http://www.extension.org/67582 This presentation will compare using litter as a replacement for LP gas for on-farm space heating with using litter to generate electricity. The comparison includes heating system efficiency, amount of LP off-set possible, value of plant nutrients in the litter, quantity and value of plant nutrients in the litter ash, impact of brokerage, and costs of producing the energy. It was concluded that using litter on-farm as a source of space heat and using the litter ash as fertilizer could provide a potential value of $48 per ton of litter. However, on-farm combustion of litter to produce electricity resulted in a loss of about - $3/ton of litter. Therefore, if a heating and ash management system can be implemented in a cost-effective manner use of litter to off-set 90% or more of the heating energy requirements would be the better of these two alternatives.

1. Combustion of Poultry Litter: A
Comparison of Using Litter for On-Farm
Space Heating Versus Generation of
Electricity
John P. Chastain, Ph.D.
Professor and Extension Agricultural Engineer
School of Agricultural, Forest, and Environmental Sciences
Waste to Worth Conference, Denver, Colorado
Grand Hyatt Hotel • April 1-5, 2013

2. Using Manure For Energy Is an Old
Idea
 People have used manure as an energy source
for thousands of years.
 Dried dung was used as fuel for ovens and
open fires.
 More recently:
 making biogas from slurries,
 Combustion in a furnace, or
 using pyrolysis and exhaust-gas reburn.

3. Poultry Litter Contains a Significant
Amount of Energy
 Average HHV = 6202 Btu/dry lb
 If litter has a moisture content of 24%
the LHV is 4480 Btu/wet lb.
 Unfortunately we cannot use all of this
heat.
 No method of heating or generating
electricity is 100% efficient.

4. How much litter is in one 42’ x 500’ broiler
house?
Estimate based on measurements in a SC broiler house.
So for a 6-house farm the litter production
= 846.8 tons/year.
Litter Depth = 5.675 in
Moisture Content = 24 %
Bulk density = 28.4 lb/ft3
Floor Area of 1 house = 21000 ft2
Litter volume = 9931.25 ft3
Mass of litter / house = 141.13 tons/yr

5. Can we burn this litter on-farm
to off-set LP gas needs?
Will we have enough?

6. Several groups and companies are
developing poultry litter furnaces
 Turkey litter in Missouri
(on-farm heat)
 Broiler litter in Arkansas
(Tom Costello, on-farm
heat).
 American Heat and Power
(Habetiz and Echols,
power plant)
Brisco Farm, Mo. www. ecoagri.biz
http://www.americanheatandpower.com/PoultryLitterEnergy.html

7. The efficiency of the poultry house
determines how much LPG is needed.
Table 2. Estimates of annual LP gas use for
heating in broiler houses based on house
energy efficiency and number of flocks grown
per year.
Level of Broiler
House Energy
Efficiency
5 Flocks per
Year
5.5 Flocks
per Year
gal LP per year per 1,000
square ft of house
Very efficient 120 132
Efficient 150 165
Average 180 198
Low 200 220
Very low 270 297

8. LP Gas use measured on SC broiler farms:
“Typical” Values
LPG Use Rate = 240 gal LP /1000 ft2
/yr
LPG Use / house = 5040 gal LP /yr
LP Use / 6-house farm = 30240 gal LP /yr

9. Need an estimate of overall heating system
efficiency.
 Heating system efficiency takes into account
the efficiency of the furnace and the
efficiency of distributing the heat to the
broiler house.
 It can be as low as 20% with 40% being a
reasonable target (Costello, 2007).
 So that means for every 1000 Btu of heat in
the litter only 400 Btu will be used to heat the
house!

10. So how much heat is in the litter on a 6-
house farm?
With this heating system 1 ton of litter can
replace 38.75 gal of LP!
litter/6-house farm = 846.8 tons/yr
Heat Value of Wet Litter = 8960000 Btu/ton
Heat Content = 7587309744 Btu/year
Heating System Efficiency = 40 %
Heat delivered to houses = 3034923898 Btu/year
Energy Content of LP = 92,500 Btu/gal LP
LPG equivalence = 32810 LPG Eq./year
LPG Eq./ton of litter = 38.75

11. So would there be enough litter to heat
these houses?
 Produce 846.8 tons/year
 Need 30,240 gal LP/year
 1 ton of Litter replaces 38.75 gal LP
 So I need: 30,240 gal LP
÷ 38.75 gal LPG Eq./ton = 780.4 tons
(66.4 tons extra?)
 Yes, if heat can be produced and delivered when
needed. Expect 80% to 100% depending on
weather.

12. Need to remember that burning litter will
produce ash that must be managed.
 Litter ash cannot be used as a lime
substitute.
 Has high concentrations of P, K, and
minor nutrients.
 Does not contain N.
 Must be spread based on P2O5 or K2O.

