Environmental assessment of roads constructed with and without bottom ash from municipal solid waste incineration

Two scenarios are assessed in a new life cycle assessment model, ROAD-RES, developed at the Technical University of Denmark for road construction and recycling of residues. The scenarios concern a 1 km asphalted road in Denmark with a service life of 100 years: Scenario A was a road with natural materials only, while Scenario B was a similar road, where municipal solid waste incineration bottom ash is used as sub-base layer replacing gravel beneath the lanes. The assessment included resource and energy consumption, and emissions associated with production of road’s materials, transport, construction of the road and operation and maintenance of the road during the roads life as well as leaching of heavy metals and salts from the bottom ash, and salts used for road salting. The assessment showed that the difference between the scenarios was marginal in terms of environmental impacts and resource consumption. The majority of the environmental impacts were related to emissions from combustion of fossil fuels. Potential pollution of groundwater due to leaching of salts appeared to be important potential resource consumption, primarily due to road salting.