Enhanced bioenergy production in rural areas: Synthetic urine as a pre-treatment for dry anaerobic fermentation of wheat straw

Straw and urine have always been two major problems in rural environmental management worldwide. Realizing the recycle of resources is possible to solve the dual problems of resources and environment. In this study, synthetic urine was proposed as a pretreatment method for wheat straw. The effects and application potential of synthetic urine on anaerobic fermentation of wheat straw were explored by comparing the start-up time, pH, methane production and other parameters of dry anaerobic fermentation system with four other traditional pretreatment and non-pretreatment (control). The results showed that the synthetic urine can effectively destroy the fiber structure of straw and beneficial to control the pH in the optimal range to avoid acidogenesis, speeding up the methanogenesis process (10 d). Compared with the control group, the total solid gas production rate and volume gas production rate after pretreatment with 1: 3 dilution of synthetic urine increased by 56.3% and 100%, reaching 195.73 mL g−1 and 1.20 m3 (m3 d) −1. The startup time of the system is also shortened by 11 d. Compared with other pretreatment groups, the methanogenesis process after synthetic urine pretreatment was the shortest (39 d), and the maximum methane production reached 121.5 mL g−1 VS. These results provide evidence that the synthetic urine has good potential to co-ferment with straw to increase bioenergy production in rural areas.