Modelling of life cycle assessment of solid waste management systems and technologies

Janus Torsten Kirkeby

Research output: Book/ReportPh.D. thesis

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Abstract

A new computer based model for environmental assessment of municipal solid waste systems and technologies has been developed. The name of the model is EASEWASTE, which is an abbreviation of Environmental Assessment of Solid Waste Systems and Technologies. The model enables, by the use of life cycle assessment, comparisons between different waste management strategies and different technologies within a waste treatment method. Life cycle assessment is a systematic and holistic approach of evaluating resource consumption, potential impact on humans and on the environment of a product or service including all upstream and downstream activities. The model is developed so sources of potential environmental impacts can be traced back to an activity, to a waste material fraction and to a substance in a waste material fraction. The model is designed to be flexible, transparent, user-friendly and well documented in order to ensure widely use by local and regional waste planners as well as by uthorities
setting guidelines and regulations.

The functional unit of the model is waste management of an amount of household waste generated in an area that is divided into three main types of residential areas: single family housing, multi-family housing and small commercial business units producing household like waste. The system boundaries of the model cover “Waste bin to grave”, i.e. the point from where products become waste and put into the waste bin at the waste generation source to the point where the waste and arisen residues are inert and will not contribute to any further environmental impacts. This point is partly defined by the overall time frame for emissions from landfills. The environmental exchanges, resource consumption and emissions, are calculated for collection, treatment of waste and residues, landfilling, remanufacturing and reuse. Also, processes that occur upstream or downstream of the waste system are included. These include manufacturing of material input to the waste management system as well as substituted materials where production is assumed avoided because of material and energy recovery. Any avoided resource consumption or emissions due to avoided production of energy or materials are included as negative consumptions and emissions resulting, in some cases, that the overall impacts can become negative in cases for waste management systems with a high level of energy recovery or recycling. An extensive model for use of compost or other biomass on soil is included calculating benefits and drawbacks compared to use of commercial fertiliser.

The EASEWASTE model has been used on the waste management system of the Municipality of Aarhus, the second largest city of Denmark, to compare the traditional waste incineration with a scenario including biogas production from organic household waste. Both scenarios showed to produce large amounts of district heating and electricity, thus a large saving of energy resources and emissions of green house gasses arises. The study showed that there were no significant differences in the consumption of resources or the environmental impacts with exception of potential human toxicity via soil, when residue from the biogas plant is used on agricultural land. Other results showed that by recycling of glass and of paper resources were saved and potential environmental impacts were avoided.

There are a number of challenges and limitations by applying life cycle assessment and EASEWASTE on municipal solid waste systems. Allocation problems of input and emissions from treatment options treating more than one type or fraction of waste, market based system expansion for recovered material and time frames including estimation and future uses of area are some of the problems that have to be dealt with in a serious manner. The current version, EASEWASTE-2004, have some limitations in not including social and environmental costs of the solid waste management systems, but this is usually not included in life cycle assessments. Site variations, considering the sensitivity of the ecosystem where emissions actual occur, are not yet part of the life cycle impact assessment. Life cycle impact assessment methods are continuously being improved to consider some of these aspects.

Future versions of EASEWASTE will, as developments in life cycle impact assessment methods are made and being generally accepted, implement these new methods. Also social and environmental costs are planned to be implemented in the near future.
Original languageEnglish
Place of PublicationKgs. Lyngby
PublisherDTU Environment
Number of pages50
ISBN (Print)87-89220-88-9
Publication statusPublished - Mar 2005

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