The Environmental Impact of Glass vs Plastic Containers
26th April 2023
In this article we aim to provide a few points for consideration and discussion to help individuals make more informed choices. As in so many areas of life now, greenwashing makes angels vs demons comparisons, but the reality is not always so straightforward.
A prevailing and popular belief is that glass packaging (bottles, jars, containers) is less environmentally damaging than its plastic equivalents. Plastic has a reputation issue. Over the past few years, this reputation has become more entrenched in the public’s mind; there is a wave of bad publicity for plastic and, as a statement of their eco credentials, many individuals and organisations refuse to use plastic.
Here we will look at the 3 simple elements of the environmental impact of each material:
- Raw materials and manufacturing
1. Raw materials and manufacturing
Traditional plastics (excluding newer plant-based plastics) are refined from components of oil, a high source of CO2 emissions and other environmental impacts, and require energy for their production.
The manufacture of a plastic bottle is simple – a melting, extrusion, and moulding process. This takes place at relatively low temperatures.
For standard glass jars and bottles, raw materials (limestone, soda ash, and sand) are simpler. However, these become more complex when discussing heat resistant and laboratory products, which can include such minerals as borosilicate. These raw materials require mining operations and refining which also have a significant environmental footprint.
The complexity and energy intensity of glass product manufacturing is significantly higher. The materials are melted at 1,600 degrees and then cooled to form glass. A furnace heated by carbon-emitting fossil fuels, such as coal, oil, and natural gas, is required to generate these temperatures. Each glass container uses a significant amount more material by weight (approx. 40 times) than an equivalent plastic product; a factor that is often overlooked in the perception that glass products have a low environmental impact. Comparing 1kg of plastic against 1kg of glass may show glass to be less environmentally damaging, while the reverse may be true when comparing a single glass container against a single plastic container.
Material wasted in the manufacturing process can often be recycled internally in both production processes.
This is where the environmental footprint of glass is undeniably higher. Since the weight of a glass container is typically 40 times greater than plastic, the transportation costs in terms of CO2 and other environmental impacts (wear on lorry tyres and brakes for example) is also greater. Transport includes bringing raw materials to the container manufacturing plant, transporting finished containers for filling, and then distributing filled containers to the end user.
This is the area of least certainty due to the variability in recycling effectiveness.
Glass containers used for simple products such as food containers, are readily recycled, but the reality is that recycling rates are low. Many containers are sent to landfill sites as general waste or are stored as empty containers.
Glass is a brittle material and as a result damage/breakage in transport and during use is greater than for plastic containers. This proportionally increases the environmental footprint of the items that are delivered intact to the end user.
Pyrex/borosilicate glass, produced to withstand high temperatures is effectively non-recyclable.
Many plastics such as polystyrene, polypropylene, polyethylene, and polyester are fully and easily recyclable, and are stamped with the recycling code.
There is no straightforward answer to which material has the lower environmental impact.
Much of the real-world impact depends on how the containers are used, transported, and disposed of. Transporting goods across continents (even empty containers), and failing to recycle empty containers, can negate any theoretical benefits. The environmental impact of the container is often less significant than the impact of the contents.
Plastic containers are produced from recycled materials – either post manufacture or post-consumer. This removes much of the raw materials acquisition impact.