Composting and worm farming

We tested five different at-home food waste methods and dish the dirt on compost and worm farm systems.

Making compost from vegetable leftovers stock.

Composting your food waste is a win for the environment. Our trial of five methods, from a machine for your kitchen bench to outdoor worm farms, found you don’t have to pay top dollar to hit pay dirt.

What to know

What to know

What to know

If you’re keen to divert your food waste, here’s our advice:

  • Avoid mechanical processors. Neither triallist recommended the Food Cycler – the only machine of its kind we found for sale in New Zealand. Worse, it was the most expensive kit by far.
  • Keep in mind the importance of a garden. If you don’t have a backyard (or someone willing to take the finalised material), the only viable option is a commercial or council collection service. Private providers are typically restricted to major cities and established council schemes are relatively rare. However, some councils, such as Auckland and Waikato, are currently rolling out or trialling food waste collections in certain areas.
  • Don’t feel forced to pay top dollar. Our volunteers that trialled the cheaper systems were just as (if not more) satisfied than those who tried out the pricier options.
  • Consider shelter. The worm farms and compost tumblers didn’t do so well when exposed to the elements – the former because worms dislike the wet and extreme cold and heat (temperatures below 4ºC and above 35ºC can kill worms). Both compost tumblers we tried let in rain, affecting the contents.
  • Check for council subsidies. To encourage residents to keep their food waste out of landfill, some councils pay a contribution or sell discounted compost equipment. Before you buy, check your council’s website to see if you can save coin.

What we did

Ten Consumer staff members trialled a composting method they’d never used before. Some had a compost bin or worm farm up and running, although others were complete newbies. They tested and rated the systems from June to August – though our Food Cycler triallists had the machine for a maximum of a month each.

We didn’t test the effectiveness of the compost, as that depends on what went into each system.

Bokashi bins

The method: Food scraps, cooked foods, fresh lawn clippings and wilted flowers go into an airtight bucket, alongside a layer of powder or spray, which contains microbes that ferment the waste. Once the bucket is full, it’s left for two weeks (longer in cold weather), so you may require two sets. After that, the solids can be added to your regular compost pile or dug into the garden. Liquids can be poured down the sink or diluted and used as plant fertiliser.

Pros: Unlike regular compost bins, bread, cheese, meat and seafood can go into bokashi buckets. The systems don’t take paper or cardboard.

Cons: It’s a multi-step process. Microbe powder or spray must be regularly purchased. The two bokashi systems we trialled returned mixed results.

Bokashi Zing System 15L

$74.98 from Mitre 10 (includes bokashi powder, $15.29 for 1kg)

How our triallist rated it:

Maze 12L Bokashi System
Bokashi 15L Zing System
  • Value for money: Very poor
  • Set-up: Very easy (pre-assembled)
  • Size: Very large (for kitchen cupboard)
  • Time commitment: Moderate
  • Use it in future: Very unlikely
  • Comments: “The bucket was too large to keep inside. Having to chop up food before putting it in, compact everything with a masher (wash the masher!) and sprinkle on the Zing [bokashi powder] was annoying and time-consuming. The only benefit I can see is for those who dispose of large amounts of meat and dairy."

Maze Bokashi System 12L

$39.90 from Bunnings (includes bokashi spray, $12.98 for 500ml)

Maze Bokashi System 12L
Maze 12L Bokashi System

How our triallist rated it:

  • Value for money: Very good
  • Set-up: Easy (assembly required)
  • Size: Small (for kitchen cupboard)
  • Time commitment: Very low
  • Use it in future: Very likely
  • Comments: “The main advantage is it takes all food waste. We’ve cut the amount of waste to landfill by between a third and a half. Our kitchen bin doesn’t smell any more, nor does the bokashi bin as it’s sealed. The whole family uses it – it’s easy and painless. The first load is becoming compost really nicely.”

Rotating composters

The method: Fruit and veges, eggshells, coffee, tea, paper, lawn clippings, leaves and twigs are added to a spinning bin on legs. As the composting process speeds up if contents are regularly turned and aerated, a tumbling bin makes this easier. Once broken down, the compost can be used on or dug into the garden.

Pros: Compost is produced more quickly than in a standard bin. Raised from the ground, the material may attract fewer pests.

