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Can compost be truly organic? Part 1

What’s in the earth in your garden? Do you make your own compost, or buy bags of ‘organic’ growing media from your garden centre? What about potting soil? March and April are busy months for the vegetable gardener, and those of us keen on keeping their gardens organic will probably turn to one of the bags of ‘organic’ growing media available from our local garden centres, especially when seed-planting time comes around. However, their contents may not be quite as…organic…as the printing on them suggests.

New Horizons

‘Organic & Peat Free Compost’ from New Horizons, for example, is a peat-free growing medium that contains composted wood and coir, a material made from coconut palm fibre. Coir is a renewable resource although the distance it has to travel to get here, and the energy involved, calls its use into question. However, unless someone has decided to waste money spraying their coconut palms, it’s organic. Peat is not a renewable resource and its use should therefore be avoided. So far, so good: it’s compost, and it’s peat-free. But what about ‘organic’?

The New Horizons mix varies slightly from year to year as can be seen simply by opening a bag and examining the contents. While the nutrient levels and other factors may not fluctuate, its appearance can be quite different. This year, for example, there are a large number of light-coloured wood chips – more of which a little later.

You are also likely to find flakes of paint, chipboard and fragments of both plastic mouldings and bags. These are hardly organic in terms of gardening standards unless you take the stance that wood products are organic simply because wood comes from trees, and plastic is organic because it comes from crude oil, a naturally-occuring material.

non-compost, image

All these bits of trash - with the exception of the penny, added for scale - came from a bag of so-called 'organic' compost

A spokesperson from the technical department of William Sinclair Horticultural Ltd, the manufacturer of New Horizons, provided the following information:

New Horizons is basically a mix of composted wood and ‘green compost’ which comes from the ‘green bins’ found at recycling centres nationwide. Nutrients, in the form of blood and bone meal, are also added.

The company is aware of the light-coloured wood chips, considers them to be a problem, and has been trying to find some way to darken them. Despite appearances, they say that have all been properly composted. However, they still look and feel pretty much like the wood chips left lying around after a session of log splitting. Composting, as anyone who has made their own can attest, generally breaks down the raw materials involved (garden clippings, kitchen scraps) making them completely unrecognisable, or almost so – but not in this case. Most people, faced with an end result that looked very much like the beginning, might well consider the process to have been incomplete.

Quality control

Every load of materials arriving at William Sinclair is put through a random ‘box test’, and every load of green compost is checked by a laser scanner called ‘Hawkeye’. Suppliers are graded according to an accreditation initiative called ‘PAS100’. This is a voluntary rather than mandatory certification which sets minimum standards for composting, such as the temperature and materials which can be used, and checking for heavy metal levels. It is not specifically organic. If non-compost material is found during the PAS100 check, it is removed and tracked back to the supplier and can therefore count against their PAS100 rating.

So, William Sinclair are clearly doing their utmost to improve the quality of their product. The problem – for us – is that the material supply itself is fatally flawed, as we will see in the next article in this series.

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8 Responses to “Can compost be truly organic? Part 1”

  1. Andy McKee says:

    Some of the elements of this article appeared in the blog a few weeks ago, but since then Mark has uncovered some surprising information. Stay tuned :)

  2. Ingrid Glendinning says:

    I too have had problems with New Horizon compost. For the last 3 years my husband and I have used it to grow chillies, basil and coriander in the house, on the windowsills.
    The planst always became infested with aphids and in spite of spraying with soapy water/showering the plants down, the aphids came back strong and we lost all our plants during the 3 years.
    Last year, I decided to buy some reclaimed peat compost and grew the same plants in this compost. Not a single aphid in sight and lots of healthy plants.
    I emailed William Sinclair, Kitchen Garden and Garden Organic about my findings plus went to the KG forum. Nobody believes me, they all say that it was coincidence and that the aphids landed on my plants from outside.

    But after reading your articles in Home Farmer, I am truly convinced that there is a problem with aphid eggs in the raw materials (probably the recycled garden waste) of New Horizon composts.

    Until they improve their product, I will not buy peat free again, as I have had the same problems with other brands. It is a shame that this is not recognized and taken seriously as it is not helping the peat free “cause”.

    • Andy McKee says:

      That’s interesting. I did a quick bit of research myself and aphid eggs should really all be killed by the temperatures of commercial composting – hence the general scepticism, I think. I’ve been growing in New Horizon compost for years, so I’ll count myself lucky not to have had the same problem.

