The Air Quality (Domestic Solid Fuels Standards) (England) Regulations coming into force soon stop small quantities of firewood from being supplied where the moisture content is above 20%. For details see: https://woodsure.co.uk/new-regulations-confirmed/   Moisture content of a piece of wood is defined in two ways:   Wet basis which is a measure of the water in a log, expressed as the weight of water as a percentage of the wet/unseasoned log. (i.e. wood and water)   Dry basis