Cow dung is a fairly common waste in rural areas. This is because most of the villagers have professions as farmers, and need cows to plow the fields. Usually, cow dung will be collected and dumped on vacant land by villagers, without looking at the further impact of the cow dung. Therefore, it is necessary to process and utilize cow dung, to overcome the impacts that will occur.
Basically, cow dung can be used as a basic ingredient of organic fertilizer, because of the abundant nutrient content in it. Besides fertilizer, cow dung can also be used as biogas fuel. Biogas is gas that comes from processing organic materials, through a fermentation process in a closed container and room. This is done because the fermentation process requires an anaerobic reaction from the microbes present in cow dung.
Most of the fermentation product is methane gas which contains heat, so it can be used as fuel for cooking. Because biogas production also has residual use, the rest of the waste can also be used as compost or organic fertilizer.
In order to maximize the utilization of cow dung, two processes are made in the form of making biogas, with the manufacture of liquid fertilizer (POC). This is done so that the sewage that comes from the rest of the biogas production can be utilized better.
Method
The basic ingredient in making biogas is fresh cow dung, which is left in the open space for less than 12 hours. This is because the cow dung still has an optimal temperature (25°-30°C), so that when it is put in a closed container, the temperature of the dung can be maintained (Usman, et al., 2020). It takes two large closed containers as a container for cow dung, and a container to accommodate the fermented gas.
The two containers are connected by a pipe that has a valve to prevent excessive gas from entering. In both containers, a faucet was added to remove the excess gas present in both containers.
It takes cow dung about a third of the capacity of the closed container. In the process of making biogas, a 60 liter container is used, so 20 liters of cow dung is needed. Then, add enough water to dissolve the cow dung. Impurities need to be dissolved to facilitate the decomposition process of complex organic elements.
Dirt that has been mixed with water, needs to be left for about 14 days, in a tightly closed container and stored in a shady place. Every few days, the container is checked to make sure that the fermentation process is going well. The faucet on the container also needs to be opened slightly when checking, to reduce excess gas. The faucet is only opened a little and for a while. After 14 days, a trial was carried out by connecting the faucet in the gas container to the hose intended for the stove.
Discussion
There are three principles in biogas production, namely hydrolysis, acidification (acidification), and methanogenesis (Elfiano, et al., 2019). Hydrolysis is a process when the organic elements in cow dung change form into simpler elements. Then, acidification is a process when these simple elements turn into elements that have acidic properties. Finally, methanogenic is the process of forming methane gas by microbes present in cow dung.