 |
|
 |
|
 |
|
 |
|
 |
|
 |
|
 |
|
 |
|
CORRIM: Phase I Interim ReportAppendix D
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|
EXECUTIVE SUMMARY FOR PACIFIC NORTHWEST AND SOUTH PLYWOOD PRODUCTION
The objective of this study is to develop a life cycle inventory
(LCI) for the production of softwood plywood as manufactured in
the Pacific Northwest (Oregon and Washington) and the South (Alabama,
Arkansas, Florida, Georgia, Louisiana, Mississippi, and Texas).
Softwood plywood is considered a structural panel product, and is
used for roof, wall and floor sheathing and sub-flooring in residential
and commercial construction. Wood species used for veneers to make
plywood in the Pacific Northwest include Douglas fir, hemlock, and
some spruce and western larch, whereas wood species used to make
plywood in the South include loblolly and slash pine (referred to
as Southern Pine). Plywood plants were surveyed in these two regions
to record all inputs and outputs associated with the production
process. Input data collected included transportation distances
and the use of wood, bark, electricity, fuel and resin. Output data
quantified plywood product, co-products of chips, trimmings, clippings,
bark, and sawdust, as well as emissions to land, water and air.
Five plywood manufacturing plants in the Pacific Northwest (PNW)
and five plants in the South were surveyed. The Year 2000 production
for these plants represented 26% and 14% of total production, respectively,
for each region. The surveyed plants produced 1.23 billion square
feet (MMMSF) 3/8-in basis in the PNW and 1.38 billion square feet
(MMMSF) 3/8-in basis in the South.
A unit process approach was taken in modeling the LCI of manufacturing
plywood. The plywood process was defined in terms of six sub-unit
processes bucking and debarking, block conditioning, peeling and
clipping, drying, lay-up and pressing, and trimming and sawing.
The rationale for this approach is that this type of model would
be useful in analyzing ways to improve process efficiency, optimize
operations, and find means to reduce environmental impacts. This
could not be achieved using a simple "black-box" approach.
With the recent attention given to conservation of raw materials,
dramatic increases in the cost of electricity and fuel, and the
substantial cost of emissions mitigation, it has become imperative
to address these concerns. The LCI data would be useful as a benchmark
to assess environmental performance and economic feasibility of
process improvements.
As expected, the major use of electricity and heat (generated with
fuel) were the drying and pressing sub-unit processes and to a lesser
extent the conditioning process. The same was true for emissions.
All inputs and outputs were determined per thousand square feet
(MSF) 3/8-inch basis of plywood. The PNW used 1.39E+06 Btu of heat
in processing, of which 90.5% was from hogged fuel and the other
9.5% was from natural gas. Similarly the South used 1.84E+06 Btu
of heat-88.6% from hogged fuel and 11.4% from natural gas. The greater
use of heat in the South is due to the need to remove more moisture
from the veneer. The ability of the plywood industry to generate
a major portion of its heat needs from the combustion of hogged
fuel instead of natural gas provides significant benefit. If the
plants had replaced the hogged fuel with an equivalent amount of
natural gas, at $.55 per therm (100,000 Btu), the PNW plants surveyed
would have had an additional natural gas bill of $17.1 million,
and the South plants would have had an additional $25.4 million
bill. The electricity use per MSF 3/8-in basis of plywood is 138.9
kWh for the PNW and 122.0 kWh for the South. As such, the electricity
bills for the PNW and South plants surveyed are substantial; at
$.06 per kWh, the annual bills would be $10.3 million and $10.1
million respectively. With the projected cost increase of both natural
gas and electricity, means to become more energy efficient will
receive more attention.
The PNW and the South had wood recoveries of 50.7% and 50.4% respectively
as determined by the output of wood in the form of plywood as a
percentage of the wood input to the plant. For the PNW 65.6 ft3
(1,892 lb oven-dry) of wood in log form plus 21.9 lbs of purchased
veneer were required to produce one MSF 3/8-inch of plywood, while
for the South 70.7 ft3 (2,269 lb oven-dry) of wood in
log form and 20.2 lb of purchased veneer were required. The amount
of bark generated during the debarking process was 5.2% and 5.5%
based on the dry weight of bark to dry weight of wood for the PNW
and South respectively.
Emissions and emissions mitigation are becoming increasingly important
in terms of plant operations and manufacturing costs. Emissions
are presented for two cases: 1) total emissions for the entire plywood
manufacturing process, including those associated with the production
and delivery of fuels, electricity, resin, and logs; and 2) emissions
associated with the plywood manufacturing process only. Burdens,
or allocations of emissions, were assigned to products and co-products
on a mass basis. Emissions reported for plywood had a burden of
51.1% and 49.6% for the PNW and South respectively. Approximately
half the emissions were assigned to the plywood and the other half
to the co-products peeler core, chips, clippings, trimmings, veneer
(green and dry), bark, and sawdust. Bark and wood waste used for
hogged fuel were not allocated any emissions. CO2, a
greenhouse gas of international interest, is generated by combustion
of fuels. Since a major portion of the heat generation for the production
of plywood was based upon hogged fuel, it contributed 97% of the
total CO2 emissions from the plant. However, this impact
is negated or greatly lessened by the growing of trees that remove
CO2 from the atmosphere. CO2 values were obtained
from EPA reports.
The quality of the data was considered very good. Based on the amount
of data for the five plants for each region, a comparison of values
established the validity of the data. Additional data analysis (i.e.,
mass and energy balances), as well as regional comparison, further
supported the integrity of our findings. The unit process approach
for modeling the LCI of plywood should prove useful for modeling
other similar processes such as laminated veneer lumber (LVL) production,
which uses green and dry veneer to produce their product. The model
would also be valuable as a tool to optimize operations, and the
LCI data could be used as a benchmark to assess improvements.
