Breaking down biodegradability

The past century’s scientific advancements have improved the quality of life for people worldwide. Material living conditions have been made far more comfortable with greater access to affordable and durable essential items. The global population will soon reach 8 billion, a phenomenon only made possible by new pharmaceuticals and agricultural chemicals. Technology has led to economic growth and provided greater access to education.

But every coin has two sides.

It’s becoming increasingly clear that we’re facing a global garbage problem. Even the most remote environments are contaminated with the synthetic materials we rely upon. Plastics, pesticides, and household chemicals are some of the most common culprits, strewn across Arctic tundra, suspended throughout the atmosphere, and sluicing down drainpipes near and far to meet the global ocean.

Now, the next wave of progress is in the name of sustainability. It’s crucial to continue improving quality of life, especially for those who continue to live in insecure situations, but not at the planet’s expense. Moving forward, what we take from the Earth must be renewable, recyclable, or assimilable into the natural world at the end of its use.

These issues have a lot of people talking trash – literally. We’ve grown to rely upon durable synthetics in our daily lives, yet they persist in the environment for centuries, if not millennia, after they’re thrown away. How can we reduce our consumption? How can we reuse, repurpose, or repair products to extend their lifespan? How can we effectively recycle an item’s components? How can we innovate materials that will break down into their most basic molecular building blocks when they no longer serve their intended function?

At the end of this line of questioning, a proposed answer is biodegradability.

“Water and air, the two essential fluids on which all life depends, have become global garbage cans.” – Jacques Yves Cousteau

Biodegradation is the natural breakdown of materials by microorganisms, such as bacteria and fungi. The process occurs in three steps:

  1. Biodeterioration, where microorganisms weaken the object’s mechanical structure,
  2. Biofragmentation, where microorganisms break down the material’s molecular structure through a series of complex chemical reactions,
  3. Assimilation, where the material’s basic molecular building blocks are incorporated into the environment as carbon dioxide, water, or biomass (organic molecules used to create new cells).

By definition, almost all materials biodegrade, the pivotal element being time. Plant matter may biodegrade within days, while ceramics and plastics may take thousands of years to complete the process. Plastics and many other fossil-fuel-derived chemicals likely take hundreds of years to fully decompose, although some varieties are too new for researchers to be sure. They may end up persisting significantly longer in the environment.

To counter these issues, scientists are developing biodegradable plastics. Often, these new materials are chemically derived from plant-based feedstocks, which reduces dependency on non-renewable fossil fuels. New biodegradable products steadily appear across the market, boasting their reduced environmental impact. At least, in theory.

Biodegradability is far more complex than adding a word to a product’s label. To earn the right to denote a product as biodegradable, materials undergo regulatory testing. Issues arise from the variability between biodegradability tests. Some protocols reference rapid biodegradability in water; others evaluate a product’s behaviour as it breaks down in soil or landfill conditions. Biodegradability testing protocols measure decomposition at various temperatures, with different microorganisms, or in aerobic or anaerobic conditions (with or without oxygen). The most rigorous protocols require measuring the gasses released as the product decomposes or observing potential effects on plants or animals. The discrepancies between testing methods can lead to materials that bear the same label yet behave very differently.

The main issue reducing the effectiveness of biodegradable alternatives is the conflation between biodegradable and compostable. Compositing is a human-driven process where biodegradation occurs under specific conditions. If these conditions are not met, the material will not readily biodegrade. Instead, it will persist in the environment, sometimes causing even more harm to local wildlife than conventional petrochemical products.

A few days ago, while eating in a restaurant, the drink I ordered came with a straw. As he handed it to me, the waiter volunteered that it was made from biodegradable plastic. “No more soggy paper straws,” he joked. But I had to wonder: would the straw really biodegrade in the landfill it was destined for or did the manufacturers evaluate its end-of-life behaviour exclusively under controlled composting conditions? Worse still, what would happen if it did make its way into the ocean? Would its impacts be as significant as those of demonized conventional plastic straws, or would it readily decompose in a marine environment?

Worms will easily turn your food scraps into nutrient-rich compost, but they can’t digest most bioplastics.

Many labels touting a product’s biodegradability omit the specific conditions for which this is true. Even products labeled as compostable often don’t paint the entire picture. For example, most compostable plastics won’t decompose in your personal compost bin and are designed to decompose in industrial composting facilities instead. It’s actually more likely for biodegradable plastics to be recycled alongside their conventional counterparts than to biodegrade.

Unless companies specify the conditions in which their products are biodegradable (and the required end-of-life processing facilities are widely available), biodegradable materials are not the solution to the global pollution problem. The availability of these new materials is a promising start, especially considering how many options have appeared in such little time. But there’s still a long way to go in dealing with the garbage we produce.

Ultimately, the best practice is to avoid generating unnecessary trash in the first place (refuse is the first element of the Rs hierarchy). Biodegradability is not yet the solution it claims to be, although significant progress will undoubtedly be made in the coming years.

Until then, no straw for me.

For more information:

  1. EPA’s guide to Plastic Recycling and Composting
  2. European Bioplastic’s FAQ on Bioplastics

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