Sunday, October 26, 2008

Tales from the Bucket: the BioBucket

An early outdoor bokashi bucket failed for insects—the fit between my inner and outer buckets wasn’t tight enough, and every fruitfly in the neighborhood decided it’d make a wonderful hatchery.

Okay, I saw one fruitfly and a few tiny larvae, but where there’s one...and I didn’t spend much time looking. Tossed in some AEM, added a couple of inches of dried leaves I’d just swept up, put the lid on with another bucket on top of the whole to add weight, and tried to forget.

Eventually, of course, I needed those buckets. Inside? No swarm of fruitflies, no giant mutant vinegar eels, and no identifiable food waste except for a scattering of melon seeds. What I had was a whole bunch of Black Soldier Fly larvae in what looked like leaf mold.

A point to mention here: had I not failed the bucket already, it would have failed twice at this step, once for insects—BSFL look like steroid-abusing maggots wearing armor—and once for smell. Wet enough for grubs is too wet for EM. But there was no food waste visible, and leaves that had been whole were now as decomposed as if they’d spent six months in a pile.

Grubs. Black Soldier Fly larvae. Volunteers in the war on trash?

I may live in Texas, but I’m not a rancher, certainly hadn’t signed up for free-range grub wrangling. Worms can live in captivity all their generations, but these...

Coward that I am, I decided not to decide what to do about them just then, instead tossing the bucket’s contents in a trash bag with more dried leaves, a pint of mature compost I happened to have within reach, and some quick-fermented bran left over from another experiment. The possums found the bag that night, so the whole megillah (less their dinner) ended up in a different bucket, one not yet fitted with spigot and screen.

After two more weeks, I opened up the bag-in-bucket.


This cannot be called a success for bokashi or any other sort of compost, but if you wanted to raise Black Soldier Fly Larvae, you could do worse. -G- Turns out the things are predictably picky eaters, with no taste for plastic and not much for cellulose: Some of the grubs had left the bag through the possum-created hole, and more from the small gap in the drawstring-top, but none had eaten their way through. The bran seemed untouched, and during sifting, I found no kitchen waste except the battered but recognizable shell of a lime-half and several whole coffee filters, every grain of grounds gone but the paper not even nibbled.

That sifting was done with my breath held against the stench, and I was already composing my post as I worked: Fail! Grubs are not a viable alternative to bokashi bucket fermenting and composting. But—

If the goal isn’t compost, but rather keeping food waste out of the landfill, these things are a major success. Approximately three gallons of food waste went into the outdoor bucket, and nearly that many leaves were added on two separate occasions, plus almost a gallon of bran, call it twelve gallons of matter altogether, three from the kitchen and nine from the (barn)yard. The total mass of grubs etc. was about two and a half gallons, of which less than one pint total was identifiable kitchen remains (one half lime-shell; coffee filters). Though they didn’t digest their way through the whole volume of leaves, they did break down that matter into smaller bits, thus technically reducing that volume, too, as well as the outright conversion-via-ingestion.

The stench? Not their fault, mine. Dried leaves plus moisture create a heavy, compact layer through which odors cannot pass, but trapping isn’t the same as eliminating. Conditions weren’t right for EM in the bucket—initially too much air, and then too much moisture—and unlike the rhodobacters in EM, grubs can’t “eat” stench. With BSFL, it’s all about odor avoidance, based on their speed of eating—fresh waste is devoured too quickly to rot and stink—but the stench was already there, even before I overloaded their bag with cellulose. Plus, I provided no drainage for the latter stage, which meant it was much, much too wet for the EM I’d added to have a chance. So no odor-reducing microbes.

This time.

Yes, despite my revulvion for all things grubby, despite my qualms about mature BSF instars littering my landscape, despite the knowledge that if the racoons ever find them, I’ll achieve landmark Michelin Guide status in the masked-bandit circuit, I’m going to see what happens if I feed food waste to grubs in a proper habitat.

What, you ask, is a proper habitat?

Well, there’s always the retail option, the BioPod. But for those of us not interested in spending that much money for what might be only a passing impulse, there’s some homebrew alternatives. Your browser may not like this link, but try to check out the thread on Cannabis World. According to one bokashi-knowledgeable poster there, a bokashi bucket’s nearly perfect already—just add a layer of mesh between drain-holes and waste, to keep grubs from falling into the reservoir and drowning, and some holes in the top to allow mature, egg-laying BSF entry.

Personally, I think I’ll add a collection system rather than letting the mature migrating grubs just make a run for it, lest they lead the racoons back to the source (possums are defeated by lids; coons are not). And, seeing as winter’s on the horizon, I may invest in a thrift-store cooler if I can find one with a wide-mouthed spigot at the base; I’ve been doing some reading, and BSFL can overwinter in their active immature state. They’ll continue to eat so long as their habitat remains above 15ºC, and they generate their own heat, so an insulated colony could keep working through much of an Austin winter, and should be able to survive even the odd freeze.

Outdoors. Where all insects belong. Cheerily chewing through three pounds of fresh waste per two feet of surface area. Per day. Okay, so I won’t get any compost* out of that—but it wouldn’t end up in the landfill, either.

Queasily grubbing away,


*BSFL “compost” is a high-protein, partially digested friable substance not suitable for use as a planting mix. It does, however, make an ideal worm-growing medium, and at five percent yield, there’s not likely to be enough of it for disposal to be a problem anyway.

Further reading:

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