Transcript Methane Gas Capture: two case studies

Methane Gas Capture:
two case studies
Ben Teague
Mississippi Technology Alliance/
Mississippi Alternative Energy Enterprise
Methane Gas Capture
General Overview
The Anaerobic Process to Make Biogas
• In the absence of oxygen naturally occurring bacteria will
break down manure
• The break down and conversion to methane occurs in
four basic steps.
–
–
–
–
Hydrolysis
Acidogenesis
Acetogenesis
Methanogenesis
• The final stage methanogensis is the actual break down
of the immediate compounds to methane
• Biogas is usually composed of 55-75 percent methane.
Carbon Dioxide and Hydrogen Sulfide make up the bulk
of the remainder.
Types of Anaerobic Digesters
Three Main Types of
Digester Design Options
1. Complete Mix (CSTR) – fully homogeneous
contents
2. Plug Flow – mimics a series of laterally mixed
units
3. Lagoon – energy recovery from treatment
oriented design
Other Digester Types
1.
Batch- fed reactor, such as the anaerobic sequential
batch reactor (ASBR)
2. Temperature- phased anaerobic digester (TPAD)
3. Suspended particle reactor
4. Anaerobic filter reactor
5. Upflow solids reactor
6. Continuously stirred tank reactor with solids recycle
7. Upflow anaerobic sludge blanket reactor
8. Anaerobic pump digester
9. Fluidized- and expanded- bed reactors
10. Fixed film anaerobic digester
AgSTAR August 2002 Haubenschild Farms Anaerobic Digester Final Report
Complete Mix Digester
 Contents kept mixed or periodically mixed
 Batch or semi-batch operation
 Mixing accomplished using mixer or pump
 High rate and extent of biogas production
 Complex solids handling
 Comparatively expensive
 Common with smaller systems
 Lower L/S ratios (more water [+ & -])
 High level of mechanical wear
Biogas
Water
Water
.
Barn
Solids
Manure
Slurry Flash Mix CSTR Digestor
Separator
Plug Flow Digester
Plug Transport
PROS
Low maintenance
Batch or semi-batch operation
Rapid recovery time/ low retention
time needed
Can be used effectively in
multiple climates
CONS
Comparatively expensive
 Smaller reactor volume
Labor intensive material
handling issues
Not 100% Necessary
(Slurry in Digester)
Biogas
Water
.
Barn
Solids
Manure
Mixing tank
PF Digestor
Separator
Covered Lagoon
PROS
•Least Expensive
•Low Maintenance
•Material handling
•Can handle low solids manure
CONS
•Land availability
•Efficient only in high temp climates
•High retention time needed b/c of low
low efficiency and liquid amounts
Biogas
Water
.
Solids
Barn
Manure
Separator
Typical Digester System Design
To Grid
Biogas Storage
Gas Compressor
.
Milking Parlor or
other market
Heaters
Potential
Protein
Recovery
Heat Recovery
Biogas
IC Engine
Electricity Generation
Barn
Digestor Heating (winter)
Screen
Digestor
Plant
Bedding
Liquid Fertilizer
Liquids
Storage
Tank/
Lagoon
Cultured Growth
Liquid
Solids
Separator
Compost
General Benefits of a Digester System
•
•
•
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Odor Control
Cash savings
Reduced risk of being subject to legal action
Renewable Energy Production
– Heat
– Electricity
• Pathogen Reduction
• Greenhouse gas reduction
• Reduction in TOD (Total Oxygen Demand)
Two Case Studies
Swine and Dairy
Two Sites in Mississippi
• The Land Water Timber Resource Board
has funded Mississippi Alterative Energy
Enterprise (MAEE) to construct two
Methane gas capture systems.
• Swine system located in Montpelier, MS
• Dairy system located in Forest, MS
Dairy System
• Dairy manure characteristics matches well with a
plug flow manure.
– Due to the high solid content dairy manure can easily
be scraped versus flushed
– A scraping system adds no or very little water into the
system. Thus a plug flow system is common.
• However, this system at Forest is a hybrid
system. It utilizes a high pressure low volume
flushing system.
• The manure will enter the digester at about 36% solids.
Dairy Methane Gas Capture
System
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Location: Mills Dairy in Forest, MS
Farmer: Quentin Mills
Total Project Cost ~$750,000-$800,000
Digester system cost: ~$282,000
Gas Use: Heating and Electricity
– Heating – direct use
– Electricity- through methane capable genset
• Estimated Annual Power Savings
– Farmer: $25,000
• Construction is due to be completed by April 22, 2004.
