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52 MATERIALS MAY/JUN 2024 FDM ASIA | www.fdmasia.com

99.films 90 thousand cubic metres per year spread across five production
facilities in Estonia, Finland, and Belarus.
TM in nitrogen has not grown much in terms of market
share, and data on current production volumes are unavailable.

Overall, the commercial amount of modified wood is still
dwarfed by that of preservative-treated wood (about 21 million
cubic metres in the US alone each year and 6.5 million cubic
metres in Europe).
Numerous wood-based TM processes have entered the
European market, mostly varying in terms of pressure conditions
and oxygen exclusion.

Thermal Modification Technologies

There are two types of TM technologies: open-system and
closed-system technologies. The majority of open systems
are upgraded classic drying ovens.
A pyrolysis technique at high temperature and normal
atmospheric pressure is used to perform TM on wood. The
world’s largest TM wood factories, including the International
ThermoWood Association, treat wood in a water steam

environment at atmospheric pressure.
Closed systems hydrolyse wood materials at high pressure
but at a lower temperature, so the pressure serves as a
temperature substitute.
According to statistics collected, thermal modification (TM) The fundamental advantage of TM in steam at higher
processes dominate the global commercial production of pressure over atmospheric pressure treatment is lower maximum
treated wood, producing 1.11 million cubic metres per year. treatment temperatures and, as a result, cheaper energy costs.
Acetylation accounts for 120 thousand cubic metres per year Another advantage is that the entire TM time from heating,
of commercialised processes, while furfurylation accounts for incineration, and cooling to room temperature is reduced. The

45 thousand cubic metres per year. total processing time in a closed-system process is 22–30
Another 330 thousand cubic metres per year of global hours until the material has completely cooled. ThermoWood
production is predicted for various methods, primarily based requires up to 70 hours to complete the process.
on resin-based systems (e.g., Impreg-and Compreg-based The Rétification process is distinguished from other
processes). Oy Lunawood (Thermowood process) is the largest thermal modification procedures by the use of nitrogen as
TM manufacturer, with an annual manufacturing capacity of the modification medium. In specific equipment, pre-dried
155 thousand cubic metres. (Wrel = 12%) wood is slowly heated to 210–240 deg C in

The Estonian company Thermory AS (Wood treatment a nitrogen environment with an oxygen content below two
technology process) also has a high capacity of approximately percent. The maximum pressure in the system during the TM