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Example of Small LCA Project
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Example of Small LCA Project. Steps of an LCA Goal Definition and Scope Evaluate burning firewood in residential application as a supplement to fossil.

Mar 31, 2015

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Antony Commer
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Page 1: Example of Small LCA Project. Steps of an LCA Goal Definition and Scope Evaluate burning firewood in residential application as a supplement to fossil.

Example of Small LCA Project

Page 2: Example of Small LCA Project. Steps of an LCA Goal Definition and Scope Evaluate burning firewood in residential application as a supplement to fossil.

Steps of an LCALife Cycle Assessment Framework

Goal definition and

scope

Inventory analysis

Impact assessment

Interpretation

Page 3: Example of Small LCA Project. Steps of an LCA Goal Definition and Scope Evaluate burning firewood in residential application as a supplement to fossil.

Goal Definition and Scope

• Evaluate burning firewood in residential application as a supplement to fossil

• House is in Kentucky and current heating is with an air source heat pump and natural gas furnace

• Determine impact of current fossil fuel consumption with supplemental wood heat

Page 4: Example of Small LCA Project. Steps of an LCA Goal Definition and Scope Evaluate burning firewood in residential application as a supplement to fossil.

Scope Continued

• Consider impact of power plant and combustion of nat gas in house

• Harvest and transport of firewood from Berea• Impacts considered

– CO2– NOx– SOx– Particulate matter (PM)– Costs

Page 5: Example of Small LCA Project. Steps of an LCA Goal Definition and Scope Evaluate burning firewood in residential application as a supplement to fossil.

Inventory Analysis - Procedure

• Obtained previous years utility bills• Picked lowest month and used that bill as

baseload electrical/gas consumption• Estimated fuel consumption for chainsaw and

log splitter• Estimated quantity and energy value of

firewood

Page 6: Example of Small LCA Project. Steps of an LCA Goal Definition and Scope Evaluate burning firewood in residential application as a supplement to fossil.

Existing Appliance Performance

• Air source heat pump– COP at 47F is 3.6, COP at 17F is 2.5– Assume average of 3.0– Actually two heat pumps in house, assume both are

same (similar performance)• Gas furnace is 80% AFUE• Use on a seasonal heating basis

– 4600 kWh of electricity (15.7 million Btu)– 31.4 MCF (31.4 million Btu)

• We need 76.2 GJ/heating season in the house

Page 7: Example of Small LCA Project. Steps of an LCA Goal Definition and Scope Evaluate burning firewood in residential application as a supplement to fossil.

Emissions from Fossil

• Natural gas appliances in residential applications – DOE EERE (2008 standards)

• Emissions from power plants DOE – EIA KY electric profile (2009)

• PM from coal combustion NREL (1999)

Page 8: Example of Small LCA Project. Steps of an LCA Goal Definition and Scope Evaluate burning firewood in residential application as a supplement to fossil.

Wood Burning Characteristics

• Energy content from University of MO for hackberry (21.6 million btu/cord)

• Estimated 2.5 cords of firewood (5 pickup loads)

• Emissions from fireplace – EPA certified stoves– 36,000 btu/hr output at 63% efficient– 4.42 g PM/hr

• Other emissions (NOx and SOX) from 1999 EPA document (g/kg basis)

Page 9: Example of Small LCA Project. Steps of an LCA Goal Definition and Scope Evaluate burning firewood in residential application as a supplement to fossil.

Wood Harvest

• EPA standards for SI gasoline engines under 18 hp (Federal Register for 2000)

• Assume engines are 33% efficient – no reference

• Emissions listed for– CO (assume all goes to CO2)– HC+NOx (from EPA, 2/3 of this category would go to

PM, assume this is true, based on cars)– Gasoline 340 ppm sulfur – assume goes to 2.78 g

SO2/gallon

Page 10: Example of Small LCA Project. Steps of an LCA Goal Definition and Scope Evaluate burning firewood in residential application as a supplement to fossil.

Results – Impact Assessment

• Emission factors (fossil and wood burning)• Total emissions for house (fossil and wood

burning)

Page 11: Example of Small LCA Project. Steps of an LCA Goal Definition and Scope Evaluate burning firewood in residential application as a supplement to fossil.

