Biomass can be used in a variety of forms to recover energy.
We have been using biomass in the form of wood and twigs for thousands of centuries for heating purposes. In many domestic and industrial sectors worldwide, biomass is still used in its raw form – just cut the tree branches or collect the twigs and use them for heating.
At the same time, many industrial sectors especially require biomass in a more dense and compact form. There are some reasons for this:
1. Biomass in a more compact form is easy to transport, and at less cost than biomass in raw form – just visualize a truck carrying twigs and tree branches against a truck carrying biomass that has been cut into neat chips
2. For some applications, it is required that biomass is available in a more dense form rather than as loose biomass.
3. Storing compact biomass is much easier and less space consuming than storing loose biomass
For the above reasons, compacting biomass is an important activity today in the biomass energy field.
There are two main types of compacted biomass – pellets and briquettes.
Many times, I have seen people getting confused between the two, so let me explain how each is different
Think of bricks when thinking about biomass briquettes. These are compacted biomass that is of the size of a brick – typically with diameters of about 60-100 mm, and varying lengths. The shapes of biomass briquettes could vary – they could be cylindrical or like a regular solid brick.
Biomass pellets are much smaller in size, typically 5-10 mm of varying lengths. These shapes could vary too, but usually they are in cylindrical form.
While biomass pellets and briquettes could be used interchangeably for some heating or power generation applications, it is usually seen that pellets are preferred for the household heating sector and also by some biomass power plants. In these cases, these applications require biomass with smaller diameters. For many applications involving furnaces or hot air generators, either pellets or briquettes could be used.
Typically, biomass pellets cost significantly higher than biomass briquettes, sometimes thrice as much. This is owing to the higher cost of making pellets, as well as owing to the fact that pellets are in many cases sold in retail (hence a longer supply chain) while briquettes are usually sold in bulk to businesses.