The UK’s Drax power station has embarked on what is believed to be the largest biomass co-firing project in the world in a bid to reduce its carbon dioxide emissions by 15 per cent.
Drax Group plc, owner of the 4000 MW coal-fired plant in North Yorkshire, has awarded Alstom a Euro63 million contract to build the main processing works for a new 400 MW biomass co-firing facility at the plant. It says it will award further contracts for the direct injection equipment and the rail unloading facility during the next few months.
The main processing works will receive, handle, store and process various biomass materials ready for direct injection into the power station’s boilers. The 1.5 million tonne/year facility will enable the plant to achieve ten per cent co-firing and reduce CO2 emissions by over 2 million tonnes/year.
Dorothy Thompson, chief executive of Drax, said: ‘Delivering significant fuel diversification and carbon abatement is central to our business strategy. Meeting our ten per cent co-firing target is key to achieving our goal of 15 per cent carbon abatement and this contract represents a major milestone in the execution of our co-firing project.
‘At Drax, we are only too well aware of the need to tackle climate change and we firmly believe that we are part of the solution. We have a role to play in the transition towards a low carbon economy whilst delivering reliable supplies of electricity.’
Work will begin immediately to prepare the site and construction is scheduled to begin in the second half of 2008. Commissioning of the project’s first phase will start in late 2009.
Drax has developed the ability to co-fire biomass materials with coal over the last five years. It is also implementing a turbine upgrade project, which will deliver a further 1 million tonnes/year saving in CO2 emissions and enable the plant to reduce annual CO2 emissions by 15 per cent based on current output levels by 2011.
Sustainability issues
Since embarking on a co-firing strategy, Drax has implemented a specialist global procurement team to source reliable supplies of biomass material. Although keen to find mainly UK sources, volatility in the agricultural market and a relatively undeveloped energy crop supply market have forced it to look for supplies overseas.
‘Recent rises in crop prices – for example wheat and rape seed – mean that farmers are getting a better income for these crops than they would for energy crops’ said a Drax spokesperson. ‘It is currently a volatile market and we need to find a sustainable source and mitigate against risks.’
The global nature of its current biomass supply chain mirrors that of Drax’s coal supply chain where half of the plant’s needs are imported and half are from the UK, says the company. A diversified approach will reduce biomass supply chain risks until the UK energy crop market is more established.
‘It’s a catch-22 situation; farmers don’t want to plant energy crops until they can be sure of a market for the end product, and they won’t see that until our project is in full swing’ said Drax. ‘When we are up and running then farmers will have more certainty, and over time we will see a dramatic improvement in the biomass supply market in the UK.’
Drax is keen to point out that importing biomass from overseas will have little affect on the company’s carbon ‘footprint’. When considering the carbon emissions associated with mining and importing coal, the production and import of biomass represents a ‘terrific saving in CO2 emissions’ the Drax spokesperson told MPS.
The company also cites the 2006 biomass co-firing review conducted by the UK government, which included an analysis of the carbon footprint of transporting fuel and found a negligible impact. It is also working towards the standards of the Forest Stewardship Council (FSC), a non-governmental organisation that promotes the responsible management of the world’s forests.
‘We look closely at sustainability when signing contracts’ said the Drax spokesperson. ‘From the business perspective it is the right thing to do … we need to be sustainable.’
But sustainability has many facets – including protecting from climate change – and the United Nations has voiced its concerns over the increasing demand for energy crops and the impact that this is having on food crop production as well as on biodiversity. Drax believes that the type of biomass it is using – mainly woody crops grown on marginal land and residual agricultural products such as sunflower seed husks – is not the type that the UN is concerned about.
Technology choice
The ability to achieve ten per cent biomass co-firing is largely down to the selection of direct injection technology. When Drax initially started using biomass in its boilers, it simply ‘sprinkled’ the biomass fuel onto the coal conveyor prior to milling. The company found, however, that this process limited the amount of biomass that could be used because the fuel was not always mixed effectively. It therefore decided that direct injection of fuel into the boiler would give better results and allow it to increase throughput.
The company is also planning to award a contract for construction of a rail unloading facility for biomass supplies in the next few months. Initial deliveries will be by road but Drax says it is committed to using rail for deliveries wherever possible in order to reduce emissions and mitigate the impact on the local community.
Turbine upgrade
Drax is equipped with a total of 30 steam turbine sections as each of its six units has one high pressure, one medium pressure and three low pressure sections. Under the current turbine upgrade programme, 24 of these will be replaced in order to increase the plant’s thermal efficiency and reduce emissions.
The £100 million project – involving the replacement of all of the high pressure and low pressure turbines – will improve the plant’s efficiency from 38 % to 40 % and avoid 1 million tonnes of carbon dioxide emissions per year.
This investment – and that in the plant’s biomass co-firing system – involves some risk, given the uncertainty over the future of the carbon market post-Kyoto. Under the current phase of the EU’s Emission Trading Scheme, Drax has emission allowances equivalent to 9.5 million tonnes of CO2 per year, but currently emits around 22.5 million tonnes of CO2 in a year. It is clearly in the company’s interest to reduce its emissions in such an environment and it believes that other utilities should follow suit. More long-term certainty is required, however, before others follow its lead.
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