Answer: Biomass Energy and Harnessing Methods
1. Definition
Biomass Energy is renewable energy derived from organic materials of biological origin, including plant matter, agricultural residues, forest products, animal waste, and municipal solid waste. It is one of the oldest energy sources used by humans and represents stored solar energy captured through photosynthesis.
Biomass is considered carbon-neutral in principle because the CO2 released during combustion or decomposition was recently absorbed from the atmosphere during plant growth, unlike fossil fuels which release carbon stored millions of years ago.
2. Types of Biomass Feedstock
| Category |
Examples |
Availability in India |
| Agricultural Residue |
Rice husk, wheat straw, sugarcane bagasse, corn stover, cotton stalks |
~500 million tonnes/year; major source |
| Forest Residue |
Wood chips, sawdust, bark, branches, leaves |
Significant but regulated |
| Energy Crops |
Switchgrass, miscanthus, jatropha, bamboo, eucalyptus |
Limited cultivation currently |
| Animal Waste |
Cattle dung, poultry litter, pig manure |
300 million cattle; huge potential |
| Municipal Waste |
Organic fraction of MSW, food waste |
~150,000 tonnes/day generated |
| Industrial Waste |
Food processing waste, paper mill sludge, distillery waste |
Available from agro-industries |
3. Methods of Harnessing Biomass Energy
A. Thermochemical Conversion
1. Direct Combustion
- Process: Burning biomass in boilers to produce heat and steam for power generation
- Temperature: 800-1000°C
- Efficiency: 20-25% (electrical); up to 80% with CHP
- Applications: Biomass power plants, industrial boilers, co-firing with coal
- Example: Bagasse cogeneration in sugar mills (5000+ MW in India)
2. Gasification
- Process: Partial oxidation of biomass at high temperature with limited oxygen to produce syngas (CO + H2 + CH4)
- Temperature: 700-1000°C
- Output: Producer gas (syngas) with calorific value 4-6 MJ/m³
- Applications: Power generation, thermal applications, synthesis of chemicals
- Advantages: Cleaner combustion, higher efficiency than direct burning
3. Pyrolysis
- Process: Heating biomass in absence of oxygen to decompose into three products
- Temperature: 300-700°C
- Products:
- Bio-oil: Liquid fuel (can replace furnace oil)
- Biochar: Solid carbon (soil amendment, carbon sequestration)
- Syngas: Combustible gas
- Types: Slow pyrolysis (more char), Fast pyrolysis (more bio-oil)
4. Torrefaction
- Process: Mild pyrolysis at 200-300°C producing energy-dense solid fuel
- Output: Torrefied biomass with coal-like properties
- Advantages: Improved energy density, storability, grindability
B. Biochemical Conversion
1. Anaerobic Digestion (Biogas Production)
- Process: Microorganisms decompose organic matter in oxygen-free environment
- Duration: 15-40 days retention time
- Output:
- Biogas: 55-65% methane (CH4), 35-45% CO2
- Digestate: Nutrient-rich slurry for fertilizer
- Applications: Cooking fuel, electricity generation, vehicle fuel (Bio-CNG)
- India: 5+ million family biogas plants; GOBAR-DHAN promoting large plants
2. Fermentation (Bioethanol Production)
- Process: Yeast (Saccharomyces cerevisiae) converts sugars to ethanol
- Feedstock: Sugarcane juice, molasses, corn, grains
- Steps: Pretreatment → Hydrolysis (for starch) → Fermentation → Distillation
- Output: Ethanol for fuel blending (E10, E20)
- India: 1300+ crore liters capacity; E20 target by 2025-26
3. Transesterification (Biodiesel Production)
- Process: Vegetable oils/fats + Alcohol + Catalyst → Biodiesel + Glycerol
- Feedstock: Used cooking oil, jatropha, pongamia, animal fats
- Output: Fatty Acid Methyl Esters (FAME) - biodiesel
- Application: Diesel blending (B5, B20)
C. Physical Conversion
- Briquetting: Compressing loose biomass into dense fuel blocks using pressure
- Pelletization: Making uniform cylindrical pellets for efficient combustion
- Advantages: Improved handling, storage, transportation; consistent fuel quality
4. Applications of Biomass Energy
| Application |
Technology Used |
Scale |
| Electricity Generation |
Combustion, gasification power plants |
MW-scale grid-connected |
| Cooking Fuel |
Biogas digesters, improved cookstoves |
Household/community |
| Transportation Fuel |
Bioethanol, biodiesel, Bio-CNG |
National fuel blending |
| Industrial Heat |
Boilers, furnaces, kilns |
Process industries |
| Combined Heat & Power |
Cogeneration systems |
Sugar mills, paper mills |
5. Biomass Energy in India
Current Status:
- Estimated Potential: 25,000 MW from agricultural/forest residue
- Installed Capacity: ~10,500 MW biomass power (incl. bagasse cogeneration)
- Family Biogas Plants: 5+ million installed
- SATAT Scheme: Target 5000 Bio-CNG plants by 2025
6. Advantages and Challenges
| Advantages |
Challenges |
| Carbon neutral (in lifecycle) |
Lower energy density than fossil fuels |
| Waste management solution |
Seasonal availability of feedstock |
| Rural employment creation |
Collection and transportation logistics |
| Reduces stubble burning |
Land use competition (for energy crops) |
| Dispatchable (unlike solar/wind) |
Storage and handling issues |
| Multiple co-products (digestate, biochar) |
Technology costs for advanced conversion |
Conclusion
Biomass energy offers versatile, renewable solutions for electricity, heat, and transportation fuel needs. Multiple conversion pathways - thermochemical (combustion, gasification, pyrolysis) and biochemical (anaerobic digestion, fermentation) - enable utilization of diverse feedstocks. For India, with abundant agricultural residue and livestock, biomass energy presents significant opportunities for rural development, waste management, and energy security. Scaling up requires addressing supply chain challenges, improving conversion efficiencies, and integrating biomass into national energy planning alongside other renewables.
Sources: Module 2 Notes | MNRE India | IEA Bioenergy | National Biomass Resource Atlas