Biomass boilers come in one of three forms : log boilers, pellet boilers and wood chip boilers. All of these technologies are eligible for the Renewable Heat Incentive(RHI).
The cheapest of all biomass systems is a log boiler, but with this comes the least amount of automation and the most work for the end user as you will have to load logs in to the boiler and light it on a regular basis.
Pellet boilers are the most popular as these offer the most versatility in that you can purchase pellets either in easily handled bags or in bulk and they offer a great deal of automation and a consistent and uniformed fuel. Wood chip boilers are only suitable for bulk deliveries and are more accustomed to the larger scale systems. Wood chip is less expensive to buy than pellets but the fuel can sometimes be a little variable in quality.
As long as the wood you are burning comes from a managed source then this is perhaps the most carbon neutral of all renewable technologies. This is because the carbon which is released during the burning processed is counteracted by the carbon which is absorbed from the atmosphere during the growing of the trees.