The wood kiln operates with 0% reliance on gas, diesel, or grid electricity, directly tackling the high emissions associated with traditional forced-air drying.
It frees up waste wood (which would otherwise be burned for drying) to be sold as additional product.
The recirculation kiln drying method works in harmony with natural thermal processes, providing superior moisture control without the heavy energy consumption of industrial methods.
Many people tend to leave their firewood to season for long periods of time. The moisture content in fire wood dried this way falls rapidly over the first few months, but beyond 6 months not much more is lost. 18-20% moisture content is the best that can be achieved. Often firewood is much wetter than that, but still gets burnt.
To do seasoning properly, a huge storage space is needed leading to long-term stock holding or burning wood before it have been seasoned properly.
This is effective, but hugely energy intensive. Even the very best biomass recirculating kilns use the same amount of energy in the drying process as is returned during the combustion of the firewood. That means every log you put in your home wood burner is matched by another log that has already been burnt to dry it.*
Fuelling these kilns has become unaffordable to anyone who has not already got an RHI scheme in place. Typical powered kilns are very expensive to build and even more expensive to run! Even small ones need loading with fuel every day and often stop working because the boiler has become blocked. If the fuel is not biomass, for instance fossil fuels, then the results of this adverse energy balance are even worse.
Many operators have started with simple stove heating, and then progressed to biomass boilers and then further to automated shredding and chipping hoppers with automated conveyor feeders. These are all huge investments in time and money that come with ongoing maintenance and support costs.
Fire is a considerable risk if a biomass boiler is attached directly to a firewood kiln which leads to difficulty with insurance.
* Wood Chip Drying through the Using of a Mobile Rotary Dryer – Energies 2019, 12, 1590; doi:10.3390/en12091590