Environmental Science
Lifecycle Analysis of Biodegradable Plastics versus Conventional Plastics
Quick fact
Many biodegradable plastics only break down under specific industrial composting conditions, not in the ocean or a backyard compost pile.
Why this is interesting
You might think a 'biodegradable' plastic is always better for the planet. But is it possible that a conventional plastic could sometimes have a smaller environmental footprint?
Read the full explanation
Understanding Lifecycle Analysis of Biodegradable Plastics versus Conventional Plastics
To compare biodegradable and conventional plastics fairly, we use lifecycle analysis (LCA). Think of it as a 'cradle-to-grave' report card for a product. We track every stage: extracting raw materials, manufacturing, transportation, use, and disposal. For conventional plastics, we start with fossil fuels (oil or gas) that are extracted and refined. For biodegradable plastics, we often start with crops like corn or sugarcane that are grown, which requires land, water, and fertilizers. Manufacturing both types uses energy and creates emissions. At the end, conventional plastics can be recycled, incinerated, or sent to landfill, while biodegradable plastics are designed to be composted or degrade naturally—but only under the right conditions. LCA sums up all these impacts, like greenhouse gas emissions, water use, and pollution, to give a complete picture.
A deeper explanation
The underlying principle of LCA is to avoid 'problem shifting'—seeing a benefit in one stage while ignoring a larger cost elsewhere. Biodegradable plastics often have a lower carbon footprint at the end-of-life because they release biogenic carbon (from plants) rather than fossil carbon. However, the agricultural stage can be intensive: growing corn uses fossil fuels for tractors, fertilizers cause nitrous oxide emissions (a potent greenhouse gas), and land use can lead to deforestation. Conventional plastics, despite being fossil-based, have a very efficient, mature manufacturing process and can be recycled multiple times. The degradation conditions are crucial: under anaerobic landfill conditions, biodegradable plastics can release methane, a powerful greenhouse gas. LCA reveals that there is no universal 'better' plastic—the winner depends on the specific impacts measured, the production and disposal infrastructure, and the time horizon considered.