What is municipal compost? How can you use it in your container growing? Is it safe? And is it the answer for the urban grower looking for a good quality, sustainable growing medium? This post will try to answer these questions. My next post will answer more of your questions about municipal compost, posted on Twitter (thanks for all these).
Why sourcing compost is a BIG issue (particularly in cities)
The practical reasons
One of the hardest choices to make when building your container garden is: which growing medium to use. There's quite a bit to consider. Which will perform best? (And performance does vary hugely). Where do you get it from and how do you shift it? (Particularly if you don't have a car - I broke two bike axles last year by overloading bike panniers with compost!) And of course there's the cost.
The environmental reasons
Then there are wider issues. Many growing media sold in the UK still contain peat (unless the bag explicitly says 'peat free' it probably contains peat). This is a problem because peat extraction releases greenhouse gases and damages precious habitats. A separate issue is that many growing media are transported long distances, with associated emissions and fuel use.
Is municipal compost the solution?
Can municipal compost offer a more sustainable solution? Made from food and green garden waste (like grass and hedge clippings from gardens) it reduces landfill, recycles organic material, and is locally sourced and made. It's also usually available free or at low cost. But is it any good for growing in containers? And how reliable is it and how safe is it?
I went down to the LondonWaste EcoPark in North London, which produces 12,000 tonnes of compost a year to see it being made and to look for answers.
How is municipal compost made?
Food waste and green waste from gardens - grass and hedge clippings, prunings - is roughly shredded (to a width of 400mm) and then mixed with a small quantity of compost activator (contains micro-organisms and enzymes to promote efficient composting). This mix goes into a large, enclosed tunnel. Fans under the floor, blow air through the waste. The pile heats up as it begins to decompose, and the temperature is carefully monitored with probes. It must reach 60 oC for at least 48 hours so that pathogens and most weed seeds are killed. After a minimum of one week in the first tunnel, it is turned and transferred into a second tunnel, where the process is repeated. This helps ensure that the materials are thoroughly and evenly composted. The compost is then transferred out of the tunnel, mixed with other batches (to help minimise inconsistencies between batches), and left to mature for several weeks. The final step is to sift the compost through a large drum - removing anything larger than 20mm.
Waste is loaded into huge enclosed tunnels, and air is blown in through vents in the floor.
The compost is made to the BSI PAS 100:2011 standard. This means the quality has to be regularly tested, including for heavy metals and other chemical residues.
How can you use it in Containers?
The compost from the EcoPark, like most municipal composts, is rich in nutrients. It is sold as a 'soil conditioner' rather than a potting compost.
Reusing old compost
It is probably most useful in container growing to help you re-use old compost. Rich in nutrients, it will add fertility. Also, as most municipal composts contain a high proportion of large particles, it may help improve structure. To your old compost, add between 20% and 50% municipal compost, depending on how rich a growing mix you want. As a rough rule of thumb you want a richer mix for fruiting crops like courgettes, less rich for leafy crops.
As a potting mix
To use municipal compost as a potting mix, the official advice is that one part compost should be mixed with three parts of a more inert growing medium like leaf mould or coir. The problem is that neither leaf mould or coir are very easy to get hold of in the city! The good news is that I know several experienced growers who grow in straight municipal compost - and do so successfully. My own (admittedly limited) experiments with neat municipal compost have also been successful (see image below).
These salads are growing in 100% straight municipal compost - and doing OK!
Experiment
So the best advice is probably to try experimenting with your own local municipal compost to see what works and what doesn't. (NB municipal composts do vary both from region to region and also, slightly, from season to season). If you do try it neat, make sure it has been left to mature for a few weeks first - as it will be too rich when fresh.
And watch the watering carefully: it can be prone to dry out quicker than some composts.
If you're interested, the nutrient levels in the Eco Park compost are typically (in kg per tonne): nitrogen (N) 13.86, Phosphate (P) 4.81, Potassium (K) 10.36, Magnesium (Mg) 3.48, Sulphur (S) 4.68.
How to get hold of it
Contact your local council to find out how it is distributed in your region. Large quantities (several tonnes) are often distributed free or at low cost. Smaller quantities are often available for sale in bags at local recycling centres.
