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.

 
 
 
 

The Adam Smith Institute thinks size doesn’t matter when housing young professionals. It’s wrong

A microhome, of sorts. Image: Wikimedia Commons.

The Adam Smith Institute has just published ‘Size Doesn’t Matter’, a report by Vera Kichanova, which argues that eliminating minimum space requirements for flats would help to solve the London housing crisis. The creation of so-called ‘micro-housing’ would allow those young professionals who value location over size to live inside the most economically-active areas of London, the report argues argues.

But the report’s premises are often mistaken – and its solutions sketchy and questionable.

To its credit, it does currently diagnose the roots of the housing crisis: London’s growing population isn’t matched by a growing housing stock. Kichanova is self-evidently right in stating that “those who manage to find accomodation [sic] in the UK capital have to compromise significantly on their living standards”, and that planning restrictions and the misnamed Green Belt are contributing to this growing crisis.

But the problems start on page 6, when Kichanova states that “the land in central, more densely populated areas, is also used in a highly inefficient way”, justifying this reasoning through an assertion that half of Londoners live in buildings up to two floors high. In doing so, she incorrectly equates high-rise with density: Kichanova, formerly a Libertarian Party councillor in Moscow, an extraordinarily spread-out city with more than its fair share of tall buildings, should know better.

Worse, the original source for this assertion refers to London as a whole: that means it includes the low-rise areas of outer London, rather than just the very centrally located Central Activities Zone (CAZ) – the City, West End, South Bank and so forth – with which the ASI report is concerned. A leisurely bike ride from Knightsbridge to Aldgate would reveal that single or two-storey buildings are almost completely absent from those parts of London that make up the CAZ.

Kichanova also argues that a young professional would find it difficult to rent a flat in the CAZ. This is correct, as the CAZ covers extremely upmarket areas like Mayfair, Westminster, and Kensington Gardens (!), as well as slightly more affordable parts of north London, such as King’s Cross.

Yet the report leaps from that quite uncontroversial assertion to stating that living outside the CAZ means a commute of an hour or more per day. This is a strawman: it’s perfectly possible to keep your commuting time down, even living far outside of the CAZ. I live in Archway and cycle to Bloomsbury in about twenty minutes; if you lived within walking distance of Seven Sisters and worked in Victoria, you would spend much less than an hour a day on the Tube.

Kichanova supports her case by apparently misstating research by some Swiss economists, according to whom a person with an hour commute to work has to earn 40 per cent more money to be as satisfied as someone who walks. An hour commute to work means two hours travelling per day – by any measure a different ballpark, which as a London commuter would mean living virtually out in the Home Counties.

Having misidentified the issue, the ASI’s solution is to allow the construction of so-called micro-homes, which in the UK refers to homes with less than the nationally-mandated minimum 37m2 of floor space. Anticipating criticism, the report disparages “emotionally charged epithets like ‘rabbit holes’ and ‘shoeboxes,” in the very same paragraph which describes commuting as “spending two hours a day in a packed train with barely enough air to breath”.


The report suggests browsing Dezeen’s examples of designer micro-flats in order to rid oneself of the preconception that tiny flats need mean horrible rabbit hutches. It uses weasel words – “it largely depends on design whether a flat looks like a decent place to live in” – to escape the obvious criticism that, nice-looking or not, tiny flats are few people’s ideal of decent living. An essay in the New York Times by a dweller of a micro-flat describes the tyranny of the humble laundry basket, which looms much larger than life because of its relative enormity in the author’s tiny flat; the smell of onion which lingers for weeks after cooking a single dish.

Labour London Assembly member Tom Copley has described being “appalled” after viewing a much-publicised scheme by development company U+I. In Hong Kong, already accustomed to some of the smallest micro-flats in the world, living spaces are shrinking further, leading Alice Wu to plead in an opinion column last year for the Hong Kong government to “regulate flat sizes for the sake of our mental health”.

Amusingly, the Dezeen page the ASI report urges a look at includes several examples directly contradicting its own argument. One micro-flat is 35 m2, barely under minimum space standards as they stand; another is named the Shoe Box, a title described by Dezeen as “apt”. So much for eliminating emotionally-charged epithets.

The ASI report readily admits that micro-housing is suitable only for a narrow segment of Londoners; it states that micro-housing will not become a mass phenomenon. But quite how the knock-on effects of a change in planning rules allowing for smaller flats will be managed, the report never makes clear. It is perfectly foreseeable that, rather than a niche phenomenon confined to Zone 1, these glorified student halls would become common for early-career professionals, as they have in Hong Kong, even well outside the CAZ.

There will always be a market for cheap flats, and many underpaid professionals would leap at the chance to save money on their rent, even if that doesn’t actually mean living more centrally. The reasoning implicit to the report is that young professionals would be willing to pay similar rents to normal-sized flats in Zones 2-4 in order to live in a smaller flat in Zone 1.

But the danger is that developers’ response is simply to build smaller flats outside Zone 1, with rent levels which are lower per flat but higher per square metre than under existing rules. As any private renter in London knows, it’s hardly uncommon for landlords to bend the rules in order to squeeze as much profit as possible out of their renters.

The ASI should be commended for correctly diagnosing the issues facing young professionals in London, even if the solution of living in a room not much bigger than a bed is no solution. A race to the bottom is not a desirable outcome. But to its credit, I did learn something from the report: I never knew the S in ASI stood for “Slum”.