‘Biomass’ is a word that we have all become increasingly aware of over recent years as the need to do something to break our ongoing dependence on fossil fuels has risen up the political and popular agenda – but first things first, just what is biomass?
Strictly speaking, biomass is the biological material that makes up living organisms, or those which were alive until quite recently, and their by-products – which actually includes you, me, all our garden plants and a whole lot of manure!
In terms of biomass energy, however, it’s generally taken to refer to principally plant-derived material, and often wood in particular.
Biomass fuels fall into three broad types:
- Energy crops – plants grown specifically as fuel; this category includes the likes of Elephant Grass (Miscanthus) and Short Rotation Coppice (SRC) trees such as willow and poplar.
- Woody residues – the kind of ‘waste’ material that generally comes from managed forestry operations or as a by-product of wood-using manufacturing processes.
- Agricultural residues – animal slurries and crop wastes; for obvious reasons, this third group is seldom relevant for domestic energy use!
Whether you opt for purpose-grown SRC fuel, logs and off-cuts from the local woodman, or specialist compressed pellets, when it comes to heating the home, if you want to use biomass, then you’re almost certainly going to be buying wood, in one form or another.
Wood for Fuel
Although in many ways the developed world is only just beginning to rediscover the potential of burning wood, across the globe it never stopped being a vitally important fuel. Around 80 per cent of the wood harvested in developing countries – and just over half of all the wood collected around the world – forms the population’s primary source of energy to meet heating and cooking needs.
In the UK, heating represents around 40 per cent of the total energy market (excluding transport) and wood is ideal for this purpose, especially in rural areas away from mains gas, where it can compete very favourably with oil and coal. It can also have the added potential community bonus in country areas of providing much-needed local employment in the forestry and transport industries.
Economics and Energy Value
With very few exceptions, wood burning is the cheapest of all forms of renewable energy to install – although unlike wind or solar systems, once in place, there will still be running costs to pay, whenever you top up with another load of logs!
Critics of biomass fuels often point to their low energy density – how much weight of material you need to burn to get a given amount of heat out – and it’s true that looked at from this standpoint, wood doesn’t fare just so well compared with conventional fuels. Having a value of around 5kWh/kg, on a weight-for-weight basis, it contains roughly 60 per cent as much energy as coal, 40 per cent as oil and only 30 per cent as natural gas. It’s also quite bulky to store and, with the exception of pellets, not particularly easy to handle automatically – which means you always need someone on hand to keep the fire stoked and burning.
However, that doesn’t really tell the whole story. According to price comparisons made by the Government’s Biomass Energy Centre in November 2008, wood competes very well with its rivals. With a cost per kWh (excluding VAT) of around 4.2p for chips – and only 2.3 p for pellets – wood matches both natural gas and oil (4.2p and 4.5p, respectively) and easily beats bulk LPG purchases at 7.1p/kWh. Never-the-less, wood prices do vary considerably in different parts of the country and there are often minimum amounts or other conditions – so it definitely pays to do some fact-finding about local sources and suppliers for yourself.
Remember too that how you burn your wood matters. An open fire is at best typically only about 25 per cent efficient – and at worst perhaps as little as 5 per cent; by contrast efficiencies of 80 per cent are routinely possible with a wood burning stove.
Benefits of Biomass
Biomass fuels have a lot going for them in terms of straight-forward energy saving, lowering utility bills and reducing your carbon footprint, along with providing a range of potential additional benefits to the local community and economy.
- Properly managed, biomass fuels offer a truly sustainable source of energy, which could also help the UK ensure partial energy self-sufficiency in the future
- In rural areas particularly, locally grown biomass means low transport distances which equate to reduced additional embedded energy and fewer ‘fuel miles’
- Biomass fuels tend to be low in sulphur and other pollutants
- Burning wood residue allows a waste product to be a useful fuel instead of simply ending up buried in landfill, with all the environmental problems that brings
Like wind and water power, biomass fuels are another energy source that our forefathers knew all about, but that we sometimes seem to think we’ve invented for ourselves. Clearly, as the old saying goes, there really is nothing new under the sun!