In a surprise finding, scientists from NTU discovered that plastic bags are more eco-friendly than paper and cotton bags.
In the study that was released on Wednesday 14 October, 5 types of bags were evaluated for their environmental impact associated with their production, distribution, transportation, waste collection, treatment and end-of-life disposal.
The finding is true for densely populated countries like Singapore where waste is eventually incinerated.
Director of residues and resource reclamation centre at the Nanyang Environment and Water Research Institute Assistant Professor Grzegorz Lisak, who led the research, said, “It is essential to evaluate the implications case by case for dealing with plastic waste.”
“In a well-structured closed metropolitan waste management system with incineration treatment, using plastic bags may be the best option that is currently available, provided that there is no significant leakage of waste into the environment,” he said.
The different types of grocery bags cause varying degrees of impact on the air and water quality. The extraction, manufacture and transport of bags via shipping cause emissions, which impact the ecosystem.
Primary reasons for the difference in impacts
The primary reason for the difference in impacts is due to the various types of raw materials, production methods, use of chemicals, location of manufacture and shipping distances, among other factors.
The negative environmental implications of CWB (Cotton woven bag) and KPB (Kraft paper bag) are dominated by the existing production processes and natural resources to obtain the finished products.
Paper bags production is a water-intensive process that involves the significant generation of liquid waste streams causing heightened emissions into agricultural soil and freshwater.
The two plastic alternatives of PNB (Polypropylene non-woven bag) and HPB (High-density polyethene plastic bag) caused far less toxicity during the production processes.
KPB caused the greatest human toxicity due to the heavy metals emissions into freshwater and volatile organic carbon emissions into the air during production, while PNB was adjudged the least.
Reusing a plastic bag four times will offset the emissions from the creation of a single-use plastic bag.
Recommendations for Singapore
In places like Singapore, where waste is incinerated, the timeline of biodegradation of paper, cotton and other biodegradable materials is irrelevant.
The study concludes that in the case of Singapore, usage of reusable plastic bags followed by HDPE plastic bags is the recommended options.
Switching to paper or cloth bags would increase the environmental footprint resulting in heightened negative effects such as global warming and eco-toxicity potentials.
It is advised to opt for reusable plastic bags that can be reused multiple times. Otherwise, single-use HDPE bags are recommended over kraft paper and biodegradable single-use options, the report said.
Minimizing the overall consumption would facilitate a substantial lowering of environmental impacts. Reusing or reprocessing the single-use HDPE bags may be an option to prevent excessive consumption of the plastic bags.