Proposed research in the coming year includes scenario analyses
for the LCI plywood model; development of LCI models for glulam,
I-beam, and laminated veneer lumber (LVL); development of LCI models
for phenol-formaldehyde, phenol-resorcinol-formaldehyde, and urea-formaldehyde
adhesives; and documenting carbon balance flows through all the
processes. Within the LCI plywood model a number of scenarios will
be studied. These include: 1) fuel switching-looking at the impact
of hogged fuel versus natural gas in terms of emissions and economics,
2) use of emissions control devices in terms of total emissions
including those for the manufacture and delivery of the electricity
and natural gas used to operate these devices, and 3) energy saving
approaches. Output of the analyses will be compared to the benchmark
data to assess improvements.
TABLE OF CONTENTS
EXECUTIVE SUMMARY FOR PACIFIC NORTHWEST AND
SOUTH PLYWOOD PRODUCTION
1.0 PACIFIC NORTHWEST SOFTWOOD PLYWOOD
1.1 INTRODUCTION
1.1.1
Unit Process Approach
1.1.2
Material Flows
1.1.3
Transportation
1.1.4
Assumptions
1.2 PRODUCT YIELDS
1.3 MANUFACTURING
ENERGY SUMMARY
1.3.1
Sources of Energy
1.3.2
Electricity Use Summary
1.4 HOGGED FUEL
UTILIZATION
1.5 DRYING EMISSIONS
FOR PNW PLYWOOD PRODUCTION
1.6 PRESSING EMISSIONS
FOR PNW PLYWOOD PRODUCTION
1.7 ADHESIVE USAGE
AND ENERGY/ELECTRICITY TO PRODUCE
1.8 PROCESS RELATED
EMISSIONS
1.9 AIR EMISSION
SUMMARY FOR PLYWOOD PRODUCED IN THE PACIFIC NORTHWEST
1.10 LIFE-CYCLE
INVENTORY RESULTS FOR PLYWOOD PRODUCTION FROM THE PACIFIC
NORTHWEST
2.0 SOUTH SOFTWOOD PLYWOOD
2.1 INTRODUCTION
2.1.1
Unit Process Approach
2.1.2
Material Flows
2.1.3
Transportation
2.1.4
Assumptions
2.2 PRODUCT YIELDS
2.3 MANUFACTURING
ENERGY SUMMARY
2.3.1
Sources of Energy
2.3.2
Electricity Use Summary
2.4 HOGGED FUEL
UTILIZATION
2.5 DRYING EMISSIONS
FOR SOUTH PLYWOOD PRODUCTION
2.6 PRESSING EMISSIONS
SOUTH PLYWOOD PRODUCTION
2.7 ADHESIVE USAGE
AND ENERGY/ELECTRICITY TO PRODUCE
2.8 PROCESS RELATED
EMISSIONS
2.9 AIR EMISSION
SUMMARY FOR PLYWOOD PRODUCED IN THE SOUTH
2.10 LIFE-CYCLE
INVENTORY RESULTS FOR PLYWOOD PRODUCTION FROM THE SOUTH
REGION
3.0 PROPOSED RESEARCH FOR COMING YEAR
4.0 REFERENCES
LIST OF FIGURES
| Figure 1.1 | Unit process approach to the modeling of the plywood manufacturing process. |
| Figure 1.2 | System boundary and sub-unit processes used to model the plywood manufacturing process. |
| Figure 2.1 | Unit Process approach to the modeling of the plywood manufacturing process. |
| Figure 2.2 | System boundary and sub-unit processes used to model the plywood manufacturing process. Not included in the sketch are the co-product flows. |
LIST OF TABLES
| Table 1.1 | Listing of input materials, product, and co-products for producing plywood. |
| Table 1.2 | Pacific Northwest delivery distance (one-way) for plywood production. |
| Table 1.3 | Average Density of Wood Species Used To Calculate Mass of Wood From Logs. |
| Table 1.4 | Inputs to produce 1.0 MSF 3/8-inch basis of plywood in the Pacific Northwest. |
| Table 1.5 | Wood mass balance for plywood production from the Pacific Northwest region per 1.0 MSF 3/8-in basis (all weights are on an oven-dry basis). |
| Table 1.6 | Electric power industry generation of electricity by primary energy sources and Statefor the Pacific Northwest region as defined by the U.S. Department of Energy. |
| Table 1.7 | Electricity allocation by sub-unit process for plywood production in the Pacific Northwest. All values are given per 1.0 MSF 3/8-inch basis of plywood. |
| Table 1.8 | Pacific Northwest weighted data conversion of boiler inputs into heat energy for 1.0 MSF 3/8-in basis of plywood. |
| Table 1.9 | Boiler energy requirements for conditioning, drying, and pressing sub-unit processes used in plywood production for the Pacific Northwest. |
| Table 1.10 | Survey data on air emissions for boilers as output from SimaPro 5 (using the FAL1 boiler data) compared to survey data. Total emissions from dryer; no allocations to co-products. |
| Table 1.11 | Emissions for drying plywood from the Pacific Northwest as reported in surveys. Total emissions from dryer; no allocations to co-products. |
| Table 1.12 | Emissions for hot pressing plywood from the Pacific Northwest. Total emissions from press; no allocations to co-products |
| Table 1.13 | Production requirements1 for the 15.88 lb of phenol-formaldehyde resin needed to manufacture 1.0 MSF 3/8-in basis plywood from the Pacific Northwest. |
| Table 1.14 | Air emissions for the production of the 15.88 lb of phenol-formaldehyde resin needed to produce 1.0 MSF 3/8-in plywood. |
| Table 1.15 | Process emissions for plywood production from the Pacific Northwest region. Includes emissions for the production and delivery of electricity, fuel, and adhesive. |
| Table 1.16 | Air emission summaries for 1.0 MSF 3/8-in basis of softwood plywood produced in the Pacific Northwest region. |
| Table 1.17 | Life-cycle inventory results for producing 1.0 MSF 3/8-in basis of plywood in the Pacific Northwest. |
| Table 1.18 | Life-cycle inventory results for 1.0 MSF 3/8-in basis plywood production from the Pacific Northwest region |
| Table 1.19 | Life-cycle inventory results for production of 1.0 MSF 3/8-in basis plywood in the Pacific Northwest. |
| Table 1.20 | Life-cycle inventory results for 1.0 MSF 3/8-in basis plywood production from the Pacific Northwest region. |
| Table 2.1 | Listing of input materials, product, and co-products for producing plywood. |
| Table 2.2 | South Delivery Distance (One-Way) For Plywood Production. |
| Table 2.3 | Average Density of Wood Species Used To Calculate Mass of Wood From Logs. |
| Table 2.4 | Inputs to produce 1.0 MSF 3/8-inch basis of plywood in the South. |
| Table 2.5 | Wood mass balance for plywood production from the South region per 1.0 MSF 3/8-in basis (all weights are on an oven-dry basis). |
