How much space would we need to store the world’s plastic in landfills?

To store all of the world's plastic at depth, we'd need the space of a large city.

When we’re done with our plastic we have three options: recycle it, incinerate (burn) it, or send it to landfill.

We think about recycling as the holy grail of environmental action, but it’s really not. Most items can only be recycled once or twice (if they’re sent there at all), so they end up in landfill eventually. Recycling delays, but does not eliminate, plastic going to landfill.

Well-managed landfills are really important to stopping ocean plastics. One of the big sources of plastic pollution is littered plastics or waste stored in open dumps or landfills. Closed ones stop this plastic from escaping.

That’s an unpopular solution, but it shouldn’t be. Landfill gets a bit of an unfair reputation.

One question that comes up is whether we have enough space for all of this plastic waste. Will we run out of room to store it?

I didn’t know how much space this would take, and I struggled to find anything online that would give me the answer. So I’ve crunched the numbers to get an estimate.

The answer is less than I’d expected. Sending all of the world’s plastic to date to deep-storage landfill would take up a few thousand square kilometres. About the size of many major cities, such as London.

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The world’s plastic would make up a city-sized landfill site

Let’s work through the numbers.

We’re going to imagine that we bury plastics 30 metres below the ground. Of course, we’d have to have trash or ground on top of this to maintain this pressure. That sounds deep, but it’s fairly common for a landfill site. Some of the deepest landfills – such as Puente Hills in the United States – go as deep as 150 metres.

At this depth, the density of plastic waste is around 0.52 tonnes per cubic metre (m³).

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That means we need a volume (amount of space) of 1.9 m³ to store one tonne of plastic.

The world has produced 9.5 billion tonnes of plastic to date.

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We’re going to send all of this to landfill. The volume we’d need is 9.5 billion multiplied by 1.9. That’s 18.3 billion m³ of space.

That’s the volume that we’d need to store it. How do we get the area that it would cover? Well, this depends on the thickness of our landfill – how tall it is. The taller the landfill, the smaller the area.

Imagine we have a really shallow one that’s just one metre thick. The area for this would be 18 billion m². That’s 18,000 km². We’d have a landfill that’s one metre thick and covers an area of 18,000 km² – the area of 1.5 New Yorks.

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This is shown in the visualisation.

If the landfill was 10 metres thick, it would cover 1,800 km². That’s the size of London. And if it was 25 metres thick, it would be just over 700 km² – the size of Baghdad.

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The deeper the landfill, the less space it takes up

That thought experiment imagined that our plastic was buried 30 metres below the surface. If we bury it at the surface then we’d need more space.

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Bury it deeper – at 45 metres – and we’d need less. That’s because the density of plastic waste increases with pressure. The deeper it goes, the more tightly it’s packed together.

In the table, I’ve run through the numbers on how much space would be needed for landfills at different depths and thicknesses.

While the numbers can vary by orders of magnitude, there is a consistent message. Storing the world’s plastic waste underground would take a city-sized piece of land. Not the size of major countries, the size of major cities.

I didn’t have a good grasp on the numbers before I started, but I’d have guessed that it was more.

There are other concerns about landfills and these numbers can seem quite different at local or national levels. Nobody wants a landfill in their backyard so, choosing the right location is important.

But in total, the area needed for plastic landfill could be just 0.01% of the world’s land.

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1. I found it surprisingly hard to find figures for the density of plastics in landfill.

This density figure is taken from this paper by Cline et al. (2020).

Cline, C., Anshassi, M., Laux, S., & Townsend, T. G. (2020). Characterizing municipal solid waste component densities for use in landfill air space estimates. Waste Management & Research, 38(6), 673-679.

2. Geyer, R., Jambeck, J. R., & Law, K. L. (2017). Production, use, and fate of all plastics ever made. Science advances, 3(7), e1700782.

OECD Global Plastics Outlook: https://www.oecd-ilibrary.org/environment/data/global-plastic-outlook/plastics-use-in-2019_efff24eb-en

3. For these city comparisons, I’m using the ‘urban area’ classification of the city boundary.

You can find these comparisons to other boundaries here.

4. The original paper from Cline et al. (2020) did not include plastic densities near the surface.

Instead, I've used the figure from Palanivel and Sulaiman (2014) of around 0.2 tonnes per m³.

Palanivel, T. M., & Sulaiman, H. (2014). Generation and composition of municipal solid waste (MSW) in Muscat, Sultanate of Oman. APCBEE procedia, 10, 96-102.

5. Global land area is around 150 million km². A mid-estimate of our landfill area is 18,000 km², which is 0.01% of this figure.