With a small patch of woodland containing mainly young ash trees, a patch of willow around the pond and plenty of hedges I’ve long been interested in the potential for burning ‘home-grown’ biomass, from chips, through twigs to logs. So I thought a review of the domestic biomass boiler options was in order…
There are two types of biomass boilers – those fed with pellets and those fed with timber. Pellet boilers can be manually or hopper fed, with hopper feeding allowing a certain amount of unattended operation. Couple hoppers with high degrees of efficiency and the workload for the owner in keeping the boiler running is minimised. For example, Treco claim that the Guntamatic Biostar W boilers will “hold enough fuel for up to a month ….[and are] self cleaning and have ash boxes that only need emptying every 6 – 8 weeks”.
Pellets are small lengths of compressed sawdust, there is no need for any additive to bond the sawdust together as lignin, an organic binding substance present in the wood does this when the pellet is formed under compression.
There are a wide array of boilers available, I’ll concentrate on two of the main ranges available in the UK at the moment…
Baxi offer a number of biomass boilers. They offer two pellet boilers – the Bioflo is manually fed (there’s no hopper so you need to feed it like a traditional boiler) and it can modulate output depending on demand between 3.8kW and 12kW. Then there’s the larger Multiheat boiler – available in 15kW, 25kW and 43kW versions with an integrated hopper. There’s also the Solo Innova, a log fuelled boiler that comes in 20kW, 32kW and 48kW thermal output versions.
Treco supply a wide range of boilers, including those from the Austrian manufacturer Guntamatic. For domestic purposes I’ll consider the Biostar that is available in four different fuel supply options; the Flex (the fuel store can be physically distant from the boiler with the two connected by a flexible vacuum tube), the Box (similar to the Flex, but with the fuel store included in the price), the W (with a large hopper that only needs filling Weekly), and the Biostar Duo (which also burns logs). There are 12kW, 15kW and 25kW versions.
So how much do they cost?
A web search for the Baxi boilers gives me a lowest price of just under £9,000 including VAT for a Bioflo (I’ve also seen them priced over £11,000), with Multiheat boilers at just over £6,000 for a 15kW model and £7,000 for a 25kW version (although I’ve also seen them priced at more £2,000+ more) and Solo Innova at £4,800 for a 20kW model and £5,300 for the 32kW model (again I’ve also seen these priced at around £1,500 more). Treco / Guntamatic Biostar boiler prices range from just over £11,000 to just over £14,000 (excluding VAT).
You’ll also need to pay for installation and a suitable flue if you haven’t got one already.
Pellets v Timber
Personally I’m not keen on the idea of pellets. Too proprietary and too vulnerable to volitile markets for my liking, but I can see their value as an alternative to oil or gas where a local source of timber is not available. Additionally, they take a lot of the manual labour away and reduce the time demands made by logs in their splitting, stacking and seasoning. Pellets also offer the convienience of hoppers and unattended heating. My ideal of a biomass boiler that will burn any type or condition of biomass seems to be some way off as the biomass boilers I’ve been reading about require, seasoned, sizeable, well prepared timber.
Costs and benefits
For comparison I looked up the statistics for my current multi-fuel stove. It’s a Charnwood Country 16B Multi-fuel central heating boiler with output statistics as follow:
- Space Heating Output (BTU) – solid fuel = 5.5kW (18,779) wood logs = 7.7kW (26,291)
- Water Heating Output (BTU) – solid fuel = 13.7kW (46,778) wood logs = 8.2kW (27,999)
This cost something over £3,000 fitted for 15kW or so of combined output.
At a guess I could get a 20kW Baxi Solo Innova installed for somewhere between £6-7,000 and if I wanted the full ‘hands-off’ luxury of a 15kW Biostar boiler I’d be looking somewhere around the £13-14,000 mark. So not cheap in comparison to more traditonal heating solutions such as my multi-fuel boiler/stove. The Energy Saving Trust (EST) tell me I can get a standalone pellet stove for £4,300 installed – I’m just not sure who from!
So how and why am I going to pay for this?
Treco claim that “Your fuel bill will drop by at least 30% when you make the switch from oil [to biomass]” so there’s an immediate saving when switching from oil of several hundred pounds a year based on current fuel oil prices (and it looks like that saving is only likely to grow). Even with prices as they are, as of writing the annual costs of a biomass system are likely to be more that those of a mains gas powered system.
The main advantage in comparison to more traditional heating and hot water solutions such as wood burning are the relatively low amounts of ash and the opportunity for unattended operation. You can get that from gas (if you’re on the mains) or oil, but if you want a greener (albeit currently more costly) solution then perhaps a biomass boiler is what you need…
You may be able to get some financial support under the Renewable Heat Incentive, although as of writing details for domestic schemes will not be available until next year (2012).
Further information is available from:
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As I’ve mentioned earlier I have plans to start work this year on managing the small amount (I’d guess at around half and acre) of woodland that I have.