Bio-based plastics can reduce waste – but only if we invest in systems to get rid of them

Waste plastic. Image: Getty.

With news that companies like Starbucks, Hyatt and Marriott have agreed to ban plastic straws, it’s a fitting time to consider the role of plastic in our daily lives. Plastics are an often overlooked modern wonder – cheap and multipurpose substances that can be fashioned into myriad products.

Drinking straws are just the literal tip of humanity’s plastic addiction. In 2016 global plastic resin production reached nearly 335m metric tons. By some estimates, it could grow to approximately 650m metric tons by 2020, roughly 100 times the weight of the Pyramid of Giza.

Our lab is one of a number of research teams looking for potential solutions to society’s plastic problems. We study a tiny photosynthetic bacteria, which we are using as a production platform to convert light and carbon dioxide into renewable compounds, including bioplastic alternatives. Bio-based plastics are a promising option for reducing plastic waste, but scaling them up will require substantial investments, both in making them and in special facilities for disposing of them.

Worldwide, only 14 per cent of plastic packaging is recycled. Image: Ellen MacArthur Foundation/creative commons.

Long-lived waste

Much of the world’s plastic output is manufactured into single-use objects, such as drinking straws. Indeed, food packaging and food-related objects, such as cups, carryout containers, shrink wrap and plastic bags, account for a large proportion of all plastics made.

Less than 10 per cent of all waste plastic is recycled worldwide. Most plastic food packaging cannot be easily recycled if it has any food remnants stuck to it, because these residues can interfere with various stages of processing. As a result, many recycling plants will not accept food packaging.

What about other plastic waste? About 12 per cent is incinerated, but nearly 80 per cent ends up in landfills or the environment. In the ocean, currents aggregate plastic trash in large floating “islands” of garbage.

A NASA simulation shows how ocean currents steer plastic waste into huge floating garbage patches.

Whether they are buried or floating at sea, plastics can take hundreds of years to break down. In the process they can wash up on shore, creating litter and tourism headaches. Furthermore, large plastic objects, and even the microparticles they can wear down into, are harmful to a variety of wildlife, including seabirds, marine life and corals.

Plastic from plants

A wide variety of bio-based plastics made from renewable biological compounds have been under study for many years. Today, many can serve as drop-in replacements for the fossil-fuel based plastics that most of us are familiar with, such as polystyrene and polyethylene.

Most bioplastics are currently made by taking sugars derived from plants, such as corn and sugarcane, and using microorganisms to convert them into raw materials that can be eventually formed into plastic resin. But there is a trade-off between making bioplastics biodegradable on the one hand and still durable enough for their purpose on the other. A straw and cup that disintegrate halfway through your road trip are not much use at all.

Many of the most promising bioplastics in production and in development can be rapidly degraded under controlled conditions, such as those in a large-scale composting facility. Here, bioplastics may be intermingled with other organics and mixed regularly to ensure that there is adequate aeration to promote rapid decomposition. One such facility that is particularly engaged in testing and improving the degradation of bioplastics is Cedar Grove, operated out of Washington state. The end result is a rich compost that is suitable for fertilising gardens and crops.

At Jepsen Prairie Organics in Vacaville, California, shredded organic waste is laid out in rows and covered to conserve heat as bacteria convert the materials into compost. Image: San Francisco Department of the Environment.

However, even bio-based plastics will still languish for decades or centuries if they are thrown in the trash and buried in landfills. Below the surface layer of a landfill, the conditions are often dry, cool and lacking in oxygen. All of these factors discourage the growth of microbes that can accelerate the breakdown of bioplastics. By contrast, compostable plastics are largely degraded within three months inside industrial compost facilities, where conditions are managed to promote aeration and temperatures are often substantially higher because of all of the microbial activity.

Similarly, it is unlikely that any developed materials will be biodegradeable under all environmental conditions. For example, they may not break down in the Arctic or at the bottom of the ocean. Conditions in such environments, such as low temperatures and oxygen levels and high pressure, can inhibit the growth of organisms that act to break the bonds within plastic polymers, leading to much slower rates of breakdown.

This means that any breakthroughs in materials science need to be coupled with sustainable methods for bioplastic production and a well-oiled system to direct bioplastic goods into composting facilities.


