Comparing plastic to its popular alternatives

2023-03-22

Comparing plastic to its popular alternatives

Paper and polylactic acid (PLA) are currently the two most popular alternatives to single-use plastics. While PLA is only biodegradable in industrial composting plants, both paper and bioderived plastics like PLA and many other “plant-based” compostable alternatives could be major greenhouse gas emitters.

Taking paper as an example, study after study shows that paper bags have a much higher carbon footprint than conventional plastic shopping bags. In fact, a meta-analysis of seven life cycle assessments (LCAs) conducted by UNEP in 2020 concluded that paper bags do contribute less to the impacts of littering; however, in most cases, they are significantly worse when it comes to climate impacts, eutrophication, and acidification, compared to single-use plastic bags.

Another study that compared the use of grocery bags made from compostable plastics to traditional grocery bags made from low-density polyethylene (LDPE) found similar results. The production of compostable plastic bags and paper bags required almost 3 times the energy input needed for the production of the same number of traditional plastic bags. Similarly, these bags generated greenhouse gas emissions up to three times higher than the traditional plastic bag.

Similar trends were noticed in a limited comparative LCA study comparing single-use plastic drinking straws to its most common alternatives, the PLA straw, and the paper straw. In terms of energy demand, the single-use plastic straw had nearly half the energy demand of PLA straws and paper straws. Similarly, the PLA straw and the paper straw had a Global Warming Potential nearly three times more than the single-use plastic straw. The study also found that the use of a (reusable) metal straw would only have a significantly lower impact than plastic straws provided that the metal straws are washed using cold tap water and the standard washing time is cut to half after each use.