It is better to buy wood by volume than by weight because between 35% and 60% of the weight of freshly felled wood comes from water. Poplar is one of the wettest woods when freshly fuelled and ash (at 35%) one of driest. Trying to burn wet wood will produce steam, less heat (as so much of it is being used to dry the wood) problems with the chimney (see below) and pollution.
Seasoning reduces the moisture content of the wood. Wood felled during one winter should be seasoned until the next and preferably a second winter before it is burned. Trees felled during the Spring/Summer will have a very high moisture content compared to those felled in late Autumn/Winter, therefore whilst a log first cut in January may be ready to burn within say, a year, it is necessary for a log cut in May to be seasoned for at least two years.
Whilst seasoning it should preferably be stored under cover in an airy place such as an open sided lean-to. Wood should be burned when the moisture content is below 25% - 'air-dry'. Your can tell if a log is dry because the bark will come away easily in the hand and the log will have splits across the grain. Ideally, logs purchased should be no more than 10cm thick. Any that are will need to be split again to ensure that they burn properly.
In terms of what type of wood to burn it is worth bearing in mind the heavier and therefore denser the wood, the higher its calorific value and therefore the longer it will burn. Hardwoods tend to be denser than softwoods such as pine and spruce and some of the densest are oak and beech. However, some of the very dense hardwoods like oak and elm can be very difficult to burn, so it is usually best to burn them with another type of wood as well. Softwoods tend to be easy to light and to burn quickly (making them very good kindling). Some species like spruce and horse chestnut spit badly making them a hazard in an open fire.
Some of the best woods to burn are ash, beech, hornbeam, hawthorn, crab apple and wild cherry.
