I have been giving much thought to this sulpher issue and it really is a non issue. ZEN's graphite purifies to 99.97 to 99.99% so even if there was 0.03% of contaminants and 100% of those contaminants were sulpher, that is still not enough to be an issue in the battery market.
So for me, there is no issue with sulfur. The only ones trying to make this an issue own no shares of ZEN.
G.