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Published 24/08/2018

Trial by insect - innovative sludge reduction research

We are always looking for better ways of doing things and recently have been working with a Palmerston North based start-up, Prescient Nutrition. They are looking at market opportunities to covert bio waste away from landfills and have been working for the last six years on food scraps and other organic wastes.

So when they approached us late last year about whether we could spare some wastewater sludge for a trial we were more than happy to send a few kilograms from our 65 tonnes a day going to landfill.

Prescient ran a couple of trials using dewatered sludge and thermal dried pellets. The pellets were too dry and actually needed water added to make them palatable, but the dewatered sludge was just right. In the bench scale trials they managed to reduce the volume of sludge by up to 70% and produce a stabilised waste residue. The larvae could then be used to produce a range of value-added bi-products.

There is obviously a long way to go before a concept like this could be scaled. Our key challenges in Wellington is the odour from our unstabilised sludge, proximity of neighbours and limited land space at our treatment plant sites. The main benefit is that it is a low carbon emission approach and can produce a useful product from what is currently waste ending up in landfill.

Check out this short video of the larvae in action – viewer discretion advised in case you are a bit squeamish!


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