I

Basket of goods

Reference scenario

Resources Waste input

Basket of goods

Figure 13.19. Various scenarios to fill the basket of goods [10].

Recycling scenario

Reference scenario

Recycling scenario

Reference scenario

Figure 13.20. Recycling scenario and complementary process route [10].

The net difference between collecting and sorting waste plastics on the one hand and collecting and landfilling them as a component of household waste

The choice of the complementary process and its efficiency are certainly of utmost importance, which is criticized by some. Examples for this are given later in the results.

Ecological data have been collected for all the products in this project as well as for all process steps required (see Table 13.1). First a "life-cycle inventory" was established for all relevant ecological inputs. In a second step a data assessment was carried out aggregating individual data into 10 environmental categories such as anthropogenic green house effect, eutrophication potential, and the like (Fig. 13.21).

Only five categories that were found relevant will be dealt with in this chapter. The other categories such as ozone depletion, mineral resources, total water, or total mass of radioactivity did not show any or only very little differences between different routes of filling the basket of goods.

The report, discussed here, was criticized by the expert panel for not having included an evaluation of the influence on human toxicity. This evaluation was considered in the beginning of the study, but it soon was realized that very little data existed or were available. A second reason for excluding it was the nonex-istence of a scientific approved and accepted way of assessing these category at the time of the study. Meanwhile, some proposals exist [11].

Table 13.1 Ecological Inputs and Outputs

Environmental Impact Categories

Resources (input factors) Coal

Crude oil Natural gas Minerals

Hydroelectric power Wood

Water appropriated Air appropriated Secondary raw materials Sum of resources Inventory analysis Emissions (output factors) Solid waste Airborne emissions Waterborne emissions Water returned Air returned

Energy equivalent of nonrenewable energy resources

Energy equivalent of renewable energy resources

Total mass of mineral resources Total water appropriated

Mass of household-type solid waste Mass of hazardous solid waste (from power generation) and other hazardous waste

Material flows contributing to the anthropogenic greenhouse effect Material flows contributing to catalytic stratospheric ozone depletion Material flows with acidification potential Material flows with eutrophication potential

Sum of emissions

Resources

- Energy

- Minerals

- Water

Resource conservation

Anthropogenic greenhouse effect (GWP)

Stratospheric ozone depletion (ODP)

Resource conservation

Anthropogenic greenhouse effect (GWP)

Stratospheric ozone depletion (ODP)

Resources

- Energy

- Minerals

- Water

Products

¿arc^ Eutrophication

Figure 13.21. LCA — data assessment.

Solid waste

- household

- hazardous

Products

¿arc^ Eutrophication

Figure 13.21. LCA — data assessment.

Solid waste

- household

- hazardous

Furthermore, recycling routes are categorized as follows:

• Recycling routes that are able to use any kind of plastic waste—certainly after some kind of pretreatment such as agglomeration or dehalogenation, for instance. They are called universal processes. A second prerequisite for this definition is the existence of a very large market for the resulting products in comparison to the recycled amount.

• In mechanical recycling, which requires rather homogeneous plastic waste. Reality has demonstrated, that only 20-30% of household waste can be separated, purified, and worked up for mechanical recycling for economical reasons and due to insufficient market potential. This practical finding corresponds with the fact that more than 60% of plastics packaging weigh less than 10 g. The smaller the item the more uneconomical the sorting process — manually or technically.

The difference in waste input — required for technical reasons — certainly affects the environmental impacts so that only scenarios involving identical waste input can be subjected to a quantitative comparison. In practice, however, the differences in the investigated input mix are sufficiently minor (higher or lower polyolefin content) to permit qualitative comparison. The different waste input categories are indicated by separator lines in the bar charts in Figures 13.22 and 13.23.

INFLUENCE ON ENERGY DEMAND AND GLOBAL WARMING POTENTIAL The most relevant differences between different routes are found for saving in energy consumption or for energy-dependent causes such as global warming potential

Energy equivalent of resources [MJ/kg]

Energy equivalent of resources [MJ/kg]

Figure 13.22. Saving of energy resources of different routes of recycling in comparison to landfill (MJ/kg of recycled plastic) (LER = life expectancy ratio) [10].

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