Using microbes to make bioplastics

Making plastic from plant sources is certainly more sustainable than fossil fuel-based approaches, but it requires land and fresh water to grow and process the feedstock materials. Our research lab is looking for ways to train photosynthetic microbes (cyanobacteria) that can naturally harness the sun to make these same bioplastic compounds.

In this process, these microbes perform the same role as plants, using sunlight and carbon dioxide to create sugars that can be converted to bioplastics. In fact, cyanobacteria are more efficient solar converters and don’t require soil or fresh water, so this approach could reduce competition for land and resources.

While it’s easy to malign the lowly plastic straw, it’s hard to come up with substitutes that are as cheap, lightweight and durable, and are environmentally benign. I believe progress is possible, but only if scientists can collectively come up with bioplastic alternatives and social policies support the composting infrastructure to dispose of them suitably.

The Conversation

Danny Ducat, Assistant Professor of Biochemistry and Molecular Biology, Michigan State University.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

These maps of petition signatories show which bits of the country are most enthusiastic about scrapping Brexit

The Scottish bit. Image: UK Parliament.

As anyone in the UK who has been near an internet connection today will no doubt know, there’s a petition on Parliament’s website doing the rounds. It rejects Theresa May’s claim – inevitably, and tediously, repeated again last night – that Brexit is the will of the people, and calls on the government to end the current crisis by revoking Article 50. At time of writing it’s had 1,068,554 signatures, but by the time you read this it will definitely have had quite a lot more.

It is depressingly unlikely to do what it sets out to do, of course: the Prime Minister is not in listening mode, and Leader of the House Andrea Leadsom has already been seen snarking that as soon as it gets 17.4m votes, the same number that voted Leave in 2016, the government will be sure to give it due care and attention.

So let’s not worry about whether or not the petition will be successful and instead look at some maps.

This one shows the proportion of voters in each constituency who have so far signed the petition: darker colours means higher percentages. The darkest constituencies tend to be smaller, because they’re urban areas with a higher population density. (As with all the maps in this piece, they come via Unboxed, who work with the Parliament petitions team.)

And it’s clear the petition is most popular in, well, exactly the sort of constituencies that voted for Remain three years ago: Cambridge (5.1 per cent), Bristol West (5.6 per cent), Brighton Pavilion (5.7 per cent) and so on. Hilariously, Jeremy Corbyn’s Islington North is also at 5.1 per cent, the highest in London, despite its MP clearly having remarkably little interest in revoking article 50.

By the same token, the sort of constituencies that aren’t signing this thing are – sit down, this may come as a shock – the sort of places that tended to vote Leave in 2016. Staying with the London area, the constituencies of the Essex fringe (Ilford South, Hornchurch & Upminster, Romford) are struggling to break 1 per cent, and some (Dagenham & Rainham) have yet to manage half that. You can see similar figures out west by Heathrow.

And you can see the same pattern in the rest of the country too: urban and university constituencies signing in droves, suburban and town ones not bothering. The only surprise here is that rural ones generally seem to be somewhere in between.

The blue bit means my mouse was hovering over that constituency when I did the screenshot, but I can’t be arsed to redo.

One odd exception to this pattern is the West Midlands, where even in the urban core nobody seems that bothered. No idea, frankly, but interesting, in its way:

Late last year another Brexit-based petition took off, this one in favour of No Deal. It’s still going, at time of writing, albeit only a third the size of the Revoke Article 50 one and growing much more slowly.

So how does that look on the map? Like this:

Unsurprisingly, it’s a bit of an inversion of the new one: No Deal is most popular in suburban and rural constituencies, while urban and university seats don’t much fancy it. You can see that most clearly by zooming in on London again:

Those outer east London constituencies in which people don’t want to revoke Article 50? They are, comparatively speaking, mad for No Deal Brexit.

The word “comparatively” is important here: far fewer people have signed the No Deal one, so even in those Brexit-y Essex fringe constituencies, the actual number of people signing it is pretty similar the number saying Revoke. But nonetheless, what these two maps suggest to me is that the new political geography revealed by the referendum is still largely with us.


In the 20 minutes it’s taken me to write this, the number of signatures on the Revoke Article 50 has risen to 1,088,822, by the way. Will of the people my arse.

Jonn Elledge is the editor of CityMetric. He is on Twitter as @jonnelledge and on Facebook as JonnElledgeWrites.

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