Derek – Friday 27th November 2020

The first compost bin I made, over 30 years ago, hadn’t been thought out. It was square with wooden posts and plastic sheet for sides. When nothing much was happening, I added lots of water. The result was an awfully smelly mix, like liquid sewage. So, having failed, I read up on composting to get it right the next time round.

What I was getting was anaerobic action. Anaerobic means without oxygen; it’s slow and it’s smelly, the bacteria involved giving off hydrogen sulphide, that rotten eggs stink. No way to get on with the neighbours, and no good for the garden either.

So after that failure, I took advantage of the leftover dustbins when we switched to wheelie bins in the 90s. There were three dustbins, and I drilled holes in them at various levels to let air in. I started putting vegetable waste from the garden and kitchen into the first bin. I am a vegetarian, so there was no meat. Also no leaves from trees, as they went into a separate area to become leaf mould. I limited the amount of wood and paper, and every foot or so, added a dusting of fertilizer. In the summer months, when the bins got dry, I would add water, but not too much as soggy waste excludes oxygen, which will result in a smelly, slow heap as I’d learnt.

This instance, it worked like a dream. By the time all three bins were filled, the first was done, full of a beautiful brown compost, looking like a rich garden soil. Compost is not soil, though. Soil, in addition, contains minerals and broken down rock particles. Nor is compost synonymous with fertilizer. If you have added fertilizer or manure to speed up the process, then your compost will be richer. Not otherwise. By adding compost to a bed, you are adding humus to the soil, helping it retain moisture. If you are using it alone for potting, and it hasn’t been enriched, you’ll need to add feed or the plants will suffer.

You will have noted, I put waste cooked food in my bins. Many commentators decry this, but it worked for me. In my opinion, it is OK if your compost bin has a base, rather than the composting material resting on soil, and the bin has a firm lid. If not, don’t add waste cooked food or rats are a possibility.

I used fertilizer. You don’t have to, but composting will be slower without it. The nitrogen in the fertilizer speeds up the process. There is some nitrogen in plant waste, but not a lot. An alternative to fertilizer is manure. Every foot or so, add a few spadefuls. Additional nitrogen is essential if you have quite a bit of wood in the mix (or paper/card which can be regarded as wood). Wood is mostly carbon and is slow to break down in the absence of nitrogen. A figure often quoted is a 30:1 carbon/nitrogen ratio, which makes me scratch my head, as how do you know without going to the laboratory?

Making compost is pretty rough and ready: not too much of anything, break wood into small pieces, make sure the mixture stays damp (but not soggy), keep it airy and add nitrogen if you want to speed up the process. You are attempting to create an environment where the composting bacteria are happily munching away at your waste. Apart from oxygen and water, they need nitrogen to make protein in order to reproduce. There’s likely to be some, but you can add more. Temperature is another important factor. In winter, it is too cold for bacterial action. As we get into spring, the bacteria liven up and composting gets going. It is at its maximum during the summer months.

The chemical processes are exothermic, which means they give off heat. A large, steaming heap could be as hot as 75°C. That will kill off pathogens and weed seeds. Small bins don’t get this hot and you’ll have to live with the weeds and pathogens.

The alternative to composting is putting vegetable garden and kitchen waste in the dustbin where it will end up in landfill. And there, in an environment short on oxygen, as it breaks down it will give off methane, a greenhouse gas 28 times more powerful than carbon dioxide.

The argument is simple, and the process not arduous. By composting we add humus to our soil and cut back on damaging emissions. Our dustbins become less smelly, less attractive to rats, and they don’t need emptying as often.