In my experience Biodiesel is always more expensive than diesel. It may be cheaper if you make your own and don't count the value of your time. Most people value it for its environmental and social value.

WVO can be almost free. I get mine by driving behind a local ( one mile away ) restaurant and grabbing the cubes they set out for me. Really no time lost. Filtering takes a little time. I drink beer, listen to music and clean/fix/build stuff while it is filtering, it takes little attending. Start with good oil and filter it well.