But arguably the best place to find it in smaller quantities is from local growing projects. If they have received a big delivery, they will often be happy for local residents to bag up some to take home - either free or for a small donation. The challenge is to sniff out a supply local to you - good sources of information include local allotments, growing projects and websites like Transition Towns or Project Dirt in London. In Camden, London, Alara Wholefoods in Camley Street often has a supply it is happy to donate to deserving causes. This is a great service, that also engages more local people in food growing. Its an idea you could replicate if you or your community group have access to space where compost can be dumped and stored until it is collected.
Where it's distributed to in North London
The EcoPark in North London distributes 60% of the finished compost to agriculture, 40% to community groups and allotments. The normal delivery size is a whopping 15 tonnes, the smallest is 7 tonnes. Plans are afoot to introduce 1 tonne bags this year. This willl be a boon for smaller growing projects.
The Last Word
I leave the last words to John Walker, who is a enthusiast for peat free composts. See his excellent website, www.earthfriendlygardener.net, for very helpful trials of different peat free composts.
'My overall feeling is that if you can get municipal compost then it's worth using it somehow. That might be as a straight soil improver, mixed (after sieving) with leafmould to make your own potting mix, or mixed with bought-in peat free to make a rich mix for containers. I wouldn't recommend using it on its own in containers, unless you've done a test run and found it works (I think all gardeners should be having fun with their own trials, which would also help build a much clearer picture of how these 'municipal' materials are doing). Use it to complement other composts/materials because it helps reduce landfill and has a much smaller 'footprint' than say peat-based compost.'
He also advises against using it, 'straight from the bag - its going to get wet and slump and disappoint'. This advice highlights how municipal composts vary from region to region: I've used it straight from the bag and haven't experienced this issue.
So probably the final, final word should be: Experiment!
If you've tried using municipal compost in container growing - or experiment this year - it would be valuable to hear about your experiences.
Your questions answered.
Thanks for all your brilliant questions about municipal compost – and thanks to Wendy and Tom at LondonWaste’s EcoPark for answering them! For more info on municipal compost and how it can be used in containers, see my other post: Muncipal Compost: is it a good thing.
At the London Waste Eco Park, the compost is made from about 5% food waste, the rest is green waste (grass clippings, prunings etc). It varies a bit seasonally (less grass clippings in winter!) and from site to site around the country (eg some sites do not use food waste). Is it suitable for organic gardens? I spoke to the Soil Association about this and the answer is yes, probably. The official line is: ‘The Soil Association recognises that the use of green waste compost is compatible with the basic principles of sustainability and can be used as part of an on-farm fertility and soil health programme.’ However, if you want to use municipal compost to gain organic accreditation you’ll need permission from the Soil Association first. Most composts that have been tested to BI PAS100 will pass the Soil Association’s verification process – but the two tests are slightly different so its not 100% guaranteed. Some municipal composts in the UK have been verified independently by the Soil Association – check with your local producer.
I have experienced the same issue, too, Simon. Here’s what they do to minimize it at the Eco Park (it may vary in other places). The food and green waste is first inspected visually. Any loads that are badly contaminated are diverted to landfill. Then, after composting, the material is screened and anything larger than 20 mm is removed. This takes out all the larger impurities (eg plastic bags), although anything smaller that 20 mm will not be removed. I tend to sieve all my municipal compost at home to remove these smaller bits.
See above for the answer to the first part of your question, Vanessa. In answer to the second part: yes, as part of BI PAS 100 Standard (which this and many other municipal composts meet), every 5000 m3 of the compost is tested for both chemical residues and heavy metals.
Nigel, the pH does vary slightly. Usually it is 7.5, but seasonal variations in the green waste collected do affect it. For example, in January, the composting of Christmas trees can make it more acidic – perhaps as low as pH 6.
Yes, Elaine, the compost is independently tested for herbicidies – this is done by sowing tomato seeds in samples of the municipal compost and comparing to tomato seeds in a control compost. The germination rate is compared and the seedling growth is monitored. If the tomato leaves curl, this is an indicator of herbicides. You should be aware, though, that it is impossible to detect herbicides in the green wastes coming into the site. The tests are run once on every 500o m3 of compost, not every bag . So the risk of herbicides being present cannot be removed completely. But as the London Eco Park has passed every herbicide test done to date, this risk is presumably pretty small.
Julieanne, you are doing the right thing! Common weeds like couch grass and bindweed will be killed by the high temperatures in the process. The exception is the pernicious and dangerous weeds like Japanese Knotweed which should not be put out for council collection.
