In at the beginning or during the process.

future generations there will be demand for energy because of fast decreasing
of fossil fuel , fuel quality, price to paid for materials and transportation cost
and all have the effect to environment. The solution lies by the use of renewable
resources (Muthu, D 2017). The fact that biogas
is not new but to modern days it is the effective renewable energy. But how
does the biogas is produced in biogas digester?

Biogas is a biofuel produced from the anaerobic fermentation
of carbohydrates in plant material or waste (example, food peelings or manure)
by bacteria. Biogas is
characterized based on its chemical composition and the physical characteristics.
It is primary mixture is methane (CH4) and carbondioxide (CO2). However the
name “biogas” form by a large variety of gases resulting from specific
processes from various organic waste.

composition of a gas issued from a digester depends on the substrate, of its
organic matter load, and the feeding rate of the digester.It
is mainly composed of methane,
with some carbon dioxide and other trace gases. The proportion of methane
within the biogas can vary between 50% and 80%, depending on whether some oxygen
is able to enter at the beginning or during the process. If some oxygen is
present, the bacteria will respire aerobically and
will produce a carbondioxide with a higher proportion and a lower proportion of
methane (BBC UK 2000).The key
process is an optimum temperature for biogas production is between 32oC
and 35oC. Temperatures above or below the optimum can result in different
quality of biogas, which can be a problem in tropical and seasoned countries
(see table below) (BBC UK 2000).This is how the digester works. First collect
the waste or cow dung and mix it with mixture of anaerobi bacteria with water
in the influent channel. After that it is  quickly release the mixture into the influent
channel that lead to the main chamber, there the anaerobic digestion will
occur. In few days after the digestion, the methane gas that turn into biogas
will rise on top of the dome and escape through the biogas outlet, where lead
to the kitchen to use as cooking gas. After the mixture out of gas and being
used all of it, it will turn into a sludge sediment. The sludge rise up to the
effluent channel with help of a pump to empty the dome. The escape sludge can
be use again as a compost to fertilize crop

(SciTech, Youtube 2013)