Plastics made from plants could be the answer to the world’s waste problem

Oh, well, that is depressing. Image: Getty.

Plastics are incredibly useful materials with extremely diverse properties, allowing a multitude of different applications that benefit our lives.

Bottles and forks aside, in the medical field alone plastics have been used for artificial heart valves, medical implants and devices, controlled drug release, specialist surfaces and coatings that repel water, organic batteries – the list is endless.

But, with marine plastic debris estimated to reach 250m tonnes by 2025, governments across the globe are starting to think about how to overcome this significant problem.

A fundamental part of this issue is that non-sustainable, single-use plastics account for up to 40 per cent of global plastic production. This equates to around 128m tonnes. The vast majority of these plastics have low recycling rates and do not biodegrade in an acceptable time span – polypropylene can take millennia to break down properly.

Worse still, if these plastics find their way into the marine environment, the motion of the sea along with sunlight can cause the plastics to fracture into small particulates called “microplastics”.

The presence of macro and microplastics in our oceans has been shown to have a detrimental effect on marine life. But the potential effect on human health is much less well understood.

A ban on the production of cosmetics and personal care products containing plastic microbeads came into effect at the beginning of the year. Realistically, though, this only accounts for an estimated 680 tonnes of microplastics per year in the UK.

The problem with plastics

It is clear then that plastic waste is a complicated problem – spanning economics, sustainability, social pressures and recycling infrastructure in both developed and developing countries. But while it’s widely known that plastics can be an issue for the environment, what isn’t often known is that the persistence of plastics in the environment is actually closely linked to how they are made.

The overwhelming majority of plastics are made using oil-based materials, meaning that, by their chemical nature, many plastics have no oxygen content. This makes them very hydrophobic (water hating) and, as such, it is very difficult for common bacteria or enzymes to break them down if they enter the environment.

Over the past few decades, there has been increased awareness of our dependence on a limited oil supply and this has driven research into alternative, sustainable sources of chemicals. In particular, the concept of using bio-based materials as a resource rather than oil-based materials has really gained momentum. Sustainable bio-based material can be waste crops, waste wood, waste food – in fact, any waste biological matter.

Most importantly, these natural, bio-based materials can easily be broken down into smaller chemical building blocks – called “platform molecules” – which in turn, can be used to make other useful chemicals, including plastics.


Nature’s building blocks

Using these platform molecules, the Green Chemistry Centre of Excellence at the University of York, has been working with the plastics industry to create a new generation of bio-based polyesters. These are often used to make fibres for clothing, as well as films and containers for liquids and foods. The resulting materials are entirely plant based, recyclable and – importantly – fully biodegradable.

Aside from sustainability, the huge benefit of using biomass as a resource is the high quantity of oxygen that is incorporated into nature’s chemical structures (celluose, glucose etc). By using bio-based materials to make bio-based plastics, the oxygen content is kept in the material. The hope is that by having a high oxygen content, the bio-based plastics will have high, but controlled biodegradability. This means that the bio-based plastic can totally and safely break down into benign starting materials.

But although this new generation of sustainable plastics is a huge step forward, and a compostable plastic is of huge benefit, this is by no means the end goal for all bio-based plastics.

Circular economy

The circular economy is all about keeping resources in a constant loop, reusing and recycling them as many times as possible. This helps to minimise waste and reduce the need for brand new resources.

Treating plastic waste as a resource rather than a problem is an important change than needs to happen over the coming decades. This will help to preserve our remaining chemical materials, as well as protect our environment.

Enough plastic is thrown away each year to circle the earth four times. Image: Pexels.

Plastics are a fundamental part of modern society and they are here to stay. Ultimately, society has to move away from oil-based products towards sustainable bio-based alternatives. But regardless of whether a plastic is oil-based or plant-based, the biggest impact you can have on the life cycle of a plastic product is to reuse and recycle it.

As a consumer, this means you have a choice and the power to make a positive impact. Find out where your nearest plastic waste recycling point is and look to promote home collection and the proper recycling of all types of plastic waste.

The ConversationSo next time you use the last of the ketchup, help to preserve our resources by making sure your plastic waste stays in the recycling loop.

James William Comerford, Postdoctoral Research Associate, University of York.

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

 
 
 
 

To beat rising temperatures, Vienna launches a network of 'Cool Streets'

A Vienna resident cools off at one of the city's new Cool Streets installations. (Courtesy Christian Fürthner/Mobilitätsagentur Wien)

Over the past several months, Austria has recorded its highest unemployment rate since World War II, thanks to the economic aftermath of the Covid-19 pandemic. With no job or a suddenly smaller income – not to mention the continued threat of the virus – many Viennese will opt for a staycation this summer.  

At the same time, last year, Austria’s capital experienced 39 days with temperatures of over 30°C (86°F), one of its hottest summers in history according to the Central Institute for Meteorology and Geodynamics.

