Anaerobic Digestion Monitoring at Synergy Biogas, LLC

78 Pages·2014·1.65 MB·English

by  Rodrigo Alejandro Labatut

Dairy Environmental Systems Program
www.manuremanagement.cornell.edu

Anaerobic Digestion Monitoring at Synergy Biogas, LLC
Cornell University Agreement No. 65961

FINAL REPORT
“EVALUATION OF THE CONTINUOUSLY-MIXED ANAEROBIC DIGESTER SYSTEM AT
SYNERGY BIOGAS FOLLOWING THE PROTOCOL FOR QUANTIFYING AND REPORTING THE
PERFORMANCE OF ANAEROBIC DIGESTION SYSTEMS FOR LIVESTOCK MANURES”
(JUN 2012 TO MAY 2014)

Prepared for
Wyoming County Industrial Development Agency (WCIDA)
Perry, NY
Mr. James Pierce
Executive Director/CEO/CFO, WCIDA

Prepared by
PRO-DAIRY Program
Department of Biological and Environmental Engineering
Cornell University
Ithaca, NY

Curt A. Gooch, P.E. Rodrigo Labatut, Ph.D.
Principal Investigator Postdoctoral Associate

November 20, 2014
Dairy Environmental Systems Program

www.manuremanagement.cornell.edu

NOTICE

1
This report was prepared by Rodrigo Labatut and Curt Gooch P.E. in the course of performing
work contracted for and sponsored by the Wyoming County Industrial Development Agency
(hereafter WCIDA). The opinions expressed in this report do not necessarily reflect those of
WCIDA, and reference to any specific product, service, process, or method does not constitute an
implied or expressed recommendation or endorsement of it. Anaerobic digestion (AD) systems are
dynamic in nature, and tend to have elements that are subject to change according to management
decisions made on the plant. The farm and digester information in this report was specific to the
time period the performance evaluation took place, and could be substantially different at other
points in time.
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Licensed in the State of Maryland, No. 22020

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TABLE OF CONTENTS

Notice ....................................................................................................................................................................................... - 2 -
Table of Contents ................................................................................................................................................................ - 3 -
Ex ecutive Summary ........................................................................................................................................................... - 9 -
1. In troduction ............................................................................................................................................................. - 11 -
1.1. Overview .......................................................................................................................................................... - 13 -
1.1.1. Farmstead ..................................................................................................................................................... - 13 -
1.1.2. Anaerobic Digestion (AD) System ....................................................................................................... - 14 -
2. M ethods and Materials ........................................................................................................................................ - 20 -
2.1. Data Collection .............................................................................................................................................. - 20 -
2.2. Sample Collection ......................................................................................................................................... - 21 -
2.3. Instrumentation and Equipment ........................................................................................................... - 22 -
3. R esults ........................................................................................................................................................................ - 25 -
3.1. Digester Influent: Dairy Cattle Manure ............................................................................................... - 31 -
3.2. Digester Influent: Co-substrates ............................................................................................................ - 32 -
3.3. Physicochemical characterization and nutrients analysis .......................................................... - 39 -
3.4. Effect of Anaerobic Digestion on Constituents: Waste Stabilization ...................................... - 53 -
3.5. Biogas characterization and production ............................................................................................ - 58 -
3.5.1. Biogas composition: anaerobic digester .......................................................................................... - 58 -
3.5.2. Biogas composition: biological scrubber ......................................................................................... - 60 -
3.5.3. Biogas production: normalized by number of cows .................................................................... - 62 -
3.5.4. Biogas production: normalized by influent biomass .................................................................. - 63 -
3 .5.5. Biogas energy .............................................................................................................................................. - 64 -
3.6. Biogas utilization .......................................................................................................................................... - 65 -
3.6.1. Electrical energy ........................................................P...R...O...-..D....A...I..R...Y... ..P..r..o..g...r.a...m... .-.. .C...o...r..n..e..l.l.. .U....n..i.v...e..r.s..i..t y- 6- 53 --
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3.6.1.2. Biogas to electricity and thermal conversion efficiency ................................................... - 66 -
3.6.1.3. Capacity factor and online efficiency ........................................................................................ - 68 -
3.6.2. Thermal energy .......................................................................................................................................... - 70 -
4. A D System Economics .......................................................................................................................................... - 71 -
4.1. Capital cost and grants received ............................................................................................................ - 71 -
4.2. Source of revenues ...................................................................................................................................... - 71 -
5. Summary and Conclusions ................................................................................................................................. - 74 -
6. References ....................................................................... .......................................................................................... - 78 -

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List of Tables

Table 1. Monitoring sampling and data collection period schedule over the entire project (June

2012 to May 2014). ......................................................................................................................................................... - 12 -

Table 2. General information about Synergy Dairy livestock operation. ................................................. - 13 -