Results – Emission Factors

Considers upstream emissions

Natural gas Electricity Wood

Em

issi

on F

acto

r (g

/GJ

or k

g/G

J)

0

500

1000

1500

2000

2500

3000

3500

CO2 (kg/GJ) NOx (g/GJ) SOx (g/GJ) PM (g/GJ)

Page 12: Example of Small LCA Project. Steps of an LCA Goal Definition and Scope Evaluate burning firewood in residential application as a supplement to fossil.

Results – Emissions from Original

Natural gas Electricity Total

Em

issi

ons

in a

Hea

ting

Sea

son

(kg

or g

)

0

10000

20000

30000

40000

50000

60000

CO2 (kg) NOx (g) SOx (g) PM (g)

Page 13: Example of Small LCA Project. Steps of an LCA Goal Definition and Scope Evaluate burning firewood in residential application as a supplement to fossil.

Results – Emissions with Stove

Natural gas Electricity Wood Total

Em

issi

ons

in H

eatin

g S

easo

n (k

g or

g)

0

10000

20000

30000

40000

50000

60000

CO2 (kg) NOx (g) SOx (g) PM (g)

Page 14: Example of Small LCA Project. Steps of an LCA Goal Definition and Scope Evaluate burning firewood in residential application as a supplement to fossil.

Results Net Changes

Reduction

Red

uctio

n U

sing

Woo

d S

tove

(%

)

-60

-40

-20

0

20

40

CO2 NOx SOx PM

Page 15: Example of Small LCA Project. Steps of an LCA Goal Definition and Scope Evaluate burning firewood in residential application as a supplement to fossil.

Interpretation - Existing

• Air source heat pump reduces impact due to COP– Use half the energy of natural gas– Get over 2/3 of useful heat from electricity

• Natural gas high NOx emissions • Coal has high CO2, SOx, and PM

Page 16: Example of Small LCA Project. Steps of an LCA Goal Definition and Scope Evaluate burning firewood in residential application as a supplement to fossil.

Interpretation - Wood

• 45% reduction in fossil energy• Assumed evenly split between gas/electric• Significant reduction in CO2 and SOx relative

to base case• PM slightly lower than base• NOx increased relative to base case

– Small SI engines big part of NOx emissions

Page 17: Example of Small LCA Project. Steps of an LCA Goal Definition and Scope Evaluate burning firewood in residential application as a supplement to fossil.

Impact of Various StagesCO2 kg NOx g SOx g PM g

Gas comb. 926 732 - - Gas upstream 100 2,800 - - Gas subtotal 1,026 3,532 - - Coal comb. 2,391 2,053 6,506 22,812 Coal upstream 61 381 266 4,562 Coal subtotal 2,452 2,434 6,772 27,375 Wood comb. 0 3,490 698 7,956 Wood upstream 193 4,421 56 5,922 Wood subtotal 193 7,911 754 13,878 System total 3,670 13,877 7,527 41,253

Page 18: Example of Small LCA Project. Steps of an LCA Goal Definition and Scope Evaluate burning firewood in residential application as a supplement to fossil.

Summary of Impacts

Page 19: Example of Small LCA Project. Steps of an LCA Goal Definition and Scope Evaluate burning firewood in residential application as a supplement to fossil.

Life Cycle Costing

• $661/yr in heating for fossil case• With wood stove increases to $759/yr

– Due to cap cost of stove (~400/yr)• Would take a 40% increase in electric and nat.

gas cost to be equal• No value on time handling firewood

Page 20: Example of Small LCA Project. Steps of an LCA Goal Definition and Scope Evaluate burning firewood in residential application as a supplement to fossil.

Potential Problems

• Uncertainty in electricity used for heating – based on lowest electric bill

• Assumed a SI engine efficiency• Assumed conversion of HC to PM

– Other conversions from g C to g CO2 and g S to g SO2

• Splitting of energy reduction – assumed equal gas and electric

Page 21: Example of Small LCA Project. Steps of an LCA Goal Definition and Scope Evaluate burning firewood in residential application as a supplement to fossil.

Other Potential Problems

• Wife not happy with me gutting the fireplace and redoing it according to manufacturer’s specs

• Estimates on fuel consumption during wood cutting

• Happy cat though