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Home & garden.

13 August 2021

Best and worst compost bins

Using a compost bin is the most effective way of managing the composting process, so check the results of our expert tests to see which one to buy
Tom Morgan

The bin you use for composting can make a big difference to the speed and success of the process. Our latest tests have uncovered the best and worst for the job.

Composting is a great way to recycle garden and kitchen waste to make soil improver that you can use as a mulch. 

On a mission to find the compost bins that are easy to use and efficient, we tested a total of 12 different models. Included in our rigorous tests were popular compost bins from big-name brands, including Eco King, Grange and Thermo-Star.

Below, we offer a closer look at the benefits of compost bins and share the full results of our expert tests.


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What are the benefits of using a compost bin?

The benefits of using a compost bin

Composting is a natural recycling process that makes good use of what might otherwise become waste, and the finished product is one of the best and simplest materials for improving your soil.

Through our trials over the years, we’ve found that using a compost bin is the most effective way of managing the composting process and that the type of bin you use can make a big difference. So we decided to take a look at what’s currently on the market, and see which ones are the easiest to use and work most efficiently.

Compost bin test results

To identify the best compost bins on the market, we tested a selection of bins at different price points, with the cheapest costing just £24.

There was a big difference between our top and lowest performing compost bin. Scoring an impressive overall rating of 79%, the best compost bin scored five stars for assembly, composting efficiency and yield. But it was a very different story for our lowest-ranking bin. Scoring just 41% for overall rating, you'd be disappointed if you paid more than £100 for this particular model.

Only logged-in members can view our recommendations in the table below. If you’re not yet a member, join Which? to get instant access.

Compost bin
Best Buy (BB) / Recommended (RC)
Price (£)
Size (litres)
Assembly
Convenience: filling
Convenience: turning or stirring
Convenience: removing compost
Composting efficiency
Yield of good-quality compost
Overall rating
BB
200
200
79%
BB
65
600
75%
BB
120
330
72%
RC
32
220
65%
RC
105
400
65%

36
900
61%

24
350
59%

85
270
58%

30
300
58%

75
288
48%

126
650
48%

115
211
41%
The more stars the better. Rating ignores price and is based on: composting efficiency 30%; convenience of filling 20%; yield of good-quality compost 20%; removing 15%; turning or stirring 10%; assembly 5%. Composting efficiency scores comprised of average temperature of compost combined with the rate of settling and rotting.

Ready to start composting? See our advice on how to make compost

How we test compost bins

Compost bin

We chose compost bins for the trial that represented the most common types available to buy.

We used three bins of each product and arranged them in three separate blocks, so none of the same type of bins were located near each other.

To fill the bins, we collected soft green and brown material, and mixed it thoroughly in 50:50 proportions. 

Each bin was filled to half its capacity in April 2019, then every month was refilled with enough material to comprise a quarter of its capacity. Filling stopped in September 2019, resumed in April 2020 and the trial ended at the end of July 2020.

The contents were turned (or stirred where the bins weren’t easily emptied) twice in the first year in July and September, and once in the second year in late June, and the compost was watered if it dried out. Assessments of how much the compost had settled and started to rot and a temperature check were carried out every two months.

Gardening tool reviews and advice - see all the products we test and read our expert recommendations on how, and what to grow in your garden.