Table 3. AD system design assumptions and characteristics. ....................................................................... - 19 -

Table 4. Data collected/measured on-site at each sampling date. .............................................................. - 20 -

Table 5. Data obtained from the SCADA system for each period. ................................................................ - 21 -
Table 6. Standard analytical methods used by CES laboratory for sample analyses. ......................... - 22 -

Table 7. Ranges and precision of the portable, on-site gas measuring device used for monitoring

(Multitec 540). .................................................................................................................................................................. - 24 -

Table 8. Specifications of equipment used in performance evaluation data collection. .................... - 24 -
Table 9. Monitoring summary data. ......................................................................................................................... - 26 -

Table 10. Monthly animal management group average populations and calculated manure
produced. ............................................................................................................................................................................ - 31 -

Table 11. Basic description and classification of wastes imported by Synergy since the start of the
monitoring. ......................................................................................................................................................................... - 33 -

Table 12. Monthly volume (gal) of co-substrates received per source during the entire monitoring

project (June 2012 – May 2014). ............................................................................................................................... - 34 -

Table 13. Digester influent mixed characterization (average of triplicates). ......................................... - 40 -

Table 14. Digester effluent characterization (average of triplicates). ....................................................... - 42 -

Table 15. Raw manure characterization (average of triplicates). ............................................................... - 44 -
Table 16. Imported waste characterization (average of triplicates).......................................................... - 45 -

Table 17. Overall statistics of the digester influent mixed and digester effluent characteristics over

the entire monitoring project. .................................................................................................................................... - 46 -

Table 18. Estimated mass and ratio of nutrients in the digester influent by monitoring period. .. - 48 -

Table 19. Estimated mass and ratio of nutrients in the digester effluent by monitoring period. .. - 50 -

Table 20. Estimated mass and ratio of nutrients contributed by raw manure. ..................................... - 52 -

Table 21. Estimated mass and ratio of nutrients contributed by imported waste............................... - 52 -

Table 22. Calculated water vapor density of biogas for each sampling date. ......................................... - 59 -

Table 23. Initial capital costs for the Synergy Biogas AD system. ............................................................... - 71 -
Table 24. Net energy sold and potential revenues from PeRleOct-rDicAitIyR aYn Pdr RogErCa’ms s -a Cleosr bneyl lm Uonnitvhe.r .s..i.t. y- 7- 35 --
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Table 25. Statistics of main parameters obtained during the 24 months of monitoring project;
values are per sampling period. ................................................................................................................................ - 75 -

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List of Figures

Figure 1. Aerial view of the Synergy Biogas AD system and Synergy Dairy farmstead. The lactating ..

cow barns are on the left side of the picture, while the anaerobic digestion system is located on the
right side. ............................................................................................................................................................................ - 14 -
Figure 2. Synergy Biogas AD system flow diagram (simplified); meters and sampling locations are

identified in circular labels; segmented biogas line between CHP and boiler denotes previous
configuration (see text). ................................................................................................................................................ - 16 -

Figure 3. Continuously-stirred tank reactor (background) and pasteurization units (foreground)
. ................................................................................................................................................................................................ - 17 -
Figure 4. Daily loading rate, co-digestion ratio (food waste to influent), biogas production, and CHP

instant power at the Synergy AD system during the two years of monitoring (May 2012 – May
2014). ................................................................................................................................................................................... - 30 -

Figure 5. Percent contribution (volume basis) of each imported waste to the Synergy digester
based on industry sector and waste characteristics. ........................................................................................ - 38 -
Figure 6. Percent change in chemical parameters’ concentrations in the digester effluent relative to

the influent for each sampling date; a positive change represents a decrease, while a negative
change represents an increase. .................................................................................................................................. - 55 -
Figure 7. Top: average mass of constituent in the digester influent and effluent for the entire
monitoring project; Bottom: average percent change in constituent mass in the digester effluent

relative to the influent for the entire monitoring project; error bars represent the standard
deviation. ............................................................................................................................................................................. - 56 -
Figure 8. Percent contribution of total volatile solids, VS (blue bar), and fixed solids, FS (red bar) in
i.e.,
the AD influent (top) and effluent (bottom) for sampling dates; total solids represent 100% of the
dry influent material ( VS + FS). .......................................................................................................................... - 57 -

Figure 9. Methane and carbon dioxide content in biogas measured at each sampling date from the
digester vessel headspace on a dry biogas basis (moisture corrected). .................................................. - 60 -

Figure 10. Concentration of hydrogen sulfide before and after the biological scrubber and its
corresponding efficiency at each sampling date. ............................................................................................... - 61 -
Figure 11. Average daily biogas production per lactating cow (LC) contributing to the digester

observed for each period; the number shown on top of the bars is the average lactating cows for the
corresponding period. ..................................................................P...R...O...-..D...A....I.R....Y... .P...r..o..g..r..a..m.... .-.. .C...o...r.n...e..l.l.. .U...n...i.v..e...r.s..i.t. y- 6- 27 --
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Figure 12. Average specific biogas production as a function of the total influent biomass observed
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for each period; the number on top of the bars indicates the ft per lb of biomass. ............................ - 63 -

