Environmental Management Strategies
Series
Series: Environmental Management Strategies Call for Papers This new ESPR feature addresses "old" and "new" methods and approaches in chemicals management. It is designed to inform about international developments and foster an exchange of ideas.
5. Regional, national, international, global access to management strategies for chemicals, e.g. WTO, WHO, OECD, UNEP, IRPTC, IFCS, etc. Please submit contributions (preferably via fax transmission) to one of the column editors:
We would like to encourage you to contribute papers, statements and news from your region and organization. The following topics are important: 1. Traditional chemicals management approaches: Toxic substances, existing chemicals, special compounds, legal limits and threshold values 2. Strategies for sustainable development 3. Management of the flow of substances, materials and energy 4. Development and application of new methods and concepts, e.g. life cycle assessment, environmental auditing and certification according to ISO 9000 ff, etc.
Length: 2-5 typewritten pages Dr. Martin Held Evangelische Akademie Tutzing P.O. Box D-82324 Tutzing, Germany Phone: +49-8158-251-116 Fax: +49-8158-251-133
Prof. Dr. Walter K16pffer C.A.U. - WG Assessment of Chemicals, Products and Systems Daimlerstraf~e 23 D-63303 Dreieich, Germany Phone: +49-6103-983-28 Fax: +49-6103-983-10
Understanding Regional Metabolism for a Sustainable Development of Urban Systems': Peter B a c c i n i
Dept. of Civil and Environmental Engineering, Swiss Federal Institute of Technology Zurich, ETH H6nggerberg, CH-8093 Zurich, Switzerland 1
Introduction
Abstract cities are the most complex forms of settlements which man has built in the course of his cultural development. Their "metabolism" is connected with the world economy and is run mainly by fossil energy carriers. Up to now there are no validated models for the evaluation of a sustainable development of urban regions. The guidelines for a "sustainable development" suggest the reduction of resource consumption. The article is concerned with the problem of how the "sustainable-development concept" can be transformed from a global to a regional scale. In urban settlements the strategy of final storage should be applied. By this, the subsystem waste management can be transformed within 10 to 15 years to a "sustainable status". With regard to the system "agronomy", the article concludes that agriculture in urban systems should focus on food production instead of promoting reduction of food production in favour of energy plants, which is not a suitable strategy. The main problems are the energy carriers. Transformation to a %ustainble status" is only possible by a reconstruction of the urban system, i.e. of buildings and the transportation network. The rate determining step in achieving such a status is the change in the fabric of buildings and in the type of transportation networks. The reconstruction of an urban system needs, mainly for economical reasons, a time period of two generations. Key words: Sustainable development; regional material management; metabolism; material flows; urban systems; waste management; energy; carbon fluxes; anthroposphere; agronomy; forestry
Cities are the most complex forms of settlements which m a n has built in the course of his cultural development. The u r b a n architecture reflects the socio-political character of a city and the cultural, economic a n d technological status of its inhabitants. Their m e t a b o l i s m is connected with the world economy and is r u n mainly by fossil energy carriers. Up to n o w there are no validated models for the evaluation of a sustainable development of u r b a n regions. The guidelines for a " s u s t a i n a b l e d e v e l o p m e n t " (IUCN 1980 and W C E D 1987) suggest the reduction of resource consumption per capita to secure the needs of future generations with a global p o p u l a t i o n of a b o u t 8 - 10 billions. Looking at the present distribution of a n n u a l energy c o n s u m p t i o n on a global scale, the industrial countries with their u r b a n settlements are responsible for 7 0 - 8 0 % of the total. For u r b a n systems of the developed world, the following question arises: H o w can they transform the "sustainabledevelopment concept" from a global to a regional scale? Some answers to this question are based on metabolic studies of densely p o p u l a t e d regions in developed countries (BACCINI and BRUNNER 1991; BACCINI a n d BADER 1996)
* For the definitionof the term "metabolism"see BACaNIand BADER1996.
