Climate-adapted wet storage of saw timber and pulpwood: an alternative method of sprinkling and its effect on freshness of roundwood and environment

The present thesis describes and discusses the development and the evaluation of an alternative method for wet storage of saw timber and pulpwood. As a fundament for climate-adapted wet storage, the water balance, waste-water dynamics and possibilities to reduce sprinkling intensity in a controlled way were studied. Thereafter, a general evaporation formula in accordance with Penman Monteith was modified and used as control function when sprinkling roundwood piles of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst). The Penman Monteith formula was tested both in theory and in practise by comparing the relationship between potential and measured evaporation at two independent sites, and by following the moisture content in the outer sapwood of sample logs. The environmental impact of climate-adapted wet storage was examined by monitoring the quality of inlet and waste-water during a wet storage season. Sprinkling of roundwood can be adjusted to the prevailing climate conditions, i.e., the evaporation from roundwood piles at the wood yard. The correlation between potential and measured evaporation from the roundwood pile was significant regardless of the geographical site. The sprinkling intensity was significantly reduced as a result of climate-adaptation. The moisture content development of roundwood during wet storage was to a great extent dependent on the wood-handling prior to sprinkling. The moisture content could be retained at an acceptable level, i.e., in excess of 100 per cent at dry-base, when fresh roundwood was put into climate-adapted wet storage. The moisture content of once dried roundwood could not be recovered. The environmental impact of climate-adapted wet storage was clearly lower than when using conventional sprinkling with fixed sprinkling intensity especially during the first two weeks of wet storage. The residence time of waste-water was longer, resulting in a lower environmental discharge due to an improved microbial degradation. The establishment of microbial ability and the environmental loads were affected by the quality of the sprinkling water.