The future is compostable 

It was National Recycling Week last week. So, it’s particularly relevant that two recent newspieces have caught my eye. This one from the Guardian UK is reporting on results from a citizen science program called ‘the Big Compost Experiment’. As usual, the headline is more inflammatory than the actual content of the article and it certainly misrepresents the broader context: “’It’s greenwash’: most home compostable plastics don’t work, says study”. 

Plenty of people are talking about what is and isn’t greenwash these days, but rather than debate the nuances of marketing strategy I’d like to address this point: “home compostable plastics don’t work”. This is a point that is repeated a few times throughout the article and it is completely wrong, but also wrong in a really interesting way. 

Home compostable plastics are designed to break down under the right conditions. You wouldn’t want a plastic wrapper to start breaking down in transit, or on your kitchen counter, or while it is otherwise being useful. And let’s take a minute to acknowledge just how useful thin, transparent and flexible plastics are. I personally try to avoid plastics made from petrochemicals wherever possible. But I also know that you can drive yourself crazy trying to be ‘zero waste’ amongst other life pressures. Hopefully most of us are thinking of innovative ways that we can avoid single use items and integrate more reuseables into our lifestyle. But changing these kinds of habits is more difficult than many people acknowledge. 

Home compostable plastics are wonderful. They perform a job when needed but then genuinely break down into their most simple constituents (CO2 and water). In this case, where the lab tests are not translating into ‘real world practice’, the confounding factor is the differences in process and practice when it comes to the composting. Basically, the 900 people who took part in the experiment didn’t know how to manage a compost pile. This is something we knew already. Most backyard compost heaps are not properly managed, even in Australia where we have high rates of backyard composting and have done so for decades now. 

This lack of knowledge or first-hand experience with a well-functioning compost heap has some interesting consequences. It results in a lack of appreciation for the work is required to compost various materials, especially the more challenging materials like woody items or oils etc. We operate our composting heaps near the biological limit in terms of productivity. It is hugely rewarding to see tricky items like avocado stones and mango pits return to the earth in a matter of weeks. The compostable plastics that we receive from cut up mailing satchels are easier. They ‘disappear’ in a matter of days in our system, and will fully mineralise in not much more than that. 

And speaking of plastic, the second piece of news was the cessation of soft plastic recycling in Australia this week. Like I said, I personally try to avoid consuming much in the way of petrochemical based plastics. But we still enjoy store bought tortillas and packets of chips etc.  

And yes, I fully appreciate that reusables are something that we collectively need to focus on. Some brave entrepreneur needs to invest in future scenarios where it’s not just dry goods that are being refilled. They need to have some confidence that customers would willingly pay a little extra for the priviledge and service level. I’m keen to try out the new refillable deodorant from Zero Co, as soon as I finish my current bottle with trash packaging. 

Transitioning any society-wide habit is always going to be challenging. Until we can transition away from single use plastics for grocery items and take away foods, etc., we need decent alternatives and we need them now. The packaging industry has already eagerly taken up compostable plastics in a large way. What is lacking at this stage is enough composting capacity so that these ‘alternatives’ don’t just end up in landfills, or worse, in incinerators of one kind or another.  

And just in case the following question occurs to you, I have an answer to that too: ‘if compostable plastics are an intermediate measure as we move away from disposability then what do we do with all of the composting capacity once we have successfully moved across to systems for reusables?’. The great news is that any excess composting capacity/infrastructure in ten to fifteen years can be used to deal with wood waste or other tricky materials. Wood waste is a huge problem. Once again, we collectively lack appreciation for the power of biology when it comes to upcycling this material. We can improve the way that we harness natural processes, and we need to, for better environmental outcomes. 

A full understanding of composting processes not only allows us to take care of compostable plastics, it also yields the highest environmental outcomes in terms of avoiding methane and achieving greater rates of humification for carbon sequestration.

I’m often put into the difficult position of choosing whether to correct myths and expectations around composting or to not offend people who think they have been doing a great job. On the other hand, I have had more than my fair share of ‘mansplaining’ (which sometimes comes from other women!) when it comes to this topic. Standard experience with backyard composting is that ‘you let it do it’s thing and eventually you get compost’. This misperception is harmless enough. Some backyard heaps are not much better than landfill but the average heap is hopefully not producing too much methane. They’re not producing much compost either though, and commonly are simply producing an easy food store for rats and mice.  

We can do so much better than this. A healthy compost heap not only takes care of problematic ‘waste’ materials, it also performs some amazing transformations that result in really stable carbon molecules that lock away carbon in our soils. This process of humification only happens when you get the balance of elements and biology just right though. You need a thriving microbial community, producing very powerful enzymes and also intense redox dynamics on the nanometer scale, homogenised across your entire composting volume. The greater the proportion of your compost heap that has this sort of activity, the better. 

Backyard compost bins are slow because they have relatively rare ‘sparks’ of activity at places where the right conditions exist. We manage our Capital Scraps composting bays for maximum activity. Activity occurs throughout the heap (although not on the edges which tend to be dry and with too much air) at varying intensities and is highly dynamic.

In conclusion, are we disappointed by the lack understanding of composting processes or the cessation of soft plastic recycling in Australia (hopefully temporary!)? Not at all. It further confirms our mission. There is a reason that we perform our composting in full public view. We hope that it inspires some in our community to not only ponder the extent of the environmental benefits, but also the way that composting fixes other problems, from how we buy packaged goods, to futuristic aims such as green chemistry for brand new drugs and materials (eg. production of this leukemia drug has already been shown to be more environmentally favourable when using material from wood waste). To us, composting and the inherent biochemical processes at the heart of it are a glorious panacea for many interrelated problems. 

But just as soft plastic recycling has faltered due to a lack of support (the Federal Environment Minister is asking business to front up and I’m sure that Businesses wish that Govt did a little more to support these emerging industries, everyday citizens can always support new recycling endeavours with eager and respectful compliance), composting also needs more support. Support for new facilities, but also support to educate the masses, to tackle the large task of addressing wrong perceptions and demonstrating just how favourable good quality composting can be. 

Your involvement is a more powerful form of support than you may realise. Mandates and new facilities and changing legislation are all great but you can’t beat the ‘social norming’ or ‘keeping up with the Jones’ factor’ when it comes to changing behaviour on a large scale. Sign up or pledge from anywhere in Canberra:, it’s a vote for better quality composting and all that that implies. 

-Dr. Brook Clinton, Founder, Capital Scraps

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