| Table 2.6 | Electric power industry generation of electricity by primary energy sources and state for the South region as defined by the U.S. Department of Energy (2000). |
| Table 2.7 | Electricity allocation by sub-unit process for plywood production in the South. All values are given per 1.0 MSF 3/8-in basis of plywood. |
| Table 2.8 | Southeast weighted data conversion of boiler inputs into heat energy for 1.0 MSF 3/8-in basis of plywood. |
| Table 2.9 | Boiler energy requirements for conditioning, drying, and pressing sub-unit processes used in the production of plywood for the South region |
| Table 2.10 | Survey data on air emissions for boilers as output from SimaPro 5 (using the FAL1 boiler data) compared to survey data. These are total emissions; no burden or allocation has been made to co-products. |
| Table 2.11 | Emissions for drying plywood from the South as reported in surveys. These are total emissions; no burden or allocation has been made to co-products. |
| Table 2.12 | Emissions for hot pressing plywood from the South. These are total emissions; no burden or allocation has been made to co-products. |
| Table 2.13 | Production requirements1 for the 19.68 lb of phenol-formaldehyde resin neededto manufacture 1.0 MSF 3/8-in basis plywood in the South region. |
| Table 2.14 | Air emissions for the production of the 19.68 lb of phenol-formaldehyde resin needed to produce 1.0 MSF 3/8-in plywood. |
| Table 2.15 | Process emissions for plywood production from the South region. These are allocated emissions. |
| Table 2.16 | Air emission summaries for 1.0 MSF 3/8-in basis of softwood plywood from the South region. |
| Table 2.17 | Life-cycle inventory results for producing 1.0 MSF 3/8-in basis of plywood in the South region. |
| Table 2.18 | Life-cycle inventory results for 1.0 MSF 3/8-in basis plywood production from the South region. |
| Table 2.19 | Life-cycle inventory results for production of 1.0 MSF 3/8-in basis plywood in the South region. |
| Table 2.20 | Life-cycle inventory results for 1.0 MSF 3/8-in basis plywood production from the South region |
1.0 PACIFIC NORTHWEST SOFTWOOD PLYWOOD
1.1 INTRODUCTION
Softwood plywood has had a long tradition as a structural building
material for both commercial and residential construction. Plywood
is used as roof, wall and floor sheathing, and for sub-flooring
in home construction. Although plywood comes in a variety of grades
and thicknesses, its production is based on a one thousand square
feet (MSF) of 3/8-inch basis equivalence-industry refers to this
as M 3/8. Plywood is made from various species in the Pacific Northwest
region, Douglas-fir and hemlock dominate, with other species such
as spruce and western larch also used. This report focuses on production
practices in Oregon and Washington. The size of production facilities
in the region range from 50,000 to 450,000 MSF 3/8-inch annually.
This study collected data from representative plants that would
be considered in the upper portion of this range. The total annual
plywood production for the region was 4,686,000 MSF 3/8-inch (APA,
2001) in 2000, representing 27% of all U.S. plywood production and
13% of all structural panel production. The region produces enough
panels, if it were all sheathing, to build 754,000 homes annually
(NAHB, 2001-6.212 MSF sheathing per home). Panels are normally produced
in 4- x 8-foot sheets.
To conduct the survey of plywood manufacturers, five plants were
identified based on their production capability and representativeness
of the industry. All five plants provided data in terms of plywood
and co-products production, raw materials, electricity and fuel
use, and emissions. The five plywood producers surveyed represent
26% of the region's production. Total annual production from producers
surveyed was 1,233,424 MSF 3/8-inch basis.
This report documents the life cycle inventory (LCI) of manufacturing
structural plywood based on resources from the Pacific Northwest
softwood region. The output of this report will be used as an input
to the life cycle analysis (LCA) of structural building materials
by CORRIM in its cradle-to-grave analysis. This report considers
those impacts associated solely with the manufacture of softwood
plywood, documenting all inputs and outputs and their impact. Primary
data was collected through a survey of plywood manufacturers, while
secondary data was obtained for impacts associated with the manufacture
and delivery of electricity and all fuels (Franklin Associates 1991;
Pre´ Consultants, 2001; USDOE, 2000), CO2 and press
emissions (EPA, 2001), and the phenol-formaldehyde resin (Athena,
1993).
The scope of this report encompasses production of softwood plywood
from the Pacific Northwest region (Oregon and Washington) including
raw material transport to the production facility (commonly referred
to as a gate-to-gate analysis). This report is confined to transportation
of logs and resin materials to the manufacturing site, production
of phenol-formaldehyde resin, electricity, natural gas, plywood
and its co-products.
1.1.1 Unit Process Approach
The plywood process was broken down into six sub-unit processes
rather than examining the process as a "black box." The
rationale for taking this approach is that this type of model would
be useful in analyzing ways to improve efficiency, optimize operations,
and find means to reduce environmental impacts. Furthermore, data
in this format could be used as a benchmark to document process
improvements. Sub-unit processes developed for one process could
be used for modeling other processes, e.g. the peeling and drying
sub-unit processes could be used as input for green and dry veneer,
respectively, into a laminated veneer lumber (LVL) life cycle inventory
analysis (LCI). The sub-unit processes used to model softwood plywood
production are shown in Figure 1.1.
Figure 1.1 Unit process approach to the modeling of the plywood
manufacturing process.
