Mitigation Measures: Alternative Materials?

Hello all!

Two posts ago, I mentioned that a particular case study brought up "encouraging alternative bags" as a solution to forge greater environmental identity. In this post, I will discuss the problems of using alternative packaging materials based on research by the UK Environment Agency, which arguably displays an objectivity to adopt the best approach for the environment. Due to differing standards on the reference of LDPE and HDPE bags with the UNEP classifications, I will drop the abbreviations to avoid confusion and discuss them in terms of thickness, comparing between disposable thin bags and reusable thick bags.

Environmental Impacts of Different Carrier Bags (Source: UK Environmental Agency)

The study documented the environmental impact across its production, use and disposal. The bags considered were: a) conventional thin plastic bags, b) thicker plastic "Bags For Life", c) paper bags, d) non-woven polypropylene bags and e) cotton bags. There were five assumptions put in place in this study to derive the specific figures seen in Table 3:

1. Volume and weight of carrier bags were averaged across UK supermarkets.

2. Energy consumption was estimated by grid electricity.

3. Production waste from (a), (b) and (d) were taken to be recycled, waste from (e) was taken to be landfilled.

4. Transport distances were determined by industry experts, and were summed for the transportation of raw materials and the delivery of the finished bag to the site of retail.

5. IPCC 2007 characterisation factors determined the carbon footprint of each bag through its life cycle - summing resource use, production, transportation and end-of-life processes. A more detailed impact assessment using the CML2 Baseline method was used to calculate nine specific categorical environmental impacts, such as acidification and eutrophication.

Table 3: Characteristics and environmental burdens of each carrier bag, summarised and rounded off to 1 decimal place (Source: UK Environmental Agency).

Type of bag	Mass per bag (g)	Items per bag	Energy consumed per 1k bags (kWh)	Waste generation per 1k bags (g)	Typical total transport scenarios to UK	Carbon footprint per bag (kg CO2 eq)	End-of-life processes possible
Thin plastic bags	8.1	5.9	6.2	418.4	Lorry: 600km Sea: 16000km Rail: 270km	1.6	- Landfill - Incinerate - Mechanical recycling
Thick plastic bags	34.9	8	6.4	171.2	Lorry: 700km Sea: 21000km Rail: 560km	6.9	- Landfill - Incinerate - Mechanical recycling
Paper bags	55.2	7.4	-	-	Lorry: 1200km	5.5	- Landfill - Incinerate - Mechanical recycling - Compost
Non-woven PP bags	115.8	7.3	-	5850	Lorry: 600km Sea: 15000km Rail: 280km	21.5	- Landfill - Incinerate - Mechanical recycling
Cotton Bags	183.1	10.6	11	1800	Lorry: 680km Sea: 15000km	271.5	- Landfill - Incinerate

As seen in Table 3, the thin plastic bags have shown to demonstrate the lowest carbon footprint and the lowest environmental impacts in 8 out of 9 categories not displayed here; cotton bags, on the other hand, showed shockingly large environmental burdens. In  the consideration of every step of this life cycle in the production of one bag, it creates a carbon footprint much greater than the other carrier bags: (a) Process of growing cotton requires large land areas, year-round irrigation, and application of fertilisers and pesticides for soil cultivation, leading to large abiotic resource depletion, (b) Transportation to cotton mills with other required raw materials drove vehicle pollution, as well as the final transportation to consumers, and (c) Conversion of cotton into cotton yarn consumes large amounts of energy and water.

Assuming that 40.3% of thin plastic bags were reused as bin liners (a figure averaged across all respondents), reusable thick plastic bags, paper bags, PP bags and cotton bags had to be reused 5, 4, 14 and 173 times respectively to bring their carbon footprints below that of thin plastic bags.  These figures unfortunately greatly challenge the flow of this blog thus far by showing that alternative packaging materials may help plastic pollution, but probably not the Earth overall - arguably, there may be issues more pressing than the current concerns about aquatic biodiversity, showing greater complexity of the issues around plastic pollution. It is obvious that bags intended to last longer should use a greater amount of resources and therefore in its production cause greater environmental impacts - however, is this (exceedingly large) amplification of environmental impact justifiable?

I hereby adopt the view that our actions should be in taken for the best interests of our Earth, rather than the sole issue of plastic pollution. My purpose is not to drive pessimism, neither is it to continue encouraging single-use thin plastic bags, but to highlight that the key to reducing the overall environmental impact from packaging is to reduce our uses of plastic bags, and to reuse them for secondary applications as much as possible. Reduce, reuse, recycle. In my next post, I will be talking about the other branch of legislations: adaptation measures when plastics have already found their way into the Earth system.

See you!