Jul 8, 2019

"Fresh" wood with a humidity level of approximately 30% must be dried to achieve a humidity level of less than 20%.

There are several methods for drying wood: the natural method in the open air and safe from bad weather or the artificial method. Wood dryers can use several technologies: heat pump, hot air conditioning or vacuum.

Natural drying

Natural air drying implies immobilization of the stock for a relatively long period of 6 to 32 weeks depending on the species, the thickness of the flows and the season. This method tends to limit responsiveness to variations in client requests.

Wood artificial drying

Artificial drying allows better humidity levels and facilitates inventory management and reactivity. Various artificial drying processes are available on the market: pres-drying, low temperature, heat pump, air conditioning or vacuum. They each have their own field of use: they will be more suitable for hardwoods or softwood, for larger or smaller production volumes and they will use different power sources. Note that the wood industries produce a significant amount of "related biomass" which can be used with certain drying processes, and from an environmental point of view are more favourable than other energy sources. The use of these products, whose carbon cycle is zero, replaces fossil fuels that have a greater impact in terms of greenhouse gas emissions.

Wood artificial drying Return on Invest (ROI)

Wood artificial drying is an important investment. The technology and equipment must be mastered to guarantee the quality of the products and, above all, to limit the associated energy consumption.

Indeed, drying under profitable economic conditions requires calculating the cost price of drying with great precision. In the cost of wood drying, regardless of the drying process, three main items appear: Energy + Depreciation + Operation, of which relative importance, depending on the process, the volumes and energies used are as follows: Energy: 40 to 60% – Depreciation: 15 to 40% – Operation: 20 to 25%

Energy is therefore one of the first cost areas of artificial drying, on which all efforts should be concentrated, bearing in mind that thermal energy represents, on average, 60 to 90 % of the total energy associated with drying.