Seven steps to perfect compost

Ben Raskin - 07 May 2014

This week is National Composting week, which gives me the excuse to talk about one of my favourite subjects: compost. There’s something magical about the way that scraps and waste fruit and veg can turn into sweet smelling and nutritious crumbly brown soil food. And the best thing about this natural process is that you can do it on any scale – from municipal composters handling many tonnes a week to small compost bins in our houses. Here are my seven steps to perfect compost:

  1. Keep your eyes on the prize. This might sound a bit obvious, but make sure you’re regularly having a good look at your compost heap. By keeping tabs on its progress you can begin to understand the process it takes, and start to spot when it needs some help to keep it happy – an extra turn if progress has stopped, or a bit of water if it has dried out.
  2. Think of your compost heap like a cake. Too much of one ingredient will spoil the recipe so it’s important to get the brown:green ratio right. Green material (kitchen waste, grass cuttings, weeds) has lots of nitrogen giving short term energy, but no structure. Brown material (woody plants or chips, cardboard, ashes) has more carbon which helps with structure, but breaks down more slowly, so too much will stop your composting in its tracks. If you find you’re composting mostly kitchen waste, then try adding cardboard or shredded paper to balance your compost cake out! Although it depends a little on the material 50:50 brown:green should be about right.
  3. Beg, borrow or steal. Getting hold of the right ingredients can be tricky, particularly if you live in a city, but if you're really determined you can find them. Cafes now often give away their coffee grounds which have lots of both phosphorus and potassium (great for growing tasty fruit and veg), and there's always cardboard going spare from shops to bulk out the carbon element of your compost. Personally, I take advantage of my colleagues high levels of (organic) coffee and fruit consumption to collect the organic waste from our office to feed the soil on my allotment.
  4. Swamp or Sahara? You’ll need your compost heap to be not too wet and not too dry, but just right. This is mostly related to how much green or brown material is in there – if you've got the balance right you shouldn't have too much trouble (see compost cake above) – but looking at moisture levels is a good guide to how your compost is doing generally. As a rule of thumb you want the pile to be damp but not wet.
  5. Patience is a virtue. As long as your compost heap is covered, keep it maturing for a long time. The longer compost matures the more stable its chemical structures become, and as research presented at our Soil Symposium last year has also shown; more mature compost has an increased effect in suppressing plant diseases.
  6. Small can be beautiful. Even if you don’t have a garden don't despair, you can still harvest some nutritious compost – there are plenty of home compost and wormery systems available that can be installed on a kitchen side. Last week saw the arrival in the office of a desktop wormery to trial with a glass side that allows you to watch the process as it happens – great for kids and we are hoping that we might get some nice food for our plant pots if the worms can survive the warmth of our working environment.
  7. The icing on top. Once your compost is ready, a small amount of the sieved compost applied as top dressing for potted plants is the best way to keep them healthy (though it may well keep the weeds a bit happy too)

Whether as a composter you're a spring sapling or a hardy perennial I hope you've found these tips useful – let me know what your best composting tips are in the comments below.

 Ben is Head of Horticulture at the Soil Association. After discovering the outdoor life on an organic vineyard in Northern Italy, and a one year professional gardening course at Lackham College, Ben has worked in horticulture for 20 years. Previous incarnations include running a walled garden in Sussex, working for the HDRA (now Garden Organic) at their gardens in Kent, setting up and running the horticultural production at Daylesford Organic Farm, before moving to the Welsh College of Horticulture as commercial manager. Ben is passionate both about the commercial production of high quality organic vegetables and teaching practical skills to all ages through on farm learning. Ben set up the Soil Association Future Growers apprenticeship scheme and is also the author of Compost – a family guide to making soil from scraps

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Richard Higgins
12 May 2015 07:56

Richard Higgins runs his Superfast Composting course towards the end of every month see This course is held in South Hertfordshire.Ben I don't have your email for sending you info on Rothamsted

Ben Raskin
17 March 2015 11:36

Also following the discussion about whether to work out ratios as carbon :nitrogen or brown / green I have amended original post to describe in terms of brown and green, as that is an easier way of thinking about.

Ben Raskin
17 March 2015 11:33

Hi John only just seen your comment - sorry. One thing you could try - which my Dad used to do - is the Dig and drop composting. where you dig a hole in the ground and put you compost in there and then cover it with a layer of soil. You can either then dig it up again in a years time to spread or just move you hole around the garden.

