Life-cycle Inventory of Wood Fuel Pellets Manufacturing from Hardwood Flooring Residues in the Southeastern United States

Transcription

1 Life-cycle Inventory of Wood Fuel Pellets Manufacturing from Hardwood Flooring Residues in the Southeastern United States Reed D., Taylor, A., Bergman R., Harper D., Jones D., Knowles C., Puettmann, M.

2 Overview Gate-to-Gate Life Cycle Inventory Commercial pellet manufacturers were surveyed in 2010 on annual production data for 2009 Input data collected for pelletization process include: wood residues, polyethylene, corn oil, water, electricity, and LPG SimaPro LCA modeling software was used to calculate the overall cradle-to-gate emissions using a network of related inventories associated with inputs for pellets.

3 Goal / Scope Definition The goal of this study is to document the life cycle inventory (LCI) of manufacturing wood pellets based on resources from the Southeast pellet-manufacturing region. The output of this study is intended for use by researchers and practitioners as an input to the life cycle analysis (LCA) of woody biomass materials in a cradle-to-gate analysis.

4 Life Cycle Assessment (LCA) The investigation and valuation of the environmental impacts of a given product (or process) through its life-cycle.

5 Life Cycle Assessment (LCA) The investigation and valuation of the environmental impacts of a given product (or process) through its life-cycle.

6 Life Cycle Assessment (LCA) The investigation and valuation of the environmental impacts of a given product (or process) through its life-cycle.

7 Life Cycle Impact Categories Global Warming Potential Stratospheric Ozone Depletion Photosynthetic Smog Acidification Eutrophication Aquatic Toxicity Air based toxicity Fossil Fuel Depletion Mineral Resource Depletion Biological Resource Depletion Water depletion Land Use

8 The Survey The size of production facilities from the survey ranged from 6,000 to 125,000 tons of wood pellets annually. Of the mills surveyed, six (25%) responded with complete data in terms of pellet production, raw materials, electricity and fuel use. The total production of responding pellet mills was 335,074 tons of pellets a year. The only available data estimated production of the entire Southeast region in 2008 was 652,561 tons (USDA, 2009) which suggests that the survey captured from mills that produce half of the total regional production.

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11 Manufacturing process of wood pellets 1.) Raw Material (Waste) Collection Approximately 50% of hardwood lumber is converted to hardwood flooring; the remainder (sawdust, shavings, trim blocks) is available for the pellet process. 2.) Drying Raw Material Some additional drying is needed for a moisture content of 9 11% Energy Inputs: residues, electricity, LPG

12 3.) Hammermill Broken down into small particles (~2mm) Energy Inputs: electricity 4.) Pelletizing Pellets are extruded using a pelletizer using high temperatures and high pressure Energy Inputs: electricity, oil, grease

13 5.) Cooling The pellets are hot when they emerge from the pelletizer. They are stored in a hopper and allowed to cool before bagging. 6.) Bagging Pellets are bagged, usually in small, semi-automatic bagging lines that are powered by electricity. Energy Inputs: electricity

14 System Boundary : Wood Pellets Functional Unit = 2000lbs of wood pellets

15 Inputs of Wood Pelletization

16 Impact categories showing relative contribution of the inputs

17 Potential and embodied energy in one ton of pellet fuel Mass-based Allocation Value-based Allocation

18 Global Warming Potential (CO2 eq/mj) of wood pellets and natural gas.

19 Summary Operating pellet mills were surveyed to collect data for a gate-to-gate life-cycle inventory. A cradle-to-gate inventory was developed using an existing life-cycle data for wood residues, electricity and the other inputs. The primary inputs for manufacturing wood fuel pellets are wood residues and electricity In the Southeast region, an average of 132 kwh of electricity was reported just for the pelletization of one ton of wood residues Applying mass allocation procedure for wood flooring manufacturing, the production of the wood residues from hardwood lumber contributes the most to the total environmental impacts of the pellets. When value allocation is used most of the environmental impacts are associated with the electricity. The electricity required during pelletization also contributes significantly, e.g. 30% of the GWP and total respiratory effects

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