Life Cycle Assessments of Energy From Solid Waste (PDF)

In this study, electricity generated from hard coal is chosen as the marginal technology. The
data for electricity produced from hard coal is from Frees and Weidema (1998), these data are
further described in section 5.7. As discussed above other alternatives may also be considered
and this should preferably be done in a continuation of this study.
3.3 Heat production
3.3.1 Heat source
In this study heat produced when handling waste by incineration, anaerobic digestion or
landfilling is credited the waste treatment option by subtracting heat produced from another
source (avoided product systems are explained in chapter 2). Heat produced through the waste
management is assumed to be transferred to the district heating system. The 1998 composition
of energy carriers contributing to the 44.1 TWh heat delivered by the district heating facilities
in Sweden are shown in Table 3.1. As can be seen the major contribution is from forest fuels,
this amount has increased by four times since 1990. The main forest fuels are forest felling
residues and by-products from the forest industries (Energimyndigheten 1999).
Table 3.1 Energy supplied from different sources to the district heating system in Sweden during 1998
(Energimyndigheten 1999).
Fuel
Energy supply (TWh)
Forest fuels 14.7
Heat pumps 7.4
Oil 5.5
Waste 5.0
Surplus heat etc 3.6
Coal 3.4
Natural gas and liquefied petroleum gas 3.3
Peat 3.1
Other biofuels 2.9
Electric boilers 1.8
In this study, the ideal data would be the long-term base load marginal as discussed in 2.1.2
and 2.3.2. Which source this is may be discussed. One key assumption is whether the market
for district heating has an up- or down-going trend. If there is an increasing use, the most
preferred alternative would be on the marginal and if the use is decreasing the least preferred
alternative would instead be defined as the marginal technology. Increasing the districtheating
share of the total heating may be considered to be in line with aiming towards
sustainable energy use. Transforming systems where electricity is used for heating buildings
to being supplied with district heating is one example.
Assuming an upward trend, the discussion may be that biofuels are preferred from a
greenhouse effect perspective and that the availability in Sweden is comparably high. On the
other hand, on the global market, biomass will become increasingly scarce and also in
Sweden different uses for biomass compete for the available resources.
Incineration of waste is another possible marginal heat producing technology if other options
of handling this waste is not considered to be significantly more preferable and the amount of
combustible waste is sufficient. The waste may be household waste or waste from other
sectors, e.g. the building sector. It has been noted that other types of waste is the competing
heat source in Sweden today (ÅF-IPK 1998). This is because the current waste incineration
capacity in Sweden is limited. If a choice leads to increased or decreased incineration of a
specific waste fraction, this is likely to decrease or increase the incineration of other waste
fractions and an increase or decrease of landfilling of this fraction resulting in a constant use
31