108
ESPR - Environ. Sci. & Pollut. Res. 3 (2) 108-111 (1996) 9 ecomed publishers, D-86899 Landsberg, Germany
Series 2
The Transformation of Rural to Urban Systems
Until the beginning of the 19th century, cities were the regional centre of an agrarian culture. With progressing industrialisation and democracy, the once distinct boundaries between rural and urban settlements began to break up. At the end of the 20th century the urban population, which already makes up more than half of the global population shows exponential growth. In the Swiss Lowlands - located between Lfiman and Lake Constance -, a region of about 200 km 2 with 100'000 inhabitants serves as a case study (OSWALDand BACCINI 1996). A first assessment of the material fluxes through the anthroposphere (the sphere in which human activities such as "to nourish", "to reside", "to transport", etc. take place) reveals that about 25 tonnes of goods per capita were used to fulfil the needs of the various activities of rural man around 1800. The main fluxes consist of water, followed by air and construction materials (--) Fig. 1). It is a solar system, driven by regionally gained biomass. At the end of this century, modern urban man needs about 100 tonnes per capita and year. This system is driven mainly by fossil fuels. Since the population has increased by a factor of 7, the anthropogenic fluxes in the region have increased by a factor of 30 (mass per km 2 and year).
Fig. 1: The metabolismof rural man (1800) and urban man (1995) The stock in construction work (the mass of buildings and transport networks) has increased by a factor of 4, from 80 to 300 tonnes per capita. This per capita increase is mainly due to the development from 1950 to 1990, when the per capita stock grew exponentially. This process is not finished yet because the metabolism, especially with regard to the goods "solids/fuels", has not yet reached a steady state.
3
The Concept of Sustainable Development and its Application on a Regional Level
Three case studies illustrate methods of transforming the concept of "sustainable development" for a regional level.
3.1 Waste management In the waste management of urban settlements the "weakest part" of the system is the process "deposition of solid residues". During the last decades, environmental protection measures have set their priorities in the cleaning of waste waters and off gases. For the deposition of solid residues, three main strategies are known (BAccINI 1989): ESPR- Environ. Sci. & Pollut. Res. 3 (2) 1996
Environmental Management Strategies 1. The containment strategy, in which a dense envelope is constructed to prevent interactions of wastes with the environment. The alternatives are specific geological formations in the lithosphere. Since the content is not changed in its physical and chemical properties during storage, the hazardous potential remains. Future generations have to control the functioning of the envelope. Up to now this strategy was restricted to specific fractions of hazardous wastes. 2. The controlled reactor strategy, in which a biochemical process is run with wastes reacting with water, air and, in the presence of organic materials, with micro-organisms. From field experiments and geochemical modelling it is known that such reactors run for several hundred years until emissions are reached which are compatible with the environment (BELEVI and BACCINI 1989). As with strategy 1, future generations have to handle the wastes of their ancestors. At present this strategy dominates in the developed countries. 3. The final storage strategy, in which all solid wastes which cannot be reused are treated to yield only earth crusts such as stones, ores and soils (BACCINI et al. 1991). Each generation transforms its waste completely, technically and economically. This is one consequent application of the sustainability concept. For such a strategy, thermal treatment processes are indispensable. Only few regions can follow such a strategy. Switzerland started with this third strategy in 1986. The intermediate results (1995) are as follows: - Due to more sophisticated thermal treatment plants the costs for mixed solid wastes have more than doubled and are now in the range of 300-400 USD per tonne. The mixed solid waste fluxes were reduced by 30 % (average value), from 360-400 to 240 to 360 kg/capita & year and are still in the process of reduction. - Separate collection has strongly increased. The main resource fluxes from private households (biomass, plastics, metals, glass, paper) follow this path into recycling (BACCINI et a1.1993). - Industry and trade have installed new equipment and technical processes to reuse goods from separate collection. - The federal government decided to cease reactor land filling definitely by the year 2000. The average costs per capita and year amount to 100-200 USD, which corresponds to about 0.4 per cent of the average net income per capita and year. The material fractions to be deposited are summarised in Table 1. The input is an order of magnitude higher than the output. "Land filling" is not a quantitative but a qualitative problem. Most actual residues from thermal treatments do not have a "final storage quality" yet. However, this is a minor problem and can be solved with reasonable economic efforts. Waste management as a subsystem in the regional material management of densely populated and developed regions can be transformed within 10 to 15 years to a "sustainable status".
