Evaluation of a Trickle Flow Leach Bed Reactor for Anaerobic Digestion of High Solids Cattle Waste
-
Upload
lpe-learning-center -
Category
Education
-
view
563 -
download
2
description
Transcript of Evaluation of a Trickle Flow Leach Bed Reactor for Anaerobic Digestion of High Solids Cattle Waste
EVALUATION OF A ‘TRICKLE FLOW LEACH BED REACTOR’ FOR ANAEROBIC DIGESTION OF HIGH SOLIDS CATTLE
MANURE
Authors: Asma Hanif – Graduate Research Student, Colorado State University
Lucas Loetscher, Graduate Research Assistant, Colorado State University
Sybil Sharvelle - Assistant Professor, Colorado State University
Kelly Wasserbach – Graduate Research Assistant, Colorado State University
Introduction
Colorado – Second highest producer of cattle manure in the 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
BackgroundOperational anaerobic digesters in the US as of September 2012 (Source: EPA)
Anaerobic digestion in Colorado
Second highest producer of cattle manure in the US yet
no operational digesters
Reasons:
o Arid climate - Produced cattle manure is very dry (approximately
90% total solids)
o Limited water resources
Types of anaerobic digesters
Leach Bed Reactors (LBRs)Advantages:
• High solids reactor
• Low water requirements
• Low energy requirements
• Good methane yields
Limitations:
• Reactor clogging leading to lower
hydrolysis efficiency
• Prolonged start-up time
• VFA accumulation over time
Proposed System Design Multi-Stage Leach Bed Reactor (MSLBR) System
TFLBR – Trickle flow leach bed reactorHRAD – High rate anaerobic digester
Overview• Cattle Manure – Collection & Preparation
• Loading Reactors
Manure in TFLBR
Wooden Block
Metal Pole
Sleeve
Weight
Analytical Results
Total Solids (TS), Volatile Solids (VS) & Fixed Solids (FS)
• Approximately 23% of cattle
manure is hydrolyzed in the
TFLBRs
• The average VS reductions
(in terms of TS) was 71.8%
Chemical Oxygen Demand (COD)
The TFLBRs undergo approximately
66.32% of COD reduction due to COD
leaching during hydrolysis.
Approximately 44% of the total COD is
leached out of the TFLBRs over the period
of six weeks.
Biochemical Methane Potential (BCMP) Test
BCMP tests validate that leachate collected from the TFLBRs have a CH4 potential of 0.43 L CH4/g COD
Conclusions• Proposed MSLBR system is the best technology fit for
digesting high solids cattle manure produced in CO.
• High biogas yields from BCMP tests indicate the successful hydrolysis of the cattle manure using TFLBRs
• Pilot scale studies monitoring the VFA concentrations under leachate recirculation would provide a better understanding of the MSLBR system
Thank You
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)
Objectives
• To design an LBR capable of handling the high solids cattle manure produced in Colorado
• To evaluate the organic leaching potential of the designed LBR to
check the extent of successful hydrolysis
• To optimize the operation of the designed LBR to achieve maximum
hydrolysis efficiency in a single pass system
Evaluation of a TFLBR operation without leachate recirculation
Three phases of reactor experiments were conducted to
study 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
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 Dissolved Solids (TDS), Volatile Solids (VS), Fixed Solids (FS), Chemical Oxygen Demand (COD), Total Nitrogen (TN), Total Phosphorus (TP), Total Potassium (TK) and Total Volatile Fatty Acids (TVFAs)
• Biochemical Methane Potential (BCMP) tests
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
Reactor Experiment – Phase II• Addition of straw as a
bulking material (5% by mass)
• Comparison between TFLBRs containing CW bulked with and without straw
• Layer of fine sand on top of waste bed to promote water dispersion through the column
Reactor Experiment – Phase III• Addition of nutrients to
check if the TFLBR is nutrient limited due to continuous leaching without recirculation
• Comparison between nutrient dosed and non-nutrient dosed TFLBRs
• Composite sampling technique instead of instantaneous sampling
Comparison between Phase I, II & III
0 2 4 6 8 10 12 14 16 18 20 22 240
5
10
15
20
25
30
35
40
45
50
Phase II - Without Straw Phase II - With Straw
Phase III - Without Nutrient Dosing Phase III - With Nutrient Dosing
Time (Days)
g C
OD
/ L
leac
hat
e
Biochemical Methane Potential Test