Case Study 7: Innovative Applications for High-Value Utilization of Biogas and Biomethane | Comprehensive and Coordinated Utilization Across the Entire Biogas Industry Chain

01 Overview:

The comprehensive and synergistic utilization of the entire biogas industry chain achieves diversified, high-value applications of biogas project outputs by establishing a full-industry-chain application scenario encompassing “manure treatment—biogas—digestate and digestate liquid—agricultural recycling”: biogas is supplied directly to ceramics manufacturers as a clean fuel; digestate is returned to livestock farms to replace traditional bedding materials such as sand and sawdust; digestate liquid is returned to fields as organic fertilizer after standardized treatment; and the by-product carbon dioxide from purification is used for microalgae cultivation. At the same time, standards for digestate liquid irrigation are established and promoted to facilitate absorption channels, transforming digestate liquid from an environmental burden into “customized nutrient solution” and forming a closed-loop system of full-volume recycling that “utilizes every last bit.” Schematic Diagram of Comprehensive Synergistic Utilization Across the Entire Biogas Project Industry Chain

02 Scenario Characteristics

First, co-production of multiple products achieves full-volume, high-value utilization. Purified biogas is supplied directly to industrial users; digested slurry replaces sand bedding and is reused on pastures; digested liquid is processed into liquid fertilizer for application to fields; and carbon dioxide is used in microalgae cultivation to produce protein powder, achieving “one feedstock, four products” and maximizing resource utilization. Second, standardized application of digested liquid to fields eliminates disposal bottlenecks. Standards for biogas liquid irrigation have been established and promoted; through dedicated pipelines, biogas liquid is mixed with irrigation water in a specific ratio and delivered to fields, enabling precise application. Third, carbon capture extends the industrial chain, turning waste into valuable resources. Carbon dioxide generated during the purification process is used for biological carbon sequestration via microalgae cultivation technology and processed into food-grade algal powder, transforming “waste gas” into high-value-added products.

03 Suitable Regions

Suitable for regions with concentrated livestock farming, clear industrial energy demands, and well-developed agricultural absorption infrastructure.

04 Application Cases

The Full-Chain Biomass Energy Circular Economy Project in Ying County, Shuozhou City, Shanxi Province, employs a mesophilic fully mixed anaerobic digestion process combined with membrane purification technology. It produces 4.6 million cubic meters of biogas annually, which is supplied directly to local ceramic industry users via a self-built pipeline network; It produces 60,000 metric tons of biogas slurry bedding annually to replace traditional sand bedding and supply it back to livestock farms; a 25-kilometer dedicated pipeline has been laid to return 517,000 metric tons of biogas liquid to farmland annually, covering 120,000 mu of farmland; and the carbon dioxide byproduct from the purification process is used for microalgae cultivation, yielding 10 metric tons of food-grade algal powder annually.