on-site analytical laboratories to monitor process stability of anaerobic digestion systems
TRANSCRIPT
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ON-SITE ANALYTICAL LABORATORIES TO MONITOR
PROCESS STABILITY OF ANAEROBIC DIGESTION SYSTEMS
From Waste to Worth: Spreading Science & Solutions
Denver, Colorado ∙ April 1 – 5, 2013
Rodrigo Labatut, Ph.D.Postdoctoral Associate
Biological & Environmental Engineering
Cornell University
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Overview of anaerobic digestion (AD) in the U.S.
o 186 on-farm anaerobic digesters in the U.S. (EPA, March 2012)
Wisconsin: 28
New York: 25
Pennsylvania: 23
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Increasing number of on-farm AD operations co-digesting manure with food wastes
Increased biomethane yields
Increased revenue by generated tipping fees
Increased project feasibility
Overview of anaerobic digestion (AD) in the U.S.
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Performance of anaerobic digestion systems
Up to 1998, failure rates were at (Lusk, 1998):
• 63% Plug-flow reactors
• 70% Continuously-stirred tank reactors
2013
Better design and engineering numbers likely to be lower
BUT, inadequate system management and control persists…
Consequences (AD, CHP)
• Inconsistency
• Underperformance
• Short-term failure
Examples in MI, OH, NY…
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Online Efficiency (%) Capacity Factor
Performance of AD systems - The case of NYS
Gooch et al., 2011
88% average online efficiency
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Online Efficiency (%) Capacity Factor
Performance of AD systems - The case of NYS
57% average capacity factor
Gooch et al., 2011
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Performance of AD systems - The case of NYS
Reasons for low CHP performance:
1. Decreased/unstable biogas production
2. Decreased/unstable biomethane content in biogas
3. Downtime of CHP unit due to AD system failure
4. Decreased efficiency of CHP system
5. Over-dimensioning of CHP system
6. Downtime of both AD and CHP systems due to maintenance
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Responsibilities: operate, maintain, and monitor both AD and CHP systems in addition to his/her daily farm-related activities.
Nearly all active on-farm AD systems in NYS are operated by a farm worker, who usually has no previous experience or training in AD!
Performance of AD systems - The case of NYS
Gooch et al., 2011
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Implications of low AD system performance/failure
1. Decreased energy generation
Data from US EPA (2012) from 157 operating AD systems with CHP units in the U.S.
Total of 83,738 kW electrical capacity
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Implications of low AD system performance/failure
1. Decreased energy generation
83,738 kW electrical capacity
In a well-operated AD system with a CF = 0.9, this translates into:
• 660 GWh of total energy produced per year, an equivalent to power 57,428 U.S. households for an entire year
• $33 million in revenues, if sold to a utility company in NYS ($0.05/kWh)
BUT, with a CF = 0.57 an AD system will:
• Power 21,057 less households
• Produce $12 million less in revenue
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2. Co-substrates
In co-digestion operations, if AD system failure occurs:
• NO tipping fees if farm cannot receive external substrates
Tipping fees are the economic driver of most on-farm AD systems in the US!
• If contract obligates farm to receive substrates, then where to store them?
If stored in an open lagoon, odor and greenhouse gases are no contained
Implications of low AD system performance/failure
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Operator training and AD monitoring labs in NYS
Manure Management Program at Cornell University
(NYSERDA founded project)
Goals:
1. To train and support a workforce of AD operators and technicians inNYS
2. To implement analytical labs on selected on-farm AD systems tomonitor key process parameters
3. To improve performance, detect process upsets more efficiently,and prevent system failure
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Key process indicators to prevent digester upsets
• Retention time
• Balanced feed
• Adequate nutrients
• Right environmental conditions
2-3 days 22 days
Digesters are like cows!
Yes Yes
Yes Yes
Yes Yes
High quality /production milk
High quality /production biogas
Result
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Parameter Determination method
pH pH meter/single-junction electrode
Temperature pH meter/thermocouple
Total alkalinity (ALK) Titration of sample with sulfuric acid 0.1 N to pH 4.0
Volatile fatty acids (VFA) Distillation of sample and titration of distillate with
sodium hydroxide 0.1 N to pH 8.3
VFA/ALK Ratio Titration method (adapted from Kapp, 1984)
Total solids (TS) Drying sample in gravity convection oven at 105oC
overnight (> 8 h)
Total volatile solids (VS) Ashing sample in muffle furnace at 550oC for 1 h
Methane content By difference of carbon dioxide content, measured
using sensidyne tubes
Total ammonia-nitrogen
(TAN)
Ion meter/ion selective electrode
AD process monitoring labs in NYS
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Parameter Determination method
pH pH meter/single-junction electrode
Temperature pH meter/thermocouple
Total alkalinity (ALK) Titration of sample with sulfuric acid 0.1 N to pH 4.0
Volatile fatty acids (VFA) Distillation of sample and titration of distillate with
sodium hydroxide 0.1 N to pH 8.3
VFA/ALK Ratio Titration method (adapted from Kapp ,1984)
Total solids (TS) Drying sample in gravity convection oven at 105oC
overnight (> 8 h)
Total volatile solids (VS) Ashing sample in muffle furnace at 550oC for 1 h
Methane content By difference of carbon dioxide content, measured
using sensidyne tubes
Total ammonia-nitrogen
(TAN)
Ion meter/ion selective electrode
AD process monitoring labs in NYS
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AD process monitoring labs in NYS
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Case study: “ Farm X AD system”
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Biogas production
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Case study: “ Farm X AD system”
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Case study: “ Farm X AD system”
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Bio
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Biogas production
Power output
Power output
Biogas production
• Plug-flow/CSTR AD system
• Need to find the correct sampling place, after VFAs spike (hydrolysis/fermentation stages)
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Digester operational parameters
• Organic loading rate (OLR)• Loading frequency• Temperature • Mixing frequency/speed
Substrate/feedstock characteristics
• Solids content (TS, VS)• Co-digestion ratio• Co-substrate chemical strength
Process perturbation
Digester upset
AD systemfailure
• Steady increase VFA concentrations, or VFA/ALK ratio
• Increase H2 partial pressure
• High VFA (i.e. acetate, propionate) • High H2 concentrations• Lower pH (sour digester)• Decreased biogas production• Decreased methane content• Decreased VS stabilization
• Biogas production stopped• AD system failure• CHP system down
Rel
ativ
e ti
me
Anatomy of an AD process perturbation
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Conclusions
• Study in NYS: <60% of electric energy potential due to poor AD performance and system failure
Inadequate management and process control to blame
• Well-trained and qualified personnel to operate and monitor AD systems the process is essential
Prevent digester upsets and potential system failures
Efficient organic waste stabilization and stable biogas production
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Conclusions
• Monitoring labs installed on selected farm-based AD systems in NYS
Monitor key process parameters and detect process upsets more efficiently
• Measured process parameters (i.e. VFA, VFA/ALK ratio) are good indicators of process upsets
• Potential to identify and correct the source of the problem before system failure occurs
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Acknowledgements
The authors would like to acknowledge the following farms for their willingness to participate in this project:
• Sunnyside• Roach• Sheland• Synergy• SUNY Morrisville
Special thanks to the lab operators!
• Don Kulis• Gary Mutchler• Doug Shelmadine and Sons • Randy Mastin• Ben Ballard and his students
New York State Energy Research and Development Authority (NYSERDA) for funding in support of this work