How expensive to take 80% of plastics out the ocean?

Question

Suppose that all the world would work together to take plastic out of the ocean. Here I include microplastics, which are much harder to remove.

How expensive would it be to remove 80% (in wheight) of the plastic from the oceans?

This would also include structural changes to prevent most plastics from entering the oceans in the future. So for example, a 100fold decrease.

I guess that this would be really expensive, maybe trillions of dollars?

Clarification: if should have added a time scale. Let’s say this has to be done within 30 years.

Answer 1

A breathtaking amount of money

The current version of the question is asking how much it would cost to remove 99% of the plastics in the world's oceans in 30 years. From this we conclude that an organized effort is being made to remove the plastics.

A plastic bag was found in the Mariana Trench, 11km below the ocean's surface. According to a survey of the Pacific Ocean, the highest levels of plastic are between 200 and 600 meters below the surface. So we're not just scooping stuff off the surface, we're netting most of it below the surface. And some of it is deep. Let's hope that the last 1% is below the 1.5km line. Here's why:

Let's take fish plastic out of the ocean

We know that commercial fishing trawls between 240 and 1500 meters. I assume it's not that hard to trawl between 0 and 240 meters, it just isn't where the fish is.

In the U.S., commercial fishing employs approximately 1.1 million people and has 155 billion in sales. I'm using the "take fish from the water" estimates to help us understand what it would take to "take plastic from the water."

World-wide commercial fishing costs are hard to come by. I found one article from 2018 here, but it's numbers for the U.S. are SO FAR BELOW the government-reported numbers that I stopped reading it. Maybe in the five years between that report and today fishing profits have risen 340X. But I doubt it. To be fair, I have limited time today and only sped-read the article. I could be wrong about the conclusions it came up with.

The U.S. isn't the largest commercial fishing nation in the world by a considerable degree, but as one might imagine, neither China nor Japan are releasing accurate data. So, as a round (and nearly irrelevant) estimate, let's 10X what the U.S. is taking in. 1.5 trillion in profits.

And if you think reported profits are scarce, accurate reported costs are next to impossible to find. So, let's use a common retail profit margin number: 40%. That suggests that in one year the cost of taking fish from the water commercially is about 930 billion U.S. dollars.

The last number we need is, regrettably, very subjective. An accurate assessment of the decrease in available fish in the sea is horrifically complex and based on far too many variables (although good for them for trying to account for all those variables). It doesn't help that the issue is terribly politicized, with advocates of fish-baby-fish showing the world replete with fish and advocates of we're-doomed! showing the world about to lose every fish in the ocean. In a sense, they're both right to a degree, but the we're-doomed! camp is likely more accurate than the fish-baby-fish camp. Let's set the politics aside.

Heather Patterson, writing for the Australian Fish Stocks Report, has the following to say about Southern Bluefin Tuna:

Roughly speaking, in 70 years we've depleted the bluefish tuna by about 95%. Close enough for government work, as they say. We need to deplete the plastic in half that time.

Putting all that together to get an estimate that's so rough it will make angels cry

Why did I go to all that effort? It didn't take much searching to find an estimate of 150 billion dollars to "clean up ocean plastic and environmental pollution." But I think that's low. Really low. Worse, if you read that article, there's a lot more going on with that 150 billion than just pulling plastic from the ocean — assuming that pulling plastic from the ocean is even on their list of things to do.

So my goal was to come up with a way to rationalize a number. I used the world-wide commercial fishing industry to model the idea. It's rough. Really rough. And I'm sure there are people who can poke holes in the idea (not a bad thing, if it leads to a more accurate result). But what I came up with was this:

\$1.86 trillion U.S. dollars.

Answer 2

Just do nothing, stop putting the plastic in. We already have plastic eating bacteria. And radiation eating fungus. The Earth is trying to fix itself from our mess. Just let it do it's thing. https://www.theguardian.com/environment/2023/sep/28/plastic-eating-bacteria-enzyme-recycling-waste

In 2001, a group of Japanese scientists made a startling discovery at a rubbish dump. In trenches packed with dirt and waste, they found a slimy film of bacteria that had been happily chewing through plastic bottles, toys and other bric-a-brac. As they broke down the trash, the bacteria harvested the carbon in the plastic for energy, which they used to grow, move and divide into even more plastic-hungry bacteria. Even if not in quite the hand-to-mouth-to-stomach way we normally understand it, the bacteria were eating the plastic.

...

