Getting to know biogas: its composition and manufacturing process from cow dung


Biogas is produced from the decomposition of organic matter which produces methane gas as the main product as an energy producer. Biogas energy is energy from gas which is the end product of digestion or anaerobic degradation of organic materials carried out by anaerobic bacteria in a free environment.

The biogas process can be observed in human waste, animal waste, household organic waste, to biodegradable waste that is in anaerobic or decomposed conditions.

The use of biogas has actually been done for a long time. Biogas-producing tools have been around since 1900 as a heat generator by the Egyptians. Although not a new finding, quality improvement is still needed in order to obtain better biogas.

At present, biogas energy is a renewable energy source that can be used to meet electrical energy and vehicle fuels.

Biogas Composition

In biogas, the main component is methane gas.

Meanwhile, the complete composition of biogas is:
(1) Methane (CH4) 50-70 percent;
(2) carbon dioxide (CO2) 30-40 percent;
(3) Hydrogen (H2) 5-10 percent;
(4) Nitrogen (N2) 1-2 percent;
(5) water vapor (H2O) 0.3 percent;
(6) hydrogen sulfite (H2S) is very small.

Of the various compositions of biogas, methane is an important element that can be used as a benchmark for energy or calorific value in biogas. Methane with a high value indicates that biogas has more energy, and vice versa. Methane gas is colorless, but has a strong odor. If burned, then methane will produce a blue flame without emitting smoke. The heat level is higher than the combustion of kerosene, charcoal, and other traditional materials.

How to make biogas

The principle of making biogas is a process of anaerobic decomposition of organic matter or closed from free air. From the decomposition, the main gas will be methane and carbon dioxide which are flammable. This gas is called biogas and can be produced from a variety of sources of organic matter.

The anaerobic decomposition process utilizes methane bacteria. Processing requires a temperature of approximately 30-55 degrees Celsius for fermentation to occur. In this temperature range, bacteria will break down organic matter optimally and produce methane and other gases.

Biogas installation requires a main building called a digester. Its function is as a reservoir for methane gas from the breakdown of bacteria on organic matter. The type of digester that is often used is the continuous feeding model, by filling in organic matter every day. Approximately 16 square meters of land is required for installation needs.

The digester is made of sand, cement, river stone, coral, red brick, construction iron, paint, and pralon pipes. In addition to the digester, it is necessary to build a sludge reservoir which can later be separated and used as solid and liquid organic fertilizer.

Making Biogas from Cow Manure

The following is an example of the process of making biogas using organic cow dung:

1. Mix cow dung with water to form mud. The ratio is 1:1 in the temporary reservoir. The shape of the mud makes it easier to put it into the digester.

2. Flow the sludge into the digester through the inlet. During the first filling, the gas valve at the top of the digester is opened to facilitate the entry of materials. In the first filling, large amounts of cow dung mud are needed until the digester is full.

3. Add 1 liter of starter (many sold in the market) and 5 sacks of fresh rumen content that can be obtained from slaughterhouses (RPH). This amount is for use in a digester with a capacity of 3.5-5.0 m2. Close the gas valve again so that the fermentation process occurs.

4. On the 1st to the 8th day, a lot of carbon dioxide gas will be produced. Remove this gas by opening the faucet. Methane gas is formed on days 10 to 14, and carbon dioxide decreases. When the composition of methane is 54% and carbon dioxide 27%, biogas can ignite or burn.

5. On the 14th day the gas can be channeled into the pipe and used to light a gas stove fire or other needs. Since day 14, the digester produces biogas energy which is always renewable. Biogas does not smell like cow dung.

6. Finally, the digester must be continuously filled with cow dung mud in order to produce optimal biogas.