Nitrogen flow in Scania : substance flow analysis on a regional level

Abstract: In this thesis, the flows of reactive nitrogen (Nr) in Scania were investigated and quantified. The thesis was also intended to form a basis for comparison between the urban nitrogen flow and other flows of nitrogen within Scania. The management of nitrogen in society has disturbed the natural nitrogen cycle. This is linked to a series of environmental problems such as eutrophication, acidification, global warming and smog. The method used was Substance Flow Analysis (SFA) for Nr. For calculation and flow charts Scania was divided into three subsystems; air, water and society. The society was divided into five sectors; agriculture/forestry/fishery, food industry/industry, household/retail/service, technical systems and transport. After that flows within the subsystems was identified, which could then be quantified by data collection and calculations. The results showed that emissions to air mainly come from agriculture, transport and combustion. Agriculture contains the largest Nr flows, consisting of mineral fertilizer, deposition and nitrogen fixation. In agriculture, animal production creates an internal flow in the form of manure and feed from agricultural land. Scania has a large food production, where animal products, slaughtered animals, imported material and crops act as raw materials. A large proportion of the produced food is exported; resulting in a large outflow of Nr. Transport gives rise to a big part of the air emissions within Scania. A surplus of Nr in soil and water give rise to leakages to the surrounding seas. The relatively large urban nitrogen flow in Scania contributes to water discharges downstream, energy consumption at WWTPs and Nr pollution up-stream. Only a small amount of the urban nitrogen flow is reused on agricultural land. There is a potential of increasing the reuse by installing urine-separating toilets. Another way of improving Nr management could be to eat less protein, i.e. give less Nr load into WWTP. The conclusions are that Scania leaks Nr to air, water and soil. The nitrogen management generally needs to be improved to become sustainable and there is a great potential for improvements of the urban nitrogen flow by either changing the wastewater systems and/or changing the diets of the people living in Scania.