https://en.wikipedia.org/wiki/Biomass_briquettes
Biomass briquettes are a biofuel substitute made of biodegradable green waste with lower emissions of greenhouses gases and carbon dioxide then traditional fuel sources. This fuel source is used as an alternative for harmful biofuels. Briquettes are used for heating, cooking fuel, and electricity generation usually in developing countries that do not have access to more traditional fuel sources. Biomass briquettes have become popular in developed countries due to the accessibility, and eco-friendly impact. The briquettes can be used in the developed countries for producing electricity from steam power by heating water in boilers.
The briquettes are fired with coal in order to create the heat supplied to the boiler. Biomass briquettes are built from recycled green waste, producing less greenhouse gas admissions because the matter has already completed part of the carbon cycle.
--- Wikipedia