『Abstract
　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.』

Contents
List of abbreviations
1. Introduction
　1.1. Background
　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
　　　Agriculture
　　　Forests and forest industry
　　　Fertilizer production
　　　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. Results
　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. Discussion
　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
　5.5. Uncertainties
　5.6. SFA as a decision-making tool
6. Conclusions
Acknowledgements
References

表４　研究した４つのサブシステム〔（I）林業と木材燃料の使用、（II）食産業と消費、（III）エネルギー、（IV）都市廃棄物〕における1990年代の終わりの窒素（N）とリン（P）の１０大フロー

	フロー		トンN／年	フロー		トンP／年
1	HII	肥料（農業）	180000	HII	肥料（農業）	29500
2	DII	作物産出高	147000	DII	作物産出高	21900
3	EII	飼料	116000	EII	飼料	16200
4	AIII	国産燃料	99000	FII	肥やし	15900
5	DIII	燃焼からの酸化窒素	75000	II	木材とパルプの化学製品（パルプと紙産業）の使用	6300
6	EIII	燃焼からの元素窒素	74000	FIII	燃料灰	6300
7	YII	肥やしと肥料と脱窒からの大気への排出	72000	JIII	産業および輸入飼料	6200
8	BIII	輸入燃料	68000	AIII	国産燃料	5700
9	FII	肥やし	67000	III	産業使用のための動物製品	5700
10	NII	国内食物消費	33000	NII	国内食物消費	5500

表５　４つのサブシステム〔（I）林業と木材燃料の使用、（II）食産業と消費、（III）エネルギー、（IV）都市廃棄物〕における1990年代の終わりの窒素（N）とリン（P）の５大環境フロー

	フロー		トンN／年	フロー		トンP／年
1	DIII	燃焼からの大気への酸化窒素	75000	TI	森林産業廃物の埋立物	3500
2	YII	肥やしと肥料と脱窒からの大気への排出	72000	ADII	農地からの浸出	2400
3	ADII	農地からの浸出	33000	HIII	燃料灰の埋立 〔一部（木材燃料）はTIフローと重複〕	2400
4	TIV、 VIV	水への都市廃水放出	14000	MIV	都市下水汚泥の埋立物	900
5	LIV	都市固体廃物の埋立物	7000	LIV	都市固体廃物の埋立物	800