How to make biogas from Kitchen waste, has been the question asked for ages. Biogas is the next best clean energy besides LPG and CNG. Biogas could be prepared from organic waste, sewage, dung, food waste or plant material as input raw material. I have been trying to understand why the replication of biogas plants has been so low. These plants are another source for turning waste to wealth. Swachh Bharat Abhiyan has been laying increased emphasis on Decentralized waste management in India. So before going any let us understand the basics behind biogas:
What is Biogas?
Biogas is formed by action of bacteria through anaerobic digestion organic waste. Let me break this down a bit 🙂 There are 2 types of decomposition.
- Aerobic – Aerobic is that process which happens in the presence of air
- Anaerobic – Anaerobic that process that happens in the absence of air.
Biomethanation is that complex micobial process in which organic substances are broken down to methane (approx. 60%) and carbon di oxide (approx 40%). Biogas could be used readily for cooking purposes or can be fed into an engine to generate electricity.
Composition of Biogas: Characteristics
Biogas is a colourless and an odourless gas and burns like the LPG. Composition of Biogas largely is dependent on the input feed material used. The gas ignites at a temperature of 650 to 750 degree Celsius and could be used as substitutes for LPF, petrol, diesel etc. The general composition of biogas is as below:
|Component||Concentration (By Volume)|
|Hydrogen Sulphide||20-20,000 ppm|
Why should you consider putting up a bio gas plant at your house?
Biogas plants are known to use kitchen waste as input for gas production. A house with 3-4 persons produces close to 750 gms to 1 kg of kitchen waste. This waste is generally mixed with garbage and disposed into landfills create a waste nightmare. Having as biogas plant at home provides an opportunity to manage waste and energy costs at the same time. A daily waste input of 0.75 – 1 kg could feed a 1 cu meter plant and can generate about 2 hrs worth of gas supply for cooking purposes. These plants generally are accompanied by single burner cook stoves. The space occupied by this plant is 1 Sq meter. As the space required is minimial, it could also be set up in schools to promote Swacch Vidyalaya.
Selection of size of the plant
|Size (Cu m)|
Suitable size of family members
Production of Biogas: How to make Biogas from Kitchen waste
A biogas kit comes along with a digester in which kitchen waste is digested and methane is released. The gas released during digestion is stored in the upper drum that moves up and down based on the generation of gas. The gas drum is fit within a frame to ensure it does not tilt because of pressure. In case excess gas is produced it is released automatically because of buoancy and is passed through the pipes for storage or burning. The kit comes along with a single burner gas stove and could be used readily for cooking.
The input for digester is partly kitchen waste and partly starchy water that is got after washing dhal or rice. Cow Dung is generally used once to create a starter culture within the digester. Post which vegetable waste can be fed into the digester. After complete digestion the waste is converted into rich manure that could be used for gardening purposes.
Calculation of Savings due to biogas
- Quantity of biogas used for cooking purposes: 0.33m3/hr
- Burning of biogas from 1 cum plant = 0.6 m3/day (considering 60% efficiency)
- Burning of biogas in 1 year = 219m3/year
- 1m3 = 0.45 kg of LPG
- Amount of LPG equivalent produced in a year =98.55kg
- This is about 6.8 LPG cylinders (14.5kg) in a year.
- Families of 4 consume 12 cylinders in a year. The new Government rules provide 6 cylinders to citizens at a subsidized price of Rs. 400 and rest 6 in a year at non-subsidized cost of Rs. 750-800.
- Total savings due to Biogas = 6.8*750 = Rs. 5100
Biogas plant cost: What is the investment required?
Biogas plants generally cost INR 7000-8000/cu m capacity. They have a lifetime of 25 years and have minimal to no maintenance cost.
Biogas vs LPG
- LPG has higher calorific value than Biogas; so less gas is required to produce the same amount of heat. Average calorific value of biogas is 20 MJ/m3 while LPG is 46.1MJ/Kg
- 1 m3 biogas = 0.45 kg of LPG.
- LPG requires more oxygen for propoer combustion. LPG requires oxygen:gas ratio = 25:1 while biogas requires 10:1. Hence LPG is provided in pressurized form and in smaller quantities for more oxygen during combustion.
Biogas plant manufacturers
This is an important section I wanted to cover as a part of this post. There has always been some difficulty identifying technology providers for domestic biogas plants. I have tried to put together a list of technology providers who you can get your biogas plant for your house:
1. Biotech India (www.biotech-india.org)
2. Sintex (www.sintex-plastics.com)
3. Kirloskar Integrated Technologies (www.kitlgreen.com)
4. Synod Bioscience (www.synod.in)
Hope this post on How to make Biogas from kitchen waste was useful to you. Have you already installed your biogas kit at home? Please do share your experience with us.