In-situ injection of potassium hydroxide into briquetted wheat straw and meadow grass - Effect on biomethane production

•Lignocellulosic biomass was pretreated by in-situ injection of KOH during briquetting process.•Pretreated capacity ranged from 350 to 800 kg.h−1 corresponding to 0.8%-10% (w/w) of KOH injection.•Improvements in both biomethane yield and hydrolysis rate were observed.

Alkaline pretreatment of lignocellulosic biomass has been intensively investigated but heavy water usage and environmental pollution from wastewater limits its industrial application. This study presents a pretreatment technique by in-situ injection of potassium hydroxide concentrations ranging from 0.8% to 10% (w/w) into the briquetting process of wheat straw and meadow grass. Results show that the biomethane yield and hydrolysis rate was improved significantly with a higher impact on wheat straw compared to meadow grass. The highest biomethane yield from wheat straw briquettes of 353 mL.g−1 VS was obtained with 6.27% (w/w) potassium hydroxide injection, which was 14% higher than from untreated wheat straw. The hydrolysis rates of wheat straw and meadow grass increased from 4.27 × 10−2 to 5.32 × 10−2 d−1 and 4.19 × 10−2 to 6.00 × 10−2 d−1, respectively. The low water usage and no wastewater production make this a promising technology.