Are biodegradable plastics necessary?

In the timeless film "It's A Wonderful Life" by Frank Capra, Sam Wainwright urges George Bailey to dive into the promising realm of plastics. "This is the next big thing after radio," Sam assures George, "and I'm giving you a chance to get in early."

One can only speculate how Sam would have reacted to biodegradable plastics or how he would have presented the idea to George when researchers found a way to create plant-based polyesters in the late 1980s. Perhaps he would have exclaimed, "This is the next big thing since the PC." And while the concept was groundbreaking, like many so-called "miracle" solutions, the actual results often fell short of expectations.

To begin, let's revisit the potential of polylactic acid (PLA), a polymer sourced from plant sugars. When Cargill, a major player in agriculture, introduced PLA, it highlighted two key advantages. First, the raw material for PLA is corn, a crop harvested in vast quantities annually. This means PLA originates from a renewable resource, unlike conventional plastic, which is derived from fossil fuels during oil refining. Second, PLA decomposes into water and carbon dioxide when exposed to bacteria, making it biodegradable and far more eco-friendly.

Interestingly, the production of PLA has proven to be more sustainable than traditional plastic in terms of fossil fuel usage. As a bio-based polymer, PLA doesn't rely on oil as a raw material. In contrast, standard plastic packaging consumes 200,000 barrels of oil daily in the U.S. [source: Royte]. Additionally, PLA production demands less energy, which typically comes from coal-fired power plants. Estimates suggest PLA manufacturing uses 65% less energy than conventional plastics [source: Royte], resulting in reduced greenhouse gas emissions and a smaller carbon footprint.

However, PLA packaging requires specific conditions to decompose effectively. The bacteria responsible for breaking it down need an oxygen-free environment and sustained temperatures of at least 140°F (60°C) for 10 consecutive days. Under these conditions, PLA biodegrades in under 90 days. Unfortunately, neither landfills nor typical home composting setups can provide such an environment. In these settings, PLA persists as long as petroleum-based plastics—500 years or more. Additionally, PLA poses challenges at recycling centers, as it cannot be mixed with traditional plastics and is treated as a contaminant.

Oxo-degradable plastic, another biodegradable option, also has limitations. While it can be recycled alongside regular plastic waste, it is derived from oil or natural gas byproducts, meaning it still depends on nonrenewable resources. As the name implies, it decomposes best in oxygen-rich environments, such as large industrial composting facilities, which are not available in standard landfills or backyard composts.

Given the current state of biodegradable plastics, are they truly necessary? In their present forms, perhaps not. However, this doesn't rule out future advancements. In the interim, recycling systems could be adjusted to handle corn-based biodegradable plastics, potentially adopting a three-bin system: one for traditional plastics, one for biodegradable plastics destined for commercial composting, and one for miscellaneous waste.

While this might not appear thrilling to ambitious entrepreneurs like Sam Wainwright, who seek rapid wealth, it represents a positive move forward.