Heating from biomass boilers

So wood fuel is dirty? The recent debate re-opened and ‘fuelled’ no doubt by the announcement that the Drax power station will convert three of its boilers to run on wood fuel, somewhat clouds the debate in a fog (or is it a soot) of confusion.

So let’s look differently at the real issues. What is an appropriate use of wood fuel and what are the various levels of the wood fuel market?

Is biomass for power-only appropriate?

Is using biomass to generate electricity only at Drax, and other such power stations, an appropriate use of wood fuel? Of course it will reduce carbon emissions, but let’s remember that only about a third of the energy of the biomass fuel (or indeed fossil fuel for that matter) used in the production of electricity goes into generating useful energy –from this type of plant. The remaining two thirds of the energy from the large-scale use of fuel is lost, so is this appropriate?

Biomass used for CHP

Contrast this to Sweden, and take as an example the city of Vaxjo. It is the size of Taunton and has a 200 MW combined heat and power (CHP) plant sitting in the suburbs. It supplies both electricity and heating via a district heating underground piped network to some 95% of the city. This is based on an efficient use of wood fuel. Remarkably, the city isn’t covered in ash and the air is clean in what is a very beautiful part of Sweden.

It can be argued that Sweden has much more wood fuel potential than the UK. But, it is being used efficiently, wisely and appropriately. District heating, with distributed heat, linked to electricity generation in combined heat and power plants is more the norm in Scandinavia. Large scale CHP done this way is an appropriate usage, electricity-only is questionable. So it is encouraging to see plans for a green district heating system for Exeter emerging, which would help reduce carbon emissions and result in more energy efficient heat and power for the city.

Biomass boilers used for heat – an appropriate use

The use of biomass fuel to generate heat in 90%+ efficient biomass boilers is also a far different thing to large scale electricity-only power generation in far less efficient circumstances. Firstly, there is a far more complete combustion at these high levels of efficiency so far less wasted energy and an effective use of fuel.

This is reflected in the very low emissions that are generated from high efficiency biomass heating as a result. Figures on the Biomass Energy Centre’s website show an up to 98% reduction in CO₂ from the use of biomass fuels to generate heat, compared to using electricity and 96% when compared to heating oil.

To put this further into perspective, there are new lower maximum emission levels that are due to come into effect in the Building Regulations this summer. The standards will be a maximum of 30g/GJ particulate matter and 150g/GJ nitrogen oxides for all new build and particularly Code for Sustainable Homes developments. OFGEM will also require the emissions from biomass boilers to fall below this level in order to gain accreditation into the Renewable Heat Incentive (RHI).

In fact, high quality and high efficiency biomass boilers including the Guntamatic Biostar, Biocom and Powerchip already fall significantly below the new maximum emissions standards.

A further point is the scale at which biomass heating takes place. Within the Renewable Heat Incentive (RHI) scheme, small-medium biomass (up to 1mW) makes up nearly 70% of heat generated from biomass boiler projects accredited into the scheme.

Treco and our partners have managed a number of installations and successfully gained RHI accreditation for over 53 biomass boiler projects to date. These include a number of 100kW boiler installations including those serving Mornacott Farm, Higher Combe  and the Great Barn, which see a single boiler providing heating to a number of buildings within a district heating scheme on rural estates.

Installations we have recently completed at Menchine  and Hollyfield free range poultry farms feature installations including 400kW and 300kW biomass boiler systems respectively. The systems at this capacity heat multiple chicken sheds with capacity available to heat the farm house as well. Read up on these case studies here.

Locations such as the above are often amongst the 12% of the country off the mains gas network, which are typically in rural, localised and harder to reach areas. They have been reliant for many years on polluting and expensive electricity, LPG and oil. The high cost of electricity in many ways reflects its inefficient production. At around 13.5p per kWh, electricity is the most expensive form of fossil fuel, with LPG at 7.16p and the cost of oil is around 6.3p per kWh, compared to just 2.7p per kWh for wood chips.

Our clients, when switching to biomass boiler heating, are likely to also move to sourcing their own wood fuel from localised suppliers, or even chipping their own wood fuel supply directly into a fuel store to gain the highest fuel cost savings of 50-80% versus fossil fuels.

Much of this localised supply is so far under the radar so as to not even factor in calculations regarding the UK’s overall supply of wood fuel or emissions generated during its localised production or transportation. In fact the availability of localised wood fuel is a by-product of correct woodland management, which stimulates biodiversity, forest growth and carbon capture.

On a local scale, the small scale local producer using 'thinnings' and residues of saw-milling can support more local markets and high efficiency heat-only biomass boilers without even touching the fuel supply being used for large scale power generation.

This boosts the local economy, creating jobs, utilises our own resources sustainably, and not only reduces CO₂, but for off-gas grid users, but reduces the costs of energy, irrespective of any tariff or incentive.

This somewhat undermines claims that wood fuel’s production results in higher greenhouse gas emissions than coal. So let's think a bit more about using wood fuel in an appropriate way, at all levels, to really energise our economy and lower our emissions.