Example of Small LCA Project

Steps of an LCA

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

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

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

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

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)

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)

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

Results – Impact Assessment Emission factors (fossil and wood burning) Total emissions for house (fossil and wood burning)

Results – Emission Factors Considers upstream emissions

Results – Emissions from Original

Results – Emissions with Stove

Results Net Changes

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

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

Impact of Various Stages CO2 kgNOx gSOx gPM g Gas comb Gas upstream 100 2, Gas subtotal 1,026 3, Coal comb. 2,391 2,053 6,506 22,812 Coal upstream ,562 Coal subtotal 2,452 2,434 6,772 27,375 Wood comb. 0 3, ,956 Wood upstream 193 4, ,922 Wood subtotal 193 7, ,878 System total 3,670 13,877 7,527 41,253

Summary of Impacts

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

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

Other Potential Problems Wife not happy with me gutting the fireplace and redoing it according to manufacturers specs Estimates on fuel consumption during wood cutting Happy cat though