Glass half full
Plastic has a considerable carbon footprint, in its creation and as it breaks down, but its alternative, glass, also has a cost to bear.
Plastic pollution may seem separate from climate change, but they are connected. Most plastic begins life as oil or fracked gas, and greenhouse gases are emitted to extract, transport and refine the fuel, manufacture plastic and manage plastic waste. The Centre for International Environmental Law, in the United States, estimates that annual emissions from plastic by 2030 could be equivalent to those from 295 new coal-fired power plants. That would gobble up a significant chunk of the remaining carbon we can emit before committing Earth to more than 1.5°C of warming.
Plastic releases greenhouse gases as it degrades into microplastics. In the ocean, it contaminates plankton, and lab studies suggest this undermines plankton’s ability to reproduce and photosynthesise. “This is deeply concerning because plankton removes huge amounts of carbon from the atmosphere,” says Olga Pantos, a senior scientist with the Institute of Environmental Science and Research (ESR).
To avoid plastic, many people seek glass packaging. But glass is made in energy-hungry furnaces that melt sand, so is it any better from a climate perspective?
Sarah McLaren is professor of lifecycle management at Massey University and directs the New Zealand Life Cycle Management Centre. She specialises in life-cycle assessments that compare the environmental impacts of different systems. These assessments reveal a higher carbon footprint for glass than plastic, largely because more of it is used to package each item and it is heavy to transport.
The end-of-life phase is harder to estimate because it depends how much is recycled. Globally, this figure is about 9%, and National Institute of Water and Atmospheric Research (Niwa) researchers find a lot of recyclable plastic in streams. Recycled glass and plastic have lower carbon footprints than their virgin counterparts. But although glass can be recycled infinitely, plastic can’t. “People often think that plastic is okay as long as it’s recycled, but often it’s downcycled to a lower grade. But there are only so many lower-grade uses in the economy. Do we really want to go down that route?” says McLaren.
The carbon footprint of plastic waste that ends up as litter in the environment has not been included in life-cycle assessments, she says, although a working group is addressing that gap.
She advocates thinking beyond comparing one packaging material with another. “For example, the wine industry realised that a lot of their impact came from energy for distribution, so they started bulk delivery overseas that is packaged on arrival. Reuse is even better – then a glass bottle can really start looking like a good alternative, from a carbon-footprint perspective.”
Grant Northcott, a consultant environmental chemist, wants people to know that glass, when melted for recycling, is non-toxic. “Plastic has still got its chemical additives.”
Usually, the life cycle of the product inside the packaging has higher environmental effects than does the packaging, so the best packaging solution enables a product to reach the consumer without damage or degradation and minimises environmental impacts, including microplastics.