11 April 2023
If you’ve looked for in-kitchen composting solutions, there’s a good chance that you’ve heard of electric composters.
The devices make – or at least claim to make – compost from food scraps.
There’s a big difference in how they work, though.
Some simply chop and dehydrate the materials you put in while others, like the Reencle Food Waste Composter, actually use bacteria, heat and air to replicate (and sometimes even improve upon) the conditions found in a compost heap.
Now a new study from the University of Brunei has revealed one thing kitchen composters need to consider when making compost in an electric composter – and it’s all related to an over-optimistic claim by manufacturers.
The researchers looked at one particular type, the Zero Waste Eco Bin. This is a bin which follows the ground and dehydrate method, but the researchers found the composter could process the food relatively quickly.
However, the study took issue with the claim that the compost was ready to use after 30 days.
After curing the compost for a month, the researchers found the compost still contained phytotoxins, which are substances that can harm plants.
As a result, the scientists questioned whether the device should be called an electric composter when the compost was not ready after 30 days, stating
However, most forms of composting require compost to be matured before it can be used.
Indeed, some commercial composters leave the compost to mature for at least a year before selling it.
The researchers also highlighted that taking steps to ensure a balanced Carbon Nitrogen ratio was correct was important to improve the results of the compost.
They managed this by using a combination of common carbon-rich materials such as bread and cereal and nitrogen-rich materials such as spinach.
What is the Carbon Nitrogen Ratio?The Carbon Nitrogen ratio is the balance of carbon and nitrogen in composting material.
The microorganisms that turn waste into compost need both carbon and nitrogen to function.
For optimal composting, this carbon: nitrogen ratio needs to be around 30:1, although research has shown that composting can be successful with a wide range of ratios.
Composters achieve this by mixing both high-carbon materials (called Browns) and high-nitrogen materials (called Greens) together when they make compost.
Greens and Browns refer to the carbon or nitrogen content, not to their color. For example, ‘Browns’ include shredded paper and cardboard, while ‘Greens’ include coffee grounds and tea leaves.
Learn more about the Carbon Nitrogen ratio.
It’s also worth noting that the researchers chose a device that composted the material at 70 degrees Celsius.
Some researchers believe this is too high a temperature, as it can reduce microbial diversity in the composting process.
The Zero Waste Eco Bin also sterilizes the compost, a process that will likely kill beneficial microorganisms that are key to achieving high-quality finished compost.
Still, the study highlights that while electric composters can be used to process waste quickly and efficiently in a kitchen, they’re not a magic bullet.
You ideally need to add both high nitrogen and high carbon material, and the compost needs to be allowed to mature for longer (and probably a lot longer) than most manufacturers recommend.
Finally, the study warns us to be skeptical of claims made by these manufacturers, especially when it refers to how quickly the compost can be used.
Azis et al, The Effect of Initial Carbon to Nitrogen Ratio on Kitchen Waste Composting Maturity, 2023, Sustainability