Phosphoric acid pretreatment of biomass

It has been noticed that concentrated phosphoric acid is an ideal cellulose solvent. The advantages of phosphoric acid pretreatment of biomass includes:

• cellulose dissolution by phosphoric acid occurs at low temperatures
• phosphoric acid can dissolve cellulose in the presence of water
• the regenerated cellulose remains in an amorphous form suitable for hydrolysis
• the residual phosphorous acid has no inhibitory effects on the sequential
  hydrolysis and fermentation.

But what about the cost?