Environmental impacts of conventional plastic and bio-based carrier bags
Environmental impacts of conventional plastic and bio-based carrier bags
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DOI：
10.1007/s11367-010-0162-9
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发表时间：
2010-03-01
影响因子：
4.8
通讯作者：
Chng, Kevin W. L.
中科院分区：
文献类型：
--
作者：
Khoo, Hsien Hui;Tan, Reginald B. H.;Chng, Kevin W. L.
生物基产品作为购物袋、包装材料和许多其他应用的使用已经越来越多地取代传统的聚合物产品。生物塑料应用的主要驱动力之一是化石燃料，特别是石油的消耗和稀缺。然而，尽管生物塑料被作为原油塑料的环保替代品引入，但其环境效益仍然值得商榷。本文旨在研究生物基材料是否是比塑料更环保的选择，并试图解释结果的基本原理。传统塑料和生物塑料购物袋的生产和处置使用生命周期评估或LCA进行了研究。选择美国的典型生物基袋（由聚羟基链烷酸酯或PHA制成）与新加坡当地生产的聚乙烯塑料（PP）袋进行比较。在LCA系统中，生产聚乙烯的原料来自中东进口原油和纳土纳气田的天然气管道。炼油厂和PP袋生产工艺位于新加坡。生物袋的生产完全在美国，并将成品运往新加坡。影响评估结果是针对全球升温潜能值、酸化和光化学臭氧形成产生的。根据新加坡年度排放清单的参数计算了归一化结果，结果表明，不同能源情景下生物袋的总体环境影响存在较大差异。当制造生物袋的能源支出由美国电力组合提供时，生产影响比PP袋的影响高出约69%。在燃煤供电的情况下，生物袋生产对生产的影响是传统塑料的五倍。当供应给生物材料生产链的能量由天然气提供时，PP袋的生命周期生产影响与生物袋相当。当在整个生命周期的生产阶段使用清洁和可再生能源（地热）时，生物袋比塑料袋环保80%。本文通过使用不同能源情景的LCA，揭示了用PHA袋替代塑料袋的环境效益（或缺点）的程度。得出的结论是，只有在整个生产过程中提供清洁能源，生物袋的生命周期生产才能被视为传统塑料袋的环保替代品。还有人强调，不应将结果视为全球代表，因为案例研究的范围仅限于新加坡。其他人对不同的可生物降解和可堆肥袋的额外工作结果各不相同。这类工作的一些复杂性在于范围包括或不包括哪些内容以及采用不同的环境影响评估方法。尽管如此，作者对这两种塑料袋的比较可以作为确定这类材料生命周期生产的主要环境负担的基础。尽管生物基产品大多被认为是替代石油基聚合物的可持续解决方案，但在大多数情况下，生产它们所需的资源和能源数量并未被考虑在内。在将生物基塑料推荐为塑料的首选之前，必须克服一些挑战。主要问题在于减少从农作物生产生物材料的生命周期中使用的能源。还应通过扩大系统边界以包括寿命终止选项来更清楚地强调这两种材料的环境益处和缺点;这在第2部分中进行（Khoo和Tan，Int J Life Cycle Assess，出版中，2010年）。
The use of bio-based products as carrier bags, packaging materials, and many other applications has been increasingly replacing conventional polymer products. One of the main driving forces of bio-plastic applications is the perceived depletion and scarcity of fossil fuels, especially petroleum. However, despite being introduced as an environmentally friendly alternative to plastics made from crude oil, the environmental benefits of bio-plastics remain debatable. This article serves to investigate whether or not bio-based materials are environmentally friendlier options compared to plastics and attempts to explain the rationale of the results.The production and disposal of both conventional plastic and bio-plastic carrier bags are investigated using life cycle assessment or LCA. A typical bio-based bag (made from polyhydroxyalkanoate or PHA) from the U.S. was selected to be compared with a locally produced polyethylene plastic (PP) bag in Singapore. In the LCA system, the raw materials for making polyethylene came from crude oil imported from Middle East and natural gas piped from Natuna gas field. The refinery and PP bag production processes are based in Singapore. Bio-bag production was entirely in the U.S., and the finished product was shipped to Singapore. The impact assessment results were generated for global warming potential, acidification, and photochemical ozone formation. Next, normalized results were calculated according to the parameters of Singapore's annual emission inventory.The total environmental impacts of bio-bags showed considerable differences under various energy scenarios. When the energy expenditures to make bio-bags are supplied by U.S. electricity mix, the production impacts are about 69% higher, compared to the impacts from PP bags. With coal-fired power supply, the production impacts from bio-bag production turned out to be about five times greater than those from conventional plastics. The life cycle production impacts of PP bags are comparable to bio-bags when the energy supplied to the bio-material production chain is supplied by natural gas. Bio-bags are 80% more environmentally friendly than plastic bags when clean and renewable energy (geothermal) is used throughout its life cycle production stages.By the use of LCA with different energy scenarios, this article sheds some light on the extent of environmental benefits (or drawbacks) of replacing plastic carrier bags with PHA bags. It was concluded that the life cycle production of bio-bags can only be considered as environmentally friendly alternatives to conventional plastic bags if clean energy sources are supplied throughout its production processes. It was also highlighted that the results should not be viewed as a global representative since the case study scope was for Singapore alone. Additional work by others on different biodegradable and compostable bags vary in results. Some of the complexities of such work lie in what is included or excluded from the scope and the adoption of different environmental impact assessment methods. Nevertheless, the authors' attempt to compare the two bags may serve as a basis for identifying the major environmental burdens of such materials' life cycle production.Although bio-based products have been mostly regarded as a sustainable solution for replacing petroleum-based polymers, in most cases, the amounts of resources and energy required to produce them have not been taken into account. Before bio-based plastics can be recommended as a preferred option to plastics, a few challenges have to be overcome. The main issue lies in reducing the energy used in the life cycle production of the bio-material from crops. The environmental benefits and drawbacks of both materials should also be more clearly highlighted by expanding the system boundary to include end-of-life options; this is carried out in part 2 (Khoo and Tan, Int J Life Cycle Assess, in press, 2010).