Hydrothermal co-carbonization of rice straw and acid whey for enhanced hydrochar properties and nutrient recovery

This study investigated rice straw hydrothermal carbonization (HTC) in water, optimizing operating conditions to enhance solid carbon content and nitrogen content in hydrochar. Additionally, we conducted hydrothermal co-carbonization (co-HTC) of rice straw and acid whey, achieving significant improvements in hydrochar properties. Co-HTC resulted in a 53.6% increase in HHVs, 20.0% higher yield, and a 42.7% rise in carbon content, accompanied by notable reductions in ash content. Nitrogen content increased by 26.0%, P content by 12.7 times, and K content by 27.6%. Analytical techniques revealed promising modifications, indicating potential applications of hydrochar in solid fuel or organic fertilizers, thus contributing to a circular bioeconomy in agricultural waste management.