digestion: managing blended wastes blended wastes... · 2015-02-05 · blended wastes municipal...
TRANSCRIPT
DIGESTION: MANAGING
BLENDED WASTES
ROBERT CASE – CITY OF FLINT
WATER POLLUTION CONTROL SUPERVISOR
CHAD ANTLE – BIOWORKS ENERGY
CHIEF EXECUTIVE OFFICER
CITY OF FLINT
WATER POLLUTION CONTROL, 2008
Flint’s Solids Handling, 2008
PUBLIC – PRIVATE PARTNERSHIP
2008
Began with Governor’s Trade Mission
Center of Energy Excellence with Kettering University
Energy Production – Major Goal
MEDC Grant + SBI Funding = Capital Improvements
Processing Cost Savings Provides Operating Revenue
CITY’S GOALS AND OBJECTIVES
Reduce operating
costs
Minimize capital
expenditures
Maintain or
enhance reliability
of solids
processing
Promote
sustainable
operations
SWEDISH BIOGAS INTERNATIONAL
GOALS AND OBJECTIVES
Implement Digestion Process
Produce Energy - Biogas
Business Expansion, Revenue Increase
Rehabilitation of Flint’s Solids Facilities
FLINT BIOGAS PLANT - PHASE I
Ground
breaking08/09/2010
Seed sludge
loading05/16/2011
• Production
startup
• Cost
savings
begins
08/2011
Thru
09/2011
Ex. North Digester
Existing
Biosolids
Incinerator
Biogas
Digestate
Storage
Sludge
from
Treatment
Plant
Digested
Biosolids to
Incinerator
Gas
Holder
Digestate
StorageTo Boiler
ACCOMPLISHMENTS
2011
REFURBISHED NORTH DIGESTER
• NEW MIXING SYSTEM
• NEW HEATING SYSTEM
• NEW CONTROL SYSTEM
REPLACED GAS SPHERE WITH NEW
DIGESTATE STORAGE TANK
NEW PUMP HOUSE
NEW SLUDGE FORCE MAINS
NEW CENTRIFUGES
SBI revenue depends on cost
savings
Cost savings declined
•Lower sludge volume
•Reduced natural gas cost
Value of Biogas
City forced
to
abandon incineration
Unexpected
Changes
THE NEW ORDER
SBI exits North
Americaoperations
BioWorksEnergy
acquires N. America operations
BioWorks
negotiates
new contract
with Flint
Stable and Sustainable Revenue Base
Long Term Commitment to Partnership
I
• Landfilling to replace incineration
• Use biogas to generate lower electricity costs
II
• Enhance biogas production – pursue outside wastes
• Blend high energy outside wastes with dilute municipal sludge
III
• Digest the blended wastes
• Produce electricity with internal combustion engine generator
STEP BY STEP: The New Order
ADVANTAGES
Greatly
increased
gas
production
Increased
revenue
Tipping
fees
Diversion
of high
strength
wastes
Improved
utilization
of assets
Flint Solids Handling, 2015
Municipal Biosolids
High Strength Wastes
2015 GOALS INCREASE VOLUME
OF EXTERNAL
SUBSTRATES
INSTALL
ELECTRICAL POWER
GENERATION
CONSTRUCT
BIOSOLIDS
LOADING FACILITY
DECOMMISSION
INCINERATION
BLENDED WASTES
MUNICIPAL WWTP SLUDGE
(PRIMARY, WAS, TWAS)
1 to 8% total solids
60 to 90 % Volatile Solids
55 to 65% Methane Content
Heterogeneous MIX – Good for Digestion
Relatively Low “Energy Density”
Contains both MACRO/Micro Nutrients required for
stable process
EXTERNAL SUBSTRATES
(FOOD PROCESSING WASTES, ORGANIC PROCESS, ETC)
TS% - Large Variations, Rheology Not Directly
Related to TS%
30 to 100% Volatile Solids
45 to 75% Methane Content
Homogeneous Mix – Can Be Difficult to Digest as a
Mono-Culture
Higher Energy Densities Than WWTP Sludge
May Lack Macro/Micro Nutrients
Proper Combination of the Two - Better Than Either Component
Increased gas
production
Micro-
Biological
diversity
Potentially higher
degradation of solids
Increased
revenue
(Tip fees,
power
generation)
BENEFITS
OF
BLENDED
WASTES
How do I
put it
together?
REALLY…
Is this
necessary?
ADMINISTRATIVE CONCERNS
Substrate
Variability
• Unknown
factors
• Unwanted
effects
• NPDES
compliance
• Polymer
consumption
Delivery
• Acceptable
transfers
• Limited
delivery
window
• Labor
resources
Sustainability
• Must achieve
desired results
• Reliable Staff
• Who is the
“Cavalier”?
PROCESS CONCERNS
SUBSTRATE VARIABILITY
The Unknown and Sometimes Unwanted Impacts
IMPACTS
Thickening and
dewatering
performance may
vary
RESPONSIBLITY
Owner must insure
compatibility with
digestion system
and NPDES limits
TESTING
Substrates should
be tested prior to
system injection,
before problems
arise
SUBSTRATE
PROVIDER
Not responsible for
the WWTP.
Responsible only to
get rid of their
waste reliably.
QUANTIFY
Recycle Streams
and nutrient Loads
should be projected,
with testing and
modeling
GAS QUANTITY/QUALITY CONCERNS
• Flow Rates
• Pressure/Vacuum Relief Valves
• Flare
• Gas storage
• Water separation
GAS HANDLING
SYSTEM
DESIGN
• Changes in energy content
• Increases in Hydrogen Sulfide
• Dilution of siloxanes (mg/M3)
• Higher chemical (Carbon/F3Cl
2) costs
BIOGAS
QUALITY
STEADY SUBSTRATE SUPPLY
• Not always as advertised!
• Marketing and procurement of long term contracts
• Competitive pricing
• Economic Development – Educate
planners/administrators of the benefit potential
MANAGEMENT
• Sufficient daily supply
• Long term contracts – Hard to come by
• Tip Fees are Volatile – competition for substrates
• Educating administrators regarding the entire process
CHALLENGES
• Must be “Right-Size” for efficient processing
• Under utilization of capital improvements if substrates
don’t materialize
• Laboratory QA/QC of Substrates – Insure material is as
planned
RISKS
PRACTICAL ISSUES OF
BLENDED WASTES
Proportions of the desired mix and how to achieve it
Order of addition (Municipal sludge versus
substrates)
Higher gas production than expected
Rapid Rise – Underestimated gas production +
insufficient Mixing = rapid expansion in gas/liquid
matrix
Flaring of gas instead of power generation = lost
revenue
ECONOMICS OF BLENDED WASTES
Tip Fees
Additional Energy
Production
• Power production
• Avoidance of natural gas usage
• Renewable energy credits
Added nutrient value for land app
Higher energy
consumption through
higher mixing requirements
+/- Impacts to residuals
processing
Recycle streams –impacts to
plant
Increased employee
labor
QUESTIONS?