The biomass industry is booming as governments search for low-carbon fuels. But should we be a bit more cautious when it comes to playing with fire? Libby Peake investigates
Long before there was gas, there was wood. And though the modern, Western world has been largely dependent on fossil fuels like gas and coal to meet our demands for electricity and heat, the humble tree is making a comeback, along with its consorts – offcuts and crops. As supplies of other energy sources begin to run out and governments throughout the world scramble to cut carbon, biomass – touted by many as a ‘zero carbon fuel’ – is becoming an increasingly attractive energy source.
Since the Renewables Obligation was introduced in 2002, licensed electricity producers in the UK have been obligated to source an increasing proportion of their electricity from renewable sources – wind, hydro, tidal, solar, hydroelectric, but also biomass. Consequently, interest in biomass, especially from large electricity producers, has been rising dramatically over the past few years.
‘Biomass’ is perhaps a harder fuel to define than some of the other renewables, as it comes in many forms, whereas a wind turbine is a wind turbine is a wind turbine. It’s largely not a case of chopping down trees and feeding them into incinerators as you might imagine, though – many bits suitable for combustion are the scraps and dust left over from saw mills (up to half of what goes in, surprisingly), as well as forestry residues – branches and whatnot taken off during felling operations or tree surgeon activity – and reclaimed wood, predominantly from the packaging, construction and demolition sectors. You can also combust agricultural residues like straw and dedicated bioenergy crops, predominantly short rotation coppice willow and miscanthus, or elephant grass, in the UK. Dr Geoff Hogan of the Forestry Commission’s Biomass Energy Centre notes these types of fuels are less common, though, as they have to “pay their way” and tend to be prohibitively expensive when residues are available for free. Basically, any organic material with a moisture content below 50 per cent (wet material takes longer to burn or requires energy to dry) is a prime candidate for combustion as biomass fuel.