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What is biowaste?

Biowaste is the organic, biodegradable component of municipal, commercial and industrial waste.

It includes municipal sewage sludge and septic tank sludge; greywater; sewage effluent; organic industrial waste; agricultural waste; kitchen/food waste; and green waste.  

Why is biowaste so important?

Biowaste makes up more than 50 percent of the total waste going to landfill in New Zealand. Biowaste is carbon-rich and generally contains high concentrations of valuable nutrients that, if properly treated and/or processed, can become a sustainable soil conditioner with the potential to provide valuable physical (e.g. increased water holding capacity), biological (e.g. beneficial organisms) and chemical (e.g. essential elements and plant nutrients) attributes.

What are the challenges of re-using biowaste?

The level and nature of contamination in biowaste varies, and our knowledge of contaminant bioavailability and contamination potential is still evolving.  Biowastes such as sewage sludge may contain potentially toxic or eco-toxic substances, which require careful management.

One of the main issues with diverting biowaste from landfill is that alternative solutions are not simple. The issues have challenged regulatory agencies worldwide. Small communities face the extra challenges of producing low volumes of a variety of different organic wastes and finding a low-cost, low-tech ‘whole’ waste solution that can be easily managed within the community.

CIBR can help local government agencies and their communities to consider the options, enabling them to decide on the best solution for their situation.

What do we do with biosolids (treated sewage) in New Zealand?

Currently, most local authorities put biosolids in landfills, largely because of the perceived and real uncertainties about the risks of alternative disposal methods.

A national survey commissionied by the Australian and New Zealand Biosolids Partnership in 2015 showed that 61% of biosolids produced in major wastewater treatment plants in New Zealand end up in landfill or monofill (a type of landfill where only one product is disposed of) – only around 17 percent is re-applied to land. In contrast, only 4 percent of biosolids from major Australian wastewater treatment plants end up in landfill. Over half of Australian biosolids are used in agriculture, with a further 10 percent composted and 1 percent applied in forestry.

Where can I find out more about biowaste?

The Australia and New Zealand Biosolids Partnership  (external link) has more detailed information on how biosolids are created, and how they can be used. They also have an easy-to-understand fact sheet (external link)  about land application of biosolids.

Science Media Centre NZ (external link)  has audio clips of an expert panel discussing the benefits and challenges of biosolids re-use.