Description of Sub-unit processes:
1. Debarking: includes debarking and bucking logs to make blocks-possible
co-products include bark and some wood waste,
2. Conditioning: heating the blocks with either hot water or steam
to condition the blocks for peeling,
3. Peeling and Clipping: blocks are peeled in the
lathe to make veneer, clipped to size, and sorted by moisture content
(which is a function of the percentage of sapwood and heartwood
in the sheet) in preparation for drying-co-products include round-up
wood, peeler cores, veneer clippings and trim
4. Veneer Drying: veneers are dried in "continuous dryers"
to 3-5% moisture content; various heat sources are used for the
drying; this center includes redrying, a practice where 10-20% of
the veneer processed through the dryer is still too wet, so it is
redried-co-products include veneer downfall and other wood waste
5. Lay-up and Pressing: veneers are coated with phenol-formaldehyde
resin and composed into panels for hot pressing; heat and pressure
are used to cure the resin, thereby bonding the veneers to make
plywood
6. Trimming and Sawing: plywood panels coming out of the press are
sawn to appropriate dimension-co-products include plywood trim and
sawdust.
Bark and some wood waste are used as fuel to fire boilers or fuel
cells to supply heat to various sub-unit processes-conditioning,
drying and hot pressing-in the manufacturing process. As such, the
bark and other wood waste when used as "hogged fuel" to
generate heat are considered within the system boundary for the
LCI analysis. Excluded from the study are the production of the
catalyst, fillers, and extenders used in resins, and the harvesting
and growth of the trees. The boiler, although not considered as
a sub-unit process, was analyzed as a separate operation within
the system boundary. Figure 1.2 provides an overview of the entire
system boundary used to model the plywood process.
Note: Not included in the sketch are the co-product flows.
Those materials considered in the LCI analysis included those listed in Table 1.1. Input materials considered were logs (includes wood and bark), green veneer, dry veneer, and phenol-formaldehyde resin. Outputs were plywood and co-products consisting of peeler core, chips, clippings, trimmings, veneer (green and dry), bark, and sawdust. All flow analyses of wood in the process were determined on an oven-dry weight basis. All bark and hogged fuel were considered green (with moisture) at 50% moisture content wet-basis. To derive the wood and bark weights and to determine how much water was "dried" from the wood and bark, the following assumptions were made: bark was at 50% moisture content (MC) on a wet-basis, the wood was at 60% MC for sapwood and 25% MC for heartwood-both on an oven-dry basis, and dry veneer and wood waste were at 7% MC on an oven-dry basis.
Table 1.1 Listing of input materials,
product, and co-products for producing plywood.
| Input Materials | Co-products Produced | Products |
|
Logs |
Bark Chips, green Peeler cores Clippings, green Veneer, dry Veneer downfall, dry Plywood trimmings, dry Sawdust, dry |
Plywood |
Delivery of the input materials was by truck. The one-way delivery distances for logs, veneer, and resin are given in Table 1.2.
Table 1.2. Pacific Northwest
delivery distance (one-way) for plywood production.
| Material |
Delivery Distance (miles)
|
| Logs (Roundwood) Veneer Resin |
60
75 122 |
The weight of the input wood was determined by using the log volume data provided by the plants in Scribner scale and converting to cubic feet (ft3) of wood using the appropriate conversion factor as given by Briggs (1994). A final conversion was then made from ft3 to mass (lb) by multiplying by the average weighted densities as determined by their percentage use as given by the survey, and the densities for these species as provided in the Wood Handbook (1987). The average wood density used was 28.84 lb/ft3 oven-dry for the mix of Douglas-fir, spruce, hemlock-fir, and western larch as given by the survey (Table 1.3).
Table 1.3 Average Density
of Wood Species Used To Calculate Mass of Wood From Logs.
| Wood Species |
Percentage
Use in Survey |
Density1
|
Weighted Average
Density |
|
%
|
lb/ft3
|
lb/ft3
|
|
| Douglas fir Spruce Hemlock-Fir Western larch |
67.6
11.6 16.8 4.0 |
30.00
21.87 28.13 32.5 |
20.28
2.54 4.73 1.30 |
| Total |
100
|
28.84
|
- The data collection, analysis, and assumptions followed protocols
as defined in "consortium for research on renewable industrial
materials (CORRIM)--research guidelines for life cycle inventories"
dated April 10, 2001. Additional considerations include:
- All data from the survey was weight averaged for the five plants
based on their production in comparison to the total production
for the year.
- Impact allocation of 100% for diesel fuel use to debarking
and bucking to address fuel use by yard log loaders.
- Impact allocation of 20% for liquid propane gas (LPG) to each
of the five sub-unit processes from Conditioning through Trimming
and Sawing for fuel use by forklift trucks within the plant.
- Density values for the wood species used to make the plywood
were obtained from Wood Handbook-Wood as an Engineering Material
(1987), and based on their weighted percentage of use as reported
by manufacturers; the weighted average density was calculated
to be 28.84 lb/ft3 oven-dry.
- Log inputs were provided in thousand board feet (Mbf) in Scribner
scale and converted to ft3
- All conversion units for forestry and forest products type
conversions were taken from Forest Products Measurements and Conversion
Factors, with special emphasis on the U.S. Pacific Northwest (Briggs
1994).
- Unaccounted wood mass of 12% was established by the difference
between reported input and output wood material flows (see Table
1.5 for material balance analysis); since there was a similar
weight difference between hogged fuel and bark, much of the difference
may have been the unaccounted for wood that was hogged for fuel.
- SimaPro5, a software package designed for analyzing the environmental impact of products during their whole life cycle, was used to perform the life cycle analysis (LCI). Developed in The Netherlands by PRé Consultants B.V., SimaPro5 contains a U.S. database for a number of materials, including paper products, fuels, and chemicals. The U.S. database is provided by Franklin Associates (FAL).
1.2 PRODUCT YIELDS
The input to produce a thousand square feet (MSF) 3/8-inch basis consists of 65.6 cubic foot (ft3) or 1,892 lb of wood from logs (based on volume and wood densities given in Table 1.3) and 21.9 lb of purchased veneer. These inputs yield 991 lb of oven-dry plywood and 383 lb of hogged fuel that is mostly if not all bark (the survey had a second category for bark where plants reported 198 lb green bark and appears to have been also included in the hogged fuel reported value). See Table 1.4 for a listing of all inputs and outputs.
