A Methodology to Support Infrastructure Development for Sustainability

Abstract

Policy makers and planners are becoming more and more aware of the impact of humankind’s combined consumption on the planet, both in terms of environmental impact and in terms of the shrinking amount of resources remaining to us that will be needed to support future generations. Sustainable development is no longer an option to postulate for one day in the future; the question now is how we can strategically approach infrastructure development so that sustainable practices are embedded into the structure of society while living standards continue to increase globally in line with modern expectations. Due to the limitations in our knowledge of how to operate a society in a sustainable manner, many approaches have been mooted, but none have yet been widely adopted. Small-scale experiments have arisen spontaneously in diverse settings and ranging from solid waste management to food supply to electricity generation; however, holistic solutions have stalled in the theoretical stage. Currently, it is simply too complex and too difficult to sustainably provide all human needs (broadly: food, water, energy, and materials) in all areas of society (residential, commercial, and industrial) as inputs and outputs; in other words, society’s metabolism. Small island developing states (SIDS) present a special case for sustainability. These are generally remote countries with small populations and very limited resources, often heavily dependent on remittances and imports from overseas, making them some of the least resilient societies in the world. They stand to benefit hugely from strategic sustainable development, while also acting as a microcosm for testing the implementation of holistic sustainability practices that larger countries or regions could replicate. This research presents a needs-based anthropogenic model of a societal metabolism’s formal and informal infrastructure systems, drawing on the well-established principles of industrial ecology and its more recent quantitative methodologies, namely urban metabolism (UM) and material flow analysis (MFA). The methodology and model developed in this research are used to determine the carrying capacity of a country and thus quantify its self-sufficiency and sustainability, and where targeted infrastructure development would make the most difference to sustainable operation. This model is tested as a proof-of-concept with a case study SIDS, on Samoa, a geologically young group of islands in the South Pacific with a moderately small population of 184,000 (and an equivalent annual tourist population of 5,000). Infrastructure systems are a crucial element in determining the carrying capacity and sustainability of a society. Their role has been acknowledged in the literature, but their interactions and interdependency on one another, and with the societal metabolism they serve, has not been well studied in a sustainability context. The UM-MFA hybrid methodology developed for this research is a novel contribution to the body of knowledge, that combines the advantages of both urban metabolism and material flow analysis into a detailed planning tool that disseminates processes, consumption, and production by tracking flows of resources through infrastructure systems. Furthermore, it has the demonstrated potential to be developed into a dynamic predictive model, which has not previously been achieved with urban metabolism or material flow analysis. The model provides insight into carrying capacity and analyses planned projects for their impact on future potential carrying capacity, and quantifies the interrelationships between infrastructure systems, which may enable authorities to identify opportunities to improve their efficiency and enhance planning for sustainable development. The working model created for Samoa demonstrates that the methodology is successful in addressing the research objectives. Modelling Samoa’s societal metabolism consisted of constructing a static snapshot conceptual and quantitative model of resource flows moving through Samoa’s infrastructure systems according to consumption of basic needs (food, water, energy, and materials). The UM component shows input and output totals, allowing comparison with other places and offering a degree of characterisation of the kinds of needs and wants encompassed by that particular society, and the materials flow analysis component shows infrastructure systems used to supply those needs and wants. As cultural aspects influence consumption behaviour, and geographical aspects influence present infrastructure and potential infrastructure development, it was important to first gain this understanding of location-specific characteristics, and these will be different for every society, so this is necessarily a first step with this methodology, and is also a key element in interpreting the results. Results showed that Samoa’s total mass inflows were 54,210,000 tonnes per year for the 2009 averaged societal metabolism. Of this, 53,301,000 t/year (95%) is water. Energy inflows totalled 5,098,000 GJ/year. By metabolic category, food input was 1.3 t/capita/year; water input was 271 t/capita/year; materials input was 13.4 t/capita/year; and energy input was 20.8 GJ/capita/year. Samoa’s food and water inputs are high compared to other locations where similar studies have been conducted; energy and materials inputs are much lower than other locations. These inputs correspond (after exports and efficiency losses) to a consumption level of 1.0 t/capita/year for food (3,680 kcal/capita/day by energy); 