Assessment of Energy Consumption

As a preliminary approach, calculating the demand in nonrenewable primary energy per FU constitutes a useful and effective way for identifying processes that are likely responsible for most emissions and extractions. The primary nonrenew-able energy flows are technically part of the impact assessment and not part of the inventory. Strictly speaking, the inventory results related to energy consist only of the mineral ore extractions needed for the energy carriers (petroleum, coal, gas, uranium, wood, etc.). These ore extractions are then multiplied by calorific values to obtain nonrenewable primary energy flows. Most analyses, however, consider the nonrenewable primary energy consumption in this early LCA phase, because it is often correlated to many inventory items and is thus an excellent way to test the magnitudes and validity of the inventory results.

Aluminum, primary,

liquid 1 kg Natural gas in ground (525 dm³)

Brown coal in ground (1.20 kg)

Crude oil in ground (1.18 kg) Uranium in ground (58.3 mg) Aluminum in ground, 24% in bauxite, 11% in crude ore (1.16 kg)

Particulates, < 2.5 μm (4.95 g) HFC-116 (28.2 mg)

Methane, biogenic (51.7 mg) Carbon dioxide, fossil (9.40 kg)

Sulfur dioxide (38.0 g) Nitrogen oxides (19.6 g) Hydrogen fluoride (676 mg) Arsenic, ion (44.0 mg)

Hard coal in ground (2.01 kg)

Occupation, forest, intensive (0.101 m²y)

Arsenic (1.88 mg)

Carbon monoxide, biogenic (91.8 g) Benzo[a]pyrene (2.74 mg)

PAH (88.7 mg) CFC-14 (252 mg) Dioxins (1.74 ng)

FIGURE 4.1 Aggregated inventory of extractions and emissions for liquid primary alumi-num at plant, taken from ecoinvent 2.2. Elementary flows from and to the environment are shown in italics.

Inventory Analysis of Emissions and Extractions 51

Primary energy is defined as the energy contained in the energy carriers at the point of extraction from the environment. It is the sum of the final energy purchased by the consumer and the upstream energy usage for extraction, preparation, and distribution. The ratio between final energy and primary energy defines the energy efficiency of the supply chain.

A part of the primary energy is nonrenewable, which means that the basic resource of this energy is nonreplaceable or is replaced very slowly through natural processes.

Nonrenewable primary energy generally stems from fossil fuels (petroleum, coal, natural gas) and uranium. This energy is eventually dissipated to the environment in the form of unusable heat. Energy from sources such as hydroelectric dams, ther-mal solar collectors and photovoltaic cells, wind power, or wood combustion is all technically renewable but requires the use of nonrenewable primary energy for the infrastructure manufacturing and use.

The nonrenewable primary energy demand and CO₂ emissions for differ-ent materials and processes are calculated and listed in the ecoinvdiffer-ent database (Section  4.3.2). Table  4.1 presents some typical values for a commonly used set of processes and materials, showing that the nonrenewable primary energy con-sumption and emissions from electricity vary substantially by country of origin;

the consumer use of 1 kWh of Swiss electricity requires 7.9 MJ of nonrenewable primary energy, compared with 10.5 MJ needed for a European electricity mix and 12.1 MJ for a U.S. electricity mix. The difference is even more noticeable for CO₂, with a variation of more than a factor of four (from 0.11 kg_CO2/kWh for Switzerland to 0.49  kg_CO2/kWh for Europe and 0.71  kg_CO2/kWh for the United States). This difference is due to the composition of the Swiss electricity mix, 40% of which is nuclear and 57% hydroelectric, a renewable energy source that needs minimal non-renewable energy for infrastructure. If the level of energy consumption varies by scenario, the choice of energy source can strongly influence the results of a study.

However, the variation in nonrenewable primary energy requirements among dif-ferent databases may be larger than the variation among regions within the same database. So, for the comparative purposes of an LCA, where consistent data sets are a priority, it is sometimes better to adapt high-quality data to another geographi-cal context rather than compare electricity mixes from the appropriate regions but different databases.