Figure 13. Total energy (MMBtu) produced by the anaerobic digester for each period. ................. - 64 -
Figure 14. Average daily electrical energy production by CHP observed for each period. ............. - 66 -

Figure 15. Volume of biogas required to generate a unit of electrical energy (kWh) and thermal

conversion efficiency of the engine-generator set calculated for each period. ..................................... - 67 -

Figure 16. Capacity factor and online efficiency calculated for each period. ......................................... - 69 -
Figure 17. Breakdown of problems generating downtime at Synergy. .................................................... - 69 -
Figure 18. Thermal energy recovered from CHP (MMBtu) and percent of recovered energy to the

total energy produced by digester (see Figure 13) for each period. No data available from Periods 1
– 8 and for Period 12. ..................................................................................................................................................... - 70 -
Figure 19. Monthly electrical energy generated/sold and parasitic load of the Synergy AD system

throughout the monitoring; No parasitic load data were available from Jun to Sep 2012 and for
April 2014. .......................................................................................................................................................................... - 72 -

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EXECUTIVE SUMMARY
The Synergy Biogas, LLC anaerobic digester system was monitored for two years, from June 2012 to
May 2014, using the EPA Protocol for Quantifying and Reporting the Performance of Anaerobic
Digestion Systems for Livestock (EPA, 2011), as a guideline. The Synergy Biogas anaerobic
digester, supplied by CH4 Biogas, LLC, was a continuously-stirred tank reactor operated in the
mesophilic temperature range, designed to co-digest multiple off-farm streams with dairy manure
and produce the necessary biogas to power a 1.4-MW internal combustion engine-generator set.
During the monitoring, effluent solids were separated and used by the Synergy farm for cow stall
bedding, while the separated liquid was stored in the farm’s uncovered earthen long-term storage
for use as cropland fertilizer.

For the entire monitoring project, an average of 1,891±62 lactating cows per day from Synergy
Dairy contributed manure to the digester. The average daily loading rate of the digester was
80,408±19,266 gal, where the average percent of imported waste (mostly food-grade residues) co-
digested with manure was 25±6% on a volume-to-volume (v/v) basis. The average reduction of
organic matter thru the monitoring project was 42% with respect to the influent, while 75% of the
odor-causing volatile fatty acids were reduced. In comparison, a previous monitoring study
reported by the authors in five manure-based co-digestion operations showed a reduction in
organic matter and volatile acids between 36% and 53% and 85% and 91%, respectively (Gooch et
al., 2011). The average daily digester biogas production for the entire monitoring project was
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495±78 ft per 1,000 lbs of total influent added to the digester, or 173±34 ft per cow contributing
to the digester. The engine-generator set produced an average of 23±7 MWh of electricity per day,
from which the average daily parasitic load of the AD system was 3±1 MWh, accounting for
approximately 14% of the electricity generated by the plant. Overall, the average capacity factor
and online efficiency of the Synergy AD system during the entire monitoring project were 0.66±0.22
and 80±23%, respectively. The electrical energy generated translated into an overall thermal
conversion efficiency of 42±4%. Also, an additional 13±5% of the total energy in the biogas was
recovered by the engine as hot water. Thus, an overall 55% (electrical + thermal) of the total
energy contained in the input biogas was recovered by the engine-generator set during the
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monitoring project.
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The majority of the challenges experienced by the Synergy AD system were of mechanical origin,
whereas 20% were related to the biological process; only 8% of the downtime was due to
scheduled systems maintenance. Some of the problems were related to the extreme cold conditions
experienced in the Northeast during the period from December 2013 to February 2014. According
to NOAA’s National Climatic Data Center, this period was the 34th coldest for the contiguous 48
states since modern records began in 1895, with an average temperature of 31.3F, 1.0F below the
20th century average (NOAA, 2014).

A summary of the most relevant data produced during the 24 months of this project is shown in the
tParboljee bcet lSouwm. mary. Statistics of main parameters obtained during the monitoring project per
month (i.e., sampling period).
System parameters Average Standard deviation
Lactating cows contributing to digester 1,891 62
Influent biomass (gal) 2,377,329 727,410
Digestate volume (gal) 1,852,882 434,644
Co-digestion (% imported waste) 25 6
Hydraulic retention time (d) 29 7
Electrical energy generated (MWh) 671 258
Instantaneous power (MW) 0.94 0.31
Plant capacity factor (decimal) 0.66 0.22
Plant online efficiency (%) 80 23
CHP thermal efficiency (%) 42 4

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