La construcción del “problema” de la corrupción

The emissions to air of environmentally harmful gases resulting from the use of energy are significantly affected by the type of energy used. No emissions to air are assumed involved when using hydroelectricity, while the combustion of fossil fuels has large regional and global effects on the environment. Examples of such effects are global warming, acidification and depletion of the ozone layer.

7.2.1 Energy use in Norway, Europe and the world

Norway is less dependent on the use of fossil fuels as compared to most other countries. In 1993, fossil fuels represented 43% of the total energy consumption in Norway14, while hydroelectric power represented 51%, and biomass about 5% (NOS C183, 1994). In contrast, fossil fuels represented almost 90% of the total energy consumption in Europe in 1993 (Euromonitor, 1995), and about 75% of the total energy consumption in the world in 1989 (Brown et al., 1991). Because of the large share of hydroelectric power

used, the use of one energy unit in Norway result in less emissions to air, as compared to the use of one energy unit in Europe and the world.

Electricity represented about 80% of the total energy consumption in the Norwegian residential sector in 1993 (Djupskås and Nesbakken, 1995). Consequently, the direct emission reductions resulting from energy saving measures performed in the residential sector will be small. It may therefore be argued that the environmental benefit of

performing additional thermal insulation measures in the Norwegian dwelling stock is limited.

However, electric power can be transmitted over long distances and does not have to be consumed in the district or in the country where it is produced. Electricity can therefore be regarded as a universal commodity. Moreover, electricity is a highly flexible energy source which can be used for a range of purposes. Hence, there are no reason to restrict saved electric power from Norwegian houses to be used in the Norwegian residential sector only. Instead, large environmental benefits may be obtained if saved energy in houses substitutes the use of energy in other sectors or in other countries.

7.2.3 Payback periods for energy consumption and emissions to air for

different ways of accounting energy savings

In Chapter 6 it is shown that the time periods (payback) are short before the total energy consumption during the production stage is paid back by the savings during the operation stage. For most emissions to air, in contrast, the payback periods are long as a result of the large share of hydroelectricity assumed used in the case study house (see Table 6.11). However, the estimated payback periods for emissions to air are notably reduced if it is assumed that saved energy in the house result in reduced use of fossil fuels in other sectors.

In the following, a principle of substitution is used, where the total energy consumption in Norway and Europe are assumed to be reduced by the same quantity of energy as saved in the case study house. The corresponding estimated emission reductions are based on the emissions to air associated with the average use of energy in Norway and Europe. The house taken as basis for the case study in Chapter 6 is used as reference. The emission reductions resulting from energy savings in this house is estimated on the basis of 69% electric heating, 24% oil-heating and 7% wood-firing. These shares are average heating shares for detached blocks of flats constructed between 1956 and 1970.

Table 7.1 shows key numbers on the average emissions to air per MWh used for the reference alternative and for the Norwegian and European alternatives. For the reference alternative, the average CO₂ emissions per MWh used are 64 kg, as compared to 142 kg and 227 kg, respectively, for the Norwegian and European alternatives. The emissions of SO₂ and NO_x per MWh used are also much lower for the reference alternative than for the Norwegian and European alternatives. The emissions of PM, however, are higher for the reference alternative than for the Norwegian alternative, and only slightly lower than

alternative are caused by wood-firing which represent 7% of the heating requirement of the house. In total, the average use of energy in Norway generates less emissions to air as compared to the average use of energy in Europe.

In Chapter 6, the total energy consumption during production of the 150 mm additional thermal insulation alternative was estimated to be 63 MWh. The associated emissions to air were estimated to be 20 tons of CO₂, 44 kg of SO₂, 54 kg of NO_x and 23 kg of PM (see Table 6.5). The energy saving was estimated to be 67 MWh per year (see Table 6.8). Table 7.2 shows that the estimated payback periods for emissions to air of CO₂, SO₂ and NO_x are significantly shorter for the Norwegian and European alternatives, as compared to the reference alternative. The payback period for emissions to air of PM is slightly longer for the Norwegian alternative and slightly shorter for the European alternative. The estimated payback periods based on the Norwegian emission alternative range from 0.7 year (NO_x) to 3.6 years (SO₂), while the payback periods calculated on basis of the European emission alternative range from 0.6 years (SO₂) to 1.5 years (PM).