109
Environmental Management Strategies Table 1:
Balanceof solid material fluxesfor a Swiss Lowland Region
Type of material
Flux in kg per capita and year
Input: Construction materials (mainly gravel, sand and stones, from regional sources) Output: Bottom ashes Residues from gas cleaning Construction wastes (inorganic)
7000-9000
100-150 10- 15 200-700
300-900
Total
3.2
Series
Agronomy and forestry
In the Swiss Lowlands, the agricultural land covers about 55 % and the forests about 33 % of the total area. The urban system of about 12 % is like a network embracing the patches of biomass production. Agronomy and forestry use less than 5 % of the total labour activity and produce less than 5 % of the GNP. The two economic branches are subsidised by about 1000 USD per capita and year to keep their living standard. Due to economical reasons, forests can not be fully harvested (yield about 75 %). In some agricultural branches (crops, milk) there is overproduction. The emissions from agriculture to air and water (mainly nitrogen and phosphorous) reduce their quality significantly. Agricultural soils are ecologically endangered. The carbon metabolism ( ~ Fig. 2,) is a good example to analyse the main characteristics of biomass management. For the system chosen, the fluxes and carbon concentrations of each commodity are taken from various studies already published (MOLLER et al. 1995). The corresponding carbon fluxes and the error propagation are calculated with SIMBOX (BACCINI and BADER 1996). In Fig. 2 the five processes within the anthroposphere (food processing, industry and trade, energy transformation, consumption in settlements, waste management) are combined as one single process "operation of settlement areas". This process is responsible for the predominant carbon flux. The input results mainly (90 %) from imported fossil fuels. Approximately 60 % of the demand for food is covered by the regional agriculture. The rest has to be imported. The carbon turnover of the process "Agriculture" is 3 to 4 units higher than the one of "Forestry". Their combined net contribution to the target process "operation of the settlement area" is only about 10 % of the total. The largest stocks are found in the soils of the latter two processes. However, the concentration of the organic carbon in soils is relatively low (a few per cent). The most concentrated forms are in the forest trees and in the wooden parts of buildings. Both are in the same order of magnitude (103 kg/capita). Present urban systems of this type thus depend mainly on external organic carbon sources to run their metabolism.
Fig. 2:
Carbonfluxes in a Swiss Lowland region (Fluxes in kg per capita and year; stocks in kg per capita)
duces affluent food (from a national point of view). Food production should be reduced in favour of specific energy plants such as miscanthus sinensis, grass or wood. Table 2 shows the resulting energy fluxes and the reduction of CO 2. The effects are marginal. A closer look at the energy content of organic wastes from agriculture and forestry leads to the conclusion that only about one third of its total potential is used. This potential is definitely higher (at least by a factor of three) than the proposed scenario with energy plants (MOLLERet al 1995). With regard to the concept of a sustainable development, a reduction of food production in favour of energy plants is not a suitable strategy. Different studies show (e.g. BUITENKAMP et al. 1992) that on a global scale mankind will encounter food shortage within one to two generations (30 to 60 years). Assuming the present per capita consumption of wood continues, the forests could meet the demands of the next generations. In conclusion, one can postulate that agriculture in urban systems should focus on food production.
Table 2:
Contribution of Agriculture (A) and Forestry (F) with energy plants (as net energy in Gigajouleper capita and year). Use of 5 % of the total agricultural land (after MOLTERet al. 1995) i
Energy (GJ/cap y) CO2-Reduction (%)
Crop Miscanthus sinensis
1.6
1.8
Grass
0.5
0.6
3.2.1 The potential of agriculture and forestry in the regional carbon household
Wood
0.6
0.7
Bio-Waste of the total A&F
5-7 a
2-3
One specific measure in carbon management is the promotion of energy plants in an agricultural practice that pro-
a actual use: 1.5 GJ/cap y
1 10
ESPR - Environ. Sci. & Pollut. Res. 3 (2) 1996
Series 3.3
Buildings and transportation networks
