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.
Biowaste makes up more than 50 percent of the total waste going to landfill in New Zealand. About 200,000 tonnes of biosolids and 122,000 tonnes of food waste are annually landfilled. Landfilling is not a sustainable option for the future and the New Zealand Waste Strategy is to be able to minimise the amount of waste that is disposed of in landfills.
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 plant nutrients) soil attributes. Beneficial use of biowaste could reduce the reliance on inorganic fertilisers such as superphosphate, which has been associated with elevated soil concentrations of trace elements.
Although biowaste is a source of organic matter and plant nutrients, they can potentially contain as well organic and inorganic contaminants, and pathogenic organisms, which might pose a risk for public and environmental health if not properly managed. There are numerous treatment options to reduce or eliminate such contaminants, or if still present in small amounts, biowaste can still be used if properly managed. Scientists in CIBR and around the world are actively investigating to identify and reduce those risks. New Zealand guidelines(external link) are established to help to take safe and sustainable decisions for the land-application of biowaste.
One of the main issues with diverting biowaste from landfill is that alternative solutions are not simple, the issues involved with these alternative solutions 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 is working with some local government agencies and their communities to consider the options, enabling them to decide on the best solution for their situation.
The Australia and New Zealand Biosolids Partnership (https://www.biosolids.com.au/(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 about land application of biosolids, see below:
Science Media Centre NZ(external link) has audio clips of an expert panel discussing the benefits and challenges of biowaste reuse.
The New Zealand Treatment Collective (https://nzltc.wordpress.com/(external link)) works to improve communication to all stakeholders in the waste management industry and to help fund research into developing and improving land treatment technology in New Zealand