A process for driving a prime mover, said process comprising a)
positioning a selective membrane between a liquid and a solution having a
higher osmotic potential than the liquid, such that the solution becomes
pressurised by the influx of liquid across the membrane, b) using the
pressure generated in the solution to drive a prime mover, c) recovering
the solution, d) separating at least some of the solvent from the
solution to form a residual product, and e) recycling the separated
solvent and/or the residual product of step d) to step a).