Table 1.4 Inputs to produce 1.0 MSF 3/8-inch
basis of plywood in the Pacific Northwest.
| INPUTS | ||
|
|
||
| Materials1 |
Units
|
per MSF
3/8-in basis |
| Round wood
Phenol formaldehyde |
ft3
lb lb lb lb lb lb |
6.56E+01
1.89E+03 1.59E+01 8.90E+00 1.11E+00 3.30E-01 3.83E+02 |
Purchased |
||
| Dry veneer Green veneer |
lb
lb |
6.81E+00
1.51E+01 |
Electrical Use |
||
| Electricity |
kWh
|
1.39E+02
|
Fuel Use |
||
| Hog fuel (produced)3 Hog fuel (purchased)3 Wood waste Liquid propane gas Natural gas Diesel |
lb
lb lb gal ft3 gal |
3.83E+02
3.40E+01 5.00E-01 3.59E-01 1.63E+02 3.95E-01 |
1 All materials unless noted,
are given as oven-dry or solids weights
2 These materials were not included in the SimaPro LCI
analysis; excluded based on the 2% rule
3 Green weight, assumed to be 50% moisture content on
wet-basis-most if not all of this material is bark, plants reported
198 lb of green bark
A complete wood mass balance is given in the Table 1.5. Bark was
not considered in the wood flow. The percentage by weight of bark
based on the weight of wood from the processed logs was most likely
10.1% if all the hogged fuel generated within the plant was bark;
however when only the reported bark weight was considered then the
amount of bark was 5.2%. From these values it appears that most,
if not all, of the hogged fuel was bark.
The difference between the total wood input and output is 233 lb.,
which was labeled as the "unaccounted for wood." The unaccounted
for wood amounted to 12% of the total wood input, which is reasonably
close for a survey of this type. The percentage of recovery of wood
in terms of wood input as logs and output as plywood is 50.7%-defined
as the weight of wood in plywood divided by the total weight of
input wood from the logs times 100%. This is a very good efficiency
for an industry that has had to use smaller and smaller diameter
logs to produce veneer. The smaller diameter logs make it more challenging
to maintain a high recovery value.
Some of the unaccounted for wood of 233 lb may have been included
in the hogged fuel reported value. The plants reported that they
produced 383 lb of hogged fuel; however, only 198 lb of this was
specifically reported as bark from the debarking sub-unit process.
Most likely the difference is bark, but it may also include some
wood waste that had been hogged for fuel from various sub-unit processes.
Table 1.5. Wood mass balance for plywood
production from the Pacific Northwest region per 1.0 MSF 3/8-in
basis (all weights are on an oven-dry basis).
| Inputs |
lb/MSF 3/8-in basis
|
| Round wood (logs) Purchased dry veneer Purchased green veneer Total |
1,8921
7 15 1,914 |
Outputs |
lb/MSF 3/8-in basis
|
| Plywood (wood only) Wood chips Peeler core Green clippings Veneer downfall Panel trim Sawdust Wood waste (to boiler) Sold dry veneer Unaccounted for wood Total |
9712
425 46 31 3 107 10 21 67 2333 1,914 |
1 Based on Douglas fir, spruce,
hemlock and western larch weighted average wood density of 28.84
lb/ft3 for 65.6 ft3 of wood in logs to produce
MSF 3/8-inch basis.
2 Plywood (wood only) based on estimated weight of plywood,
991 lb, minus 80% of resin, filler, soda ash, and catalyst total
use.
3 12% unaccounted for wood
1.3 MANUFACTURING ENERGY SUMMARY
Energy for the production of plywood comes from electricity, diesel, liquid propane gas (LPG), bark-hogged fuel, and steam. With the recent dramatic cost increases for fuel and electricity, and the potentially for greater cost increases, this topic will attract considerable attention in the coming years as plants seek to maintain profitability. The electricity is used to operate the debarker, bucker, lathe, pneumatic and mechanical conveying equipment, fans, hydraulic pumps, saws, and a radio-frequency redryer (one plant only). Electricity was used in all processes. Diesel fuel use is assumed to be by log loaders in the "Debarking" sub-unit process. As such, all of the diesel use was assigned to this process. Forklift trucks used small amounts of LPG in one or more of the remaining five sub-unit processes. This fuel use was assigned evenly over the five sub-unit processes from "Conditioning" to "Trimming and Sawing," as such, 20% of the LPG use was assigned to each of these operations.
The source of fuel used to generate the electricity used in the manufacturing process is very important in determining the type and amount of impact in the LCI analysis. The breakdown of electricity for the Pacific Northwest by fuel source is given in Table 1.6. The source of this data is the U.S. Department of Energy (DOE). In 1998 the dominant form of fuel source in the region was hydro, representing 77.5% of the total, followed by coal at 7.8% and non-utility sources at 7.1%. In the SimaPro (LCI software) impact analysis, no impacts are associated with hydro-generated electricity; however, combusting of coal can contribute significant impact values.
Table 1.6 Electric power
industry generation of electricity by primary energy sources and
Statefor the Pacific Northwest region as defined by the U.S. Department
of Energy.
| Percentage Share, 19981 | |||
| Fuel Source |
OR
|
WA
|
Average
|
| Coal Petroleum Natural Gas Nuclear Hydro Renewable Non Utility |
9.1
0.0 1.1 6.8 77.8 0.3 4.8 |
6.5
0.1 6.8 0.0 77.2 0.0 9.4 |
7.8
0.05 4.0 3.4 77.5 0.2 7.1 |
1 Source: Energy Information Administration/State Electric Profiles 2000, Department of Energy (2000). http://www.eia.doe.gov/cneaf/electricity/st_profiles/toc.html
The distribution of electricity use by sub-unit process for the various plants was not obtained from the survey data. Rather it was extracted from data provided by the Oregon State University Energy Extension Office and a publication entitled Energy Use and Conservation in Oregon's Lumber and Wood Products Industry (Grist and Karmous, 1988) of the Oregon Department of Energy. Table 1.7 provides a breakdown of electricity use by sub-unit process. The dominant electricity use is for drying (36.7%) to operate the high velocity fans used in longitudinal, cross-flow and jet dryers (methods used to increase the heat and mass transfer rates during drying). Each of four other sub-unit processes-debarking/bucking, peeling/clipping, lay-up/pressing, and trimming/sawing-each used approximately 15% of the total electricity. Conditioning used the least amount (7%).
