The ecology of recycling.

• Author: Chertow, Marian
• Position: Report

While not on the front line of climate solutions, recycling of waste materials, wastewater, and wasted energy is a locally available and highly desirable means of reducing greenhouse gases. One potent greenhouse gas, the methane emitted from landfills and wastewater, accounts for about 90 per cent of greenhouse gas emissions from the entire waste sector. That amount is 18 per cent of human-caused methane emissions globally and about three per cent of total greenhouse gases, according to the Intergovernmental Panel on Climate Change. (1) Diverting waste bound for landfills and putting it to good use, then, is an obvious and proven means for conserving land and resources, as we have known for a long time; we can now add the knowledge from numerous studies that these practices also bolster climate protection.

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This article draws on examples from around the world to describe the climate effects of 1) household recycling and reuse, 2) the cyclic resource flows across clusters of companies known as "industrial symbiosis", and 3) far reaching policy proposals for national scale resource use. It draws lessons from the system's perspective provided by industrial ecology, a new field resolutely focused on the flows of material, energy, and water through systems at different scales, from products to factories to countries and regions.

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How does resource reuse affect climate? Cycling energy through cogeneration, reuse of agricultural wastes, or recovery of energy-intensive materials such as aluminium, reduces greenhouse gases. Since most commercial energy is produced from burning fossil fuels, the power generation sector emits more greenhouse gases than any other industrial sector. Cycling materials for use in other production processes reduces the lifecycle impacts, when compared with virgin materials that must be extracted from the earth and then transformed and transported through numerous stages. Recovered resources free up land and capital for other opportunities that would have been required for the equivalent amount of goods to be made from virgin resources. Cycling water means using it more than once, a critical and increasingly urgent practice where water is scarce owing to expected changes in precipitation patterns brought on by climate change. To capture these concepts, industrial ecologists use the term "embedded utility": the total amount of the water, energy, and materials used for all different lifecycle stages of a product from beginning to end. (2) Embedded utility is central to industrial ecology: if a product is landfilled, these resources are lost.

HOUSEHOLD WASTE AND RECYCLING

Study after study in the last five years from Brazil to Canada and from Europe to Asia affirms the ability to quantify greenhouse gas emissions from household waste on a lifecycle basis. Each of these lifecycle studies finds a clear, positive impact of recycling and reuse on reducing greenhouse gasses, principally because of recapturing, rather than discarding, the embedded energy, water...