Which bag is best for the environment?
Peter Allan, principal consultant at Hyder Consulting, has authored numerous studies for the government on the impacts of plastic bags, including reports advising the government about which shopping bag system would be kindest to the environment. This research involved a lifecycle assessment of bag options, including energy and water use, materials consumption and litter and marine impacts across the life of a bag. The analysis found that,
- Overall, a reusable bag is a better option for the environment than bags with between one and three typical uses. “Given the popularity of the green bags, we needed to test whether reusable was better for the environment and this was comprehensively proven – but only so long as you use it repeatedly over a long period,” says Allan.
- A green bag has to be used more than 23 times before it becomes a better option than single-use bags.
- Of the range of reusable bag types tested, the most environmentally friendly option was the 100% recycledcontent PET reusable bag, closely followed by the reusable green bag.
- Calico bags are not recommended, due to the amount of water used in their production.
An assessment of single-use bags was also undertaken and the recycled HDPE bags came out best, with paper and biodegradable starch bags the least preferable for the environment. “Both biodegradable and paper bags use more energy and materials than thin plastic bags to make,” says Allan. “And there is little advantage in biodegradable and degradable bags, because most bags end up in landfill where there is no benefit to breaking down – they just create more methane and a less stable landfill site.”
Know your bags
Biodegradable: Plastic that meets the Australian Standard for biodegradability and breaks down or composts into carbon dioxide, methane, biomass and water. Generally made of corn starchor other plant material.
Degradable: Petroleum-based plastic that breaks down into small pieces when exposed to oxygen or sunlight.
HDPE (High Density Polyethylene): A lightweight plastic from which the vast majority of single-use plastic bags are made.
LDPE (Low-Density Polyethylene): Thicker plastic from which boutique bags are made.