Life-Cycle Assessment of Redwood Decking in the United States 

with a Comparison to Three Other Decking Materials

Final Report

By

CORRIM

The Consortium for Research on Renewable Industrial Materials

P.O. Box 352100

Seattle, WA 98195-2100

With participation from member organizations and affiliates including: 

U.S. Forest Service Forest Products Laboratory

Madison, Wisconsin 

Represented by Richard D. Bergman

Vice President-Solid and Engineered Wood Products, CORRIM

and

School of Environmental and Forest Sciences, University of Washington

Represented by Ivan L. Eastin

Director and Professor, Center for International Trade in Forest Products (CINTRAFOR) and 

Vice President–Marketing, CORRIM

and 

Elaine Oneil 

Executive Director, CORRIM

and

Humboldt State University, Department of Forestry and Wildland Resources

Represented by Han-Sup Han

Professor of Forest Operations and Engineering

July 31, 2013
i

Executive Summary

Study Goals 

The goal of the study was to conduct a life-cycle inventory (LCI) of California redwood 

(Sequoia sempervirens) decking that would quantify the critical environmental impacts of 

decking from cradle to grave. Using that LCI data, a life-cycle assessment (LCA) was produced 

for redwood decking. The results were used to compare the environmental footprint of redwood 

decking to other decking materials that serve an equivalent function. The other materials 

examined include plastic (cellular PVC) and wood–plastic composites (WPCs) with recycled 

content varying from 0% and 100%.

Methodology 

The environmental impacts were determined using LCA techniques conducted to ISO 14040 and 

14044 standards. System boundaries delineated the life cycle covered from extraction through 

product production and maintenance to disposal of old decking into a landfill with standard 

methane capture equipment for energy recovery. The present study chose the functional unit as 

100 square feet (9.29 m2) of installed decking in service for 25 years. Twenty-five years is the 

expected service life of all decking materials. TRACI 2.1 method found in SimaPro 7 modeled 

the life-cycle impact assessment (LCIA) per functional unit. Softwood shavings used in making 

WPC decking products left the sawmill with no environmental burdens assigned to them. The 

biogenic methane captured from the landfill avoided natural gas production.

Impact Measures 

Impact categories include global warming potential (GWP) (kg CO2-eq), acidification potential 

(kg SO2-eq), respiratory effects (PM 2.5-eq), eutrophication potential (kg N-eq), ozone depletion 

(kg CFC-11-eq), and smog potential (kg O3-eq). Other impact measures included cumulative 

(total) energy demand (primary energy) (MJ-eq), including both the biomass and fossil fuel 

contributions, were calculated and reported directly from LCI flows. The present study also 

tracked fresh water consumption (in L) and renewable and non-renewable material resource 

consumption (non-fuel resources). Impact categories and other impact measures were reported

per 100 ft2(9.29 m2) and per m3. Carbon stored in the decking was accounted for in GWP.

Key Findings 

The following table shows the LCIA per functional unit for PVC (156 kg), virgin WPC (266 kg), 

recycled WPC (266 kg) and redwood (135 oven-dried kg). PVC and both WPC decking products 

assumed a 2.3% loss, whereas redwood decking assumed a 3% loss over their whole life cycle.

For two reasons, global warming potential (GWP) for redwood (–163 kg CO2-eq) was negative.

One, the carbon sequestered in the trees that are used as raw material for the redwood decking, 

continued to be stored in the decking while in use (–262 kg CO2-eq). Secondly, redwood decking 

consumed little energy for drying, which is usually the most energy-intensive process for wood 

products. Even though the two WPC decking materials stored carbon as a final product (50% by 

weight) as well, all six key impact categories were still substantially higher in value for the 

alternative decking materials than for redwood decking. Biomass energy consumption was 

higher for redwood decking than for the alternatives, as expected, because wood product 

production typically utilizes the wood residue generated during production as a fuel source. 

However, total energy for redwood was substantially lower than the other decking products:

4.2% (447/10640) of PVC, 3.0% (447/14700) of virgin WPC and 6.7% (447/6690) of recycled 
ii

WPC. The volume of captured biogenic methane from decomposing redwood decking in 

landfills to avoid natural gas production was 11.3 m3/100 ft2, approximately 433 MJ/100 ft2of 

energy.

Life-cycle impact assessment for four decking products by value per 100 ft2(9.29 m2)

Impact category Unit

Polyvinyl

chloride

Virgin wood–

plastic composite

Recycled wood–

plastic

composite Redwood

Global warming kg CO2 eq 426 264 144 –163

Ozone depletion kg CFC-11 

eq

1.60E-05 1.37E-05 1.16E-05 1.36E-06

Smog kg O3 eq 30.0 36.3 28.5 9.5

Acidification kg SO2 eq 4.61 5.94 2.86 0.21

Eutrophication kg N eq 0.108 0.237 0.203 0.022

Respiratory effects kg PM2.5 eq 0.276 0.338 0.157 0.006

Primary energy consumption Unit

Non-renewable fossil MJ 10169 13840 5820 280

Non-renewable nuclear MJ 449 238 168 39

Renewable (solar, wind, 

hydroelectric, and geothermal) MJ 15 614 693 35

Renewable, biomass MJ 6 9 9 94

Total primary energy MJ 10600 14700 6690 447

Material resources 

consumption1 Unit

Non-renewable materials kg 157 134 134 0.8

Renewable materials kg 0 133 133 136

Fresh water L 4500 3360 3440 229

Waste generated Unit

Solid waste kg 0.736 0.070 8.60 0.223

1 Non-fuel resources.

Kiln-drying is the most energy-intensive activity for making most wood products. However, in 

this respect, redwood decking is different because of the amount that sold green or first air-dried 

before being kiln-dried. Approximately 36% of redwood decking was sold green, with the 

remaining 64% being air-dried. After air-drying to less than 30% moisture content, 57% of the 

decking is further dried in the kiln so that 36.6% of total redwood decking leaves the mill as a 

kiln-dried product. Therefore, minimal kiln-drying resulted in a redwood decking product 

comparable on an energy-consumption basis to structural Douglas-fir (Pseudotsuga menziesii) 

that is sold and installed green.

The following figure illustrates the relative differences between the critical environmental 

impacts associated with the four decking materials per functional unit.
iii

Life-cycle impact assessment for the four decking products by percentage per 100 ft2(9.29 m2)

Interpretation 

Redwood decking had considerably lower values for the six key impact categories, compared to 

the other three decking materials. The low GWP ranking for redwood decking was the result of 

the product’s ability to store carbon, originally sequestered from the atmosphere, over the life of 

the product. The LCIA incorporated carbon stored in all decking products through sequestration 

including WPC decking. Biogenic carbon dioxide emissions were not considered but biogenic 

methane emissions were in the LCIA to be consistent with the TRACI method. Additionally, the 

present study considered that 96% of the carbon in the wood residues generated during decking 

production was emitted to the atmosphere as biogenic carbon dioxide. Whereas the remainder 

(4%) was stored in a new product separate from redwood decking.

As indicated by the six impact categories, producing recycled WPC had substantial 

environmental advantages over using virgin WPC. All six key impact categories were lower for 

recycled WPC than for virgin WPC. The negative environmental impact for recycled WPC

compared to virgin WPC was solid waste generated during the cradle-to-gate production of 

recycled WPC.

The other impact measures indicated the high consumption of both non-renewable and renewable 

material resources in the virgin and recycled WPC decking products. WPC decking products are 

-40%

-30%

-20%

-10%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Polyvinyl chloride Virgin wood plastic

composite

Recycled wood plastic

composite

Redwood

Global warming Ozone depletion

Smog Acidification

Eutrophication Respiratory effects

Non-renewable fossil Non-renewable nuclear

Renewable (solar, wind, hydroelectric, and geothermal) Renewable, biomass

Total primary energy Non-renewable materials

Renewable materials Fresh water

Solid Waste
iv

made of 50% polyethylene resins and 50% wood. In addition, WPC decking products are 

substantially denser than the other decking products; therefore, the two WPC decking products 

consume roughly the same as PVC in the non-renewable resource category and redwood decking 

in the renewable resource category.

Sensitivity Analysis 

The present study conducted a sensitivity analysis to determine the environmental impacts 

assigned to the final product. For the base case, the present study allocated no environmental 

impacts to the co-products or by-products. Instead, all burdens were assigned to the final product 

(no allocation). To evaluate the decision, a sensitivity analysis was conducted assuming mass 

allocation. Redwood decking was the only decking product that had other co-products associated 

with its production such as green and dry wood residues. 

All six impacts for redwood decking were lower for the mass allocation than the base case. The 

impacts for the other three decking materials stayed the same. Because of mass allocation, GWP 

for redwood decking was slightly more negative (–175 kg CO2-eq) compared to no allocation 

conducted (–163 kg CO2-eq). GWP for redwood decking was lower for the mass allocation 

scenario primarily because the green wood residues were allocated a portion, about 40% of the 

environmental impacts originally assigned to the redwood decking in the base case scenario. The 

following table shows the LCIA per functional unit for mass allocation.

Life-cycle impact assessment for four decking products per 100 ft2(9.29 m2) (Mass 

allocation)

Impact category Unit

Polyvinyl

chloride

Virgin wood–plastic

composite

Recycled wood–

plastic composite Redwood

Global warming kg CO2 eq 426 264 144 –175

Ozone depletion kg CFC-11 eq 1.60E-05 1.37E-05 1.16E-05 1.25E-06

Smog kg O3 eq 30.0 36.3 28.5 6.7

Acidification kg SO2 eq 4.61 5.94 2.86 0.09

Eutrophication kg N eq 0.108 0.237 0.203 0.016

Respiratory effects kg PM2.5 eq 0.276 0.338 0.157 0.001

Primary energy consumption Unit

Non-renewable fossil MJ 10169 13836 5823 95

Non-renewable nuclear MJ 449 238 168 27

Renewable (solar, wind, 

hydroelectric, and geothermal) MJ 15 614 693 24

Renewable, biomass MJ 6 9 9 86

Total primary energy MJ 10600 14700 6690 232

Material resources consumption1 Unit

Non-renewable materials kg 157 134 134 1

Renewable materials kg 0 133 133 138

Fresh water L 4500 3350 3430 189

Waste generated Unit

Solid waste kg 0.736 0.070 8.60 0.220

1 Non-fuel resources.

Recommendations 

As shown by its negative GWP, the amount of carbon stored in redwood decking exceeded the 

total GHG emissions emitted during its whole life cycle. Other wood building products and 
v

wood composites have this significant environmental advantage of storing carbon while in use to

offset the impacts from production. The uptake of carbon dioxide from the atmosphere into the 

raw materials (i.e., trees) used to make wood products and the storage of the resultant carbon in a

long-lived product is a significant environmental benefit.

The substantially lower rankings across all six critical impact categories for redwood decking 

quantify its lower environmental footprint relative to alternative decking materials. Other lifecycle studies have shown similar results for wood products.

Acknowledgments

We gratefully acknowledge the financial assistance for this research project provided by the 

California Redwood Association. A special thank you to the following people for their technical 

assistance: James Salazar (ATHENA), Craig Clemons (USDA FS Forest Products Laboratory), 

Chris Bolin (AquAeTer, Inc.), Tim Goertemiller (Milacron), and Lal Mahalle (FPInnovations). 
vi

Table of Contents

Executive Summary......................................................................................................................... i

Study Goals.................................................................................................................................. i

Methodology................................................................................................................................ i

Impact Measures.......................................................................................................................... i

Key Findings................................................................................................................................ i

Interpretation..............................................................................................................................iii

Sensitivity Analysis ................................................................................................................... iv

Recommendations...................................................................................................................... iv

Acknowledgments........................................................................................................................... v

1 Introduction............................................................................................................................. 1

1.1 Background ...................................................................................................................... 1

1.2 Significance...................................................................................................................... 3

2 Goal of the study..................................................................................................................... 3

3 Methodology........................................................................................................................... 4

3.1 Scope of the Study............................................................................................................ 4

3.2 Functional Unit................................................................................................................. 4

3.3 System Boundary ............................................................................................................. 5

3.4 Allocation Procedures...................................................................................................... 6

3.5 Decking ............................................................................................................................ 7

3.5.1 Plastic (PVC) ............................................................................................................ 7

3.5.2 Wood–plastic Composites (WPC)............................................................................ 8

3.5.3 Redwood ................................................................................................................. 10

3.6 Life-Cycle Impact Assessment Methodology and Types of Impacts ............................ 11

3.7 Interpretation .................................................................................................................. 11

3.8 Assumptions................................................................................................................... 11

3.9 Value Choices and Optional Elements........................................................................... 12

3.10 Limitations.................................................................................................................. 12

3.10.1 Omissions of life-cycle stages, processes, input or output flows ........................... 12

3.10.2 Decision Criteria (cut-off rule, if applicable) ......................................................... 12

3.11 Data Quality Requirements ........................................................................................ 12

3.12 Peer Review................................................................................................................ 13

3.13 Electrical Grids........................................................................................................... 13

4 Cradle-to-Gate Life-Cycle Inventory Data ........................................................................... 14

4.1 Polyvinyl Chloride ......................................................................................................... 14

4.2 Wood–plastic Composite (virgin and recycled)............................................................. 15

4.2.1 Raw Material Preparation ....................................................................................... 15

4.2.2 Wood–plastic Composite Processing...................................................................... 17

4.2.3 Process Energy........................................................................................................ 17

4.3 Redwood......................................................................................................................... 18

4.3.1 Forest Resources..................................................................................................... 18

4.3.2 Resource Transportation ......................................................................................... 24

4.3.3 Product Production.................................................................................................. 24

5 Data Quality Summary ......................................................................................................... 28

6 Installation and Use Phase Life-Cycle Inventories............................................................... 28
vii

6.1 Polyvinyl Chloride ......................................................................................................... 29

6.1.1 Transport................................................................................................................. 29

6.1.2 Use Phase Inputs..................................................................................................... 29

6.2 Wood–Plastic Composite (virgin and recycled)............................................................. 30

6.2.1 Transport................................................................................................................. 30

6.2.2 Use Phase Inputs..................................................................................................... 30

6.3 Redwood......................................................................................................................... 30

6.3.1 Transport................................................................................................................. 30

6.3.2 Use Phase Inputs..................................................................................................... 30

7 End of life Phase ................................................................................................................... 31

8 Life-Cycle Impact Assessment ............................................................................................. 32

8.1 PVC Decking.................................................................................................................. 32

8.2 WPC Decking................................................................................................................. 35

8.2.1 Virgin Wood–plastic Composite Decking .............................................................. 36

8.2.2 Recycled WPC Decking ......................................................................................... 38

8.3 Redwood Decking.......................................................................................................... 41

8.4 Overall LCIA – All Decking Products........................................................................... 45

9 Sensitivity analysis—Mass Allocation ................................................................................. 48

10 Cradle-to-Gate Redwood Decking – Mass Allocation ......................................................... 52

Scenario Analyses: end-of-life values from EPA (2006) data...................................................... 54

11 Conclusions and Recommendations..................................................................................... 58

12 References............................................................................................................................. 58

13 Appendix: Forest Resources Module Survey ....................................................................... 63

14 Appendix: Product Manufacturing Module Survey.............................................................. 80

15 Appendix: Landfill Gas Equations........................................................................................ 91

Table of Figures

Figure 1-1: Complete life cycle from regeneration of trees to disposal of wood materials (Based 

on Fava et al. 1994)......................................................................................................................... 2

Figure 1-2: Life-cycle assessment phases....................................................................................... 2

Figure 3-1: Shaded region shows area of redwood decking production......................................... 4

Figure 3-2: System boundary for decking from cradle-to-grave. ................................................... 6

Figure 3-3: Diagram showing the wood flow through the production center (i.e., sawmill). ........ 7

Figure 3-4: Cradle-to-gate manufacturing process diagram for cellular PVC decking (Mahalle 

and O’Connor 2009). ...................................................................................................................... 8

Figure 3-5: Cradle-to-gate manufacturing process diagram for virgin WPC decking (Mahalle and 

O’Connor 2009).............................................................................................................................. 9

Figure 3-6: Cradle-to-gate manufacturing process diagram for recycled WPC decking (Mahalle 

and O’Connor 2009). ...................................................................................................................... 9

Figure 3-7: Cradle-to-gate wood decking manufacturing (Puettmann et al. 2010). ..................... 10

Figure 4-1: Stages of processing for LDPE bags (Climenhage 2003).......................................... 17

Figure 4-2: Redwood forest operations producing saw logs and biomass.................................... 20

Figure 8-1: Life-cycle impact assessment for the four decking products by percentage.............. 45

Figure 9-1: Life-cycle impact assessment for four decking products by percentage per 100 ft2

(9.29 m2) (Mass allocation)........................................................................................................... 49
viii

Figure 11-1: Life-cycle impact assessment for all decking by percentage (EPA 2006)............... 55

Table of Tables

Table 3-1: Reference flows for redwood, polyvinyl, and wood–plastic composite decking.......... 5

Table 3-2: Regional grids in SimaPro for decking production ..................................................... 14

Table 4-1: Resource list for manufacturing one metric ton of polyvinyl chloride decking (Lippiatt 

2007; Mahalle and O’Connor 2009)............................................................................................. 14

Table 4-2: Energy resources required to produce one metric ton of PVC decking (Lippiatt 2007; 

Mahalle and O’Connor 2009)....................................................................................................... 15

Table 4-3: Resource list for manufacturing one metric ton of wood–plastic composite decking 

(Mahalle and O’Connor 2009)...................................................................................................... 15

Table 4-4: Ancillary list for producing one metric ton of virgin wood–plastic composite decking 

(Mahalle and O’Connor 2009)...................................................................................................... 15

Table 4-5: Electrical energy consumed for the two main unit processes ..................................... 18

Table 4-6: Assumptions and input values used for the environmental impact analysis of redwood 

forest1resources management1..................................................................................................... 19

Table 4-7: Fertilization rates to grow coast redwood two-year old seedlings.............................. 19

Table 4-8: Fuel and lubrication consumption rate for tree planting and pre-commercial thinning

....................................................................................................................................................... 19

Table 4-9: Hourly productivity and fuel and lubricant use of redwood harvesting systems1....... 21

Table 4-10: Mass balance of manufacturing redwood decking.................................................... 25

Table 4-11: Carbon balance of redwood decking......................................................................... 26

Table 4-12: Material and energy consumed on-site to produce redwood decking (SimaPro input 

values). Includes fuel used for electricity production and for log and transportation (unallocated)

....................................................................................................................................................... 27

Table 4-13: List of ancillary materials consumed during manufacturing..................................... 27

Table 5-1: Data quality summary for cradle-to-gate data............................................................. 28

Table 6-1: Installation guidelines for the various decking materials............................................ 29

Table 7-1: GHG emissions from wood landfilled with standard methane capture....................... 31

Table 8-1: Life-cycle impact assessment for 100 ft2(9.29 m2) of polyvinyl chloride decking.... 33

Table 8-2: Life-cycle impact assessment for 1 m3of polyvinyl chloride decking ....................... 34

Table 8-3: Environmental performance of 100 ft2(9.29 m2) of polyvinyl chloride decking from 

cradle-to-gate ................................................................................................................................ 35

Table 8-4: Environmental performance of 1 m3of polyvinyl chloride decking from cradle-to-gate

....................................................................................................................................................... 35

Table 8-5: Life-cycle impact assessment for 100 ft2(9.29 m2) of virgin wood–plastic composite 

decking.......................................................................................................................................... 37

Table 8-6: Life-cycle impact assessment for one m3of virgin wood–plastic composite decking 37

Table 8-7: Environmental performance of 100 ft2(9.29 m2) of virgin wood–plastic composite 

decking from cradle-to-gate.......................................................................................................... 38

Table 8-8: Environmental performance of 1 m3of virgin wood–plastic composite decking from 

cradle-to-gate ................................................................................................................................ 38

Table 8-9: Life-cycle impact assessment for 100 ft2(9.29 m2) of recycled wood–plastic 

composite decking ........................................................................................................................ 39
ix

Table 8-10: Life-cycle impact assessment for one m3of recycled wood–plastic composite 

decking.......................................................................................................................................... 40

Table 8-11: Environmental performance of 100 ft2(9.29 m2) of recycled wood–plastic composite 

decking from cradle-to-gate.......................................................................................................... 41

Table 8-12: Environmental performance of 1 m3of recycled wood–plastic composite decking 

from cradle-to-gate........................................................................................................................ 41

Table 8-13: Life-cycle impact assessment for 100 ft2(9.29 m2) of redwood decking ................. 43

Table 8-14: Life-cycle impact assessment for one m3of redwood decking ................................. 43

Table 8-15: Environmental performance of 100 ft2(9.29 m2) of redwood decking from cradle-togate................................................................................................................................................ 44

Table 8-16: Environmental performance of 1 m3of redwood decking from cradle-to-gate ........ 44

Table 8-17: Life-cycle impact assessment for four decking products by percentage per 100 ft2

(9.29 m2) ....................................................................................................................................... 46

Table 8-18: Life-cycle impact assessment for four decking products by value per 100 ft2(9.29 

m

2

)................................................................................................................................................. 47

Table 8-19: Life-cycle impact assessment for four decking products by value per m3................ 48

Table 9-1: Life-cycle impact assessment for four decking products by percentage per 100 ft2

(9.29 m2) (Mass allocation)........................................................................................................... 50

Table 9-2: Life-cycle impact assessment for four decking products per 100 ft2(9.29 m2) (Mass 

allocation) ..................................................................................................................................... 51

Table 9-3: Life-cycle impact assessment for four decking products per m3(Mass allocation).... 51

Table 10-1: Life-cycle impact assessment for 100 ft2(9.29 m2) of redwood decking (Mass 

allocation) ..................................................................................................................................... 52

Table 10-2: Life-cycle impact assessment for one m3of redwood decking (Mass allocation) .... 53

Table 10-3: Environmental performance of 100 ft2(9.29 m2) of redwood decking from cradle-togate (Mass allocation)................................................................................................................... 54

Table 10-4: Environmental performance of 1 m3of redwood decking from cradle-to-gate (Mass 

allocation) ..................................................................................................................................... 54

Table 11-1: Life-cycle impact assessment for four decking products by percentage per 100 ft2

(9.29 m2) (EPA 2006) ................................................................................................................... 56

Table 11-2: Life-cycle impact assessment for four decking products per 100 ft2(EPA 2006).... 57

Table 11-3: Life-cycle impact assessment for four decking products per m3(EPA 2006) .......... 57
1

1 Introduction

The main scope of this project was to identify the critical environmental impacts of using redwood 

as a decking material relative to competing materials, including polyvinyl chloride (PVC) and 

wood–plastic composites (WPCs) at various recycled content (0% and 100%) for residential use. 

