Sources of ocean plastic pollution

Whilst there is thankfully increasing attention being paid to ocean plastic pollution, current community & government actions - mainly focussed on banning certain things like plastic bags & straws (the latter comprising a mere 0.025% of ocean plastic waste) - are largely tokenistic and not informed by the evidence of where the problem comes from - which as New Scientist reports, is substantially due to poor waste management in developing countries (like this open plastic dump island in the Maldives).

A 2015 McKinsey study found that 20% of ocean plastic waste comes from ocean-based sources like fishing vessels (nearly half of the Great Pacific Garbage Patch is fishing nets, so it's no wonder they also gather together other rubbish), but of the dominant 80% of ocean plastic that leaks from land sources (especially when near the coast), 75% is from uncollected waste and the rest due to leakage from poor waste-management systems. Clearly waste collection is the big problem, and moreover, 55-60% of all land-sourced ocean plastic comes from just 5 Asian countries, where waste systems are poor or non-existent. For example, only 5% of waste is collected in rural China (40% in China overall) vs 90%+ in the Philippines & developed countries.

Also this study found that 90-95% of river-borne plastic in the world’s oceans comes from just 10 rivers - 8 of them Asian (e.g. the Yangtze, Indus, Ganges & Mekong) and two in Africa (the Nile & Niger) - with all having large populations and poor waste management along their catchments (although another study estimated two-thirds of river-borne plastic comes from the top 20 polluting rivers, also mostly in Asia). Note however that the 1-1.5 million tonnes p.a. of river-borne plastic, which can come from places far from the coast, only contributes around 10-15% of the roughly 10 million tonnes p.a. total land-based plastic entering oceans, so by far the biggest source of ocean plastic is the roughly 8 million tonnes p.a. of uncollected & mismanaged waste nearer to coastlines, especially in poorer regions without any waste collection (and the total, including ocean-based sources, is about 12 million tonnes p.a., as in the chart below, although note there is a large uncertainty of some +/-40% in these total tonnage estimates).

Prioritising our "green budget"

My concern is that as recent public reaction to bag bans in Australia shows, there is a limit to what people are willing to "pay" (in $ & inconvenience) to address the problem of ocean plastic, so we need to ensure maximum "bang-for-buck". I for one have already had enough of not being able to drink the last of my cocktail through a paper straw that's turned to mush, and that makes me more resistant to the next daft ban that's proposed (& though straws are given out far more than necessary, sometimes they are needed, especially by some disabled people, so there are better ways to reduce this plastic waste than simply banning them). At some point, the community will say, "Enough!", but we will have done precious little to actually reduce ocean plastic. You can think of it as a limited "green budget" that's available to spend, which we should use as effectively as possible before it's all gone, so we need a comprehensive plastic management strategy that prioritises the range of potential initiatives. And given the majority of ocean plastic comes from regions of the world suffering extreme poverty, if we are going to be rational and focus on the most effective measures then top & urgent priorities over the short-medium term (more importantly than promoting recycling) should be for richer countries to help poorer countries improve (& actually have!) waste collection & management (perhaps with financial support being part of broader trade deals, which seems fair given how much global wealth & polluting consumption is concentrated in the hands of a small wealthy % of the population).

Textile washing & tyres are by far the biggest sources of microplastics affecting sea-life & our health;
igarettes, food wrappers & drink bottles litter our beaches

Policies that aim to reduce plastic waste escaping into oceans need to focus on the major culprits - both in terms of the type & magnitude of pollution caused by each source, and the degree of damage it imparts on natural ecosystems and human food chains. If our primary concerns are the health impacts of microplastics eaten by marine animals then we should focus on textile fibres, which are responsible for almost all microplastics found on the sea floor and also for most microplastics found near the surface where fish feed.

Vast quantities of microplastics are discharged during clothes washing (as washing machines typically lack waste-water filtering that could otherwise catch almost 80% of all microfibres), especially with new clothes, which can shed 8 times more microfibres than the same garment after 5 washes (a problem that's exacerbated by wasteful fashion culture, where the average Australian buys 14.8kg of clothing, or 56 new items every year, and nearly a quarter of 16- to 24-year-olds say they would only be pictured in an item of clothing one to three times on social media before discarding it). Top-loader washing machines produce 7x more microfibres than front-loaders, and of the total 1.5 million tons of microplastics estimated to be entering the ocean every year, synthetic textiles are responsible for 35%, with another 28% coming from tyres, 7% from road markings and 3.7% from ship paint (total 97.7%). Only 2% is attributed to "personal care products", which suggests microplastics in cosmetics aren't a significant problem (consistent with the chart below from a European Commission Study, and this industry link, although of course the latter isn't a neutral source). Clearly banning plastic bags & straws etc. will do virtually nothing to reduce microplastics pollution.

In beach clear-ups, plastic cigarette butts are said to comprise about a third of all items collected, although this data suggests 12% (about the same as bags, straws & stirrers combined), with the next most common items of food wrappers, bottles & tops accounting for 22%. This implies cigarette butts may be responsible for between 0.5 and 1.4 million tonnes of ocean plastic p.a. globally (scaled from 64kt p.a. in the US), which is some 5-15% of the roughly 10 million tonnes p.a. of land-based plastic entering the world's seas. To address these major pollutants, tobacco (& other) companies need to be pressured/incentivised to develop biodegradable alternatives.

Removing existing plastic pollution?

