Sure - I will agree with that future of SOP production is in...

Sure - I will agree with that future of SOP production is in seawater extraction but only in a close/distant future when energy is plentiful and cheap. Until that future, hypersaline saltwater lakes and inland brine extraction will dominate due to the simple fact their salt concentrate i.e. potassium concentrate is higher which means whatever method you use for extraction will be cheaper compared to in seawater. Looks like RWD also agree as their extraction method target high sulphate brines as well as seawater - at the end of the day the viability of the project will come down to extraction costs