This has come up before, but the discussion got lost. Basically, some home bio-diesel maker asked what to do with NaOH methanol containing waste. And I told her to pretend she was a petroleum manufacturer -- she should burn some of her biodiesel to generate heat to distill the water, methanol, and glycerol off from a concentrated solution of spent NaOH and soaps. She should quantify what goes into the still, and what goes out. She can sell the glycerol, reuse the methanol, discharge the pure water (checking first what the environmental requirements would be, verify that the waste meets those requirements, and document those facts) and store, warehouse and eventually pay a waste collector to dispose of the waste salts responsibly, again, documenting the status of the waste, and her own compliance. This is why petroleum products are expensive. Obviously, an experimental production of bio-diesel doesn't need all of this, but if you're going to compare the cost effectiveness of the process, these are costs that you can't ignore.