Guyuan County in Hebei Province experiences extremely cold winters, with temperatures falling below −40°C. Despite these harsh conditions, a large-scale biogas project using potato starch processing waste as feedstock has operated continuously and reliably for more than eight years, providing a proven engineering reference for anaerobic digestion and biomethane projects in cold regions.
The project treats potato pulp and high-strength organic wastewater generated during potato starch production. It consists of four anaerobic digesters, each with a capacity of 6,000 m³, together with a professional biogas holder system. The facility produces more than 26,000 m³ of biogas per day, successfully transforming processing waste from an environmental burden into a valuable renewable energy resource.
The project employs an integrated treatment process comprising hydrolysis and acidification, digestate recirculation and slurry homogenization, anaerobic digestion, biogas purification and upgrading, and the agricultural utilization of digestate. Since the potato pulp has a solids content of approximately 13%, large quantities of fresh water are not used for dilution. Instead, digestate from the anaerobic digestion process is recirculated to the front end for feedstock preparation and homogenization. This approach reduces fresh-water consumption and wastewater discharge while improving internal water recycling efficiency.
The biogas produced through anaerobic digestion enters the biogas holder, where it is safely collected, steadily stored, and buffered to maintain stable pressure. This provides a continuous and reliable gas supply for the downstream treatment system. The stored biogas then undergoes biological desulfurization and membrane upgrading to produce biomethane that meets the required utilization standards. The biomethane is supplied to residents in Guyuan County as a clean fuel for daily cooking and winter heating.
Meanwhile, the digestate is not discharged directly as wastewater. Instead, it is used for farmland irrigation, fertigation, and soil improvement, returning valuable organic matter and nutrients to the agricultural production system.
By integrating waste treatment, anaerobic digestion, biogas storage, biomethane utilization, and digestate recycling, the Guyuan project has established a circular model that converts agricultural processing waste into clean energy and ultimately returns nutrients to farmland. More than eight years of operational experience demonstrate that even under extremely cold climatic conditions and with high-solids feedstock, biogas projects can achieve continuous, stable, and efficient year-round operation through appropriate process design, effective thermal insulation, and reliable equipment configuration.