Table 1.7. Electricity allocation by
sub-unit process for plywood production in the Pacific Northwest.
All values are given per 1.0 MSF 3/8-inch basis of plywood.
| Sub-unit Process |
KWh
MSF 3/8-in basis |
Allocation
Percentage1 |
| Debarking & Bucking Conditioning Peeling & Clipping Drying Lay-up & Pressing Trimming & Sawing Total |
17.2
9.6 24.5 51.0 15.3 21.4 138.9 |
12.4
6.9 17.6 36.7 11.0 15.4 100 |
1 Source: Ferrari, C.J., 2000. Life Cycle Assessment: Environmental modeling of plywood and laminated veneer lumber manufacturing. Table 24, Appendix D., page 111 - Distribution of electricity use by sub-unit processes.
1.4 HOGGED FUEL UTILIZATION
All of the bark generated during debarking and other
waste sources in the plants were combined with some purchased hogged
fuel (approximately 10% of the total hogged fuel) to use as hogged
fuel in either a boiler or a direct-fired fuel cell. Hogged fuel
weight, following industry practice, was given as green weight and
assumed to be 50% moisture content on a wet-weight basis. As such
the total hogged fuel burned of 417 lb at 50% moisture content on
a wet basis, is 208.5 lb of oven-dry weight hogged fuel. A very
small amount of wood waste was burned in the boiler. In addition
to hogged fuel for heat generation, natural gas was also used, representing
7% of the total heat generation. Hogged fuel and wood waste was
by far the dominant fuel source at 90.4% of the total energy. Natural
gas represented only 9.6% of energy use. Table 1.8 provides a breakdown
of heat energy use for the boilers by fuel source.
Table 1.8. Pacific Northwest weighted
data conversion of boiler inputs into heat energy for 1.0 MSF 3/8-in
basis of plywood.
| Fuel Type |
Input
|
Heat Energy
BTU |
Allocation
% |
|||
|
Total
|
Total
|
Total
|
||||
| Hogged Fuel (lb) |
416.71
|
1,256,3512
|
90.34
|
|||
| Self generated |
382.7
|
1,153,841
|
91.84
|
|||
| Purchased |
34.0
|
102,510
|
8.16
|
|||
| Wood Waste (lb) |
0.5
|
1,5023
|
0.11
|
|||
| Natural Gas (ft3) |
163.4
|
132,8124
|
9.55
|
|||
| Total |
1,390,665
|
100
|
||||
1 Weight of green hogged fuel
(assumed 50% MC wet-basis)
2 Weight of green hogged bark multiplied by 4500 BTU/lb
of green bark multiplied by 67% efficiency
3 Weight of green wood waste multiplied by 4500 BTU/lb
of green wood multiplied by 67% efficiency
4 Volume of natural gas multiplied by 1016 BTU/ft3 of
natural gas, 80% efficiency-source Athena
Three sub-unit processes used hogged fuel and natural gas for heat block conditioning, veneer drying, and hot pressing. Veneer drying used the dominant amount (73%) of energy for heating, followed by hot pressing (14%) and conditioning (12%). The plants reported heat use for drying and pressing. To determine heat use for conditioning it was calculated by taking the total heat use for the plant (as determined by hogged and wood waste fuel used in the boiler to generate steam) and subtracting the reported steam use for drying and hot pressing. In summary, dryers used the dominant amount of electricity (36.7%) and energy (73%) compared to the total use for the three production centers. Table 1.9 provides a breakdown of heat use by sub-unit process and source.
Table 1.9. Boiler energy
requirements for conditioning, drying, and pressing sub-unit processes
used in plywood production for the Pacific Northwest.
| Heat energy use per MSF 3/8-inch basis plywood | |||||
| Fuel Inputs |
Conditioning
BTU |
Drying
BTU |
Pressing
BTU |
Total
BTU |
Percent
% |
| Hogged Fuel Wood Waste Natural Gas Total Percent % |
127,896.5
152.9 13,520.3 141,569.7 10 |
949,675.7
1,135.4 100,392.6 1,051,203.7 76 |
178,778.7
213.7 18,899.1 197,891.6 14 |
1,256,351
1,502 132,812 1,390,665 100 |
90.3 |
Boiler data in the LCI was determined by calculating the BTU energy equivalence of the two fuel sources of hogged fuel and natural gas, then entering this data into either a specially written boiler module for hogged fuel generated within the plant or the Franklin Database natural gas boiler, respectively. The boiler module written for hogged fuel used only Franklin Associates (FAL) data for wood boiler emissions and did not include a transportation burden for the delivery of hogged fuel to the plant. However, when hogged fuel was purchased, the wood boiler FAL database was used, which included a transportation burden for its delivery. The natural gas fired boiler used the FAL database that included a transportation burden to the plant. For all fuel whether wood, hogged fuel, or natural gas, emissions from the FAL database in the LCI analysis were used. Table 1.10 provides a comparison of emissions as generated by the FAL database to that of the data collected by the survey. All survey data, except for CO2, was provided by the survey; CO2 was calculated from EPA data on boiler emissions (EPA, 1999). Although the emissions data for FAL and the CORRIM survey are similar in magnitude, there are differences. The likely difference between the FAL data and survey/EPA data is due to several factors. First, the FAL data represents all wood-fired boilers throughout the U.S. and does not consider wood species or regional effects on the values. Secondly, the FAL database is based upon a much larger database. Consideration should be given to establishing a new database for hogged-fuel fired boilers based on the CORRIM survey data. The CORRIM database could include boiler data from other modules for softwood plywood, softwood lumber, and OSB.