The environmental impact was determined using life-cycle assessment (LCA) techniques 

conducted to ISO 14040 standards. Conducting the LCA to these standards provided the added 

credibility that the results were not only scientifically sound, but were reviewed by independent 

experts. Additionally, the present study provided underlying LCA data should the California 

Redwood Association (CRA) choose to pursue environmental product declarations (EPD).

1.1 Background 

The Consortium for Research on Renewable Industrial Materials (CORRIM) is a non-profit 

research consortium with members from 16 universities and research institutions. Using a 

scientifically rigorous methodology, CORRIM has set out to evaluate the environmental 

performance of wood by researching the impacts of wood materials using the standardized tools 

of life-cycle analysis. CORRIM has helped build a multi-national database of the environmental 

and economic impacts associated with using renewable materials (Bowyer et al. 2001). 

CORRIM has provided wood building material’s LCI data to the United States Life Cycle 

Inventory (US LCI) Database (USDA 2013). The present decking LCA study used the 

methodology and protocols put forth by CORRIM and ISO standards (CORRIM 2010; ISO 

2006a; 2006b).

LCI data are a major component of a LCA. LCA uses rigorous methodology to find the critical

environmental impact for a particular product, referred to as “cradle-to-grave” (raw material 

extraction to waste disposal) analysis. LCI measures all the raw material and energy inputs and 

outputs required to manufacture a particular product on a per unit basis within carefully defined 

system boundaries. The current LCI study includes forest resources, resource transportation, 

manufacturing, product transportation, final product use, maintenance, and final disposal for 

redwood decking (Figure 1-1) (ISO 2006a; 2006b).

In the present study, forest resources include stand establishment and raw material extraction. 

Stand establishment involves nursery operations, seedling planting activities, intermediate 

treatment activities (fertilization and pre-commercial thinning/selection), and silvicultural 

systems used. The analysis includes the environmental and energy costs on a per unit basis using 

data from individual LCI studies.
2

Figure 1-1: Complete life cycle from regeneration of trees to disposal of wood materials

(Based on Fava et al. 1994).

A LCA is comprised of four stages (phases) as defined by the ISO. These are 1) goal and scope 

definition, 2) inventory analysis, 3) impact assessment, and 4) interpretation (Figure 1-2). A 

LCA study includes all stages, but a LCI study does not include stage 3, the impact assessment 

(SAIC 2006, ISO 2006a; ISO 2006b). 

Figure 1-2: Life-cycle assessment phases.

The full life-cycle study can provide information about the potential environmental impacts 

associated with a product or service or the impacts implied by any product selection decision. It 

represents the holistic yardstick of environmental performance. That assists us to understand and 

avoid possible “burden shifting;” such as from the manufacturing to the use phase of the 
3

product’s life cycle, or resolving environmental problems while simultaneously creating 

economic or social problems.

1.2 Significance 

A redwood decking LCA can be important to both manufacturing and consumer groups. This 

LCA information could be useful to wood product manufacturers, policy makers, and consumers 

concerned with the physical environment, the sustainability of natural resources, and 

sustainability of local businesses. 

Consumers make choices to buy or use products made from metal, wood, plastic, or concrete 

daily. Consumers base product selection on a broad range of attributes including price, quality,

and intended service application. In recent decades, the burdens that a particular product may 

place on human health and the physical environment have begun receiving increased 

consideration. To help make informed product choices consumers need transparent, scientifically 

verified, unbiased life-cycle information. 

The LCA methodology used by CORRIM can provide this information as it has for an array of 

wood products across multiple geographic regions using LCIs. However, no such inventory or 

LCA was completed for redwood decking in the United States. Given the popularity of redwood 

for residential decking, an evaluation of the collective material and energy inputs and outputs 

required to manufacture this product was needed. 

2 Goal of the study

The goal of the study was to identify the critical environmental impacts of using redwood as a 

decking material relative to plastic (cellular PVC) and WPCs at various recycled content (0% 

and 100%) for residential use. From this point on, cellular PVC is referred to as PVC in this 

paper. The environmental impact was determined using LCA techniques conducted to ISO 

14040 (ISO 2006a) and 14044 (ISO 2006b) standards. Conducting the LCA to these standards 

provided the added credibility that the results were not only scientifically sound, but they had

been third-party reviewed by a panel of independent experts. This extra level of effort was aimed 

at performing a comparative assertion between the four decking materials. The LCA outcomes 

resulted from this study were intended to be used in a comparison for future disclosure to the 

public. In addition, a third-party review supported future endeavors should the CRA and its 

members, the primary intended audience, choose to pursue environmental product declarations

(EPDs), a Type III eco-label for redwood decking.

Other intended audiences included manufacturers and policymakers as well as buyers of decking 

material. For decking manufacturers, the continuous improvement of the manufacturing process 

is essential to remaining competitive. Through the collection of primary forestry and 

manufacturing data required to model the LCA of redwood decking, the present study identified

improvement opportunities for participating redwood sawmills in the areas of wood use,

efficiency, and energy efficiency. A full-length comprehensive report will be made available on 

the CORRIM website (www.corrim.org). Only data in an aggregated form will be released 

publicly to protect proprietary information.
4

3 Methodology

3.1 Scope of the Study 

The scope of the study covered the full life cycle of redwood decking and decking made from 

PVC and WPC at 0% and 100% recycled content. Figure 3-1 shows the region of northern 

California where both harvesting of redwood decking logs and the conversion of logs into the 

final product occurred. Redwood decking production is primarily a local activity: forest 

management practices and product manufacturing processes take place along coastal northern 

California. The dimensions for redwood decking examined were 38 × 140 mm (2 × 6 in). The

redwood decking LCA was constructed using primary data to evaluate the environmental 

impacts of redwood decking. WPC and PVC decking LCAs were constructed from peerreviewed literature and other secondary and tertiary data sources. Redwood, PVC, and WPC 

decking materials were evaluated on a functionally equivalent basis with respect to service life. 

The service life selected for those four decking materials was 25 years. Results included

cumulative energy consumption, air emissions, fresh water usage, material resource 

consumption, and solid waste. 

Figure 3-1: Shaded region shows area of redwood decking production.

3.2 Functional Unit 

Delineating system boundaries determined the unit processes to include in the analysis and 

standardized material flows, energy use, and emission data. The functional unit of installed 

100 ft2(9.29 m2) of decking material was selected with a service life of 25 years, and the 

thickness depending on material selection. The other three decking materials were assumed to 

have a service life of 25 years as well. The U.S. decking industry uses square footage. Therefore, 

the unit of 100 ft2 was preferred over SI unit of square meters, which is typical for markets

outside the United States. Based on U.S. industry measures, we used the conversion of 1,000
5

board feet (MBF) of green and dry wood decking equally 2.36 m3and 1.62 m3, respectively, 

because wood shrinks as it dries from its green state to its final dry state and is planed (Bergman 

2010). For dry redwood decking, 10 m2at 38-mm thickness equals 0.375 m3(231 bf). Decking is 

usually sold by the board. A one 8-ft 2 × 6-in green and dry wood board is considered 8 bf (i.e., 1 

bf per linear foot) whether green or dry. Results of the LCIA and other impact measures were 

reported on a 100 ft2(9.29 m2) and m3basis.

Table 3-1 shows reference flows and actual thicknesses for the following decking products: 

redwood, WPC, and PVC.

Table 3-1: Reference flows for redwood, polyvinyl, and wood–plastic composite decking

Decking material

Mass

(kg/m3)

Reference 

flow

(kg/10m2)

Reference 

flow

(kg/100ft2)

Reference 

flow

(kg/1000 bf)

Thickness

(mm)

Conversion 

(100 ft2/m3)

Redwood1380 145 135 897 38 0.354

Polyvinyl chloride 660 168 156 1,557 25 0.236

Virgin WPC2960 287 266 2,265 25 0.277

Recycled WPC2960 287 266 2,265 25 0.277

1 Miles and Smith 2009 (properties measured at 12% MC and mass values listed as oven-dry). 

2 Klyosov 2007.

3.3 System Boundary 

This project considered the full life cycle of all the decking products, starting from raw material 

extraction to final disposal in a municipal solid waste (MSW) landfill with methane capture 

(Figure 3-2). For redwood decking, raw material extraction included forest resources. Forest 

resources included stand establishment and activities such as nurseries. Additionally, do-ityourselfers complete most decking projects and usually send their old decking material, when 

replaced, to a MSW landfill. California, the largest market for redwood decking, has passed 

regulations in 2011 requiring landfills without equipment to install methane capture technology 

by 20121. An additional scenario analysis was conducted on the end-of-life approach from the 

Mahalle and O’Connor (2009) study indicating that only 59% of MSW landfills had landfill gas 

collection systems (EPA 2006; Themelis and Ulloa 2007). Joists and posts used to support the 

deck were omitted from this analysis since these materials are common for all systems. 

 

1

http://www.calrecycle.ca.gov/LEA/Mail/2009/MethaneCap.htm.
6

Figure 3-2: System boundary for decking from cradle-to-grave.

3.4 Allocation Procedures 

Defining the allocation between co-products for LCI flows of emission data and energy and 

material inputs is a necessary step of the LCA process. In the present study, WPC and PVC 

decking did not require an allocation method because their manufacturing did not generate any 

co-products that were not reground and mixed back into the final product. Therefore, all 

emissions and inputs were attributed solely to the decking product. In contrast, redwood decking 

required the selection of an allocation method because there were a number of co-products 

produced along with the decking lumber. 

For redwood, mills produce many other redwood lumber products in addition to the 38- × 140-

mm decking (Figures 3-3). Additionally, redwood mills process some Douglas-fir (Pseudotsuga 

menziesii) logs into rough green lumber. Therefore, the 38- × 140-mm (nominal 2- × 6-) 

redwood decking must be separated from Douglas-fir products and then further allocated 

redwood logs on a mass basis between the various redwood products based on the weighted 

average input for the redwood sawmills surveyed.

As redwood decking products are far more expensive (10:1 ratio) than the wood residues 

produced during the manufacturing process (such as bark, sawdust, and chips), all LCI burdens 

were assigned to the redwood decking just like the other decking products. Thus, in the case of 

redwood decking products, no LCI burdens were assigned to the wood residues. The wood 

residues were still considered during the calculation of the wood mass balance. Therefore, the 

present study allocated all LCI flows to the redwood decking and none to the wood residue 

generated during the production of the redwood decking. A sensitivity analysis was conducted on 

a mass allocation approach for comparison.
7

In practice, this resulted in the burdens from the redwood wood residues, which represented

about 40% of the mass of the logs entering the sawmill, being allocated to the redwood products 

on a mass basis. As an example, if the condition arises that 30% of the incoming redwood log 

mass becomes redwood decking, and another 30% becomes other redwood lumber products, the 

remaining 40% of the incoming redwood logs are various wood residues2. In this case, since no 

LCI burdens are assigned to the wood residues, 50% of the LCI burdens are assigned to the 

redwood decking (30% from decking plus half the residue burden or 20%) and 50% to the other 

redwood lumber products because the mass of the two categories of redwood products (redwood 

decking and other redwood lumber products) are equal.

Figure 3-3: Diagram showing the wood flow through the production center (i.e., sawmill).

3.5 Decking 

3.5.1 Plastic (PVC)

Plastic decking, which is primarily made from PVC, has a relatively small market share but it has 

the fastest market growth. Plastic decking currently sold in the California market is referred to as 

cellular (solid) PVC. Unlike cellular PVC decking, hollow PVC products have been unable to 

pass the California State Fire Marshals Code for Wildland Urban Interface Zones and are of no 

interest in this study3. Cellular PVC is about half the weight of standard PVC because of a 

foaming agent added during the manufacturing process, which is referred to as acrylic foam cell 

stabilizer (Anonymous 2009). For this report and previously mentioned, the term “PVC decking” 

was used to refer to cellular PVC unless otherwise specifically noted. The primary component 

used to manufacture about 85% of PVC decking is PVC resin. PVC resin is made from an 

ethylene dichloride-vinyl chloride monomer through polymerization. The monomer is produced 

from chlorine and ethylene derived from natural gas with the addition of liquid oxygen. Figure 

3-4 shows the manufacturing process diagram of plastic decking starting with PVC resin and the 

addition of the foaming agent (FAL 2010; PRé Consultants 2013; Trex 2009; Lippiatt 2007).

 

2 The ratio of 60% products and 40% wood reside is maintained regardless of the redwood product produced.

3

Personal communication 10/25/2011 Charlie Jourdain, California Redwood Association. 
8

The US Ecoinvent (EI) database provided an extrusion process for plastics based on European 

manufacturing data. This study modified data by considering energy consumption from U.S.

energy sources. This was the best data source available in the SimaPro model to make 

meaningful comparisons. Inherent in this data choice, region-specific data on energy sources 

were incorporated into the plastic manufacturing databases.

Figure 3-4: Cradle-to-gate manufacturing process diagram for cellular PVC decking

(Mahalle and O’Connor 2009).

3.5.2 Wood–plastic Composites (WPC)

WPC decking has a larger market share than PVC decking but its share is still less than wood 

decking. WPC decking is manufactured using a mixture of wood fiber and plastic resins plus 

some ancillary materials. WPC uses polyethylene (PE) as its primary feedstock. Two of the most 

common resins used in WPC are high-density polyethylene (HDPE) and low-density 

polyethylene (LDPE) (FAL 2010; Klyosov 2007).

The focus of the present study was on both virgin and recycled PE used to manufacture WPC 

decking. Mahalle and O’Connor (2009) provide the basis for the WPC decking formulations 

used in this study. Figures 3-5 and 3-6 illustrate the cradle-to-gate manufacturing process for 

virgin and recycled WPC decking, respectively. The source material used to manufacture 

recycled WPC is generally derived from plastic grocery and retail bags. Other sources include #2 

recycled products such as detergent and soft drink bottles. However, clean plastic bags used in 

the present study are the preferred feedstock in the recycling process to eliminate additional 

processing steps, such as washing and drying (Climenhage 2003). 
9

Hammermills grind dry wood shavings into wood flour. Blenders combine the wood flour with 

PE resin and other materials during the WPC extrusion process. WPC decking is primarily made 

on the East Coast but there is one manufacturing plant located in Fernley, NV, that supplies the 

West Coast (http://www.wpcinfo.org/producers/deck/). Details from this plant were used in our 

model to most fairly represent the comparisons between redwood decking and competing 

products.

Figure 3-5: Cradle-to-gate manufacturing process diagram for virgin WPC decking 

(Mahalle and O’Connor 2009).

Figure 3-6: Cradle-to-gate manufacturing process diagram for recycled WPC decking

(Mahalle and O’Connor 2009).
10

The US EI database included an extrusion process for plastics that provides energy consumption. 

The extrusion process included all available US LCI Database data in the SimaPro model. 

3.5.3 Redwood

Redwood logs are sawn into decking with some wood residues generated. Green wood residues 

include sawdust, chips, hog fuel, and bark. Planing rough lumber generates shavings. Some 

redwood decking is kiln-dried after being air-dried. Approximately 36% of redwood decking was 

sold green, with the remaining 64% being air-dried. After air-drying to less than 30% MC, 57% 

of the decking is further dried in the kiln so that 36.6% of total redwood decking leaves the mill 

as a kiln-dried product. Redwood decking is primarily sold on the West Coast with only a small 

volume of material being shipped east. Figure 3-7 describes the basic unit processes and the 

system boundaries for cradle-to-gate manufacturing of redwood decking. Inputs include 

packaging as well as electricity, diesel, natural gas, steam, propane, and gasoline.

Redwood decking is processed similarly to other types of lumber products. A comparable wood 

product to redwood decking is structural Douglas-fir lumber. It was cited in a LCI study done by 

Milota in 2004 because most Douglas-fir is sold and installed green. In addition, since most 

redwood decking is not kiln-dried or at least not kiln-dried until first air-dried; manufacturing 

redwood wood decking uses significantly less energy than that of other wood materials

(Puettmann et al. 2010). CORRIM has previously studied involving certain grades of Douglas-fir 

structural lumber that are not kiln-dried (Milota et al. 2004; Puettmann and Wilson 2005). 

Figure 3-7: Cradle-to-gate wood decking manufacturing (Puettmann et al. 2010).
11

3.6 Life-Cycle Impact Assessment Methodology and Types of Impacts 

Once the complete cradle-to-grave LCI has been constructed for redwood decking, the following 

environmental mid-point impact categories of global warming potential (kg CO2-eq), 

acidification potential (kg SO2-eq), respiratory effects (PM 2.5-eq), eutrophication potential (kg 

N-eq), ozone depletion (kg CFC-11-eq), and smog potential (kg O3-eq) were calculated using 

TRACI 2.1 impact estimators. Cumulative energy demand (primary energy) (MJ-eq), including 

both the biomass and fossil fuel contributions, were calculated and reported directly from LCI 

flows. The present study tracked fresh water consumption (in L) and renewable and nonrenewable material resource consumption (non-fuel resources). Impact categories and other 

impact measures were reported on a 100 ft2(9.29 m2) and m3basis.

An EPD of redwood decking may be developed based on the results obtained in this LCA project

(FPInnovations 2011). Therefore, the following additional environmental information was

derived from the LCA flows in accordance with ISO 21930 Clause 8.2 (ISO 2007):

1. Generation of waste

2. Emissions to water, soil, and air

3.7 Interpretation 

In conducting the LCIA, the present study did not go beyond the mid-point impact categories 

highlighted in ISO 21930 (ISO 2007). End-point impact categories will not be calculated because 

of their higher level of uncertainty compared to the mid-point categories. The LCI flows were 

converted to the above impact categories according to TRACI 2.1 method found in SimaPro 7 

(PRé Consultants 2013). Carbon storage in the final product was included as part of the life cycle

for redwood and WPC decking. Additionally, see Section 5.4.1.6 for redwood decking 

calculations on carbon sequestration. These calculations helped develop the carbon balance for 

redwood decking.

3.8 Assumptions 

 Specific gravity, density, and other physical properties of redwood (Sequoia 

sempervirens) were sourced from Alden (1997), Jones and O’Hara (2012), and Miles and 

Smith (2009). 

 Redwood decking was assumed to equilibrate at 12% moisture content (MC4) after 

installation. Green redwood logs, however, were 127% MC and heartwood was 100%

MC. 

 Redwood decking includes both pure heartwood and a mixture of heartwood and 

sapwood (Piitro 1986; Highley 1995; Jones et al. 2011). Redwood decking is not 

pressure-treated because it is mostly heartwood.

 38- × 140-mm (2- × 6-in) redwood decking weighs 1,400 pounds per MBF.

