Co-digestion of Hog Manure with Glycerol to Boost Biogas Production Oswald Wohlgemut (MSc) July 14, 2008

Farm-scale Anaerobic Digestion

Background  Anaerobic digestion

Lab Research Co-digesting hog manure with Glycerol Goals – To find optimal glycerol dosage – To boost biogas and methane production – To determine nutrient (N,P) fate through digestion – To gather information to be used for operating a pilot-scale model Biodiesel Glycerol

Why co-digest with glycerol?  To find a valuable use for biodiesel waste  To help boost biogas and methane production  Make the process more economical  To reduce GHG emissions  To increase “green energy” in Manitoba

Experimental Setup  4 bench-scale anaerobic digesters (4L)  Complete-mix, mesophilic (35ºC), semi-continuous fed, with gas collection

Experimental Setup 1. Shock Loading Effect – addition of 1%, 2%, 4% pure glycerol (by weight) 2. Comparison Study – comparing 1% pure glycerol to 1% crude glycerol (by weight) 3. Digester Recovery – testing microbial resistance to high COD glycerol loading over time

Feed Characteristics  Hog manure screened and diluted (~1% TS)  pH 7.6 Digester FeedCOD (g/l)Additional COD load Manure (Control)16.7 Manure + 1% Pure Glycerol x Manure + 2% Pure Glycerol x Manure + 4% Pure Glycerol x Manure + 1% Crude Glycerol x

Results  Shock Loading Experiment  Control (Manure) ~ 72% CH 4  Manure + 1% pure glycerol ~ 64% CH 4

Results  Shock Loading Experiment  Reactors with 2% and 4% pure glycerol addition were overloaded with SCOD and did not stabilize

Results  Comparison Experiment  Control (Manure) ~ 70% CH 4  Manure +1% pure glycerol ~ 63% CH 4  Manure + 1% crude glycerol ~ 67% CH X

Results  Digester Recovery  Can bacteria recover from overloading?  Comparing 2% glycerol loading in experiment 1 & 3 Experiment 1 Glycerol start Glycerol stop 2.8 X Experiment 3

Results  Methane Yield and Composition Substratem³CH 4 /kg COD added % CH 4 composition Control (Manure) % pure glycerol + manure % crude glycerol + manure % pure glycerol + manure

Conclusion Biogas and methane production increased with glycerol addition A high glycerol shock loading can cause digester failure with a buildup of VFAs Bacteria were able to recover and utilize high glycerol COD loading over time Methane composition decreases with increasing glycerol addition Crude glycerol did not have inhibitory effects

Future Research  Batch experiments with raw manure to determine BMP (Biochemical Methane Potential) of manure with different concentrations of glycerol  Analysis to determine nutrient (P, N) fate through digestion with glycerol

Future Research  Pilot-scale digester in a solar greenhouse

Acknowledgements  Manitoba Agriculture, Food and Rural Initiatives  Dr. Nazim Cicek  Dr. Jan Oleszkiewicz  My colleagues in the lab

Questions?