Anaerobic Digesters for Dairy Farms - Manure Management

76 Pages·2012·5.01 MB·English

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AGRICULTURAL AND BIOLOGICAL i
ENGINEERING

EXTENSION BULLETIN 458

ANAEROBIC DIGESTERS
FOR DAIRY FARMS

by
RK. Koekeh, EE, Fabian, RW. Guest, J.K. Campbell

Summary: Fundamentals of the pradustion of biogas (methane anc
Carbon dioxide) on dairy farms are presented, Practical
considerauons for compasbiity of a digester with farm

] amuse managemen and labor practices are discussed. An

teatimtte of digester size, energy production, and economic

Key Words: snacrobic digester, biogas, methane, cogeneration, mimare
‘management

LEGAL NOTICE

“This report was prepared as an necount of work partially sponsored

‘by the New York State Energy Research and Development Authorcy
the Energy Authority) andthe Niagi, Mobaw Corporation
MPC), Neither the Energy Authority, NMPC, nor any person

‘eding on behalf of them:

Makes any warranty or representation, express or implied,
with respect to the accuracy, completeness, or usefulness of
information contained herein, oF that the use of any information,

eratus, mellod, or process disclosed in the bulletin may not
infringe upon privately owned rights, or

Assumes ay laity with esos the ue of of for
damages resulting from the use of, any information, apparatus,
‘method, oF process disclosed inthis bulletin.

DEPARTMENT OF
AGRICULTURAL AND BIOLOGICAL ENGINEERING
[NEW YORK STATE COLLEGE OF AGRICULTURE AND LIFE SCIENCES
‘A STATUTORY COLLEGE OF THE STATE UNIVERSITY
[AT CORNELL UNIVERSITY, ITHAGA, NEW YORK 14853
ACKNOWLEDGEMENTS

Bye flowing darren sno nucle peers mate ly one
+ Mr. Peter Huatingion at Cooperstown Holstein Corporation Firm: Cooperstown, NY
+ Dr Stanley Wocks ut The Agnay Fann Research Center dry, Tully, NY
+ Mr. Ronald Space, Sr, and Mr. Ronald Space, Jt at The Millbrook Farms Freeville, NY
+ Mr, Charles Johnson and Mt, Gary Johnson atthe Jobson Farm: Chester, NY

The ae of rade maes in is bulletin ior ienfication of egulpant and does not conse om endorsement of
4 product by the New York State Collegeof Agriculture and Life Sciences at Cornell Onley
‘Table of Contents

Anaerobic Digesters on New York State Dairy Farms...

Fundamentals of Anaerobic Digestion System..
“Types of Digester, 3

Matching a Bioges System to an Individual Farm, 8
‘Compatibility of Anaerobic Digestion Technology with Dairy... 8
“Manure Management... 8
“Farin Labor Considerations 9
Off Farm Resources... 9
Site Considerations 7 : °
“Worksheet I: Compatibility of Anaerobic Digestion Technology with Dairy 10
Fastimation of Component Size and Energy Production... des 2
Worksheet Il; Estimation of Component Size and Energy Production. B
[Estimation of Economic Benefits a 4
~Worsheet Il: Estimation of Economic Renefis. 1s
Anaerobic Digester Design & Construction. .... ”
Digester Size, 8
“Plug.Flow Digester 18
‘Mixed Digester... 19
‘Construction Materials 20
Digester Structure. 20
Heat Exchanger a

2

2B

24

u

ru

28

“Insulation Type and Placement... 8
Heating System... 30
“Size and Placement of Heat Exchanger a
Manure FIOW 00 © a

of Heating, Fuel

Replacemen:
Cogeneration of Electricity and Water. 6
AB gino een 37

~Generator
—Conitols...

“Heat Recoves
Cogencrator System Design Considerations...
Comming te Cogeenar the Bigs System
Housing...
Electrical Systera
Water

Gas Storage... - 46
Safety een : 48
Applicable Codes, Regulations and Standards. 8

Management of an Anaerobic Digestion System. Ne 5
Digester System Management. .

