The main problem at the moment is a lack of incentives to use it at waste water treatment plants, but I guess this will come with increasing Phosphorus prices. Still it would be beneficial to start recovering more Phosphorus already now but this is a political issue rather than an Engineering issue in my opinion.
http://www.grontmij.com/highlights/water-and-energy/Pages/pe...
The main problem at the moment is a lack of incentives to use it at waste water treatment plants, but I guess this will come with increasing Phosphorus prices. Still it would be beneficial to start recovering more Phosphorus already now but this is a political issue rather than an Engineering issue in my opinion.