What does biodegradable mean?

Biodegradable plates and cutlery being laid on a table

Are natural products better, then?

Again, there’s no simple answer. Just because something can biodegrade naturally, doesn’t mean it’s better for the environment.

When biodegradable products are sent to landfill, including biodegradable plastics and items like grass cuttings or newspapers, they break down into two greenhouse gases: methane and carbon dioxide.

According to a 2011 US study biodegradable plastic generates the most methane, followed by office paper, food waste and then newspaper, in the average landfill.

Now some landfill sites can collect methane and use it for energy. But the researchers found that many sites struggle to collect all the gas released – because different items break down at different rates. This means methane can escape into the atmosphere and contribute to global warming instead.

At the other end of the scale, if biodegradable items get completely buried in landfill with no exposure to bacteria, heat, oxygen, moisture or light, they may not decompose at all. The result is they're no better than single-use plastics and simply fill up landfill sites fill more quickly.

Should I avoid biodegradable plastics?

Biodegradable plastics were introduced as a more eco-friendly alternative to conventional plastic but they’re not the green solution originally hoped for. In fact, a recent study by University of Plymouth’s international marine litter research unit found biodegradable plastic bags were largely undamaged and still able to carry shopping three years after being buried in soil or left in sea water.

A better alternative may be ‘compostable’ or bioplastics. These are often made from plant materials, like starch, rather than fossil fuels and do exactly what it says on the tin – break down into materials such as water, oxygen and compost. Compostable plastics are best used for food packaging, like sandwich packets or compost caddy liners; it does not matter if they get mixed in food waste as everything can be disposed of together.

However, there are concerns over their use. That’s because only a small minority of compostable plastics can be put on your compost heap at home; the majority need industrial or local authority composters. These reach the higher temperatures and humidity needed to break down bioplastics properly.

And if compostable plastics get mixed up with the rest of your recycling, they could contaminate the lot. So it’s important to keep them out of your plastics recycling box.

Isn't there anything I can do?

Yes, there’s loads! First of all, make sure you’re doing everything you can to be a better recycler. If you do have a home composting system, check that everything you add is meant to be in there rather than an industrial composter. Find out if your local council collects compostable items and remember to keep them in a separate bin from other plastics.

Most of all, avoid buying anything that comes in single-use plastics, such as plastic water bottles or ready-meal trays, and stick to fresh, unwrapped foods – these may be the only things that can be truly said to be biodegradable.