Agrofuels are fuels from the agricultural sector, different from fuels derived from forest or industrial wood. They include perennial crops (miscanthus, short rotation coppice, etc.) and some co-products of agricultural plants (flax, hemp, straw, etc.). Following the first transformation process, they can be used as fuel in boilers specifically designed for using this kind of biomass.
Agrofuels can have woody origin (short rotation coppice, hedges, etc.) or being lignocellulosic materials (miscanthus, tall fescue, linseed, etc.).
- Woody agrofuels are generally harvested in the form of whole stems or directly crushed into wood chips with a 50% moisture content. A drying phase of at least 6 months is required for use in a biomass boiler. The ash rate is lower than in the case of lignocellulosic fuels;
- Lignocellulosic agrofuels are harvested by forage harvesters generally with a moisture content between 10 and 25%. These fuels do not require drying and can be used directly in biomass boilers. The ash rate is higher than that of wood fuels, and the ash melting temperature is lower.
Transformation and uses
Agrofuels can be used in bulk or submitted to an additional transformation phase (torrefaction, densification, etc.). The increase in energy density is useful when the fuel is used in large installations.
Like woodchips, agrofuels are used in biomass boilers. Specific settings will optimise combustion and ash production.