We ran Composting Trials of our Products. What Happened?

Composting trail stages

We recently rolled up our sleeves and ran composting trials of GREEN HOME products at Zero to Landfill Organics (ZTL) in Cape Town. In some ways the trials were predictable (spoiler alert: all our products are compostable) – but there were a few surprises too.

ZTL is an industrial, or large-scale, composting facility run by Melanie Ludwig. When Cassandra, GREEN HOME’s environmental research ambassador, would visit the site, Melanie’s standard greeting was: “Welcome to the farm!”. And yes, it is similar to a farm. But instead of rows of vegetables (those are growing on the plot next door), at ZTL you’ll find giant rows of compost.

These super-size piles amplify nature’s biodegradation process. Bigger piles mean more of the good stuff. More microbes (bacteria and fungi), which generate more heat. Temperatures of 60 – 70°C are typical in active large-scale compost piles. This helps to compost green waste rapidly while effectively killing off pathogens. The result? Nutrient rich compost that’s free of any bad stuff. 

compostable products lying on soil before being compostedPartially composted packaging samples lying on soil

Left image: Products at start of trial. Right image: Partially composted packaging. The previously clear PLA containers have become white, opaque and flaky, while the paper and bagasse products are wet and soft. 

So What Happened When we put GREEN HOME Products In These Piles?

We noticed that different products composted at different rates in different composting conditions. Our bagasse products and wood pulp product liked things juicy and composted much faster when mixed with plenty of food waste, or anything full of moisture. 

We assumed our corn starch based bioplastic products would prefer plenty of moisture too. But they composted fastest in a fairly dry compost pile which had built up good heat and contained lots of healthy white fungus.

After just 4 weeks in these dry and warm conditions, our corn starch bioplastic products samples – which included sandwich wedges, cold cups, coffee cup lids and more – had completely biodegraded. All that remained were some pieces of cutlery (see pic below) which were our thickest sample item by far. At this stage, the pieces of cutlery had become much softer, and changed shape when pressed.

The bioplastic layer on one of our hot cups had also disappeared, but the paper cup itself remained due to the pile being too dry for for paper products to break down quickly.

Pieces of partially composted CPLA cutlery.

Pieces of partially composted CPLA cutlery. At this stage they
are no longer hard, but breakable and soft to the touch, similar
in texture to unfired porcelain.

Chemistry Matters

Even though our two kinds of clear bioplastic bags look exactly the same, the wood cellulose and corn starch bags composted differently too – because they’re different at the molecular level. The wood cellulose bags broke down faster in moist conditions, while the corn starch bags composted faster at higher temperatures.

Composting conditions will always affect rates of biodegradation – it’s chemistry after all! But the essential elements remain the same: microbes, moisture and oxygen break down organic matter over time.

We found it fascinating to watch how our products broke down and plan to run more composting trials soon.  We’ll be sure to let you know how they go.

 

Do you compost at home? Let us know if you have any stories to share. And check out our compost solution providers page for an up-to-date list of people offering equipment, training and composting services.

About Cassandra Gamble

Cassandra is GREEN HOME's Environmental Research & Communications Ambassador.
Her BSc (Hons) degree from the Open University (UK) focused on Environmental Science, plastic pollution and sustainable innovation.
On behalf of GREEN HOME, Cassandra is also a founder member of ORASA,, the Organics Recycling Association of South Africa.