Biogas : Sustainable fuel from food waste

Treatment and proper disposal of municipal solid waste (MSW) is a tough task for civic bodies all over India. In a city like Pune, around 1400 Tons of MSW is generated per day. Presently, the waste generated in Pune is just dumped at a dumping ground near ‘Devachi Urali’ at Phursungi, Pune. As a responsible civilian, it is our duty to reduce waste generation and dispose our waste generated at our own level. It is possible to do so using simple cost effective methods.

MSW mainly consists of roughly 50% non biodegradable and 50% biodegradable waste. Non- biodegradable waste like plastic, metal and glass is reused/ recycled in various ways. Biodegradable waste treatment can be efficient if done in a decentralized manner. Biomethanation (biogas production), vermicomposting and aerobic degradation are some routinely used methods, used for treatment of biodegradable waste.

Biogas Generation
Biogas is generated by bacteria in the process of biodegradation of organic material under anaerobic conditions. This process creates methane that can be captured and used to either run thermal appliances (cooking) or to create electricity by feeding the methane to generators.
Biogas can be created from a wide variety of biomass (starch and sugar based). These can range from energy crops, crop refuse and waste. The use of waste such as manure and kitchen waste to create energy is an aspect that makes biogas especially relevant in the context of rural India.

A new perspective in biogas technology
(Pune based scientist’s modern experiment)

Preface:
To produce biogas from waste or stale food, waste flour, wet waste in house, edible and non-edible seeds is now not new to us. But to separate the gases like methane (CH4) and carbon dioxide (CO2) from biogas and to fill it in separate cylinders is certainly a modern technology. The above mentioned procedure is done successfully in Pune’s suburb, Hadapsar by Mr. Deepak Kanhere, Director, Shashwat Oorja Pvt. Ltd. Both gases have separate application in industrial field. This is the only experiment in India what they have claimed.
Pune based NGO ‘ARTI’ (Appropriate Rural Technology Institute) headed by senior scientist Dr. A. D. Karve, used food waste to produce biogas and also won the prestigious Ashden awards for sustainable development in 2006. But scientist Mr. Deepak Kanhere has gone further and separated Methane and Carbon dioxide successfully and enhanced the biogas usage. Prior to this he was associated with ARTI, Pune. And since last 7-8 years was in research for various type of material to be used as feeding material. In the last year, he has founded Shashwat Oorja Pvt. Ltd. and kept the biogas research further in the interest of society. They have installed a prototype demonstration plant at Hadapsar, Pune, where vegetable waste and waste food is the primary feed for which the near by 2-3 restaurants is the point of supply for same.

About the plant :

Daily around 100 kg waste is treated in plant to produce around 8000 liters of biogas. This has the budgetary expenditure of 6.36 Lac. This plant has consumed around 1200 sq. ft space for erection. Initially all the waste is physically inspected to sort out non degradable material such as plastic bags. By using pulveriser all material is crushed to form a paste. Water is added to form slurry and all the material is pumped up to digester tank. This digester tank contains slurry of dung to avail a colony of anaerobic bacteria for degradation process. This mixture goes further into two tanks to form acidogenesis and methanogenesis. All the tanks are airtight to keep anaerobic status for bacteria’s survival. At the last two tanks biogas is produced and is catched in gas holder tank, which is inverted into digester tank. At the time of biogas production the waste water coming out in the form of slurry is reused for next day’s feeding material. And hence no additional water is required daily which saves the cost and efforts. Produced quantity of biogas is further compressed by a compressor in MS capsule. Update this is normal process to form CBG (Compressed Biogas).

An innovative option:
Biogas contains methane (CH4), carbon dioxide (CO2), hydrogen sulfide (H2S) but methane is the only gas which is flammable. One can roughly estimate the percentage of methane and carbon dioxide is 60% and 40% respectively. To separate these gases, a “scrubbing system” is used. This is seamless MS pipe containing ceramic reching as the scrubber material which is porous in state and hence enhances the process of scrubbing.

Biogas with a pressure of 10 kg/cm2 is forced in from lower side while water at the rate of 40 ltr/min through the scrubber. Carbon dioxide is easily soluble in water, hence get dissolved and purified methane comes out, which is again passed trhough a second scrubber to remove moisture. The CO2 dissoloved water is again passed through third scrubber where CO2 is released and collected in a capsule. Plain water is recycled in the process again and again. The produced quantity of CO2 is raw in nature and needs further purification.

Cost of production:
By the scrubbing of biogas 1 kg CH4 and 1 kg CO2 is separated and roughly costs 17-19 Rs/kg. Purified CH4 can be sold at rate of Rs. 35/kg while CO2 at the rate of Rs. 25/kg. but if the CO2 is purified further then can be sold at Rs. 40/kg. All the required material to erect this type of p lant is available easily across India.

CO2 usage:
1. Foundry: to keep the molding porous in nature.
2. In extraction solvent system – distillation
3. In aerated soft drinks (food grade)
4. For photo synthesis of crops in farm.
5. As pesticide for aerobic pests can be possible.
Slurry is rich in nutrients and can be used as liquid fertilizer.

Fuel farming:
If we cultivate Sugar-beet as energy crop in the farm, which yields around 30 Tons /acre. In addition to this around 10-12 tons vegetative waste is available as fodder to animals. This crop is of 5 months and won’t require specific soil conditions or integrated crop management. It enhances the soil condition for nitrogen fixation. This adds good amount of income to farmer, besides saline land management.
Maize, sugar-beet and tapioca are few examples of energy crop yielding 500/ 300/900 lit/kg respectively.

Carbon credit:
Due to high penetration of CFC gases, the problem of global warming and pollution arises. To reduce the emission of these gases is awarded by carbon credit certificate (CCC). If we reduce the amount of CO2/ CH4 by installing a biogas plant we can claim carbon credit. For which plant size of biogas should be bigger.
By filling one ton of CO2 in cylinder, we can avoid its release in atmosphere, then 12 euro (INR 720) is offered by CCC. As methane is 21 times more polluting than CO2, we can claim 252 Euros (INR 15000) for one ton. By this we can save pollution, but also add income source to project.

Very easy installation:
We can install these type of projects in hotels, educational institutes and even in hostels, because they produce large amount of food waste and biomass.
Methane cylinders can be sold in comparison with LPG at an estimated price of Rs. 35/kg. this plant becomes economically viable when it has a capacity of 4 tons waste /day and costs approximately 85 Lacs with a payback period of 6.5 years. All these projects are eligible for bank finance with 10-12% rate of interest.

Some international organizations such as Shell Foundations offer funding for these type of project in the form of subsidy. If in any town of village a group of entrepreneurs come together, can erect this type of project to achieve a good opportunity for income source as well as local employment.

Methane usage:
This gas can be used as fuel in kitchen, automotive in compressed form. This gas generates electricity by means of a generator. Since the gas is purified, it adds more calorific value in comparison with biogas.