Evaluation of a Trickle Flow Leach Bed Reactor for Anaerobic Digestion of High Solids Cattle Waste
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DESCRIPTIONProceedings available at: http://www.extension.org/67604 Colorado is the second highest producer of high solids cattle waste (HSCW) in the United States. Despite the available resources, Colorado currently has only one operational anaerobic digester treating manure (AgSTAR EPA 2011), which is located at a hog farm in Lamar. Arid climate and limited water resources in Colorado render the implementation of high water demanding conventional AD processes. Studies to date have proposed high solids AD systems capable of digesting organic solid waste (OSW) not more than 40% total solids (TS). Lab tests have shown that HSCW produced in Greeley (Colorado) has an average of 89.4% TS. Multi-stage leach bed reactor (MSLBR) system proposed in the current study is capable of handling HSCW of up to 90% TS.
- 1. EVALUATION OF A TRICKLE FLOW LEACH BED REACTORFORANAEROBIC DIGESTION OF HIGH SOLIDS CATTLEMANUREAuthors:Asma Hanif Graduate Research Student, Colorado State UniversityLucas Loetscher, Graduate Research Assistant, Colorado State UniversitySybil Sharvelle - Assistant Professor, Colorado State UniversityKelly Wasserbach Graduate Research Assistant, Colorado State University
2. Introduction Colorado Second highest producer of cattle manure inthe United States (19 million tons of manure/yr) Difficulties in organic solid waste management Growing demands for renewable sources of energy Anaerobic digestion of the produced cattle manure -Biomass energy equivalent to 46 billion BTU/day 3. BackgroundOperational anaerobic digesters in the US as of September 2012 (Source: EPA) 4. Anaerobic digestion in Colorado Second highest producer of cattle manure in the US yetno operational digestersReasons:o Arid climate - Produced cattle manure is very dry (approximately90% total solids)o Limited water resources 5. Types of anaerobic digesters 6. Leach Bed Reactors (LBRs)Advantages: High solids reactor Low water requirements Low energy requirements Good methane yieldsLimitations: Reactor clogging leading to lowerhydrolysis efficiency Prolonged start-up time VFA accumulation over time 7. Proposed System DesignMulti-Stage Leach Bed Reactor (MSLBR) SystemTFLBR Trickle flow leach bed reactorHRAD High rate anaerobic digester 8. Overview Cattle Manure Collection & Preparation Loading ReactorsManure inTFLBRWooden BlockMetal PoleSleeveWeight 9. Analytical Results 10. Total Solids (TS), Volatile Solids (VS) & Fixed Solids (FS) Approximately 23% of cattlemanure is hydrolyzed in theTFLBRs The average VS reductions(in terms of TS) was 71.8% 11. Chemical Oxygen Demand (COD)The TFLBRs undergo approximately66.32% of COD reduction due to CODleaching during hydrolysis.Approximately 44% of the total COD isleached out of the TFLBRs over the periodof six weeks. 12. Biochemical Methane Potential (BCMP) TestBCMP tests validate that leachate collected from the TFLBRs have a CH4 potential of0.43 L CH4/g COD 13. Conclusions Proposed MSLBR system is the best technology fit fordigesting high solids cattle manure produced in CO. High biogas yields from BCMP tests indicate thesuccessful hydrolysis of the cattle manure using TFLBRs Pilot scale studies monitoring the VFA concentrationsunder leachate recirculation would provide a betterunderstanding of the MSLBR system 14. Thank You 15. History of LBRs LBRs with Municipal Solid Wastes (MSWs) Initial waste saturation to improve leaching potential Inert bulking agents to avoid clogging due high density wastes Comparison between upflow and downflow leaching Sequencing between a batch of fresh and stabilized waste bed LBRs with Lignocellulosic Biomass (LB) Leachate recirculation to improve system yield Hydraulic flush to control pH/VFA concentration inside the LBR LBRs with Cattle manure Co-digestion Trickling inoculum(All the above discussed LBRs handled OSWs not more than 26% TS) 16. Objectives To design an LBR capable of handling the high solids cattle manureproduced in Colorado To evaluate the organic leaching potential of the designed LBR tocheck the extent of successful hydrolysis To optimize the operation of the designed LBR to achieve maximumhydrolysis efficiency in a single pass system 17. Evaluation of a TFLBR operation withoutleachate recirculationThree phases of reactor experiments were conducted tostudy and optimize TFLBR operation Reactor Experiments Phase I Failure of hydrolysis due to clogging Reactor Experiments Phase II Addition of straw as a bulking material Addition of a layer of dispersion media Reactor Experiments Phase III Addition of nutrients to improve bacterial activity 18. Overview Cattle Manure Collection & Preparation Pulverization Sorting System Construction & Setup Loading Reactors System Operation & Sampling Analytical Tests Total Solids (TS), Total Suspended Solids (TSS), Total DissolvedSolids (TDS), Volatile Solids (VS), Fixed Solids (FS), ChemicalOxygen Demand (COD), Total Nitrogen (TN), Total Phosphorus(TP), Total Potassium (TK) and Total Volatile Fatty Acids (TVFAs) Biochemical Methane Potential (BCMP) tests 19. Reactor Experiment Phase I Three TFLBRs (triplicate) loaded with high solids CW Water inflow rate 20 mL/min System failure within the first 24 hours- Water build-up on top of the waste bed due to clogging 20. Reactor Experiment Phase II Addition of straw as abulking material (5% bymass) Comparison betweenTFLBRs containing CWbulked with and withoutstraw Layer of fine sand on top ofwaste bed to promote waterdispersion through thecolumn 21. Reactor Experiment Phase III Addition of nutrients tocheck if the TFLBR isnutrient limited due tocontinuous leaching withoutrecirculation Comparison betweennutrient dosed and non-nutrient dosed TFLBRs Composite samplingtechnique instead ofinstantaneous sampling 22. Comparison between Phase I, II & III051015202530354045500 2 4 6 8 10 12 14 16 18 20 22 24gCOD/LleachateTime (Days)Phase II - Without Straw Phase II - With StrawPhase III - Without Nutrient Dosing Phase III - With Nutrient Dosing 23. Biochemical Methane Potential Test