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Disposing of Biodiesel Waste

Recycle Your Failed Biodiesel Reaction

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Making Biodiesel - Bad biodiesel reaction on left

Failed soapy biodiesel reaction on the left; good fuel on the right

Photo © Scott Gable

Sometimes biodiesel reactions just go wrong. We even wrote an article on troubleshooting (and saving) failed batches of biodiesel. But, on occasion, even the biggest dose of determination won't overcome a case of "bad biodiesel blues." So, then what?

When All Else Fails

It hurts a little to give up on a recalcitrant batch of BD. We biodiesel homebrewers tend to be stubborn do-it-yourselfers who pride ourselves on overcoming setbacks and failures. But reasonable folks have to know when to wave the white flag. So, what to do on those occasions when a No Reaction or Soupy Reaction batch won't respond to any of your valiant attempts to salvage it? Short and sweet: recycle it (well, compost it really). CAUTION: Do not dump it down the drain--you wouldn't do that with any other automotive chemical, would you? BD glop is not technically hazardous waste, but it's not exactly benign either (as it hurls down the drain towards waterways unknown).

A failed gloppy batch of biodiesel is mostly an incomplete batch of soap (glycerin) that can be recycled back to nature, but it must be done right. Just dumping a bucket of glop in a hole in the ground, and then walking away, won't do--biodegradation is an aerobic (requires exposure to oxygen) process. The secret to effective composting is to keep the organic matter aerated. Here's how we do it: We mix leaves, twigs (that's twigs, not branches) and straw in with the glop, and then pour it into a small glycerin composting area we built behind our main garden compost bin (experience has shown that our garden waste decomposes at a different rate than our biodiesel waste). Every couple of weeks we add more straw and leaves and give the whole shebang a good salad-style toss with a pitchfork. This manual aeration technique helps keep the microbial decomposition chuggin' along, as well as assisting in the evaporation of any trace methanol from the original glop. Let a few months pass, and "tah dah," you have rich black peat to help your garden grow.

And if you have no provisions for composting in your backyard, don't be dismayed--perhaps a deal can be cut with a neighbor, friend or relative. It's another hallmark of determined do-it-yourselfers--to trade and barter skills, tools and favors. But if you just can't swing that deal, as a last resort, contact your local hazardous waste recycling center--explain what you have and see what they recommend.

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