Ditch plastic dog poo bags, go compostable



File 20190227 150718 11v5pnz.png?ixlib=rb 1.1
Don’t do these doggie-doo don’ts.
Shutterstock

M. Leigh Ackland, Deakin University

We humans have a habit of avoiding our waste. We find organic waste particularly unpleasant. We bag it and dispose of it as soon as possible.

Even the most environmentally conscious person would rather not handle something like decomposing food or dog poo with their bare hands. Plastic bags are often the first step we take to disconnect ourselves from our waste – until we can get rid of it somewhere else.

Traditional plastic bags are made from ethylene, derived from petroleum or natural gas. Ethylene does not degrade easily. So these types of bags are major contributors to plastic pollution.

More than three-quarters of plastic ends up in landfill, while up to 5% finds its way to the ocean. Only 9% of plastics are recycled.




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Many environmentally conscious pet owners are turning to biodegradable bags as the solution to their doggy-doo woes, but many brands won’t break down in landfill, compounding the problem. Alternatives are at hand, though, with compostable bags and community sharing programs that can help non-composters.

A ‘biodegradable’ statement on a bag isn’t enough: it needs a logo

“Biodegradable” means something that can potentially be broken down naturally in the environment, particularly by microorganisms but also by other factors such as heat, light and oxygen. We usually think of biodegradable materials as derived from natural sources such as plants, but synthetic materials can also be biodegradable.

But there are issues with the term “biodegradable bag”. Bags can be labelled biodegradable, but after being used and discarded they might only partly decompose because the conditions are not right for full decomposition. Or else the decomposition might take a long time.

Full decomposition means complete conversion of the bag into simple substances such as carbon dioxide and water that can be re-used by microorganisms like bacteria and fungi.

Food becomes poop, which becomes…?
Carol Von Canon/Flickr, CC BY-NC-SA

The biodegradability of plastic can be measured in a laboratory using methods such as carbon tracking. There are international standards for testing biodegradability of plastics. The International Organization for Standardization (ISO) has developed these standards.

Unfortunately, ocean and landfill environments are not conducive for degradation of biodegradable plastic. Marine environments often don’t contain the right types of microorganisms needed to break down plastics, or there aren’t enough to be effective in a reasonable time frame. Landfill conditions often lack oxygen, which limits the types of microorganisms that can exist there.

Compost, however, provides an ideal environment for biodegradation. Compost contains a diverse range of organic materials that support the growth of many different varieties of organisms.

DNA sequencing has revealed the huge diversity of microorganisms that exist in compost. These include bacteria, fungi and invertebrates that can digest a wide range of organic materials. In particular, fungi are found to possess enzymes that are capable of breaking down many different organic substances.

Compost to the rescue

You can now buy compostable bags. These are a type of biodegradable bag that is suitable for disposal in compost only (not in the ocean or landfill!).

How can you tell if a compostable bag can actually be fully broken down in compost? Standards Australia produces standards for the biodegradability of plastic bags. Code AS 4736-2006 specifies a biodegradable plastic that is suitable for overall composting (which includes industrial processes) and other microbial treatment, while AS 5810-2010 specifies home composting.

Standards Australia provide a brief overview of the testing carried out for AS 5810-2010. Other countries have similar standards – for example, the US has ASTM code D6400, which certifies that the material meets the degradation standard under controlled composting conditions.

The Australian Bioplastics Association administers a voluntary verification scheme. This enables manufacturers or importers to have their plastic materials tested and certified.

There is a double arrow logo you can watch out for on bags that have been certified as home compostable and there is a seedling logo for certified compostable. If you cannot locate a certified compostable bag in your area, you can source them online. Make sure they have have the certified compostable logo of the country from which they come.

It is interesting to observe the biodegradability of a plastic bag in your compost heap, as I did with a compostable bag full of dog poo. After two weeks buried in the compost, the only evidence of the bag was some small black fragments. These looked like leaf mould except they had the print from the bag label on them. In comparison, a normal plastic bag buried at the same time was completely unaltered. Of course, this experiment is not proof of total bag degradation – proper laboratory testing would be required for this.




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What if you can’t compost?

If you cannot compost, you will probably be relying on your local council to dispose of your waste. If the council uses landfill for waste disposal then there may be no point in using compostable bags for your waste, as landfill does not have the right conditions for composting to occur.

If you have a kerbside green waste collection that is composted, this service most likely will not accept food waste at the moment – which means dog poo is very unlikely to be included. Nor may compostable bags be allowed in green waste collections. Some councils, however, are working towards food organics/green organics waste collections for the future, and these may include compostable bags.

Moyne Shire in western Victoria, for instance, provides compostable bags for dog poo and accepts it along with green waste in its fortnightly “FOGO” collection.

If you have material for composting but do not have a compost heap, you can join Sharewaste. Sharewaste links people who want to recycle their organic waste with their neighbours who can use the waste for composting, worm farms or chickens. So this is a way to avoid sending your organic waste to landfill.