The metabolism of the urban settlement area needs the following mass goods (see also Fig. 1): Water, biomass, construction materials and energy carriers. As a first working hypothesis, the following two criteria are chosen to examine the potential for a sustainable development of the region: 1. The metabolism of an urban system is "sustainable", if the demand for essential "mass goods" such as water, biomass, construction materials (e.g. stones) and energy carriers can be satisfied autochthonously by > 80 % in the long term. The degree of self-sufficiency, arbitrarily chosen with respect to a set of essential goods, determines the ecologically defined border of the urban system. 2. The rest can be covered from the "external market" in such a way that the global resource capitals are not reduced significantly. The mean fluxes of available goods per capita from the external market are determined by the annual growth rate of the "global Hinterland", divided by the world population. A first analysis of a Swiss Lowland region leads to the following results (OSWALDand BACCINI 1996): Water: The region is self-sufficient with respect to the quantity needed (ground water). However, the quality is constantly decreasing, mostly due to agricultural emissions, i.e. the water household is not sustainable. Biomass: The activity "to nourish" can be supported autochthonously by 60 %. With a low meat diet (10 kg meat instead of 80 per capita and year), the region could become "sustainable" if the emissions to air and water are reduced simultaneously. The forestry could theoretically cover the regional demand for wooden products (timber, pulp), but is presently not economically competitive. Construction materials: The region is self-sufficient with respect to gravel and sand, but will exhaust the stocks within the next 30 years, assuming the same rate of exploitation. Theoretically, there are alternatives in the lithosphere. However, their exploitation will need more energy. Energy carriers: More than 90 % of the energy result from external resources. About 80 % of the energy flow into "building maintenance" and transportation. It follows that a transformation to a "sustainable status" is only possible by a reconstruction of the urban system, i.e. buildings and the transportation network. The mass good energy and the existing "architecture" are the key factors. The rate determining step in achieving such a status is the change in the fabric of buildings and in the type of transportation networks. The capital invested in the "construction" (---~Fig. 1) amounts to 300'000 USD per capita. The annual expenditures for their metabolism amount to 10'000 USD per capita, that is in the same order of magnitude as the average annual net income. The reconstruction of an urban system needs, due to economic reasons, a time period of two generations or about 60 years {assuming an annual change of I - 2 % of the stock). The per capita net energy demand, at present 120 GJ/cap & y, should be reduced by a factor of three (to 40 units), ESPR - Environ. Sci. & Potlut. Res. 3 (2) 1996
Environmental Management Strategies corresponding to 2 kW per capita (primary energy). This is in agreement with a global threshold consumption proposed by the World Energy Conference. There are distinct measures to achieve these goals, for example: - reduce heating of buildings from 600 MJ/m 2 9y (100 m2/capita) to 200 MJ/m 2. y (or 20 GJ/cap. y). - reduce transportation energy for persons and goods from 30 GJ/cap 9y to 10 GJ/cap 9y. Theoretically, there is enough building surface available (300 m2/cap) in the settlement area to realise this concept technically. With 5 % efficiency from 200 W/m 2, about 70 m2/cap are needed to produce 20 GJ/cap 9 y. Such a scenario for 2050, shown in comparison with the present energy supply in Fig.3, is technically achievable but economically not yet favourable (approximately fivefold energy prices), due to the fact that fossil energy is still available at low prices.
Fig. 3:
4
Comparison of energy supply sources at present (1990+, light bars) with a solar scenario (for 2050+, hatched bars) in a Swiss Lowland Region
References
BACCINI,P. (Ed.) (1989): The Landfill: Reactor and Final Storage. Lecture Notes in Earth Sciences Vol.20, Springer, Berlin Heidelberg New York BACClNI,P.; BRUNNER,P.H. (1991): Metabolism of the Anthroposphere. Springer, Heidelberg New York BACCINI,P.; BELEVI,H.; Lichtensteiger, Th. (1992): Die Deponie in einer 6kologisch orientierten Volkswirtschaft. GAIA 1, 34-49 BACCINI,P.; DAXBECK,H.; GLENCK,E.; HENSELER,G. (1993): METAPOLIS, Giiterumsatz und Stoffwechselprozesse in den Privathaushalten einer Stadt. Nationales Forschungsprogramm NFP 25 "Stadt und Verkehr", Ztirich BACCINI,P.; BADER,H.P. (1996): Regionaler Stoffhaushalt (Regional Material Management). Spektrum Akademischer Verlag, Heidelberg BELEW,H.; BACC~NI,P. (1989): Long-Term Behaviour of Municipal Solid Waste Landfills. Waste Management and Research 7, 43-56 BUITENKAMP,M.; VENNER,H.; WAMS,T. (Eds.) (1992): Action Plan Sustainable Netherlands. Friends of the Earth Netherlands, P.O. Box 19 199, Amsterdam IUCN 1980: World Conservation Strategy, Gland MI]LLER, D.; OEHLER,D.; BACCIN1,P. ,(1995): Regionale Bewirtschaftung yon Biomasse (Regional Management of Biomass). vdf, Hochschulverlag AG an der ETH Ziirich OSWALD,E; BACCINI,P. (1996): Synoikos, an intermediate report, ETH Zurich WCED 1987: Our Common Future. New York, Oxford University Press
111
Series
Series: Environmental Management Strategies Call for Papers This new ESPR feature addresses "old" and "new" methods and approaches in chemicals management. It is designed to inform about international developments and foster an exchange of ideas.
