Biogas Plants

Biogas
Process Overview
Biomethane is produced in anaerobic
digesters, in the process called anaerobic digestion. Biomethane is a
renewable energy resource, as opposed to natural gas (methane), which is a
non-renewable energy resource. Biomethane has similar qualities of methane
and both are used in interchangeably, and each may be a substitute for the
other. Anaerobic digestion is a biological process that produces a gas
principally composed of methane (CH4) and carbon dioxide (CO2) otherwise
known as biogas. These gases are produced from organic wastes such as
livestock manure, food-processing waste, etc. As previously stated, Bio
methanization is the process of conversion of organic matter in the waste
(liquid or solid) to Bio Methane (sometimes referred to as "Biogas) and
manure by microbial action in the absence of air, known as "anaerobic
digestion."
Anaerobic processes could occur either naturally
or in a controlled environment such as a biogas plant. Organic waste such as
livestock manure and various types of bacteria are put in an airtight
container called digester so the process could occur. Depending on the waste
feedstock and the system design, biogas is typically 55 to 75 percent pure
methane. State-of-the-art systems report producing biogas that is more than
95 percent pure methane.
Production and disposal of large
quantities of organic and biodegradable waste without adequate or proper
treatment results in widespread environmental pollution. Some waste streams
can be treated by conventional methods like aeration. Compared to the
aerobic method, the use of anaerobic digesters in processing these waste
streams provides greater economic and environmental benefits and advantages.
Interest
in Bio methaination as an economic, environmental and energy-saving waste
treatment continues to gain greater interest worldwide and has led to the
development of a range of anaerobic reactor designs. These high-rate,
high-efficiency anaerobic digesters are also referred to as "retained
biomass reactors" since they are based on the concept of retaining
viable biomass by sludge immobilization.
Despite popular belief,
the amount of waste going in the digester is almost equal to the amount
coming out. However the quality of the waste is altered into the better
ready to use organic fertilizer. Waste coming out of the digester can be
separated (solid/liquid) to compost the solid part and use the liquid part
as fertilizing irrigation or to be treated further for rejection in nature.
The biogas concept we can offer is primarily suitable for farmer's home,
small farms, and rural electrification programs. The family size biogas
system is composed of one 2m3 biogas digester, a pipe system, a gas purify
system, appliances and/or an electricity generator.
The medium
size biogas system is designed for small size livestock farms to treat the
animal waste, for schools or factories etc. and to treat waste water from
toilets. The medium size biogas system is composed of a group of 10m3 biogas
digester that are formed into one unit, a pipe system, a gas purify system,
appliances and/or an electricity generator.
Raw material needed to
produce 1 normal cubic meter biogas
| Raw material |
Water content (%) |
Dry matter |
Fresh matter |
| Pig Manure |
82 |
4.00 |
13.85 |
| Cow Manure |
83 |
5.26 |
26.21 |
| Chicken Manure |
70 |
4.00 |
13.85 |
| Human Manure |
80 |
3.33 |
16.65 |
| Rice Straw |
15 |
3.84 |
4.44 |
| Wheat Straw |
15 |
3.70 |
4.33 |
| Corn stalks |
18 |
3.45 |
4.07 |
* From 25 kg of cow dung (organic
waste), you get 1 nm3 of biogas (Calorific Value 4500 5500 Kcal/nm3).
From one NM3 of biogas, you can generate 1.5 kWe per day.