Composting your organic waste is like harvesting rain into your water tank or tapping into sunlight for your energy needs. These things are meaningful beyond their utility; they connect you to nature and give insights into the natural cycles of life on planet Earth.The Conversation

M. Leigh Ackland, Professor in Molecular Biosciences, Deakin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Why compostable plastics may be no better for the environment


File 20180718 142426 1qf5pak.jpg?ixlib=rb 1.1
Single-use biodegradable plastics include claims that they break down quickly into benign end products, but the reality is more complex.
from http://www.shutterstock.com, CC BY-SA

Thomas Neitzert, Auckland University of Technology

As companies move to get rid of single-use plastic bags and bans on microbeads are coming into force, new biodegradable or compostable plastic products seem to offer an alternative. But they may be no better for the environment.

Recently, European scientists argued that existing international industry standards are insufficient and cannot realistically predict the biodegradability of compostable plastics. New Zealand’s Parliamentary Commissioner for the Environment (PCE), Simon Upton, weighed into the debate, questioning the merit of biodegradable plastics and urging the New Zealand government to deal with the confusion surrounding their labelling.

The key concerns include the terminology itself, the lack of appropriate recycling or composting infrastructure and toxicity of degradable plastics.




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Confusion over terms

We know that plastics hang around in the environment for a very long time.
Recent surveys show significant support among New Zealanders for initiatives to reduce single-use plastics.

Newly marketed single-use plastics that claim to be biodegradable suggest that they will break down quickly into benign end products, but the reality is more complex. A degradable or compostable plastic item may indeed deteriorate slightly faster than a conventional product, but only if the conditions are right.

The current industry standards are not taking into account real-life conditions and are therefore underestimating the breakdown times. The standards are also not accounting for the damage to marine life that ingest breakdown particles before a product is completely degraded.

The PCE highlights that biodegradation should not be confused with other natural processes, such as weathering. For a plastic polymer to biodegrade, it needs to be broken down through the action of living cells (mostly fungi and bacteria) into simple chemical elements.

However, as the graphic below shows, the speed of biodegradation can vary greatly, depending on the original material and whether the plastic ends up in a commercial composting facility or a backyard compost heap or the ocean. Differences in materials, labelling and capabilities of composting facilities are making it difficult for the system to function properly.


Parliamentary Commissioner for the Environment, CC BY-SA

Avoidance is best

Considering the New Zealand government’s intention to transition to a low-carbon economy and zero waste initiatives, the best answer to the problem is avoidance. Under the premise of convenience, we got used to a bag for everything, a plastic sleeve for a single slice of cheese or teabag, and a single-use plastic bottle for water. The production of all these containers contributes to carbon emissions as well as the later disposal.

In many cases, biodegradable plastic bags are made from crude oil, requiring carbon-based production processes and emitting carbon dioxide or methane when degrading. If we switch to no extra packaging, reusable containers made from metals or ceramics, and buy in bulk, then crude oil and gas can stay in the ground for a potential safe use by future generations.

Failing this, a second best option are products made from renewable materials. Here and in general, we have to insist on meaningful labelling with a clear pathway to deposition or recycling.




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Toxic components

Many degradable plastics include additives, designed to make the product less durable. At the moment, the various additives and fillers are leading to contamination of waste streams. Expensive sorting or subsequent landfill might be the only alternative. Adequate recycling or re-manufacturing facilities would need to be created in New Zealand.

In his letter to Eugenie Sage, the associate minister for the environment, the PCE also refers to toxicity of plastics. More independent research is required in this area and the principle of caution should be applied in the meantime. In this day and age, there is no need to release a new material into general circulation, where the harmlessness is not investigated beyond doubt.

In some cases, a material may be banned in Europe but still readily available in the United States and Australasia. One example is BPA (bisphenol-A), which was banned in parts of Europe and some US states, but Australia announced a voluntary phase-out in baby bottles.

The banning of cosmetic products containing microbeads is another case in point. In the last few years, some countries, including the US, UK, France, Canada, Taiwan and Sweden, have proposed or implemented microbead bans. The US ban on microbeads in rinse-off cosmetics has been in place since July 2017, but while the Australian government endorsed a voluntary phase-out in 2016, there is no official ban. New Zealand implement its ban this June.

The way forward

Consumer action and demand is a good start, with more and more of us changing our behaviour, leading by example, and asking industry to do likewise. A robust debate led by independent scientist should inform the public and authorities. Experiences like the ban of CFCs in the 1990s and New Zealand’s ban of microbeads are revealing to be ultimately successful. But they require regulatory intervention.

This can take the form of a ban of single-use plastics, which many countries have decided to exercise. Strengthening the standards framework is also required. At the moment, there is no overarching approach. Degradation in public waste facilities, in composting plants or in the sea is considered separately, as is toxicity.

The ConversationA material should be assessed fully in all relevant environments and then appropriately labelled. The New Zealand government should work with industry towards product stewardship, where the whole product life cycle is taken into account in the design phase. This will bring us closer to a circular economy, in which we reuse and recycle far more products.

Thomas Neitzert, Professor emeritus, Auckland University of Technology

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