An overview of the greenhouse gas implications of material recovery and recycling is presented for a variety of materials, i.e. steel, aluminium, glass, plastics, wood, paper and cardboard, aggregates and wood. The benefits of recycling in terms of greenhouse gas reductions are quantified and set in perspective to other measures. It is shown that the present aluminium recycling alone in a country like Denmark saves greenhouse gas emission equivalent to heating of over half a million family houses. Assumptions and system boundaries are often discussed in the quantification of the benefits of recycling. An analysis of the key system boundary assumptions is done showing the significance of the assumptions to the result and conclusion. The paper and cardboard system is the one most sensitive to assumptions, and differences in assumptions can reverse results and conclusions for this specific material category. Each of the key assumptions is discussed in both the short and long term perspective, and a scenario approach is used to interpret and discuss the probabilities of assumptions. Especially, the modelling of biomass in future systems is crucial to the results and conclusions on paper & cardboard recycling. It is argued that biomass should be considered a constrained resource in a long term perspective, and that the marginal for the use of biomass is either a fossil resource or an arable land resource. In both cases, use of biomass draws on a marginal with high greenhouse gas implications. Accordingly, the saving of pulp wood for virgin paper will save the marginal of either fossil fuels or arable land leading to unambiguous benefits of paper/cardboard recycling. The role of transport in recycling schemes is discussed, and it is demonstrated that recycling does not necessarily lead to increased transportation. It may well turn out that the few kilometers between the household and the waste collection station has the highest transport related greenhouse gas emission due to the use of a personal car for this distance – as opposed to shipping the materials from Europe to e.g. China by a container ship. This demonstrates that the geographical distribution of material supply chains not necessarily leads to increased greenhouse gas emissions, the degree of recycling is of much higher significance.
Waste & Climate Conference: Messages To Cop15, 2009
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Waste & Climate Conference - messages to COP15, 2009