In-home processing of organic kitchen waste using a worm-composter prototype : Deliverable D4.5 Evaluation of sideflows for upcycling, soil improvement and fertilizing resource: worm composting

Samenvatting

This report is part of the WUR flagship project Circularity by Design, embedded within the strategic investment theme Connected Circularity. The project aims to apply (re)design principles to develop a sustainable agri-food system within the Amsterdam Metropolitan Region. The organic fraction of household waste in urban areas in the Netherlands is mostly not collected via a source-separation waste management system, but usually ends up within municipal residual solid waste fractions at central waste processing facilities. Source separation is seen as a way to lower financial and environmental burdens. The European revised Waste Framework Directive (2018/851/EU, §10) requires that all municipalities must plan and implement separate biowaste collection schemes (either via curb side or drop-off collection systems). Alternatively, municipalities can encourage citizens to dump their biowaste directly into home or community composting so it does not end up in the public collection systems. One means of doing so is decentralized (small-scale) worm composting, in which compost worms partly break down this waste and convert the remainder into worm compost and new worms/biomass. A prototype household worm composter was tested during 50 days on its ability to convert a defined food waste mixture (representative of what is wasted on average in Dutch households minus the unsuitable items such as sauces etc) into worm compost and new worm biomass. It was concluded that compost worms can be fed 72.6 % of the food waste produced in a typical Dutch household and almost 38 % of the food waste dry matter was broken down by the worms. The food waste contained ~72 % water. The compost samples had at least the same nitrogen use efficiencies as cattle dung slurry. Regarding heavy metals and pathogens, a food waste/worm compost sample from a similar composter complied with the standards for Keurcompost. Initially, conditions in the composter were beneficially for worm growth and waste processing but during the course of the experiment, there was too high moisture build-up. The design should be further improved to allow for more aeration and better passage of the processed food waste/worm compost out of the reactor. After solving these issues, the composter is useful for decentralized waste recycling/upcycling.