Technical Development of Waste Sector in Sweden: Survey

MASTER’S THESIS IN ENVIRONMENTAL STRATEGIES RESEARCH
Start up energy required for the system is taken from the average country electricity grid and
Sweden’s average energy mix is considered using the data from the SimaPro (2007) LCA. Both
processes produce electricity from the system. As a result, avoided electricity production is also
considered for the system as average country (Sweden) mix from the database. The LCA model is
developed based on emission data, assuming waste as zero burden materials. The model is thus
process specific LCA. No transportation emission is considered for the model. All the emissions
data that are taken into account for the LCA model are the average emission data; which means
this is not a plant specific emission data. Therefore, average emission data from P-G and
Incineration of MSW are used for the LCA model. Table 9 shows the emission data for two
waste treatment facilities.
Table 9: Emissions to air from waste management facilities (grams per ton of MSW)
Substances
Emissions of MWS treatment processes (g/T)
Pyrolysis-Gasification Incineration
Nitrogen oxides 780 1600
Particulates 12 38
Sulphur dioxide 52 42
Hydrogen chloride 32 58
Hydrogen fluoride 0.34 1
VOCs 11 8
Cadmium 0.0069 0.005
Nickel 0.040 0.05
Arsenic 0.060 0.005
Mercury 0.069 0.05
Dioxins and furans 4,8×10 -8 4,0×10 -7
Polychlorinated biphenyls No data 0.0001
Carbon Dioxide 10,00,000* 10,00,000
Carbon Monoxide 100 No data
DEFRA (2004) * CO2 emission assumed similar in both combustion technologies.
There is data gap for P-G process. Carbon emission is not given in the Defra report because the
process did not consider the post treatment emission after electricity generation by the syngas.
Therefore, to minimize data gap, carbon emission is assumed to be same as incineration of MSW.
This assumptions might have an impact on the results; mainly in global worming potentials but it
could still be useful while comparing the two different technologies. Since the carbon dioxide is
the content of biogenic and fossil carbon, therefore, to identify environmental burdens only
carbon dioxide is considered in the model. From the eco-invent data base, municipal solid waste
contributes 39.5% of fossil carbon, therefore, 39.5% of total carbon emission is considered for
both processes in the LCA model. Calculation of fossil carbon is shown in the appendix.
The LCA model is an attributional LCA model therefore; average country mix is used for
electricity generation as avoided product. Difference between the average data and the marginal
one is average data represents the average situation for certain process, and marginal data
represent the last number unit that produce in the system. For example, in extreme winter, during
high heat demand, Sweden generates heat from coal or diesel power plant. Usually, Sweden does
KUNGLIGA TEKNISKA HÖGSKOLAN
44 | Page