22 August 2014 02:05

great article. living in an area affected by a severe draught. other than covering the pile - any advice to reduce or eliminate the need for watering?

Ben Raskin
19 May 2014 15:51

Hi Julia It does have some information on setting up a compost heap but as it is a book aimed at younger audience does not go into great detail, and I have only touched briefly on multiple bay options. However if you do still want to buy after that non sales pitch then it's available either from online retailers or you can contact me directly (either phone our switchboard or DM me on twitter @Ben_Raskin ) Thanks

Julia Hailes
14 May 2014 14:07

How do I get a copy of your book - Compost – a family guide to making soil from scraps. Does it include advice on setting up a compost heap? I'm about to install three for different stages of composting...

Ben Raskin
14 May 2014 09:23

Thanks everyone for you comments and questions, will try to answer then all in one post if that's ok?Angela - the more you shred or rip the cardboard the quicker it will rot, but mostly not necessary unless it's really thick. The bugs should break it up for youMilan (and Roger) - interested that you were advised not to use paper. I know inks used to be a big problem, but my understanding was that they are now mostly vegetable based and ok to use. i will do a bit more research to check the latest position.Peter and Dee - as Nancy suggests the 25:1 (or even 30:1) is the Carbon to Nitrogen ration. However your green waste will contain a significant amount of carbon, so 2:1 or 1:1 of brown:green may well give you that ratio, depending on the make up of your material. If you want to get very scientific about it (though you probably have more important things to do with your life) you can do more exact analysis of each material added - there's quite good method here, although being an American site not all the materials listed would be available in th e UK.Sarah - Chicken manure is generally viewed as green, it's usually high in Nitrogen. Others will depend partly on how often you clean them out and how much bedding is included. Some more information on different animal manures here Please do post again to follow any of this up, or to add more of interest. Love the bumble bee nest in the heap Derek!Ben

12 May 2014 19:32

Having composted for many years,I now have three bins and use in succession,I add shredded paper and carboard to green waste and shred tree prunings and cabbage stalks ect.although covered I always top my heap with several layers of carboard,after a couple of weeks the life developing under the carboard is amazing.I found a Bumble Bee nest in a bin last week,good news.

12 May 2014 19:19

I guessed the ratio was meant to read, in words for clarity, two-point-five to one but I would like confirmation of that. Personally I collect compost material e.g. peelings, in a kitchen caddy but always line it with the paper sacks/punnets that the organic fruit and veg service deliver in, and put the lining in the garden compost heap with contents every time. I also pop in every empty toilet roll, unsquashed to add airspace. Any extra plain paper bags from the market and flour bags from the organic flour go in too. Ours has worked fairly well for years on this regime; we haven't emptied it for several years and the apple tree whose roots are under it is now fruiting every year despite being nearly 70 years old and previously fruiting biennially. So there's a useful tip!

12 May 2014 17:27

Comfrey and nettles will speed up decomposition. Urine too and also contains a good source of phosphates

12 May 2014 16:22

Peter - I have seen the 25:1 ratio before, I don't think it's a misprint - but this is actually the correct chemical proportions of nitrogen to carbon for the composting reactions to heat up your compost nicely... quite how that translates to actual green stuff and actual brown stuff might be quite different - I would tend to agree with your 1:1 ...probably depends quite how green your greens are and quite how brown your browns...

12 May 2014 16:07

What is manure from hens, pigs, sheep, rabbits etc counted as; brown or green? We have an animal rescue and there is plenty!!

12 May 2014 12:48

The main issue I have is a lack of 'brown' stuff to put with all the green kitchen scraps but I'm a bit concerned about putting in cardboard and news paper because of possible chemicals that they contain. Do you have a view on this ?

Peter Freeman
12 May 2014 11:17

Surely the brown:green ratio is not right as stated 25:1? I guess this is a misprint as I normally advise between 1:1 and 2:1.

12 May 2014 10:49

In my composts I use freshly mowed grass and dry old grass, twigs of trees and shrubs and even larger branches, so my composts are paradises for spiders, lizards, even water snakes (they catch mice, so they are very welcome). However, I never use cardboard or any old paper as I checked that with a papermill and a printer and they discouraged me from using them in my garden because of the unknown mixture of chemicals (e,g. colours). The same actually applies for ashes of burnt magazines - though I have never had the chemical analysis done.

08 May 2014 09:38

I love the idea of thinking of my compost heaps as cake but when you say add cardboard, do you mean finely ripped up or in sheets? We do add all our shredded paper but should I be wetting it and the cardboard?

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