Fuel for your biomass boiler can be supplied by the ton or per kWh.
If you are purchasing fuel by the ton, you should consider the following:
Moisture content: The moisture content of the fuel effects how efficiently it burns. As a general rule of thumb, the higher the moisture the less efficiently it will burn. However, in some cases the fuel can be too dry. The maximum moisture content of the fuel will vary depending on the make and model of your boiler. For example, Gilles wood chip and industrial boilers can burn wood fuel with a moisture content of up to 55% moisture content. This is higher than average.
Contaminants: It is important to make sure that the fuel you are using is free from contaminants such as varnish, glue, paint and creso, as they can cause the boiler to burn at a higher than recommend temperature reducing the lifespan of the boiler. Other containments such as nails and metal can also damage the boiler. The chlorine content of the fuel is very important, chlorine reacts with and corrodes the steel construction of the boiler and can significantly reduce the boiler’s lifespan. An example of a biomass fuel which is high in chlorine is chicken litter.
Ash content: The ash content of the fuel effects how regularly the boiler needs to be cleaned. Pellets usually have an ash content of .5% and for woodchip it’s 1%. Burning logs in a gasification boiler rather than a standard log boiler will reduce the amount of ash being produced from that fuel. The ash from miscanthus burns at a much lower temperature compared to standard wood fuel. Burning miscanthus in a standard wood boiler causes the ash to melt and then form a hard crust on the burning chamber called clinker. There are a number of solutions to this which your boiler supplier should be able to suggest.