A log's a log isn't it? Well, not if you want it to burn well it isn't. As with all woodfuel, the efficiency with which it burns depends greatly on its moisture content. For logs to burn efficiently in a boiler the moisture should be at or below 25%. That’s not all. They should also be seasoned, and cut to the right size.

So how do you know whether your supplier is offering you logs of a high or low standard when there is no kite mark that you can measure things against? The answer is to plan your supply chain, and become an informed customer according to Stephen Green, biomass project manager at RegenSW.

He suggests that by now you should have next winter’s seasoned log supply already in storage. He also advises you get a wood moisture meter, so that you can check the moisture level both in the wood you buy and that which you’re storing (prices start at around £10 on ebay).

The lack of standards in the log market, which has boomed recently thanks to the rise in energy prices, is because it is dominated by the grey market. Firewood is often sold by the load or half load, which makes it almost impossible to compare prices between suppliers. Ask your supplier for a more specific indicator of volume. It’s also helpful to know what size the logs are cut to and whether they’ve been split, so you know how suitable they are for your appliance. Large and small are a bit too vague.

Moisture content will be affected by whether or not the logs have been seasoned, and if so, for how long. Whether they’ve been stored under cover and how long they since they were split will also have and impact. Freshly cut, green material will have a moisture content of 55%, compared with 20-25% for two-year seasoned wood that has been split.

Buying appropriate pellets and wood chips is not so complicated. Although there isn’t a UK standard in operation, most of the industry has adopted the Austrian Onorm standards. Boilers and stoves will specify which standard of fuel is needed for it to operate effectively.

Moisture content is just as important for the performance of both fuels, so it's worth putting a wood moisture meter on your Christmas present list for them too.

Photo by iangbl

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