Life cycle assessment of disposal of residues from municipal solid waste incineration: Recycling of bottom ash in road construction or landfilling in Denmark evaluated in the ROAD-RES model

• Published in: Waste management (Elmsford) Vol. 27; no. 8; pp. S75 - S84
• Main Authors: Birgisdóttir, H., Bhander, G., Hauschild, M.Z., Christensen, T.H.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 2007; New York, NY Elsevier Science
• Subjects: Applied sciences; Conservation of Natural Resources; Construction Materials; Continental surface waters; Denmark; Environmental Pollutants - analysis; Environmental Pollutants - toxicity; Exact sciences and technology; General treatment and storage processes; Incineration; Industrial Waste; Models, Theoretical; Natural water pollution; Other wastes and particular components of wastes; Pollution; Refuse Disposal; Urban and domestic wastes; Wastes; Water treatment and pollution; Denmark; ANE, Denmark; Energy consumption; Cinders; Waste dumping; Toxicity; Urban waste; Pollutant formation; Construction materials; Acidification; Pollutant emission; Modeling; Interstitial water; Coastal zone; Transport process; Upgrading; Lixiviation; Recycling; Seawater; Ground water; Warming; Life cycle (environment); Road construction; Stratosphere; Ozone; Heavy metal; Persistence; Depletion; Incineration; Environment impact; Surface water; Solid waste
• ISSN: 0956-053X; 1879-2456
• DOI: 10.1016/j.wasman.2007.02.016

Two disposal methods for MSWI bottom ash were assessed in a new life cycle assessment (LCA) model for road construction and disposal of residues. The two scenarios evaluated in the model were: (i) landfilling of bottom ash in a coastal landfill in Denmark and (ii) recycling of bottom ash as subbase layer in an asphalted secondary road. The LCA included resource and energy consumption, and emissions associated with upgrading of bottom ash, transport, landfilling processes, incorporation of bottom ash in road, substitution of natural gravel as road construction material and leaching of heavy metals and salts from bottom ash in road as well as in landfill. Environmental impacts associated with emissions to air, fresh surface water, marine surface water, groundwater and soil were aggregated into 12 environmental impact categories: Global Warming, Photochemical Ozone Formation, Nutrient Enrichment, Acidification, Stratospheric Ozone Depletion, Human Toxicity via air/water/soil, Ecotoxicity in water/soil, and a new impact category, Stored Ecotoxicity to water/soil that accounts for the presence of heavy metals and very persistent organic compounds that in the long-term might leach. Leaching of heavy metals and salts from bottom ash was estimated from a series of laboratory leaching tests. For both scenarios, Ecotoxicity water was, when evaluated for the first 100 yr, the most important among the twelve impact categories involved in the assessment. Human Toxicity soil was also important, especially for the Road scenario. When the long-term leaching of heavy metals from bottom ash was evaluated, based on the total content of heavy metals in bottom ash, all impact categories became negligible compared to the potential Stored Ecotoxicity, which was two orders of magnitudes greater than Ecotoxicity water. Copper was the constituent that gave the strongest contributions to the ecotoxicities. The most important resources consumed were clay as liner in landfill and the groundwater resource which was potentially spoiled due to leaching of salts from bottom ash in road. The difference in environmental impacts between landfilling and utilization of bottom ash in road was marginal when these alternatives were assessed in a life cycle perspective.