Boilers are available for burning straw for domestic heating and constitute an almost carbon neutral source of heat as the carbon is recycled annually. Various sizes of bales can be used and are usually batch loaded by tractor. There is nearly always a hot water storage accumulator employed to store the heat. Some of them can be used to burn other biomass fuels such as wood waste. The cheaper end of these boilers tend to be quite inefficient and polluting but the better ones have secondary combustion systems which burn off the smoke.
It is important to get the design of the accumulator and associated pipework correct, and also the header tank which usually needs to be able to cope with a large expansion of the water in the system.
There are three possible drawbacks
- Being light compared with their volume, considerable dry storage area is required nearby for the bales
- The boilers themselves are large: a domestic boiler of 40 kW output will be about a metre high by a metre wide by nearly 2 metres long
- Batch feeding may be required two or three times a day so this can be difficult to organise. Probably the best situation for straw bale heating is a large farm building where staff are available to feed the boiler.
There is an interesting Navitron forum with some discussion of the practical aspects of burning straw and biomass