Table 7.1. Estimated emissions to air of CO₂, SO₂, NO_x and PM per MWh used for three different alternatives. The reference alternative is based on the emissions to air resulting from the energy consumption for space heating of the case study house, while the

Norwegian and European emission alternatives are based on the average emissions to air resulting from one energy unit used in Norway and Europe, respectively.

Alternative Energy Total emissions to air Emissions to air per

consumption CO₂ SO₂ NO_x PM CO₂ SO₂ NO_x PM TWh Million tons 1000 tons 1000 tons 1000 tons kg/MWh g/MWh g/MWh g/MWh Reference* 64 62 61 156 Norwegian** 240 34 37 220 21 142 154 918 88 European*** 33 943 7 695 37 242 20 991 7 859 227 1 097 618 232

* Detached block of flats assumed having 69% electric heating, 24% oil-heating and 7% wood-firing. ** Data, referring to 1992, are based on NOS C161 (1994). Ocean transport is not included.

*** Data on energy consumption refer to 1993, data on emissions to air refer to 1990 and 1991. Europe includes Belgium, Denmark, France, Germany (East and West), Greece, Ireland, Italy, Netherlands, Portugal, Spain, United Kingdom, Austria, Finland, Iceland, Norway, Sweden, Switzerland, Albania, Bulgaria, Czech/Slovak Republics, Hungary, Poland, Romania, USSR (former) and Yugoslavia (former). Based on Euromonitor (1995).

7.2.3 Payback periods for an alternative construction

The payback periods shown in Table 7.2 are estimated for an additional thermal

insulation measure consisting of 150 mm high-density mineral wool (110 to 135 kg/m3₎

and 20 mm plaster as weather coating. For this construction, the layer of high-density mineral wool is the main contributor to the total energy consumption and emissions to air during the production stage (See Table 6.5). Since energy consumption and emissions to air during the production of mineral wool are proportional to the density, notable

reductions in energy consumption and emissions to air may be obtained by using low- density mineral wool as thermal insulation layer instead of high-density mineral wool. To exemplify this, payback periods are estimated for the energy consumption and emissions to air for an alternative construction consisting of 150 mm low-density rock wool (30 kg/m3) and wooden cladding. As a simplification, it is assumed that this

insulation alternative gives the same U-value improvement of the walls as the alternative with high-density mineral wool and plastering. The consumption of low-density mineral wool and timber is estimated to be 148.4 m3 _{and 29.7 m3, respectively, while other}

materials like steel (nails) and cardboard (wind proofing) are neglected. Data on energy consumption and emissions to air of CO₂, SO₂, NO_x and PM during production of low- density mineral wool and timber are taken from Fossdal (1995). All other assumptions are the same as for the case study house (see Chapter 6).

Table 7.3 shows the estimated energy consumption and emissions to air during the production of the low-density mineral wool alternative, and the yearly energy saving and emission reductions during the operation stage. The emission reductions are estimated as for the case study house (69% electric heating, 24% oil-heating and 7% wood-firing; see Table 6.8). From Table 7.3 it can be seen that the estimated payback periods for the low- density alternative are much shorter compared to the high-density mineral wool

construction (Table 7.2). The energy consumption during the production stage is paid

Table 7.2. Number of years (payback periods) before the total energy consumption and emissions to air during the production stage is paid back by the energy savings and emission reductions during the operation stage. Three alternative ways of estimating the emission reductions resulting from saved energy are given; a reference alternative based on 69% electric heating, 24% oil-heating and 7% wood-firing in the case study house, and two alternatives based on the average emissions to air per energy unit used in Norway and Europe. Energy consumption and emissions during the removal stage are neglected.

Alternative Payback periods (years)

Energy CO₂ SO₂ NO_x PM

Reference alternative 0.9 4.7 10.5 13.2 2.2

Norwegian average emissions to air 0.9 1.7 3.6 0.7 3.2

back after 0.4 years, and the SO₂ emissions after 3.3 years. The corresponding payback periods for the high-density construction are 0.9 years and 10.5 years, respectively.

The short payback periods calculated for the high-density insulation alternative (Table 7.2), especially when considering the effect of substituting fossil fuel use, and the even shorter payback periods calculated for the low-density insulation alternative (Table 7.3), indicate that additional thermal insulation measures generally are very favourable in a life cycle perspective with respect to total energy consumption and emissions to air.

7.3 IMPORTANCE OF ENERGY PRICES AND EMISSION TAXES