
2017 Performance Comparison of Biogas Anaerobic Digesters Report
2017 comparative study of biogas anaerobic digesters based on DNA sequencing of samples collected. Includes the DNA sequencing results of each sample, grouped and analyzed for each digester included in the study, and each digester type. Survey data is included to augment DNA testing. Includes pdf version available for immediate download after purchase (64 pages).
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Executive Summary
Performance Comparison of Anaerobic DigestersÂ
Anaerobic digesters are employed in wastewater, landfill and livestock operations worldwide to create renewable energy. Improving biogas production in a one-million gallon reactor by 5-10% can offset up to $200,000 annually in power costs when used for onsite power (Ling, A. 2020).
This study used 60 samples from 21 digesters representing a variety of industries, feedstocks, reactor design, and operational conditions. Microbial community data and digester operation and outcome data were used to understand the relationships between operation, community members, and outcomes.
Each digester and site studies had specific digester microbiomes that were more similar to each other than to other digesters. This suggests that microbial community results are site-specific. The community composition associated with optimum results will vary between sites. Despite this limitation, some general community trends were observed across the samples studied, and these may be used to make general conclusions about digester operation and community structure. Briefly,
- Higher relative abundances of total archaea, pseudomonads, and commomonads correlated to higher percent CH4 in produced gas
- Thermophilic conditions and blanket-type reactors correlated to higher archaea relative abundances and higher percent CH4 in produced gas
- COD removal correlated directly to CH4 production
- Higher VFA to alkalinity ratios and lower pH in the ranges observed (pH 6.7 to 7.8 and VFA : alkalinity 0.04-0.24) correlated to higher archaea relative abundances
- Digesters treating municipal wastes harbored more diverse and even communities than digesters treating only industrial wastes, possibly due to the regular addition of waste activated sludge.
Based on these results, several key microbial indicators were identified for use in tracking changes in a digester microbiome:
- Community diversity (number of microbe types)
- Community evenness (how evenly microbe types are distributed)
- Total relative abundance of:
- Total methanogens (total archaea)
- Key methanogen groups: Methanobacterium spp., Methanosaeta spp., Methanothermobacter spp.
This report also proposes several key performance indices (KPIs) based on these indicators to help operators use microbial community analysis to inform and improve system operation.
Table of Contents
Executive Summary 1
1.0 Introduction 3
Study Overview 3
Study Goals 3
Overview of Methods Used in this Study 3
Description of Samples Included in this Study 4
Study Results and Discussion 4
General Community Trends 4
Microbiome Trends by Industry Key Microbial Players 7
Hydrolytic Bacteria 11
Acidogenic and Acetogenic Bacteria 11
Methanogenic Archaea 11
Others 11
Summary of Key Microbial Groups 12
Linking Microbiome to Design and Operational Conditions 14
Reactor SRT 14
Reactor Mixing Regime 14
Temperature (mesophilic, thermophilic) 14
COD Removal 15
VFAs and VFA:alkalinity ratio 15
Nutrient concentrations in digester (ammonia, ortho-P) 16
Feedstock (primary sludge, secondary sludge, agricultural solids, high-strength liquids) 16
Chemical additives (micronutrients, iron, P) 16
pH 16
Relating Archaea Relative Abundance to Operating Parameters 16
Linking Microbiome to Digester Outcomes 17
Methane production 18
Biogas composition 18
Stability and resilience (reduce probability of upset) 18
Other issues (scum, crust, foaming) 18
Implications for Digester Performance and Operation 19
Approach to Problem Solving 19
Bio-Methane Production 19
Reactor Stability and Resilience 19
Odor Production 20
Example Dashboard 20
List of Tables
Table 1 Summary of microbial groups observed in this study 9
Table 2 Summary of microbial member differences between reactor types 10
List of Figures
Figure 1 Visualization of microbial community similarities with each digester indicated (non-metric multidimensional scaling) 4
Figure 2 Visualization of microbial community similarities with municipal and industrial indicated (non-metric multidimensional scaling) 5
Figure 3 Diversity and evenness for municipal and industrial samples 6
Figure 4 Summary of microbial community composition 7
Figure 5 Visualization of microbial community similarities with mesophilic versus thermophilic reactors indicated and methanogen groups shown in blue (non-metric multidimensional scaling) 11
Figure 6 Predicted versus actual percent archaeal abundance 13
Figure 7 Digester operations and performance as related to microbiome and KPIs 15
Figure 8 Example Microbe Detectives Digester Dashboard 16
List of Appendices, Attachments, or Exhibits
Appendix A Study Methods
Appendix B Additional Figures and Correlations