Hi Mark, We've been using undiluted North London Waste Compost for our community veg growing project for the last 2 years (and agin for this coming growing season) and have had great results for all sorts of veg growing. Great for runner beans, courgettes, rhubarb, nasturtiums and tomatoes and we will be trying out carrots and parsnips this year too.Very interesting post. Thanks again. Naomi
Thanks for sharing your experience, Naomi - very interesting and useful to hear your experience. I know quite a few people now who are growing directly in the North London Waste compost, undiluted. It'd be interesting to know if people from other boroughs / regions of the UK have had similar experiences. Anyone?
Here at FOOD from the SKY we have used more than 15 tonnes of municipal compost from Haringey. It is rough, rich and very dark with large bits of wood and sometimes we found knives and forks as well as glass bits. We use it seeved for young plants and on the top of our groing container. The compost that was left for few month was fabulous and if you have time it is worth letting it rest and increase its leaf mold and life organisms have time to move in.
W ehave grown food, herbs and flowers in the boxes for almost 2 years now. We top up evry few months with new compost as well as feeding with all sort of organic fertilisers. We also had biodynamic solutions spread on the whole roof few months ago. Great stuff as it is local, rich and free. I would recomend to add some sand and leaf mold for seeding and seedlings and some top soil for more mature plants if you can.
Happy growing, thank you Mark for inviting me to write here, very interesting and valuable post!
xx
Azul
Thank you, Azul, your learning offers valuable information - and inspiration. Congratulations on creating such a vibrant and productive garden from London's waste! Very interesting how you've found it improves with time - also to learn how you keep it fertile - and the tips to adapt it for different uses in the container garden. Thanks for so much for sharing! Mark
Hi Mark, I've enjoyed reading this. We've used Camden municipal compost from the start as it was cheap and readily available. It was bought in bags from the recycling centre and used neat in our raised beds. Three years on, the compost has been taken down into the bark chippings, topsoil and clay that was under the raised beds. I top up each year with more and have always had excellent results across my varied crops. I also use it for container growing on my balcony, again with great results. It's not all used straightaway so is left in bags until needed. This bagged compost was relatively smooth and a good choice while still available. I'm now using compost donated by Naomi (above comment) which needs to be sieved as it has large twigs, glass, bottle tops etc in it. Looks quite good though so the effort should be worth it. Interesting to hear feedback from others as well!
Great post Mark,
Lewisham Council hand off their collected green waste to a parks management company who in turn sells it to a large composting company.
Ive been lobbying for Lewisham Council to make some of this municipal compost available to residents, but they refuse.
Its residents own waste after all. I may start a bit of a campaign!
Good plan! It might be worth talking to North London Waste Authority - quite a lot of their compost goes to agriculture but they are trying to get more of it going back into the community. Eg they are reducing the minimumm delivery size and holding events to raise awareness of composting in the community. Let me know if you'd like a contact name there.
I know that in the U.S. municipal compost contains Sewage Sludge. This is a highly toxic waste which is being disguised as garden compost. Check and make sure your town or city is not using its sewage sludge to enhance its compost.
I work for Camden Council and have been helping groups access the municipal compost. Alara (the muesli company) on Camley Street behind Kings Cross gets it delivered in the 15 tonne loads to the front of their premises (where they also host a community garden - with a permaculture forest garden out the back!), and it is free to take for anyone who can cart it away.
The first time I got some was with a new community gardening group I was helping. I must admit it stank! I got a bit for myself - not much as I had to wheel it home - and I took the back roads home to avoid bumping into anyone, they'd smell me before they saw me!
I'm happy to say the compost stopped smelling after a couple of weeks although it lingered on my gardening gloves for a lot longer. I just used it as top dressing on my plot, but I've been to the new garden where it was used neat, and the plants there are thriving.
I've since been back to the "smelly pile" (as we now call it) and the compost there now smells much less offensive.
I also understand that it is (or soon will be) available in bags from the Regis Road recycling centre, at a low cost to cover the cost of bagging it.
My first thought when reading about using municiple compost is that it will contain residues of herbicide and pesticide from the garden and food waste of many people using these substances.
This article is really interesting. I've just bought West Country compost, our local council compost provider and it is lovely stuff - nice and dark and rich. The big disappointment though, is the amount of plastic I've found in it. It really shows how much plastic is out there in the environment polluting everything.
