Landfills are required by EPA regulation to be lined, as well, and largely, they're being utilized as sources of energy. A landfill can be thought of as a giant battery with a fairly large supply of energy. Then again, so can a cow, I guess.
Our waste oils from the fryer basically end up in the septic tank. That's been done here for 15 years, and the septic hasn't been treated or pumped once in that time. Before my Father moved in to the house, the Septic was pumped at least every 3-5 years, because it kept backing up, and my Father's sister and brother in law used to put every "help my septic tank" chemical known to man down the toilet to help it. I kept telling them that wasn't the way it worked, and they always "knew better than me".
My Father took my word for it.
I can agree that WVO shouldn't just be dumped wherever, but I still will not agree that it's viable as a fuel. It's just too easy to make it into BD (often, the same energy you'd expend filtering and etc...) to ignore the potential ramifications of it. And even if not harmful to anything, turning triglycerides into raw glycerin still will have an available marketable aspect, if even just as fertilizer/pesticide.