Optimum usage and economic Optimum usage and economic feasibility of animal manure-based feasibility of animal manure-based biomass in combustion systemsbiomass in combustion systems

Nicholas T. Carlinncarlin50@hotmail.com

Under the advisement of:Dr. K. Annamalai & Dr. W. Harman

Texas A&M University, Dept. of Mechanical EngineeringMarch 9, 2009

Overview

• Biomass supply and properties• Option 1: Large scale combustion of

biomass– Co-firing coal with biomass– Reburning coal with biomass

• Option 2: Small scale combustion of biomass

• Summary• Acknowledgments

Introduction – CAFOswww.factoryfarm.org

• About 10 million beef cattle on feed in USA• 5 dry kg (11 lb) manure per animal per day (collectable)• Over 18 million dry metric tons of manure per year• 109 million GJ/yr (103 million MMBtu/yr), if 70% ash

Sources:NASS of the USDAASAE standard D384.2 MAR2005

Dairy Cowswww.tnr.com (The New Republic)

• About 9.1 million dairy cows in USA• 6.4 dry kg (14 lb) manure per animal per day (collectable)• Over 21.2 million dry metric tons of manure per year• 255 million GJ/yr (242 million MMBtu/yr), if biomass is 40% ash

Sources:NASS of the USDAASAE standard D384.2 MAR2005

(by mass)

WY Sub-

bituminousa TX Lignitea

Low-ash Dairy

Biomassb

High-ash Feedlot

Biomassb

%Moisture, wet basis 32.9 38.3 25.3c 27.3c

% Ash, dry basis 8.4 18.6 20.0 45.2%Fixed Carbon, dry basis 49.2 41.2 17.4 10.0%Volatile Matter, dry basis 42.5 40.2 62.8 44.7%Carbon, DAF basis 75.7 74.1 58.9 59.1%Hydrogen, DAF basis 4.4 4.2 5.2 7.0%Nitrogen, DAF basis 1.1 1.4 3.2 4.2%Oxygen, DAF basis 18.4 19.1 32.0 28.9%Sulfur, DAF basis 0.4 1.2 0.7 0.8Empirical Formula C3.88H2.68N0.05O0.71S0.008 C3.10H2.09N0.05O0.60S0.019 C2.93H3.08N0.14O1.20S0.013 C1.96H2.76N0.12O0.72S0.010

Normalized Formula CH0.691N0.013O0.183S0.002 CH0.674N0.016O0.194S0.006 CH1.051N0.048O0.410S0.004 CH1.408N0.061O0.367S0.005

HHV, dry basis (kJ/kg) 27,115 23,160 17,183 11,266HHV, dry basis (Btu/lb) 11,658 9,958 7,388 4,844aTAMU Coal & Biomass Lab Fuel BankbSweeten and Heflin, 2006, TAMU Res. & Ext. Center, AmarillocSolar dried before the fuel analysis, typically about 88% moisture as excreted

Fuel Analyses

0

200

400

600

800

1,000

1,200

1,400

0 10 20 30 40 50 60 70 80 90 100

Moisture Percentage, wet basis (%)

Man

ure

Bu

lk D

ensi

ty (

kg/m

3 )

Chen, 1983, for Beef cattle manure with %M > 84%

ρ b,MBB = 998*(1 - 0.00345(100 - %M ))-1

Bulk Density of Manure Biomass

Data from Chen, 1983, Ag. Wastes 6

Curve fit to Chen’s data

2

, 3

3 4

5 6

564.8745 4.373987 % 1.844560 %

1.293383E 1 % 2.800288E 3 %

2.525236E 5 % 8.252736E 8 %

b MBB

kgM M

m

M M

M M

Modeling Particle Distribution and Specific Heat

Porosity:

Specific heat of bone dry biomass solids, adapted from Bohnhoff et al., 1987.

,

% % %

100 100 100BD BD BD

MBB BD ash FC VM

A FC VMc c c c

Specific heat of wet biomass solids

2 ( ),

% %1

100 100 lMBB MBB BD H O

M Mc c c

2 ( )

,,

1 % 100% 1001

l

MBB b MBBH O p MBB

MM

Thermal Energy Conversion of Manure

OPTION 1: Large-scale combustion

OPTION 2: Small-scale, on-the-farm combustion

Power Plant

DryingGrinding and other

processing

Emission and dollar savings (or costs)? Overall economic feasibility?

