Technical Development of Waste Sector in Sweden: Survey

MASTER’S THESIS IN ENVIRONMENTAL STRATEGIES RESEARCH
5.3.4 Assumptions and Limitations
The following assumptions have been made during the LCA model development:
• For both scenarios, transportation of waste has been ignored by assuming that
transportation distance for waste is same for both treatment plants.
• Average energy data is considered for the model assuming the similar impact on the
model for the two processes. Average data are taken for Sweden context.
• Data is based on UK’s waste treatment facilities. However, we assume that electricity that
is consumed by the systems will be quite similar with the Swedish perspective, so
electricity consumed by system is assumed to come from the Swedish national grid
(medium voltage).
• CO 2 data for P-G is assumed to be same as incineration of MSW because same waste type
with same carbon content would be combusted in the two different processes. This
assumption is made due to the lack of carbon data for P-G process.
5.3.5 Life Cycle Inventory Analysis
Life cycle inventory of the LCA model is made based primarily on the literature, report and
publications and some of the important papers are DEFRA (2004), Feo et al., (2003), Bridgwater
(1994), NSCA (2002), Halton EFW Business Case (2007), Cherubini et al., (2008), Finnveden et
al., (2000), Circeo (2009), Khoo (2009). LCA Model has been developed based on the inflowoutflow
material data that are available from the reference sources. It is important to understand
and decipher the data quality and reliability of the data while developing a comparative model. It
should be asserted that, the mountable data for P-G process is not available in Sweden since,
there are no P-G plants in large projects in Sweden. However, the data gathered for the LCA
model is quite effective for developing LCA model since data for LCA is not adversely available
for emerging technologies.
Data Analysis
In the LCA model of Pyrolysis-Gasification, the input data is takenas waste resource (1 ton
MSW), energy (electricity kWh/ton of MSW), emission (gm/T) in air, soil or waster, Energy
generation (kWh/ton of MSW) and residue (kg/ton) produced by the facilities. Most of the data
that is used for the LCA model is based on the waste composition in UK. Typical waste
composition is shown in the appendix Table A1. Both technologies require startup energy and
both generates energy from the waste treatment facilities and final residues are generated from
the processes. Table 8 shows the Inflow-outflow energy and solid waste from the processes.
Table 8: Input-output (energy and residue) in different MSW treatment processes
Input/output Pyrolysis-Gasification Incineration
Start-up energy (kWh/T) 339.3 (3) 77.8 (1)
Energy generated(kWh/T) 685 (4) 544 (4)
Solid residue (kg/T) 19.6 (3) 180 (2)
(1) Finnveden et al., (2000), (2) DEFRA (2004) , (3) Khoo(2009), (4) Circeo
(2009)
KUNGLIGA TEKNISKA HÖGSKOLAN
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