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Methane Gas Capture:Methane Gas Capture:two case studiestwo case studies
Ben TeagueBen Teague
Mississippi Technology Alliance/Mississippi Technology Alliance/
Mississippi Alternative Energy EnterpriseMississippi 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 reactor4. Anaerobic filter reactor5. Upflow solids reactor6. Continuously stirred tank reactor with solids recycle7. Upflow anaerobic sludge blanket reactor8. Anaerobic pump digester9. Fluidized- and expanded- bed reactors10. 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
Barn
. Manure Slurry Flash Mix
Water
Solids
Separator
Water
CSTR Digestor
Biogas
Plug Transport
Plug Flow Digester
Mixing tank PF Digestor
Biogas
Not 100% Necessary(Slurry in Digester)
PROS Low maintenanceBatch or semi-batch operationRapid recovery time/ low retention time neededCan be used effectively in multiple climates
CONS Comparatively expensive Smaller reactor volumeLabor intensive material handling issues
Barn
. Manure
Water
Solids
Separator
Covered Lagoon
Barn
. Manure
Water
Solids
Separator
Biogas
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
Typical Digester System DesignTypical Digester System Design
Barn
Screen Digestor
BiogasMilking Parlor or
other market
.Heaters
Biogas Storage
Gas Compressor
IC EngineElectricity Generation
Heat Recovery
Liquid
Solids
Separator
Digestor Heating (winter)
Compost
PotentialProtein
Recovery
Liquid Fertilizer
Cultured Growth
PlantBedding
LiquidsStorageTank/ Lagoon
To Grid
General Benefits of a Digester System
• 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 3-6% solids.
Dairy Methane Gas Capture System
• 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
Spray irrigation
Gensetmethane
Existing Lagoon Solids
Separator
Compost
Equalization Basin
Anaerobic Digestion
Barns
Electricity to operatesystem, excess to Grid
Clear Water
Offset purchased Propane
Recirculation for barn flushing
Dairy Activities to Date
• 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 SystemReview
• 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)
• 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
$0$1,500$3,000$4,500$6,000$7,500$9,000
$10,500$12,000$13,500$15,000
TotalSystemSavings
FarmerSavings
PrestageSavings
total
Farmer electricitySavings
Farmer GasSavings
Prestage Savings
($.85/ gal $.07 retail $.02 sell back) retail actual = .075 per kwh
(Total Savings $15,343)
IC EngineLiquid Fertilizer
Cultured Growth
Biogas for direct burn
Covered lagoon
Existing lagoon
Liquids pumped from lagoon
Genset
To the grid
Used on farm
barn biogas
M&N Swine System
Swine Schematic
Existing Lagoon
BARNS
Anaerobic Digester
Flaregenset
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 ?
