Large-scale Bokashi??!?

Food bank
Bokashi bins outside Great Falls food bank. Photo by Mary Jane Arendes.

As I mentioned in yesterday's post, I'd never heard of largescale Bokashi composting until Sunday afternoon at the Best of Bioneers festival here in Bozeman.

Several years back, Michael Dalton and Mary Jane Ahrendes hadn't heard of it either, but that didn't stop them. Inspired by another Bioneers conference several years ago, they founded an organization, Gardens from Garbage, and started setting up composting systems around their city of Great Falls. Bokashi composting systems.

Bokashi is an anaerobic (oxygen-free) composting method (as to opposed to the back-yard aerobic heap methods most of us are familiar with) which uses special microbes to essentially pickle waste into compost. Most often used for household garbage, the method requires nothing more than an airtight container and some starter microbes, usually in the form of treated wheat bran, which gets sprinkled over each layer of garbage until the vessel is full.

The vessel is then sealed and set aside to do its anaerobic thing. A commercial Bokashi maker usually has a spigot at the bottom for draining off the considerable amount of liquid produced, a leachate that can be used as a fertilizer, in a diluted form. After ten to fourteen days, the contents are ready to take to the garden.

It's rich but acidic stuff, so when most people bury it in the garden, it's only half-done; it needs to finish composting for a couple of weeks before plant roots can encounter it unharmed.

Now, I researched this method—along with everything else I could find—when I did my big composting article a couple of years ago, and never heard about anything larger than a 5-gallon household vessel. (You can see everything I know about it at

But along come Michael Dalton and Mary Jane Ahrendes. Undaunted by the fact that no one's done this before, they get an architect to donate a plan for large-scale vessles, and they start building them.

Their modest goals include establishing composting systems at all the schools in their city (they've got systems up and running at two elementary schools and are working on bins at six others; that leaves just seven to go) and eventually involving all the grocery schools and restaurants in Great Falls. They have already built a remarkable series of bins for their local Food Bank, (see the photo at the top of the page,) and they have helped to establish a composting program at the Salvation Army store in Billings, Montana, where six graduates of Rimrock Foundation's substance-abuse programs have been hired to run the program and to establish similar programs in other cities. Those six, soon to be joined by three more, used to be homeless.

On the side, Michael and MJ are setting up a program dubbed V.E.G.I. (Virgelle Education Greenhouse Institute) in a neighboring town (only 74 miles away, which is nothing in Montana) which "will provide the rural community with locally grown vegetables, eggs & chickens year-round and serve as an education center for cold composting, vermiculture, organic gardening, food preservation, and cooking." The problem with these folks is they just don't know how to think big.

At each Bokashi site, with the help of volunteer labor, this indomitable pair constucts a number of air and water-tight bins, so that when a full one is sealed and left to compost, others can be filled.

Often constructed from free pallets, each 4'x4' bin is lined with visqueen (or visquine), a tough plastic, so that it is both air and water-tight. There's apparently an evolving method for collecting liquid from the bottom of the bins. (Since this is an anaerobic, or oxygen-free process, drainage holes aren't an option.)

Michael and Mary Jane leave their bins closed for 90-120 days, so that the contents are completely decayed by the time the lids are removed. The result, therefore, looks and feels like regular compost. It's a lot easier to deal with–and a lot easier on the nose–than the ten-day old pickled sludge most home Bokashi processes talk about.

Their secret–their ability to get this–

Bokashi compost 3 weeks later

Three weeks later. Photo by Mary Jane Arendes

as opposed to this–

Food scraps after fermenting
Food scraps after fermenting. from bokashicycle

arises from the second step of their process: adding "brown matter" such as dried leaves to the fermented scraps, then sealing it for another two weeks.

Aside from the fact that this is simply possible, I really didn't recognize some of the advantages that Bokashi has over conventional heap composting. For one thing, it's far less labor intensive. A hot compost pile needs to be turned every few days to a week, and even a cold pile needs occasional turning. For the home composter, this is work. For large-scale operations, it's not only work, it's fossile fuel, as large piles require machinery to turn them.

Secondly, Bokashi keeps functioning all winter, whereas since a conventional pile is aerobic, it tends to shut down as the air temperature drops. It's possible to keep a hot pile going all winter, but with something the size of a backyard pile, it's tough.

Third, there's a whole slew of issues that I've never dealt with, because I'm just a back-yard composter. But apparently, setting up a large-scale composting operation requires a permit, and yearly fees, and these are hefty. Besides that, the operator has to dig not one but two wells in order to monitor ground water quality.

Because Bokashi is done in enclosed bins, all of these fees were waived. So for large-scale operators, Bokashi is cheaper and cleaner than conventional composting.

As far as I can see, one of the few disadvantages of Bokashi is that it doesn't handle the harder-to-compost things that a hot pile will eventually break down: twigs, avocado pits, and orange peels. But then, a heap doesn't break these down in one round either; they need to be tossed back into the pile for a second go-round. So you either sift your compost (which could be done with Bokashi as well) or you let some stuff go into your soil in an unfinished state, or you relegate these items to their own, longer-term pile–or bin. So there's really no difference between backyard heaps and Bokashi in this regard.

I've belatedly figured out how to download pictures from their site (the obvious way), but there are plenty more there. Hop on over to Gardens from Garbage and have a look.

5 Responses to Large-scale Bokashi??!?

  1. So do they seal the entire bin in the above picture, or seal it in segments?

  2. Thanks for posting, interesting article for sure.
    Do you try using Coir as a potting mix as well??
    Thank you

  3. Interesting One. It is very easy to make an organic compost. Just you need green materials, brown materials and water to make an organic compost. Organic compost is used in indoor gardening as well.

  4. Interesting One. It is very easy to make an organic compost. Just you need green materials, brown materials and water to make an organic compost. Organic compost is used in hydroponics as well.

  5. Eloïse Le Bras

    What about using Bokashi method for managing ONLY green wastes? (We have every day 150 cubic meters of tree leaves (80% are Albizia saman) and grass to manage)

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