Technologies for collecting existing plastic waste may also be part of the solution, although mainly in areas of high concentration within rivers & harbours and coastal beaches, since about 95% of ocean plastic is below the surface. The chart below indicates 94% is on the sea floor, with just 1% on the surface and the remaining 4% on coastal beaches, but the concentration on beaches (per unit area) - which are a constant new source for ocean plastic - is about 30 times that on the sea floor (partly as a large amount of plastic in the ocean may get thrown back onto the shore, with possibly two thirds of all the buoyant plastic released into the marine environment since the 1950s being stored by the world’s shorelines). However this video suggests 92% of ocean plastic that is concentrated in five major ocean garbage patches is comprised of large items, so although these patches hold a relatively small percentage of total ocean plastic (the largest of these five patches, in the Pacific, contains 80,000 tonnes or less than 1% of total ocean plastic) there may be a large flow of plastics towards & through these concentrated patches (which is why they form these congregated patches), where light degradation may cause them to break down over decades into microplastics, before sinking and being dispersed across the sea floor. Therefore - despite its critics - technologies that collect plastic from these ocean patches before they break down may actually be an effective way of reducing plastic levels throughout the oceans.

Plastic has its benefits; recycling and alternatives are for the longer term

In the long term, the production of plastics could be constrained by oil reserves & energy-use (unless replaced by bio-sources), so we do also need to support innovation for more efficient usage, reuse & recycling (such as in concrete, for soft plastics), but although plastic packaging can sometimes be taken to absurd levels, initiatives in these areas need to balance competing issues, like the benefits of plastic for food hygiene, preservation & waste reduction (which otherwise adds to greenhouse emissions), energy use (e.g. for otherwise longer refrigeration of fresh food or to make alternative packaging/carrying materials), cost etc., so it's not simply a case of plastic = bad & re-use/recycling = good.

Common misperceptions about the impact of single-use plastics are identified by life-cycle analysis, which indicates food waste is often a much bigger problem than the packaging that can reduce this waste, even with highly-packaged meal kits. Also the impact of bag bans on plastic consumption is not as great as might be expected. For example, after California banned so-called single-use retail plastic bags, which people had actually been using as bin liners, 30% of the avoided plastic came back as new purchases of truly single-use rubbish bags (& more waste may arise from peopling throwing out the more resource-intensive thick bags that supermarkets issue instead, as appears to be the case in the UK, where supermarkets are now handing out more than a billion thick plastic 'bags for life' each year, which is using more plastic than with the previous 'single-use' bags - as further reported here). Depending on your assumptions and objectives, thick plastic bags and even paper bags need to be reused more than 3 times for a net environmental benefit vs a thin single-use plastic bag, whilst supposedly "green" cotton tote bags need to be used at least 130 times and perhaps more than 7000 times.

Single-use plastic shopping bags and drinking straws make up less than 1% of the more than 100 kg of plastic that each Australian uses every year, which if saved up over a year would only form the size of a volleyball, which (if the bags weren't used as bin liners) could be then thrown in the local recycling bin. We may do better to focus on reducing and recycling the two-thirds of the plastic we use for packaging. And of course things that cause problems also have benefits (e.g. faster check-out & hence lower grocery costs), so we need to be careful about banning things. For example, any parent knows how beneficial disposable nappies are, and actually cloth nappies may be worse for the environment than disposables if they use non-renewable energy for washing & drying. More broadly, dogs have a bigger carbon footprint than a 4WD, so should we ban dogs?!

Incentives are often better than rigid rules & product bans

Funding to support an evidence-based strategy like this should come from small, pragmatic levies on the worst culprits for plastic waste, e.g. retail bags, bottles & fast-food packaging (which of course isn't possible if you simply ban these items) and maybe a general virgin-plastic production tax. Such price signals will also help to make currently difficult & uneconomic recycling and bio-sourced, biodegradable plastics (made from crops, seaweed or fish scales) more commercially viable (but a virgin-plastic tax would probably not be a very effective incentive for directly reducing ocean pollution since the chances of plastic waste blowing into waterways would vary inversely with weight).

As a relatively poor multi-island nation that is struggling with ocean plastic waste ("drowning in plastic"), Indonesia is also leading the way with major investment in the development of bio-plastics (which in the near term may still cost 30% more than virgin plastic), including genuinely biodegradable/soluble bags that animals can safely eat, as well as compostable coffee cups and even human-edible/soluble food packaging, water balls & bottles based on seaweed, which unlike other bio-plastic sources doesn't require land that's needed for other purposes (such as food production), and may be a major source of economic growth for Indonesia. Likewise, East Timor is aiming to take a world-leading role in recycling plastics into new plastics or oil fuel, using Australian-developed technology. Perhaps phasing out Australian waste exports (which probably makes sense in the medium term if you assume all nations have similar wage levels and environmental standards) will encourage us to use our own technology too!

And as a final option (or until bio-plastics can replace non-biodegradable plastic), since unfortunately so many people in our wealthy society are so wasteful & careless (whatever it costs them), yes, bans on certain items may be necessary - if the evidence clearly supports it.

But if supermarkets were to bring back bags similar to those they used to have, then I'd suggest very slightly thicker ones that can be more readily reused (& don't need the ridiculously wasteful "double bagging" for heavy items that they used to do), charging (or taxing) maybe 5c/bag for self-service (or rounding up to the nearest 5c), or 10c per $10 of shopping (rather than counting many bags) for a checkout assistant that bags your items for you (which may be quicker and hence save the supermarket and ultimately the customer money).