sustainability | The Peterborough & Area Master Gardeners

By Marjorie Vendrig, Master Gardener in Training

Five years ago I moved from a large rural garden outside Ottawa to a small urban lot in downtown Peterborough. One of the biggest changes in my gardening practice was making the switch from large, multi-bin composting to a single, small, black plastic bin. Over the years in my Ottawa garden I had developed a good system for adding kitchen and garden waste, turning the compost, adding leaf mulch, then spreading the compost over the gardens. Here in Peterborough, my small plastic bin was productive on a smaller scale but the raccoons, bunnies, and rats managed to chew through the plastic and serve themselves. It was more of a mess than a benefit. They defeated me. Thankfully, the municipal kitchen waste program kicked in about the time the racoons moved in, giving me a reasonable alternative for kitchen waste. My garden wasn’t getting much benefit except for the fall leaves that I mulched and put over the beds.

I realized that I really miss composting and I would prefer to be putting my own food scraps back into my garden. I started looking into composting systems for small spaces and came across bokashi composting. It’s not really composting, rather a fermentation process, and described as perfect for small spaces. Sometimes called a ‘pre-compost’ process, the fermented results are added to worm compost or outdoor compost where decomposition is completed. It’s also anaerobic so there’s no need to turn the compost or layer materials. The process is fairly fast, about two weeks for the initial fermentation step. Any kitchen waste, including meat, cheese, oil, can be added. Bokashi is a Japanese word meaning fermented organic matter; the practice originated in Japan.

The anaerobic fermentation process requires an accelerator, something like a starter for sourdough baking. It is often referred to as ‘bokashi bran’, the bran inoculated with microorganisms – fungi, lactobacteria, phytobacteria. It’s easy enough to put together a homemade system with a few 5-gallon buckets – one with a tight sealing lid – and other household items. One bucket should have holes drilled in the bottom; this bucket is placed inside the other; the holes allowing any moisture from the fermenting food to drip into the bottom bucket. Fill the top bucket with layers of small 2 – 3” kitchen scraps and bokashi bran until the bucket is almost full, cover and press with a layer of waxed paper, a cloth, or even some foam before sealing the bucket with the lid and leaving for a few weeks to ferment. After about one week some white mold with develop, after two weeks the bucket will smell like pickles and the fermented material can be buried in the garden about 6-12”deep. It will decompose fairly quickly in the garden and planting can be done around the fermented trough after a few weeks. Alternatively, it can be added to the compost heap or even into a large tub of soil indoors where it will continue to decompose. Any liquid – the ‘tea’ in the bottom bucket can be added to the compost or garden as well.

Bokashi bran is widely available online and at some garden centres; it’s also possible to buy a kit that includes bran, several buckets, and instructions. The buckets in the kits often have a tap and reservoir so the ‘tea’ can be collected at the bottom of the bucket. Like sourdough starter, the bran can be made at home, though some starters work more quickly than others. It’s worth experimenting to test a few products and compare results. I’ve learned that a few cities in western Canada have municipal bokashi programs so it is possible in colder climates. On a large scale, it is also being trialled at Sissinghurst, a famous garden in the UK.