Life cycle assessment of a pyrolysis/gasification plant for hazardous paint waste |
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Authors: | Robert Jan Saft |
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Institution: | (1) NV ROVA Holding, P.O. Box 200, 8000 AE Zwolle, The Netherlands |
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Abstract: | Goal, Scope and Background Life Cycle Assessment (LCA) remains an important tool in Dutch waste management policies. In 2002 the new National Waste Management
Plan 2002–2012 (NWMP) became effective. It was supported by some 150 LCA studies for more than 20 different waste streams.
The LCA results provided a benchmark level for new waste management technologies. Although not new, operational techniques
using combined pyrolysis/gasification are still fairly rare in Europe. The goal of this study is to determine the environmental
performance of the only full scale pyrolysis/gasification plant in the Netherlands and to compare it with more conventional
techniques such as incineration. The results of the study support the process of obtaining environmental permits.
Methods In this study we used an impact assessment method based on the guidelines described by the Centre of Environmental Science
(CML) of Leiden University. The functional unit is defined as treatment of 1 ton of collected hazardous waste (paint packaging
waste). Similar to the NWMP, not only normalized scores are presented but also 7 aggegated scores. All interventions from
the foreground process (land use, emissions, final waste) are derived directly from the site with the exception of emissions
to soil which were calculated. Interventions are accounted to each of the different waste streams by physical relations.
Data from background processes are taken from the IVAM LCA database 4.0 mostly originating from the Swiss ETH96 database and
adapted to the Dutch situation. Allocation was avoided by using system enlargement. The study has been peer reviewed by an
external expert.
Results and Discussion It was possible to determine an environmental performance for the pyrolysis/ gasification of paint packaging waste. The Life
Cycle Inventory was mainly hampered by the uncertainty occurred with estimated air emissions. Here several assumptions had
to be made because several waste inputs and two waste treatment installations profit from one flue gas cleaning treatment
thus making it difficult to allocate the emission values from the flue gasses.
Compared to incineration in a rotary kiln, pyrolysis/gasification of hazardous waste showed better scores for most of the
considered impact categories. Only for the impact categories biodiversity and life support the incineration option proved
favorable due to a lower land use.
Several impact categories had significant influence on the conclusions: acidification, global warming potential, human toxicity
and terrestrial ecotoxicity. The first three are related to a better energy efficiency for pyrolysis/gasification leading
to less fossil energy consumption. Terrestrial ecotoxicity in this case is related to specific emissions of mercury and chromium
(III).
A sensitivity analysis has been performed as well. It was found that the environmental performance of the gasification technique
is sensitive to the energy efficiency that can be reached as well as the choice for the avoided fossil energy source. In this
study a conservative choice for diesel oil was made whereas a choice for heavy or light fuel oil would further improve the
environmental profile.
Conclusions Gasification of hazardous waste has a better environmental performance compared to the traditional incineration in rotary
kilns mainly due to the high energy efficiency. As was determined by sensitivity analysis the differences in environmental
performance are significant. Improvement options for a better performance are a decrease of process emissions (especially
mercury) and a further improvement of the energy balance by decreasing the electricity consumption for shredders and oxygen
consumption or making more use of green electricity.
Recommendations and Perspectives Although the life cycle inventory was sufficiently complete, still some assumptions had to be made in order to establish sound
mass balances on the level of individual components and substances. The data on input of waste and output of emissions and
final waste were not compatible. It was recommended that companies put more emphasis on data storage accounted to particular
waste streams. This is even more relevant since more companies in the future are expected to include life cycle impacts in
their environmental performance. |
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Keywords: | Avoided burden hazardous waste life cycle assessment paint waste pyrolysis/gasification waste management |
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