(Earth Day) A tour will be scheduled in the afternoon.
Why Here? Why Now?
• Mills Dairy (a 400 head dairy)
– Within the range of successful digester farms
– Accurate representation of an average to high
number Mississippi Farm.
• Farm Bureau pointed us toward the Mills Dairy
because they were transitioning from pasture to
a confined operation
• This transition time was a perfect penetration
point due to capital expenditures, construction
economies of scale and need for manure
management changes. (lagoon would not be
large enough)
Dairy System Schematic
Offset purchased Propane
methane
Electricity to operate
system, excess to
Grid
Genset
Barns
Spray irrigation
Anaerobic
Digestion
Equalization
Basin
Solids
Separator
Compost
Recirculation for barn flushing
Existing
Lagoon
Clear Water
Dairy Activities to Date
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Educated the farmer on Technology
Finalized working agreement issues
Refined planning assumptions
Executed project contract
Visited Florida Dairies & UF AD facility
Defined communications/reporting requirements
Concept design Dairy (design/waste treatment
plant layout)
• Identified permit issues
• Preliminary engineering & permit package
• Site Preparation
Dairy Activities to Date Cont…
• Submit permit package
• Finalize design documents (09-11-03)
• Finalize equipment/contractors
agreements
• Receive permit (90 days)
• Pour barn concrete (meeting 09-11-03)
• Procure equipment & materials
• Begin construction
Swine Methane Gas Capture System
Review
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Location: M&N Nursery in Montpelier, MS
Farmer: Mike Shinn
LWTRB Grant: $114,000
Prestage has donated $20,000
Gas Use: Heating and Electricity
– Heating – direct use
– Electricity- through methane capable genset
•
Estimated Annual Savings
– Farmer: $11,587
– Prestage:$3,755 (see next slide)
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8 barns = ~ 6,500 hogs at an average weight of 38 pounds per hog. (grown
from 12-50lbs)
M&N is paying ~ 7.5 cents per kwh for power and consuming ~ 88,685 kwh
per year. In 2000 M&N paid $6,659
Because M&N is a Prestage grower they have a capped cost of 45 cent per
gallon of propane. However the total propane cost in 2000 was $16,614
Swine System Savings
System Savings
$15,000
$13,500
$12,000
$10,500
$9,000
$7,500
$6,000
$4,500
$3,000
$1,500
$0
total
(Total Savings $15,343)
Farmer electricity
Savings
Farmer Gas
Savings
Total
System
Savings
Farmer
Savings
Prestage
Savings
Prestage Savings
($.85/ gal $.07 retail $.02 sell back) retail actual = .075 per kwh
M&N Swine System
Existing lagoon
Biogas for direct burn
barn
Covered lagoon
biogas
Genset
Used on farm
IC Engine
Liquid Fertilizer
To the grid
Cultured Growth
Liquids pumped from lagoon
Swine Schematic
BARNS
Existing Lagoon
genset
Flare
Anaerobic
Digester
Swine System
• Technology- This system utilizes a covered lagoon
approach
• Markets for Biogas- The biogas will fill all heating needs
and will then flow over to a generator to supplement or
replace power needs.
• Construction- Construction should be complete by
April 22,2004
• Paybacks was based on Propane cost offset and on gas
production. However, assuming average production and
$1.00 per gallon of propane cost the system should be
able to pay itself back within 5-6 years simple payback
Swine Activities to Date
• Many necessary “back office” issues have been
completed. These activities pave the way for
construction activities
• Meeting with DEQ to determine possible permitting
• Construction contracts in draft form
• Feasibility study performed earlier by Phil Badger
• Detailed financial models produced
• Investment secured from Prestage Farms. (09-12-03)
Swine Activities to Date cont…
• Soil samples have been taken for digester site to
determine necessity for clay lining and amount
of clay needed
• Educated participating farmer on the system
• Complete working agreement and contracts
• Identify planning assumption
• Engineering blueprints
• Finalize equipment/ contractors agreements
• Procure all equipment and materials
• Site Preparation
Key Closing Thoughts
• Economics or regulatory demands will drive the
proliferation of these systems in the Southeast.
• Types of manure match well with certain
technologies at this point; however, the lines are
being blurred by new technologies.
• A predetermined market for power or biogas
product is key to the economic viability
• Relationship with the Local Power Provider is
key
Questions ?