Nitrogen (N) and phosphorus (P) are essential elements for all living organisms. However, in excess, they contribute to such environmental problems as aquatic and terrestrial eutrophication (N, P), acidification (N), global warming (N), groundwater pollution (N), depletion of stratospheric ozone (N), formulation of tropospheric zone (N) and poor urban air quality (N). Globally, human action has multiplied the volume of N and P cycling since the onset of industrialization. The multiplication is a result of intensified agriculture, increased energy consumption and population growth.
Industrial ecology (IE) is a discipline, in which human interaction with the ecosystems is investigated using a system analytical approach. The main idea behind IE is that industrial systems resemble ecosystems, and, like them, industrial systems can then be described using material, energy and information flows and stocks. Industrial systems are dependent on the resources provided by the biosphere, and these two cannot be separated from each other. When studying substance flows, the aims of the research from the viewpoint of IE can be, for instance, to elucidate the ways how the cycles of a certain substance could be more closed and how the flows of a certain substance could be decreased per unit of production (= dematerialization). IE uses analytical research tools such as material and substance flow analysis (MFA, SFA), energy flow analysis (EFA), life cycle assessment (LCA) and material input per service unit (MIPS).
In Finland, N and P are studied widely in different ecosystems and environmental emissions. A holistic picture comparing different societal systems is, however, lacking. In this thesis, flows of N and P were examined in Finland using SFA in the following four subsystems: I) forest industry and use of wood fuels, II) food production and consumption, III) energy, and IV) municipal waste. A detailed analysis at the end of the 1990s was performed. Furthermore, historical development of the N and P flows was investigated in the energy system (III) and the municipal waste system (IV). The main research sources were official statistics, literature, monitoring data, and expert knowledge.
The aim was to identify and quantify the main flows of N and P in Finland in the four subsystems studied. Furthermore, the aim was to elucidate whether the nutrient systems are cyclic or linear, and to identify how these systems could be more efficient in the use and cycling of N and P. A final aim was to discuss how this type of an analysis can be used to support decision-making on environmental problems and solutions.
Of the four subsystems, the food production and consumption system and the energy system created the largest N flows in Finland. For the creation of P flows, the food production and consumption system (Paper II) was clearly the largest, followed by the forest industry and use of wood fuels and the energy system. The contribution of Finland to N and P flows on a global scale is low, but when compared on a per capita basis, we are one of the largest producers of these flows, with relatively high energy and meat consumption being the main reasons.
Analysis revealed the openness of all four systems. The openness is due to the high degree of internationality of the Finnish markets, the large-scale use of synthetic fertilizers and energy resources and the low recycling rate of many waste fractions. Reduction in the use of fuels and synthetic fertilizers, reorganization of the structure of energy production, reduced human intake of nutrients and technological development are crucial in diminishing the N and P flows. To enhance nutrient recycling and replace inorganic fertilizers, recycling of such wastes as wood ash and sludge could be promoted.
SFA is not usually sufficiently detailed to allow specific recommendations for decision-making to be made, but it does yield useful information about the relative magnitude of the flows and may reveal unexpected losses. SFA studies should be supported with other methods such as LCA. Data uncertainties are high in this type of analysis. Use of quantitative uncertainty analysis is therefore recommended. Definition of the system boundaries significantly affects conclusions drawn from SFA results.
Sustainable development is a widely accepted target for all human action. SFA is one method that can help to analyse how effective different efforts are in leading to a more sustainable society. SFA's strength is that it allows a holistic picture of different natural and societal systems to be drawn. Furthermore, when the environmental impact of a certain flow is known, the method can be used to prioritize environmental policy efforts.』
List of abbreviations
1.2. Industrial ecology and industrial metabolism
1.2.1. Closing material material cycles
1.2.2. Diminishing of material flows
1.3. Topics under investigation
1.3.1. Nitrogen (N)
1.3.2. Phosphorus (P)
1.4. Study area - Finland
Forests and forest industry
Energy production and consumption
2. Aims of the study
3. Materials and methods
3.1. Substance flow analysis (SFA)
3.2. System description
I Forest industry and use of wood fuels
II Food production and consumption system
III Energy system
IV Municipal waste system
3.3. Data sources and quantification methods
3.3.1. Situation at the end of the 1990s
3.3.2. Historical data
4.1. Situation at the end of the 1990s
4.1.1. Flows between production and consumption sectors
4.1.2. Flows to water, air and soil (environmental flows)
4.1.3. Recycling and re-use of N and P
4.2. Historical changes in N and P flows
4.2.1. Energy system
4.2.2. Waste and wastewater management system
5.1. Magnitude of the Finnish N and P flows
5.2. Closing the N and P cycles
5.3. Possibilities for diminishing N and P flows
5.4. Importance of system boundaries
5.6. SFA as a decision-making tool