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HIGH-SOLIDS ANAEROBIC FERMENTATION OF BEEF CATTLE MANURE: A BIOENGINEERING ANALYSIS
Abstract
A study was conducted to determine the feasibility of high-solids anaerobic fermentation of beef cattle manure at 35(DEGREES)C. An experiment was designed in which influent total solids levels of 10, 20, 30 and 40 percent (%) wet basis were the primary variables. The experiment was divided into two phases--Phase I with manure as substrate (C/N = 11) and Phase II with glucose amended substrate (C/N = 25). Organic loading rates (L(,r)) of 5 and 8.3 kg VS m('-3)d('-1) for Phase I, and 6.4 and 10.6 kg VS m('-3)d('-1) were selected for Phase II. Eight 25-L tumble-mix fermenter were used as test apparatus. Process performance at steady state conditions, analysis of process failures, kinetic analysis of steady state data using the modified Contois model and comparative net energy analysis were conducted. The results showed that anaerobic fermentation of beef manure at 20 to 30% influent total solids (TSI) was possible. The upper limit of the organic loading rate at which stable fermentation could be obtained at 30% TSI was 5.0 with beef manure at C/N = 11 and 10.6 with glucose amended beef manure (C/N = 25). Process failures occurred above an L(,r) of 5.0 for Phase I and 6.4 for Phase II at 30% TSI and for all L(,r)'s at 40% TSI. Steady state data indicated that maximum COD and VS removals could be obtained between 20 and 30% TSI. The greatest methane production, (gamma)(,v) = 3.13 L L('-1) was obtained at 20% TSI with an L(,r) of 10.6 and C/N of 25. The addition of glucose contributed most if not all to the increased (gamma)(,v). High effluent total ammonia and TVA characterized the fermentation process at high TSI. Kinetic analysis of the steady state data at 30% TSI showed that the fermentation process was inhibited indicated by high values of the Contois inhibition index, K. The onset of inhibition occurred at an influent VS of 125 and 300 kg VS m('-3) with manure and modified substrate, respectively. A comparative net energy analysis indicated that at an L(,r) of 5.0, the net energy produced with a tumble-mix fermenter at 20% TSI was lower than that of an equivalent conventional fermenter at 12% TSI.
Subject Area
Environmental science
Recommended Citation
LUIS, VICTOR SAGUIGUIT, "HIGH-SOLIDS ANAEROBIC FERMENTATION OF BEEF CATTLE MANURE: A BIOENGINEERING ANALYSIS" (1983). ETD collection for University of Nebraska-Lincoln. AAI8314906.
https://digitalcommons.unl.edu/dissertations/AAI8314906