Welcome to our second Big Green Debate! This time we are taking a look at the issues surrounding the use of biomass as a source of energy. Jacob Williams points out the concerns surrounding biomass energy whilst Robert Pass makes the case for its use.

Please note that there may be a certain level of devil’s advocate in this debate, and the views expressed may not be the real opinions of the writers.




If burning biomass releases carbon, how can that be a good thing? 

Well, the key difference between biomass fuels and fossil fuel, is that burning fossil fuels releases carbon sequestered millions of years ago back into the atmosphere as carbon dioxide. Burning biomass fuels however, releases contemporary carbon recently taken up by the growing plant. If wood fuel is sourced from well managed woodlands, then carbon released from the wood during combustion will be removed from the atmosphere as the remaining trees and seedlings photosynthesize.

Or so the theory goes. In practice, there are other energy inputs that affect this carbon-neutral balance, for example, emissions that arise from fertilizer production, harvesting, drying and transportation. So, if you use biomass wood it is vital to source your fuel from sustainable, local sources!

This is not impossible, but it is getting more difficult as the demand for British timber far outstrips the supply. In the UK, total wood production is around 8.4 million (dry) tonnes a year. According to the Forestry Commission, the number of biomass fired power stations that are planned in the UK will lead to an increase in timber imports from 20 million tonnes now, to 50 million tonnes in 2015. Such a large new demand for wood is likely to mean more industrial tree plantations, more deforestation and more emissions. 

Using biomass for large scale thermal electricity generation is nuts! Higher efficiencies are achieved in generating heat for small-scale local generation facilities. This can be sustainable if some golden rules are followed: the use of biomass must not outstrip domestically available biomass resources; biomass production must not interfere with wildlife or involve the diversion of land away from food production; biomass systems must use effective and well maintained filters. These filters capture carbon and other pollutants before they enter the atmosphere.

There are a number of companies that manufacture pellets or briquettes made from sawmill and arboriculture waste that has been produced in the UK. The combination of low moisture content and highly compressed material gives pellets a high volume energy density, typically three to four times that of wood chips.

Biomass is not a silver bullet. It will not even get close to replacing all of the fossil fuels the planet burns, either for electricity or to keep warm, but it can form a small part of the solution. 

Robert Pass



Biomass boilers are increasingly being seen as a perfect solution for our heating needs whilst using a low carbon fuel, but this approach has some fundamental issues.

With biomass it’s all about where the fuel is coming from. The problem is the scale at which we are using biomass fuel. The use of biomass boilers has increased by 25% in the last two years. This planet has a finite amount of land and, no matter what we think, that land is not all for human use. So what we should first ask is, whether we have sufficient space to grow enough food to feed an ever increasing population. Adding to this that we as a race are still primarily omnivorous, means that we need to grow even more to feed livestock. We also still need to have the space to house the population, keep enough greenery around to live in a pleasing environment, as well as growing and harvesting biofuel crops.

We are already struggling with all these; food production and living space being basic needs, which are vital for our existence. The amount of the plant matter left for biofuel is also not self-renewable, because, again, the amount that plants self-renew in a year is finite, and that needs to be used for building, food production and medicinal needs.

The only way of using biomass in a sustainable way is by only using waste by-products from more valuable productions, as well as very well managed systems of forestry. If this is done, then it becomes conceivable that it could be sustainable. However, experts say biomass boilers emit NOx (nitrogen oxides) and particulate emissions as well as human carcinogens. It does appear to be hypocritical that we are switching to using biomass boilers because our traditional fossil fuelled boilers pollute the air, when biomass emissions are hazardous themselves.

Estimates of the sustainable biomass energy potential for the UK or EU vary but it is certain that the figure is closer to 10% than 100% of total energy use. Furthermore, biomass supplies appear to be declining. For the world as a whole, carbon stocks in forest biomass decreased by an estimated 0.5 Gt annually during the period 2005–2010/12. Clearly, burning more of it won’t improve this situation. 

In the same way that we would not be able to plant enough trees to offset the burning of fossil fuels, biomass is unsustainable. This is because it is unlikely we will be able to produce enough fuel because land space is finite and claims already exist on it, for example for farming, living space, and so on. In order to have truly sustainable energy our main aim should be to reduce energy use and demand, not to simply find new things to burn.

Jacob Williams