Draft


Combined Heat and Power 

Energy Savings and Energy Reliability for 

Wastewater Treatment Facilities 

For
detailed
information
on
the
opportunities
for
CHP
at
WWTFs,
see
the
CHP
Partnership’s
report,


The Opportunities for and Benefits of Combined Heat and Power at Wastewater Treatment Facilities.


1


1
Available
at
http://www.epa.gov/chp/markets/wastewater.html.


Combined
heat
and
power
(CHP),


also
known
as
cogeneration,
can
be


an
excellent
solution
for
controlling


energy
costs
while
improving
the


reliability
of
power
and
thermal
energy


supplies
for
your
wastewater
treatment


facility
(WWTF).
With
a
well­designed


CHP
system,
your
facility
can:


� Produce
power
at
a
cost
below
retail


electricity.


� Reduce
operating
costs
by
displacing


purchased
fuels
for
thermal
needs.


� Ensure
the
availability
of
reliable


heat
and
electricity
supply.


� Increase
energy
efficiency,
reduce


greenhouse
gas
emissions,
and


generate
renewable
power.


How Is CHP Used at 

WWTFs? 

CHP
is
the
production
of
both
power
and


heat
from
a
single
fuel
source.
CHP
is
a


reliable,
cost­effective
option
for
WWTFs


that
have,
or
are
planning
to
install,


anaerobic
digesters.
The
biogas
flow
from


the
digester
can
be
used
as
“free”
fuel
to


generate
electricity
and
power
in
a
CHP


system
using
a
turbine,
microturbine,
fuel


cell,
or
reciprocating
engine.
The
thermal


energy
produced
by
the
CHP
system
is


then
typically
used
to
meet
digester
heat


loads
and
for
space
heating.
By
making


use
of
the
waste
heat
from
onsite


electricity
production,
CHP
increases
fuel


efficiency
and
decreases
energy
costs.


Engineering Rules of 

Thumb for Considering 

CHP at a WWTF 

•
 A
typical
WWTF
processes
100
gallons


per
day
of
wastewater
for
every
person


served.


•
 Approximately
1.0
cubic
foot
(ft3)
of


digester
gas
can
be
produced
by
an


anaerobic
digester
per
person
per
day.


This
volume
of
gas
can
provide


approximately
2.2
watts
of
power


generation.


•
 The
heating
value
of
the
biogas


produced
by
anaerobic
digesters
is


approximately
600
British
thermal
units


per
cubic
foot
(Btu/ft3).


•
 For
each
4.5
million
gallons
per
day


processed
by
a
WWTF
with
anaerobic


digestion,
the
generated
biogas
can


produce
approximately
100
kilowatts


(kW)
of
electricity
and
12.5
million
Btu


(MMBtu)
of
thermal
energy.

Where Does CHP Have the Best 

Technical and Economic Fit? 

CHP
has
the
greatest
technical
and
economic


potential
at
WWTFs
that
have
anaerobic
digesters


and
influent
flow
rates
greater
than
5
million
gallons


per
day
(MGD).
Anaerobic
digestion
continuously


produces
biogas
that
contains
approximately
60


percent
methane.
The
biogas
generated
from
each
4.5


MGD
of
influent
flow
generates
approximately
100


kW
of
electricity
and
12.5
MMBtu
of
thermal
energy


in
a
CHP
system.
The
electricity
and
heat
can
be


used
for
a
variety
of
purposes:


� To
sell
back
to
the
grid
as
green
power.


� To
operate
pumps
and
blowers
used
throughout


the
treatment
process.


� To
maintain
optimal
digester
temperatures,
dry


the
biosolids,
and
provide
space
heating
for
the


WWTF.


A
variety
of
CHP
technologies
can
be
used
at


WWTFs.
Reciprocating
engines
are
the
most
widely


used
CHP
systems
and
can
be
employed
at
facilities


with
any
influent
flow
rate.
Microturbine
and
fuel
cell


CHP
systems
up
to
approximately
1
megawatt
(MW)


can
be
employed
at
facilities
with
influent
flow
rates


less
than
50
MGD.
Combustion
turbine
CHP
systems


greater
than
1
MW
are
an
option
for
facilities
with


influent
flow
rates
greater
than
50
MGD.


What Can CHP Do for You? 

Reduce Energy Costs 

A
well­designed
CHP
system
can
be
an
attractive


investment
for
your
WWTF.
A
CHP
system
allows


your
facility
to
generate
both
electric
and
thermal


energy
on
site,
offsetting
the
costs
of
grid
power
and


purchased
fuel.


A
market
analysis
developed
by
EPA’s
CHP


Partnership2
 estimates
the
net
cost
to
generate
power


for
three
representative
CHP
systems
at
a
WWTF.


