The right compost bin needs to fit your gardening routine as well as the corner you’ve chosen. You have to reach it with kitchen scraps, add bulky garden material and get finished compost out without fighting a fence or shrub.
I’ve used both the 220-litre Blackwall and the 330-litre version. The smaller bin suits modest, regular input; the larger gives useful extra capacity without a huge increase in diameter. I’d measure the space in front of the hatch as carefully as the bin’s footprint.
Let’s work out which size you can use comfortably, and when space for a second bin is more valuable than one very large container.
220L versus 330L: the footprint is closer than it sounds
I have used both Blackwall sizes. The 220-litre bin keeps a modest garden-waste routine contained without dominating a corner; the 330-litre version gives me more room for leaves, clippings and kitchen waste, and compost developed at the bottom after several months. Its lid can catch, so I check that it is seated after filling. Buy the larger bin if your regular input justifies it and you have room to empty it; the smaller one is easier to fit into a compact garden.
EvenGreener gives the 220L model as 74cm diameter by 90cm high, and the 330L as 80cm diameter by 100cm high. Those dimensions also appear in IPL’s specification sheet. They describe the bin itself; they do not include a person, an open lid or emptying space.
| Model | Published dimensions | Calculated circular footprint | When to consider it |
|---|---|---|---|
| Blackwall 220L | 74cm diameter × 90cm high | About 0.43m² | Smaller regular input, tighter space or easier reach |
| Blackwall 330L | 80cm diameter × 100cm high | About 0.50m² | More material with only a modest footprint increase |
The circular footprint increases by about 17%, while the nominal capacity increases by 50%. Those percentages are calculated from the published dimensions and volumes. They do not imply the larger bin composts 50% faster, and the circular area is not a realistic whole working area.
Mark the diameter on the ground before ordering. Then stand where you would empty it. If your feet land in a shrub, or a wall blocks the hatch, the paper fit is misleading.
Measure input for a few weeks
For a useful estimate, use a bucket of known capacity and note roughly how much suitable material you add each week. Include the dry shredded cardboard or woody material needed alongside wetter green material. Measuring peelings alone understates the volume the bin will have to receive.
Repeat during a busy garden period. One quiet February week tells you little about a flush of grass clippings or autumn clearing. Record exceptional surges separately: a whole hedge reduction should not dictate the size of a bin that normally takes modest weekly inputs.
An example makes the distinction clear. Two 10L buckets a week produce 240L of incoming material over 12 weeks. Four produce 480L. These are input volumes before settling and decomposition, not predictions of how full a bin will be or how much finished compost you will obtain.
Material collapses at different rates. Soft leaves, chopped stems and loosely crumpled cardboard do not pack like dense peelings. There is no dependable universal conversion from “litres per week” to a bin size that guarantees never overflowing. Use the count to distinguish a trickle from a sustained bulky supply, then allow room for variation.
If woody prunings make up much of that input, my blade versus turbine shredder guide explains the handling and collection differences. For a seasonal pile of leaves, making leaf mould in bags or a cage offers a separate storage route.
A second bin solves a different problem from a bigger bin
A single bin is convenient for adding little and often, but it is doing two jobs at once: receiving fresh material and holding older material while it matures. When every spare space is immediately refilled, finding the finished part can be awkward. With room for two, one can receive new material while the other rests. You can also use the spare space when turning a batch. Before buying two, put a bucket or barrow in front of each planned hatch and make sure you can stand there and work.
A larger single bin gives more space for input. Two bins can separate active filling from material left to mature, or provide somewhere to turn a batch. That can be more useful than adding fresh scraps endlessly onto compost you are trying to finish.
Two 220L bins provide 440L nominal volume, but they need two footprints and access to both. Do not compare 440L with 330L and overlook the working area. Two bins only improve the system if you have a plan for moving or resting the contents.
If your measured inputs are small, a second empty bin is not automatically an improvement. Start with the workflow you will use. For a steadily productive garden with enough room, leaving space for a second unit is sensible even if you initially buy one.
Allow for filling, turning and emptying
Top access: can you lift and remove the lid without catching a branch or shelf? Can you tip in a bucket without raising it uncomfortably? The extra 10cm height of the 330L may matter more than its extra 6cm width.
Front access: the hatch needs room for a scoop or spade and somewhere for the removed material. As a planning exercise, mark a clear metre in front, then try the actual movements with your tools and container. That metre is a suggested working allowance, not a manufacturer requirement or a guarantee of comfort.
Whole-bin access: small hatches are convenient for taking out a little finished material, but turning or clearing a whole batch may require lifting the shell or moving its contents onto a sheet. Leave enough space for the way you intend to manage it.
Route: check the narrowest gate and the walk from the kitchen. A bin that is awkward to reach on a wet evening is likely to receive less balanced attention than one on a practical route.
Do small plastic bins actually make compost?
Yes. RHS guidance says bins below one cubic metre are generally less efficient than larger ones, but can still make compost successfully. Both 220L and 330L are well below that volume. Neither size should be bought on the assumption it will reliably create a sustained hot-composting process.
A sheltered spot with some shade helps avoid extremes. Soil underneath is convenient for drainage and access by organisms; a hard surface can also work with appropriate drainage and a little soil introduced. Check the bin’s instructions and any base accessory rather than assuming every base plate is included.
Size also cannot compensate for a bin dominated by wet grass clippings. Mix suitable green and brown materials, keep air and moisture in balance and assess the contents as you go. Maturity depends on conditions and material; the calendar alone does not tell you that everything through the hatch is ready.
Buy capacity you can use
The 220L Blackwall is worth considering if the lower height and slightly smaller diameter make the bin genuinely easier to use. The 330L Blackwall is the stronger capacity option where both fit comfortably, because the footprint penalty is small relative to the extra volume.
Compare the delivered price and what is included. Some listings bundle a base and others do not. Check your council’s current compost-bin scheme as well: eligibility and subsidies vary by area, so a price advertised by another council is not necessarily available to you.
Finished garden compost has a useful destination in a coastal garden. Our guides to using compost and organic matter near the coast and improving sandy soil explain that next step.
Before ordering: mark the bin footprint, check a week’s input and rehearse emptying it. Then compare the 220L option and the 330L option against that real space. A usable composting corner is worth more than a large number printed on a lid.