 Using higher heating values (HHV), this study converted fuel from its volume or mass 

basis to its energy value. HHV represents the (gross) energy content of a fuel with the 

combustion products at 25°C (77°F) with all water vapor brought to liquid form. Whereas 

lower heating value (net energy) maintains the water in the combustion product in vapor 

 

4 Moisture content (MC) is calculated on a dry basis. 

 

 

 .
12

form at 150°C (302°F). HHV instead of lower heating values is the preferred method in 

the United States to calculate energy values (EIA 2013).

3.9 Value Choices and Optional Elements 

Optional LCIA steps such as normalization, grouping, and weighting were not completed. Endpoint impact categories such as Eco-Indicator 99 were not used because of their higher level of 

uncertainty as compared to the mid-point categories reported using the TRACI method. The 

LCA analysis, particularly at end-of-life, was chosen to be as consistent as possible to the other 

decking materials to allow for an objective comparison.

3.10 Limitations 

3.10.1 Omissions of life-cycle stages, processes, input or output flows

Human labor and the manufacturing LCA of machinery and infrastructure, including logging 

roads, was outside the system boundaries and therefore not modeled in this analysis.

3.10.2 Decision Criteria (cut-off rule, if applicable)

All materials used in the logging and manufacturing process that have a significant 

environmental impact were tracked. For the present study, mass and energy that contributed less 

than 1% to the total output were not modeled in the SimaPro LCA software. Initially, all LCI 

flows were included in the impact categories. The final analysis included any mass or energy 

resource that resulted in a greater than 2% change to any impact category.

3.11 Data Quality Requirements 

(1)Time-related coverage, (2) geographical coverage, (3) technological coverage, (4) 

representation, and (5) sources of data: Primary data for redwood decking was collected for raw 

material extraction (i.e., harvesting) and product manufacturing for 2010 and 2011 on an annual 

basis from redwood operations in northern California. Additional LCI data on decking materials 

was drawn from the externally reviewed LCA report of Mahalle and O’Connor (2009) and 

Franklin Associates (FAL) (2010) and peer-reviewed literature such as Bolin and Smith (2011). 

Secondary data from other life-cycle inventory (LCI) databases was used in the following order 

of preference: US LCI Database (USDA 2012) and the U.S. version of the European database 

EcoInvent (www.ecoinvent.ch) referred to as US IE.

The four redwood mills included in this study are members of the CRA, who sponsored the 

study. These mills located in California are in Davenport, Scotia, Korbel, and Ukiah. The four 

mills produced about 90% of redwood decking manufactured in the United States in 2010. One

redwood mill did not kiln-dry their decking but the other three redwood mills did some kiln–

drying.

(6) Precision: To aid in validating the data precision, the present study surveyed a minimum of 

50% of redwood production in the United States. According to the USDOC (2011) and Binam 

(2013), twelve redwood mills produced 614 thousand m3 (260 million board feet (bf) ). Thus, to 

meet the data requirement, approximately 308 thousand m3 of redwood production was to be 

surveyed from a minimum of four sawmill facilities. In 2010, the annual production of the four 

California redwood mills surveyed was 552 thousand m3 (260 million bf). This represented 

approximately 90% of the total rough green redwood lumber production in the US. Individual 
13

mill production ranged from 44.4 to 238 thousand m3 (18.8 to 101 million bf) of rough green 

lumber. The data collectors gathered process-specific data on-site wherever possible.

(7) Completeness, (8) Uncertainty, and (9) Consistency: Measures of completeness and 

uncertainty were provided, including a listing of study limitations and assumptions. To deal with 

potential unknowns, sensitivity and scenario analyses were conducted to address these issues as 

necessary. A mass balance, from material input to material output for the sawmill, energy 

comparison to other wood products, and a sensitivity analysis were conducted to address 

uncertainty in data quality. Redwood sawmills reported primary data for the whole sawmill on an 

annual basis.

(10) Reproducibility: Questionnaires were used to survey the redwood operations to collect 

primary data on both timber harvesting (APPENDIX 13) and lumber manufacturing.

(APPENDIX 14). The primary data obtained from the surveys were weight-averaged using the 

formula shown below (Milota et al. 2004):







  n

i

i

n

i

i i

x

Px

P

1

1

weighted

Where

Pweighted

is the weighted average of the values reported by the sawmills, Piis the reported 

sawmill value, and

i

x

is the fraction of the sawmill’s value to total production of the surveyed 

mills for that specific value. The cradle-to-gate LCI flows for the four decking materials were 

provided in a separate attachment titled “Cradle-to-grave LCI flows of four decking products”.

3.12 Peer Review 

For maximum credibility and transparency, the analysis and results were subject to an 

independent peer review panel organized by Wayne Trusty (Wayne B. Trusty & Associates

Limited; Merrickville, ON,, Canada, Tel: (613) 269-3795, e-mail: wbtrusty@sympatico.ca) who 

served as the Panel Chair. The other panel members were Getachew Assefa Wondimagegnehu, 

Associate Professor at the University of Calgary and Athena Chair in Life Cycle Assessment in 

Design, and Gary Rynearson, Forest Policy Manager of Green Diamond Resource Company.

3.13 Electrical Grids 

Table 3-2 provides the location and regional grids used in SimaPro to model the environmental 

impacts from using grid electricity. The electrical grid is broken into 26 regions of the United 

States5.

 

5

eGrid: http://cfpub.epa.gov/egridweb/ghg.cfm.
14

Table 3-2: Regional grids in SimaPro for decking production

Process Location Grid Comments

PVC resin production Louisville, KY SRTV 2008

PVC decking production Columbus, OH RFCW 2008

Virgin HDPE resin production Fort Worth, TX ERCT 2008 50% of total production

Virgin HDPE resin production Magnolia, AR SRMV 2008 50% of total production 

Planer shavings Pacific Northwest NWPP 2008

Recycled HDPE pellets Fernley, NV NWPP 2008 Local pellet production

WPC decking production Fernley, NV NWPP 2008

Redwood production region Upper northern CA NWPP 2008 50% of total production

Redwood production region Lower northern CA CAMX 2008 50% of total production

4 Cradle-to-Gate Life-Cycle Inventory Data

This section covered the life cycle of decking products from resource extraction to creation of 

final product at mill gate. 

4.1 Polyvinyl Chloride 

The cradle-to-gate LCI data for PVC decking was developed using existing LCI and productionrelated data including a 2009 decking and siding report (Lippiatt 2007; Mahalle and O’Connor

2009; Trex 2009; FAL 2010). PVC decking formulation was based on the assumption that siding 

and decking manufacturing processes were similar. No PVC resin plants exist in California6.

TimberTech XLM decking is a major seller of PVC decking into the West Coast, therefore their 

product was used to represent PVC decking in this study. TimberTech XLM decking is made in 

Columbus, OH7. As for the manufacturing of PVC resin, the primary component (82.5%) of 

PVC decking, the closest plant to Columbus, OH, was located in Louisville, KY (325 km). 

Resource transportation was based on hauling the PVC resin from Louisville to Columbus by 

diesel tractor-trailer. Table 4-1 lists the ingredients for the production of one metric ton of PVC 

decking (Lippiatt 2007). One metric ton of PVC decking corresponds to 640 ft2(59.5 m2) of 

installed decking (156 kg/100 ft2). Table 4-2 lists the energy resources used during the extrusion 

process derived from the US EI database to make one metric ton of PVC decking.

Table 4-1: Resource list for manufacturing one metric ton of polyvinyl chloride decking (Lippiatt 2007; 

Mahalle and O’Connor 2009)

Ingredients Amount Unit Percent Database

PVC resin 825 kg 82.5 US LCI

Filler (calcium carbonate) 85 kg 8.5 US LCI

Titanium dioxide 25 kg 2.5 US LCI

Impact Modifier (acrylic or chlorinated PET) 40 kg 4.0 US LCI

Stabilizer (organo-tin mercaptide) 10 kg 1.0 US EI

Lubricant (parrafin/calcium stearate) 15 kg 1.5 US EI

 

6 EPA to regulate PVC plant emissions http://earthjustice.org/features/epa-to-regulate-pvc-plant-emissions .

7

Personal communication on 01/18/2012, TimberTech Live Chat.
15

Total 1000 kg 100

Table 4-2: Energy resources required to produce one metric ton of PVC decking (Lippiatt 

2007; Mahalle and O’Connor 2009)

Plastic extrusion energy inputs Unit Amount Database

Electricity kWh 508 US LCI

Natural gas MJ 121 US LCI

Heavy fuel oil MJ 683 US LCI

4.2 Wood–plastic Composite (virgin and recycled) 

The manufacturing process was comprised of two parts: raw material preparation and extrusion. 

For WPC decking, wood flour and HDPE made up the primary ingredients and include some 

ancillary materials as shown in Table 4-3 and Error! Reference source not found. (Mahalle and 

O’Connor 2009; Bolin and Smith 2011). At 50%, wood flour was the largest ingredient in 

making WPC decking. In addition, because the WPC decking was 50% wood (i.e., wood flour), 

carbon uptake during tree growth was considered. A carbon storage value of 917 kg of CO2 per 

metric ton of final product8 was calculated. The CO2 stored in the final product was given a 

characterization factor of –1 when calculating GWP. Note that no existing LCI data exists for 

maleated polyolefins. Therefore, a 50:50 mix of HDPE (10 kg/metric ton decking) and acetic 

acid formulation (10 kg/metric ton decking) was used as a proxy.

Table 4-3: Resource list for manufacturing one metric ton of wood–plastic composite decking (Mahalle 

and O’Connor 2009)

Ingredients Mass (kg) Percent Database

Wood flour 500 50 US LCI

PE (virgin and reprocessed) 400 40 US LCI

Talc 20 2 US EI

Polyester resin (lubricant) 20 2 US EI

Borax (Biocide-borate) 20 2 US EI

Titanium dioxide 20 2 US LCI

Acetic acid (coupling agents-acid 50%) 10 1 US LCI

HDPE resin (coupling agent-PE) 10 1 US LCI

Total 1000 100

Table 4-4: Ancillary list for producing one metric ton of virgin wood–plastic composite decking (Mahalle 

and O’Connor 2009)

Lubricating oil (motor oil; assume 1 kg/l) 0.012619054 Kg US EI

Lubricating oil (grease) 7.94E-07 Kg US EI

Diesel oil .0968 L US LCI

4.2.1 Raw Material Preparation

As shown in Table 4-3, wood flour from planer shavings and PE resin were the two main 

components in WPC decking. Wood flour production includes the transport of planer shavings

 

8

500 kg wood/metric ton WPC × 0.5 kg carbon/1.0 kg wood × 44 kg CO2/12 kg carbon = 917 kg CO2/metric ton.
16

from the softwood sawmill to the WPC decking plants, the grinding of planer shavings to a flour 

consistency using hammermills and pre-drying of wood flour before mixing with the PE resin.

Environmental burdens assigned in producing wood flour from planer shavings used in making 

WPC decking were consistent with previous decking LCA studies (Mahalle and O’Connor 2009; 

Bolin and Smith 2011). Wood flour was stored in a silo. Softwood mills, providing planer 

shavings, were 1,200 km from the decking manufacturing facility located in Fernley, NV. Trex

(San Jose, CA), a large WPC decking manufacturer, has a plant located in Fernley, NV, that 

supplies both virgin and recycled WPC decking to the western United States. Therefore, Trex 

WPC decking was the virgin and recycled WPC decking analyzed in the present study. 

For virgin HDPE resin, the nearest HDPE plants were located in Fort Worth, TX, and Magnolia, 

AR; therefore, an average transport distance of 4,400 km was calculated. For reprocessed LDPE

going into recycled WPC decking, the raw material consisted of bailed clean and dry grocery 

plastic sacks. Dirty grocery plastic sacks require washing and drying (a process that consumes 

considerable energy). It is assumed that enough clean and dry plastic sacks were available within 

an average transportation distance of 250 km and that the mode of transportation was a single 

unit truck. Therefore, no washing and drying occurred. The weighted average raw material 

transportation for all raw materials was based on the transportation distance of wood planer 

shavings (1,200 km), either virgin or reprocessed PE resin, and the additives (70 km). Virgin 

HDPE resin was assumed to be mostly transported by rail (80%) and the remaining distance by 

diesel tractor-trailer truck (20%) because of the long distance between the HDPE resin plant and 

the WPC decking plant. 

WPC decking was made from either 100% virgin HDPE or 100% reprocessed LDPE. The only 

product from the plants is WPC decking. Therefore, all LCI flows were assigned to the decking. 

Reprocessed LDPE was located considerably closer to the decking plant than virgin LDPE. Only 

clean and dry plastic LDPE sacks were used in making the 100% recycled content WPC decking.

Therefore, careful handling of the plastic grocery sacks was necessary to prevent recontamination of the dry and clean bags that would have had added additional processing.

Figure 4-1 details the handling processes for preparing LDPE bags before the extrusion process. 

The bailing process compacted the clean and dry bags for easier handling, transporting, and 

processing upon arrival at the WPC decking plant.
17

Figure 4-1: Stages of processing for LDPE bags (Climenhage 2003).

4.2.2 Wood–plastic Composite Processing

Additional processing of the material inputs occurred at the WPC decking plant. Grinding the 

planer shavings into wood flour included both a grinder and a dust collection system. 

Hammermills ground the wood flour to a 20- to 60-mesh size. A conveyor system transported the 

wood dust collected from the grinding process to a silo for processing into the WPC decking 

(LDED 2005). A second silo contained the PE resin.

The extrusion process involved blending the wood flour with the PE resin along with the other 

ingredients. Additional manufacturing processes included profiling the decking along with 

cooling, sizing, and surfacing. The largest impacts associated with the extrusion process were 

from energy consumption. Wood fiber drying, blending/compounding, profiling the extrusion

and other downstream processes consumed substantial amounts of energy. Other air emissions 

included CO2 from wood fuel and minor emissions from the polymers as well as emissions from 

the venting process associated with the biocide (Borax). Fugitive emissions were less than 1% of 

the total and therefore not included in the LCA. Electricity was the primary energy source for the 

extrusion process (Mahalle and O’Connor 2009).

A common practice during WPC decking manufacturing is for the WPC decking waste generated

on-site during the product manufacturing process (e.g., from defective decking at the production 

facility) to be reground and added back into the raw material mix. Regrind amounts typically add 

up to 5–10% of the mix (LDED 2005). In the current project, a pair of hammermills reground the 

defective material to 1/8-inch particle size. For the grinding dust, a collection system gathered

the fugitive wood dust and mixed it back into the process. 

4.2.3 Process Energy

Electricity was the main energy consumed during WPC decking production, from a cradle-togate perspective. In the 2009 LCA report by Mahalle and O’Connor, the extrusion process 
18

consumes 1,420 kWh/metric ton of decking produced. The US LCI Database has a unit process 

called “recycling HDPE postconsumer pellets” that consumes 490 kWh/metric ton. Both values 

are listed in Table 4-5. For wood flour manufacturing, the hammermills consumed 58 

kWh/metric ton to produce 40-mesh wood flour from dry planer shavings.

Table 4-5: Electrical energy consumed for the two main unit processes

Category Unit process

Amount 

(kWh/tonne)1 Database

Raw material processing

Wood flour manufacturing3

58 US LCI

Recycled HDPE pellets2

490 US LCI

WPC manufacturing

Extrusion process3

1,420 US LCI

Regrinding3

6 US LCI

1 WPC decking is 2.27 metric tons/ thousand bf (2.50 tons/thousand bf). 

2 US LCI Database process.

3 Brown (2008); Goertermiller (2012); Bolin and Smith (2012); Mahalle and O’Connor (2009).

4.3 Redwood 

4.3.1 Forest Resources

Redwood is a unique species growing naturally along the coastal area of northern California. The 

primary source of data used for this study was collected from four redwood forest products 

companies in northern California. The four mills represented 83% of redwood decking product 

production in 2010. A survey questionnaire in Appendix 13 was developed to collect forest 

resource management data. Questions related to log volume in MBF harvested through the 

rotation age of the forest stand were also in the survey. The survey was completed based on the 

2010 calendar production year. These data were combined with information from the existing 

literature and personal interviews. An overall forest management scenario and assumptions used 

for the analysis of the present study are outlined in Table 4-6, Table 4-7, and Table 4-8.

4.3.1.1 Survey Data Including Assumptions

The survey data were aggregated and summarized to calculate weighted average values that 

represent a mean value for each category of interest. Weights were based on each company’s 

annual harvest volume, silvicultural methods (i.e., even-age or thinning/selection), and 

harvesting systems used (Figure 4-2). The data summary and initial calculation values were 

entered into the harvest factors spreadsheet that was developed for prior CORRIM reports 

detailing LCA and LCI for wood products in the United States (Johnson 2008). The harvest 

factors spreadsheets integrate stand establishment, intermediate treatment, timber harvest, and 

transportation factors into a presentation of total cost, fuel and oil consumption rates, and carbon 

footprint associated with wood removal and equipment used. 
19

Table 4-6: Assumptions and input values used for the environmental impact analysis of redwood forest1

resources management1

Thinning/Selection Even-age2

Seedling planting density 

(trees per ha)

432 (175 per acre) 319 (129 per acre)

Fertilization to trees None None

Harvest volume (% total) 47 53

Harvest volume (m

3

/ha) per entry 1003,4(7.41 MBF/acre) 3003,4(21.81 MBF/acre)

Harvest unit size (ha) 14.2 (35 acre) 10.1 (25 acre)

Age of trees (years) 40-100+ 60

1Estimate of bark as percent of solid wood: 9.9% after accounting for handling losses

Average skidding/yarding distance: 202 m (663 feet) for all harvesting systems used

One-way log hauling distance: 53.1 km (33 miles) in average

Specific gravity (green): 0.36 (Miles and Smith 2009). 

Carbon fraction (mass carbon per unit mass dry wood): 0.53 (Jones and O’Hara 2012).

2Even-age results were compiled from responses for clearcut harvesting systems on the survey form.

3Thinning/selection enters every 20-year to harvest 7.41 MBF/acre.

4Based on a conversion factor of 190 ft3

/MBF (Fonseca 2005); 35.3145 ft3/m3; 2.47 ac/ha.

Table 4-7: Fertilization rates to grow coast redwood two-year old seedlings

Fertilization1 Nitrogen (N) Phosphate (P) Potassium (K)

(kg/ha) 0.137 0.125 0.208

(kg/seedling) 0.00100 0.00091 0.00151

1 The values of lb/acre are based on the planting rate of 137 seedlings per acre of forestland (2.205 lb/kg; 2.47 ac/ha).

Table 4-8: Fuel and lubrication consumption rate for tree planting and pre-commercial thinning

Gasoline (L/ha-km1) Lubrication (L/ha-km1)

Tree planting 0.00386 0.000069

Pre-commercial thinning/selection 0.00649 0.000118

1Distance from a seedling storage place to a planning site.
20

Figure 4-2: Redwood forest operations producing saw logs and biomass.

SimaPro 7.3 LCA modeling software (PRé Consultants 2013) estimated environmental outputs 

to the air and water from the redwood forest management activities from weighted-average 

survey data. The first step was to develop the redwood resource database within the SimaPro 

program. The information that was summarized in the harvest factors spreadsheet was entered 

into SimaPro based on a cubic meter (saw logs), a bone-dry metric ton (biomass), or a perhectare basis (reforestation). 

Key input values entered include fuel/oil consumptions and volume removed/acre for six 

different harvesting systems and two silvicultural methods (Table 4-9). Each harvesting system 

consisted of a set of machines that are commonly used to harvest redwood saw logs in northern 

California and consumed different amounts of fuels and lubricants. The survey questions were 

structured into four categories: stand establishment and forest inventory, harvesting systems and 

productivity, log transportation, and slash treatments and biomass recovery for energy. Under 

each category, survey questions were asked to describe forest management activities and 

resources that were required to produce redwood logs.
21

Table 4-9: Hourly productivity and fuel and lubricant use of redwood harvesting systems1

Machine type

Production 

rate Fuel use2 Lubricant use2

(m

3

/hour) (L/m

3

) (L/m

3

)

Manual ground-based system

Thinning/ Felling Chainsaw 5.30 0.505 0.0091

Selection Skidding Tracked crawler 7.15 6.894 0.1241

Processing Chainsaw 13.60 0.102 0.0018

Loading Log loader 22.87 1.964 0.0354

System total (stump-to-truck) 9.46 01.70

Skyline system

Felling Chainsaw 5.30 0.505 0.0091

Yarding Skyline yarder 9.93 6.363 0.1145

Processing Chainsaw 13.60 0.102 0.0018

Loading Log loader 22.87 1.964 0.0354

System total (stump-to-truck) 8.93 0.161

Helicopter system

Felling Chainsaw 5.30 0.505 0.0091

Yarding Helicopter 37.93 34.885 0.6279

Processing Chainsaw 13.60 0.102 0.0018

Loading Log loader 22.87 1.964 0.0354

System total (stump-to-truck) 37.46 0.674

Manual ground-based system

Even-age Felling Chainsaw 6.03 0.665 0.0120

Skidding Tracked crawler 12.11 4.412 0.0794

Processing Chainsaw 18.93 0.077 0.0014

Loading Log loader 22.87 1.964 0.0354

System total (stump-to-truck) 7.12 0.128

Mechanized ground-based system

Felling Feller-buncher 38.85 1.734 0.0312

Yarding Shovel 19.37 3.392 0.0611

Processing Stroke-boom delimber 38.74 1.551 0.0279

Loading Log loader 22.87 1.964 0.0354

System total (stump-to-truck) 8.64 0.156

Skyline system

Felling Chainsaw 6.03 0.665 0.0120

Yarding Skyline yarder 12.81 4.727 0.0851

Processing Chainsaw 18.93 0.077 0.0014

Loading Log loader 22.87 1.964 0.0354

System total (stump-to-truck) 7.43 0.134

Landing to Intermediate Load Site (L/mBDT3) (L/BDT3)

Biomass Loading: Loader 30.41 0.718 0.0129

recovery Pre-hauling: Dump truck- modified 13.82 0.936 0.0169

operation Centralized grinding

Loading: Loader 30.41 0.718 0.0129

Processing: Horizontal grinder 27.21 3.685 0.0663

System total (stump-to-truck) 6.06 0.109

1 The values presented in this table were based on each entry to the redwood stand to harvest redwood saw logs and logging slash 

for the year of 2010.

