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How to make the most of bio-energy
Posted by Stewart Boyle on 25 September 2013 at 9:18 am
Bio-energy (or biomass) tends to divide a generally pro-renewables audience. Fed by countless images of rainforest destruction, ‘Fuel vs Food’ slogans, and general suspicion of anyone who chops down trees, bio-energy has its fans but its detractors. ‘Do we have enough fuel?’ is a common question with clients and at public meetings. ‘Does it really save carbon?’ is another fed by a well-orchestrated campaign by NGOs and the paper board industry. Yet bio-energy for heating provides 365 days 24-7 reliable and low-cost heating, and under the current renewable heat incentive (RHI) offers a really attractive investment.
I spent 18 months researching and writing ‘The Sleeping Giant Awakens: Bio-energy in the UK’ to try and answer these and other questions. In advance of its official publication I offer below ten practical tips on doing bio-energy right. I focus mainly on the heating sector but with brief reference to biopower and biofuels.
Top Tip 1 - If you want a fully automated wood heating system to replace your existing boiler and heating, forget log boilers and woodstoves – these are not for you. If you don’t mind daily or more frequent loading up with logs and regular de-ashing – including the morning of 1 January after a great party – and have the lifestyle to support this (working from home or a farm), then it’s a good option.
Top Tip 2 – if you have a good supply of your own logs and fulfil the top tip 1 criteria, then a log boiler can be a great investment with rates of return in the range of 12-22% IRR.
Top Tip 3 – always start with the fuel when looking at wood heating boilers. Deciding whether to use logs, wood pellets or chip is the key first step – they each have their pros and cons. Top tip 1 gives some of these. Pellets are very convenient and compact, and it’s still carbon-friendly to get them made and delivered even from the far north of Scotland, but they are more expensive than wood chip and self-supply logs. Ask yourself too, can you actually get the fuel delivered simply and economically? Schemes designed where the only way to get fuel into a storage silo is via a chipper (at £35,000 or £250 a day), or manually or via pallet trucks and builders bags, tend to bump up fuel costs and become a real pain.
Top Tip 4 – get independent and experienced advice on wood fuel handling, choice and design. I’m re-emphasising this because around 50% of wood heating system problems are due to fuel mistakes.
Top Tip 5 – most wood boiler systems work better when linked to an accumulator tank. This helps balance the peaks and troughs of heating demand, as well as provide a bit more ‘oomph’ during peak loads.
Top Tip 6 - boiler sizing is a mix of science, judgement and experience. Avoid suppliers who offer ‘over-size’ boilers rated at greater than your peak load simply to maximise RHI income. That will likely cause big problems in light load conditions and wear out your boiler. For log boilers, a boiler sized at around 80% of peak load and with an accumulator tank sized at 50litres per kilowatt of the boiler is a good ball-park figure. For pellet boilers with an accumulator, which are faster reacting to load demands, setting the boiler size at 70-85% of peak load is quite common. There is a free ‘biomass decision support tool’ available to assess this via the Carbon Trust.
Top Tip 7 – there are a stack of ‘do’s’ and ‘don’ts’ related to running woodstoves well. Most problems for new users arise from buying logs that are not appropriate or paying over the odds at garage forecourts. Buy local and ask for logs suitable for an open fire as these logs need to be barn dried for two years to be sure of a good burn. Softwood and chestnut logs are not the best options for open fires as they spi’, but can be used in woodstoves, particularly when blended with other hardwoods. Oh – and buy a good axe and bowsaw and learn to use them!
Top Tip 8 – one tip on choosing your green car. Electric vehicles are the flavour of the month but at present only offer 25% lower carbon emissions than a decent diesel car. This will improve as the power sector de-carbonises but it will take some time to get there. Biofuels based on bio-ethanol or bio-diesel by comparison offer 50-70% relative savings. My advice – opt for an efficient hybrid car that offers electric vehicle performance and local air pollution benefits in urban areas, but elsewhere, the IC engine linked with blended liquid fuels will offer exceptional mileage range and lower carbon emissions.
Top Tip 9 – a tip on biopower based electricity. Co-firing in plants such as Drax has had a terrible press and green NGOs have suggested it is 49% worse than burning coal. Don’t believe the hype and green PR on this issue. Careful analysis suggests that this assertion is based on very selective and unrealistic assumptions and simply doesn’t stack up. So UK co-firing and pure biopower options offer 60-80% carbon reductions compared to coal.
Top Tip 10 – we have plenty of wood fuel for heating in the UK - in the form of logs, pellets and chip - for the foreseeable future. And yes, we do need to plant a lot more trees and look seriously at energy crops such as SRC willow and miscanthus, but the biggest problem with UK woodland right now is its perceived low value and the lack of management in around half of it. Engage with local woodland owners – some of us offer ‘sweat for logs’ exchanges - and you’ll learn to love the saw and axe as the friends of biodiversity.
‘The Sleeping Giant Awakens’ is one of the most comprehensive books on bio-energy. It also challenges some of the controversies. For many other tips and answers to lots of bio-energy questions, we can offer a special YouGen users book deal. The deal is worth £2 off the cover price (normally £9.99 hard copy and £7.99 digital). Go to www.oneplanetmedia.co.uk/OPM-publications and quote the YouGen Discount Code – YG2013SGA5 .
From the blog
What to expect from your biomass boiler (Aug 2011)
How to choose your biomass boiler installer (Nov 2010)
About the author:
Stewart runs the consultancy arm for South East Wood Fuels. His book The Sleeping Giant Awakens: Bioenergy in the UK will be published in
May 2013. Click here to get a free download of the first chapter and put Free Download in the subject line.
If you have a question about anything in the above blog, please ask it in the comments section below.
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