Valuable supplies of phosphorus could be recovered from sewage sludge ash, which remains after the sludge has been burned for electric power generation. The method has been developed by chemical engineers Yuuki Mochizuki and Naoto Tsubouchi at Hokkaido University's Center for Advanced Research of Energy and Materials.
Sewage sludge, available in plentiful amounts, is currently burned in large quantities for power generation and also to reduce its volume. The remaining ash is relatively rich in phosphorus, leading to increasing efforts to find efficient ways to recover the phosphorus. Existing methods encounter several significant problems, however, including chemical contamination requiring further purification and complicated expensive chemical processing.
They therefore explored the volatilization behavior of the different elements in sewage sludge ash under different chemical conditions, especially with and without carbon being added during a sludge treatment process involving chlorine. This allowed them to develop an effective method for separating useful phosphorus-containing compounds using a combination of chlorination steps with and without the presence of carbon.
Modern agriculture is underpinned by a steady supply of fertilizer. However, one of the main ingredients of fertilizer, phosphorus, is running out, putting pressure and financial strain on farmers ...