Waste disposal plus co-benefit of usable energy or thermal

commodities

Design considerations. Gross economic study.

Option 1Large Scale Combustion

Dairy

Dairy

Large feedlot or CAFO

Power Plant

Centralized drying and composting facility

<30 km(<20 miles)

80-320 km(50-200 miles)

Transporting Manure Biomass

Biomass Drying Operations

boilerNatural Gas or Electric

Warm Air

Air

Steam

Capital Costs:•Dryer = f (belt area)•Boilers•Manure Loaders•Land Purchases

O&M Costs:•Dryer•Boilers•Loaders•Gas and/or electric•Labor

Transporting Biomass

• Known Parameters:– Loading and unloading

time– Average speed of the

trucks– Hauling schedule – hours

per day hauling– Number of days per year

hauling– Volume capacity of each

truck• Must find:

– # of trips, # of trucks– Total driving hours (labor)– Diesel fuel consumption

40 cubic yard trailer (www.montonetrailers.com)

Existing coal injection

Biomass stockpile

Transport or hauling vehicle

Front end loader

Metal detector Magnetic

separator

Scale

Screen

Feeder

Grinder

Air intake

Exhaust

Sep

arat

or

Silo

Vent

Scale

Feeder

Pressure blower

Biomass reburn fuel

Biomass co-fired

fuel

•Lower NOx

•Lower nonrenewable CO2

•Better oxidation of Hg

Higher Ash Output

Overall cost estimates for these operations for

reburn and co-fire systems exist in the

literature

Other Processing at Power Plant

[adapted from the DOE, 2004, Fed. Energy Management Program]

CombustionSystemCoal and/or manure

biomass• With a moisture

percentage, %M,• Ash percentage, %A, and• Temperature, Tfuel

Combustion Air• At some excess percentage,

%EA, of stoichiometric level,• At some temperature Tair, and • Some relative humidity

CVref

Qloss

Products of Combustion• At some temperature, Tout

General Combustion Model

22 (l) 2 2 , 2 (g)

2 2 (g) 2 2 2

79 79C H N O S H O Ash O N 1 H O

21 21

CO H O N SO O Ash

C H N O S H O airw a y

b c d e f

2

, ,,

, , ( ), ,,

298 298

298

loss k k fly ash p ash out bottom ash p ash ashproducts out

fuel DAF fuel DAF H O l fuel ash p ash fuel k kair in

Q N h m c T m c T

N h wh m c T N h

Mass balance:

Energy balance:

Direct coal and biomass blend and injection if biomass heat fraction ≤ 2%

Secondary and tertiary air

Additional injection system for biomass if biomassheat fraction > 2%

Secondary and tertiary air

Emissions for MBB blends generally:

• Lower in nonrenewable CO2,

• Higher in SO2, and • Higher in fly ash.

Higher bottom ash levels

CVref

Q

Co-firingBlending coal

with biomass in primary burn

region

Project time (yrs)

Ca

sh

Flo

ws

(D

olla

rs)

3015 20 255 10

Diesel, natural gas, propane fueling costs

Labor & Maintenance

Coal savings

Avoided CO2 and NOx emission allowances New plant equipment and retrofit

Dryer facility and equipment

Transport vehicles

Annual Cash Flows Capital Costs

Project time (yrs)

Ca

sh

Flo

ws

(D

olla

rs)

3015 20 255 10

Operating cost/revenueNew plant equipment and retrofit

Dryer facility and equipment

Transport vehicles

Annual Cash Flows Capital Costs

Operating cost or revenue

, , ,

2 2

& & &n total drying n total truck n cofire n n

n n n n x n

Operating Income O M O M FO M Coal Savings

CO Savings SO Cost Ash Disposal Ash Sale NO Savings

Project time (yrs)

Ca

sh

Flo

ws

(D

olla

rs)

3015 20 255 10

Net Present Value

Net Present Worth

Net Present Cost

OR

1n

nDiscount factor DR

$ n

n presentn

Income after taxDiscounted Income

Discount factor

30

1

$ present n totaln

NPW Discounted Income Investment

Project time (yrs)

Ca

sh

Flo

ws

(D

olla

rs)

3015 20 255 10

Annualized cost or revenue

Annual Cash Flows

30

30

1$/

1 1

DR DRAnnualized Cost Revenue NPW

yr DR

2 2 2 2

22

, , , , ,

$

CO no cofire CO cofiring reported CO drying CO trucks

Specifc CO Reductionmetric ton CO

Annualized Cost

E E E E

Co-firing with BiomassSteps in Analysis

1) Compiled modeling equations into a spreadsheet computer program (Excel).