2

Included machine idling time (i.e., scheduled machine-hour, SMH).

3Bone dry metric ton.
22

4.3.1.2 Stand Establishment and Forest Inventory. 

This section of the survey requested information on stand establishment and an overview of 

redwood forest management plan and activities. Survey results provided information used to 

outline a framework of forest management practices that are commonly used by redwood forest 

products companies. Information collected included nursery operations, seedling planting 

activities, intermediate treatment activities (fertilization and pre-commercial thinning), 

silvicultural systems used, rotation ages, and volume removed each entry.

4.3.1.3 Harvesting Systems and Productivity. 

This section of the survey asked for descriptions of typical harvesting systems and equipment 

used to harvest timber from stump to truck, including felling, primary transport (stump-tolanding), processing, and loading (Table 4-9). Three major types of harvesting systems were 

surveyed: ground-based, skyline, and helicopter. 

These three harvesting systems were further divided based on equipment type used and 

silvicultural methods (i.e., thinning/selection, even-age) applied. Figure 4-2 shows the

percentage of the six harvesting system that provided the 814,405 m3(151,370 MBF) of redwood 

logs in 2010 and adds up to 100%.

In addition, survey questions were related to harvesting productivity (i.e., MBF/hour), cost 

($/MBF), and fuel/oil consumption rates for each harvesting equipment used. Additionally, 

machine utilization rates were surveyed to adjust hourly productivity and fuel/oil consumption 

rates.

4.3.1.4 Log Transportation. 

Log transportation started from the forest landing in the woods, included loading at the landing 

and unloading at the sawmill. Log transport was allocated to the manufacturing process that is 

consistent with other CORRIM research.

4.3.1.5 Slash Treatments and Biomass Recovery for Energy. 

The survey also requested a description of activities for managing slash resulting from timber 

harvest. It included data on percent utilization of trees cut, prescribed burning and biomass 

recovery operations for energy production (Figure 4-2). Operations productivity (i.e., ton/hour) 

and fuel/oil consumption rates were collected for biomass recovery equipment and systems that 

are commonly applied to utilize forest residues left from redwood saw log harvesting (Table 4-

9). Biomass recovery operations are relatively new to this region, but there has been an 

increasing interest in utilization of logging slash. For redwood logging slash, 48% of the total 

collected, 13,730 bone dry metric tons (15,140 tons) was delivered to local energy plants in 

2010.

4.3.1.6 Carbon Sequestration Calculation

Trees, the raw materials for wood products sequester carbon during its growth through 

photosynthesis, a natural process. Therefore, this study looked at the impact of carbon 

sequestration into the analysis by tracking the carbon uptake into the logs. The following 

calculations were performed to help develop a carbon balance on redwood decking. As 

previously mentioned, GWP did not include biogenic CO2 emissions to be consistent with 
23

TRACI 2.1. However, GWP in this study did include the carbon stored in the final product to be 

consistent with the revised North American wood product Product Category Rule (PCR). The 

analysis was broken into the two forest management practices (even-age and thinning/selection). 

By production volumes, even-aging was 53% of total with thinning/selection covering the 

remaining 47% as shown in Table 4-6. A weighted-average approach for the different practices 

was used for forest operations as shown by Figure 4-2. To aid in tracking both wood mass and 

carbon flow for the rest of the life cycle, the logs were broken into roundwood and bark. 

Percentage of roundwood (90.1%) and bark (9.9%) were from weight-averaged primary data 

collected at the sawmill. The following equations calculated the carbon sequestration values for 

the surveyed redwood forest removals for 2010 per hectare:

Even-age (kg/hectare):

Carbon uptake factor (i.e., CO2 equivalent) for round wood

= wood volume per Ha × specific gravity × 1000 × CO2 uptake factor x carbon content of wood

= 290.17 m3per Ha × 0.36 × 1000 × (44/12) x 0.53 = 203,003 kg CO2-eq per Ha

Carbon uptake factor (i.e., CO2 equivalent) for bark

= volume of bark × specific gravity ×1000 × CO2 uptake factor × carbon content of wood

= 32.50 m3per Ha × 0.36 × 1000 × (44/12) x 0.53 = 22,737 kg CO2-eq per Ha

Thinning/selection (kg/hectare):

Carbon uptake factor (i.e., CO2 equivalent) for round wood

= 100.13 m3× 0.36 × 1000 × (44/12) x 0.53 = 70,051 kg CO2-eq per Ha

Carbon uptake factor (i.e., CO2 equivalent) for bark

= 11.21 m3× 0.36 × 1000 × (44/12) × 0.53 = 7,842 kg CO2-eq per HA

Where 

 Specific gravity = 0.36 of green specific gravity when logs harvested

 1000 = converting from specific gravity to a unit of kg/m3

 CO2 uptake factor = the ratio of the atomic mass of a carbon dioxide molecule to the 

atomic mass of a carbon atom (44:12; EPA 2005)

4.3.1.7 Logging Slash Recovered for Power

Recovering slash helps reduce fire hazard and site preparation costs as well as avoid slash 

burning. Weight-averaging survey data calculates 16.9 oven-dry (OD) kg redwood logging slash 

fuel per m3of harvested redwood log. Based on power plant reported volume and energy 

production, one OD kg of wood fuel generates approximately 1.14 kWh (20% electrical 

conversion of electricity out to wood fuel in). Logging slash typically degrades naturally on the 

forest floor or is burned in the forest emitting biogenic CO2 thus becomes part of the natural 

carbon cycle. No scientific consensus has been developed to incorporate the impact of logging 

slash when burned to generate electricity once the stem has been removed for processing. Likely, 

the power plant burning the logging slash would be accountable for the collection and 

transportation data while given credit for the electricity generated to avoid regional grid

electricity. Therefore, this LCA did not include any positive or negative environmental burdens

pertaining to logging slash. 
24

4.3.2 Resource Transportation

Transportation of redwood logs cut from the trees occurs by logging trucks. Logging trucks 

collect the redwood logs (127% MC) at the landing and transport the logs an average of 54 km to 

the sawmill log yard. No other material transported to the mill was greater than 1% of the mass 

of the incoming logs. Therefore, no other material transportation data besides logs were included 

in the LCA.

4.3.3 Product Production

Typical sources of energy consumed during the manufacturing process include thermal energy 

for kiln–drying the decking and electrical energy for log breakdown into decking and other coproducts.

4.3.3.1 Material Flow

Figure 3-7 illustrates the unit processes for redwood product manufacturing, starting with the log 

yard operations. Diesel logging trucks unload the redwood logs into the log yard. Log storage 

occurs year round although the log volume depends on the season. Sawmills typically stockpile 

logs during the dry season when logging conditions are optimal. Redwood mills track log 

volume to ensure there is an adequate volume of logs to keep the mill operating. Two of the four 

redwood mills surveyed sprinkle their logs with water to maintain freshness and keep the logs 

from checking and splitting. Fork lifts powered by diesel, gasoline, and propane (natural gas is a 

proxy) move the logs around the yard and to the sawmill for debarking and further processing. 

Bark comprises about 9.9% of the incoming log volume. After debarking, the log is sawn into 

rough lumber. The sawing process (minus the bark) produces rough green decking (59.9%), 

wood chips (22.7%), sawdust (9.5%), hog fuel (5.0%), and shavings (1.9%). The three 

processing options for rough green decking include 1) planing and selling as green decking 

(7.6%), 2) selling as is (28.4%), or 3) drying and selling as dried decking (64.0%).

Drying rough green decking usually occurs by first air-drying and then kiln-drying to reach the 

desired MC. Drying redwood decking lowers the total weight of the board. In addition, drying

reduces the volume of each board once the board dries below the fiber saturation point although 

the mass of wood per board stays constant. Sawmills have to consider wood shrinkage when 

sawing the logs into green lumber. The vast majority of redwood decking is sold as dry planed 

decking product (62.4%), whereas only 2.6% rough redwood decking is sold. 

As part of the process of confirming the data quality, a mass balance was performed and the 

results are summarized in Table 4-10. In performing the mass balance for redwood decking, all 

the unit processes located within the site system boundary were considered. Using a weightaveraged approach, 648 OD kg of incoming redwood logs with a green density (127% MC) of 

803 kg/m3produced 1.0 m3(380 OD kg) of planed redwood decking. The sawing process 

yielded 388 kg of rough green decking with no loss of wood substance occurring during the 

drying process. Planing the rough lumber into a surfaced decking product reduced the 388 OD kg 

of rough dry decking to 380 OD kg of planed dry redwood decking, for a 2% reduction in mass. 

Some of the wood waste was converted on-site to thermal energy in a boiler. Boilers burned all 8 

OD kg of dry shavings produced onsite for thermal process energy. Overall, an average log was 

reduced to 59% (380/648) of its original mass during its conversion to planed dry redwood 

decking. 
25

According to the North American PCR, if the mass/energy of a flow is less 1% of the cumulative 

mass/energy of the model flow it may be excluded, provided its environmental relevance is 

minor. This analysis included all energy and mass flows for primary data (FPInnovations 2011). 

Table 4-10: Mass balance of manufacturing redwood decking

Sawing 

process

Boiler 

process

Dryer process Planer process All processes 

combined

Material (OD kg) In Out In In Out In Out In Out E

Green logs (wood only) 648 — —S — — — — 648 0 –648

Green logs (bark only) 71 — — — — — — 71 0 –71

Green chips — 147 — — — — — 0 147 147

Green sawdust — 68 — — — — — 0 68 68

Green bark — 71 — — — — — 0 71 71

Green shaving — 12 — — — — — 0 12 12

Green hog fuel — 32 — — — — — 0 32 32

Rough green decking — 388 — 388 — — — 388 388 0

Rough dry decking — — — — 388 388 — 388 388 0

Planed dry decking — — — — — — 38010 380 380

Dry shavings — — 8 — — — 8 8 8 0

Sum 719 719 8 388 388 388 388 1503 1495 –8

1 Equal to one cubic meter of redwood decking.

4.3.3.2 Carbon Balance

Table 4-11 shows the carbon flow for redwood decking from carbon uptake during sequestration 

to production of the final product. As indicated, 262 kg CO2-eq/100ft2(738 kg CO2-eq/m3) was 

stored as carbon in the final product. In comparison, virgin and recycled WPC decking stored 

244 kg CO2-eq/100ft2as these products were 50% wood. As noted previously, WPC decking is 

substantially denser than redwood decking. Therefore, even though WPC decking is only 50% 

wood, WPC stores about the same value of carbon as redwood decking on a per functional area 

basis. As done for WPC decking, the carbon stored in redwood decking was given a 

characterization factor of –1 when calculating GWP. Carbon uptake was developed from the 

wood mass balance for a cubic meter of redwood decking provided in Table 4-109.

 

9

(648+71.5) kg wood in /m3redwood decking out × 0.53 kg C/kg wood × (44 kg CO2/kmole) ÷ (12 kg C/kmole) = 

1,398 kg CO2-eq/m3redwood decking out.
26

Table 4-11: Carbon balance of redwood decking

Carbon flows per unit of redwood decking made (kg CO2-eq/100 ft2)

1

(kg CO2-eq/m3)

Carbon uptake –495 –1398

Mill residue combusted on-site for on-site thermal energy 5 16

Mill residue leaving site and combusted for electricity (71%) 162 457

Mill residue leaving site and decayed as soil amendment (25%) 57 161

Mill residue leaving site and made into new wood product (4%) 9 26

Carbon stored in final product 262 738

Balance 0 0

1

0.354 m3 per 100 ft2redwood decking.

4.3.3.3 Energy Consumption

Redwood decking production required both electrical and thermal energy for processing the logs 

into the decking. For the four mills surveyed in this study, most thermal energy was produced 

onsite. However, some steam was produced nearby and piped to the mill. Electricity was 

obtained off-site from the combined NNWP/CAMX power grids (50/50). Electrical energy was 

required for the log yard operations, sawing, drying, and planing unit processes, whereas thermal 

energy was only used during the drying process.

Survey results showed that 222 MJ10 of unallocated process energy was consumed per cubic 

meter of redwood decking produced. The total unallocated electrical consumption, not including 

primary energy, was 91 kWh/m3of final product (Table 4-12). Primary energy refers to the 

energy embodied in natural resources such as fossil fuels in ground and biomass in trees before 

being converted into electricity or heat. For the log yard operations, sawing, drying and planing, 

the consumption of the grid electrical energy was 1.1%, 67.7%, 10.7%, and 20.5% of the total, 

respectively. Based on this breakdown, the four unit processes used 1.0, 61.9, 9.8, and 18.7 kWh 

of grid electricity per m3of redwood decking produced. The major sources of process energy 

were from the wood fuel generated onsite from the planing process, from natural gas, and from 

piped-in steam produced from burning wood biomass off-site. 

Total electrical energy consumption per cubic meter of redwood decking produced is comparable 

to the published western redcedar decking (Thuja plicata) value of 118 kWh/m3(Mahalle and 

O’Connor 2009). In addition, the electrical consumption for producing planed dry redwood 

decking was found to be similar to NE/NC United States softwood lumber where the value was 

99 kWh/m3(Bergman and Bowe 2010). These values do not include primary energy resources.

Table 4-13 tracked the ancillary material consumed during the decking manufacturing process 

and the amounts of these materials.

 

10 (8.05+1.86)OD kg wood*20.9MJ/OD kg wood+0.375 m3

natural gas*54.4 MJ/kg*0.705kg/m3=222 MJ/m3redwood decking.
27

Table 4-12: Material and energy consumed on-site to produce redwood decking (SimaPro input values). 

Includes fuel used for electricity production and for log and transportation (unallocated)

Fuel type Quantity SI Units per m3 Quantity Units per MBF1

Fossil fuel

Natural Gas20.375 m

3

0.023 1000 ft3

Electricity

Grid (eGrid) 91 kWh 158 kWh

On-site transportation fuel

Off-road diesel 2.43 L 15.9 Gal

Gasoline 0.36 L 2.3 Gal

Propane 0.10 L 0.6 Gal

Renewable fuel

On-site Wood Fuel28.05 Kg 30.7 Lb

Off-site Wood Fuel2, 31.86 Kg 7.1 Lb

Water use

Surface water 187 L 1220 Gal

Ground water 22 L 146 Gal

1

1.73 m3per 1.0 nominal thousand board feet planed redwood decking.

2 Energy values were found using their HHV in MJ/kg; 20.9 MJ wood oven-dried and 54.4 for natural gas. 

3 Wood boiler producing steam at a nearby facility.

Table 4-13: List of ancillary materials consumed during manufacturing

Ancillary materials (kg/m3) (lb/MBF1) Database

Hydraulic fluid 2.41E-01 9.16E-01 US-EI

Motor oil 6.63E-02 2.52E-01 US-EI

Grease 0.00E+00 0.00E+00 US-EI

Cardboard 1.21E-04 4.61E-04 US-EI

Plastic strapping 6.36E-02 2.42E-01 US LCI

Paint 2.12E-03 8.06E-03 US-EI

Potable water 1.81E+00 6.90E+00 US-EI

Replacement sticker 3.40E+00 1.30E+01 US LCI

1 MBF = thousand board feet.
28

5 Data Quality Summary

Data quality summary is listed in Table 5 1. Data quality relates to the actual scenario being 

studied. Therefore, primary data collected from industry ranks the highest with peer-reviewed 

studies ranking in the middle. In addition, data within LCI databases are typically peer-reviewed 

before being entered into the databases so is ranked as medium-high as the data were peerreviewed twice.

Table 5-1: Data quality summary for cradle-to-gate data

Decking Data source Data quality Comments

WPC Secondary (various sources) Medium From peer-reviewed study by 

Mahalle and O’Connor (2009) 

and industry sources listed in 

References

Redwood Primary data (surveys) High 100% allocated to decking

PVC Secondary (various sources) Medium From peer-reviewed study by 

Mahalle and O’Connor (2009) 

and industry sources listed in 

References

Energy/Ancillary

materials

Tertiary data (US LCI and US 

Ecoinvent Databases)

Medium-high

6 Installation and Use Phase Life-Cycle Inventories

This section covered the ancillary material requirements and processes involved in the 

installation, use, and maintenance of decking products throughout their service lives. The use of 

phase inventories accounted for all the material and energy inputs and processes associated with 

the final products leaving the mill gate and the installation, use, and maintenance. Since redwood 

decking is primarily used along the Pacific Coast, product transportation was modeled for two 

building site locations. One represented local markets in San Francisco, CA, and the second 

represented a more distant market in Seattle, WA. 

Installation specifications for all of the decking materials evaluated are shown in Table 6-1. It is 

assumed that a residential light-duty deck was installed according to the TimberTech, Trex, and 

CRA installation guidelines. As per these specifications, WPC, and PVC decking have the same 

joist spans and fastener specifications. The only major difference is the 24-inch joist space for 

the redwood deck versus 16 inches for the other decks. The joist spacing is increased because the 

redwood decking boards are thicker than the other products and have a higher strength that 

allows for wider joist spacing. Therefore, less structural lumber for the deck joists is required for 

the redwood deck per functional unit.
29

Table 6-1: Installation guidelines for the various decking materials

Decking 

material

Size of board

(mm)

Joist span

(mm)

Fasteners Gaps between boards and solid objects (e.g.,

wall)

WPC1 31 × 140 

(1.25 × 6 in) 400 (16 in)

62.5-mm (2.5 in-)

galvanized screws 

(no. 8 or 10)

Width-to-width – 6.25 mm (0.25 in)

End-to-end – 3.125 mm (0.125 in)

Abutting solid objects – 6.25 mm (0.25 in)

Redwood2 38 × 140 

(2 × 6 in) 600 (24 in) Same as WPC

Width-to-width – 4.69 mm (0.188 in)

End-to-end – flush

Abutting solid objects – flush

PVC3 25 × 140 

(1 × 6 in) 400 (16 in) Same as WPC

Width-to-width – 6.25 mm (0.25 in)

End-to-end – 4.69 mm (0.188 in)

Abutting solid objects – 6.25 mm (0.25 in)

1 Mahalle and O’Connor (2009) p. 37.

2

Personal communication 09/30/2011, Charlie Jourdain, President, California Redwood Association (CRA).

3

Personal communication 01/18/2012, Charlie Jourdain, President, CRA.

The decking installation and use phase LCI included the transportation of the decking from the 

production facility to the warehouses and then to the selected building sites. Also, the materials 

and energy used in the installation, use, and maintenance of the deck was considered. Energy 

used by the nail guns and drills during installation was assumed to be minor and was not 

included in the LCI. All decking materials were assumed to have similar cleaning guidelines. For 

example, washing the deck surface with a detergent and bleach to kill mold and mildew is 

suggested annually for all decking materials (Mahalle and O’Connor 2009; Trex 2013; 

TimberTech 2013). In addition, to maintain decking throughout its service life regardless of the 

decking material, the deck should have dirt and debris removed on a semiannual basis.

Based on the information considered, decking maintenance and installation procedures were 

similar enough between the different decking materials to disregard in performing the full LCA. 

Additionally, product transportation will likely substantially outweigh all other impacts for this 

stage. Other material attributes related to this life-cycle stage are shown below.

6.1 Polyvinyl Chloride 

6.1.1 Transport

PVC decking boards were made in a production facility located in Columbus, OH (TimberTech 

2013; EBN 2012). Diesel trains (80%) and diesel tractor-trailer (20%) were assumed to transport 

the PVC decking to distribution centers in San Francisco (3,800 km) and Seattle (3,800 km). 

