Not everyone wants the same from their compost bins – we look at some of the best compost bins for sale on the market today in different categories

Size matters

There are different categories in which to rate compost bins — aesthetics, speed, safety, cost and size. Let’s start with size first because it certainly matters for a compost bin and the bigger, the better. To have a chance of getting ‘hot’ and for the composting process to happen more quickly a pile needs to be 1m³ or bigger. Many, in fact, most composters on the market are less than this critical mass. When there’s too much outside surface area and insufficient inside space any heat that is generated quickly escapes. Trying to solve this problem has led to some intriguing inventions in the compost bin market.

Thermo-compost bins

Thermo-bins have insulated walls that are sometimes thicker or with an air gap between two outer layers of plastic. The risk of increasing heat in this way is that moisture will evaporate and the compost dry out, at which point decomposition can slow down, precisely the opposite of the desired outcome. If the bin is well sealed however, condensation can occur and keep the moisture levels up.

Turning compost

Moisture and air have to be evenly distributed throughout the heap if it is to continue to gather composting speed (and heat). If insufficient air is present the compost will become anaerobic, slow down and smell. For many years ‘turning’ has been the proposed solution to reintroduce air although the need to turn all but the largest compost piles is now disputed. Layering input materials carefully depending on their carbon and nitrogen content can replace the need to turn. For many home compost bins, for example ‘cones’, turning isn’t possible and so layering becomes more important. The Aerobin 400 introduces air via a patented ‘lung’ and in trials the invention worked, producing temperatures reliably higher than average and being less prone to drying out. For more information on the Aerobin see the article Best New Designs in Compost Bins

Green Johanna composter

The Green Johanna is a cone-shaped bin with insulation that comes with a stirring stick. On adding new material the top 6 inches of the composting matter is agitated. This bin keeps the matter moist and temperatures above that of the outside air.

Compost tumblers

Tumblers are another way of keeping the compost material exposed to air at all times but, like all of the smaller vessels, it requires a careful balance of carbon and nitrogen materials or won’t work properly. A drawback with tumblers is that they have to be loaded in one go rather than little by little, which could mean stacking waste while you wait. Twin tumblers can be bought but then the balance of ongoing input materials must be carefully monitored, which is the same as for other bins but in a tumbler you can’t see it, making it difficult to know whether the balance is right or not. They do turn easily provided the balance inside is right. If it gets too wet it can be heavy even with the turning mechanism. For more about Tumblers see the article at Tumblers – Why Buy One of the Most Expensive Composters on the Planet? and Compost Tumblers on the market

Nature Mill.  Cheating?

NatureMill is a tiny digester that can go in your kitchen. It cheats by using electricity to both grind up and heat the waste but for compost ready in two weeks …

Onto the matter of cost… the innovations above will cost you dear as these are some of the most expensive bins on the market. Green Johanna is the most reasonable and some councils in the UK offer them at a serious discount. Twin tumblers are the most expensive and only for the most committed composters.

Ex-ter-min-ate

For simple systems that do the same job just more slowly you will struggle to beat the Dalek, a simple plastic cone. It’s easy to move about, no fiddly assembly, and if loaded correctly it will quietly get on with the job. All plastic cones and bins are made of recycled plastic these days. I would still advise getting the biggest plastic bin with which you feel your outside space can cope, the bigger it is the quicker you will have compost and more of it.

Right wood for compost bins

At this end of the market the appeal of a natural material such as wood may be strong for people who clearly have an eco-conscience. Wooden bins or ‘modules’ (where two or three wooden bins are slotted together) are generally reasonably priced and aesthetically pleasing BUT, be careful, although they are often from FSC (ethically sourced timber) they are also ‘pressure treated’. This means treated with chemical preservatives. So you go to the trouble of growing organic veg for your family and all the time you could be leaching homoeopathic amounts of heavy metal into the compost! There are a couple of wooden bins available without preservatives and one with an eco-friendly preservative (well done Greenfingers.com for the PEFC Pine Beehive Composter) but the problem is that because wood is natural it will of course decompose. Using a water-based preservative is noble but will need to be re-applied annually, not very practical with a compost bin. For more on Beehive Composters see Beehive Composters and untreated wooden Beehive Composter

Plastic Nottoobadastic

I never thought I’d say it but in this case recycled plastic really does solve a problem with its moisture repellent and rot resistant qualities. The alternative, if you can’t stand the idea of plastic in your garden, is au naturel, a heap without sides, not enclosed, just sitting there in a pile. Your dad probably had one with tomatoes and potatoes spontaneously erupting from it! The drawbacks are that they do collect and grow any seed that blows in on the wind and you really can’t add anything that might be a danger to small children or pets, or potential food for vermin.

You pays your money, you takes your choice

Brightgreenlive’s (via Amazon) small beehive composter in untreated, unpainted natural pine. Self assembly is required and they recommend treating somehow. Pine is a soft wood so this will not last for many years but the price reflects that, £49.98.

For small composters for outside see The Nod on Small Bins – Smallest Composters for an Outside Space