Appendix A:
‘An Overview of The Millivook Farr Anserobic Digester. 66
An Overview of The Agway Furm Research Center Anaerobic Digester o
‘An Overview of The Cooperstown Holstein Corporation Farm Anaerobic Digester...
List of Figures and Tables

Eu Title
Anaerobic digester atthe Millbrook Farm in Torpikins County, NY.
2 Amzu digest he Coopersown Has Corporation Farm in Osego
‘County.

i
3 Anaerobic digeser atthe Agway Farm Research Center in Onondaga County. NY. 2
4 Anaerobic digestion system componcnts; manure handling: digester; biogas uilization 3
5 Two phases of methane production by anaerabic digestion... 3
{6 Biogas production is optimized at about 100°F digester temperature, 4
7. Hydraulic retention time influence an biogas production. a
Basic digewer types...» 5
9 ‘Thepeoprin er marr tha evenly convert io biogas al 7
10 Plug-flow digester flow diagram... . ”
Li Mixed digester flow diagram. 0
12 Plug-low digester dimensions - 9

13. Mixed digester dimensions. 20

1éScrimreinforement of synthetic rubber or plastic ins 2

15 Ladson cylindrical mixed digester wal... 3

16 Ladson plup-flow digester wall (partially below grade)... ra
17 Typieal aperitif plg-sow dgeser val desig oun frees. %6
18 Anchoring system fora flexible cover, 2 : 8

19 Insulation placement ina plug-flow digester... 2»

20 insulation Placervent in a cylindrical mixed digester 0

21 Sipe pipe et exchanger defor Coopersown Hosa digs oneveve 3

22 Simplified heating loop in plug-OW digeME nnn so HR

23 _Exittraps for effluent ima cylindrical mined digester

24 _Exiteaps for effluent in aplug-flow digester. 3

25 Primary gases constituting biogas 35

25 Volume af biogas with energy oft gallon of dese! fel 35

27 Continuous copenerator operation and typical farm demand. 36

28 Four components ofa cogenerator. 7

39 Panel operation ofa generate with public ay: exact matching voltage,

frequency, and phasing. Of MeqUEMEY.rorn-— 38

10 Typical eageneator and conta pune fr bingat production on ry fan »

31 Heat recovery system used by cogenerator, 0

32 Possible housing layout for cogenerator 2

33 Layout of heat recovery. system... a

34 Simple manometes for monitoring gas pressure : “4

35 Simple devices for maximum pressure clic! valve and condensate puma 44

36 Variable volume low pressure storage. .asa.sr coe M6

37. Medium pressure siorage of biogas... 46

38 High pressure siorage of biogas. a

39 Suggested localion of temperature probes in digesters 54

40 Method ofinsaliing thermocouple in digester for easy pai. ot

441 Effect of pat load or rich air-fuel mixture on copeceration efficiency 2
Tile

Recommenited propeties fora flexible gas cover on a digester.
Covermaterial characteristics.
Strobe on pipe (cet forbiogws.

ested dimensions for a flexible biogas collection cover,
fen transfer coefficients of digester heating gids...
Combustion properties ef gascous fuels...
Summary of key design specifications fora cogeneraor
‘Tora amount of biogas that can be scrubbed by one bushel of sponge.
Storage needs for one-half day of ges production
Suggested procedures for minimizing poten! Iza siatn intoe

Section of ar tmarobe digests

‘Summary sheet for monitoring digester performance...
“Troubleshooting Guide:
Part, Materials Handling.
Par I. Heating Systeras en
Part II, Digester Gas. System...
Part IV, Toxickey.
‘Guidelines for interpreting oil analysis test data...
Primary peevenive rmintenance shedule fora cogenerator operated continuously
‘Summary sheet for monitoring cogenerstor performance
ANAEROBIC DIGESTERS ON NEW YORK STATE DAIRY FARMS

Figure 1. Anaerobic digester atthe Millbrook Farm in tompkins County, NY.

‘The information in this bulletin is based upon engineering principles of anaerobic digesters,
esearch at Comell University, and facts learned from a three-year smdy of three New York State
Gniry farm digester operations. This three-year demonstration project serves as the basis for
‘Snaragement information in this bulletin.’ Three digescers in Tormpkins, Onondaga, and Orsego
‘Counties were monitored forthe three-year study and are described in Appendix A.

