I think the methanol should be removed before dumping the glycerin. I have read on biodiesel.infopop that some are applying demethed glycerin at a rate of 8 gallons/acre. The theory is that the potassium (K) in the glycerin is available to plants.

I have a friend that is using the glycerin to heat his oil and is having good results. If he stopped taking my glycerin, I think I would just set up a burner and burn it off. They take small galvanized pipe, heat it, and wrap it around a drive shaft (for a form). The nozzle is placed at the bottom of the coil so it heats the glycerin before it hits the nozzle and it can be pressured with a small pump or air compressor.