#2 Possible Agro-Residues
The possible agro residues which do not pose collection and drying problems, normally associated with biomass are rice husk, coffee husk, groundnut shells, and coir waste. At present, loose rice husk, groundnut shells and other agro-residues are being used mostly by small scale boilers in process industries. Apart from being inefficient, these boilers do not have provision to capture fly ash and unburnt carbon, with the result that extensive air pollution is being created.
This pollution problem has become so acute that the state government of Punjab has banned the burning of loose husks in boilers. Other states are on the way to follow this policy. The users are advised to use such husks for making briquettes or fluidized bed boilers with proper pollution control measures. But the better option is briquettes and that would be helpful.
As the number of industries is day by day increasing and it’s obvious that the requirement of fuel is also increasing and the present power supply is unable to meet the energy demand. To combat this energy shortage, developed as well as developing countries are putting more efforts into R&D to tap alternative energy sources. In India alone, it is proposed that 18,000 MW should be produced from biomass.
Appropriate Biomass Residues for Briquetting:
There are many type of factors to consider before qualifying a biomass as a feedstock for briquetting Apart from its availability in large quantities, it should have the following characteristics:
o Low moisture content
Moisture content should be as low as possible, generally in the range of 10-15 percent. High moisture content will pose problems in grinding and excessive energy is required for drying.
o Ash content and composition
Biomass residues normally have much lower ash content except for rice husk with 20% ash but their ashes have a higher percentage of alkaline minerals, especially potash.