Hi, I live in Catford and contacted North London Waste Authority yesterday to enquire about getting a load (7 tonnes) of compost. They said they could only deliver to north east London. It is not possible to get municipal compost in south east London it seems.
Hi Martin, Mmm, I've heard of others in South London with the same issue. Might be worth you getting in touch with Anne-Marie at Lewisham Gardens (http://lewishamgardens.webs.com/) as I know she was looking into it and seeing if the council would do anything about it. Good luck! Mark
Our local municipal compost in Croydon is excellent despite the cringe-worthy name Croypost. I grow hundreds of herbs to sell and use it mixed with one third homemade compost (we have chickens and ducks) and one third Horizon organic. Brilliant results. Also my best ever crop of garlic on my allotment was in a deep bed topped with 15cm of Croypost. Only hiccup was a crop of Judas Ear Fungus one year.
What is cheap about recycled household waste at £3 for a 30 litre bag?
http://www.londonwaste.co.uk/ecopark-compost-for-sale/
It's cheaper to buy it from a DIY? superstore, even though they sell it at rip off prices...
Depends where you get it, Tony. Community growing sites in London will often get several tonnes delivered for free for at low cost, and then give it away or sell it a very low price. For example, Alara Whole Foods on Camley Street in Camden often has a stash that people can help themselves to - you just need to leave your name and address so they can track where it is going. You may need to ask around a bit to find low cost source or persuade a local growing project to get a large delivery that can be divvied out. I can't remember the cost per tonne but I think it is about £20 which is roughly equivalent to 25p a bag.
I'm going by the sack price they quote, Mark, on their web pages. If they can deliver a ton for £20, I'd buy 1 for my plot. Who would you suggest I call for a ton delivered to a plot in Ealing?
Ah, I think the catch might be that you need to order several tonnes in one go... might work if you can get several people on your allotment to club together? I'll email you a contact number for the site.
Does anyone know if municipal compost is available near Cranbrook, in Kent?
Sure there's lots of horse manure round here, but it has rarely heated up enough to kill the weed seeds, so I'd prefer a 'cooked' compost.
hi Tony, i wonder if you manage to figure out about the tone of compost for your Ealing plot? I am in need of 2 cubic meters of compost ( not sure how much of a tone would that be) for rised veggie bed in a garden in Ealing, but can't find much of any information about it how to get it in Ealing area. any suggestions would be appreciated :)
Hi Daria, I gave up trying to buy it from councils - way too expensive.
Much easier to go here and get horse manure for free (its smelly by rewarding):
http://www.ealingridingschool.net/
Regards,
Tony
Dear Azul,
You seem to have good experience.I have access to both leaf mould & freshly made council compost.I am soon going to plant in 1.pots.2.Beds at home.3.My allotment. Please advise how best ,combinations,ratios,to use these two items.Thanks
Anil
Thanks Tony, may use the manure for autumn or spring feeding. I manage to find out Camden council is much more generous with free compost, and you can get it through muesli company Alara. Bit far, but free. They get 25 tones every so often. Very smell, particularly when fresh (we got it on the next day after delivery) and unfortunately has a lot of plastic, mainly foil mixed in it, which was annoying to remove. But mixed with our clay from the garden should do good, potatoes grown big and flowering, will see soon if any spuds are there.
The quality and control process varies hugely depending on where and how it is made. Some places do it very well, some very badly. In the UK, there is a standard, PAS 100 that some places sign up to - to pass this, the compost has to undergo regular testing, including on heavy metals - so (in theory, at least) it should never be strewn with bits of metal (although bits of plastic can still be quite common in my experience). Bottom line: if you really want to know what is in your compost, make it yourself.
I am filling in my pond to create a bog garden and have calculated I need 3.82 cubic metres of soil. Having done that calculation, I find myself confused as to exactly how much soil that is. Some companies measure in litres and some in kilos. I have considered council created compost, but hesitate because I am not convinced it will be free of weeds. Having read the article I suspect I should mix it with other soil (not necessarily top soil). Any helpful advice would be gratefully accepted.
Re Municipal compost. I have been using it for more than ten years and think it's great, particularly for hanging baskets, containers and summer bedding plants. Originally I was so ignorant I only diluted it with soil when I was running short of it. I'm a great believer in 'if it works, keep on doing it.' It works so I still do it, even though I've now read it is better used as a soil enhancer rather than 100% growing medium. Never had any problem with weeds from it. Sometimes find it is still warm from composting and I keep that for a few weeks before I use it. Sometimes I found white dust patches in it, a bit like wood ash. Never used that on vegetables but it never seemed to do the flowers any harm. I think it is better than a lot of compost sold in bags at garden centre with the added advantage of being free.