Cons: The bins can’t handle large amounts of dairy, meat, oils and seafood. Only one of the bins we tested received a thumbs up.

Jobmate Compost Tumbler 160L

$169.00 from Mitre 10

Jobmate Compost Tumbler 160L
Jobmate 160L Compost Tumbler

How our triallist rated it:

  • Value for money: OK
  • Set-up: OK (assembly required)
  • Size: Medium (for backyard)
  • Time commitment: Low
  • Use it in future: Very likely
  • Comments: “Rainwater came in through the air slots on the side, so we had to tape these up. The heavier it was, the harder the tumbler became to start moving, but it was still doable. It might be useful if you don’t have space for a larger compost bin – no worms but no rodents either.”

Maze Compost Tumbler 245L

$279.00 from Bunnings

Maze Compost Tumbler 245L
Maze 245L Compost Tumbler

How our triallist rated it:

  • Value for money: OK
  • Set-up: Difficult (assembly required)
  • Size: Large (for backyard)
  • Time commitment: Moderate
  • Use it in future: Unlikely
  • Comments: “The compost got too damp and slimy with winter rains. It’s a good composter for beginners, but you do need to monitor it. If it’s wet, you might have to go out every day and turn it. You’ll also need to have some yard space – it’s quite big.”

Worm farms

The method: Fruit and veges (with a few caveats), cooked food (ditto), egg shells, coffee, tea, paper, lawn clippings, leaves and twigs are fed to a bin of tiger, red and/or Indian blue worms, which eat the material and produce worm castings. This “vermicompost” falls to the bottom of the bin. Once harvested, it can be either mixed with soil and sprinkled on plants or dug into the garden. Liquids can be diluted and used as plant fertiliser.

Pros: Worms can produce finished garden material faster than a compost bin. Aeration isn’t required. The two worm farms trialled received the nod.

Cons: Worms aren’t as hardy as soil microbes. They’re also fussier eaters: disliking acidic, fatty and spicy foods as well as bread, dairy, meat, oils and seafood. A worm farm can’t be left unfed for long periods.

Tui Worm Farm

$99.00 from Mitre 10 (plus $50.00 for 500g live worms)

Tui worm farm
Tui Worm Farm

How our triallist rated it:

  • Value for money: Very good
  • Set-up: Easy (assembly required)
  • Size: Small (for backyard)
  • Time commitment: Very low
  • Use it in future: Very likely
  • Comments: “It’s easy to look after and takes up minimal space. The worms are happily eating away. Our kids (seven and nine) have taken a great interest in the worms. While the farm doesn’t compost the total amount of vege waste we use in a week, it’s a great addition to our home.”

Hungry Bin Worm Farm

$325.00 from Hungrybin.co.nz (plus $50.00 for 500g live worms)

How our triallist rated it:

Hungry Bin Worm Farm
Hungry Bin Worm Farm
  • Value for money: OK
  • Set-up: OK (assembly required)
  • Size: Medium (for backyard)
  • Time commitment: Moderate
  • Use it in future: Very likely
  • Comments: “The outdoor bin survived a couple of Wellington winter blasts without being blown open or over – I was impressed! It could be too big for indoor use, unless you had tons of spare space. I’ve grown very fond of my worms, which settled in well despite the cold and, after a couple of months, started to thrive.”

Commercial collection services

The method: Food waste is collected by a commercial composter courtesy of a bin left on the kerb once a week. The company creates and sells (or uses) the final compost. The commercial services are in their infancy and aren’t available everywhere.

Pros: It’s low maintenance. Both services tested won rave reviews from our volunteers.

Cons: The costs are ongoing. KaiCycle doesn’t accept eggs, meat, oils or seafood and, while planning to expand, is fully subscribed.

KaiCycle 20L bucket (Wellington)

$34.50 per month

How our triallist rated it:

KaiCycle bucket (Wellington)
KaiCycle 20L bucket (Wellington)
  • Value for money: Very good
  • Set-up: Very easy (pre-assembled)
  • Size: Large (for kitchen bench)
  • Time commitment: Very low
  • Use it in future: Very likely
  • Comments: “It’s very easy and convenient, especially as we’re flatting and don’t have much space. The bucket is a bit too big for our shared kitchen, so we used a smaller container and transferred the waste each night. The price is reasonable, so we’ll do it for the long run.”

