Carbon Dynamics in Wood Products

The carbon (C) reservoir of wood products in Finnish construction and civil engineering was estimated by three inventories including the years 1980, 1990 and 1995. The inventory method is mainly based on the statistics of Finnish building stock. The use of different construction materials in different parts of buildings is estimated for each building type. Information collected through building permits includes the materials of bearing frames and facades. More information about the use of wood products in construction is gathered by many enquiries. The mix of construction materials has changed during each decade. Furthermore, the timber stocks in construction not subject to permission and in civil engineering (e.g. bridges) were estimated. The C reservoir is calculated on the basis of dry matter content of wooden construction materials. The time parameters of a simple exponential decay model and a more detailed C balance model of wood products were calibrated to the inventory results using the estimated wood flows to construction as model inputs. According to the inventories the C pool in sawn wood and wood-based panels of the Finnish building stock was 8.7 Tg C in 1980, 10.7 Tg C in 1990 and 11.5 Tg C in 1995. The mean annual increases, 0.20 Tg C from 1980 to 1990 and 0.15 Tg C from 1990 to 1995, are approximately 1.3% and 0.8% of the fossil fuel C emissions in Finland during the same periods. When also taking into account construction not subject to permission and civil engineering works, the estimated C stock of wood products in Finland was 16.5 Tg C in 1995, which is about 3.3 Mg C per capita and approximately 2.4% of the C reservoir in Finnish forest biomass. The total C reservoir of wood products (excluding wood waste and paper products) coming from Finnish forests might be as much as 7% of the standing biomass if exported wood products are also included. The average lifetime of sawn wood in Finnish construction is less than 40 years.