Packaging is both an essential function and something that can add significant value to a brand. In recent years, there have been many headlines about the environmental impacts of packaging, in particular relating to plastic and paper bags. Smith Bateson, as a responsible company, has commissioned an independent study into the life-cycle assessment of carrier bags. The key issues are summarised below, so that buyers are aware of the real facts. The aim is not to promote one type of bag over another, rather to communicate the evidence. The study shows that some typical perceptions about the environmental impacts of plastic bags compared with paper bags may be inaccurate and misleading.
Plastic bags consume 71% less energy during their production than paper bags
Plastic bags generate 39% less greenhouse gas emissions than un-composted paper bags and 68% less greenhouse gas emissions than composted paper bags.
Paper bags are between 6 and 10 times heavier than lightweight plastic bags and, consequently, require more transport,
along with its associated costs.
Plastic bags consume less than 6% of the water needed to make paper bags. It takes 2.5 m3 of water to produce 1000 paper bags and 0.13 m3 of water to produce 1000 plastic bags.
Using paper bags generates almost five times more solid waste than using plastic bags.
Polyethylene (plastic) bags contribute 74–80% less solid waste than paper bags at zero recycling. Plastic bags continue to contribute less solid waste than paper bags at all recycling rates.
At a zero recycling rate, plastic bags contribute over 90% less waterborne waste than paper bags. This percent difference actually increases as the recycling rate for both types of bag increases.
The landfill volume occupied by plastic bags is 70–80% less than the volume occupied by paper bags.
Although paper and certain plastics may be biodegradable or compostable in specially designed industrial facilities, the evidence indicates that this feature may be of little value in the effort to reduce waste. Current research shows that in modern landfills, paper does not degrade or break down
at a substantially faster rate than plastic. Owing to the lack of water, light, oxygen and other important elements necessary for biodegradation, nothing completely degrades in modern landfills.
The use of biodegradable bags would offer benefits in litter persistence but would not deliver significant resource use gains and would not be compatible with plastic bag recycling.
Although the risk of litter may be the same for plastic and paper bags, plastic bags have a greater potential for adverse environmental impact when not reused, recycled or sent to landfill, particularly in the marine environment.
Recycling and composting generally produce only a small reduction in global warming potential and abiotic depletion.
The research summarised here supports the view, which is counterintuitive for many, that paper bags have a greater environmental impact during their manufacture and use than plastic bags.
The evidence does not support the conventional wisdom that paper bags are a more environmentally sustainable alternative to plastic bags.
Paper bags have a greater adverse impact than plastic bags for most of the environmental issues considered. Areas where paper bags score particularly badly include water consumption; acidification, which can have negative effects on human health, sensitive ecosystems, forest decline and lakes); and the eutrophication of water bodies, which can lead to the growth of algae and the depletion of oxygen.
Compared with lightweight HDPE bags and reusable low-density polyethylene (LDPE) bags, single-use paper bags perform worse across all environmental indicators (energy consumption, water consumption, climate change, acidification, air quality, eutrophication, waste and litter) except risk of litter.
Environmental gains from reusable bags are closely linked to the life expectancy of the bags, their weight-to-capacity ratio and their final destination – low litter, high recycle.
After four or more uses, reusable plastic bags are superior to all types of disposable bags (paper, polyethylene and compostable plastic) across all significant environmental indicators.
Heavyweight, reusable plastic bags (so-called bags for life) are more sustainable than all types of lightweight plastic carrier bags if used four times or more. They give the greatest environmental benefits over the full life cycle.
Paper bags perform worse in all indicators except risk of litter. Reusable bags perform best, provided that they are reused at least four times.
Whatever type of bag is used, the key to reducing its impacts is to reuse it as many times as possible. Where reuse for shopping is not practicable, other options, e.g., to replace bin liners, are beneficial.
The reuse of conventional HDPE and other lightweight carrier bags for shopping and/or as bin liners is pivotal to their environmental performance. Reuse as bin liners produces greater benefits than recycling bags.
A substantial shift from single-use disposable bags to more durable reusable bags would deliver an environmental gain over the full life cycle of the packaging.
Reusable heavy-duty plastic bags that can combine low resource use, longevity and recycling come out as most sustainable.
Paper, LDPE, non-woven polypropylene and cotton bags should be reused at least 3, 4, 11 and 131 times respectively to ensure that they have lower global warming potential than conventional HDPE carrier bags that are not reused.
The key issue, however, is not whether to use paper or plastic, but how the efficiency of carrier bags can be maximised through ways to reduce, reuse and recycle them, in that order. By putting more items in fewer bags, avoiding double bagging, switching to durable bags and reusing and recycling disposable bags, significant reductions in material and non-renewable energy consumption, pollution, solid waste, greenhouse gas emissions and litter will occur.
These figures are summarised from an independent carrier bag lifecycle assessment report.
Click here to view the full report.