Are biomass boiler costs justified?


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Work started in the warm August of 2009 when we didn’t need heating. Hot water was supplied by an immersion heater as we didn’t have the Solar Thermal panels up at this point (they came in 2010).
The estimated install was meant to be two weeks but it took six in total. We allocated one half of a double garage to the project in an area co-located with the existing gas-boiler for convenience.
Installation was largely trouble-free. The UK representative of the Manufacturer (KWB) came out for commissioning and observed that one section of pipework was incorrect. It was quickly rectified.

We live in a Conservation area and had planning permission refused for an external flue so we had it route through the corner of the bedroom over the garage. Not a big problem as our installer arranged for builders to come in and box in the flue. We redecorated ourselves.

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Are biomass boiler costs justified?

  1. 1. Are Biomass BoilerCosts Justified?
  2. 2. Biomass boiler costs don’t end with installation. Mark Browntakes a frank look at the pros and cons of a biomass boiler for a 5bed detached house.Biomass boiler installationWork started in the warm August of2009 when we didn’t need heating.Hot water was supplied by animmersion heater as we didn’t havethe Solar Thermal panels up at thispoint (they came in 2010).The estimated install was meant to betwo weeks but it took six in total. Weallocated one half of a double garageto the project in an area co-locatedwith the existing gas-boiler forconvenience.
  3. 3. Biomass boiler systemInstallation was largely trouble-free. The UK representativeof the Manufacturer (KWB) came out for commissioningand observed that one section of pipework was incorrect.It was quickly rectified.We live in a Conservation area and had planning permissionrefused for an external flue so we had it route throughthe corner of the bedroom over the garage. Not a bigproblem as our installer arranged for builders to come inand box in the flue. We redecorated ourselves.The KWB Easyfire is a 15kW boiler with a 500l buffer tank. Thesystem provides space and water heating but we also have bothgas backup as well as solar thermal and lounge wood stove.Our system is using wood pellets fed from a hopper. The hopperstores enough for at least seven days in the depth of winter butcan last up to two months in a warm summer. It is fullyautomated, other than filling it up with pellets or emptying theash (once a year!) no work is required. Our KWB is very reliable.
  4. 4. Biomass boiler costsWe installed in 2009 on the assumption thatthe Renewable Heat Incentive would payfor the investment. We could have had acheaper boiler make but had to opt forone licenced for use in a smoke-controlzone. Total cost of the boiler, buffertank, flue, labour & VAT came to £15,590minus £1000 from the (then) Low CarbonBuilding program grant.We use bagged wood pellets and need justunder 5 tonnes a year. They cost about£230/tonne (delivered + VAT) workingout at £1100 pa approx. We take threetonnes per delivery with about twodeliveries a year. Note that there areslightly cheaper options but we preferUK-sourced pellets.
  5. 5. Pros and cons of biomass boilersWe are lucky enough to have a maintenance contract that coversfive years’ work. It works out at about £150 a year this way, butyou could pay up to £500 pa if unwilling to pay up front for acontract. This contract includes cleaning the flue and boiler.Pros•Of all the technologies you install for heating biomass offer the greatestreduction in carbon footprint per £ spent•The KWB we used is able to control the existing Gas boiler and use it asbackup•Biomass boiler installations cause no more disruption than wouldmaintenance on your regular boiler. No need to rip up your floors or gardenas you might for a ground-source heat pump installation.•Biomass boilers use very little electricity•Biomass boilers can use waste wood (turned into pellets)•Biomass boilers can use locally-sourced biomass helping your localeconomy•Biomass boilers are a resilient technology when used with other localmicrogeneration such as photovoltaics•Biomass is very clean – you cannot see nor smell any smoke – ever!•The ash from a biomass boiler takes up hardly any space. When necessarytip it on your garden as fertiliser.
  6. 6. Cons• Biomass boilers are expensive coming in atanything upward of £9000. You could get quotesfor well over £20,000 so shop around. Even ifreplacing oil it is hard to see a payback withoutan additional incentive such as the RHI or acheap on-site source of fuel such as wood chip.• A double garage provides ample storage butmoving and stacking bagged wood pelletsrequires physical effort• It was really hard to find a domestic installer (orwas in 2008/09).• Don’t forget you will need a buffer tank andstorage space for the fuel. We suggest allowingthe sort of space in which a small car would fit.• Biomass boilers are not really suitable for smallhomes on the gas grid. They are more beneficialif you have a very large building (ie, farmhouse, community hall, church, school, etc.) offmains gas.
  7. 7. • Your Biomass boiler deserves to be maintained properly. The UK market isonly very slowly gearing up so you might be limited in choice. Your averageCorgi registered plumber will not touch it.• Our KWB boiler’s controllers are sophisticated to the point of being toocomplicated. Refuelling from bags can be physically demanding. This makesthem unsuitable for social housing, the physically impaired or the elderly.• Fuel delivery can be inconvenient (as for any solid fuel) so we normally takethe day off work or pay extra for Saturday delivery. Delivery to narrow cul desacs are a problem in our experience so we always specify a small 8 tonnetruck – sometimes this message doesn’t get through and we have had topush pallets from the road on a pallet trolley with the help of the deliverydriver. This is almost impossible for a one tonne pallet, we recommend ¾tonne pallets or less. A tail lift truck is recommended. We always end uppart-hand-stacking some of the load to reduce its footprint in the garage.For one fit man this might take 40 minutes to shift 1.5tonnes of baggedpellets (15kg per bag). The other option is to use a large hopper with thepellets blown in – but this is only suitable for much larger installations thanwe have.• Having solar thermal can mean the biomass boiler is hardly used throughpart of the summer. However it will keep the buffer tank up to operatingtemperature which is wasteful (although this can be switched off). Oursystem was sized appropriately based upon our SAP rating so this isn’t asignificant problem.
  8. 8. ConclusionGiven the information we had in 2009 (and the pending Renewable HeatIncentive) we think we made a good choice. However the RHI has notmaterialised and, as far as we know, might NEVER pay us a penny for thisboiler in its final manifestation.When deciding upon this form of heating we did compare it to a ground-sourceheat pump. We didn’t cost up a comparable GSHP but it would only have beensuitable if we had been prepared to dig up the floor for underfloor heatingplus the garden for the ground loop. A GSHP would need a lot of electricity torun but we wanted to generate most of our own power so it would have putthat objective out of reach. Hence biomass was the most local & resilientoption.We have great satisfaction with the boiler and our only regret is the loss of spacein the garage. We would recommend domestic biomass for rural areas withlarge buildings off mains gas.© Mark Brown Aug 2012