The efficiency of a wood burning boiler or stove relies almost entirely on the quality of the fuel. Get this wrong and heat and cost-saving benefits diminish significantly. Standardising wood, particularly when it’s in log form is no mean feat – it is a variable material with size and most importantly, moisture content differing significantly depending on the way it has been treated. When it comes to pellets this is easier, but regardless of the perceived difficulties it is still a very necessary process.
At the moment, consumers may not understand what they are buying – they need to understand in order to get the best out their biomass equipment. By purchasing sub-standard fuel with high moisture content, you are basically paying for water.
This table clearly demonstrates what happens to the kilowatt hour (kWh) as the moisture content goes up – a serious effect which will slash any efficiency claims made by a particular product.
BS EN 14961 is the standard that heating-grade wood fuel should meet. It has been floating around since 2010 but is only now filtering down into best practice. Reputable pellet suppliers should already be following its guidance, but it is harder to monitor one-man-bands delivering logs from the back of their van. Logs can currently be bought under HETAS’ wood assurance scheme.
While a lengthy and pretty boring document, what’s important for consumers is understanding the significant parts of BS EN 14961’s key, which should appear on all fuel packaging. For logs and pellets there’s Length (L) and Diameter (D), pellets also show ash content (A). Woodchip uses a P and then a number, which signifies sawdust content and average sizing. When it comes to logs, the most important symbol to look out for is M, which relates to the moisture content – this should be between 15% and 20% for optimum efficiency.
The only way the standard has any chance of being enforced is if it is consumer driven. If you are in receipt of wood biomass fuel, ask your supplier for proof of compliance. Fuel suppliers should be volunteering this information – it will help to reassure end-users that you know your stuff and are trustworthy.
Next year’s domestic Renewable Heat Incentive (RHI) should see a boom in the take-up of biomass; if this affects your customer base, make sure they are clued-up when it comes to purchasing fuel. Wet wood = an inefficient heating system, negating any of the cost and carbon saving benefits biomass has to offer.