Upon arrival at the distribution centers, single-unit trucks were assumed to transport the WPC 

deck boards an average of 20 km to the building sites for installation.

6.1.2 Use Phase Inputs

A 100 ft2- (9.29 m2-) PVC deck requires 211 lineal feet (64.3 m) of 4/4- (25 mm-) deck boards. 

In addition, a 2.3% material loss was assumed during installation (from trimming) and the waste 

material sent to a landfill for disposal. Like other large PVC decking manufacturers, TimberTech 

offers a limited lifetime warranty on their decking products. Therefore, in this study, a PVC deck 

had an expected service life of 25 years with proper care and maintenance.
30

6.2 Wood–Plastic Composite (virgin and recycled) 

6.2.1 Transport

WPC decking boards were made in a production facility located in Fernley, NV (Trex 2012). 

Diesel tractor-trailers were assumed to transport the decking to distribution centers located in 

San Francisco (400 km) and Seattle (1,200 km). Upon arrival at the distribution centers, singleunit trucks were assumed to transport the WPC deck boards an average of 20 km to building sites 

for installation.

6.2.2 Use Phase Inputs

A 100 ft2- (9.29 m2-) WPC deck requires 211 lineal feet (64.3 m) of 5/4 (31 mm) deck boards. In 

addition, a 2.3% material loss was assumed during installation (from trimming) and the waste 

material sent to a landfill for disposal. Like other large WPC decking manufacturers, Trex offers 

a 25-year warranty on their decking products. Therefore, in this study, a WPC deck had an 

expected service life of 25 years with proper care and maintenance.

6.3 Redwood 

6.3.1 Transport

Redwood decking was primarily used within the region of manufacture (U.S. West Coast),

unlike other decking materials. Therefore, the lower product transport distance resulted in a 

lower impact for this stage of the life-cycle analysis. From the survey data, weight-averaged 

product transportation distances were calculated for the green and dry redwood decking 

products. However, to facilitate the product comparison with other decking materials regarding 

San Francisco and Seattle, several assumptions were necessary.

For example, San Francisco lies on the southern end of the redwood timber range with the 

majority of redwood decking production occurring roughly 250 to 600 km away. Therefore, it 

was assumed that diesel tractor-trailers transported the redwood decking approximately 300 km 

to a distribution center. In the case of Seattle, diesel tractor-trailers were assumed to transport the 

redwood decking approximately 1,000 km to the distribution centers. The weight of the water 

found within the decking added additional burdens. Assuming green decking (34.6% of total 

volume) at 127% MC and dry decking (65.4% of total volume) at 19% MC, a weighted-average 

value of 56.4% MC was estimated and used in estimating the additional environmental impacts 

during decking transportation. Upon arrival at the distribution centers, diesel single-unit trucks 

were used to transport the redwood deck boards an average of 20 km to the building sites for 

installation.

6.3.2 Use Phase Inputs

A residential 100 ft2- (9.29 m2-) redwood deck requires 211 lineal feet (64.3 m) of nominal 2 × 6 

(38- × 140-mm) deck boards. In addition, because of redwood’s natural durability, no stains or 

preservatives were applied to the installed deck boards11. Therefore, it was assumed that redwood

deck boards were not stained and that they would develop a natural weathered appearance within 

several months. A 3% material loss was assumed during installation (from trimming) and the 

 

11 Personal communication 01/18/2012, Charlie Jourdain, President, California Redwood Association.
31

waste material was sent to a landfill for disposal (Mahalle and O’Connor 2009). With proper 

maintenance, redwood decking should last 25 years before decking boards would need to be 

replaced. 

7 End of life Phase

Final disposition of old deck boards had a substantial influence on the environmental impacts 

and the LCA, depending on the type of material from which the decking was manufactured. Prior 

to the introduction of WPC decking materials, wood decking was simply disposed of in a landfill 

and considered inert without any environmental impact once the material was in the landfill. 

Therefore, only transportation to the landfill and the energy to landfill the material needed to be 

considered.

In contrast, the present study assumed that, while the decking was disposed of in a landfill, the 

wood decking partially decomposed. Research has shown that a portion of the discarded wood 

decking (about 23%) breaks down anaerobically when stored in a landfill (Skog 2008). The 

wood decomposes into biogenic methane and biogenic carbon dioxide on a 50:50 molar ratio. As 

the biogenic methane, a potent greenhouse gas (GHG), rises to the surface of the landfill, 10% of 

the biogenic methane oxidizes into biogenic CO2. Therefore, the CH4:CO2 molar ratio at the 

landfill surface is 45:55.

To help mitigate climate change, it is desirable that biogenic methane, which is a much more

potent GHG than CO2, be captured and burned (i.e., flared). Additionally, energy may be 

recovered and is an added benefit as the landfill gas captured and burned avoids the production 

of natural gas for energy. EPA (2011) and Salazar and Meil (2009) provided the background 

calculations found in Appendix 16– Landfill Equations. Table 7-1 shows the GHG emission 

profile for the baseline scenario, a landfill with energy recovery.

Table 7-1: GHG emissions from wood landfilled with standard methane 

capture

GHG Emissions

kg GHG per OD 

kg wood

kg GHG per 100 ft2

(redwood)1

Methane, biogenic20.0180 2.43

Carbon dioxide, biogenic20.0605 8.17

Carbon dioxide, biogenic30.231 31.2

Carbon dioxide, biogenic40.0990 13.4

1

135 oven-dried kg redwood per 100 ft2.

2 Released directly into air.

3 Released after energy recovery (70%).

4 Release after flaring (30%) – energy not recovered.

Landfill gas (LFG) contains a considerable percentage of biogenic methane. Biogenic and fossil 

methane are the same chemically. Fossil methane is the primary component of natural gas. 

Therefore, LFG capture for energy production would offset some natural gas production. In this 

study, the avoided natural gas production due to the capture of LFG was estimated to be 0.054 kg 

(0.0753 m

3

) of natural gas production per OD kg of wood decomposing in the landfill, assuming 

a 23% decomposition rate and a 75% landfill methane capture of 0.1004 m

3

/OD kg at landfill 
32

surface (Salazar and Meil 2009). The remaining 25% of biogenic methane (0.018 kg/OD kg 

wood) was emitted directly into the atmosphere. So for the functional unit of 100 ft2of decking 

area (135 OD kg) of redwood decking sent to a landfill with methane capture, a total of 7.31 kg 

(10.2 m

3

) of natural gas production was avoided. To model the impact on redwood decking, 

cradle-to-gate production of natural gas at the plant was entered as an avoided product to account 

for the environmental impacts not occurring by using LFG instead.

All decking was assumed to be removed manually during the deconstruction of the deck. 

Therefore, the impact of removal was not included in the LCA. Both PVC and WPC decking 

products have no other impacts except transportation to the inert landfill and handling at landfill. 

8 Life-Cycle Impact Assessment

This section of the report covers the impact assessment of the life-cycle assessment. The LCI 

flows from the various decking materials provided the basis for the LCIA. The TRACI 2.1

Method data incorporated into SimaPro provided the framework for calculating the 

environmental mid-point categories listed in Section 3-6. The GWP profiles presented included

the carbon stored in the redwood and WPC decking products. The LCIA provided input for 

builders, architects, engineers, and designers on the various attributes of raw materials, product 

choices, and disposal methods. Learning the LCIA of a particular material allows stakeholders to 

make informed product choices based on science rather than anecdotal evidence, assuming that 

the LCIA analysis was transparent. 

The LCIA data provided in this report for the individual decking materials assumed that half the 

decks were built in San Francisco, CA, and the other half in Seattle, WA, the two most popular 

destinations for redwood decking. Redwood decking is generally used where it is manufactured,

which lowers its product transportation distance.

The first section showed the LCIAs for individual decking materials by the following stages: 1) 

cradle-to-gate manufacturing, 2) product transportation from production facility to customer, 3) 

use phase, and 4) removal of decking and disposal in a MSW landfill with methane capture. 

The second section provided overall decking numbers. The second section showed overall 

decking numbers assuming that half the decks were constructed in San Francisco and the other 

half in Seattle, WA. In addition, a sensitivity analysis was performed using mass allocation 

instead of the no allocation approach and the LCA results are shown in Section 9. Section 10 

highlighted the required cradle-to-gate LCA data for developing a business-to-business (B2B) 

EPD. Furthermore, a scenario analysis was completed using EOL values based on EPA (2006) 

and used in Mahalle and O’Connor (2009) study on western redcedar.

8.1 PVC Decking 

This study modeled the entire life cycle of PVC decking. PVC decking production required raw 

materials and generated emissions. SimaPro modeled the inputs provided in Section 4.1. 

Table 8-1 shows the impacts associated with building a 100 ft2- (9.29 m2-) deck. Table 8-2

indicates the same impacts converted to a cubic meter basis. These tables indicate that the 

greatest impacts occurred during the cradle-to-gate manufacturing process. Cumulated 

unallocated total energy consumption was 10,600 MJ/100 ft2(42,500 MJ/m

3

) with about 93%

(9,840/10,060) of the energy use associated with the cradle-to-gate manufacturing process. This 
33

result was consistent with the GWP as the cradle-to-gate manufacturing process generated 86% 

(368/426) of the total. The in-service use phase had a minimal impact on the LCA because the 

only inputs were derived from cleaning the deck semiannually. Biomass energy of 6.4 MJ/100 ft2

(27 MJ/m

3

) was attributable to grid electricity, less than 1% of total.

Table 8-1: Life-cycle impact assessment for 100 ft2(9.29 m2) of polyvinyl chloride decking

Impact category Unit

Cradleto-GateTransportation 

to customer

Use 

phase Landfill Total

Global warming kg CO2 eq 368 57.8 0.029 1 426

Ozone depletion kg CFC-11 eq 1.60E-05 2.25E-08 1.98E-09 3.66E-11 1.60E-05

Smog kg O3 eq 20.5 9.4 0.001 0.18 30.0

Acidification kg SO2 eq 4.32 0.29 0.00 0.01 4.61

Eutrophication kg N eq 0.088 0.020 0.000 0.000 0.108

Respiratory effects kg PM2.5 eq 0.270 0.006 0.000 0.000 0.276

Primary energy consumption Unit

Non-renewable fossil MJ 9378 783 1 7 10200

Non-renewable nuclear MJ 442 7 0 0 449

Renewable (solar, wind, 

hydroelectric, and 

geothermal)

MJ 15 1 0 0 15

Renewable, biomass MJ 6 0 0 0 6

Total primary energy MJ 9840 791 1 7 10600

Material resources 

consumption1 Unit

Non-renewable materials kg 157 0 0 0 157

Renewable materials kg 0 0 0 0 0

Fresh water L 4410 2 88 0 4500

Waste generated Unit

Solid waste kg 0.736 0.000 0.000 0.000 0.736

1 Non-fuel resources.
34

Table 8-2: Life-cycle impact assessment for 1 m3of polyvinyl chloride decking

Impact Category Unit 

Cradle-toGateTransportation to 

Customer Use Phase Landfill Total

Global warming kg CO2 eq 1560 245 0 2 1810

Ozone depletion kg CFC-11 eq 6.79E-05 2.25E-08 1.98E-09 3.66E-11 6.79E-05

Smog kg O3 eq 86.7 39.9 0.0 0.8 127

Acidification kg SO2 eq 18.3 1.2 0.0 0.0 19.6

Eutrophication kg N eq 0.371 0.084 0.001 0.001 0.457

Respiratory effects kg PM2.5 eq 1.144 0.026 0.000 0.000 1.17

Primary Energy Consumption Unit

Non-renewable fossil MJ 39700 3320 2 30 43100

Non-renewable nuclear MJ 1872 28 0 0 1900

Renewable (solar, wind, 

hydroelectric, and geothermal) MJ 62 3 0 0 65

Renewable, biomass MJ 27 0 0 0 27

Total primary energy MJ 41700 3350 3 30 45000

 Material resources

consumption1

Non-renewable materials kg 663 0 0 0 663

Renewable materials kg 0 0 0 0 0

Fresh water L 18700 9 370 0 19100

Waste generated Unit

Solid waste kg 3.12 0.00 0.00 0.00 3.12

1 Non-fuel resources.

Table 8-3 and Table 8-4 show the environmental performance of 100 ft2(9.29 m2) and 1 m3of

PVC decking from cradle-to-gate, respectively. The categories of material extraction and product 

production combine to form the cradle-to-gate LCIA shown in Tables 8-1 and 8-2. Additional 

information includes non-renewable and renewable materials that fall under the category 

“Material resources consumption (Non-fuel resources)”.
35

Table 8-3: Environmental performance of 100 ft2(9.29 m2) of polyvinyl chloride decking from cradle-to-gate

Impact category Unit Total

Forest carbon 

uptake Material extraction Product production

Global warming kg CO2 eq 368 0 285 83

Ozone depletion kg CFC-11 eq 1.60E-05 1.39E-05 2.12E-06

Smog kg O3 eq 20.5 14.91 5.54

Acidification kg SO2 eq 4.32 3.64 0.682

Eutrophication kg N eq 0.088 0.072 0.015

Primary energy consumption Unit

Non-renewable fossil MJ 9378 8249 1129

Non-renewable nuclear MJ 442 276 166

Renewable (solar, wind, 

hydroelectric, and 

geothermal)

MJ 14.6 12.4 2.3

Renewable, biomass MJ 6.26 3.04 3.21

Total primary energy MJ 9840 8540 1300

Material resources 

consumption1 Unit

Non-renewable materials kg 157 0 157

Renewable materials kg 0 0 0

Fresh water L 4410 1180 3230

Waste generated Unit

Solid waste kg 0.736 0.148 0.589

1 Non-fuel resources.

Table 8-4: Environmental performance of 1 m3of polyvinyl chloride decking from cradle-to-gate

Impact category Unit Total

Forest carbon 

uptake Material extraction Product production

Global warming kg CO2 eq 1560 0 1207 353

Ozone depletion kg CFC-11 eq 6.79E-05 5.89E-05 8.99E-06

Smog kg O3 eq 86.7 63.2 23.5

Acidification kg SO2 eq 18.3 15.4 2.9

Eutrophication kg N eq 0.371 0.307 0.064

Primary energy consumption Unit

Non-renewable fossil MJ 39737 34953 4784

Non-renewable nuclear MJ 1872 1170 703

Renewable (solar, wind, 

hydroelectric, and 

geothermal)

MJ 62 52 10

Renewable, biomass MJ 27 13 14

Total primary energy MJ 41700 36200 5510

Material resources 

consumption1 Unit

Non-renewable materials kg 663 0 633

Renewable materials kg 0 0 0

Fresh water L 18700 5000 13700

Waste generated Unit

Solid waste kg 3.12 0.625 2.495

1 Non-fuel resources.

8.2 WPC Decking 

This study modeled the entire life cycle of virgin and recycled WPC decking. The manufacturing 

process requires raw materials and generates emissions. SimaPro modeled the variable inputs 
36

specified in Section 4.2. Dry planer shavings left the softwood mill with no environmental 

burdens because softwood lumber was the primary product and to be consistent with treatment of

other wood residues in previous decking studies.

8.2.1 Virgin Wood–plastic Composite Decking

Table 8-5 shows the impacts generated for a 100 ft2- (9.29 m2-) area of deck, whereas Table 8-6

indicates the impacts converted to a cubic meter basis. The data presented in these tables 

demonstrate that the greatest impacts occurred during the cradle-to-gate manufacturing process. 

The cumulated unallocated total energy consumption was 14,700 MJ/100 ft2(53,000 MJ/m

3

) of 

deck with about 98% (14,400/14,700) of energy use associated with the cradle-to-gate 

manufacturing process. Carbon stored in the final product was 244 kg CO2/100 ft2(881 kg CO2-

eq/m3)

12

. This result was consistent with the GWP as the cradle-to-gate manufacturing process 

generated about 96% (486/508) of the total prior minus the carbon stored in the final product13. 

Including carbon storage lowered total GWP from 508 to 264 kg CO2-eq/100 ft2(950 kg CO2-

eq/m3), a reduction of 244 kg CO2-eq/100 ft2(881 kg CO2-eq/m3). The use phase had minimal 

impact on the LCIA because the only inputs in this phase came from cleaning the deck 

semiannually.

An interesting outcome of manufacturing the WPC decking in Nevada versus the East Coast was 

the large drop in fossil energy (i.e., diesel) use required. The main reason was that virgin WPC 

decking manufacturing occurred in Fernley, NV, versus previous studies with WPC decking 

manufacturing in the East. Therefore, significantly less product transportation occurred to 

provide virgin WPC decking to the west coast market.

Softwood sawmills use biomass energy to kiln-dry lumber before planing (Puettmann et al. 

2010). However, biomass energy shown of 9.0 MJ/100 ft3(32 MJ/m

3

) was attributable to the 

electric grid not to the wood portion of the WPC decking, the same as PVC decking. Planer 

shavings are the result of planing softwood lumber that is typically kilned dry (Puettmann et al. 

2010). However, in the present study, planer shavings produced at the softwood sawmill had no 

environmental burdens assign to them but do carry the inherent carbon found in all wood 

products.

 

12 267 kg per functional unit × 50% wood × 50% carbon × 44/12 = 244 kg CO2-eq.

13 244+242=486; 244+264=508.
37

Table 8-5: Life-cycle impact assessment for 100 ft2(9.29 m2) of virgin wood–plastic composite decking

Impact category Unit

Cradleto-GateTransportation 

to customer

Use 

phase Landfill Total

Global warming kg CO2 eq 242 20.8 0.029 1 264

Ozone depletion kg CFC-11 eq 1.36E-05 7.97E-10 1.98E-09 6.24E-11 1.37E-05

Smog kg O3 eq 32.6 3.4 0.001 0.31 36.3

Acidification kg SO2 eq 5.83 0.10 0.00 0.01 5.94

Eutrophication kg N eq 0.229 0.007 0.000 0.001 0.237

Respiratory effects kg PM2.5 eq 0.336 0.002 0.000 0.000 0.338

Primary energy consumption Unit

Non-renewable fossil MJ 13540 271 1 12 13800

Non-renewable nuclear MJ 236 2 0 0 238

Renewable (solar, wind, 

hydroelectric, and 

geothermal)

MJ 614 0 0 0 614

Renewable, biomass MJ 9 0 0 0 9

Total primary energy MJ 14400 273 1 12 14700

Material resources 

consumption1 Unit

Non-renewable materials kg 134 0 0 0 134

Renewable materials kg 133 0 0 0 0

Fresh water L 3270 0 88 0 3360

Waste generated U

Solid waste kg 0.070 0.000 0.000 0.000 0.070

1 Non-fuel resources.

Table 8-6: Life-cycle impact assessment for one m3of virgin wood–plastic composite decking

Impact category Unit

Cradleto-GateTransportation 

to customer

Use 

phase Landfill Total

Global warming kg CO2 eq 875 75 0 3 953

Ozone depletion kg CFC-11 eq 4.93E-05 2.25E-08 1.98E-09 3.66E-11 4.93E-05

Smog kg O3 eq 117.7 12.2 0.0 1.1 131

Acidification kg SO2 eq 21.0 0.4 0.0 0.0 21.5

Eutrophication kg N eq 0.828 0.025 0.001 0.002 0.856

Respiratory effects kg PM2.5 eq 1.212 0.008 0.000 0.001 1.22

Primary energy consumption Unit

Non-renewable fossil MJ 48900 980 2 44 50000

Non-renewable nuclear MJ 851 9 0 0 860

Renewable (solar, wind, 

hydroelectric, and 

geothermal)

MJ 2218 0 0 0 2218

Renewable, biomass MJ 32 0 0 0 32

Total primary energy MJ 52000 990 2 44 53100

Material resources 

consumption1 Unit

Non-renewable materials kg 482 0 0 0 482

Renewable materials kg 480 0 0 0 480

Fresh water L 11800 0 319 0 12100

Waste generated Unit

Solid waste kg 0.251 0.000 0.000 0.000 0.251

1 Non-fuel resources.

Table 8-7 and Table 8-8 show the environmental performance of 100 ft2(9.29 m2) and 1 m3of

virgin WPC decking from cradle-to-gate, respectively. The categories of forest carbon uptake, 
38

material extraction, and product production combine to form the cradle-to-gate LCIA shown in 

Tables 8-5 and 8-6. Additional information includes non-renewable and renewable materials that 

fall under the category “Material resources consumption (Non-fuel resources)”.

