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UK wood waste is the answer to effective small-scale CHP

Already widespread on the continent, wood-fired biomass solutions providing Combined Heat and Power (CHP) are becoming increasingly attractive in the UK. The Department of Energy & Climate Change believes 10% of Britain’s energy could come from biomass by 2020, making a significant contribution to the EU 20-20-20 targets for renewables.  

Affordable, reliable energy, with the potential to cut CO emissions by as much as 90% compared to gas for instance, are key reasons, while fuel cost savings are another. Woodchip biomass or pellets from sustainable sources are significantly cheaper than fossil fuels and, with a growing number of suppliers, it is an increasingly reliable and competitively priced resource.

Recent analysis from the government’s chief scientific advisor on energy however, suggests that importing and burning timber from North American forests to feed mega biomass power stations like Drax, can result in higher greenhouse emissions than coal-fired. So is biomass still the answer?

Burning UK waste wood rather than virgin timber is a major factor in delivering effective and ‘green’ biomass solutions and the immediate opportunity lies with small-scale and local CHP solutions. Constructed on site for industrial scale users, or near to communities, these district heat and power solutions will deliver cheap renewable energy on their doorstep.  

There are a number of reasons why this makes sense. Small-scale solutions in the 1-5 MWe range are easier to fund, with considerably less risk. They are much quicker to design and implement and importantly, technically proven with dozens of examples across Europe, especially in Scandinavia. What’s more, the bio-energy potential of waste wood in the UK remains substantially underutilised.

Waste wood falls into two broad categories. The first includes waste material from construction, the furniture manufacturing sector and municipal waste. Somewhere in the region of 5 million tonnes per year of this material is generated in the UK. According to Wood Recycling Association (WRA) figures, output from wood recyclers rose to 2.3 million tonnes in 2013, but a significant proportion, especially the municipal wood waste that is difficult to sort and segregate and lower quality materials, still goes to landfill. Yet according to WRA estimates, we continue to export in the region 500,000 tonnes, mostly to biomass in Europe.

A second largely untapped category includes forestry residues - material left over from harvesting and forest operations, which has no other useful purpose - this includes trimmings, stumps, bark, deadwood and small branches. While much of this is often simply left on the ground, it is a perfect fuel source for modern, small scale, clean burn biomass solutions.

A typical Waste Incineration Directive compliant CHP plant for example can convert 6,000 to 80,000 tonnes of UK waste wood - both low grade recycled wood and forest residues - into 170,000MWhr of renewable thermal energy, each year. And Twinwoods Heat & Power in Bedfordshire is a prime example. Due to go live in 2015, the 3.4MWe CHP biomass power station will produce 27,000 MWhr of electricity and 8,000 MWhr district heating annually, establishing the plant as a locally important source of renewable energy.

The state-of-the art clean burn solution will consume approximately 40,000 tonnes of waste wood from commercial and domestic recycling centres per annum and has been designed by Saxlund to provide a minimum of 8,000 hours operation between shutdown inspections. Under the contract, Saxlund will manage all aspects of design, manufacture, installation and commissioning of the plant, key components of which include the fuel handling system with push floor and conveyors, the combustion grate, integrated high pressure steam boiler and steam pipework to feed a Siemens turbine system.

Of course improvements to the collection, aggregation and sorting infrastructure for waste wood and forest residues and further restrictions on waste wood to landfill will be important factors for the waste wood biomass sector. To a degree both are dependent on the other. However, with the efficiency of biomass fired CHP almost double that of much larger power stations, together with the government renewable heat incentive and the opportunity to divert waste wood to fuel, there has never been a better opportunity for investors, energy companies, large energy consumers and the waste wood processing sector.

But, while the opportunity is clearly there, the right technology, appropriate investment partners and suppliers who are in it for the long game are crucial in delivering enduring and successful energy projects.

Matt Drew, managing director, Saxlund International

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