5. Regional, national, international, global access to management strategies for chemicals, e.g. WTO, WHO, OECD, UNEP, IRPTC, IFCS, etc. Please submit contributions (preferably via fax transmission) to one of the column editors:
We would like to encourage you to contribute papers, statements and news from your region and organization. The following topics are important: 1. Traditional chemicals management approaches: Toxic substances, existing chemicals, special compounds, legal limits and threshold values 2. Strategies for sustainable development 3. Management of the flow of substances, materials and energy 4. Development and application of new methods and concepts, e.g. life cycle assessment, environmental auditing and certification according to ISO 9000 ff, etc.
Length: 2-5 typewritten pages Dr. Martin Held Evangelische Akademie Tutzing P.O. Box D-82324 Tutzing, Germany Phone: +49-8158-251-116 Fax: +49-8158-251-133
Prof. Dr. Walter K16pffer C.A.U. - WG Assessment of Chemicals, Products and Systems Daimlerstraf~e 23 D-63303 Dreieich, Germany Phone: +49-6103-983-28 Fax: +49-6103-983-10
Understanding Regional Metabolism for a Sustainable Development of Urban Systems': Peter B a c c i n i
Dept. of Civil and Environmental Engineering, Swiss Federal Institute of Technology Zurich, ETH H6nggerberg, CH-8093 Zurich, Switzerland 1
Introduction
Abstract cities are the most complex forms of settlements which man has built in the course of his cultural development. Their "metabolism" is connected with the world economy and is run mainly by fossil energy carriers. Up to now there are no validated models for the evaluation of a sustainable development of urban regions. The guidelines for a "sustainable development" suggest the reduction of resource consumption. The article is concerned with the problem of how the "sustainable-development concept" can be transformed from a global to a regional scale. In urban settlements the strategy of final storage should be applied. By this, the subsystem waste management can be transformed within 10 to 15 years to a "sustainable status". With regard to the system "agronomy", the article concludes that agriculture in urban systems should focus on food production instead of promoting reduction of food production in favour of energy plants, which is not a suitable strategy. The main problems are the energy carriers. Transformation to a %ustainble status" is only possible by a reconstruction of the urban system, i.e. of buildings and the transportation network. The rate determining step in achieving such a status is the change in the fabric of buildings and in the type of transportation networks. The reconstruction of an urban system needs, mainly for economical reasons, a time period of two generations. Key words: Sustainable development; regional material management; metabolism; material flows; urban systems; waste management; energy; carbon fluxes; anthroposphere; agronomy; forestry
Cities are the most complex forms of settlements which m a n has built in the course of his cultural development. The u r b a n architecture reflects the socio-political character of a city and the cultural, economic a n d technological status of its inhabitants. Their m e t a b o l i s m is connected with the world economy and is r u n mainly by fossil energy carriers. Up to n o w there are no validated models for the evaluation of a sustainable development of u r b a n regions. The guidelines for a " s u s t a i n a b l e d e v e l o p m e n t " (IUCN 1980 and W C E D 1987) suggest the reduction of resource consumption per capita to secure the needs of future generations with a global p o p u l a t i o n of a b o u t 8 - 10 billions. Looking at the present distribution of a n n u a l energy c o n s u m p t i o n on a global scale, the industrial countries with their u r b a n settlements are responsible for 7 0 - 8 0 % of the total. For u r b a n systems of the developed world, the following question arises: H o w can they transform the "sustainabledevelopment concept" from a global to a regional scale? Some answers to this question are based on metabolic studies of densely p o p u l a t e d regions in developed countries (BACCINI and BRUNNER 1991; BACCINI a n d BADER 1996)
* For the definitionof the term "metabolism"see BACaNIand BADER1996.