Depending
on
the
WWTF,
costs
can
range
from:


� 3
cents
per
kilowatt­hour
(kWh)
to
6.5



cents/kWh
for
a
126
kW
microturbine.



� 9.1
cents/kWh
to
10.2
cents/kWh
for
a
300
kW


fuel
cell.


� 0.1
cents/kWh
to
3.8
cents/kWh
for
a
1
MW



reciprocating
engine.



Although
the
economics
of
CHP
at
WWTFs
are


often
attractive,
in
states
where
electricity
prices
are


low,
burning
biogas
directly
in
boilers
for
onsite


heating
needs
might
be
more
economical.


Ensure the Availability of Heat and Electricity 

Supply 

CHP
systems
provide
critical
power
and
thermal


reliability
for
WWTFs
by
producing
power
and
heat


24
hours
per
day,
7
days
per
week.
CHP
integrates


seamlessly
into
existing
heating
and
electrical
systems


and
provides
a
steady
supply
of
hot
water
or
steam.
A


CHP
system
can
also
be
configured
to
provide
backup


power
in
the
event
of
a
utility
outage
so
operations


can
continue
during
a
blackout
or
catastrophic
event.


Grid 

Heat Recovery 

Unit 

Engine 

Turbine 

Microturbine 

Fuel Cell 

Generator 

Electricity 

Water 

Steam or Hot Water Digester Heating/ 

Space Heating 

WWTF 

Anaerobic 

Digester 

Biogas 

Hot Exhaust 

Gases 

Typical CHP System Configuration at WWTFs 

2
 available
at
http://www.epa.gov/chp/markets/wastewater.html
Increase Energy Efficiency, Reduce Greenhouse 

Gas Emissions, and Generate Renewable Power 

With
CHP,
improved
efficiency
means
that
your


facility
uses
less
fuel;
therefore,
operating
and


maintenance
costs
are
reduced,
while
environmental


performance
is
improved.
The
power
and
heat


produced
on
site
by
the
CHP
system
displaces


purchases
of
electricity
and
fuel
for
boilers.
The
same


reductions
in
purchased
electricity
that
result
in


energy
cost
savings
also
reduce
the
environmental


impact
of
WWTF
operations
by
reducing
air


pollution.


On
a
national
scale,
if
all
WWTFs
that
operate


anaerobic
digesters
and
have
influent
flow
rates


greater
than
5
MGD
were
to
install
CHP,


approximately
340
MW
of
clean
electricity
could
be


generated,
offsetting
2.3
million
metric
tons
of


carbon
dioxide
(CO2)
emissions
annually.
These


emission
reductions
are
equivalent
to
removing


approximately
430,000
cars
from
the
road.


Additionally,
because
the
biogas
produced
by


WWTFs
is
considered
renewable
by
most
state


renewable
portfolio
standards
and
third­party
green


power
certification
programs,
the
environmental


attributes
of
electricity
generated
by
CHP
systems
at


WWTFs
can
be
sold
as
renewable
energy
certificates


(RECs).
The
monetary
value
of
the
REC
sale
may
be


used
to
defray
the
capital
costs
of
the
CHP
system
to


further
improve
project
economics.


How Is CHP Being Used at U.S. WWTFs? 

As
of
September
2007,
wastewater
treatment
CHP
systems
were
in
place
at
79
sites
in
24
states,
representing


223
MW
of
electric
capacity.
Of
the
existing
CHP
systems
in
the
wastewater
treatment
sector,
the
majority
use


reciprocating
engines.
The
mix
of
technologies
used
for
CHP
also
includes
microturbines,
fuel
cells,
and
turbine


installations.


The
following
case
studies
provide
examples
of
recent
successful
CHP
installations
at
WWTFs.


City of Albert Lea Wastewater Treatment Palmdale Water Reclamation Plant, 

Facility, Minnesota California 

In
the
summer
of
2003,
the
city
of
Albert
Lea,
Minnesota,
 In
2004,
the
Los
Angeles
County
Sanitation
District


installed
a
120
kW
CHP
system
at
its
WWTF.
The
CHP
 (LACSD)
began
operating
a
250
kW
fuel
cell
CHP


system
integrates
four
30
kW
microturbines
(manufactured
 system
at
the
Palmdale
Water
Reclamation
Plant.
The


by
Capstone
Turbine
Corporation,
a
CHP
Partnership
 fuel
cell
was
manufactured
by
FuelCell
Energy,
a
CHP


