Every year in New Zealand, 2.2 million tonnes of waste is generated via food manufacture – much of which ends up in landfills.
This organic biowaste could be used to improve our soils instead of damaging our environment, says environmental scientist Brett Robinson.
Photo: Unsplash / Gabriel Jimenez
He's leading a University of Canterbury research project exploring how this biowaste can be transformed into soil conditioner and animal fodder.
"We're producing wonderful food in relatively healthy soils – and a lot of the plant material we produce then gets put into a compacted landfill.
"Apart from [carbon dioxide release], that's also a waste of this very valuable organic matter the food contains and our soils require… and it's also a waste of valuable plant nutrients and also potentially animal nutrients.
"'Replacing our soil carbon is a critical priority – either directly or through an animal."
Using our own biowaste in our own soils would also boost the economy. Currently we import tonnes of biowaste for animal feed and tonnes of fertiliser, Robinson tells Bryan Crump.
"The irony is we import biowaste from overseas to feed to our animals.
'We import Plant Kernel Expeller from counties like Indonesia - about 200 million tonnes a year - when we could be using locally produced waste.
"There's a huge potential gain to New Zealand's economy to the tune of about 1.6 billion a year eventually, if all of these wastes are utilised."
It's a no-brainer that New Zealand's biowaste should be reused but it is a challenge to find uses for it in existing agricultural systems.
To be made more palatable to cows, biowaste can be transformed by micro-organisms found in bacteria and fungi or blending with other waste, Robinson says.
Ideally, all of New Zealand's food prodution waste should go back into the soil - either via animals' bodies or directly.
Increasing the carbon levels in our soils is important for New Zealand's greenhouse gas budget.
"In our current agricultural system a lot of this plant material is removed whereas in a natural ecosystem the plant material would decompose in the soil we remove it and then it might go to a landfill.
"Many of our soils, particularly cropping soils, are becoming depleted in organic matter. This reduces fertility and increases the leaching of things like nitrate into groundwater."
Biowaste has greater value as a soil conditioner or animal fodder than as fuel, Robinson says.
Energy production can instead be achieved with "the worst of the waste", i.e. sewage, he says.
The University of Canterbury research team is working with 21 local food processing companies keen to explore recycling options.