108
ESPR - Environ. Sci. & Pollut. Res. 3 (2) 108-111 (1996) 9 ecomed publishers, D-86899 Landsberg, Germany
Series 2
The Transformation of Rural to Urban Systems
Until the beginning of the 19th century, cities were the regional centre of an agrarian culture. With progressing industrialisation and democracy, the once distinct boundaries between rural and urban settlements began to break up. At the end of the 20th century the urban population, which already makes up more than half of the global population shows exponential growth. In the Swiss Lowlands - located between Lfiman and Lake Constance -, a region of about 200 km 2 with 100'000 inhabitants serves as a case study (OSWALDand BACCINI 1996). A first assessment of the material fluxes through the anthroposphere (the sphere in which human activities such as "to nourish", "to reside", "to transport", etc. take place) reveals that about 25 tonnes of goods per capita were used to fulfil the needs of the various activities of rural man around 1800. The main fluxes consist of water, followed by air and construction materials (--) Fig. 1). It is a solar system, driven by regionally gained biomass. At the end of this century, modern urban man needs about 100 tonnes per capita and year. This system is driven mainly by fossil fuels. Since the population has increased by a factor of 7, the anthropogenic fluxes in the region have increased by a factor of 30 (mass per km 2 and year).
Fig. 1: The metabolismof rural man (1800) and urban man (1995) The stock in construction work (the mass of buildings and transport networks) has increased by a factor of 4, from 80 to 300 tonnes per capita. This per capita increase is mainly due to the development from 1950 to 1990, when the per capita stock grew exponentially. This process is not finished yet because the metabolism, especially with regard to the goods "solids/fuels", has not yet reached a steady state.
3
The Concept of Sustainable Development and its Application on a Regional Level
Three case studies illustrate methods of transforming the concept of "sustainable development" for a regional level.
3.1 Waste management In the waste management of urban settlements the "weakest part" of the system is the process "deposition of solid residues". During the last decades, environmental protection measures have set their priorities in the cleaning of waste waters and off gases. For the deposition of solid residues, three main strategies are known (BAccINI 1989): ESPR- Environ. Sci. & Pollut. Res. 3 (2) 1996
Environmental Management Strategies 1. The containment strategy, in which a dense envelope is constructed to prevent interactions of wastes with the environment. The alternatives are specific geological formations in the lithosphere. Since the content is not changed in its physical and chemical properties during storage, the hazardous potential remains. Future generations have to control the functioning of the envelope. Up to now this strategy was restricted to specific fractions of hazardous wastes. 2. The controlled reactor strategy, in which a biochemical process is run with wastes reacting with water, air and, in the presence of organic materials, with micro-organisms. From field experiments and geochemical modelling it is known that such reactors run for several hundred years until emissions are reached which are compatible with the environment (BELEVI and BACCINI 1989). As with strategy 1, future generations have to handle the wastes of their ancestors. At present this strategy dominates in the developed countries. 3. The final storage strategy, in which all solid wastes which cannot be reused are treated to yield only earth crusts such as stones, ores and soils (BACCINI et al. 1991). Each generation transforms its waste completely, technically and economically. This is one consequent application of the sustainability concept. For such a strategy, thermal treatment processes are indispensable. Only few regions can follow such a strategy. Switzerland started with this third strategy in 1986. The intermediate results (1995) are as follows: - Due to more sophisticated thermal treatment plants the costs for mixed solid wastes have more than doubled and are now in the range of 300-400 USD per tonne. The mixed solid waste fluxes were reduced by 30 % (average value), from 360-400 to 240 to 360 kg/capita & year and are still in the process of reduction. - Separate collection has strongly increased. The main resource fluxes from private households (biomass, plastics, metals, glass, paper) follow this path into recycling (BACCINI et a1.1993). - Industry and trade have installed new equipment and technical processes to reuse goods from separate collection. - The federal government decided to cease reactor land filling definitely by the year 2000. The average costs per capita and year amount to 100-200 USD, which corresponds to about 0.4 per cent of the average net income per capita and year. The material fractions to be deposited are summarised in Table 1. The input is an order of magnitude higher than the output. "Land filling" is not a quantitative but a qualitative problem. Most actual residues from thermal treatments do not have a "final storage quality" yet. However, this is a minor problem and can be solved with reasonable economic efforts. Waste management as a subsystem in the regional material management of densely populated and developed regions can be transformed within 10 to 15 years to a "sustainable status".