2) Generated a base case reference run of the program.

3) Conducted a sensitivity analysis of the net present worth of the co-fire system by varying each individual parameter, while holding all other parameters constant.

Base case Inputs for Co-firing

• Plant base inputs:– Plant Capacity: 300 MWe (35% efficiency)– Burning WY sub-bituminous– FGD is installed, 20% of ash is sold

• Co-firing Biomass– 5% (by mass) low-ash dairy biomass– Each biomass dryer has a 2 dry metric ton

capacity (fueled with natural gas)– Biomass transported 80 km (50 miles)

Base case Inputs for Co-firing

• Pricing– Coal: $30/ton (3.77% annual escalation)– CO2 value: $3.50/ton (5.25% escalation)– SOx value: $880/ton (4% escalation)– Natural gas: $7.76/MMBtu (5% escalation)– Electricity: $0.09/kWhe (3.70% escalation)– Diesel: $3.00/gallon (5% escalation)

• Economics:– 5.3% non-inflated discount rate– 4% inflation 9.5% inflated discount rate– 12.1% capital charge rate– 34% tax rate (MACRS of depreciation)

Year 1 CostsCoal Combustion

onlyCo-firing Coal with

BiomassFixed O&M Cost 0 (67,261)

Variable O&M Costa 0 (2,155,166)Biomass Delivery Cost 0 (620,100)

Coal Delivery Cost (43,878,448) (42,265,847)CO2 Penalty (7,800,913) (7,574,966)

SO2 Penalty (314,864) (329,081)

Ash Revenue 368,704 368,601Ash Disposal Cost (1,769,781) (1,993,493)

Annualized Capital Cost 0 (594,887)TOTAL COST (w/o capital) (53,395,301) (54,637,314)aFor MBB, variable O&M includes the cost of drying the biomass

Year One Comparison

Total Operating Cost @ Y1 = $1.2 million

(6.0)

(5.0)

(4.0)

(3.0)

(2.0)

(1.0)

0.0

1.0

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

Project Year

Mill

ion

Do

llars

Total Operating Cost (real dollars)

Discounted Operating Cost (present dollars)

Total Initial Investment:$5.9 million

Annual Cash Flow for Base Case

NPW = -$22.6 million

Base Case Results

• Total investment for plant equipment, dryers, and trucks = $5.9 million

• NPW = -$22.6 million– Annualized cost = $2.30 million per year

– Cost of reducing CO2 = $35.68/ton CO2

– Cost of co-firing = 0.11 ¢/kWhe

• If avg. household consumes 940 kWhe per month, co-firing with manure biomass would increase electric bills by about $1.03 per month.

Effect of Coal Prices

(5.0)

(4.5)

(4.0)

(3.5)

(3.0)

(2.5)

(2.0)

(1.5)

(1.0)

(0.5)

0.0

0 10 20 30 40 50 60 70

coal price at year 1 ($/metric ton)

An

nu

aliz

ed C

ost

/Rev

enu

e o

f C

o-f

irin

g(m

illio

n $

/yea

r)

(45)

(40)

(35)

(30)

(25)

(20)

(15)

(10)

(5)

0

30-y

ear

Net

Pre

sen

t W

ort

h (

mill

ion

$)

Coal price escalates annually by 3.77%

Effect of CO2 Value

(3.0)

(2.5)

(2.0)

(1.5)

(1.0)

(0.5)

0.0

0.5

1.0

1.5

2.0

0 10 20 30 40 50 60

CO2 value at year 1 ($/metric ton CO2)

An

nu

aliz

ed C

ost

/Rev

enu

e o

f C

o-f

irin

g(m

illio

n $

/yea

r)

(30)

(25)

(20)

(15)

(10)

(5)

