on-site analytical laboratories to monitor process stability of anaerobic digestion systems
TRANSCRIPT
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
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
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.
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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AA NHV RL NH PAT SK EM
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AD systems
Online Efficiency (%) Capacity Factor
Performance of AD systems - The case of NYS
Gooch et al., 2011
88% average online efficiency
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Cap
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On
line
Effi
cien
cy (
%)
AD systems
Online Efficiency (%) Capacity Factor
Performance of AD systems - The case of NYS
57% average capacity factor
Gooch et al., 2011
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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Sampling (bi-weekly)
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NHV
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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
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
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
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
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
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
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
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
AD process monitoring labs in NYS
Case study: “ Farm X AD system”
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1/1/2011 2/1/2011 3/1/2011 4/1/2011 5/1/2011 6/1/2011 7/1/2011 8/1/2011 9/1/2011 10/1/2011 11/1/2011 12/1/2011 1/1/2012 2/1/2012
Bio
gas
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t3/m
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tpu
t (kW
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Biogas production
Power output
Power output
Biogas production
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CHP Power Output (kW)
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Effluent pH
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(g/L
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(g/L
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Effluent Volatile Solids (g/L)
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Bio
gas
( ft3 /
min
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AD Biogas Production (ft3/min)
Case study: “ Farm X AD system”
Case study: “ Farm X AD system”
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Bio
gas
pro
du
ctio
n (f
t3/m
in)
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wer
ou
tpu
t (kW
)
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)
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
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
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
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
