There’s plenty of interest in organic compost – and plenty of shops selling it.
But in my research for this article, I’ve found plenty of pitfalls too. The very definition of organic compost is questionable, and not all organic compost is good for the environment.
Some gardeners assume that organic compost is also peat-free – but that’s not always the case.
That might sound confusing. But if you want to use compost that isn’t going to harm the environment and is good for your plants, it’s worth taking a little time to understand what’s going on.
- What is organic compost?
- What should an eco-friendly gardener look for in compost?
- Testing your compost
- Making your own organic compost
- What’s the best organic compost to buy?
- Summing up
What does organic compost actually mean?
The term organic itself means different things to different people.
A soil scientist will use the term organic soil, for example, to refer to soil created by the decomposition of previously living materials. A gardener might refer to organic soil as soil which has not been treated with man-made chemicals or herbicides.
Technically speaking, all compost is organic, since it is created via decomposition.
But for the average gardener, organic compost generally means compost that doesn’t have added man-made chemicals.
Many people also believe that organic compost doesn’t contain peat, but that’s not always the case.
Is organic compost certified?
Roy Lawford, of O&F Organic, explained to me that in the UK organic is only a legal term when it applies to ‘food’ or ‘feed’.
If the item is not a ‘food’ or a ‘feed’, any producer can call it organic.
So any product – including compost – can be called organic without being certified, as long as you can’t eat it.
There are certification systems which can used for compost. These allow a product to be labelled ‘Approved for use in Organic system’ rather than organic.
There’s also a compost certification scheme called the PAS100. However, this is separate from organic certification, and the logos used do not include the word organic.
Is organic compost chemical free?
Despite claims by some compost sellers, there is no such thing as a chemical-free compost.
After all, chemicals are the very building blocks of our world.
Take dihydrogen monoxide, for example. It’s used in pesticides, as a solvent and indeed in the nuclear industry.
Not really. It’s just H20, AKA water.
What should an eco-friendly gardener look for in compost?
Even if all compost is organic, there are still some things the eco-gardener can look out for when choosing a product.
Peat stores carbon – and lots of it.
There are over three billion tons of carbon stored in peat in the UK alone.
Digging up and using peat releases carbon into the atmosphere. And compost is a big user of peat. In fact, multi-purpose compost can contain between 30 and 70% peat.
So peat-free compost, whether organic or not, should be essential for anyone who cares about the environment.
Unfortunately, just because compost is labelled organic doesn’t mean it is peat-free.
What’s more, it is not always easy to see if a compost labelled as organic uses peat. You may be better off looking for peat-free compost rather than organic compost. You can also see below for a selection of the best peat-free composts.
All compost should be free of herbicides. Unfortunately, there is widespread use of herbicides for growing crops and fodder. Some of these herbicides can pass through an animal’s digestive system, and are not broken down by the composting process.
Herbicides can be found in compost too.
So when choosing a compost, it’s important to buy a reputable brand.
Whether organic or not, if you have the time it’s also a good idea to check if it has been tested for herbicides or perform your own test (see below).
Free from physical contaminants
Organic compost should be free from substances like metal and plastic.
Unfortunately, there is so much plastic in the environment now, it’s difficult to find compost which is completely free of it.
This is such a big problem that the Soil Association has stopped issuing certification for compost made from green waste. Fortunately, they do certify a small number of other composts.
Testing your compost
Testing compost is actually very easy, and can help detect herbicides which could cause damage in your garden.
Simply plant two trays of seeds. One should be in the compost you are testing.
The second should be in compost you have made at home or have used before. This acts as a control. After all, as we gardeners know, there are many factors that affect plant development.
For the test, it’s best to use plants that are particularly susceptible to herbicides, such as beans, tomato plants. The very best plant to use is clover, which is affected by tiny amounts of herbicides such as aminopyralid.
If there are any herbicides in the compost you are testing, you’ll start to see problems with the seedlines. This could include stunted growth or furled leaves.
Make your own organic compost
I’ve experienced herbicides once. (In manure, not compost).
Since then, I’ve been keener than ever to make my own compost – from either garden waste from my garden or my neighbours, or from the one local farm I know that doesn’t use herbicides.
After all, when you make compost you know exactly what is going into it.
Even then, unless you are extreme, it’s unlikely to be 100% organic. In my own compost, for example, I use tea bags (which often contain tiny amounts of plastic) and seaweed (likely to contain some heavy metals).
But at least you have control over what’s going in.
For information on doing your own composting, see our Home Composting Guide.
What’s the best ‘organic’ compost to buy?
While I highly recommend making your own compost, the reality is:
- It’s difficult to make enough compost.
- Some people don’t have the time to make compost.
So the majority of gardeners have to buy at least some compost.
As we’ve seen, buying organic compost can be problematic. However, there are some excellent peat-free composts, some of which also label themselves as organic.
Ethical Consumer has rated a number of peat-free composts. (Do note that their recommendations are based on the company practices, rather than product testing.)
This small composting company is run by a farmer and an environmental scientist, so they should know something about soil fertility!
They’re the only compost company I could find which is listed by both Ethical Consumer and the Soil Association.
Made on a traditional hill farm in the Lake District, their peat-free compost uses bracken, which is rich in potash, and sheep’s wool for improved water retention.
(Apologies to US readers – this section is UK based, as I have had difficulty accessing research focussed on US compost. If you know of any, do let me know!)
Other options include:
- Fertile Fibre peat-free organic compost
- GroChar peat-free compost
- Miracle-Gro peat-free compost
- Eden Project coir compost
- Vital Earth peat-free compost
One of the problems I have with organic compost is its very name.
The term organic implies it is special, when in fact all compost is organic. It also feels a bit disingenuous that some ‘organic’ compost contains peat.
If you are concerned about the environment, I would suggest searching for peat-free compost. I’d also look for compost which, where possible, has been certified by a reputable organisation such as the soil association.