Improving the bioenergy production from wheat straw with alkaline pretreatment

• KOH pretreatment for wheat straw including black liquor recycling was investigated.
• Water and KOH consumption were reduced by 75% and 25% with recycling.
• Pretreatment with black liquor recycling reached steady state after five batches.
• Higher sugar and CH4 yields were obtained compared to raw straw treated with liquor.

A pretreatment process for wheat straw using potassium hydroxide (KOH) and recycled black liquor as a treatment reagent was developed and the minimum fresh chemical and water requirement were determined. Black liquor recycling in the pretreatment process resulted in a 75% reduction in fresh water use and 25% in KOH use, when compared to no recycling. It was found that after five batches of treatment, the concentrations of reducing sugar, chemical oxygen demand (COD), and K+ in black liquor, reached stable levels. During the pretreatment with black liquor recycling, 32–35% lignin was reduced in wheat straw. The pretreated straw showed reducing sugar yield of 336–366 mg g−1 [total solid (TS)] and methane yield of 290–303 mg g−1 [volatile solid (VS)] when subjected to enzymatic hydrolysis and anaerobic digestion, respectively.

Figure optionsDownload as PowerPoint slide