Biomass densification

Introduction

Briquetting is densification of biomass so as to improve its combustion efficiency and make handling more convenient. The efficiency of briquette stove can be as high as 26 percent compared to a traditional stove which has efficiency of 12 percent or less (WECS, 1985). Several types of briquettes using different raw materials are manufactured in Nepal.

Rice Husk Briquette

Rice husk briquette was introduced in Nepal in 1982 and these briquettes are commercially available. Briquettes are produced by compacting rice husk by a screw through a die that is heated to 300° C. The briquettes are cylindrical in shape and a hole in the middle facilitates airflow. It has a calorific value of 4000 kcal/kg and can be burned in ordinary or air induced stoves.

Beehive Briquettes

Beehive briquettes utilize low value loose biomass such as agricultural and forest residue, which are normally difficult to handle and give low thermal efficiency. The process involves partial carbonization of biomass in a Charring Drum, mixing of char with 20 to 30 percent bentonite clay, followed by compaction in a steel mould. The briquettes are cylindrical in shape with a diameter of 13 cm and height of 9 cm and have 19 holes.

Biocoal Briquette

Biocoal Briquette is a composite fuel of biomass and coal with different proportion of biomass ranging from 10 to 80 percent. Initial experiments have been successful but some more research and development is required before the technology becomes commercially viable.