What are Wood Chips?
Wood chips are a type of biomass fuel made from logs or larger pieces of waste wood that have been processed through a fuel quality wood chipping machine to produce pieces of a fairly uniform size.
This enables the wood chips themselves to be automatically fed into a biomass boiler from a dedicated fuel store via an agitator with sprung arms and auger-based fuel delivery system.
This offers the greatest convenience and the construction of a large fuel store into which the wood chips can be directly fed in large quantities. This also enables bulk buying in order to keep fuel costs low and minimise the amount of times your fuel store needs to be filled.
How Much Fuel Will I Need?
You are likely to need the following quantities of wood chips for your biomass boiler. The examples have been based on a standard heating profile of 1,314 hours (the heating being on for 15% of the year).
|Typical Fuel Store Size||23m3||40m3||63m3||63m3||90m3|
|Fills Per Annum||4||4||4||5||5|
|Typical Fuel Store Size||8m3||18m3||24m3||32m3||50m3|
|Fills Per Annum||3||3||3||3||3|
A Wide Variety of Fuel Quality
Fuel quality can be paramount in gaining the very best performance from your biomass boiler and can have a huge impact on the life and reliability of your boiler. However, the robustness of the SL series means that these boilers can cope with varying qualities of fuel.
Wood fuel should contain no more than 30% water prior to chipping. In order to dry wood to this level, it may need to be seasoned for up to 2 years for hardwoods and 1 year for softwoods.
Your fuel should also be free from contaminants. The most common causes of service call outs are generally where the fuel contains stones, barbed wire, padlocks and doorknobs, animal carcasses or pieces of excessive length as longer pieces can twist around the fuel delivery system’s auger.
G50 Wood Chips?
The Lindner & Sommerauer range of high efficiency biomass boilers will burn up to G50 wood chips which are roughly 50mm in average chip size. You should buy wood chips from a Woodsure or HETAS approved supplier whose fuel conforms to the ENBS P16A/P16B fuel quality standard. A great source of local suppliers in your area can be found on the National Biofuels Database, which you can see here.
Fuel of this standard will below 30% moisture and be free from the contaminants listed above.
Buy in or Chip Your Own?
There are different benefits to buying fuel from a Quality Assured fuel supplier or from chipping your own. Bought in wood chips are easy and convenient and represent a fuel cost saving of 20-50% versus heating oil. Be sure to check the receipt when you receive your fuel delivery as the Fuel Grade and moisture content should be stated on the paperwork.
If you already have your own supply of logs, you may be able to save up to 80% compared to the cost of heating oil. A contract chipping machine can visit your site and process 15-20 tonnes of wood an hour at a cost of as little as £20 per tonne. Your logs will have to be seasoned so that they contain less than 30% mositure prior to chipping.
Hedgerow Wood - Self Supply
It is also possible to use chipped hedgerow wood in your biomass boiler. On a 15 year coppice rotation without periodic top trimming, a total length of 3km of hedgerow (coppicing around 200m per annum) of hedgerows can heat a typical 4-5 bedroom farmhouse with an energy demand of 30kW. Using hedgerow wood in this way enables a farm house to self supply their own wood fuel indefinitely.
For environmental reasons, it is recommended that only 50% of hedgerows are coppiced to produce woodfuel. Therefore a total of 6km of hedgerow would be required and the average 50 hectare farm in the South West has 10.5km of hedgerow. This is the equivalent of approximately 10 tonnes of wood chips per annum.