187 t/capita/year for water; 13.0 t/capita/year for materials; and 7.5 GJ/capita/year for energy. Materials had the highest efficiency of use (at 97%), probably because this category mainly comprises finished goods imported into Samoa, that can’t be manufactured locally. Energy had the lowest efficiency of use (at 36%), because of Samoa’s dependence on old and inefficient diesel generators for electricity production. Samoa’s outputs totalled 2,131,000 t/year, or 11.3 t/capita/year, of which 1,404,000 t/year (66%) is domestic wastewater. Wastewater output was 7.4 t/capita/year, low compared to the water input and low compared to other locations; this is probably due to the type of toilets commonly used in Samoa and the dewatering role of septic tanks and pit latrines, the main types of sanitation infrastructure on the islands (they also chronically leak, causing increasing contamination of groundwater). Atmospheric emissions are the second largest output category at 3.0 t/capita/year, mainly consisting of CO2 emissions. Samoa’s solid waste output was 142,000 t/year, or 0.8 t/capita/year, which was low compared to studies from other locations. 21,000 t/year of organic solid waste (15% of all solid waste) was redirected within Samoa’s societal metabolism, reducing its environmental impact; this mainly comprised food scraps and green waste which is fed to livestock or composted, respectively. Other solid waste vectors include landfilling, emissions to atmosphere, runoff to sea, exported recycling, dumping on land or in lagoons, and burning. In terms of sustainability, which is taken here to represent fully local production of basic mass goods (in each metabolic category) as a means of providing self-sufficiency, Samoa is only completely sustainable (100% local supply) in water; local supply of food, materials (including CO2), energy, and materials (excluding CO2) is 79.1%, 49.3%, 21.3%, and 7.1%, respectively. Samoa’s carrying capacity for the 2009 societal metabolism, based on the category with the lowest local supply proportion (materials, excluding CO2 uptake by vegetation), is 13,514 people, compared to a total local and transient (tourist) equivalent population of 189,274. Because it is a function of both supply, which can be altered by infrastructure and technology, and demand, which can varying depending on levels of consumption, the carrying capacity will change. Samoa’s available resources (local and total, the latter including imports) and its 2009 levels of consumption were thus analysed against sustainability recommendations, basic human needs, average developing countries’ consumption, and average developed countries’ consumption, to quantify the carrying capacity for various levels of demand, and 2009 total and local supply, and potential local supply, against these reference values. Local food production could be increased through the Samoan Government’s plans to increase agricultural productivity by an extra 18,500 t/year, which would increase local production to 104% of 2009 consumption. Combined with a demand reduction to the recommended long-term sustainability level, Samoa could support over 230,000 with local food production. This would also address their high food intake, which may be a cause of the high incidence of obesity in Samoa. Although water is currently fully sustainable, efficiency gains and guttering on corrugated iron roofs could increase local supply by 15,404,000 t/year, meaning that if the population were to increase by an additional 50,000 people, water consumption levels could remain the same as at 2009. At lower consumption levels, Samoa’s water supply could support over two million people, a population level unlikely to be reached for at least a century. Energy shows the greatest potential for local sustainable development, with up to 944,000 GJ/year additional supply through capacity expansion and demand reduction, which would raise the local production proportion to between 45% and 125% (depending on efficiency). This would be achieved by producing biodiesel from coconuts, and bioethanol from breadfruit, and embarking on renewable electricity generation projects, including hydropower, on-grid solar, and wind power generation. Materials is not a category for which the Government has planned new supply projects, but opportunities have been identified to close the loop by reusing waste products, and by making better use of locally available construction materials, which would increase local supply to 55%. In order to improve local carrying capacity of materials, building design and construction materials should preferentially move away from reliance on imported steel and pre-cast concrete, and towards traditional (locally-abundant) building materials such as wood, copra, rock, dead coral, and sand. This may involve harvesting volcanic rock from lava fields and crushing it to the correct size, and should involve a sustainable forestry management plan to enable long-term wood harvesting. A shift from woodfuel to electricity for cooking (in line with present trends) should further support this, freeing up to 42,000 t/year of wood for other purposes. Although Samoa was not sustainable in 2009, and was not on a sustainability trajectory at that time, the proposals outlined by the Samoan Government and this research would shift Samoa’s development path to a more self-sufficient, and more sustainable, future. With management of both supply and demand, Samoa could become fully self-sufficient in three of the four main metabolic categories (food, water, and energy), and more than half self-sufficient in materials (including CO2).