Composting cooked food waste

I got my first composting-related injury yesterday by bashing my knuckle against the wall while aerating my compost. If you can avoid it, please site your compost bin some distance away from brick walls. Unfortunately, I do not have that luxury, but I am now all the more tempted to purchase an aerator rather than making do with an old mop handle. Aerators, as the name suggests, help move the compost around to let the air circulate better. They do not ‘turn’ your compost as such, but do so more than prodding the heap with a long stick! They cost around £10 – £20 and are surprisingly effortless to use.

In my last blog post I looked at the conventional methods of composting. These are all well and good but when I first started composting they just didn’t appeal – as a standalone method, at least – because I couldn’t compost everything that could, technically (because it was once a living thing), be composted. My main concern was, and is, food waste. Obviously, I minimise this as much as possible but with two young children I cannot prevent it entirely and it does not then make sense to throw these no longer edible leftovers into the general waste when I am composting the rest of my kitchen waste. I cannot throw it into the compost bin because 1) it could attract pests and therefore spread disease, and 2) cooked food does not compost as quickly and effectively.

Fortunately, various methods for composting cooked food waste exist.

1) Wormeries

Worm composting – or vermiculture – creates a dark, crumbly, nutrient-rich compost as well as a liquid that can be used as plant feed (diluted 1:10). Worms – brandling/tiger worms, or night crawlers – feed on kitchen waste from one end of their body and produce casts – basically, worm manure – from the other end. These casts are the worm compost.

Wormeries come in two forms – tiered, stacking bins or a singular, non-stacking bin. The obvious advantage is with the tiered bins as this makes it far easier to harvest the worm compost because you do not have to disturb the worms. Wormeries are possibly the most varied of all bins, and can either be purchased (£40-70) or made yourself using an abundance of materials. They are also an ideal solution for anyone short on space – for example, someone who lives in a flat without a garden can produce compost inside and use this on any pot plants they may have. Wormeries are actually well-suited to indoor composting because worms prefer the warmth. And besides, it’s rather like having pets.

So, what can you put into a wormery?

The usual: veg and fruit peelings (but avoid citrus peel and onion peelings as the worms do not like it), crushed egg shells, tea leaves, coffee grounds, kitchen paper, shredded paper, egg boxes, toilet rolls, cut flowers.

The unusual: leftover cooked potatoes and other cooked vegetables, leftover rice and pasta.

Avoid: citrus fruit and onion peelings, meat, fish and dairy products, dog/cat faeces, diseased plant material, non-biodegradable materials.

Like conventional composting, remember to make sure there is a mix of greens and browns so that the bin doesn’t get too hot or wet (you don’t want to kill your worms!)

I would love to have a wormery and sometimes I think I should have got one of these before getting my bokashi bins, but we get through a lot of citrus fruit in our house, and a wormery does not solve the ‘all food waste’ problem. It is a good solution, however, if you only want to make a small amount of compost.

Bokashi bins (£20-£60 + bran (about £20 for a year))

Bokashi isn’t actually composting because it is an anaerobic process of fermenting food waste so that it can be safely composted. It uses a special bran which contains effective micro-organisms. Raw and cooked meat and fish (including bones), dairy, bread, and all other forms of cooked food can be placed in the bin alongside vegetable peelings, coffee grounds and tissues. It has been bothering me as to why manufacturers do not advise putting tea bags in so I (finally) searched for an answer – it is because the effective micro-organisms that are an essential part of the bokashi process do not work properly if the waste is too wet. The solution is to ensure teabags have dried out before they go in.


The process:

Each time you put waste into the bin you have to sprinkle it with bokashi bran and squash it down to let out any air, then reseal the lid. There is a tap at the bottom where you drain off excess liquid (this can be diluted 1:100 and used as a weekly plant feed, or – it is this potent – for keeping your drains clear and fresh). It is best to have two bins because when one is full you need to leave it for 2-3 weeks to ferment, in which time you start filling the next.

On the face of it, bokashi bins are an ideal solution for anyone with minimal space who is interested in managing their kitchen waste, but the key problem is: you do not produce compost and so you still need somewhere to dispose of it. You can either add it to an active compost bin (with lots of browns!) or bury it in a trench. But you need the place to do this. I have read about universities (mainly in the USA) where they have communal compost bins, which students are able to add bokashi-treated waste to, but in the UK at least there are laws relating to community composting and what can then be done with the resultant compost, etc., so this might be more complicated to initiate. (A blog post for another day, perhaps.) Overall, I’m still in two minds about bokashi composting.

Trench composting5430765694_79edaafb69_z

A brief mention here as this is one way of disposing of bokashi-treated waste, but likewise useful for fruit and vegetable waste from kitchen and garden. In this method, you are burying your waste so that when it decomposes it adds nutrients to the soil. Trench composting is best done over the winter and early spring so you can then grow on that spot the following summer and reap the benefits!




hpp1Green cone (£85)

If I had a garden with a fruit tree of some description, I would have one of these. Green cones are basically food digesters. Because they are fully enclosed you can dispose of raw and cooked food waste, including meat, fish and dairy. You do not get any compost from the green cone, but if you site it by a fruit tree, for example, then this will benefit from the nutrients entering the soil.



Next post: the all-encompassing super-compost bins.



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