13. How much ash and plant nutrients will be
produced?
1 Broiler 6-House
House Broiler Farm
Ash production if 100% of LPGis off-set (ton/yr) 24.4 147
Plant nutrient yield in ash
P2O5 (ton/yr) 2.20 13.2
K2O (ton/yr) 1.90 11.4
Ca (ton/yr) 1.40 8.4
Mg (ton/yr) 0.30 1.8
S (ton/yr) 0.28 1.7
Zn (lb/yr) 35.6 214
Cu (lb/yr) 37.6 226
Mn (lb/yr) 43.5 261

14. How much land is needed?
1 Broiler 6-House
House Broiler Farm
Ash production if 100% of LPG is off-set (ton/yr) 24.4 147
Plant nutrient yield in ash
P2O5 (ton/yr) 2.20 13.2
K2O (ton/yr) 1.90 11.4
Land area needed if ash is spread based on 89 lb P2O5/ac (acre/yr) 49.4 296
Ash application rate (ton/acre) 0.49
Land area needed if ash is spread based on 45 lb K2O (acre/yr) 84.4 506
Ash application rate (ton/acre) 0.29

15. What is the value of the ash if spread based
on P2O5 for a 6-house farm?
 Value of P2O5 = 13.2 ton/year x 2000 lb/ton x
$0.69/lb = $18,216/year
 Value of K2O = 11.4 ton/year x 2000 lb/ton x
$0.50/lb = $11,400/year
 Total value = $29,616/year
 Can this be used for the poultry producer’s
cropping enterprise?

16. What would the savings be if litter replaced
LP? – Scenario 1: Use ash on own land.
 LP gas for a 6-house farm = 30,240 gal/year
 Assume price is $1.90/gal
 Value of LP savings = $57,456
 However all N was lost in the litter that was burned
– 780.4 tons burned.
 PAN = 44 lb PAN/ton @ $0.71/lb
 N-lost was worth $24,380
 P & K Value = $29,616/year
 Net gain = $62,692/year (LP saved – N lost + P&K)

17. What would the savings be if litter replaced
LP? – Scenario 2: No land - brokerage
 LP gas for a 6-house farm = 30,240 gal/year
 Assume price is $1.90/gal
 Value of LP savings = $57,456
 Brokerage payments lost on the 780.4 tons burned.
 Litter price = $15/ton
 Loss of Brokerage Payment = $11,706
 P & K Value = ($29,616/year x 0.33) = $9,773
 Net gain = $55,523/year (LP saved – Loss + P&K/3)

18. The big questions is…
 Can annual savings of $55,523 to $62,692
per year pay for the heating system fast
enough?
 Cost to produce an LPG Eq. is about $0.55 to
$0.65/LPG Eq. in other systems studied.
 Assume we can make a LPG Eq. for $0.65.
 30,240 gal LPG Eq. x $0.65 = $19,656/year
 Annual savings is closer to $35,867 to
$43,036 per year.

19. Value per ton of litter
 Burned 780.4 tons of litter
 Annual savings $35,867 to $43,036 per
year.
 Value of litter =$46 to $55/ton

20. Electricity use based on data collected on
SC broiler farms
Cost per kWh = $0.077 to $0.122
kWh Use Rate = 2326 kWh/1000 ft2
/yr
kWh Use / house = 48846 kWh/yr
kWh Use / 6-house farm = 293076 kWh/yr

21. Can litter be burned to generate electricity?
 Yes – but may not be cost-effective on-farm
 Need a steam boiler and turbine. Cost to
produce a kWh is high for small units.
 Smallest units are on the order of 1000 kW.

22. Average overall efficiency for coal-fired,
steam power plants in the US is 32%.
(Beer, 2012)
Most of the energy in the fuel is lost as
heat.

23. To run a 1 MW plant requires (Chastain et
al., 2012)…
 Biomass fuel feed rate = 2381 lb litter /hr
 Need 10,429 tons of litter / year!
 Gross energy production
= 8,759,891 kWh/year
 Gross kWh/ton of litter = 840
 Need 74, 42’ x 500’ broiler houses

24. Net kWh for a 1 MW plant (Chastain et al.,
2012)…
 Gross energy production
= 8,759,891 kWh/year
 Gross kWh/ton of litter = 840
 Need 74, 42’ x 500’ broiler houses
 Electrical use by houses
= 3,614,604 kWh/year
 Net energy to grid = 5,145,287 kWh/year
 Net kWh/ton of litter = 493 (59%)

25. So only 590 kW of a 1000 kW power
plant would be available to supply
energy to something besides the farms
that generate the litter.
Not horrible, but needs to be considered!
Nothing is 100% efficient!
Makes co-firing of coal & litter look attractive.

26. A 1 MW litter powered plant will
produce…
 1957 tons of litter ash.
 176 tons of P2O5.
 152 tons of K2O
 Using our previous price assumptions the ash
has a value of at least $394,880.
 Seems like a larger power plant would be
needed to justify construction of a fertilizer
plant.

27. Results for a Single Farm with Best
Assumptions
 1 broiler house can support 13.5 kW.
 A 6-house farm could operate a 80 kW generator.
 The on-farm generator could produce 711,312
kWh/year
 293,076 kWh per year could be used on-farm.
 Excess would be 418,236 kWh/year
 Potential value = $0.12 x 293,076 + $0.045
x 418,236 = $53,990/year

28. Are you lowering your costs in this case?
 Value of electricity = $53,990/year
 The lowest price to produce a kWh in this system is
about $0.08/kWh.
 Lowest cost to produce = 711,312 kWh/year
x $0.08/kWh = $56,905 /year
 Are you making money for your trouble?
 No. Loss of at least $3000 / year or $3.54/ton of
litter (-$3000/846.8 tons/year).

29. Conclusion
 Using litter for heating is the only on-farm
alternative that makes sense at this time.
 Value of litter (100% use) will range from $46 to
$55/ton
 Matching heat demand is tough and will prevent
100% utilization of litter for combustion.
 Need large scale to be in the electric power business.
 Key is to understand cost to produce energy on farm
which will vary greatly.

30. Agricultural Mechanization &
Business
School of Agricultural, Forest, and
Environmental Sciences
Contact:
Christi Leard
864.656.3250