The effect of ammonium dihydrogen phosphate (NH4H2PO4) on rice straw (RS) carbonization was evaluated at temperatures of 350-650 degrees C. The carbonized products of RS with NH4H2PO4 show higher solid and energy yields, but lower higher heating values than the carbonized RS at every carbonization temperature. The optimum carbonization operation of RS with NH4H2PO4 which has a higher energy yield at a lower solid volume may be determined between 350 and 450 degrees C, and RS with NH4H2PO4 carbonized at 450 degrees C presents better pore properties than carbonized RS. The carbonized products of RS with NH4H2PO4 all have lower gaseous potassium release ratios than those of RS carbonized at the same temperature at combustion temperatures of 700-1000 degrees C by retaining potassium in non-volatile phosphorus compounds with high melting points. It is an effective method for inhibiting the gaseous potassium release during combustion of the carbonized products. (C) 2015 Elsevier Ltd. All rights reserved.