Our Indispensable Guide to Briquettes
Don’t worry – it’s easier than you think! Our guide to wood briquettes will help you become a wood fuel expert in no time.
Wood Briquettes and Heat Logs are interchangeable terms. They both describe a product made from wood by-products. This might be sawdust, wood chip, or wood flour, using extreme pressure to form a block or log shape.
Different briquettes have different burning characteristics, making some more suitable for specific stages in your fire’s life.
Some are great for lighting the fire; others are ideal for a nice hot flame during the day, while some are designed for slow overnight burning.
Every stove is different, depending on air flow, flue set up, and especially weather conditions. One thing we’ve learned is that there’s no such thing as one ‘best’ briquette for everyone. The best option is to try a few and see what suits you. Our Sample Packs and Ready Mixed Pallets are ideal for this.
Generally speaking, a single good quality, compressed heat log is the equivalent of three or four traditional logs.
What makes a good briquette?
Composition: What is the briquette made of?
Fuel briquettes can be made of almost any biomass material, including hardwood, softwood, straw, bracken, paper, coffee, canola, etc.
We choose to stock wood briquettes made from unadulterated hardwood or softwood. Some other biomass products such as straw, bracken, and coffee tend to have a higher ash content and lower calorific value than clean timber.
The right timber is important too. It’s tempting to use old pallets or used timber from building works but there can be hidden extras you don’t want. Waste wood often contains glues, paints and binders, all of which can give off unpleasant and smelly fumes whilst burning.
Because of this, we only stock pure wood briquettes, that we know have no additional nasties in them.
Compression: Is the briquette dusty or crumbly?
Compression refers to the amount of pressure the wood is placed under to make it into a briquette. High compression is better – these briquettes are denser and less dusty.
Poor quality machines running at low compression levels produce cheap and dusty briquettes. We avoid these because they often put people off burning briquettes.
High quality briquettes are made using big, expensive machinery working with very high forces to produce densities of over 1,000kg/m3. The result is briquettes of high calorific value that hold their shape and burn long and hot.
Calorific value: How much heat can it produce?
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 a 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 5,000 kWh/tonne depending on compaction and tree species. (Note: 5,500kWh/tonne is the same as 5.5kWh/kg.)
Ash content: How much ash will it produce after burning?
This is how much ash is left in the ash pan when you clean the fire out. Virgin timber briquettes that have had the bark removed produce much less ash than traditional logs. Some of our briquettes are as low as 0.28% ash. Bracken briquettes, as a comparison, are 4-7% ash.
However, some bark in the mix can add to the calorific value and lots of bark in a briquette can help retain heat in your stove for longer periods and even overnight. Our pure RUF Bark bricks are about 4% ash and can burn up to 12 hours. Bark contains more silica than cleaned timber and it is the silica that creates ash.
Ash from pure wood-burning is a great source of potash for your garden, so it can be safely added to the compost bin. Just make sure it’s completely cold first!
Moisture content: How much water is in the briquette?
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, and a very expensive way to buy water.
Generally, the drier the better. Combustion goes to generate heat rather than to drive off moisture before the fuel can start producing heat for you. However, dry but poorly compacted briquettes burn too fast. Although they’re often cheap, it’s poor value compared to densely compacted but necessarily more expensive briquettes.
Additives: What else is in it?
The answer to this should always be ‘nothing’.
None of our briquettes contain any additives (to assist burning) or binders (to assist compaction). All our briquettes are held together by the natural lignin released from the wood under intense compaction pressure.
Remember: if the wood content is dry enough, you do not need additives to assist burning. And if the heat log is highly compressed, you don’t need to add binders. So, a good quality briquette will not have and will not need any additives.
Product Standards: Are there industry standards I should look for?
The best quality briquettes are made to European Standards. They tell you the manufacturer is complying with European standards for 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.
However, there are many excellent quality briquettes available that are not certified because the certification process is onerous and expensive. Responsible manufacturers will always be able to provide the information we describe above, regardless of their certification.
While weight isn’t a reliable way to buy traditional logs, the consistency of briquettes means that knowing your price per kilo is really helpful.
Most pack weights are around 10kg, but some are 5kg, 12kg, 15kg and others 20kg. Clearly this needs to be taken into account when comparing prices between products. That is why we always give a ‘price per kg’ to assist with comparison.
It may seem obvious, but don’t assume more is better (I frequently have to field the comment “Ah, but there are four in this pack and five in that pack”); four briquettes per 10kg pack or twelve briquettes per 10kg pack; it’s the same energy, it’s just that the four at 2.5kg each should last longer than ten at 1kg each.
Again, although most pallets weigh 1 tonne, some weigh more and some less. Take this into account when comparing prices and look for our ‘price per kg’ info.