Biogas is a familiar name in Indian households thanks to various efforts from our government's push for clean fuels across India in the past. Biogas is a gaseous mixture produced by the anaerobic digestion of organic raw materials. Biogas is mainly comprised of Methane, Carbon dioxide, hydrogen sulfide and saturated moisture but not limited to. In the past production of biogas was limited to farm yard manure and utilization for cooking applications in rural parts of India and lately large capacity biogas plants was very popular in industries with high organic loading in their effluents. The large capacity biogas was then mainly used for the generation of heat and power for the captive applications. Moving forward the demand for electricity and electrification of the grid in the interior part of India resulted in the concept of Bio-Power or Alternative energy resources along with solar and wind for the supply of electricity to our household.
Biogas generation is a proven process in the industry and is very close to each one of us as we carry one digester in our belly every day since we were born. If one drives the analogy between the digestion of food by living beings like humans, Animals etc one can say whatever they can use as food either as is or with some preparation like cooking, marinating, fermenting etc but not limited to can be potentially converted to Biogas in a controlled atmosphere.
The material around us generally has some distinct element which has its own significance if biogas generation is desired. These elements can be enlisted as below,
a. Organic fraction (Carbon)
1. Volatile Organic Matter – Generally this fraction can be converted to various reaction products with ease as against balance components.
2. Non-Volatile Organic Matter – Recalcitrant like organic polymer, lignin etc but not limited to
b. Inorganic Fraction- All inorganic element collective called Ash.
c. Moisture – It’s an equilibrium content at a given condition or as per downstream process.
Each and every element/material around us have either of it and the ease of converting it to an end product will drive the conversion process and end product. It could be the table which I am using right now as it is made up of particle board. However, The selection of raw material for the production of compressed biogas has various dimensions as below but not limited to,
1. Window of availability – Higher is preferred2. Access to raw material3. Transport requirement4. Storage and handling requirements5. Cost elements like securing, transport, Processing etc6. Yield of product and byproduct7. Ease of conversion8. Sustainability of supply chain9. Environmental impact and opportunity10. Benefit to society and their involvement
As a part of the SATAT program, we have identified various raw materials which we as a nation see issues in a way converted to opportunities for energy sustainability of India. Following are some of the raw materials which is in major focus for compressed biogas generation but not limited to,
A. Agricultural Waste: This is one of the most readily available with a limited window of availability of 30-60 Days in most cases. These are high on lignin and inorganics need state-of-the-art technology for effective conversion to CBG. The typical yield from this material can be up to 500 Am3/DMT depending upon composition and conversion process. Major agricultural waste is rice straw which is one of the major reason behind Air pollution in the northern part of India which is effectively being converted to Compressed Biogas.
B. Cow Dung: Cow dung is another potential feedstock available in abundance which is being potentially converted to Biogas for years altogether and now it can be converted to Compressed biogas at points of bulk generation like large Cow Shelters (Goshals), Diary Farms and cluster etc but not limited to. One can expect biogas yield up to 50 m3/MT depending upon composition and quality and process for conversion.
C. Press mud: Press mud is another organized source of feedstock. It is mainly a by-product from Indian sugar mills and is rich in organic which can be effectively converted to Compressed Biogas. Indian sugar production is more than 340 MMT which potentially generates about 1.3 MMT press mud which is presently utilized for bio-composting of Vinasse, Fertilizer ( As is basis), BioFuel (Briquette ) etc but not limited to. Looking at Non-bio-composting based zero liquid discharge trends in the distillery industry possibility of large-scale press mud availability for potential generation of CBG can not be denied. The press mud can produce upto 130 m3/ MT biogas or even higher as claimed by technology providers could be a welcome addition for sugar mills and all entrepreneurs for building CBG business. The press mud window of availability is upto 220 days a year at some places and about 130-150 days on average for mill operation. Press mud is perishable feedstock and without adequate provision for preservation significant loss of yield can be envisaged.
D. MSW: Over 60 MMT of generation and lack of processing & treatment facility to the scale of generation makes MSW is one of the major issue to tackle in India. Most of the MSW generated in India can be potentially converted to biogas. The segregation of the the MSW fraction is the ley hurdle in the process which need to be addressed to open up the CBG potential. The segregated MSW can produce upto 130 m3/MT biogas depending on level of segregation and composition of the MSW.
E. Food waste: India is known for diversity in food across the geography of the country. Sad part of the story is that we also waste significant amount of food via organized value chain of hotels and restaurants. Some of the cities in India are putting their best efforts in collection of food waste and treating them in dedicated facility for better utilization of its potential.
F. Municipal Sewage treatment plants: Indian STP are dominated by aerobic treatment technologies which generate lot of sludge for disposal which can be treated for production of biogas. Also all upcoming STP shall be designed to produce higher sludge for recovery of energy in the form of CBG. The implementation of Anaerobic treatment technologies for direct generation of biogas from STP and then converting it to CBG also can be thought of moving forward.
G. Industrial Waste water: All industrial wastewater with higher organic loading and significant biogas generation potential can be thought of to produce CBG as value added co-product rather as source of Heat and Power wherever possible.
The future of the compressed biogas project lies in access to lower cost Feedstocks that are readily available in the vicinity of the plant for a larger window of availability during the year.
