Optimizing the Digestion Process to Maximize
Methane, Power and Payback – A Discussion of
Treatment, Co-Generation and the Evolving
Methods of Paying Off the System
Joseph C. Cleary, P.E., BCEE
Principal
HydroQual, Inc.
1200 MacArthur Boulevard, Mahwah, NJ 07430
jcleary@hydroqual.com
Michael Curtis, Ph.D., P.E.
Senior Vice President
Fuss & O’Neill
146 Hartford Road, Manchester, CT 06040
mcurtis@fando.com
Outline








Anaerobic Digestion Overview and History
Available Technologies and Configurations
Design Considerations & Optimization
Project Delivery Approach
Paying for Alternative Energy Upgrade
Renewable Energy, Carbon Credits and Bonds
Entrepreneurial Approach and Investor Partnering
Summary
Anaerobic Digestion Overview
and History
Anaerobic Digestion Process
History






1940’s – Low rate anaerobic municipal sludge
digesters
1950-60’s – Two stage and heated digesters 7
Thermophilic
1960-70’s – Anaerobic contact process used in
meat packing and food industry wastewater.
1965-85 – Development of Egg-Shaped Digesters
for municipal sludges
1966-68 – Fixed film reactor lab studies
1972 – First full-scale anaerobic filter with pall
rings (Celanese)
History

1980-85 – Hybrid anaerobic filter (ADI)
Downflow filter (Bacardi)
Upflow anaerobic sludge blanket (UASB)
(Biothane & Paques)
Fluidized Bed



1990s – Expanded Granular Sludge Bed (EGSB)
(Biothane)
1990s-2000 – Pulsed sand bed system (Ecovation)
2000-Present - Co-Gen Advancements, “Carbon
Engineering” TM
Number of Industrial Installations
Industrial Sector
Beverage
Food
Pulp and paper
Chemical/pharmaceutical
Dairy/Ice Cream/cheese
Sewage
Meat/poultry/fish
Other
TOTAL
Reference: Chemical Engineering April 2003
Number
623
310
137
107
67
67
23
265
1599
Typical Industrial Application
Reactor Configurations
Reference: R.E. Speece, 1996
Design Considerations

Organic loading rate (e.g. Kg COD/M3-day)

Gas production rate

Alkalinity & pH balance

Reactor configuration / mixing

Concentration of biomass inventory

Volatile Solids / Mass Reduction

Temperature / Heating

Toxicity Inhibition

Biosolids Quality – Pathogen Destruction
Digester Process Optimization

Improved Mixing

New Low-Energy Mixing Enhancements

Increase Methane Production / VS Reduction

Staged Reactors

Temperature (meso / thermophilic)

pH / Alkalinity

Feed Rate Optimization

Co-Digestion – Carbon Engineering TM
Project Delivery Approaches

Design/Bid/Build (most traditional)

Design/Build (D/B)

Design/Build/Operate/Maintain (DBOM)

Design/Build/Own/Operate/Maintain
(DBOOM)
 So
How do You Pay for it ??
Paying for Alternate Energy Upgrade






Resource is Methane
Payback Based Upon Avoided Power Purchase
and Much More
1 mgd plant with Flared, well-maintained
digester
20,000 SCFD – 60% Methane – 30 kW
$45K per year at $0.16 per kWhour
Helps – but will not pay for $ 0.5 – 1M
investment
Paying for Alternate Energy Upgrade

Must Install
Gas Treatment – Sulfur and Siloxanes
Condensate Collection

Pressurization

Co-Generation Unit (turbine, engine, etc.)
Electric Switch Gear
Heat Exchange Capabilities (Exhaust / Engine Jacket
Heat to Process)




Not Rocket Science – but Not Trivial!
Co-Gen Units
Fuel Cell – 7K per kW
80-90% Efficient
Power and Heat
Micro Turbine
4 K per kW
Paying for Alternate Energy Upgrade




First Consideration – app. / up to 50 % Sludge
Mass Reduction – sizable Sludge Disposal
Cost Reduction
Possible Elimination of some / all Fossil Fuel
Use to Maintain Digester Temperature
Avoided Power Purchase – Power Parasitized
On-Site - Highest Value
Low Energy Plants (RBC’s, Trickling Filters)
can actually export Power to Grid - Net
Metering Research
Renewable Energy Credits and Carbon
Credits






Renewable Energy Credits (REC’s) for
generated power
Current value approx 3-7 cents per kWh
Based Upon Utility Mandates to Offer
Increasing levels of Renewable Power
Capitalism at Work – Given Market
Brokers – Buyers - Sellers
Value of Power ($0.05 per kWh)


$0.21 per kWH
$55K for 30 kW Installation
Renewable Energy Credits and Carbon
Credits

Carbon Credits market still very young

Adds some revenue now

Has Potential to add very significant
revenue stream for larger projects
 Example – Mid-Size Digester
 Offsetting 500,000 gal fuel oil per year
 Reducing 5,000 tons/year CO2
 Ten year period
 Total value approx $500,000
Renewable Energy Credits and Carbon
Credits

Purchase of Carbon Credits and REC’s

Lump Sum Up front – Buy Down Capital

Long-Term Annuity Approach

Need Good Financial Analyst

Long-Term - Carbon Costs Going to Rise
New Jersey Programs

http://www.njcleanenergy.com/renewableenergy/programs/renewable-energyincentive-program

New Jersey Clean Energy Program

Large and Growing

Never Take ANYTHING on Face Value

Programs Set up for Flexibility and Success

NJ BPU BioPower Rebate Program

$1,500 - $2,000 per kW at Typical Installation
Clean Renewable Energy Bonds

The Energy Policy Act of 2005 (P.L. 109-58)
establishes Clean Renewable Energy Bonds. A
"CREB" is a special type of tax credit bond
providing the equivalent of an interest-free
loan for financing qualified energy projects.
Clean Renewable Energy Bonds



For the 2007 round of awards, there were 786
applicants from 40 states seeking a total of $2.5 billion
in bond authorization (three times what was available).
610 projects were approved including 78 private
projects in 24 states ranged from $120,000 to $31
million.
25% of the applicants were in California (presumably
high solar pv project count); other active states were
New Mexico, Montana, Minnesota and Colorado. There
were few applicants from the East and South other than
Massachusetts.
Entrepreneurial Approach




Well run Digester an Environmental Bonanza
Can Take Organic Wastes and Treat for Money
CA – Food Wastes
New England –





Flammable Hazardous
Petroleum / Waste Wastes
Food and More
Pluses – Tipping Fees – Can Greatly Increase
Methane Production Power Payback
Essex Junction VT
Investor Partnering





Digester Projects are Wanted Commodities by
the Investment Community
Shared-Savings – Open Book Approach
ESCO’s
Value of Carbon seen as ‘sure thing’
Private – Public Partnership can make project
happen
Summary






Trend towards Increased Sludge Digestion in US
and World
Reverses Trends (EPA) of Previous 25 years
Alternate Energy Market – Driven
If you Have Methane – Easy Analysis to Develop
If you are Planning Stages, my belief is that
Switch to Digestion Will and Can Pay
Expert-Driven Field Integrating Design,
Construction and Financing
QUESTIONS