There are different types of biomass boilers. Log boilers usually will just burn logs. Some models are capable of burning turf and coal also. However, burning turf in a boiler which you have to manually feed may not be the best idea as it has a low calorific value, i.e. you will spend a considerable amount of time shovelling turf into the boiler. Often when a fuel has a low calorific value it also means more ash is produced, so you will have to rake out the ash more frequently too.

Gilles Wood Gasification Boiler

Pellet boilers obviously burn wood pellets, which are fed automatically via transport augers. More often than not, you will be able to fire logs into them too.

Gilles Pellet Boiler

Woodchip boilers are more versatile; in addition to burning woodchip they also burn pellets and logs.

Gilles Woodchip Boiles

If you are growing miscanthus you may wish to burn it in a woodchip boiler, in chipped or bailed form. If it is in chipped form it can be fed automatically via augers, like wood chip and pellets. If you decide to burn it in bailed form it needs to me manually fed, like logs. Burning miscanthus in a standard wood boiler causes the ash to melt and then form a hard crust on the burning chamber called clinker. This problem is easily avoided by co-firing with woodchip. Burning miscanthus without your own supply may not be the best idea as it is bulky and does not have as good a calorific value as pellets and woodchip. In other words, miscanthus only makes sense when you have a cheap local supply or you’re growing it yourself.

Willow and other forms of wood such as blackthorn are fantastic for burning in biomass boilers as they have a good calorific value. If you have a local supply or a growing this yourself you should certainly consider burning it in a woodchip boiler. Like all wood fuels you will want to put it in a shed for 6 months to a year to dry out, season. The only disadvantage is that because there is more bark in willow you will get a bit more ash and have to rake ash a bit more regularly.

Burning other fuels such as oats is possible, but you will need to ask your boiler supplier to help you configure the boiler as oats burn very hot. Once again, co-firing is a good idea in this scenario.

It is possible to burn waste wood products such as sawdust, although, care needs to be taken due to number of small particles.

Moreover, you can burn straw and hay in a biomass boiler, but once again ask your boiler supplier for advice.

You may be interested in reading tomorrows post about fuel, as it will advise you on important considerations such as moisture content and containments.