Biowaste is any solid or liquid organic, biodegradable waste, which includes sewage sludge, organic industrial waste; agricultural waste; kitchen/food waste; green waste, sewage effluent and greywater.
Biowaste makes up more than 50 % 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 viable long-term management option and is becoming more difficult due to increased levies, lack of space and transportation distance, and a general community expectation of the need to develop sustainable use options. In addition, landfilling creates a significant regional economic and environmental issue and runs contrary to central government policy.
However, safe and sustainable biowaste management is a ‘wicked’ problem because of its inextricable mix of social, economic, environmental, infrastructural, political and cultural factors. Tackling this ‘wicked’ problem requires a transdisciplinary, holistic approach underpinned by the very best science and innovation.
Unlike many other waste streams, there are good prospects for alternative, economical and beneficial end-use options for organic wastes.
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)(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 always that simple, with the issues involved in these alternative solutions challenging 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.