I'm so disappointed in my council for no longer providing municipal compost to residents.
Many years ago it did (organised a few days where you could fill your bags) but no longer does, they sell it all to processors and I think it's one of those little things councils should really be doing for residents. It encourages local production of food/minimises emissions not to mention the environmental damage that can be done by forcing people to buy commercial compost in single use plastic.
I've been thinking of trying to get a campaign going to get my council providing this product to residents again.
That's a shame Ian, it's great to be able to get locally made compost. I'm guessing that with the phasing out of peat municipal compost has become a more valuable and sought after commodity. So the council may have found they can sell it and use the proceeds to fund other work. It might be interesting to find out if that's why they stopped selling it or if there are other reasons.
In Northumberland you can buy bags of this compost at the council tip for £4 a bag - it is so heavy I can't lift it, at least 1.5 times the weight of a bag of Multipurpose for about the same price, so good value. They are not allowed to call it "compost" - they call it "soil improver." Frankly I don't mind paying for it. I have been using it to put a top layer when making no-dig beds, i.e. cardboard, one layer of old horse manure, one layer of home made loam, one layer of my own compost and the "soil improver" on top.
Sometimes when it is very heavy it's because soil is mixed in with it (people aren't supposed to put soil in their green waste bins but sometimes it gets into the mix). Whether this is a good thing depends to some degree on the quality of the soil. But the weight might, as you say, just be due to the size of the bag - I've bought those bags in Northumberland before but not for a few years now. I found it very variable in quality on the occasions I did.
Municipal compost that has the PAS 100 standard (always look for this standard when buying) has various quality controls that help ensure it is safe to grow in. It is also illegal to dispose of Japanese knotweed in green waste - and so, in theory at least, it should never be present. There is also evidence that Japanese Knotweed is killed in hot composting processes - and from what I can tell, the temperature that needs to be maintained to make PAS 100 compost is high enough to usually kill it - see for example this paper:http://www.organics-recycling.org.uk/uploads/article2149/Can%20composting%20kill%20Japanese%20Knotweed%20Version%202.pdf. I doubt that this guarantees that Japanese knotweed is never in municipal compost - and I can't find any reliable statistics on the matter - but the risk should be very small from what I can tell.
Hi,
My landscape gardeners have just rotavated 5 huge bags of "compost" from my local council green bags. To begin with as it rained every day I thought it was great. Then the problems came as we dried out. Some of the soil must have washed out, and I was left with a litter of plastic chips from discarded plant pots, broken china and glass (up to 10 cm across - so not being filtered properly), pieces of electrical cable, etc. It is mainly now a pile of wood. Twigs up to a finger's breath across a dry surface that looks like dead grass and a film of something white that resembles sand. I planted 170 plants in a huge bed. All the plants with a 5 litre pot from the garden centre look normal. All the smaller plants I raised myself, the bulbs and dry rooted plants from dealers, are in trouble. Many bulbs have not sprouted. Plants are dying and those that survive have yellowed leaves. Can anyone tell me if they have similar problems? We are in Oxfordshire. My supposition is that there is herbicide remaining or that the composition of the compost is not conducive to plant health. Before the gardeners put this in we had a beautiful dark loam.
oh dear, David, I am very sorry to hear your experience. Green waste compost tends to be a very variable product and it is not uncommon for it to have an imbalance of nutrients - and this is the most likely cause of the yellowing leaves (although herbicide can't be ruled out), probably a lack of nitrogen. I've seen this on a number of occasions, including at a community garden in Newcastle. However, it really should be checked and sieved to remove the majority of the impurities, particularly the larger sized pieces of china and plastic you talk about (these couldn't have been buried in your garden already and brought to the surface by your gardeners? Just asking as our small garden is FULL of builders rubish below the surface). It might be worth checking with the gardeners to see where they sourced the compost from and to what standard it was made - and at least reporting your problems in nothing else.
Waste is loaded into huge enclosed tunnels, and air is blown in through vents in the floor.
These salads are growing in 100% straight municipal compost - and doing OK!
Waste is loaded into huge enclosed tunnels, and air is blown in through vents in the floor.
These salads are growing in 100% straight municipal compost - and doing OK!
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