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Greenhouse gas (GHG) emissions from post-consumer waste and wastewater are a small contributor (about 3%) to total global anthropogenic GHG emissions. Emissions for 2004-2005 totalled 1.4 Gt CO2-eq year(-1) relative to total emissions from all sectors of 49 Gt CO2-eq year(-1) [including carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and F-gases normalized according to their 100-year global warming potentials (GWP)]. The CH4 from landfills and wastewater collectively accounted for about 90% of waste sector emissions, or about 18% of global anthropogenic methane emissions (which were about 14% of the global total in 2004). Wastewater N2O and CO2 from the incineration of waste containing fossil carbon (plastics; synthetic textiles) are minor sources. Due to the wide range of mature technologies that can mitigate GHG emissions from waste and provide public health, environmental protection, and sustainable development co-benefits, existing waste management practices can provide effective mitigation of GHG emissions from this sector. Current mitigation technologies include landfill gas recovery, improved landfill practices, and engineered wastewater management. In addition, significant GHG generation is avoided through controlled composting, state-of-the-art incineration, and expanded sanitation coverage. Reduced waste generation and the exploitation of energy from waste (landfill gas, incineration, anaerobic digester biogas) produce an indirect reduction of GHG emissions through the conservation of raw materials, improved energy and resource efficiency, and fossil fuel avoidance. Flexible strategies and financial incentives can expand waste management options to achieve GHG mitigation goals; local technology decisions are influenced by a variety of factors such as waste quantity and characteristics, cost and financing issues, infrastructure requirements including available land area, collection and transport considerations, and regulatory constraints. Existing studies on mitigation potentials and costs for the waste sector tend to focus on landfill CH4 as the baseline. The commercial recovery of landfill CH4 as a source of renewable energy has been practised at full scale since 1975 and currently exceeds 105 Mt CO2-eq year(-1). Although landfill CH4 emissions from developed countries have been largely stabilized, emissions from developing countries are increasing as more controlled (anaerobic) landfilling practices are implemented; these emissions could be reduced by accelerating the introduction of engineered gas recovery, increasing rates of waste minimization and recycling, and implementing alternative waste management strategies provided they are affordable, effective, and sustainable. Aided by Kyoto mechanisms such as the Clean Development Mechanism (CDM) and Joint Implementation (JI), the total global economic mitigation potential for reducing waste sector emissions in 2030 is estimated to be > 1000 Mt CO2-eq (or 70% of estimated emissions) at costs below 100 US$ t(-1) CO2-eq year(-1). An estimated 20...

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The use of stainless steel, a metal employed in a wide range of technology applications, has been characterized for 51 countries and the world for the years 2000 and 2005. We find that the global stainless steel flow-into-use increased by more than 30% in that 5 year period, as did additions to in-use stocks. This growth was mainly driven by China, which accounted for almost half of the global growth in stainless steel crude production and which tripled its flow into use between 2000 and 2005. The global stainless steel-specific end-of-life recycling rate increased from 66% (2000) to 70% (2005); the landfilling rate was 22% for both years, and 9% (2000) to 12% (2005) was lost into recycled carbon and alloy steels. Within just 5 years, China passed such traditionally strong stainless steel producers and users as Japan, USA, Germany, and South Korea to become the dominant player of the stainless steel industry. However, China did not produce any significant stainless steel end-of-life flows in 2000 or 2005 because its products-in-use are still too new to require replacements. Major Chinese discard flows are expected to begin between 2015 and 2020.

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Summary A detailed understanding of material stocks in use is essential for anticipating future scrap availability, identifying critical drivers for material use, and developing strategies for resource efficiency. Here, we present a bottom‐up assessment of iron and steel stocks in use in urban and rural China for the years 2000 and 2010, including >250 subcategories of products and components, and grouping them into five main end‐use categories (i.e., buildings, infrastructure, domestic appliances, machinery, and transport equipment). The uncertainty range of the steel content per type of stock, a determinant of the accuracy and usefulness of the stock accounting, is probed by multiple means, including sample analysis. Important findings are that (1) iron and steel stocks in China have climbed to 2.4 tonnes/capita (t/cap) in 2010, up from 0.9 t/cap in 2000. The use of reinforced concrete in construction of the urban built environment was the major driver for stock growth; (2) a rural‐urban difference was uncovered, with rural iron and steel stocks of approximately 1.1 t/cap and the urban iron and steel stocks of approximately 3.7 t/cap in 2010. Both are, nevertheless, far below the level of 10 to 16 t/cap observed in highly industrialized and urbanized countries. For this reason, further stock increase is foreseeable as urbanization and industrialization proceeds and quality of life improves; (3) nearly half of the steel stocks were embedded in concrete structures, and 23% were located in the countryside. Only a fraction of these stocks are currently recovered at end of life.

Summary Rapid industrialization and urbanization has been occurring in China since the introduction of the opening‐up policy in 1978. The demands of building and infrastructure construction have increased rapidly, especially in the transportation and housing sectors in China. Large amounts of construction materials have been required in building construction and maintenance of the railway and road systems, especially steel and cement. Continued cement and steel production will require heavy raw material resource consumption and will emit a great deal of carbon dioxide (CO2). This study forecasts future steel and cement demand and related resource consumption and CO2 emissions for building and transportation infrastructure based on a material flow analysis of China. Furthermore, the effect of prolonging the lifetime of building and transportation infrastructure is appraised. The results indicate that building and transportation infrastructure will increase sharply through 2030. Although the demand for new construction will then decrease, steel and cement consumption will remain at a high level through 2050 because these are needed to maintain roads and railways. In addition, prolonging the lifetime of buildings and infrastructure is a useful way to avoid more raw material consumption and to mitigate CO2 emissions. However, its main effect is to decrease the demolition of buildings and reduce material use for the maintenance of roads and railways. Currently not enough countermeasures have been implemented to realize a low carbon–dematerialization society in the building and transportation construction sector. Future comprehensive efforts should include the reuse of waste construction material and a reduction in raw material consumption intensity by applying technical innovations.