Cooking with two cows? Easy as 1, 2, 3

Pino says each house needs dung from at least two cows to meet its biogas energy needs. The dung from two animals can produce enough biogas to cook for up to two hours. And yes, goat droppings can also be processed into biogas.

“But goat dung contains only a little methane. Processing goat dung into biogas requires more time because goat dung is more difficult to break down.”

Transforming cow dung into biogas is very easy. First the cow dung has to be broken down to become a liquid. At this stage the cow manure must be stirred until it’s evenly distributed.

Waste from grass that has not been refined by the digestive process in the cow’s stomach is separated. This is done to prevent any blockages when it goes into the reactor. After it’s dissolved and evenly distributed the cow dung is put into the pool, or reactor. It takes four to five days in the reservoirs for the cow dung to produce methane.

Next, the methane gas produced is then channeled through pipes to a plastic bladder. The size of the bladder depends on the capacity of the reservoir. Gas from a reservoir of 1.5 x 2 meters can be accommodated in a 500-liter plastic bladder. Once it is filled with methane gas, the plastic bladder that was previously empty becomes inflated.

The plastic bladder containing the methane is connected to a plastic hose to the stove. If there is too much methane, the gas can be channeled to to several stoves. This means the owner of a biogas processing plant can also share production with neighbors.

One of the most important points in making biogas is choosing the right digester. There are three types of biogas digesters available these days, including the fixed dome plants developed in China.

The floating drum plant, mainly used in India, is a variant of the biogas plant plastic cover, while Taiwan, Ethiopia, Colombia, Vietnam and Cambodia mainly use plug flow plants, or balloon plants.

The main parts of a biogas digester are: (1) the manure reservoirs, (2) the digester, (3) the slurry pond, (4) the gas reservoirs, (5) the exit gas pipeline, (6) the exit slurry pipeline and (7) the cattle dung intake.

In Indonesia, most farmers in rural areas make balloon-shaped digesters because it is relatively easier and cheaper.

A balloon plant is made of plastic with one end of the pipe in the manure and the other end of the going out in the slurry. The gas exit pipe is installed at the top.

Balloon digesters are cheap, easily transported, simple to construct and easy to maintain and operate.

Although one of the downsides is the balloon digester remains relatively fragile and can damage easily.

If the system isn’t well maintained, mice are prone to eat the plastic balloon containing the methane, which means gas will leak.

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