Sally Spencer: What is the rationale behind converting coal-fired power plants to biomass?
Matt Willey: Sustainable biomass has a strategically important role to play in the UK’s renewable energy mix and is critical for meeting the country’s carbon reduction targets.
It is the only renewable which can be despatched to meet both baseload and flexible demand at scale in the UK, and is therefore the perfect complement to other intermittent and inflexible forms of power generation, such as wind and nuclear.
Converting an existing power station makes use of an existing asset, its grid connection and other infrastructure. As such it is capital efficient and, therefore, cost-effective.
Intermittent forms of generation rely on biomass and fossil fuel power stations for back-up, adding to the costs of intermittent technologies, such as wind. According to DECC’s Bioenergy Strategy, the costs of meeting the UK’s 2050 carbon targets are estimated to be £44bn higher without sustainable biomass.
Drax Power Station is a national strategic generating asset, but it is also the country’s largest single-site carbon emitter. Converting units to burn sustainable biomass in place of coal allows Drax to retain that critical role while significantly reducing its carbon emissions in a cost-effective way.
SS: Why did Drax alter its plans to build dedicated biomass power plants in favour of converting existing coal-fired ones?
Following a review of the support for renewable technologies under the Renewables Obligation, the government’s policy for electricity generation from biomass clearly favoured biomass conversions rather than dedicated biomass plant. Drax responded to that change in policy.
SS: How complex was the conversion?
MW: Nothing like the scale of the biomass conversion at Drax Power Station has been attempted anywhere in the world. There are no ‘off-the-shelf’ solutions and much of the expertise has been developed in-house. We have over 10 years’ experience of working with biomass and have drawn on all of that expertise.
It is not a simple fuel switch. Coal and biomass are very different materials and have to be transported, stored and handled in very different ways. This necessitated the design and construction of bespoke facilities, with safe and reliable operation key considerations.
The capital investment in the biomass project is expected to be in the range of £650m to £700m. That includes investment in the new, bespoke facilities at the Drax Power Station site, as well as in technology to ensure compliance with tighter emissions limits from 2016, and investment upstream in two pellet plants and a port facility in the US.
SS: Was there a period when it was co-firing coal and wood biomass?
MW: We started co-firing biomass with coal in 2003. At first with low levels of 3-4% biomass (by heat) and later, in 2010, up to 12.5%. During that time we learnt much and conducted extensive research and development into increasing the amount of biomass burnt in place of coal.
SS: How much power is generated at Selby?
Drax is the UK’s largest power station, with a potential capacity of around 4,000MW, and is typically responsible for meeting 7-8% of the UK’s electricity demand. Its six units can generate the same amount of electricity as it would take to power over six million homes.
SS: How much wood fuel is required at Selby?
MW: One converted unit requires around 2.5 million tonnes of biomass pellets per year.
SS: Is it still the plan to convert a further two Drax units to biomass?
MW: We plan to have converted three units by 2016 (see p26). With three units converted, Drax will require around 7-8 million tonnes of biomass pellets per year.
SS: Is all the fuel in the form of wood pellets?
MW: Since 2003 we have burnt many different types of sustainable biomass, including forestry and forestry residues, agricultural by-products such as peanut husks, olive cake and straw, and energy crops such as miscanthus and willow. The vast majority of the biomass we currently use comes in the form of wood pellets, but the same general principle holds; those wood pellets are typically low value residues or by-products of other industries and made from raw fibre that often has no other commercial use.
SS: Where is your biomass sourced from and is it ever likely to be sourced from the UK?
MW: Much of our wood comes from the US and Canada, although we do have suppliers in the Baltics and Portugal. The forest industries in the US are vast and create a huge amount of wood that would be wasted if not used for electricity generation.
In the US alone the US Department for Energy estimates that, across the country, 93 million tonnes of forest residues and thinnings, which could easily be recovered at a viable price, are left to rot or burn on site every year.
Canada is another good source of wood – primarily residues and off-cuts from sawmills that would otherwise go to waste.
The reality is that the UK simply does not have the scale of forestry industry or landmass to support our requirements. The UK-sourced biomass we use comes in the form of straw and energy crops that grow on marginal land.
SS: What are the logistics involved?
MW: We are building two new pellet plants in the US – one in Louisiana and one in Mississippi – and a new storage and handling facility at the Port of Greater Baton Rouge. Between them those facilities will allow Drax to self-supply around 900,000 tonnes of pellets per year. We also have contracts in place with third-party suppliers. The UK Ports of Hull, Immingham and Tyne are either already handling biomass for us or are developing facilities to do so. The first 50 of 200 purpose-built biomass rail wagons are now in operation to bring the fuel from the port to the site.
SS: Does the wood fuel have to come from certified sources?
MW: Under the UK’s biomass sustainability policy all biomass used in power generation will have to be sourced sustainably from this year but Drax has been providing its sustainability data for several years already.
DECC is introducing new legislation which will require all fuel to satisfy a range of sustainability requirements, written into the Timber Standard. Wood certified to FSC or PEFC would satisfy these requirements and, ideally, we would like our fuel to originate from sources certified to these standards.
However, we recognise that not all our fuel can be certified by FSC or PEFC and hence we have introduced our own procedures and practices whereby we can ensure its sustainability. These are extensions to our sustainability policy, which we have had in place since 2008. This policy is robust, independently audited and covers a range of issues from maintaining the carbon stock of the fibre baskets we draw from, through to protecting biodiversity and social rights. We also calculate the carbon footprint of every step of the supply chain. This rigorous process is why we are sure our biomass is sustainable and that the carbon savings we are delivering relative to coal are in excess of 80%. Part of our programme is ensuring that the growth of the forest area exceeds the total drain (or harvest) from that area to confirm that our activities are not releasing more carbon from forests than we are saving.
SS: How secure is this supply?
MW: The raw material – woody residues and thinnings – is abundant so we have no concerns about the availability of sufficient volumes. The key is ensuring we have the logistics in place to get material, which in the past may not have had a market, to the ports and ultimately to Drax Power Station. Getting the infrastructure in place demands investment and long-term contracts underpin that necessary investment.
SS: What role have government subsidies played in determining Drax’s biomass plans and what would a future without subsidies be like?
MW: Building a supply chain infrastructure from scratch requires investment and that in turn requires regulatory certainty to secure investor confidence. Support for biomass conversion does end (in 2027) before many other renewables and far earlier than the proposed nuclear support regime. That is one of the reasons why it is much better value, but it is also a reason why the regulatory certainty necessary for investor confidence is needed now.
SS: The timber industry – notably the panels sector – has major concerns regarding biomass displacing some of its own raw material supply. What is your response?
MW: These concerns should not be aimed at Drax or coal-to-biomass conversions. UK wood is too expensive. The point of the investment we have made in the US is to give us access to a market where vast quantities of the residues and thinnings that often have no other commercial use are available to us at prices we can afford. We source very little or no wood from the UK.
