Food scraps won’t separate themselves

Setting up home, community, or industrial collection and processing options for food scraps will only reduce food waste to landfill if people separate their food waste from their general waste in a way that reduces both waste streams, minimises contamination, and maximises diversion.

Minimising contamination: garbage in, garbage out

To make sure that the outputs of food waste processing options are high quality and able to be used for their intended purpose, it is crucial to make sure the right materials go into our food scraps bins.

What constitutes ‘the right material’ is confusing because it depends on what happens to the food waste next. The processing option being used and its scale or sophistication will dictate what can be successfully processed. Therefore, while general advice on this topic can be useful (e.g., WRAP’s resources on food waste collections), how food waste is separated and collected will always depend on your unique context.

For people living in areas where food scrap collection services are already provided, your council will have instructions about what can and can’t be accepted. If the government decides to require all councils to have kerbside food scraps collections, standardising the materials that can and can’t go into kerbside food scraps bins will simplify these instructions nationwide.

Tauranga City Council rolled out a rates-funded food scrap collection service in July 2021. Take a look at New Zealand Herald’s short clip on the service rollout, which includes tips for food waste separation and recycling people living in Tauranga. At the moment, each council with a food scraps service has its own systems and rules, but the Ministry for the Environment has suggested that, if kerbside collection of food scraps is mandated for all councils, the services should be standardised. In the first year of the service being in place, Tauranga residents almost halved the amount of food waste they sent to landfill.

What types of things could go into my food scraps bin if its collected kerbside?

The Ministry for the Environment suggests that kerbside food scraps bins should only contain food and garden waste and exclude all other potentially ‘biodegradable’ materials like coffee cup lids and cardboard. Other jurisdictions, like New South Wales, have taken a similar precautionary approach. The Ministry argues that paper and cardboard products, compostable packaging, compostable bin liners, tea bags, hair, vacuum cleaner dust, and animal waste should be ruled out, as these can be sources of contamination and/or potentially limit the culturally and socially acceptable uses of end-products like compost. The proposed exclusion of compostable plastics (both plant- and fossil-based) reflects the fact that they aren’t desirable inputs for many food waste processing options because they don’t contain nutrients and are a source of confusion for households.

Community engagement, consultation, and product standards (e.g. strict rules on the composition of ‘compostable’ plastics, ban or voluntary phase out of plastics in tea bags) could enable more materials to be accepted, as could distinguishing between grades of compost (e.g. for landscaping use vs food system use).

Home, community, and industrial enterprises: same, same but different

There are often subtle differences between what can go into your compost or worm bin at home and what might be suitable for community or large-scale processing facilities. That’s because managed community composting operations and large-scale processors have the scale and expertise to ensure their processes reach temperatures that are high enough to kill pathogens from animal-based foods and break down certain compostable products, as well as minimise odour and pest risks.

Maximising food waste separation

Even when people have a separate bin or home solution for food waste, they don’t always use it.

A trial in the Wellington suburb of Miramar found that people given food scraps bins for weekly kerbside collection still put a substantial amount of food waste in their general rubbish, and those given a compost bin, worm bin, or bokashi bin trial continued to put food waste in the general rubbish too, in greater volumes than the kerbside group. Old habits die hard, and new ways of managing food scraps need to be well designed and easy for people to incorporate into their daily routines.

For councils designing kerbside food scraps services, insights from the UK suggest that more household food waste is separated if food waste bins are collected weekly (especially when coupled with fortnightly general waste collection) and when food waste is collected separately from green waste, although combined waste has been collected in Christchurch for many years.

A New South Wales study confirmed that food waste diversion is better when landfill options are limited by smaller general waste bins collected less frequently. It also found that the longer an area has had food scrap collections for, the better the residents become at diverting their scraps from landfill.

Clear communication, reliable services, and good bin design (including possibly the provision of bin liners) are also crucial to high engagement. Supporting tools like prompts, information campaigns, incentives, and consequences could help too.

Simple tips for keeping kerbside scraps bins ick-free are provided by Hamilton City Council and are an example of how councils can encourage their community to make the most of their bins. The easier it is for people to separate their food waste, the more likely they are to do it.


For people using home solutions, understanding the details about how to manage your compost, worm farm, or bokashi effectively is crucial.

Concerns about pests, odour, and what to do if something goes wrong have been found to be barriers to full utilisation of home food scraps processing options.

It’s also crucial to make sure that you pick the right solution for you. For example, while bokashi bins are often marketed to people who don’t have enough space for composting or worm farming, people opting for bokashi still need to think about what they’ll do with their food waste pickle (the product of the bokashi process) and need an additional bin to cover the weeks during which their bokashi is maturing and can’t be disturbed.

As multi-unit dwellings become more common, it will be increasingly important to consider how to effectively manage waste in these settings, including food waste.

Multi-unit dwellings often don’t have kerbside collection services for each unit: waste is aggregated and collected in bulk for offsite management. This approach can be applied for separated food waste too, but odour and pest risks need to be managed (e.g. through regular collections, use of biochar to neutralise odours, physical separation of food waste collection sites away from living areas). Dehydrators have been proposed as a solution to keep food scraps stable and smell-free between collections in multi-unit dwellings, but they use a lot of energy and can create odour, pest, and pathogen risks if the dried food is exposed to any moisture during storage.

On-site processing (e.g. shared compost bins or worm farms in outdoor spaces associated with the complex) and partnerships with community composting enterprises may be part of the mix of solutions, and home-based solutions can play a role too, depending on space availability (e.g. a bokashi bin can fit under the sink, and a worm farm can fit on a balcony) and access to soils (e.g. the building’s gardens, balcony pot plants, or a friend’s backyard) to add resulting organic material to.

What about putting food waste down the sink?

People living in multi-unit dwellings often wonder whether they can dispose of their food scraps down the sink. The environmental impacts of in-sink disposal of food waste vary region-to-region depending on how wastewater in an area is treated.

Everything that goes down our sinks and toilets ends up in the sewers, which lead to wastewater treatment plants. In some parts of the country, wastewater undergoes anaerobic digestion (e.g. in parts of Auckland, Hamilton, Palmerston North, Christchurch, and others), meaning that methane is captured and used to generate energy. Meanwhile, about 40% of wastewater from the country’s largest wastewater treatment plants is treated without energy capture meaning that food thrown down the sink will release greenhouse gases.

Following wastewater treatment, biosolids remain. The end fate of the biosolids varies, but the vast majority (about 70%) is either landfilled or used to rehabilitate quarries. A small portion is used on agricultural land (generally after composting, vermicomposting, or thermal pasteurisation).

In addition to considering how wastewater is managed, it is also important to consider the impacts of increasing the wastewater treatment burden and risk of pipe blockages, given this infrastructure wasn’t designed with food waste management in mind. Even when food waste is ground up using in-sink disposal units, it can still block pipes (especially fats, oils, and greases). We also waste fresh water when we wash food down the sink.

According to BECA, five wastewater treatment plants in Aotearoa anaerobically digest their municipal wastewater, capturing biogas which can be used as an energy source. This means that there is some energy recovery from food waste that is disposed of down the sink in these parts of the country. However, our wastewater infrastructure wasn’t designed with food waste disposal in mind, so disposing of waste in this way can put extra pressure on our pipes and treatment facilities. 

Date released: 29 March 2023
Last updated: 29 March 2023