Open AccessA Practical Approach for Estimating Influent-Effluent Mass Flow Differences in Dairy Manure-Based Anaerobic Co-Digestion Systems
Author(s) -
Rodrigo A. Labatut,
James Winston Morris,
Curt Gooch
Publication year - 2022
Publication title -
applied engineering in agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.276
H-Index - 54
eISSN - 1943-7838
pISSN - 0883-8542
DOI - 10.13031/aea.14180
Subject(s) - effluent , biogas , anaerobic digestion , manure , volume (thermodynamics) , environmental science , methane , anaerobic exercise , waste management , environmental engineering , pulp and paper industry , chemistry , engineering , agronomy , physiology , physics , organic chemistry , quantum mechanics , biology
HighlightsThree rigorous, methods for estimating influent-effluent mass flow differences due to biogas generation in manure-based anaerobic co-digestion systems are presented. The methods developed reveal that influent-effluent mass flow differences are driven by waste biochemical conversion - biogas water vapor content is insignificant. A simple, input-based method produced comparable results to two, more complex, output-based methods, when tested using 12 months of data collected from three dairy-based anaerobic co-digestion systems.Abstract. During co-digestion of dairy manure and off-farm organic waste in farm anaerobic co-digestion (AcoD) systems, the process’s conversion of biodegradable organics to biogas reduces the volumetric mass (or mass-volume) of the effluent discharged compared to the mass-volume fed. In this study, we present three methods for estimating the mass-flow difference between influent and effluent due to conversion to biogas based on widely accepted, rigorously applied, biological and engineering principles. Monthly operating data from three full-scale AcoD systems, operated under different conditions for a full year were used to compare results using the three calculation methods. Results revealed that the predictions of influent mass flow loss obtained using a simplified input-based method primarily based on influent volumetric flow rates and biodegradability data were in good agreement with those obtained using more accurate, real-time data, namely methane concentration and biogas production. For AcoD systems adding off-site wastes at around 30% or less of the total influent volatile solids (VS), the estimated reduction in effluent flow was in the range of 3% or less. In one case, for VS additions up to approximately 60% of the AcoD system’s influent load, the reduction was 12%. Accepted fundamental water vapor relationships were also applied to biogas generation. Biogas water vapor loses were estimated to comprise approximately 0.2% of the total biogas mass-volume typically produced. Since in most anaerobic digestion systems, biogas condensate water is returned to the influent, this insignificant amount may be ignored. Keywords: Anaerobic, Biogas, Co-digestion, Dairy manure, Digestion, Food waste, Volume-mass flow conversion.