Figure 2. Anaerobic digester atthe Cooperstown Holstein Corporation Farm in Otsego County, NY.

1 on Farm Biogas Systems Information Disseiation Proj, fund by the New York Sta Eoeay Research and
Dovelapment Aubority, gars Msbswk Power Corpeaton an Corel! University,
ry

Anaerobic digesters convert organic material in manure into a mixture of methane, carbon dioxide
and other trace gases called biogas. The digester is an oxygen-free (anaeroble) environment where
microbes preseat in manure produce the biogas. The biogas can be utilized in the same manner £3
ratural ga5 oF LP gas.

‘The economic pay-back for adigestion installation depends upon the price of energy being replaced
by biogas at te farm. When compared with “alternative energy sources such as wind or solar
energy, anaerobic digesters'on dairy farms possess an advantage of a constant source of rew
‘matesial—cow manure, Some digesters have been insalled on dairy fans for reasons other tha
the economic justification of lowering energy cost with odor contol being a main reason, A few
dlairy farms ate using digesters along with solid separators (For bedding), since the digestive
Droces provides a beter feed material forthe solid separators. Anaerobic digesters are alo Used t
educe odors in cow manare to be spread on fields nea residential areas.

Similar management and maintenance requirements are associated with both small and large
<igestion operations. Capital cost for construction and purchase of digestion equipment will not
double as the size of the farm's project doubles. For these reasons, most economically viable
Aigesters have been installed on large and well-managed dairies,

‘The objective of this bulletin isto explore issues associated with the management of biogas
‘Production on dairy firms using cow manure 46 the digester feedstock.

Figure 3. Anserobic digester atthe Agway Fanm Research Cems in Onondaga County, NY.
3

FUNDAMENTALS OF AN ANAEROBIC DIGESTION SYSTEM

‘Anaerobic digestion is a biological process in which microbes “digest” the organic material in
‘manure while giving off biogus as a by-product (Figure 4). These microbes exist naturally i the
fnanute, 50 the digester's function is to provide suitable conditions for the microbes’ growth,
Digested manure has less xtor than undigested manure.

Figure 4, Anaerobic digestion system components:
‘manore handling; digester; and biogas wnlization.

‘Anaerobic digestion occurs in two phases (Figure $)-In phase one, acid-forming bacteria convert
‘Complex organic material such as proteins, fas, and carbohytdrates into organic acids—primerily
teetlc and Propionic acids. in phase two, these acids are converted by methane-forming bacteria
into biogas (methane and earbon donide).

fuwsr PHashi ) SECOND rHASF:
| caxnerew | |

oNRLEX SRCANIC “|
MATERIA. QCANURE)

saerur oxoastes |
eons a9

Figure 5. Two phases of methane production by anaerobic digestion,
4

‘he acid forming bacteria of phase one reproduce rapidly and are not sensitive to environmental
Conditions. However, the methane-forming becteria of phase two are xremely sensitive o
‘oxygen, temperature, acidity (pH), and the manure loading rate. To keep all of the microbes
healthy and producing biogas, these environmental factors must be controlled so that the acid
(onniers and methane formers are kept in balance.

‘For economically optimal biogas production, the digester contents must be hept at temperate of
00°F. Figure 6 shows how biogas production is influenced by temperatures both Maher and
lover than optimal. Maintenance of optimal digester temperature is the single most
important management factor for successful operation af a dairy digester system,

es
et

Digester Torperiure
Figure 6. Biogas production is optimized at about 100"F digester tempatature.

‘The numberof days that manure remains in the digester, calied the hydraulic teeation time (HRT),
affects biogas production in that gas production from a mass of manure is greater with hanger
retention times (Figure 7). Typical HRT is 20-30 days. For additional discussion of HRT. see
Anaerobic Digester Desig & Construction on page 17

s a —_—
ve a
Praditon
en faasiipe
ny

% 30 Days
Hyde Retention Tine

Figure 7. Hydraulic etention time influence on biogas production,