Vermicomposting of Biosolids and Beneficial Reuse — New Zealand Commercial Case Studies from 4 Communities over 8 Years

Earthworms are the emerging work force behind the up-cycling of dewatered sludge from municipal and industrial wastewater treatment plants and of wet organic residues from food processing industries in New Zealand. Vermicomposting is increasingly becoming the strategy of choice, transforming these sludge’s and wastes into a safe and highly valued fertiliser and soil conditioner known as vermicast for use in agriculture, horticulture, nurseries, and recreation areas. Acceptance of the technology has seen vermicomposting grow from processing some 2,000 tonnes of sludge in 2008 to close to 200,000 tonnes in 2015. Globally the traditional means of disposing processing wastes to landfill is under close scrutiny due to high capex and opex costs and negative environmental impacts. Increasingly stringent legislation means communities and industries are seeking the security of alternative solutions when planning their long-term waste biosolids disposal strategies. Important to these are excellence in environmental performance, ecological sustainability and the need to be cost effective. Vermicomposting technologies achieve this through the conversion of biosolids to a safe fertiliser and soil conditioner suitable for sustainable land utilisation. Vermicomposting is natural process, is highly cost effective for industrial and municipal organic wastes streams and overcomes cultural resistance of human waste utilisation to land. A number of case studies from municipal wastes and industrial are discussed. Municipal wastes from Maketu, a small community of 250 households producing 0.5 tonnes biosolids per day. Te Puke, a semi-rural community of 8,000 people producing 900 tonnes p.a., and Rotorua and Hamilton with combined populations of 218,000 and diverse industrial footprints producing 10,000 and 13,500 tonnes p.a. of biosolids respectively. Industrial sludge and wet organic residues vermicomposting operations are presented for Miraka (dairy) (2,500 t/a), Fonterra (dairy) (30,000 t/a), Seeka (horticulture) (5,000 m3/a) and Oji Fibre Solutions (100,000 t/a), (formally CHH Pulp and Paper), who have diverted their organic waste sludge’s away from traditional landfill disposal to vermicomposting up-cycling.