Choosing the right briquette
Different stoves and flue set-ups create different burning characteristics and we have learned it is impossible to guess which briquette is going to suit your stove and your lifestyle.
Compression: The compression used to manufacture a briquette affects how it burns and how much dust and debris might come off as it is handled. Cheap briquettes are almost always made with poor quality machines running at low compression rates. High quality briquettes are made using more complex machinery working to very high compaction rates of over 1,000kg/m3. The result is briquettes of high calorific value that hold their shape and burn long and hot.
Calorific value: We compare calorific value in terms of kilowatt hours per tonne (kWh/tonne) as this enables an easy comparison to be made with other heating fuels such as coal, gas and oil. As rough guide, traditional logs have a calorific value of around 4,100 kWh/tonne (depending on moisture content and tree species) whilst good quality briquettes have a calorific value of between 4,800 and 5,500 kWh/tonne depending on compaction and tree species
(Note: 5,500kWh/tonne is the same as 5.5kWh/kg).
Max. ash content: The amount of ash left behind after burning is what is left in the ash pan for you to dispose of. Less ash results from virgin timber processed after the tree bark has been removed, however some bark can add to the calorific value and lots of bark (pure bark briquettes as high as 4% ash) can help retain heat in your stove for longer periods and even overnight. Bark contains more silica than clean timber and it is the silica that creates ash.
Max. water content: Wood briquettes generally have a water content (moisture content) of under 10%. Most high quality briquettes are dried down to under 6%. Traditional logs by comparison are considered suitable for burning when below 20% and most winter purchased logs are around 30% moisture content, that’s a lot of water to evaporate. Generally, the drier the better as combustion goes to generate heat rather than to drive off moisture prior to the fuel being able to produce any heat for you.
Product Standards: There are European standards to which best quality briquettes are made. This gives you confidence that the manufacturer is producing a briquette that complies with European standards relating to composition, traceability, environmental sustainability and product quality. The standards to look for are: ÖNORM M7135 (Austria) or DIN51731 (Germany). The EU and British Standard equivalents are BS EN 15210-1 2009 and BS EN 15210-2 2010.
Pack size: Most pack weights are around 10kg, but some are 12kg, some 15kg and others 20kg. Clearly this needs to be taken into account when comparing prices between products.