109
Environmental Management Strategies Table 1:
Balanceof solid material fluxesfor a Swiss Lowland Region
Type of material
Flux in kg per capita and year
Input: Construction materials (mainly gravel, sand and stones, from regional sources) Output: Bottom ashes Residues from gas cleaning Construction wastes (inorganic)
7000-9000
100-150 10- 15 200-700
300-900
Total
3.2
Series
Agronomy and forestry
In the Swiss Lowlands, the agricultural land covers about 55 % and the forests about 33 % of the total area. The urban system of about 12 % is like a network embracing the patches of biomass production. Agronomy and forestry use less than 5 % of the total labour activity and produce less than 5 % of the GNP. The two economic branches are subsidised by about 1000 USD per capita and year to keep their living standard. Due to economical reasons, forests can not be fully harvested (yield about 75 %). In some agricultural branches (crops, milk) there is overproduction. The emissions from agriculture to air and water (mainly nitrogen and phosphorous) reduce their quality significantly. Agricultural soils are ecologically endangered. The carbon metabolism ( ~ Fig. 2,) is a good example to analyse the main characteristics of biomass management. For the system chosen, the fluxes and carbon concentrations of each commodity are taken from various studies already published (MOLLER et al. 1995). The corresponding carbon fluxes and the error propagation are calculated with SIMBOX (BACCINI and BADER 1996). In Fig. 2 the five processes within the anthroposphere (food processing, industry and trade, energy transformation, consumption in settlements, waste management) are combined as one single process "operation of settlement areas". This process is responsible for the predominant carbon flux. The input results mainly (90 %) from imported fossil fuels. Approximately 60 % of the demand for food is covered by the regional agriculture. The rest has to be imported. The carbon turnover of the process "Agriculture" is 3 to 4 units higher than the one of "Forestry". Their combined net contribution to the target process "operation of the settlement area" is only about 10 % of the total. The largest stocks are found in the soils of the latter two processes. However, the concentration of the organic carbon in soils is relatively low (a few per cent). The most concentrated forms are in the forest trees and in the wooden parts of buildings. Both are in the same order of magnitude (103 kg/capita). Present urban systems of this type thus depend mainly on external organic carbon sources to run their metabolism.
Fig. 2:
Carbonfluxes in a Swiss Lowland region (Fluxes in kg per capita and year; stocks in kg per capita)
duces affluent food (from a national point of view). Food production should be reduced in favour of specific energy plants such as miscanthus sinensis, grass or wood. Table 2 shows the resulting energy fluxes and the reduction of CO 2. The effects are marginal. A closer look at the energy content of organic wastes from agriculture and forestry leads to the conclusion that only about one third of its total potential is used. This potential is definitely higher (at least by a factor of three) than the proposed scenario with energy plants (MOLLERet al 1995). With regard to the concept of a sustainable development, a reduction of food production in favour of energy plants is not a suitable strategy. Different studies show (e.g. BUITENKAMP et al. 1992) that on a global scale mankind will encounter food shortage within one to two generations (30 to 60 years). Assuming the present per capita consumption of wood continues, the forests could meet the demands of the next generations. In conclusion, one can postulate that agriculture in urban systems should focus on food production.
Table 2:
Contribution of Agriculture (A) and Forestry (F) with energy plants (as net energy in Gigajouleper capita and year). Use of 5 % of the total agricultural land (after MOLTERet al. 1995) i
Energy (GJ/cap y) CO2-Reduction (%)
Crop Miscanthus sinensis
1.6
1.8
Grass
0.5
0.6
3.2.1 The potential of agriculture and forestry in the regional carbon household
Wood
0.6
0.7
Bio-Waste of the total A&F
5-7 a
2-3
One specific measure in carbon management is the promotion of energy plants in an agricultural practice that pro-
a actual use: 1.5 GJ/cap y
1 10
ESPR - Environ. Sci. & Pollut. Res. 3 (2) 1996
Series 3.3
Buildings and transportation networks
