Recycling wood chip waste
Bristol’s new city history museum runs on wood pellets. It’s heated by a biomass boiler, part of a masterplan to reduce the council’s carbon emissions.
The green boiler is one of a number installed in the area, designed to improve the museum’s energy efficiency. It is part of Bristol’s 10:10 campaign: a 10% drop in CO2 emissions by the end of 2010. The council has established a local wood-energy supply chain, from recovering the wood chip through to installing biomass boilers in public buildings.
The wood fuelled boilers provides carbon neutral heat to the museum. While it still releases CO2 when burned, the wood only emits the amount of CO2 that the trees absorbed when growing, roughly equal to the amount they would have released when they decayed.
In the 21st century the holy grail is a truly green, carbon neutral fuel source. Most alternative projects struggle to achieve even modest efficiencies, not for want of scientific innovation, but because delivery to the end user dents the overall rating. The ultimate solution is one that can marry an advanced process with a local resource.
Wood chip is a by-product of tree management everywhere and viewed like any other low grade industrial waste, as an inconvenience. But wood chip is rich in natural energy, if only it can be liberated efficiently. As a fuel it presents an obvious challenge: it’s wet. Conventional methods of extracting energy from fresh wood generate more steam than electricity. This is where gasification comes in. A new generation of burners have rewritten the rule book on converting raw material into heat.
Where we’re going we don’t need roads
Gasification is complicated to explain as it is essentially a chemical reaction. Remember the end of Back to the Future when Doc returns with his DeLorean and feeds rubbish into the engine before taking off into the sky? Well gasification can turn rubbish into energy – not quite as simply as he did though! The feedstock (what you feed into the process) must be carbon-rich, like coal or wood. It undergoes a process involving the injection of oxygen, air or steam, while subjected to high pressure. The process can produce a flamable gas (hence ‘gasification’) which can even power vehicles (maybe not time machines!), but in the case of wood chip boilers the gas is burnt to produce heat.
The great advantage of gasification is that it is very green and some of the newer processes have remarkable efficiencies of 80% and above, compared with traditional processes that struggle to achieve half that. The cost savings from using wood fuel can be between 25% and 50% less than a fossil fuel system. So householders could make savings of around £500 a year and businesses could easily be saving tens of thousands, if they converted to wood fuel.
This technology has a very bright future and since the fuel doesn’t have to travel very far, it has the potential to offer some truly sustainable solutions to our future energy requirements.
Bristol City Council picks up awards for its commitment to tackling climate change. It was named the UK’s ‘Most Sustainable City’ and was the only UK city to be short-listed for the European Green Capital Awards. But they’re not alone in the South West, in fact the Regional Development Agency was awarded £3 million in April 2008 by DEFRA (the Department for Environment, Food and Rural Affairs) to invest in 30 bioheat projects. Once these are all up and running they will provide the region will be in excess of 37MW of renewable heat and save an estimated 7,000 tonnes of carbon a year.
“…as boilers come up for renewal we are replacing them with Biomass. As well as the contribution to the council’s carbon reduction programme, we are anticipating cost avoidance as a result. We estimate the council will save at least £2500 each year on fuel costs at The Octagon Theatre, for example,” said Keith Wheaton-Green, Climate Change Officer at South Somerset District Council.
If you’re interested in biomass and gasification energy sources, these links may be of interest:
Centre for Sustainable Energy helps people and organisations meet the challenges of rising energy costs and climate change
Bristol City Council Biomass Study
The BIOMASS Energy Centre owned and managed by the UK Forestry Commission, via its research agency Forest Research
Bristol Green Capital programme
South West Wood Shed run by Regen SW
Commercial:
UK Biomass Ltd a sustainable fuels project management company
Biofuels Media Ltd runs various study tours to BioEnergy facilities
Wood Energy Ltd is a leading specialist supplier of high efficiency automatic wood heating systems
