What happens to the food scraps once the contents are collected by Auckland Council? Photo / 123rf
What happens to the food scraps once the contents are collected by Auckland Council? Photo / 123rf
OPINION
Tāmaki Makaurau’s new residential food waste system is now in full swing. What happens to the food scraps once the contents are collected by Auckland Council? Should you stop composting at home and use the council system instead? Kate Hall (aka Ethically Kate) dives in and explains all.
When you pop your food scraps out for collection, they’re taken to Papakura to be unloaded and checked. Your carrot tops and mouldy avocado skins stay there for a couple of days before they make their way down to Reporoa in trucks that carry construction materials from Taupō to Auckland and need to get back to that region.
At the Ecogas Organics Processing Facility in Reporoa, the scraps are screened for contamination. All contaminants are removed and the water is captured (about 70 per cent of food is water, so there’s a lot!). Now it’s time for the main event and the short answer to your question: Your lovely little scraps are processed in an anaerobic digestion system.
Picture a thick, liquidised soup being pumped through an anaerobic digester. For about 70 days, bacteria break down your food scraps to produce biogas, methane, carbon dioxide (CO2), and liquid digestate.
All these elements are used for a variety of purposes, but the liquid digestate makes up about 98 per cent of what comes out after the scraps have been through the anaerobic process.
The biogas generates electricity to power the Ecogas site and heat tomato-growing glasshouses nearby.
The CO2 and methane don’t yet serve a purpose, but in future the CO2 is intended to be used to help tomatoes grow and the methane may be pumped into Aotearoa New Zealand’s gas pipeline, which is only 400m from the main facility.
The liquid digestate is pasteurised and turned into Fertify, a fertiliser that is used by large farming, horticulture, and cropping operations.
I’m doing my best to answer your question in an unbiased way because there are many opinions on whether this new residential food waste system is positive or not.
The end result of the liquid fertiliser means chemical fertilisers don’t need to be imported that were manufactured using fossil fuel energy-intensive processes, but the arguments against using anaerobic systems that produce methane are also compelling.
Composting locally is a far more effective solution that builds community resilience. Photo / 123rf
The new food scrap bins keep more organic waste out of landfill, but they may also discourage people from composting at home or within their community, and that would be a social and environmental travesty.
If you have a compost bin at home or the capacity to start one, do it! Composting locally is a far more effective solution that builds community resilience, has a greater positive environmental impact, and also saves you money.
Why give someone else your organic matter when you can turn it into valuable soil and avoid buying compost from plant stores? Use resources like ShareWaste to find local composters who’d be willing to take your food scraps, and encourage your friends and family, too, to compost at home.