Partner)
and
utilizes
the
recovered
heat
(28
MMBtu
per
 Partnership
Partner.
With
the
CHP
system,
70
to
80


day)
from
the
turbines
to
maintain
proper
operating
 percent
of
the
digester
gas
produced
by
the
facility’s


temperature
of
the
anaerobic
digester
and
provide
a
 anaerobic
digesters
is
utilized
in
the
fuel
cell.
The


portion
of
the
facility’s
space
heating
requirements.
 system
produces
225
kW
for
use
on
site,
while
waste


heat
from
the
fuel
cell
exhaust
is
used
to
maintain
 With
funding
from
the
Minnesota
Department
of
 proper
temperature
for
digester
operation. Commerce’s
Conservation
Improvement
Program
and
the


local
utility,
the
CHP
system
provides
120
kW
of
backup
 LACSD
chose
the
use
of
biogas
coupled
with
CHP
to


power
to
operate
critical
systems
during
a
utility
power
 conserve
fossil
fuel,
reduce
air
emissions,
and
save


outage.
The
CHP
system
also
saves
the
WWTF
800,000
 money.
The
CHP
system
reduces
annual
CO2
and


kWh/year,
or
25
percent
of
its
energy
use.
The
system
has
 nitrogen
oxide
emissions
by
778
tons
and
0.58
tons,


a
payback
period
of
approximately
4
to
6
years.
 respectively,
and
saves
LACSD
approximately


$227,000
per
year
in
energy
costs.
 In
addition
to
representing
a
successful
partnership


between
municipal,
utility,
and
state
entities,
the


project
successfully
integrates
a
CHP
system
utilizing


a
renewable
fuel,
generates
energy
and
cost
savings


for
the
municipality,
and
results
in
reduced
air


emissions
for
local
citizens.

What Resources Are Available? 

Technical Assistance 

The
CHP
Partnership
has
developed
services
and


tools
to
assist
those
considering
implementing
CHP


at
their
facilities.
Visit
the
Streamlining
Project


Development
pages
of
the
Partnership’s
Web
site
at


www.epa.gov/chp/project-development/index.html to


learn
more
about
the
CHP
project
development


process,
whom
to
involve
on
your
CHP
project


team,
typical
options
for
system
financing,
and
other


services
EPA
provides.


Project Resources 

Take
advantage
of
the
Partnership’s
up­to­date
lists


of
state
and
federal
incentives
(e.g.,
rebates,
tax


credits,
environmental
revenue
streams)
for
CHP,


along
with
lists
of
regulatory
rules
and
rates
that
are


advantageous
to
clean
distributed
generation.
This


information
is
updated
monthly
at
www.epa.gov/

chp/funding/index.html.


Public Recognition 

Through
the
ENERGY
STAR
CHP
Awards,
EPA


recognizes
highly
efficient
CHP
projects
that
achieve


fuel
and
emission
savings
over
comparable
state­ofthe­art
separate
heat
and
power.
The
Partnership


accepts
Award
applications
continuously
and


presents
these
awards
at
key
events.
For
more


information
on
applying
for
an
ENERGY
STAR


CHP
Award
for
your
WWTF,
visit
www.epa.gov/

chp/public-recognition/index.html.


Is My Facility a Good Candidate

for CHP? 

•
 Do
you
have
an
influent
flow
rate
greater
than
5


MGD?


•
 Do
you
pay
more
than
$0.06/kWh
for
electricity?


•
 Is
reliable,
high-quality
power
and
thermal


energy
important
to
you?


•
 Is
it
important
to
reduce
energy
costs
and


increase
the
overall
energy
efficiency
of
your


wastewater
treatment
process?


•
 Do
you
want
to
increase
your
facility’s



environmental
performance?



If
the
answer
is
“yes”
to
two
or
more
of
these



questions,
CHP
can
benefit
your
facility.



CHP
technologies
are
flexible,
providing
a
wide


range
of
sizing
options.
The
right
CHP
system
for


your
WWTF
will
be
determined
through


consultations
and
analyses,
which
will
include
a


site-specific
evaluation
of
your
facility’s
electricity


and
thermal
loads.


What’s the Next Step? 

EPA
is
available
to
answer
your
questions
and


provide
specific
technical
support
for
your
project.


For
information
on
how
EPA
can
support
your


evaluation
and
implementation
of
CHP,
contact


Neeharika Naik-Dhungel at (202) 343-9553 or 

e-mail her at naik-dhungel.neeharika@epa.gov.

About the EPA CHP Partnership 

The
CHP
Partnership
is
a
voluntary
program


designed
to
foster
cost-effective
CHP
projects.


Through
the
Partnership,
EPA
engages
energy


users,
the
CHP
industry,
state
and
local


governments,
and
other
stakeholders
in
cooperative
relationships
to


expand
the
use
of
CHP.
Information
about
the
Partnership’s
services
and


program
offerings
is
available
on
its
Web
site:
www.epa.gov/chp.


Last
updated
March
5,
2008