The values provided in Table  4.1 must be interpreted with care and generally cannot simply be compared only on a per unit mass basis. For example, aluminum requires seven times more energy and emits seven times more CO₂ per unit mass than steel. However, these materials should be compared by function rather than mass and different amounts may be needed depending on the function. It is therefore necessary to relate all energy consumptions and CO₂ emissions back to the FU for the considered application (example in Table 4.2).

Appendix III provides the nonrenewable primary energy consumption and CO₂ emissions for a large number of materials and processes. System reference flows can be identified based on Section 3.3 concepts, and then Appendix III data may be used for a preliminary evaluation of the principal contributions to the total energy demand.

52 Environmental Life Cycle Assessment

TABLE 4.1

Nonrenewable Primary Energy and CO₂ for Different Types of Energy Carriers, Materials

Nonrenewable Primary Energy (MJ per unit)

CO₂ (kg per unit)

g_CO2/MJ ratio Energy Carriers

1 kWh electricity (Europe) 10.5 0.49 47

1 kWh electricity (United States) 12.1 0.71 59

1 kWh electricity (Japan) 11.5 0.53 46

1 kWh electricity (Switzerland) 7.9 0.11 13

1 kWh electricity (China) 10.4 0.98 94

1 L gasoline (no combustion)^a 42.9 0.49 11

1 L gasoline (with combustion) 42.9 2.88 65

1 kg light oil (42.7 MJ final) 56.8 3.71 65

Transportation

1000 km-kg transportation by 16–32-ton lorry

2.6 0.15 58

1 person-km by train (Intercity) 0.98 0.06 58

1 person-km by airplane (European flight)

3.28 0.19 60

1 person-km by car 3.0 0.17 57

Material

1 kg steel, low alloy 27.4 1.63 59

1 kg primary aluminum 160.4 9.55 60

1 kg recycled aluminum 22.4 1.32 59

1 m³ concrete 1,381 257 186

1 kg copper 31.2 1.86 60

1 m³ water 5.55 0.30 54

1 kg newsprint paper 24.3 1.22 50

1 kg polyethylene HDPE^a 76.4 1.56 20

1 kg glass 11.5 0.63 55

End of Life

1 kg landfilled steel 0.197 0.00657 33

1 kg landfilled aluminum 0.521 0.02010 39

1 kg incinerated municipal solid waste (MSW)

0.43 0.50 1,161

1 kg incinerated polypropylene 0.209 2.53 12,060

Note: Figures are extracted from ecoinvent 2.2 and aggregated over the entire life cycle.

a Includes the gasoline extraction and refinement processes, but does not include combustion.

Inventory Analysis of Emissions and Extractions 53

TABLE 4.2

Nonrenewable Primary Energy for an Output of 800 lm during 5000 h

LCA Stage

Reference Flows and Main Intermediary Flows

bulbs/FU = 0.075 kg/FU

Copper: 31.2 MJ/kg 0.075 kg/FU

× 31.2 KJ/kg

= 2.34 MJ/FU

Manufacturing 5 bulbs/FU 0.38 MJ/bulb 1.90 MJ/FU

Packaging 5 bulbs/FU × 0.01 kg/bulb

= 0.05 kg/FU

Paper: 24.3 MJ/kg 1.2 MJ/FU Transportation 1000 km × 5 bulbs/FU

× (0.035 kg/bulb bulbs/FU = 300 kWh/FU

Electricity (U.S.):

12.1 MJ/kWh

3633 MJ/FU Waste disposal 5 bulbs/FU × (0.035 kg/bulb

+ 0.01 kg/bulb)

0.06 kg electronics/FU Electronics: 896 MJ/kg 53.7 MJ/FU

0.1 kg glass/FU Glass: 11.5 MJ/kg 1.15 MJ/FU

Manufacturing 1 bulb/FU 10.6 MJ/bulb 10.6 MJ/FU

Packaging 0.04 kg/FU Paper: 24.3 MJ/kg 1.0 MJ/FU

Transport 1000 km × (0.16

54 Environmental Life Cycle Assessment

Im Dokument ENVIRONMENTAL LIFE CYCLE ASSESSMENT (Seite 80-84)