Throwaway plastic has found its way into almost every aspect of our lives: from the disposable coffee cup you pick up on the way to work or the straw in your smoothie, to the hidden fibres woven into wet wipes and tiny glittering fragments in make-up.

Of the 6.3 billion tonnes of plastic we’ve thrown away since we started mass-producing it in the 1950s, just 600 million tonnes has been recycled – and 4.9 billion tonnes has been sent to landfill or left in the natural environment.

While awareness of the detrimental impact plastic can have on the environment has exploded in recent years, environmentally friendly alternatives are only now picking up steam. As single-use plastics bans come in around the world – next year in the UK, and by 2021 in Canada – new materials are going to become ever more important. But are they all they’re cracked up to be?

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Biodegradable plastics are one set of materials that are becoming a popular replacement as consumers demand green alternatives. Rather than remaining stable for hundreds of years – the quality for which we prized plastic when we first began using it – biodegradable plastics can be broken down by microbes, chewed up and turned into biomass, water and carbon dioxide (or in the absence of oxygen, methane rather than CO2).

A subset of them are compostable, which means that not only are they broken down by microbes, but they can be turned – alongside food and other organic waste – into compost. Only a minority of these plastics are home compostable, so, the label “compostable” most often means industrially compostable. That coffee cup with a Seedling logo you’re drinking from won’t decompose very quickly, if at all, on your home compost heap, but will break down inside the right kind of industrial equipment.