The metabolism of the urban settlement area needs the following mass goods (see also Fig. 1): Water, biomass, construction materials and energy carriers. As a first working hypothesis, the following two criteria are chosen to examine the potential for a sustainable development of the region: 1. The metabolism of an urban system is "sustainable", if the demand for essential "mass goods" such as water, biomass, construction materials (e.g. stones) and energy carriers can be satisfied autochthonously by > 80 % in the long term. The degree of self-sufficiency, arbitrarily chosen with respect to a set of essential goods, determines the ecologically defined border of the urban system. 2. The rest can be covered from the "external market" in such a way that the global resource capitals are not reduced significantly. The mean fluxes of available goods per capita from the external market are determined by the annual growth rate of the "global Hinterland", divided by the world population. A first analysis of a Swiss Lowland region leads to the following results (OSWALDand BACCINI 1996): Water: The region is self-sufficient with respect to the quantity needed (ground water). However, the quality is constantly decreasing, mostly due to agricultural emissions, i.e. the water household is not sustainable. Biomass: The activity "to nourish" can be supported autochthonously by 60 %. With a low meat diet (10 kg meat instead of 80 per capita and year), the region could become "sustainable" if the emissions to air and water are reduced simultaneously. The forestry could theoretically cover the regional demand for wooden products (timber, pulp), but is presently not economically competitive. Construction materials: The region is self-sufficient with respect to gravel and sand, but will exhaust the stocks within the next 30 years, assuming the same rate of exploitation. Theoretically, there are alternatives in the lithosphere. However, their exploitation will need more energy. Energy carriers: More than 90 % of the energy result from external resources. About 80 % of the energy flow into "building maintenance" and transportation. It follows that a transformation to a "sustainable status" is only possible by a reconstruction of the urban system, i.e. buildings and the transportation network. The mass good energy and the existing "architecture" are the key factors. The rate determining step in achieving such a status is the change in the fabric of buildings and in the type of transportation networks. The capital invested in the "construction" (---~Fig. 1) amounts to 300'000 USD per capita. The annual expenditures for their metabolism amount to 10'000 USD per capita, that is in the same order of magnitude as the average annual net income. The reconstruction of an urban system needs, due to economic reasons, a time period of two generations or about 60 years {assuming an annual change of I - 2 % of the stock). The per capita net energy demand, at present 120 GJ/cap & y, should be reduced by a factor of three (to 40 units), ESPR - Environ. Sci. & Potlut. Res. 3 (2) 1996
Environmental Management Strategies corresponding to 2 kW per capita (primary energy). This is in agreement with a global threshold consumption proposed by the World Energy Conference. There are distinct measures to achieve these goals, for example: - reduce heating of buildings from 600 MJ/m 2 9y (100 m2/capita) to 200 MJ/m 2. y (or 20 GJ/cap. y). - reduce transportation energy for persons and goods from 30 GJ/cap 9y to 10 GJ/cap 9y. Theoretically, there is enough building surface available (300 m2/cap) in the settlement area to realise this concept technically. With 5 % efficiency from 200 W/m 2, about 70 m2/cap are needed to produce 20 GJ/cap 9 y. Such a scenario for 2050, shown in comparison with the present energy supply in Fig.3, is technically achievable but economically not yet favourable (approximately fivefold energy prices), due to the fact that fossil energy is still available at low prices.
Fig. 3:
4
Comparison of energy supply sources at present (1990+, light bars) with a solar scenario (for 2050+, hatched bars) in a Swiss Lowland Region
References
BACCINI,P. (Ed.) (1989): The Landfill: Reactor and Final Storage. Lecture Notes in Earth Sciences Vol.20, Springer, Berlin Heidelberg New York BACClNI,P.; BRUNNER,P.H. (1991): Metabolism of the Anthroposphere. Springer, Heidelberg New York BACCINI,P.; BELEVI,H.; Lichtensteiger, Th. (1992): Die Deponie in einer 6kologisch orientierten Volkswirtschaft. GAIA 1, 34-49 BACCINI,P.; DAXBECK,H.; GLENCK,E.; HENSELER,G. (1993): METAPOLIS, Giiterumsatz und Stoffwechselprozesse in den Privathaushalten einer Stadt. Nationales Forschungsprogramm NFP 25 "Stadt und Verkehr", Ztirich BACCINI,P.; BADER,H.P. (1996): Regionaler Stoffhaushalt (Regional Material Management). Spektrum Akademischer Verlag, Heidelberg BELEW,H.; BACC~NI,P. (1989): Long-Term Behaviour of Municipal Solid Waste Landfills. Waste Management and Research 7, 43-56 BUITENKAMP,M.; VENNER,H.; WAMS,T. (Eds.) (1992): Action Plan Sustainable Netherlands. Friends of the Earth Netherlands, P.O. Box 19 199, Amsterdam IUCN 1980: World Conservation Strategy, Gland MI]LLER, D.; OEHLER,D.; BACCIN1,P. ,(1995): Regionale Bewirtschaftung yon Biomasse (Regional Management of Biomass). vdf, Hochschulverlag AG an der ETH Ziirich OSWALD,E; BACCINI,P. (1996): Synoikos, an intermediate report, ETH Zurich WCED 1987: Our Common Future. New York, Oxford University Press
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