Table 1.10. Survey data on air emissions
for boilers as output from SimaPro 5 (using the FAL1
boiler data) compared to survey data. Total emissions from dryer;
no allocations to co-products.
| Air Emissions |
FAL Data
lb / MSF of Plywood |
CORRIM Survey Data
lb/ MSF of Plywood |
| Acetaldehyde Acetone Acrolein As Ba Benzene Cl2 CO CO2 (non fossil) Dust (PM10) Formaldehyde Methanol Naphthalene NOx Organic substances Particulates Phenol Propionaldehyde SOx VOC Zn |
6.30E-04
N/R N/R 1.85E-05 9.24E-04 7.56E-04 1.64E-03 2.86E+00 4.41E+02 N/R 1.39E-03 N/R 5.04E-04 3.15E-01 3.49E-02 3.57E-02 8.40E-03 N/R 1.60E-02 N/R 9.24E-04 |
N/R
N/R 1.50E-06 N/R N/R N/R N/R 4.79E+00 3.76E+023 4.36E-01 N/R 2.91E-04 N/R 8.10E-01 N/R 5.39E-01 N/R 4.61E-03 N/R 3.18E-01 0.00E+00 |
1 Reference:
SimaPro 5.0, 2001; Franklin Associates, FAL Database, 1998
2 N/R= Not reported in surveys
3 Calculated from EPA Wood Waste Combustion in Boilers,
AP-42, Section 1.6, EPA, 1999
1.5 DRYING EMISSIONS FOR PNW PLYWOOD PRODUCTION
Dryers are used to take the moisture content of green veneer from about 25-60% to 3-6% (oven-dry basis). Dryer temperatures are normally in the 300 to 365oF range; however, the wood veneer does not experience this higher temperature until much of its moisture is evaporated near the end of the dryer. Most emissions are generated at this time. One of the plants surveyed had a direct-fired natural gas dryer, and because of this, the emissions reported have components of CO, CO2 (fossil), NOx, and SO2 that would not be emitted from the steam heated dryers.
Table 1.11. Emissions for drying plywood
from the Pacific Northwest as reported in surveys. Total emissions
from dryer; no allocations to co-products.
| Air Emission1 |
Unit
|
Emissions from dryer
per MSF 3/8-in basis |
| Acetaldehyde Acrolein CO CO2 (fossil)2 Dust (PM10) Formaldehyde Methanol NOx Particulates Phenol SO2 VOC |
lb
lb lb lb lb lb lb lb lb lb lb lb |
1.04E-02
6.69E-07 1.50E-01 2.71E+00 2.66E-01 2.12E-02 3.26E-02 4.99E-02 3.00E-01 2.61E-03 1.10E-03 5.96E-01 |
1 Air emission data as reported from
surveys
2 Calculated from EPA Plywood Manufacturing - Emission
Factor Documentation, AP-42, Chapter 10, Table 10.5-2, 2001
1.6 PRESSING EMISSIONS FOR PNW PLYWOOD PRODUCTION
Hot pressing is done in the plywood process to provide intimate
contact between veneers while the phenol-formaldehyde adhesive cures
as a result of temperature in the 325-340oF range. Emissions are
generated from the wood as a result of the high temperatures and
the adhesive curing.
Table 1.12. Emissions for hot pressing
plywood from the Pacific Northwest. Total emissions from press;
no allocations to co-products
| Air Emission |
Unit
|
Emissions from dryer
per MSF 3/8-in basis1 |
| Acetaldehyde Acetone Alpha-pinene Beta-pinene Formaldehyde Methanol Methyl ethyl ketone Methyl isobutyl ketone Particulates Phenol THC as carbon VOC |
lb
lb lb lb lb lb lb lb lb lb lb lb |
4.19E-03
6.50E-03 9.80E-02 3.80E-02 1.90E-03 1.39E-01 8.70E-04 7.10E-04 1.20E-01 1.39E-03 2.10E-01 2.49E-01 |
1 Calculated from EPA Plywood Manufacturing - Emission Factor Documentation, AP-42, Chapter 10, Table 10.5-6, 2001
1.7 ADHESIVE USAGE AND ENERGY/ELECTRICITY TO PRODUCE
Phenol-formaldehyde (phenolic) resin is the adhesive used in plywood production. The manufacture of phenolic resins is particularly energy intensive. The total energy requirement for the production 15.88 lb of phenolic needed for MSF 3/8-in basis plywood from the Pacific Northwest is 1.94E+05 BTU's. Electricity requirements for phenol-formaldehyde production per MSF 3/8-in basis are 7% of the total electricity used to produce plywood in the Pacific Northwest region. The15.88 lb of phenol-formaldehyde resin is comprised of 65% formaldehyde and 35% phenol by weight. All the materials, fuel, and electricity used to produce the phenol-formaldehyde resin are listed in Table 1.13. Total air emissions for the production of the 15.88 lb of phenol-formaldehyde resin are given in Table 1.14.
Table 1.13. Production requirements1
for the 15.88 lb of phenol-formaldehyde resin needed to manufacture
1.0 MSF 3/8-in basis plywood from the Pacific Northwest.
| INPUTS | ||
|
|
||
Materials |
Units
|
per MSF 3/8-in basis
|
| Formaldehyde Phenol |
lb
lb |
1.03E+01
5.56E+00 |
Fuel Use |
||
| Heavy oil Gasoline +Natural gas |
BTU
BTU BTU |
9.91E+03
6.83E+01 1.84E+05 |
Electricity Use |
||
| Electricity |
kWh
|
1.02E+01
|
1 Data obtained from Material, Energy & Environmental Unit Factor Emissions: Structural Wood Production, Athena, 1993.
| Air Emission |
Emissions per MSF 3/8-in basis
|
||
|
PF Resin
Production1 |
Total for Plywood
Production2 |
PF Resin Contribution to
Total for Plywood Production |
|
|
lb
|
lb
|
%
|
|
| Acetaldehyde Acetone Acrolein Benzene1 CO CO2 (fossil) CO2 (non-fossil) Cumene1 Dust (PM10) Formaldehyde Methane Methanol Non methane VOC NOx Particulates Phenol1 SO2 SOx VOC |
0.00E+00
0.00E+00 9.87E-09 8.24E-06 7.44E-02 2.08E+01 4.22E-03 6.98E-05 0.00E+00 1.59E-02 5.17E-02 0.00E+00 1.69E-01 2.94E-01 3.89E-03 2.04E-02 0.00E+00 2.69E-01 0.00E+00 |
1.13E-02
4.81E-03 5.95E-07 5.16E-04 2.15E+00 4.69E+01 2.96E+02 6.98E-05 2.09E-01 3.54E-02 1.03E-01 1.28E-01 2.49E-01 7.10E-01 3.70E-01 2.90E-02 7.78E-04 5.33E-01 6.27E-01 |
0.00
0.00 1.66 1.60 3.46 44.38 0.00 100.00 0.00 44.82 50.19 0.00 68.13 41.47 1.05 70.31 0.00 50.37 0.00 |
1 Data
obtained from Material, Energy & Environmental Unit Factor Emissions:
Structural Wood Production, Athena, 1993.
