This is overall an interesting idea. They have to burn the gas off, I'm assuming it's infeasible for them to send the electricity anywhere useful, so mining bitcoin let's them do something with the fuel they would otherwise just waste.
I wonder if the same idea could be improved upon to actually do something useful. For example, a portable GPU data centre, for ML model training? Maybe the bandwidth requirements are too high. Anyway, the concept is good (using waste fuel for on-site data processing), they just need to find a better application