Table 8-7: Environmental performance of 100 ft2(9.29 m2) of virgin wood–plastic composite decking from 

cradle-to-gate

Impact category Unit Total

Forest carbon 

uptake

Material 

extraction

Product 

production

Global warming kg CO2 eq 242 –244 272 215

Ozone depletion kg CFC-11 eq 1.36E-05 1.27E-05 9.15E-07

Smog kg O3 eq 32.6 18.95 13.66

Acidification kg SO2 eq 5.83 4.02 1.806

Eutrophication kg N eq 0.229 0.203 0.027

Primary energy consumption Unit

Non-renewable fossil MJ 13540 10552 2988

Non-renewable nuclear MJ 236 100 135

Renewable (solar, wind, 

hydroelectric, and geothermal) MJ 614 18.7 595.7

Renewable, biomass MJ 8.9 5.9 3

Total primary energy MJ 14400 10700 3720

Material resources consumption1 Unit

Non-renewable materials kg 134 0 134

Renewable materials kg 133 0 133

Fresh water L 3270 2522 744

Waste generated Unit

Solid waste kg 0.070 0.070 0.000

1 Non-fuel resources.

Table 8-8: Environmental performance of 1 m3of virgin wood–plastic composite decking from cradle-to-gate

Impact category Unit Total

Forest carbon 

uptake

Material 

extraction

Product 

production

Global warming kg CO2 eq 874 –881 980 775

Ozone depletion kg CFC-11 eq 4.93E-05 4.60E-05 3.30E-06

Smog kg O3 eq 117.7 68.4 49.3

Acidification kg SO2 eq 21.0 14.5 6.5

Eutrophication kg N eq 0.828 0.732 0.097

Primary energy consumption Unit

Non-renewable fossil MJ 48879 38094 10786

Non-renewable nuclear MJ 851 362 489

Renewable (solar, wind, 

hydroelectric, and geothermal) MJ 2218 67 2150

Renewable, biomass MJ 32 21 11

Total primary energy MJ 52000 38600 13400

Material resources consumption1 Unit

Non-renewable materials Kg 482 0 482

Renewable materials Kg 480 0 480

Fresh water L 11800 9110 2690

Waste generated Unit

Solid waste Kg 0.251 0.251 0.000

1 Non-fuel resources.

8.2.2 Recycled WPC Decking

SimaPro was used to model the variable inputs listed in section 4.2. Table 8-9 shows the impacts 

generated from building 100 ft2(9.29 m2) of decking from recycled WPC while Table 8-10
39

demonstrates the impacts converted to a cubic meter basis. The tables show that the greatest 

impacts occurred during the cradle-to-gate manufacturing process. The cumulated unallocated

total energy consumption was 6,690 MJ/100 ft2(24,000 MJ/m

3

) with about 96% (6390/6690) of 

the energy use being attributed with the cradle-to-gate manufacturing process. Carbon stored in 

the final product was the same as virgin WPC decking at 244 kg CO2/100 ft2(964 kg CO2-

eq/m3). This result was consistent with the GWP as the cradle-to-gate manufacturing process 

generated about 94% (366/388) of the total outputs minus the carbon stored in the final product14. 

Including carbon storage lowered total GWP from 388 to 144 kg CO2-eq/100 ft2(510 kg CO2-

eq/m3), a reduction of 244 kg CO2-eq/100 ft2(881 kg CO2-eq/m3). The cumulative allocated 

energy was about 54%

15 lower than for the virgin WPC decking. The use phase had a minimal 

impact on the LCIA because the only inputs in this phase came from cleaning the deck 

semiannually. An in the previous case, manufacturing the recycled WPC decking in Nevada 

versus the East coast resulted in a large drop in the fossil energy use required to transport the 

decking material to the west coast.

Table 8-9: Life-cycle impact assessment for 100 ft2(9.29 m2) of recycled wood–plastic composite decking

Impact category Unit

Cradleto-GateTransportation 

to customer

Use 

phase Landfill Total

Global warming kg CO2 eq 122 20.8 0.029 1 144

Ozone depletion kg CFC-11 eq 1.16E-05 7.97E-10 1.98E-09 6.24E-11 1.16E-05

Smog kg O3 eq 24.8 3.4 0.001 0.31 28.5

Acidification kg SO2 eq 2.75 0.10 0.00 0.01 2.86

Eutrophication kg N eq 0.196 0.007 0.000 0.001 0.203

Respiratory effects kg PM2.5 eq 0.154 0.002 0.000 0.000 0.157

Primary energy consumption Unit

Non-renewable fossil MJ 5530 271 1 12 5820

Non-renewable nuclear MJ 166 2 0 0 168

Renewable (solar, wind, 

hydroelectric, and 

geothermal)

MJ 693 0 0 0 693

Renewable, biomass MJ 9 0 0 0 9

Total primary energy MJ 6400 273 1 12 6690

Material resources 

consumption1

Non-renewable materials kg 134 0 0 0 134

Renewable materials kg 133 0 0 0 133

Fresh water L 3350 0 88 0 3440

Waste generated Unit

Solid waste kg 8.60 0.00 0.00 0.00 8.60

1Non-fuel resources. 

 

14 122+244 = 366; 144+244 = 388.

15 

 

 

.
40

Table 8-10: Life-cycle impact assessment for one m3of recycled wood–plastic composite decking

Impact category Unit

Cradleto-GateTransportation 

to customer

Use 

phase Landfill Total

Global warming kg CO2 eq 441 75 0 3 519

Ozone depletion kg CFC-11 eq 4.18E-05 2.25E-08 1.98E-09 3.66E-11 4.18E-05

Smog kg O3 eq 89.4 12.2 0.0 1.1 103

Acidification kg SO2 eq 9.9 0.4 0.0 0.0 10.3

Eutrophication kg N eq 0.706 0.025 0.001 0.002 0.734

Respiratory effects kg PM2.5 eq 0.557 0.008 0.000 0.001 0.57

Primary energy consumption Unit

Non-renewable fossil MJ 20000 980 2 44 21100

Non-renewable nuclear MJ 598 9 0 0 610

Renewable (solar, wind, 

hydroelectric, and 

geothermal)

MJ 2502 0 0 0 2502

Renewable, biomass MJ 33 0 0 0 33

Total primary energy MJ 23100 990 2 44 24200

Material resources 

consumption1 Unit

Non-renewable materials kg 482 0 0 0 482

Renewable materials kg 480 0 0 0 480

Fresh water L 12100 0 320 0 12400

Waste generated Unit 441 75 0 3 519

Solid waste Kg 4.18E-05 2.25E-08 1.98E-09 3.66E-11 4.18E-05

1 Non-fuel resources.

Table 8-15 and Table 8-16 show the environmental performance of 100 ft2(9.29 m2) and 1 m3

of recycled WPC decking from cradle-to-gate, respectively. The categories of forest carbon 

uptake, material extraction, and product production combine to form the cradle-to-gate LCIA 

shown in Tables 8-9 and 8-10. Additional information includes non-renewable and renewable 

materials that fall under the category “Material resources consumption (Non-fuel resources)”.
41

Table 8-11: Environmental performance of 100 ft2(9.29 m2) of recycled wood–plastic composite decking 

from cradle-to-gate

Impact category Unit Total

Forest carbon 

uptake

Forestry 

operations

Wood 

production

Global warming kg CO2 eq 122 –244 151 215

Ozone depletion kg CFC-11 eq 1.16E-05 1.07E-05 9.15E-07

Smog kg O3 eq 24.8 11.12 13.66

Acidification kg SO2 eq 2.75 0.95 1.805

Eutrophication kg N eq 0.196 0.169 0.027

Primary energy consumption Unit

Non-renewable fossil MJ 5527 2540 2987

Non-renewable nuclear MJ 166 30 135

Renewable (solar, wind, 

hydroelectric, and geothermal) MJ 693 98 596

Renewable, biomass MJ 9 6 3

Total primary energy MJ 6390 2670 3720

Material resources consumption1 Unit

Non-renewable materials kg 134 0 134

Renewable materials kg 133 0 133

Fresh water L 3340 2600 740

Waste generated Unit

Solid waste kg 8.60 8.60 0.00

1 Non-fuel resources.

Table 8-12: Environmental performance of 1 m3of recycled wood–plastic composite decking from cradleto-gate

Impact category Unit Total

Forest carbon 

uptake

Forestry 

operations

Wood 

production

Global warming kg CO2 eq 441 –881 547 775

Ozone depletion kg CFC-11 eq 4.18E-05 3.85E-05 3.30E-06

Smog kg O3 eq 89.4 40.1 49.3

Acidification kg SO2 eq 9.9 3.4 6.5

Eutrophication kg N eq 0.706 0.610 0.097

Primary energy consumption Unit

Non-renewable fossil MJ 19953 9169 10784

Non-renewable nuclear MJ 598 109 489

Renewable (solar, wind, 

hydroelectric, and geothermal) MJ 2502 352 2150

Renewable, biomass MJ 33 23 11

Total primary energy MJ 23100 9640 13430

Material resources consumption1 Unit

Non-renewable materials kg 482 0 482

Renewable materials kg 480 0 480

Fresh water L 12100 9390 2670

Waste generated Unit

Solid waste kg 31.0 31.0 0.0

1 Non-fuel resources.

8.3 Redwood Decking 

To be consistent with the new North American wood PCR introduced in 2011, the LCIA did not 

include biogenic CO2 emissions and forest carbon uptake but did include carbon stored in the 

final product (FPInnovations 2011). For consistency, WPC decking products that stored carbon

were analyzed and reported in this study in the same manner. This section does not cover the 
42

specifications outlined in the North American Structural and Architectural Wood Products PCR. 

However, Section 10 did cover the necessary cradle-to-gate LCIA data specifications.

The SimaPro 7.3 program was used to model the input variables listed in Section 4.3 considering 

the above changes shows the impacts associated with building a 100-ft2(9.29-m

2

) deck, whereas

Table 8-14 displays the impacts generated on a cubic meter basis. The tables show that the 

greatest environmental impacts occurred during the cradle-to-gate manufacturing process that 

included redwood resource harvesting and product production. The cumulated unallocated total 

energy consumption was 447 MJ/100 ft2(1,270 MJ per m3) of deck with most of energy use 

associated with the cradle-to-gate manufacturing process. This indicates that the other cradle-togate LCI stages for both PVC and WPC decking products have a greater impact on energy use. 

During final disposition, the biogenic methane captured avoids natural gas production and the 

resultant reduction of 424 MJ/100 ft2of energy was substantial. The biomass energy contributes 

94 MJ/100 ft2of deck to the total energy balance. 

The low biomass energy associated with redwood decking was again counterintuitive in 

comparison to other wood products. The reason for this result was that minimal kiln-drying 

occurred during redwood decking manufacturing. Air-drying was the primary source of 

removing water from the redwood decking. Kiln–drying is the most energy-intensive unit 

process for producing lumber-type products (Simpson 1991; Bergman and Bowe 2008; 

Puettmann et al. 2010; Bergman and Bowe 2012). Additionally, redwood decking was kiln-dried 

after air-drying to less than 30% MC on the air yard. Biomass energy represents about 21% 

(94/447) of total energy used and the GWP value was negative, –163 kg CO2-eq/100 ft2(–460 kg 

CO2-eq/m3) because redwood decking stores the carbon sequestered by trees. Redwood decking 

stores carbon equivalent to 262 kg CO2/100 ft2(738 kg CO2/m3) while in-service. Therefore, 

when not considering carbon storage in the redwood decking while in-service, 98 kg CO2-eq/100 

ft2(278 kg CO2-eq/m3) of redwood decking was emitted over the full life cycle. This value 

includes the biogenic methane not captured from the landfills and subsequently emitted to the 

atmosphere (2.5 kg/100 ft2). As with all of the decking products considered, the use phase had a 

minimal impact on the LCIA because the only inputs come from cleaning the deck semiannually. 
43

Table 8-13: Life-cycle impact assessment for 100 ft2(9.29 m2) of redwood decking

Impact category Unit

Cradleto-GateTransportation 

to customer

Use 

phase Landfill Total

Global warming kg CO2 eq –229 14.6 0.029 52 -163

Ozone depletion kg CFC-11 eq 1.35E-06 5.57E-10 1.99E-09 3.62E-10 1.36E-06

Smog kg O3 eq 6.8 2.4 0.001 0.26 9.5

Acidification kg SO2 eq 0.33 0.07 0.00 -0.19 0.21

Eutrophication kg N eq 1.71E-02 4.87E-03 1.97E-04 –6.12E-04 2.16E-02

Respiratory effects kg PM2.5 eq 1.62E-02 1.53E-03 1.31E-05 –1.20E-02 5.74E-03

Primary energy consumption Unit

Non-renewable fossil MJ 504 198 1 –423 280

Non-renewable nuclear MJ 38 2 0 –1 39

Renewable (solar, wind, 

hydroelectric, and 

geothermal)

MJ 34 0 0 0 34

Renewable, biomass MJ 94 0 0 0 94

Total primary energy MJ 670 200 1 –424 447

Material resources 

consumption1 Unit

Non-renewable materials Kg 0.8 0 0 0 0.8

Renewable materials Kg 136 0 0 0 136

Fresh water L 140 0 89 0 229

Waste generated Unit

Solid waste kg 0.223 0.000 0.000 0.000 0.223

1 Non-fuel resources.

Table 8-14: Life-cycle impact assessment for one m3of redwood decking

Impact category Unit

Cradleto-GateTransportation 

to customer

Use 

phase Landfill Total

Global warming kg CO2 eq –648 41 0.08 147 –460

Ozone depletion kg CFC-11 eq 3.82E-06 1.57E-09 5.63E-09 1.02E-09 3.83E-06

Smog kg O3 eq 19.3 6.8 0.0 0.7 26.8

Acidification kg SO2 eq 0.92 0.21 0.00 –0.54 0.59

Eutrophication kg N eq 4.83E-02 1.38E-02 5.58E-04 –1.73E-03 6.09E-02

Respiratory effects kg PM2.5 eq 4.58E-02 4.31E-03 3.69E-05 –3.39E-02 1.62E-02

Primary energy consumption Unit

Non-renewable fossil MJ 1424 559 2 –1195 780

Non-renewable nuclear MJ 107 5 0 –3 109

Renewable (solar, wind, 

hydroelectric, and 

geothermal)

MJ 96 0 0 0 98

Renewable, biomass MJ 265 0 0 0 265

Total primary energy MJ 1892 564 2 –1197 1270

Material resources 

consumption1

Non-renewable materials kg 2 0 0 0 2

Renewable materials kg 383 0 0 0 383

Fresh water L 395 0 251 0 646

Waste generated Unit

Solid waste kg 0.629 0.000 0.000 0.000 0.629

1 Non-fuel resources.

Table 8-15 and Table 8-16 show the environmental performance of 100 ft2(9.29 m2) and 1 m3

of redwood decking from cradle-to-gate, respectively. The categories of forest carbon uptake, 
44

material extraction, and product production combine to form the cradle-to-grave LCIA shown in 

Tables 8-13 and 8-14. Additional information includes non-renewable and renewable materials 

that fall under the category “Material resources consumption (Non-fuel resources)”.

Table 8-15: Environmental performance of 100 ft2(9.29 m2) of redwood decking from cradle-to-gate

Impact category Unit Total

Forest carbon 

uptake

Forestry 

operations

Wood 

production

Global warming kg CO2 eq –229 –262 14.3 17.8

Ozone depletion kg CFC-11 eq 1.35E-06 2.46E-08 1.33E-06

Smog kg O3 eq 6.84 5.32 1.52

Acidification kg SO2 eq 0.326 0.158 0.168

Eutrophication kg N eq 1.71E-02 1.03E-02 6.80E-03

Primary energy consumption Unit

Non-renewable fossil MJ 504 208 296

Non-renewable nuclear MJ 38 2.1 35.8

Renewable (solar, wind, 

hydroelectric, and geothermal) MJ 34 0.52 33.5

Renewable, biomass MJ 94 0.00 93.8

Total primary energy MJ 670 211 459

Material resources consumption1 Unit

Non-renewable materials kg 0.77 0 0.77

Renewable materials kg 136 0 136

Fresh water L 140 27 113

Waste generated Unit

Solid waste kg 0.223 0.00 0.223

1 Non-fuel resources.

Table 8-16: Environmental performance of 1 m3of redwood decking from cradle-to-gate

Impact category Unit Total

Forest carbon 

uptake

Forestry 

operations

Wood 

production

Global warming kg CO2 eq –648 –738 40.3 49.2

Ozone depletion kg CFC-11 eq 3.82E-06 6.938E-08 3.754E-06

Smog kg O3 eq 19.3 15.0 4.3

Acidification kg SO2 eq 0.920 0.447 0.474

Eutrophication kg N eq 4.83E-02 2.912E-02 1.921E-02

Primary energy consumption Unit

Non-renewable fossil MJ 1424 589 835

Non-renewable nuclear MJ 107 6 101

Renewable (solar, wind, 

hydroelectric, and geothermal) MJ 96 1 95

Renewable, biomass MJ 265 0 265

Total primary energy MJ 1892 596 1296

Material resources consumption1 Unit

Non-renewable materials kg 2.18 0 2.18

Renewable materials kg 383 0 383

Fresh water L 395 77 318

Waste generated Unit

Solid waste kg 0.629 0.000 0.629

1 Non-fuel resources.
45

8.4 Overall LCIA – All Decking Products 

Figure 8-1 compares the six impact categories plus the cumulative energy consumption, fresh 

water consumption, material resources consumption, and solid waste generated for the four

decking products evaluated in the report on a percentage basis. Considerable differences existed

between the redwood decking and the other decking materials evaluated. Redwood decking 

product had negative GWP values while the other decking materials have positive GWP values. 

Figure 8-1: Life-cycle impact assessment for the four decking products by percentage

In addition, all other impact categories for redwood were less than 30% of the worst impact 

value reported. Reasons for the carbon benefit credited to the wood decking product was 

attributed to redwood decking lumber being primarily air-dried with only a minimal amount of 

kiln-drying being performed. Wood decking materials also stored the carbon that was originally 

absorbed by the growing tree as CO2 from the atmosphere. Both WPC decking products also 

stored carbon. Overall, redwood decking had substantially less environmental impact over the 

other decking products with the exceptions of biomass energy and renewable material 

-40%

-30%

-20%

-10%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Polyvinyl chloride Virgin wood plastic

composite

Recycled wood plastic

composite

Redwood

Global warming Ozone depletion

Smog Acidification

Eutrophication Respiratory effects

Non-renewable fossil Non-renewable nuclear

Renewable (solar, wind, hydroelectric, and geothermal) Renewable, biomass

Total primary energy Non-renewable materials

Renewable materials Fresh water

Solid Waste
46

consumption. With respect to the other decking products, recycled WPC decking materials have

the highest solid waste because of unusable waste during product manufacturing.

Table 8-17 shows the percentage values for the six impact categories plus cumulative energy, 

fresh water consumption, material resource consumption, and solid waste generated. Table 8-18

displays the numerical values for the six impact categories plus cumulative energy, fresh water 

consumption, material resource consumption, and solid waste generated per 100 ft2of deck. 

Table 8-19 shows the numerical values for the six impact categories plus cumulative energy, 

fresh water consumption, material resource consumption, and solid waste generated on a cubic 

meter basis.

PVC decking made the greatest contribution to GWP, ozone depletion, fresh water consumption, 

and non-renewable material resource consumption while virgin WPC decking had the highest 

smog, acidification, eutrophication, respiratory effects, and total primary energy. Recycled WPC 

had the highest solid waste production. As expected, redwood decking had the highest biomass 

energy consumption and renewable material resource consumption. Virgin and recycled WPC 

decking, however, nearly consumed as much renewable resources as redwood decking because 

these decking products were 50% wood. As previously mentioned, the biomass energy profile 

for redwood decking was low for a wood product, thereby not typical. In addition, GWP for 

redwood decking was negative as redwood decking stored the carbon while in service, which 

was originally sequestered by trees.

Table 8-17: Life-cycle impact assessment for four decking products by percentage per 100 ft2(9.29 m2)

Impact category

Polyvinyl

Chloride (%)

Virgin wood–plastic

composite (%)

Recycled wood–

plastic composite (%)

Redwood

(%)

Global warming 100 62 34 –38

Ozone depletion 100 85 72 8

Smog 83 100 78 26

Acidification 78 100 48 6

Eutrophication 46 100 86 9

Respiratory effects 82 100 46 2

Primary energy consumption

Non-renewable fossil 73 100 42 2

Non-renewable nuclear 100 53 37 9

Renewable (solar, wind, 

hydroelectric, and geothermal) 2 89 100 5

Renewable, biomass 7 10 10 100

Total primary energy 72 100 46 3

Material resources consumption1

Non-renewable materials 100 85 85 0

Renewable materials 0 98 98 100

Fresh water 100 75 76 5

Waste generated

Solid waste 9 1 100 3

1 Non-fuel resources.

Biomass energy consumption was higher for redwood decking than for the alternatives, as 

expected, because wood product production typically utilizes the wood residue generated during 
47

production as a fuel source. Regardless, total energy for redwood was substantially lower than 

the other decking products: 4.2% (447/10640) of PVC, 3.0% (447/14700) of virgin WPC and 

6.7% (447/6690) of recycled WPC. Captured biogenic methane from decomposing redwood 

decking in landfills to avoid natural gas production was 11.3 m3/100 ft2, approximately 433 

MJ/100 ft2of energy.

