Indeed.  I've been looking at mineral oil, but it has a lot of up front expenses. If done right, and at scale, it could provide an edge by consuming about half the electricity.  Though I see the next big area of profit being a big jump in hashpower.  If somebody would make a 50 TH/s miner, that'd surely be profitable for a while.  However, I'm not sure I see that playing out due to high up front costs.