What Oda and his colleagues found in that rubbish dump had never been seen before. They had hoped to discover some micro-organism that had evolved a simple way to attack the surface of plastic. But these bacteria were doing much more than that – they appeared to be breaking down plastic fully and processing it into basic nutrients. From our vantage point, hyperaware of the scale of plastic pollution, the potential of this discovery seems obvious. But back in 2001 – still three years before the term “microplastic” even came into use – it was “not considered a topic of great interest”, Oda said. The preliminary papers on the bacteria his team put together were never published.

...

Fortunately, over the past four decades, scientists have become remarkably proficient at engineering and manipulating enzymes. When it comes to plastic chewing, “the Ideonella enzyme is actually very early in its evolutionary development”, says Andy Pickford, a professor of molecular biophysics at the University of Portsmouth. It is the goal of human scientists to take it the rest of the way.

When any living organism wishes to break down a larger compound – whether a string of DNA, or a complex sugar, or plastic – they turn to enzymes, tiny molecular machines within a cell, specialised for that task. Enzymes work by helping chemical reactions happen at a microscopic scale, sometimes forcing reactive atoms closer together to bind them, or twisting complex molecules at specific points to make them weaker and more likely to break apart.

If you want to improve natural enzyme performance, there are approaches that work in almost every case. Chemical reactions tend to work better at higher temperatures, for instance (this is why, if you want to make a cake, it is better to set the oven at 180C rather than 50C); but most enzymes are most stable at the ambient temperature of the organism they work in – 37C in the case of humans. By rewriting the DNA that codes an enzyme, scientists can tweak its structure and function, making it more stable at higher temperatures, say, which helps it work faster.

Throw money at this project. And we know the world can. Covid was the most expensive and rapidly developed cure ever. Throw covid money at the plastic problem and it will be solved in a few years.

Answer 3

Mankind would have to leave the planet.

Based on a 2019 article, 46% of the plastic in the ocean is broken fishing gear (nets, cages, oyster spacers, etc.). Another 20% (in 2019) was debris from the Japanese 2011 tsunami. If you add in the 9% (by weight) that is microplastics, there is no functional way of reducing the total plastics in the ocean by even 50% without ceasing human activity on the planet.

The problem is that, in order to stop putting plastic into the ocean, humans would have to stop using the ocean. They would have to stop living on the shores. They'd have to stop driving cars. The economic impact of that would be incalculable.

Answer 4

It will cost nothing (if you are patient). There is a substantial amount of energy to be liberated from plastic, and a lifeform will eventually evolve to make use of it. We may not be far off from this either. Some years ago, a bacteria was found naturally occurring in the guts of some earthworms that was capable of breaking plastics' molecular chains into much shorter chains; it wouldn't take much to go from this to decomposing them fully. What marine plastic is not decomposed in this way, will eventually be eaten by other organisms and drop to the ocean's bottom once those other organisms die, where it will be buried over time.

Preventing more plastic from entering the ocean will also happen for free, some years after producing plastic becomes uneconomical. This depends on the price and availability of oil, from which almost all plastics are made, and there is only so much sufficiently cheap oil in the world. Once it runs out, plastics will become unaffordable and will not be produced, and so eventually they will stop finding their way to the ocean too.

And eventually the last bacteria will eat the last piece of floating plastic, and the oceans will be free of plastic at no extra charge, even if we keep dumping it into them for as long as we possibly can.

Answer 5

I guess, it depends on the solution itself. Plastic is a material/resource which is useful to get recycled for production. If the "raw" of plastic somewhere is big enough it may be profitable to get into this - as some mines are profitable and others not especially. So, planning the delivery offset is key here. It may vary as hell, but the cheapest solutions work in good synchronization could win for someone who find it better to get big amount of it from, for example not very deep shelf, rather than buy some material, pay for chem-labs and for energy to produce plastic from scratch. That way of "mining" could later bring better offsets, which others could follow - hence make it cheaper and cheaper. And thus it would reduce some big amount of thrash from oceans in short, maybe a bit naive plan.

So the answer depends on the price ratio - production/recycling+delivery - which may vary quickly as geopolitics changes all the time on Earth, and I don't know this numbers right now, even for hypothetical country/company. It may be cheap enough one day to earn on it.

Answer 6

It would never end, it would become a revenue stream for multiple govt entities and big business, soon be rife with corruption, and like aid to war torn countries & the third World there would never be an end to the costs because the money stops trickling down to the actual work really quickly.