The other impact measures indicated the high consumption of both non-renewable and renewable 

material resources in the virgin and recycled WPC decking products. WPC decking products are

made of 50% polyethylene resins and 50% wood. In addition, WPC decking products are 

substantially heavier than the other decking products; therefore, these two products consume 

roughly the same as PVC in the non-renewable resource category and redwood decking in the 

renewable resource category.

Table 8-18: Life-cycle impact assessment for four decking products by value per 100 ft2(9.29 m2)

Impact category Unit

Polyvinyl

chloride

Virgin wood–

plastic composite

Recycled wood–

plastic composite Redwood

Global warming kg CO2 eq 426 264 144 -163

Ozone depletion kg CFC-11 eq 1.60E-05 1.37E-05 1.16E-05 1.36E-06

Smog kg O3 eq 30.0 36.3 28.5 9.5

Acidification kg SO2 eq 4.61 5.94 2.86 0.21

Eutrophication kg N eq 0.108 0.237 0.203 0.022

Respiratory effects kg PM2.5 eq 0.276 0.338 0.157 0.006

Primary energy consumption Unit

Non-renewable fossil MJ 10169 13840 5820 280

Non-renewable nuclear MJ 449 238 168 39

Renewable (solar, wind, 

hydroelectric, and geothermal) MJ 15 614 693 35

Renewable, biomass MJ 6 9 9 94

Total primary energy MJ 10600 14700 6690 447

Material resources 

consumption1 Unit

Non-renewable materials kg 157 134 134 0.8

Renewable materials kg 0 133 133 136

Fresh water L 4500 3360 3440 229

Waste generated Unit

Solid Waste kg 0.736 0.070 8.60 0.223

1 Non-fuel resources.
48

Table 8-19: Life-cycle impact assessment for four decking products by value per m3

Impact category Unit

Polyvinyl

chloride

Virgin wood–

plastic composite

Recycled wood–

plastic composite Redwood

Global warming kg CO2 eq 1810 953 519 –460

Ozone depletion kg CFC-11 eq 6.80E-05 4.93E-05 4.18E-05 3.83E-06

Smog kg O3 eq 127 131 103 27

Acidification kg SO2 eq 19.6 20.0 10.3 1.1

Eutrophication kg N eq 0.457 0.856 0.734 0.061

Respiratory effects kg PM2.5 eq 1.170 1.221 0.565 0.016

Primary energy consumption Unit

Non-renewable fossil MJ 43100 50000 21000 790

Non-renewable nuclear MJ 1900 860 610 110

Renewable (solar, wind, 

hydroelectric, and geothermal) MJ 65 2220 2500 98

Renewable, biomass MJ 27 32 33 265

Total primary energy MJ 45100 53100 24100 1260

Material resources 

consumption1 Unit

Non-renewable materials Kg 663 482 482 2

Renewable materials Kg 0 480 480 385

Fresh water L 19100 12100 12400 647

Waste generated Unit

Solid waste Kg 3.12 0.25 31.0 0.63

1 Non-fuel resources.

9 Sensitivity analysis—Mass Allocation

For the baseline scenario, redwood decking had 100% allocation of critical environmental 

impacts to the final product. To evaluate the significance of this original decision, a mass 

allocation was performed. The mass allocation only affected redwood decking as the other three 

alternatives had no co-products produced in conjunction with the decking. In essence, wood 

decking comprises 60% of the incoming log volume (wood only). If bark is considered, decking 

drops to 54.0%. Therefore, the following wood co-products produced as a direct result of sawing 

and planing were assigned positive and negative environmental attributes by mass: 

 Sawing unit process – green redwood products and co-products

o Decking (54.0%)

o Wood chips (20.4%)

o Sawdust (9.5%)

o Bark (9.9%)

o Shavings (1.7%)

o Hog fuel (4.5%)

 Planing unit process

o Planed (surface) dry decking (97.9%)

o Dried planer shavings (2.1%)

Figure 9-1 shows the six impact categories plus cumulative energy consumption, fresh water 

consumption, material resource consumption, and solid waste generated for the four decking 
49

products evaluated on a percentage basis. As expected, no changes occurred for PVC, virgin 

WPC, and recycled WPC decking. All changes in impacts concerned redwood decking because 

of the change in allocation. Redwood decking GWP decreased slightly from the mass allocation 

case to the (no allocation) base case. 

Figure 9-1: Life-cycle impact assessment for four decking products by percentage per 100 

ft

2

(9.29 m2) (Mass allocation).

Table 9-1 shows the percentage values for the six impact categories plus the cumulative energy, 

fresh water consumption, material resource consumption, and solid waste generated. Table 9-2

displays the numerical values for the six impact categories plus cumulative energy, fresh water 

consumption, material resource consumption, and solid waste generated per 100 ft2(9.29 m2) of 

deck. Table 9-3 shows the numerical values for the six impact categories plus cumulative 

energy, fresh water consumption, material resource consumption, and solid waste on a cubic 

meter basis. PVC decking had the highest contribution to GWP and ozone depletion while virgin 

WPC decking has the highest contribution for smog, acidification, eutrophication, respiratory 

-50%

-40%

-30%

-20%

-10%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Polyvinyl chloride Virgin wood plastic

composite

Recycled wood plastic

composite

Redwood

Global warming Ozone depletion

Smog Acidification

Eutrophication Respiratory effects

Non-renewable fossil Non-renewable nuclear

Renewable (solar, wind, hydroelectric, and geothermal) Renewable, biomass

Total primary energy Non-renewable materials

Renewable materials Fresh water

Solid Waste
50

effects, and fossil energy. The biomass energy profile was not typical for redwood decking 

because of the low bioenergy consumption compared to other wood products (Puettmann et al. 

2010). GWP decreased slightly to -175 kg CO2-eq/100 ft2for the mass allocation case from -163

for the (no allocation) base case.

The other impact measures indicated the high consumption of both non-renewable and renewable 

material resources in the virgin and recycled WPC decking products, about the same as the no

allocation case. WPC decking products are made of 50% polyethylene resins and 50% wood. In 

addition, WPC decking products are substantially heavier than the other decking products 

therefore these two products consume roughly the same as PVC in the non-renewable resource 

category and redwood decking in the renewable resource category.

Table 9-1: Life-cycle impact assessment for four decking products by percentage per 100 ft2(9.29 m2) (Mass 

allocation)

Impact category

Polyvinyl

Chloride (%)

Virgin wood–plastic

composite (%)

Recycled wood–

plastic composite (%)

Redwood

(%)

Global warming 100 62 34 –41

Ozone depletion 100 85 72 8

Smog 83 100 78 18

Acidification 78 100 48 1

Eutrophication 46 100 86 7

Respiratory effects 82 100 46 0

Primary energy consumption

Non—renewable fossil 73 100 42 1

Non—renewable nuclear 100 53 37 6

Renewable (solar, wind, 

hydroelectric, and geothermal) 2 89 100 3

Renewable, biomass 7 10 10 100

Total primary energy 72 100 46 3

Material resources consumption1

Non—renewable materials 100 85 85 0

Renewable materials 0 98 98 100

Fresh water 100 75 76 4

Waste generated

Solid waste 9 1 100 3

1 Non-fuel resources.
51

Table 9-2: Life-cycle impact assessment for four decking products per 100 ft2(9.29 m2) (Mass allocation)

Impact category Unit

Polyvinyl

chloride

Virgin wood–

plastic composite

Recycled wood–

plastic composite Redwood

Global warming kg CO2 eq 426 264 144 –175

Ozone depletion kg CFC-11 eq 1.60E-05 1.37E-05 1.16E-05 1.25E-06

Smog kg O3 eq 30.0 36.3 28.5 6.7

Acidification kg SO2 eq 4.61 5.94 2.86 0.09

Eutrophication kg N eq 0.108 0.237 0.203 0.016

Respiratory effects kg PM2.5 eq 0.276 0.338 0.157 0.001

Primary energy consumption Unit

Non-renewable fossil MJ 10169 13836 5823 94

Non-renewable nuclear MJ 449 238 168 27

Renewable (solar, wind, 

hydroelectric, and geothermal) MJ 15 614 693 24

Renewable, biomass MJ 6 9 9 86

Total primary energy MJ 10600 14700 6690 231

Material resources 

consumption1 Unit

Non-renewable materials kg 157 134 134 1

Renewable materials kg 0 133 133 138

Fresh water L 4500 3350 3430 189

Waste generated Unit

Solid Waste kg 0.736 0.070 8.60 0.220

1 Non-fuel resources.

Table 9-3: Life-cycle impact assessment for four decking products per m3(Mass allocation)

Impact category Unit

Polyvinyl

chloride

Virgin wood–

plastic composite

Recycled wood–

plastic composite Redwood

Global warming kg CO2 eq 1810 953 519 –493

Ozone depletion kg CFC-11 eq 6.80E-05 4.93E-05 4.18E-05 3.54E-06

Smog kg O3 eq 127 131 103 19

Acidification kg SO2 eq 19.6 20.0 10.3 0.25

Eutrophication kg N eq 0.457 0.856 0.734 0.045

Respiratory effects kg PM2.5 eq 1.17 1.221 0.565 0.004

Primary energy consumption Unit

Non-renewable fossil MJ 43100 49900 21000 267

Non-renewable nuclear MJ 1900 860 610 80

Renewable (solar, wind, 

hydroelectric, and geothermal) MJ 65 2220 2500 67

Renewable, biomass MJ 27 32 33 243

Total primary energy MJ 45100 53000 24100 657

Material resources 

consumption1 Unit

Non-renewable materials kg 663 482 482 2

Renewable materials kg 0 480 480 391

Fresh water L 19100 12100 12400 533

Waste generated Unit

Solid waste kg 3.12 0.25 31.0 0.62

1 Non-fuel resources.
52

Total energy for redwood decking when assigning environmental impacts by mass dropped 

substantially from the base case. Total primary energy of 231 MJ/100 ft2(657 MJ/m3) was found 

for the mass allocation, about a 50% drop from when allocating all environmental burdens to the 

final product and none to the wood residues.

10 Cradle-to-Gate Redwood Decking – Mass Allocation

In order for life-cycle assessments to meet the specifications outlined in the North American 

Structural and Architectural Wood Products product category rule (PCR), environmental burdens 

must be allocated on a mass basis (ISO 2006c; ISO 2007; FPInnovations 2011) unless co-product 

revenue differences exceed a 10:1 ratio in which case economic allocation should be used. In the 

case of redwood co-products, the revenue streams are similar and mass allocation is therefore 

used. 

Table 10-1 shows the environmental impact measures associated with building a 100 ft2- (9.29 

m

2

-) deck using a mass allocation basis. Table 10-2 displays the measures generated on a cubic 

meter basis on a mass allocation from cradle-to-grave. One cubic meter of redwood decking was 

the declared unit. The tables show that the greatest environmental impacts occurred during the 

cradle-to-gate manufacturing process that included redwood resource harvesting and product 

production. The cumulated unallocated total energy consumption was 282 MJ/100 ft2(800 

MJ/m

3

) of deck with most of energy use associated with the cradle-to-gate manufacturing 

process. During final disposition, the biogenic methane captured avoided natural gas production 

and the resultant reduction of 461 MJ/100 ft2(1303 MJ/m3) of energy was substantial. The 

biomass energy contributed 86 MJ/100 ft2(243 MJ/m3) of deck to the total energy balance. 

Table 10-1: Life-cycle impact assessment for 100 ft2(9.29 m

2

) of redwood decking (Mass allocation)

Impact category Unit

Cradleto-GateTransportation 

to customer

Use 

phase Landfill Total

Global warming kg CO2 eq –241 4.4 13.04 49 –175

Ozone depletion kg CFC-11 eq 1.25E-06 1.69E-10 2.49E-09 2.54E-10 1.25E-06

Smog kg O3 eq 4.0 0.7 2.274 -0.34 6.7

Acidification kg SO2 eq 0.20 0.02 0.07 -0.21 0.09

Eutrophication kg N eq 1.14E-02 1.48E-03 4.79E-03 –1.81E-03 1.58E-02

Respiratory effects kg PM2.5 eq 1.18E-02 4.64E-04 1.45E-03 –1.24E-02 1.38E-03

Primary energy consumption Unit

Non-renewable fossil MJ 319 59.9 177 –461 94.5

Non-renewable nuclear MJ 26 0.5 1.5 –1.2 26.6

Renewable (solar, wind, 

hydroelectric, and 

geothermal)

MJ 24 0 0 0 23.8

Renewable, biomass MJ 86 0 0 0 86.1

Total primary energy MJ 455 60 178 –462 231

Material resources 

consumption1

Non-renewable materials kg 1 0 0 0 1

Renewable materials kg 136 0 0 0 136

Fresh water L 99.59 0 88.85 0 188

Waste generated Unit

Solid waste kg 0.220 0.000 0.000 0.000 0.220

1 Non-fuel resources.
53

Table 10-2: Life-cycle impact assessment for one m3of redwood decking (Mass allocation)

Impact category Unit

Cradleto-GateTransportation 

to customer

Use 

phase Landfill Total

Global warming kg CO2 eq -681 12 36.85 139 -493

Ozone depletion kg CFC-11 eq 3.53E-06 4.76E-10 7.03E-09 7.17E-10 3.54E-06

Smog kg O3 eq 11.3 2.1 6.4 -1.0 18.8

Acidification kg SO2 eq 0.58 0.06 0.20 -0.59 0.25

Eutrophication kg N eq 3.21E-02 4.18E-03 1.35E-02 -5.11E-03 4.47E-02

Respiratory effects kg PM2.5 eq 3.34E-02 1.31E-03 4.09E-03 -3.50E-02 3.89E-03

Primary energy consumption Unit

Non-renewable fossil MJ 901 169 500 –1303 267

Non-renewable nuclear MJ 73 2 4 –4 75

Renewable (solar, wind, 

hydroelectric, and 

geothermal)

MJ 67 0 0 1 68

Renewable, biomass MJ 243 0 0 0 243

Total primary energy MJ 1284 171 504 –1306 653

Material resources 

consumption1

Non-renewable materials kg 2.2 0 0 0 2.2

Renewable materials kg 383 0 0 0 383

Fresh water L 281 0 251 0 532

Waste generated Unit

Solid waste kg 0.623 0.000 0.000 0.000 0.623

1

Non-fuel resources.

Table 10-3 and Table 10-4 show the environmental performance of 100 ft2(9.29 m2) and 1 m3

of redwood decking from cradle-to-gate including carbon stored in the final product, 

respectively. Forestry operations and wood production were derived from the cradle-to-gate 

LCIA shown in Tables 10-1 and 10-2. When compared to the environmental performance of 

redwood decking shown in Table 8-15, assigning environmental impacts by mass allocation 

lowers all of the environmental impact measures categorized in the present study as those 

burdens are allocated to chips and other co-products.
54

Table 10-3: Environmental performance of 100 ft2(9.29 m2) of redwood decking from cradle-to-gate 

(Mass allocation)

Impact category Unit Total

Forest carbon 

uptake

Forestry 

operations

Wood 

production

Global warming kg CO2 eq –241 –262 14.2 6.6

Ozone depletion kg CFC-11 eq 1.25E-06 1.25E-07 1.13E-06

Smog kg O3 eq 4.01 3.27 0.74

Acidification kg SO2 eq 0.204 0.141 0.063

Eutrophication kg N eq 1.14E-02 6.66E-03 4.72E-03

Primary energy consumption Unit

Non-renewable fossil MJ 319 215 104

Non-renewable nuclear MJ 26 14.1 11.7

Renewable (solar, wind, 

hydroelectric, and geothermal) MJ 24 12.61 11.0

Renewable, biomass MJ 86 9.30 76.8

Total primary energy MJ 455 251 204

Material resources consumption1 Unit

Non-renewable materials kg 0.77 0.00 0.77

Renewable materials kg 136 0 136

Fresh water L 100 47 53

Waste generated Unit

Solid waste kg 0.221 0.004 0.217

1 Non-fuel resources.

Table 10-4: Environmental performance of 1 m3of redwood decking from cradle-to-gate (Mass allocation)

Impact category Unit Total

Forest carbon 

uptake

Forestry 

operations

Wood 

production

Global warming kg CO2 eq –687 –738 40.1 10.9

Ozone depletion kg CFC-11 eq 3.53E-06 3.533E-07 3.182E-06

Smog kg O3 eq 11.3 9.3 2.1

Acidification kg SO2 eq 0.577 0.398 0.179

Eutrophication kg N eq 3.21E-02 1.881E-02 1.333E-02

Primary energy consumption Unit

Non-renewable fossil MJ 901 606 295

Non-renewable nuclear MJ 73 40 33

Renewable (solar, wind, 

hydroelectric, and geothermal) MJ 67 36 31

Renewable, biomass MJ 243 26 217

Total primary energy MJ 1290 708 580

Material resources consumption1 Unit

Non-renewable materials kg 2.2 0.0 2.2

Renewable materials kg 385 0 385

Fresh water L 281 132 149

Waste generated Unit

Solid waste kg 0.623 0.011 0.612

1 Non-fuel resources.

Scenario Analyses: end-of-life values from EPA (2006) data

The present LCA study conducted a sensitivity analysis assuming values from a wood LCA 

study conducted by Mahalle and O’Connor (2009) using EPA (2006) information. The 

assumptions are as follows: 1) wood decomposition rate, 23%, 2) methane capture equipment 

installed, 59%, 3) average capture efficiency, 75%, 4) energy recovery, 53% and 5) energy 

content of LFG, 0.54 MJ/m3.
55

Figure 11-1 shows the six impact categories plus cumulative energy consumption, fresh water 

consumption, material resource consumption, and solid waste generated for the four decking 

products evaluated on a percentage basis. The only environmental impacts change occurred to 

the redwood decking and then only minimal changes occurred.

Figure 11-1: Life-cycle impact assessment for all decking by percentage (EPA 2006)

Table 11-1 shows the percentage values for the six impact categories plus the cumulative 

energy, fresh water consumption, material resource consumption, and solid waste generated. 

Table 11-2 describes the LCIA for a functional unit of decking. As expected, the changes 

occurred in redwood decking because only redwood decking decomposed in the landfill. The 

GWP value using EPA (2006) data (–164 kg CO2-eq) was only slightly less than the GWP value 

estimated from the base case (–163 kg CO2-eq) shown in Table 8-13. Table 11-2 displays the 

numerical values for the six impact categories plus cumulative energy, fresh water consumption, 

material resource consumption, and solid waste generated per 100 ft2of deck. Table 11-3 shows 

-40%

-30%

-20%

-10%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Polyvinyl chloride Virgin wood plastic

composite

Recycled wood plastic

composite

Redwood

Global warming Ozone depletion

Smog Acidification

Eutrophication Respiratory effects

Non-renewable fossil Non-renewable nuclear

Renewable (solar, wind, hydroelectric, and geothermal) Renewable, biomass

Total primary energy Non-renewable materials

Renewable materials Fresh water

Solid Waste
56

the numerical values for the six impact categories plus cumulative energy, fresh water 

consumption, material resource consumption, and solid waste on a cubic meter basis. PVC 

decking had the highest contribution to ozone depletion and GWP, while virgin WPC decking 

has the highest contribution for smog, acidification, eutrophication, respiratory effects, and fossil 

energy. Only biomass energy consumed was higher for redwood decking than for any other 

product.

