is safe to use pvc barrel like this? So i would like to fill it with full of sawdust and filter biodiesel trough it??
only if you upflow. woodchips soaked in fuel exposed to air have been known to ignite.
It's ok as long as you keep the chips covered in biodiesel so air can't get to the wood chips. The only time biodiesel chip filters have been known to "oxidize" is when the biodiesel was drained out of the chips. Still, there has been no report of the wood chips "bursting into flames", only reports of the chips in the center of the drum turning black from oxidation when left to drain overnight.
You will have to drain out the biodiesel before you can change out the wood chips with fresh material. However, the process of spontaneous combustion takes time, hours. So, you have plenty of time to drain the biodiesel and dispose of the wood chips safely, like in a fire you set.
In general however Igor, please understand that you are making fuel. This isn't needle point, where the worst that could happen is being stuck with a needle. Making Fuel does come with risk. There is no "SAFE" way to make fuel, only safer ways.
After studying homebrew accidents for several years, I came up with a set of safety tips every biodiesel hobbyist should know about. Following them does not guarantee you will not have an accident, just make them a lot less likely, and less disastrous if they do happen.
Safety Tips for Biodiesel Home Brewers
thanks for all your answers
I totally agree with you...