Journal
APPLIED ENGINEERING IN AGRICULTURE
Volume 38, Issue 1, Pages 165-176Publisher
AMER SOC AGRICULTURAL & BIOLOGICAL ENGINEERS
DOI: 10.13031/aea.14180
Keywords
Anaerobic; Biogas; Co-digestion; Dairy manure; Digestion; Food waste; Volume-mass flow conversion
Categories
Funding
- National Institute of Food and Agriculture, U.S. Department of Agriculture [2016-68003-24601]
- Cornell PRO-DAIRY Program via New York State Department of Agriculture and Markets
- Chilean Fund for Science and Technology (FONDECYT) [1161697]
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This study presents three methods for estimating the mass-flow difference in anaerobic co-digestion systems, based on widely accepted principles. The results show that a simplified input-based method is consistent with real-time data for predicting influent mass flow loss. The reduction in effluent flow is around 3% for systems adding off-site wastes at 30% or less of the total influent volatile solids.
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.
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