Understanding the quality of new raw material sources will be of great importance to ensure the development of a circular bioeconomy. Building up quality understanding of wood waste is an important step in this development. In this paper we probe two main questions, one substantial and one theoretical: What different understandings of wood waste quality exist and what significance do they have for the recycling and re-use of this waste fraction? And, what is the evolution of knowledge and sustainable practices of wood waste qualities a case of? The analysis is based on diverse perspectives and forms of methods and empirical material. Studies of policy documents, regulations, standards, etc. have been reviewed to uncover what kind of measures and concepts that have been important for governing and regulating wood waste handling. Interviews concerning wood and wood waste qualities have been conducted with key informants and people visiting recycling and waste management stations in Oslo and Akershus in Norway. By studying quality conceptions through the social birth, production, life, end-of-life and re-birth of wood products, we analyse socio-cultural conditions for sustainability. Furthermore we show how the evolution of knowledge and sustainable practices of wood waste qualities, in the meeting with standards and regulations, is a case of adaptation work in the evolution of Norwegian bioeconomy.
Lecture – Drying of wood chips with surplus heat from two hydroelectric plants in Norway
We studied drying of wood chips by surplus heat from two hydroelectric plants in the western part of Norway. The wood was chipped and loaded into the dryer; a tractor-trailer and a container were used. The dryers had perforated floors where warm air from the plants was funnelled into the dryer, using an electric fan of 4 kW. Four separate trials were conducted in September and October 2009. The drying capacity of the trailer and the container was roughly 11.5 m3 and 29 m3 loose respectively. The effective height at which drying took place was 1.2 m and 1.9 m. The average temperatures of the air channelled into the dryers was 15–18 °C in the trailer and 24–26 °C in the container. The fan was operated for 139 hours (twice) for the trailer and 121.5 and 67.5 hour periods for the container. The fan used 556 kWh (twice), 486 kWh and 270 kWh of electricity respectively. The chips located at the bottom dried first, and chips located above dried later. The water content in the chip was measured to 66.1 to 52.1% (wet base) before and 9.6 to 6.9% (wet base) after drying. The amount of water removed from the container was approximately 28 kg per hour and 22 kg per hour from the trailer. For the container, drying cost roughly 9 Euro per MWh; the cost of the trailer was nearly twice as much. This indicates that the drying volume should be as high as possible. Drying determines net calorific value and hence market value of wood chip.