circular economy waste

Sustainable plastic from seaweed

A couple of years ago marine biologists conducted a wide scale survey of the sea floor around Europe, diving as deep as 4.5 kilometres down into the Cascais Canyon off Portugal. 6,500 sites were studied in total, and “litter was found at all surveyed locations”. Our rubbish is everywhere.

Plastic doesn’t biodegrade, so once it leaches into the natural environment, it stays there. It slowly breaks down into smaller and smaller pieces, but we don’t know how long it takes to disappear entirely – we haven’t had plastics for long enough. Somewhere between 500 to 1,000 years is as precise as we can be.

Given that a whole third of global rubbish ends up in the natural environment at the moment, we urgently need new forms of plastic. And they’re out there. I’ve recently covered edible disposable cutlery, plastic made from greenhouse gases, and packaging grown from fungi. Here’s another: a Japanese design team is currently developing plastics out of seaweed.


Their technique uses agar, a natural gelatin that is used in Japanese cooking. You may have used it yourself in making jellies or panna cotta. Or you may have encountered it in a petri dish at school, as it’s used in labs as a base for growing bacteria. It’s derived from red algae, which can be harvested from the oceans or grown in aquaculture. Chile is a big producer. The seaweed is boiled to extract the agar, which can be frozen or compressed to make shapes of varying degrees of stiffness. Current experiments have focused on cushioning and packaging, a sustainable replacement for things like polystyrene.

The work is at an early stage, so it’s too early to tell whether agar based plastics will be commercially viable or at what scale. But the idea won the Lexus Design Award recently, and it’s another example in the wave of innovation around plastics at the moment, and these new solutions can’t come fast enough.



  1. The reason why we make plastics from oil – as well as all manner of other planet-destroying things – is because it is cheaper and easier, and that is because we live in an oil based economy, financed by ‘petrodollars’.
    We humans are incredibly inventive so we can make plastics out of anything we like which provides the carbon, hydrogen and oxygen to make long chain polymers. The first plastics were made from coal in the days when we lived in a coal based economy. We can – and have – made plastics from carbon dioxide, a lot more sensible that trying to capture and store the gas. We can also choose to make plastics biodegradable – just like naturally occurring long chain polymers such as cellulose.
    What we seem to be incapable of choosing to do is to move from a fossil fuel economy to a solar economy – and that will be our destruction.
    In other words, ‘It’s the economy, stupid’.

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