在環境基準不確定模式下運用GaBi LCA軟體探討水足跡計算方法─以DVD-R光碟片製造為例

Abstract

Rapid industrialization has led to global climate change, raising attention to environmental issues. The problem of water resource shortage shown in various statistical data indicates the government should convey to consumers the idea of water management in order to retard expansion of water scarcity. “Water footprint” is an indicator for measuring scarcity of fresh water. It is a focus gradually concerned by businesses, and many of them use it as a tool for disclosing water resource and enhancing their green image. There are blue, green and grey water footprints. The former two are used to indicate water consumed by production. The last considers the amount of diluted fresh water required for maximum tolerable concentration of discharging pollutants to nearby waters; its calculation, compared to traditional water usage, must include intangible degree of water pollution in production of product or service. The location and standard of pollutants discharged to nearby waters must be acquired for conducting water footprint assessment by combining calculations of life cycle and water footprint. This is a critical point in calculating grey water footprint. However, the information cannot be easily accessed. Its range is often only within the focal firm of the business, and single water quality criterion beneficial to the business is mostly adopted for assessing the entire water footprint. The purpose of this study is to apply GaBi 5 LCA software in establishment of an integrated and operable water footprint calculation model. This model will be included in the fourteen criteria for life environment and human health protection stipulated by EPA, and its range will extend to raw material production. A DVD of cradle-to-gate will be used as an example in this study for considering the uncertainty water environment where up-stream material supplier is located, settling the situation of the supplier’s uncertain water grade, exercising analysis, excluding uncertainties, and assessing the range between optimal and worse water footprint. Current LCA software is without built-in calculation model of water footprint indicator. The Gabi 5 model developed by this study requires only input of water grade, total emission stipulated by EPA, and natural concentration of the water. We must include phases from raw material exploitation, transportation and manufacture to in-firm recycling. For a 4.7 G DVD, of which supplier is located at highest land surface water grade, the water footprint is 235.5735 kg. The method of uncertain water grade is then applied, and analysis of optimal and worse results narrows the range to 117.1178 kg.