0

5

10

15

20

30-Y

ear

Net

Pre

sen

t W

ort

h (

mill

ion

$)

CO2 credit values increase annually by 5.25%

Co-firing with biomass becomes profitable

Cost components of co-firing vs. transport distance

0

10

20

30

40

50

60

70

80

90

100

0 16 80 161 241 322

average distance between plant and animal feeding operation (km)

Per

cen

tag

e o

f M

anu

re-b

ased

Bio

mas

sC

o-f

ire

O&

M C

ost

at

Yea

r 1

Co-fire O&M Transportation Cost Drying O&M

70 – 80% of drying cost due to

natural gas

0.76

1.76

3.95

2.02

1.22

0.0

1.0

2.0

3.0

4.0

5.0

TX Lignite WY Sub-bituminous LA Dairy BiomassDried off the Plant(with natural gas)

LA Dairy BiomassDried at the Plant

(i.e. no natural gas)*

LA Dairy Biomass ifNo Drying Needed

(already < 30%moisture)

As-

del

iver

ed F

uel

Co

st (

$/G

J)

--300 MW Plant--80 km (50 mile) transport distance--Natural gas: $7.76/MMBtu--Diesel: $3.00/gal--Drying from 60% to 20% moisture*Not accounting for investment cost of installing heat exchanger at power plant

Cases where natural gas may not be needed

May be the case for dairies and feedlots

in the Texas Panhandle Region

NPW = -$22.6 million

NPW = +$2.1 million

Waste heat utilized from power plant

Primary Coal Injection• Along with primary

combustion air

Reburn Fuel Injection• Usually natural gas or coal, but

could be manure biomass,• 10-20% of the plant heat rate• Rich mixture, ER = 1.05 – 1.2• Temperature: 1300-1500 K

High NOx emission

Lower NOx emission60 to 90% reduction

Over Fire Air• Completes the combustion

process

Exhaust Gases• With acceptable NOx

emission• Lower CO2 emission from

nonrenewable sources

Higher bottom ash levels

CVref

Q

Reburning to reduce NOx

Different base case inputs for Reburning

• Tangentially fired boiler using low-NOx burner with closed coupled over fire air– Primary NOx control can achieve levels of 0.20

lb/MMBtu

• Reburn fuel is pure low-ash dairy biomass– 10% heat contribution to overall heat rate

• (13% by mass)

– Reburning achieves levels of 0.06 lb/MMBtu

• Alternatively, SCR can also achieve levels of 0.06 lb/MMBtu

• NOx value: $2,600/ton NOx (4.5% escalation)

Effect of NOx Value

(10000)

(8000)

(6000)

(4000)

(2000)

0

2000

4000

6000

8000

10000

0 1000 2000 3000 4000 5000 6000 7000 8000

NOx credit value at year 1 ($/metric ton)

Sp

ecif

ic N

Ox

Re

du

cti

on

Co

st/R

even

ue

($/m

etr

ic t

on

NO

x)

annual escalation of NOx value 10.0%

1.0%

4.5%

Section 1:The cost of reducing NOx by

reburning is greater than the current value of a metric ton of NOx.

Section 3:The revenue from reducing NOx by

reburning is greater than the current value of a metric ton of NOx.

Section 2:The cost of reducing NOx by reburning is less

than the current value of NOx

Effect of NOx Value

(8)

(6)

(4)

(2)

0

2

4

6

8

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

NOx credit value at year 1 ($/metric ton)

An

nu

aliz

ed C

ost

/Rev

enu

e (m

illio

n $

/yea

r) SCR

Manure-based biomass

reburning

NOx credit values escalate annually by 4.5%

Option 2Small-scale, On-the-farm

Combustion

Solids Separator

Pump

Process (e.g. space heating, hot water generator,

etc.)

Flushed Manure Slurry

90-99% moisture

Semi solids50-70% moisture

Vapor Exhaust

Biomass Solids 15-30% moisture

Bottom Ash

Exhaust Products

Wastewater 1-6% solids

Condensate for continued flushing

Recycled wastewater for flushing or treatment lagoon

Saturated Steam

Remaining solids%M=??