      Because chillies are so prone to aphid attack you always need to keep a close eye on them. Keep a close eye out for trouble, and if you see even one, knock it off with water from a hand spray. Then look carefully through all your plants in case it’s not alone!

  3. Mark Gatter says:

    Hi Ingrid,

    Interesting that you mention aphids…Two years ago I started several peppers, aubergines and tomatoes indoors under lights in January, in pots filled with New Horizons. The pots had been washed and stored at the end of the previous season and the cupboard was a ‘flat pack’ wardrobe that was bought the previous autumn. So, you’d think aphids were nowhere near. However, the developing aubergines in particular began to display leaf damage, and then the peppers. When I checked, there were loads of aphids. I couldn’t really believe that they’d come from the cupboard or the pots, and it was totally the wrong time of year for them to be coming from outside.

    I tried it again last year, this time in February, and the same thing happened. It wasn’t a ‘scientific’ test so I can’t prove anything, but I suspect that some degree of contamination is happening after the composting process is complete. I started to look more closely at New Horizons, and the result was the articles you’ve found on FIMP. Aphids may just be the tip of the iceberg!

    • Ingrid Glendinnning says:

      Hi Mark,

      phew, I am glad I’m not the only one with this problem. It seems to be indoors especially. It is so frustrating when nobody believes you. I am now 100% convinced that the aphids come from the compost, either because it is not properly composted (as your pictures show) or not enough heat built up during the process or that New Horizon (William Sinclair) have not sterlized it well enough.
      When you go on their website, they do say that they used “screened” green, composted waste, but nowhere does it say that it is sterilized.
      I bought a bag of Levington, peat besed, for my plants this year, only to find that they have now changed the composition of their product and it now includes composted bark too. I almost expected the same problem again and was worried. But I shouldn’t have worried as there was not a single aphid or fly that hatched. So, it could be that they use a different processs or higher temperatures, who knows. There is definetly something wrong with recycled council waste in these products and they get away with charging for the product when it contains things that should not be in there.

      I was like you, I initially thought the aphids were coming from another source, dirty pots, outside etc. But after 3 years, clean or new pots but using the same compost, the problem was the same.
      I feel really bad using peat again, but at least it is only a very small amount for indoor use as outside I use my own homemade compost.

      • Andy McKee says:

        Now you’ve got me really nervous, since I just potted my chillies on yesterday! So far as I know no compost manufacturers sterilise their product – they trust the composting process itself to kill all the nasties. Of course, the maturing compost sits outside in heaps and there’s nothing to stop hitch hikers climbing aboard at that stage. Which is probably why my polytunnel is full of crickets today…

      • Mark Gatter says:

        Hi Ingrid,

        Have a look here: http://www.westridingorganics.co.uk/growing-media/
        This was the ONLY truly organic soil amendment that I found that’s commercially available. All the others…weren’t truly organic as far as I could tell. And, the peat in this one is OK as it’s ‘recycled’, i.e. collected from lakes into which it’s been washed by natural erosion. Otherwise, and as you’re clearly aware, peat is not really the way to go and we should all avoid it whenever possible.

        I think that New Horizons is very likely composted at a high enough temperature to destroy aphid eggs, but that maybe it gets contaminated later in the process. It’s hard to say. Anyway, and just in terms of the ‘green bin’ inclusions, I’m avoiding it, too!

        • Ingrid Glendinning says:

          Hi Mark,

          yes, I have used Moorland Gold but it is extremely expensive. It is however the best compost I have ever used but I can’t sustain the price any longer as it would make for some very expensive chillies, basil and coriander.
          This was the first compost I bought last year when thinking about the aphid problem. I had no aphids etc. using this compost, and it has the most amazing texture and it great to work with. The organic gardening catalogue are the ones I bought it from and I can’t get it locally so the price from them is very high, probably due to shipping costs.
          My compromise this year is to use a small amount of cheaper peat based compost only for the house, one 60l bag for the whole year, only for the house. The rest will come from my own bins for plants outside.
          I do wonder how moorland gold pile their composts as there was no contamination from aphids, as I said above. There probably is no council waste in there either and peat is naturally more sterile than council compost.

          There is clearly still a lot of work that needs done before this issue is resolved.

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