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ISWA and DAKOFA Annual Congress 2006: Waste Site Stories

The significance of boundary conditions and assumptions in the environmental life cycle assessment of waste management strategies - a large international review of existing studies. Henrik Wenzel, Institute for Product Development, Technical University of Denmark, Denmark wenzel@ipl.dtu.dk.

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ISWA and DAKOFA Annual Congress 2006: Waste Site Stories

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  1. The significance of boundary conditions and assumptions in the environmental life cycle assessment of waste management strategies- a large international review of existing studies Henrik Wenzel, Institute for Product Development, Technical University of Denmark, Denmark wenzel@ipl.dtu.dk ISWA and DAKOFA Annual Congress 2006: Waste Site Stories Driving Waste Management towards Sustanable Development 1st – 5th Octobre 2006, Copenhagen, Denmark

  2. Literature search approach and outcome The international literature search contained three main elements: • A targeted approach to LCA institutions and experts worldwide and material institutions and waste institutions • A broad search of the scientific literature • An international Internet search via search engines and homepages of relevant institutions (mainly national Environmental Protection Agencies) Evaluated and selected studies

  3. Criteria for final inclusion of studies in the review • The study was to be an LCA or LCA-like study complying with LCA quality standards • The material stream in question was analysed and reported on separately, that is, not as a part of a mixed waste stream • The study included a comparison of two or more scenarios for the end-of-life handling of the material stream in question. OBS: In practice, all studies comprising a quantitative environmental comparison of waste management options also met the other two criteria and were included

  4. Results and conclusions were held up against system delimitation issues Essential system delimiation issues identified in the paper and cardboard review

  5. Results and conclusions were held up against system delimitation issues Essential system delimiation issues identified in the other material stream reviews

  6. Waste management comparisons Scenarios comparing: • recycling to incineration • recycling to landfill • incineration to landfill System boundary approaches: R I L A B A: Quantitative and relative presentation possible B: Quantitative, but not relative presentation possible

  7. Result presentation format – example: paper and cardboard - energy [Impact from recycling] - [Impact from incineration] _________________________________________ [Impact from incineration] %

  8. Example: Paper and cardboard - GWP

  9. Paper and cardboard

  10. Paper and cardboard

  11. Paper and cardboard

  12. Paper and cardboard

  13. Paper and cardboard- GWP quantitatively

  14. Paper and cardboard- GWP quantitatively

  15. Paper & cardboard- 4 key issues divide the conclusions • The virgin pulp type – i.e. the energy split between electricity and thermal energy in production of the various virgin paper and cardboard types • The marginal electricity assumed for virgin paper/cardboard production • The potential utilisation of the extra incineration capacity created by recycling to reduce landfilling • The inclusion of an alternative use of saved wood for virgin paper/cardboard production

  16. The virgin pulp type

  17. The marginal electricity assumed for virgin paper/cardboard production

  18. Utilisation of released incineration capacity

  19. The inclusion of alternative use of saved wood

  20. Overview of results/conclusions Overall environmental preference (no. of scenarios):

  21. Conclusion • The results and conclusions of the LCA can depend significantly on the assumptions behind the system modelling and –delimitation • LCAs comparing waste management options for paper & cardboard are very sensitive to such assumptions. A total of 15 important assumptions have been identified, 4 of which have been found to be essential to the outcome of the study: • The type of pulp in question • The assumption of marginal electricity for virgin paper production • The inclusion of alternative use of saved incineration capacity to reduce landfilling of burnable waste • The inclusion of alternative use of saved biomass • Other generally essential assumptions are: • The recovered material to virgin material substitution ratio • The contamination of the material before recovery • This analytical review of the relations between system assumptions and results/conclusions of LCAs allows us to explain any differences in the outcome of LCAs comparing material waste management options

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