2 Includes all emissions for plywood production, plus
those emissions associated with the production and delivery of electricity,
fuel, and adhesive.
1.8 PROCESS RELATED EMISSIONS
The total emissions from each sub-unit process can also be determined. Table 1.15 gives the emissions breakdown for the six sub-unit processes. The values include the burdens in terms of emissions for the production of any electricity, fuel, and adhesive, in addition to that of the hogged fuel and wood. The total values for Tables 15, 16, and 18 differ slightly due to rounding error as the values were accumulated from sub-unit process to sub-unit process. The allocation of all emissions to plywood was 51.1%; as such, to find total emissions, divide the emissions allocated to plywood by 0.511. The reminder of emissions (48.9%) was assigned to the co-products.
Table 1.15. Process emissions for plywood
production from the Pacific Northwest region. Includes emissions
for the production and delivery of electricity, fuel, and adhesive.
| Air Emission |
Emissions per MSF 3/8-in basis plywood
|
||||||
|
Debarking
|
Conditioning
|
Peeling and
Clipping |
Veneer
Drying |
Lay-up and
Pressing |
Trimming
and Sawing |
||
|
lb
|
lb
|
lb
|
lb
|
lb
|
lb
|
TOTAL
|
|
| Acetaldehyde Acetone Acrolein Alpha-pinene Benzene Beta-pinene CO |
0.00E+00
0.00E+00 1.79E-08 0.00E+00 2.17E-08 0.00E+00 4.33E-02 |
6.22E-05
0.00E+00 9.55E-09 0.00E+00 7.47E-05 0.00E+00 2.88E-01 |
0.00E+00
0.00E+00 1.69E-08 0.00E+00 0.00E+00 0.00E+00 0.00E+00 |
1.09E-02
0.00E+00 7.17E-07 0.00E+00 5.27E-04 0.00E+00 2.17E+00 |
4.36E-03
6.50E-03 3.22E-08 0.00E+00 1.18E-04 0.00E+00 5.09E-01 |
0.00E+00
0.00E+00 1.49E-08 0.00E+00 0.00E+00 0.00E+00 0.00E+00 |
1.13E-02
4.80E-03 5.90E-07 0.00E+00 5.15E-04 0.00E+00 2.15E+00 |
| CO2 (fossil) |
1.13E+01
|
2.59E+00
|
1.42E-03
|
1.87E+01
|
3.19E+01
|
1.31E+00
|
4.55E+01
|
| CO2 (non-fossil) |
2.84E-03
|
4.37E+01
|
0.00E+00
|
3.08E+02
|
6.30E+01
|
0.00E+00
|
2.97E+02
|
| Cumene Dust (PM10) Formaldehyde Methane Methanol Methyl ethyl ketone |
0.00E+00
0.00E+00 2.74E-03 4.52E-03 0.00E+00 0.00E+00 |
0.00E+00
0.00E+00 1.32E-04 6.82E-03 0.00E+00 0.00E+00 |
0.00E+00
4.80E-03 0.00E+00 3.22E-03 0.00E+00 0.00E+00 |
0.00E+00
2.67E-01 2.22E-02 4.38E-02 3.26E-02 0.00E+00 |
9.43E-05
1.34E-03 2.36E-02 8.05E-02 1.40E-01 8.70E-04 |
0.00E+00
6.94E-03 0.00E+00 2.97E-03 0.00E+00 0.00E+00 |
6.97E-05
2.07E-01 3.53E-02 1.02E-01 1.28E-01 6.43E-0 |
| Methyl isobutyl | |||||||
| ketone Non methane VOC |
0.00E+00
3.55E-02 |
0.00E+00
1.00E-02 |
0.00E+00
3.05E-03 |
0.00E+00
5.57E-02 |
7.10E-04
1.00E-03 |
0.00E+00
2.97E-03 |
5.25E-04
6.97E-02 |
| NOx |
1.91E-01
|
4.16E-02
|
5.55E-03
|
3.29E-01
|
4.57E-01
|
5.06E-03
|
7.08E-01
|
| Particulates Phenol |
1.51E-02
8.53E-08 |
4.54E-03
8.30E-04 |
1.11E-02
0.00E+00 |
3.30E-01
8.48E-03 |
1.34E-01
3.02E-02 |
9.91E-03
0.00E+00 |
3.68E-01
2.90E-02 |
| SO2 |
0.00E+00
|
0.00E+00
|
0.00E+00
|
1.05E-03
|
5.36E-06
|
0.00E+00
|
7.77E-04
|
| SOx |
3.31E-02
|
3.55E-02
|
1.22E-02
|
2.32E-01
|
4.15E-01
|
1.09E-02
|
5.31E-0
|
| THC as carbon VOC |
0.00E+00
0.00E+00 |
0.00E+00
0.00E+00 |
0.00E+00
0.00E+00 |
0.00E+00
5.96E-01 |
0.00E+00
2.52E-01 |
0.00E+00
0.00E+00 |
0.00E+00
6.26E-01 |
1.9 AIR EMISSION SUMMARY FOR PLYWOOD PRODUCED IN THE PACIFIC NORTHWEST
The total air emissions for producing 1.0 MSF 3/8-in basis of plywood are allocated (the burden is assigned) based on the weight fraction of plywood to the total weight of plywood and co-products, and their assignment at each sub-unit process as the materials progress through the manufacturing process. Table 1.16 gives a summary of the emissions. The allocation for plywood is 51.1%.