WeCompost 20L bin (Auckland)

$46.00 per month

WeCompost 20L bin (Auckland)
WeCompost 20L bin (Auckland)

How our triallist rated it:

  • Value for money: Good
  • Set-up: Very easy (pre-assembled)
  • Size: Medium (for kitchen bench)
  • Time commitment: Very low
  • Use it in future: Likely
  • Comments: “We found this a useful way to get rid of all food waste, including things like chicken bones and other meat products. It’s very simple, saves room in our normal rubbish bin and reduces bin odours.”

Mechanical processors

The method: The Food Cycler comes with a bucket, into which food waste (with some exceptions) is added. The machine runs a three- to six-hour cycle in which the scraps are heated and shredded. It’s recommended that the leftover dehydrated material is then sprinkled on your garden.

Pros: Food Cycler accepts bones, fruit pits and meat. The system works indoors.

Cons: Considering the price, the machine has a long list of no-nos: large amounts of banana, bread, cake, citrus peel, cherry, dressing, grape, jam, melon, nut butter, orange, rice and sauce. Of the five, it’s the only system requiring electricity and producing noise, which put off our triallists.

Food Cycler

$650.00 from Snapfoodwaste.co.nz (includes filters, normally $75.00)

How triallist one rated it:

Food Cycler
Food Cycler
  • Value for money: Poor
  • Set-up: Very easy (pre-assembled)
  • Size: Large (for kitchen bench)
  • Time commitment: Very low
  • Use it in future: Very unlikely
  • Comments: “I was disappointed at the size of the bucket – my first go, I used a quarter of the scraps I had. When I put the end product on the garden it went slightly mouldy. It’s very expensive, with high ongoing costs. The filters last three months, which is $300 a year, plus power.”

How triallist two rated it:

  • Value for money: Poor
  • Set-up: Very easy (pre-assembled)
  • Size: Large (for kitchen bench)
  • Time commitment: Moderate
  • Use it in future: Very unlikely
  • Comments: “It says to sort the food scraps for best results – I was expecting to be able to put any everyday food scraps in it. I personally wouldn’t use it again. The noise was annoying. I’d need to have it running every day and I think it would use too much electricity.”

Electricity consumption: We measured the Food Cycler’s power usage during three cycles. Based on costs of 27¢ per kilowatt hour, the machine averaged 14¢ per cycle – about half that consumed by a new dishwasher per load. If you ran it every day (as our volunteers estimated they would), that’s roughly $49 a year.

The New Zealand supplier, SnapFoodWaste, said the machine, when running, “uses less than one kilowatt hour” (27¢) or 0.07 kilowatt hours (2¢) per day on standby.

GUIDE COST excludes delivery. RATINGS based on surveys completed by the triallist testing the product. Two triallists tested the same Food Cycler.

Health and safety tips

The bacteria Legionella occurs naturally in soil, potting mix and compost. The microbe can be inhaled, causing a lung condition with symptoms similar to pneumonia, including aches, coughing, fever and shortness of breath. If untreated, an infection can develop into Legionnaires’ disease, which can be deadly.

When working with compost or worm casts, wear gloves and wash your hands thoroughly afterwards. You can also wet any material to reduce airborne particles.

Rodents are another unwanted presence in compost piles. Securing wire mesh to the bottom of standard compost bins prevents them burrowing in, but still allows soil microbes and worms to do their thing. There’s a rodent-proofing guide on Predator Free Wellington’s website pwf.org.nz.

Why compost?

If you send food scraps to the dump, chances are they’ll end up getting buried. Without air, organic waste decomposes and produces methane, a greenhouse gas that traps more heat than carbon dioxide.

As long as it’s regularly aerated, the material in your compost will produce comparatively less methane and other greenhouse gases. Research indicates the same is true for worm farms.

If you’re a home composter, you’ll also prevent emissions created by transporting food waste to the tip. Studies suggest compost systems can transfer the carbon from organic waste back into the soil (a process known as “sequestration”), but this is dependent on conditions.

The harvested compost products, solid or liquid, help your garden thrive by adding oxygen and nutrients. Some final material is so potent it must be diluted before it goes on plants, topsoil and vege gardens. To be sure, read your system’s manual.

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