Briquettes are cubiform, prismatic, or cylindrical units with a diameter of more than 25 mm produced by compressing milled biomass (wood chips, sawdust,agrofuels, etc.). These briquettes are used in appliances capable of burning traditional logs (agrobriquettes might require a polyfuel appliance), but have the advantage of being much more homogeneous in terms of size, composition, moisture and calorific value.
Wood briquettes are mainly produced by industries of the primary processing of wood, mainly sawdust or chips. These elements are sometimes refined before being compressed.
Agrofuel briquettes are produced from wood chips from hedges, short rotation coppices, or herbaceous biomass (e.g. miscanthus).
No chemical additive is used (natural additives such as starch might be used in limited quantity), the cohesion is ensured by the natural binders of the biomass.
To be comprehensive, there are also briquettes made from animal litter compressed (e.g. horse litters).
The densification of wood and agrofuels can increase the energy content of the fuel per unit volume, making transport and storage more efficient.
The densification process also has the advantage of transforming a relatively heterogeneous fuel into a homogeneous and standardised product.