Seasoned, Unseasoned, or Kiln-Dried: Choosing the Greenest Type of Firewood

Winter has finally arrived in Edinburgh. And while most people use gas or electric heat to warm their homes these days, there are still many who use firewood to warm their homes.

There has been much talk about wood heat recently. Many believe it to be an environmentally-irresponsible way of heating, while others think it’s clean and natural. What’s most frustrating about this debate is that both viewpoints are correct. This is because, as we will discuss further on, firewood is the Dr Jekyll and Mr Hyde of winter heating.

In this article, we’ll take a look at the most important choice you make each heating season: whether to buy preseasoned logs, season your own firewood, or purchase professionally kiln-dried logs.

Isn’t All Firewood the Same?

As is explained in Lekto’s expert-written ultimate guide to firewood, the most important determiner of firewood quality is its moisture content.

When wet (or improperly seasoned) firewood is burned, it smokes heavily and releases large amounts of creosote (a cancerogenic, tar-like substance) and a slew of other pollutants that are harmful to both human health and the environment. But get rid of that moisture and firewood becomes an incredibly clean and efficient source of heat that releases virtually no pollutants. The difference is truly night and day.

Recognizing the importance of firewood dryness, Defra introduced the Ready to Burn firewood quality standard. This regulation mandates that all pre-dried firewood sold in the UK starting 1 May 2022 must contain no more than 20% moisture. And while this is good, it still doesn’t mean that you can buy any kind of firewood out there and expect to get the same quality.

Types of Firewood

There are three main types of logs you can buy in the UK today: seasoned (air-dried), unseasoned (wet), and kiln-dried (baked in an industrial oven).

Seasoned Firewood

This is the type of firewood most people are familiar with. Seasoned firewood is created by leaving firewood outside to dry for a period between 12 and 36 months (depending on the wood species and local climate).

Up until recently, whether your seasoned firewood would burn well or not depended largely on the luck of the draw. Unscrupulous suppliers would often sell their firewood before it had enough time to dry properly, which resulted in firewood that burned inefficiently and produced a lot of smoke.

After Defra stepped in to mandate that all pre-dried firewood must contain no more than 20% moisture, seasoned logs became much easier to recommend. Which makes them a good value option for cost-conscious consumers.

Unseasoned Firewood

Wet or unseasoned firewood consists of freshly-split logs that you’re expected to dry yourself. 

While it is far cheaper to buy than the other options, proper seasoning can take a couple of years and you may be tempted to use firewood before it is properly seasoned. And, as we discussed earlier, this is a hazard to your health, the health of your appliance, and the health of the environment.

So, unless you’ve been seasoning your own logs for many years and understand how to dry them properly, we do not recommend that you buy unseasoned logs.

As of late 2021, the only legal way to buy unseasoned firewood is to purchase it in bulk (in quantities over 2 cubic metres). If you do decide to make such a purchase, make sure the supplier provides clear, in-depth instructions on how to season the logs properly. They are required to do so by law.

Kiln-Dried Firewood

Kiln-dried firewood can be thought of as the Rolls-Royce of firewood. It is by far the most expensive option you can find, but it burns cleaner and hotter than any other type of firewood out there. 

Kiln-dried firewood is created by putting unseasoned logs into an industrial oven equipped with a powerful fan and baking it for several days. While this process is expensive and energy-intensive, it can produce firewood that contains as little as 10% moisture (which is far lower than the 20% required by the Ready to Burn standard). 

This makes it the most eco-friendly type of firewood out there.

The only real drawback to kiln-dried logs is the price premium you have to pay. This being said, heating your home with premium kiln-dried firewood is still less expensive than doing it with gas or electric heat, all the while being incredibly eco-friendly.

•