Climate experts expect a similarly sizzling 2020 season, and city officials are now doubling down on efforts to combat the heat by launching a “Cool Streets” initiative as well as a new, state-of-the-art cooling park.

“As the city councilwoman in charge of climate, it is my job to ensure local cooling,” Vienna’s deputy mayor Birgit Hebein proclaimed at the opening of one of 22 new “Cool Streets” on 22 June.

“In Austria, there are already more heat deaths than traffic fatalities,” she added.

Hebein was referring to the 766 people the Austrian Agency for Health and Food Security included in its 2018 heat-associated mortality statistics. The number was up by 31% compared to 2017, and in contrast to the 409 people who died in traffic collisions the same year.

The project includes 18 temporary Cool Streets located across the city, plus four roads that will be redesigned permanently and designated as “Cool Streets Plus”.

“The Plus version includes the planting of trees. Brighter surfaces, which reflect less heat, replace asphalt in addition to the installation of shadow or water elements,” said Kathrin Ivancsits, spokeswoman for the city-owned bureau Mobilitätsagentur, which is coordinating the project.


Vienna's seasonal Cool Streets provide shady places to rest and are closed to cars. (Petra Loho for CityMetric)

In addition to mobile shade dispensers and seating possibilities amid more greenery provided by potted plants, each street features a steel column offering drinking water and spray cooling. The temporary Cool Streets will also remain car-free until 20 September.

A sensor in the granite base releases drinking water and pushes it through 34 nozzles whenever the outside temperature reaches 25°C (77°F) . As soon as the ambient temperature drops to 23°C (73°F), the sensor, which operates from 10 a.m. to 8 p.m., turns off the water supply.

The sensors were included in part to allay concerns about legionella, a pathogenic bacteria that can reproduce in water.  

“When the spray stops, the system drains, and therefore no microbial contamination can develop,” said Dr. Hans-Peter Hutter, deputy head of the Department of Environmental Health at the Center for Public Health at Medical University Vienna, in a televised interview.

Hutter also assured the public that there is no increased risk of a Covid-19 infection from the spray as long as people adhere to the one-meter social distance requirement.


But Samer Bagaeen of the University of Kent's School of Architecture and Planning notes that air cooling systems, like the ones used in Germany at abattoirs, have been found recently to be a risk factor for Covid-19 outbreaks.

“The same could be said for spay devices,” he warned.

Vienna’s district councils selected the 22 Cool Street locations with the help of the city’s Urban Heat Vulnerability Index. The map shows where most people suffer from heat by evaluating temperature data, green and water-related infrastructure, and demographic data.

“Urban heat islands can occur when cities replace the natural land cover with dense concentrations of pavement, buildings, and other surfaces that absorb and retain heat,” as the US Environmental Protection Agency states.


A rendering of Vienna's planned park featuring a Coolspot, which is scheduled to open in August. Click to expand.
(Courtesy Carla Lo Landscape Architecture)

Vienna’s sixth district, Mariahilf, is such an area. The construction of the capital’s first “Cooling Park”, a €1 million project covering the 10,600 square-metre Esterházypark, is designed to provide relief. 

Green4Cities, a centre of excellence for green infrastructure in urban areas, designed the park’s main attraction, the “Coolspot”. The nearly 3.40-metre high steel trellis holds three rings equipped with spray nozzles. Textile shading slats, tensioned with steel cables, cover them.

The effects of evaporation and evapotranspiration create a cooler microclimate around the 30 square-metre seating area, alongside other spray spots selectively scattered across the park.

The high-pressure spray also deposits tiny droplets on plant and tree leaves, which stimulates them to sweat even more. All together, these collective measures help to cool their surroundings by up to six degrees.

The landscape architect Carla Lo and her team planned what she calls the “low-tech” park components. “Plants are an essential design element of the Cooling Park,” Lo says. “By unsealing the [soil], we can add new grass, herbaceous beds, and more climate-resistant trees to the existing cultivation”.

Light-coloured, natural stone punctuated by grass seams replaces the old concrete surfaces, and wooden benches meander throughout the park.

Living near the park and yearning for an urban escape close by, Lo says she’s motivated to ensure the park is completed by mid-August.

“If we don't do anything, Vienna will be another eight degrees Celsius hotter in 2050 than it already is,” Hebein said.

Vienna recently came in first in the World's 10 Greenest Cities Index by the consulting agency Resonance.

“There is no one size fits all on how cities respond to urban heat,” says the University of Kent’s Bagaeen, who points out that Vienna was one of the first European cities to set up an Urban Heat Islands Strategic Plan in 2015.

In the short term, prognoses on the city’s future development may be more difficult: Vienna votes this autumn.

Petra Loho is a journalist and photographer based in Austria.