurry flows back into the digester to replace it.

Biogas plants use bacteria to break down wet organic matter, like animal dung, human waste and food waste that produces biogas, a mixture of methane and carbon dioxide, and also a semi-solid residue.

Biogas can also be used for lighting.

Source: Kuenselonline