Key findings presented at the Microbiome Water Summit
The Microbiome Water Summit was held on September 29th 2017 at the Shedd Aquarium in Chicago, Illinois. The summit featured leaders in this ground-breaking field of work. View key findngs of the study, presented by Dr. Alison Ling in the Summit video below.
“With specialized DNA sequencing that is being applied in these studies, the resource recovery industry finally has the opportunity to measure the microbiology much more comprehensively than what has been previously possible. The studies will help the industry interpret results and use this new insight to optimize systems. I believe this will be a game-changer for the industry.” –Jeremy Cramer, Sr Process Eng., Donohue & Associates
Biogas Study:Â Summary & Key Findings (60 minutes) by Dr. Alison Ling, Barr Engineering
Panel Moderator: Jeremy Cramer, Senior Process Specialist, Donohue & Associates
Autumn Fisher, Superintendent, City of Fond du Lac
Chris Lefebvre, Wastewater Superintendent, Stevens Point, Wisconsin
Nick Menninga, General Manager, Downers Grove Sanitary District
Kamlesh Patel, Senior Environmental Research Scientist, MWRD of Greater Chicago
Technical and Operational Advisory Group

Dr. Ling served as the principal author of this report. She is an environmental engineer with Barr Engineering Company in Minneapolis, MN. At Barr, she is engaged in front-end design and troubleshooting for water and wastewater treatment projects. Read more...

Dr. Trevor Ghylin is a professional water process engineer and has more than a decade of experience working for CH2M, the leading consulting firm in the water industry and also a senior process engineer for Xylem, a multi-billion dollar pure play water technology company. Read more...

Dr. V. P. Tale has been working in the field of anaerobic digestion technology since year 2004 and his work in this field has been published through several peer reviewed journal articles, conference proceedings and provisional patent applications. Read more...

Dr. Leon Downing is a senior technologist with CH2M and serves as the East Region Technology Lead. A graduate of the University of Wisconsin-Platteville, Leon then received his M.S. and PhD from the University of Notre Dame, focusing on process modeling and energy efficient biological nutrient removal. Read more...

Kellen Lauer is an Environmental Specialist with Environmental Business Specialists (EBS), focusing in molecular microbiology. She came to EBS in August 2015 to develop a molecular biology lab with capabilities for quantitative PCR analysis of wastewater systems. Read more...

Jeremy Cramer has 18 years of wastewater and water treatment experience. He is a licensed water and wastewater operator in the state of Wisconsin. Throughout his career, he has been involved in the management, operation, and maintenance of both wastewater and water treatment systems and facilities. Read more...

Bryan Johnson, P.E., is a seasoned civil and environmental engineer with 30 years of experience in renewable bioenergy with a particular focus in biogas energy. Through the combination of his formal education and work experiences, Mr. Johnson has successfully developed well in excess of $100M in bioenergy opportunities. Read more...

David Ellis P.E., started working with municipal sewage anaerobic digestion systems 25 years ago. Building on that experience, he has worked on large scale digesters for multi-national food-industry clients for 20 years, since before many folks had heard of green-house gases. In those days, biogas was simply a matter of good business. Read more...
