So far, we’ve covered open composting in a traditional compost heap and composting with worms. In a wormery, we use a special type of surface-dwelling, non-burrowing worm to eat our waste and reprocess it into solid and liquid fertiliser. Traditional composting, as we’ve learned, is a collaboration between air and water, bacteria and fungi, and insects. The composting takes place in the presence of oxygen and the main workhorses are microorganisms that break down the sugars and carbohydrates, proteins and fats in the waste.
At an industrial level, anything that has ever lived can be composted. In fact, last year, Washington State in the US legalised the composting of human cadavers. You’ll get about a cubic metre of fluffy soil from a dead body, which I’ve been told is a great potting mix. There are also microbial and fungal applications being tested that will compost single-use plastics, like carrier bags and plastic film, which after all is derived from crude oil, which at one time used to be lots of little sea animals and plants swimming around in the Palaeozoic and Precambrian oceans of prehistory.
However, at a home and garden level, we’re limited by space and technology to composting the easier items, such as vegetable trimmings, spoiled fruit, and teabags from the kitchen, and grass clippings, old plants and leaves from the garden. We can also add paper and cardboard to that list.
But that leaves us still with a lot of waste to deal with. A recent survey reported that annual food waste in UK households, hospitality & food service, food manufacture, retail and wholesale sectors in 2018 was around 9.5 million tonnes. Seventy percent of which was intended to be consumed by people (30% being the ‘inedible parts’). This had a value of over £19bn a year and would be associated with more than 25 million tonnes of greenhouse gas emissions. Over 85% by weight of this wasted food arises in households and food manufacture.
That’s a lot of waste, and at a time when we are dealing with the twin crises of stressed food supplies caused by the Coronavirus lockdown, and unprecedented global warming caused by greenhouse gas emissions we can all do a bit more to limit waste and help the environment.
Some councils collect food waste from residencies. Tower Hamlets, my council, had a waste food collection service for some residencies, but this didn’t cover many apartments or flats (which at 83.2% is the majority of the properties in the area), and has since been suspended. As a result, most waste food went into black bags and landfill.
There is, however, a way in which we can compost all this waste food from our household and create a high nutrient fertiliser and soil additive, and that method is Bokashi fermentation. Bokashi will not only deal with vegetable cuttings and coffee grounds, but also compost difficult items like cooked food, bread, rice, pasta, meat, eggs, fish and dairy. This is because it composts material in a different way – in an oxygen-free, or anaerobic environment – and employing a different family of bacteria and fungi to do the work.
Bokashi is a bit more specialised than traditional composting, in that you need a very specific set of microbes to be able to do it (or else you’ll end up with a very stinky mess). Luckily, the bokashi microbes – called ‘EM’ of Effective Microorganisms, a specific set of anaerobic bacteria, actinomycetes, yeasts and fungi – are commercially available and have been inoculated into bran which can be purchased by mail order. This is the brand I use: <https://www.bokashidirect.co.uk/bokashi-bran/bokashi-bran.html>.
You will also need two pairs of buckets. These can be bought commercially <https://www.organiccatalogue.com/products/bokashi-kitchen-waste-composting-kit-2-buckets-container-and-1kg-bran-_783168?gclid=Cj0KCQjwy6T1BRDXARIsAIqCTXrH53jSBO9ERGd_De8KznD2Kl-EwTbHm8qduYqfzwKMdUesVX9cHVkaAqDdEALw_wcB>, but it’s often quicker and more cost-effective to make your own containers.
Basically, you need two stacking containers that have airtight lids. The top container has holes drilled in the bottom and is the one you seal airtight. This sits inside the other container, making an airtight seal. I use plastic popcorn buckets, as my kids always enjoy a movie night, I have plenty around the house. You’ll also need a plastic bag and something small like a saucer that can fit inside your top container.
You’re then ready to go. Put a 2cm layer of Bokashi bran on the base of the top container – then lay a thin layer of food waste on top of the bran. I would avoid oils and big bones – they will break down but will take a long time and consume a lot of bran. It’s best to cut the waste into small pieces or blitz it in a food processor, as the system will work quicker. I also use a potato-masher to press the food down into the bran and expel as much of the air.
Then sprinkle another layer of Bokashi bran on top of the food waste and cover with your plastic bag and your weight, or saucer. Close the lid. The idea is to drive out as much air as you can, as Bokashi is a process where you try to exclude air. Keep this up until the bin is full to the brim, then seal it up and lay it down for two to four weeks.
Every couple of days you need to go back to the system, separate the buckets, and drain off the leachate. The leachate can be used as a liquid fertiliser on your plants. Some sources recommend diluting 1:100. I just pour it into my water butts, as the EM helps keep the stored water sweet. I also pour it neat down the sink, as the EM helps clean the pipes. You should notice a sweet, vinegary scent. A bit like apple cider vinegar. If the mix smells rotten and foul, it is likely rotten and foul and somehow the wrong bacteria, or air has got into the system, and you’ll have to dispose of the complete batch, wash your buckets out with disinfectant and start again.
Don’t under any circumstances be tempted to open the top bin, as it will let air into the system, and your food waste will rot, not ferment or ‘pickle’. After about three weeks, the batch will be ready. When you open your Bokashi bin, you’ll notice a whitish mould around the exterior of the food waste. In spots, it’ll be a bit fuzzy.
This develops from two of the three most common bacteria used in EM and is harmless. Some of the vegetable and fruit matter will have wilted. The contents will have sunk down by a couple of inches, as can be seen from where the ring of bokashi bran shows higher up in the bucket. The contents will not be soil, it will look the same as when you put it in, perhaps a bit greyer. Bokashi does not physically change waste but changes it chemically and structurally. The food waste will look the same, but it has been fermented or Bokashi-d.
How to use it? Well you can dig a trench in your garden and bury it then plant on top after a week or two; you can feed it to your worms; or combine it with your compost pile. Within a few days, the material will have completely broken down and you’ll be left with compost.
Bokashi is a great system and helps us deal with our food waste and carbon footprint and creates beneficial products that can be used to fertilise your garden. To start with it can be tricky getting the process right, if you have any questions or comments, please get in touch