A large quantity of biomass is utilized in the rural area as fuel. Briquetting of biomass is a process which acquired considerable significance in the recent past, due to its efficiency increase, reduction in bulk, and having high calorific value the of the briquettes. The process also helps to prepare smokeless briquettes, which are more hygienic to rural population, especially the women folk who are always hard of finding enough fuel supplies.

I. Introduction

Forest or agricultural biomass is generally difficult to handle because of its bulky and scattered nature, legal and administrative problems, low thermal efficiency and copious liberation of smoke. In order to achieve maximum and efficient exploitation of resources locally available, it is essential to compress them into manageable and compact pieces which have a high thermal value. The process is called briquetting or pelleting. Pellets are compressed biomass briquettes and are usually cylindrical-shaped with a diameter between 25-100 mm. and length varies between 100-400 mm. Briquetting of biomass to increase its bulk density has acquired considerable significance in the recent past. Briquetting consists of applying pressure to a mass of particles with or without a binder and converting it into a compact aggregate. Since biomass is compressed into a dense material, it is also called as densification.

II. Techniques for Making Briquettes

At a time when the supply of fossil fuel and fire wood is not keeping pace with the increasing energy demand in the country, the use of organic residues through briquetting is one of the promising alternatives to meet local needs in various sectors, households, small scale industries, such as bakeries, brick kilns, drying tea, tobacco, spices, power and producer gas generation. It has been observed that density, durability and combustion efficiency of briquettes increases with de crease in the size and increase in pressure during preparation. Three versions of compaction/briquetting machines based on the use of different forms of energy, manually operated, bullock operated, and power-operated, have been designed, fab ricated and tested by different agencies in the country. Mainly two techniques are available for making briquetted fuel from agro wastes.

a). Pyrolysed briquetted fuel

This process involves conversion of wastes/residues into charcoal in the absence of oxygen (pyrolysis) at 275-300°C and the briquetting is done. The principal users of this kind of fuel at present are households, hoteliers, factories, canteens, tea stalls etc: The crop residues viz. rice and wheat straw and husk makes a good material for briquetting. In Table 1 economics of agro-waste as a fuel is presented.



Pyrolysis: Pyrolysis is dry distillation of woody biomass. The organic matter is heated above 400°C in the absence of air. This results in the release of a variety of energy rich products, both gaseous and liquid. Solid residue of pyrolysis is charcoal which in itself is a good energy material. The quick heating of organic material yields more gaseous, while slow heating, increases the percentage of the liquid factions. Presence of tars & pyroliginic acids in the products of pyrolysis makes them unsuitaple as engie fuels. The oils commonly formed via pyrolysis, are complex, mixture of hydrocarbons, ketones, aldehydes and other organic compounds, while the gases contain carbon monoxide, carban dioxide hydrogen, ethylene, methane, ethane, and other hydrocarbons. Pyrolysis of woody biomass is a versatile process having potential to provide a wide range of fuels from different types of biomass.