The intentional and unintentional release of wastes into the environmental media produce a wide range of impact pathways, many of which of complex and uncertain quantification. It should be always reminded that the efforts of public authorities to promote the development of an industrial sector aimed to avoid a “free release” into the environmental media and based on the collection, treatment and recovery of waste streams have the implicit aim to reduce the external costs produced by wastes. These efforts imply the high investment and management costs of modern waste management techniques (including those for environmental control), and consequently the generation of social costs through waste charges (or higher general taxes) or even the generation of social benefits through the money savings obtained by using low cost recycled materials. This very complex and context variable organisation doesn’t mean that wastes don’t produce external costs.

The most important impact pathways linked to waste management are:

- Greenhouse gases (CO2 emissions due to the combustion of the non organic waste fraction and CH4 emissions from landfills without gas recovery system)

- Air pollutants harmful for health through direct and agricultural pathways (PM, NOx, SO2, NMVOC, cadmium, dioxins, furans and other micro-pollutants)

- professional health risks from biological agents (virus, bacteria, fungi, etc.),

- amenity losses (bad smells, landscape impacts, etc.)

- fire risk associated to waste deposits

- pollution risks for land, rivers and ground waters (long term risks due to landfills protection layers degradation).

Waste management may produce external benefits, in relation to the obtained recycling rate (external costs avoidance of the primary materials production) and to energy production (heat and electricity) obtained by burning the recovered landfill methane or by directly burning waste fractions (waste thermal plants).

The greater part of the quoted impact pathways have been extensively analysed and valued by European research. The most extensive studies on waste treatment external costs are those realised with the upgraded version of the ExternE methodology within the so-called Methodex EU research project.
On the basis of existing methodologies, external costs of landfill technologies and of incineration plants (with or without energy recovery systems) may be systematically analysed and even compared by using alternative scenarios. Outcomes are influenced non only by technological assumptions, but also from context variables (national mix of production plants in valuing energy recovery benefits, landscape damage, population exposed to odours, willingness to pay for avoiding bad odours, etc.) and from discount rate assumptions. Since much of landfill environmental impact factors are produced in the longer term as compared to the incinerator ones, the level of discount rate may advantage landfill valuation in relative terms. Sustainability assumptions in valuing technologies are suggested.

© 2006 - Andrea Molocchi