Condensate for continued flushing

Proposed Manure Waste Disposal Combustion Proposed Manure Waste Disposal Combustion System for on-the-farm disposalSystem for on-the-farm disposal

Combustion Air

Air

Air

Disposal Efficiency

1 8, 5

1

ew adisposal

m m m

m

Mass of flushed manure leaving the animal housings

Mass of wastewater not vaporized in the boiler

Mass of remaining ash

Tracking Results in Spreadsheet

Overall System Results: Mass Flow (kg/s) and Temperature (K)

Dry air 0.1995Moisture 0.0019 Steam 0.2097Temp 298 Temp 417

Dry exhaust 0.2130Moisture 0.0114 Steam 0.0114 Moisture 0.0216

Solids 0.0131 Temp 417 Temp 417 Temp 420Moisture 0.4233Temp 298

Solids 0.0106Moisture 0.3421Temp 298

Solids 0.0237Moisture 0.7655Temp 298 Vapor 0.1010

Temp 385Steam 0.0964

Solids 0.0447 Temp 417Moisture 0.8496 Dry air 0.1995Temp 298 Moisture 0.0019

Temp 416Solids 0.0316Moisture 0.1089Temp 298

Ash 0.0063Solids 0.0210 Temp 1,993Moisture 0.0842 Moisture 0.0964 Solids 0.0316Temp 298 Temp 417 Moisture 0.0079

Temp 370 Extra fuel 0.0000Boiler Press. 300 kPa (gage) Moisture 0.0000Flame Temp 1,993 K Temp 298

Solids 0.0106Moisture 0.0247Temp 417

Solids Separator

Pump

Air Pre-heater

Dryer Design

Vapor Exhaust

Solids into Dryer

Saturated Steam

Dried Solids

Condensate3

9d

10

11

2

Vapor Exhaust

Solids into Dryer

Saturated Steam

Dried Solids

Condensate3

9d

10

11

2

0

500

1,000

1,500

2,000

2,500

01020304050607080

moisture percentage of dried solids for combustion, %M 3

Was

tew

ater

Mas

s F

low

(kg

/hr)

0

500

1,000

1,500

2,000

2,500

Ad

iab

atic

Fla

me

Tem

per

atu

re (

K)

not vaporized

vaporized

flame temperature

(10% excess air)

Drier Solids

Effect of Ash Percentage

0

500

1,000

1,500

2,000

2,500

0 10 20 30 40 50

ash percentage in biomass (dry basis)

Rem

ain

ing

Was

tew

ater

(kg

/hr)

30

35

40

45

50

55

60

65

70

Dis

po

sal

Eff

icie

ncy

(%

)

disposal efficiency

remaining wastewater

Additional Fueling

40

50

60

70

80

90

100

0.00 0.05 0.10 0.15 0.20

additional fuel, mf EF (kg of extra fuel / kg of total fuel burned)

Dis

po

sal

Eff

icie

ncy

(%

)

CH4 C3H8 Texas Lignite

Summary

• Bottom line:– Large scale combustion of

manure-based biomass can be profitable, but a lot has to happen.1. Manure must be low in

ash2. Coal prices must be high

3. NOx and CO2 values must be high and expected to escalate

4. Using high-grade fuels to dry the manure should be avoided

5. Reburning is theoretically more profitable than co-firing, but there are many feasibility issues and simply not enough possible applications for reburning in the US.

– Small scale combustion is highly dependant on two things1. Avoided manure waste

disposal costs2. Earning profit from

electricity or thermal commodity (e.g. steam) production

Summary (cont.)

• Currently, given the high cost of transporting manure and preparing it for combustion in coal burners, as well as the lack of available low-ash manure and the lack of real dollar benefits, small-scale combustion is preferable.

• Future carbon taxes or cap-n-trade programs can greatly improve the possibility of burning manure biomass in coal-fired power plants.

Summary (cont.)

• As for drying and transporting:– Rotary dryers were found to consume slightly

less heat energy than conveyor belt dryers– Due to the relationship between manure

density and moisture percentage, there seems to be little difference in costs between transporting manure with 20% moisture and manure with 60% moisture.

– Although transporting liquid manure, >90% moisture, is significantly more expensive.

Acknowledgments

• DOE--Golden, Colorado, Grant #DE-FG36-05GO85003 and

• Texas Commission on Environmental Quality (TCEQ), Grant #582-5-65591 0015

Questions?Questions?ncarlin50@hotmail.com