Table 11-1: Life-cycle impact assessment for four decking products by percentage per 100 ft2(9.29 m2) 

(EPA 2006)

Impact category

Polyvinyl

Chloride (%)

Virgin wood–plastic

composite (%)

Recycled wood–

plastic composite (%)

Redwood

(%)

Global warming 100 62 34 –38

Ozone depletion 100 85 72 8

Smog 83 100 78 26

Acidification 78 100 48 6

Eutrophication 46 100 86 9

Respiratory effects 82 100 46 4

Primary energy consumption

Non-renewable fossil 73 100 42 4

Non-renewable nuclear 100 53 37 9

Renewable (solar, wind, 

hydroelectric, and geothermal) 2 89 100 5

Renewable, biomass 7 10 10 100

Total primary energy 72 100 46 5

Material resources consumption1

Non-renewable materials 100 85 85 0

Renewable materials 0 98 98 100

Fresh water 100 75 76 5

Waste generated

Solid waste 9 1 100 3

1 Non-fuel resources.
57

Table 11-2: Life-cycle impact assessment for four decking products per 100 ft2(EPA 2006)

Impact category Unit

Polyvinyl

Chloride

Virgin wood–

plastic composite

Recycled wood–

plastic composite Redwood

Global warming kg CO2 eq 426 264 144 –164

Ozone depletion kg CFC-11 eq 1.60E-05 1.37E-05 1.16E-05 1.36E-06

Smog kg O3 eq 30.0 36.3 28.5 9.6

Acidification kg SO2 eq 4.61 5.94 2.86 0.35

Eutrophication kg N eq 0.108 0.237 0.203 0.022

Respiratory effects kg PM2.5 eq 0.276 0.338 0.157 0.014

Primary energy consumption Unit

Non-renewable fossil MJ 10169 13836 5823 583

Non-renewable nuclear MJ 449 238 168 40

Renewable (solar, wind, 

hydroelectric, and geothermal) MJ 15 614 693 35

Renewable, biomass MJ 6 9 9 94

Total primary energy MJ 10600 14700 6694 752

Material resources 

consumption1 Unit

Non-renewable materials kg 157 134 134 0.8

Renewable materials kg 0 133 133 136

Fresh water L 4500 3360 3440 229

Waste generated Unit

Solid Waste kg 0.736 0.070 8.60 0.223

1 Non-fuel resources.

Table 11-3: Life-cycle impact assessment for four decking products per m3(EPA 2006)

Impact category Unit

Polyvinyl

Chloride

Virgin wood–

plastic composite

Recycled wood–

plastic composite Redwood

Global warming kg CO2 eq 1810 953 519 –463

Ozone depletion kg CFC-11 eq 6.80E-05 4.93E-05 4.18E-05 3.83E-06

Smog kg O3 eq 127 131 103 27

Acidification kg SO2 eq 19.6 20.0 10.3 1.0

Eutrophication kg N eq 0.457 0.856 0.734 0.063

Respiratory effects kg PM2.5 eq 1.170 1.221 0.565 0.040

Primary energy consumption Unit

Non-renewable fossil MJ 43100 49900 21000 1646

Non-renewable nuclear MJ 1900 860 610 110

Renewable (solar, wind, 

hydroelectric, and geothermal) MJ 65 2220 2500 98

Renewable, biomass MJ 27 32 33 265

Total primary energy MJ 45100 53000 24100 2120

Material resources 

consumption1 Unit

Non-renewable materials kg 663 482 482 2

Renewable materials kg 0 480 480 385

Fresh water L 19100 12100 12400 647

Waste generated Unit

Solid waste kg 3.12 0.25 31.0 0.63

1 Non-fuel resources.
58

11 Conclusions and Recommendations

Based on the LCA developed for the four decking products, the following conclusions can be

made. As shown by its negative GWP, the amount of carbon stored in redwood decking exceeds 

the total GHG emissions emitted during its whole life cycle. Other building products have this 

significant environmental advantage of storing carbon while in use to offset the impacts from 

making them: likewise the wood content of WPC products reduces their GWP burden relative to 

those products that have no carbon storage potential in the body of the product itself. The uptake

of carbon dioxide from the atmosphere into the raw materials (i.e., trees) to make wood products 

and then storing the resultant carbon is a critical environmental benefit.

The substantial lower values across all six critical impact categories for redwood decking show 

its lower environmental footprint relative to alternative decking materials. Other life-cycle 

studies have shown similar results for wood products (Lippke et al. 2004; Werner and Richter 

2007) relative to other building products with substantial fossil fuel inputs. 

Less kiln–drying of wood products requires less energy consumption and creates lower 

environmental impacts. For alternative decking products, cradle-to-gate manufacturing consumes

nine times more primary energy than is consumed for redwood decking. As shown by the present 

study and others (Milota et al. 2005; Puettmann and Wilson 2005), using wood products in the 

green form (i.e., not dried) suggest considerably lower environmental impact than kiln–drying

wood to the desired MC. Utilizing less energy-intensive methods of drying wood in place of 

heated kilns can result in huge reductions in environmental impact.

A trade-off exists between landfilling old wood products and capturing the biogenic methane to 

avoid natural gas production. Capturing biogenic methane from decomposing wood avoids 

natural gas production which is a substantial environmental benefit for low-energy intensive 

wood products. If the methane is released it contributes to GWP, an environmental cost.

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63

13 Appendix: Forest Resources Module Survey

The California Redwood Association (CRA) is sponsoring a research project designed to 

evaluate the environmental impacts associated with the manufacture, consumption, disposal, and 

re-use of redwood as a decking material in comparison to wood–plastic composites. The 

objective of this project is to provide a transparent, scientifically verified, non-biased assessment 

which allows consumers to compare the environmental impacts between these two products. 

This assessment can be used to develop marketing strategies aimed at correcting misperceptions 

about the environmental impact of wood as a building material through a “cradle-to-grave” (raw 

material extraction to waste disposal) analysis. 

This study is conducted by the Consortium for Research on Renewable Industrial Materials 

(CORRIM) which is a non-profit research consortium with members from 16 universities and 

research institutions. Analyses will determine redwood decking’s contribution to cumulative 

energy consumption, air pollution, water pollution, solid waste pollution, and climate change 

relative to competing decking products. The project is broken into three interconnected modules 

that collectively provide the CRA with the necessary elements to support environmental claims 

in their marketing efforts: 1) market assessment, 2) forest resources, and 3) manufacturing 

process.

The forest resources module will describe typical harvest activities reflecting the costs and 

burdens associated with supplying logs for processing by redwood decking manufacturers. Other 

objectives of the module include development of representative data describing forest 

management and harvest activities associated with the growth, removal, and reestablishment 

specific to the redwood forest types. Within the questionnaire we will be asking questions on 

stand establishment, harvesting system and productivity. 

We would greatly appreciate it if you could complete and return the questionnaire at your earliest 

convenience. Any information that you provide will be kept strictly confidential, and will only 

be released as a summary where no individual’s answers can be identified. The information 

collected from this survey will be destroyed upon completion of the study. Of course, if you have 

any questions, please contact us at the address or phone numbers shown below. 

Sincerely,

Elaine Oneil, Ph.D. Han-Sup Han, Ph.D.

Executive Director, CORRIM Professor, Forest Operations and Engineering

School of Forest Resources Department of Forestry and Wildland Resources

University of Washington Humboldt State University

Seattle, WA 98195 Arcata, CA 95521

Phone:206-543-8684 Phone: 707-826-3725

Email: eoneil@u.washington.edu Email: hh30@humboldt.edu
64

Part I. Stand Establishment and Forest Inventory

1. Planting production rates and seedling types

 Seedling type: Bare root __________ Container _____________ 1.0 / 2.0 / other

 Planting rates (trees/day-planter):___________________________

 Trees/acre:_____________________________________________

 Number crew/transport vehicle: ___________________________________

 Average distance to planting site (miles): ____________________

2. Detail on stand establishment and yield is used to identify the inputs and outputs necessary to 

produce the per acre yield typically removed from redwood forests. The yield figures are 

then used to determine emission profiles per unit of wood volume. 

Silviculture System Volume 

removed 

per 

entry/acre

Rotation or 

re-entry 

period 

(years)

Volume 

remaining 

post 

harvest/acre

Site Prep

Y/Na

Planting

Y/N TPAb

Type (%) area or 

volume

(circle which)

Clearcut

Partial cut

Coppice

Shelterwood

Seed tree

Other

a

Eight slash treatment types are listed on Page 14

b

TPA: trees per acre

3. Please indicate “Yes” or “No” as applicable to your company and provide additional details 

where applicable.

Treatment Y/N # entries/ 

rotation

Comments

Fertilization (fertilizer mix and application rate/acre)

Precommercial 

Thinning

Equipment 

type

Production rates 

(ac/day) per person 

or machine

#people or 

machines

TPA 

removed/ 

final density
65

Part II. Harvesting Systems and Productivity

1. Please estimate your company’s redwood harvest in 2010.

Sawtimber: ______________ MBF/acre and/or ______________ Cubic feet/acre

 Clearcut:_________ MBF/acre; Thinning ____________ MBF/acre

Other products from the redwood harvest areas: specify them if any: (e.g. non-redwood 

sawtimber or biomass for energy)

_____________________: ______________ MBF/acre and/or ______________ Cubic feet/acre

 Clearcut:___________ MBF/acre; Thinning ___________MBF/acre

2. Please provide average values for harvested trees

DBH ________inches; Total height _________feet; Utilization limit (top diameter) 

________inches

Utilized log length: Minimum__________ ft; Maximum: _____________ft

3. Please estimate the percentage volume of redwood harvest that originated from each land 

ownership group. Total = 100%

Company lands________%; Other private lands________%; State_________% 

Federal________%; Tribal lands________%

4. What are typical external skidding/yarding distances (average distance between a landing and a 

harvest unit boundary)?

Skidding ____________ ft; Shoveling ____________ ft; Skyline ____________ ft 

Helicopter ___________ft: Other ___________ ft (specify:_______________________) 

Other __________ ft (specify:___________________________________)

5. Please list equipment used and estimate the percentage of their use for the following operations, 

manual (using a chainsaw) versus mechanized based on your annual harvest volume. Total = 

100%

Harvesting 

Operation

Manual Mechanized

Equipment used Equipment used Total

Clearcut

Felling Chainsaw % % 100%

Limbing/Bucking Chainsaw % % 100%

Thinning/Selection

Felling

Chainsaw % % 100%

Limbing/Bucking Chainsaw % % 100%

6. Please list harvesting equipment options and systems that are commonly used to harvest redwood 

and estimate an annual harvest volume (%) using each harvesting system in your company.
66

--- Clearcut ---

Harvesting 

System

Harvesting Phase Harvest 

Volume

/year

Felling Primary 

transport*

Processing Loading

Ground-based system

%

%

%

%

%

Skyline yarding system

%

%

%

%

Helicopter yarding system

%

%

%

Others (please specify)

%

%

%

%

Total timber harvest volume per year from clearcut 100%

*Primary transport: transporting logs or whole trees from the stump to landing or roadside

7. Please list harvesting equipment options and systems that are commonly used to harvest redwood 

and estimate an annual harvest volume (%) using each harvesting system in your company.
67

--- Commercial Thinning ---

Harvesting 

System

Harvesting Phase Harvest 

Volume

/year

Felling Primary 

transport*

Processing Loading

Ground-based system

%

%

%

%

%

Skyline yarding system

%

%

%

%

Helicopter yarding system

%

%

%

Others (please specify)

%

%

%

%

Total timber harvest volume per year from commercial thinning 100%

*Primary transport: transporting logs or whole trees from the stump to landing or roadside
68

Harvesting Machine Specifications

Please fill the table with your best estimates. You ONLY need to provide information for 

equipment options that are commonly used in your harvesting operations.

Felling

Note:

 Type of Machine: make multiple listings of the same machine type if the same type of 

machine but with different size/horsepower is used.

 Machine Size/Description: horsepower and small/medium/large

 Potential Production Rate (MBF/hour): felling only. Alternatively, daily production 

(MBF/day) may be provided along with the number of hours/day of working.

 Hourly Machine Cost ($/hour): this includes fixed costs (e.g. depreciation, insurance,...) and 

operating costs (e.g. fuels, repair/maintenance,...), but does not include the operator’s wages.

 Labor Cost ($/hour): Labor includes base labor rate plus fringe benefits.

 Machine Efficiency (%): amount of time that a machine is actually used to produce timber 

per day or hour, excluding machine warming up, breaks, fueling, downtime, etc.

 Fuel Consumption (gal/hour): this may be estimated based on the total amount of fuel used 

per day divided by the total number hours per day in a typical operation.

TYPE OF 

MACHINE

Machine Size 

/Horsepower 

/Description

Potential 

Production 

Rate

(MBF/hour)

Hourly 

Machine 

Cost

($/hour)

Labor 

Cost

($/hour)

Machine 

Efficiency

(%)

Fuel use

(gal/hour)

Clearcut

Chainsaw 

Feller-Buncher

(Other: specify)

(Other: specify)

Thinning

Chainsaw 

Feller-Buncher

(Other: specify)

(Other: specify)
69

Processing

Note:

 Type of Machine: make multiple listings of the same machine type if the same type of 

machine but with different size/horsepower is used.

 Machine Size/Description: horsepower and small/medium/large

 Potential Production Rate (MBF/hour): Processing only. Alternatively, daily production 

(MBF/day) may be provided along with the number of hours/day of working.

 Hourly Machine Cost ($/hour): this includes fixed costs (e.g. depreciation, insurance,...) and 

operating costs (e.g. fuels, repair/maintenance,...), but does not include the operator’s wages.

 Labor Cost ($/hour): Labor includes base labor rate plus fringe benefits.

 Machine Efficiency (%): amount of time that a machine is actually used to produce timber 

per day or hour, excluding machine warming up, breaks, fueling, downtime, etc.

 Fuel Consumption (gal/hour): this may be estimated based on teh total amount of fuel used 

per day divided by the total number hours per day in a typical operation.

TYPE OF 

MACHINE

Machine 

Size/ 

Horsepower

/Description

Potential 

Production 

Rate

(MBF/hour)

Hourly 

Machine 

Cost

($/hour)

Labor 

Cost

($/hour)

Machine 

Efficiency

(%)

Fuel use

(gal/hour)

Clearcut

Chainsaw 

processing

Stroke-boom 

delimber

Dangle-head 

processor

Other (specify): 

Other (specify):

Thinning

Chainsaw 

processing

Stroke-boom 

delimber

Dangle-head 

processor

Other (specify): 

Other (specify): 
70

Ground Skidding and Forwarding Equipment: Clearcut

Note:

 Type of Machine: make multiple listings of the same machine type if the same type of 

machine but with different size/horsepower is used.

 Machine Size/Description: horsepower and small/medium/large

 Potential Production Rate (MBF/hour): stump to landing (primary transport). Alternatively, 

daily production (MBF/day) may be provided along with the number of hours/day of 

working. 

 Hourly Machine Cost ($/hour): this includes fixed costs (e.g. depreciation, insurance,...) and 

operating costs (e.g. fuels, repair/maintenance,...), but does not include the operator’s wages.

 Labor Cost ($/hour): Labor includes base labor rate plus fringe benefits.

 Machine Efficiency (%): amount of time that a machine is actually used to produce timber 

per day or hour, excluding machine warming up, breaks, fueling, downtime, etc.

 Fuel Consumption (gal/hour): this may be estimated based on the total amount of fuel used 

per day divided by the total number hours per day in a typical operation.

TYPE OF 

MACHINE

Machine 

Size / 

Horsepower 

/Description

Potential 

Production 

Rate

(MBF/hour)

Hourly 

Machine 

Cost

($/hour)

Labor 

Cost

($/hour)

Machine 

Efficiency

(%)

Fuel use

(gal/hour)

Wheeled Skidders

Skidder

Tracked Skidders

Crawler 

Shovels

Shovel

Others: Please specify
71

Ground Skidding and Forwarding Equipment: Thinning

Note:

 Type of Machine: make multiple listings of the same machine type if the same type of 

machine but with different size/horsepower is used.

 Machine Size/Description: horsepower and small/medium/large

 Potential Production Rate (MBF/hour): stump to landing (primary transport). Alternatively, 

daily production (MBF/day) may be provided along with the number of hours/day of 

working.

 Hourly Machine Cost ($/hour): this includes fixed costs (e.g. depreciation, insurance,...) and 

operating costs (e.g. fuels, repair/maintenance,...), but does not include the operator’s wages.

 Labor Cost ($/hour): Labor includes base labor rate plus fringe benefits.

 Machine Efficiency (%): amount of time that a machine is actually used to produce timber 

per day or hour, excluding machine warming up, breaks, fueling, downtime, etc.

 Fuel Consumption (gal/hour): this may be estimated based on the total amount of fuel used 

per day divided by the total number hours per day in a typical operation.

TYPE OF 

MACHINE

Machine 

Size / 

Horsepower 

/Description

Potential 

Production 

Rate

(MBF/hour)

Hourly 

Machine 

Cost

($/hour)

Labor 

Cost

($/hour)

Machine 

Efficiency

(%)

Fuel use

(gal/hour)

Wheeled Skidders

Skidder

Tracked Skidders

Crawler 

Shovels

Shovel

Others: Please specify
72

Cable and Aerial Yarding Equipment: Clearcut

Note:

 Type of Machine: make multiple listings of the same machine type if the same type of 

machine but with different size/horsepower is used.

 Machine Size/Description: horse power, yarder tower height, maximum external payload 

capacity for helicopter (small/medium/large) 

 Potential Production Rate (MBF/hour): stump to landing (primary transport). Alternatively, 

daily production (MBF/day) may be provided along with the number of hours/day of 

working.

 Hourly Machine Cost ($/hour): this includes fixed costs (e.g. depreciation, insurance,...) and 

operating costs (e.g. fuels, repair/maintenance,...), but does not include the operator’s wages.

 Labor Cost ($/hour): Labor includes base labor rate plus fringe benefits for all yarding crew

(yarder operator, loader operator if any, landing crew, rigging crew, choker setters).

 Machine Efficiency (%): amount of time that a machine is actually used to produce timber 

per day or hour, excluding machine warming up, breaks, fueling, downtime, etc.

 Fuel Consumption (gal/hour): this may be estimated based on the total amount of fuel used 

per day divided by the total number hours per day in a typical operation.

TYPE OF 

MACHINE

Machine 

Size / 

Horsepower 

/Description

Potential 

Production 

Rate

(MBF/hour)

Hourly 

Machine 

Cost

($/hour)

Labor 

Cost

($/hour)

Machine 

Efficiency

(%)

Fuel use

(gal/hour)

Skyline

Skyline yarder

Helicopters

Helicopter

Others: Please specify
73

Cable and Aerial Yarding Equipment: Thinning

Note:

 Type of Machine: make multiple listings of the same machine type if the same type of 

machine but with different size/horsepower is used.

 Machine Size/Description: horse power, yarder tower height, maximum external payload 

capacity for helicopter (small/medium/large) 

 Potential Production Rate (MBF/hour): stump to landing (primary transport). Alternatively, 

daily production (MBF/day) may be provided along with the number of hours/day of 

working.

 Hourly Machine Cost ($/hour): this includes fixed costs (e.g. depreciation, insurance,...) and 

operating costs (e.g. fuels, repair/maintenance,...), but does not include the operator’s wages.

 Labor Cost ($/hour): Labor includes base labor rate plus fringe benefits for all yarding crew

(yarder operator, loader operator if any, landing crew, rigging crew, choker setters).

 Machine Efficiency (%): amount of time that a machine is actually used to produce timber 

per day or hour, excluding machine warming up, breaks, fueling, downtime, etc.

 Fuel Consumption (gal/hour): this may be estimated based on the total amount of fuel used 

per day divided by the total number hours per day in a typical operation.

TYPE OF 

MACHINE

Machine 

Size / 

Horsepower 

/Description

Potential 

Production 

Rate

(MBF/hour)

Hourly 

Machine 

Cost

($/hour)

Labor 

Cost

($/hour)

Machine 

Efficiency

(%)

Fuel use

(gal/hour)

Skyline

Skyline yarder

Helicopters

Helicopter

Others: Please specify
74

Sawlog Loading Equipment

Note:

 Type of Machine: make multiple listings of the same machine type if the same type of 

machine but with different size/horsepower is used.

 Machine Size/Description: horse power and clearcut only, thinning only, or both.

 Potential Production Rate (MBF/hour): sawlog loading productivity. Alternatively, daily 

production (MBF/day) may be provided along with the number of hours/day of working.

 Hourly Machine Cost ($/hour): this includes fixed costs (e.g. depreciation, insurance,...) and 

operating costs (e.g. fuels, repair/maintenance,...), but does not include the operator’s wages.

 Labor Cost ($/hour): Labor includes base labor rate plus fringe benefits.

 Machine Efficiency (%): amount of time that a machine is actually used to produce timber 

per day or hour, excluding machine warming up, breaks, fueling, downtime, etc.

 Fuel Consumption (gal/hour): this may be estimated based on the total amount of fuel used 

per day divided by the total number hours per day in a typical operation.

Move-in/Move-out Equipment

 Low-beds (or low-boys) are commonly used to bring logging and biomass recovery 

equipment to harvesting sites. Please provide you best estimates.

TYPE OF 

MACHINE

Machine 

Size / 

Horsepower 

/Description

Potential 

Production 

Rate

(MBF/hour)

Hourly 

Machine 

Cost

($/hour)

Labor 

Cost

($/hour)

Machine 

Efficiency

(%)

Fuel use

(gal/hour)

Loading

Loader

TYPE OF 

MACHINE

Machine 

Size

(horse 

power)

Loading/ 

Unloading 

time

(min./trip)

Hourly 

Machine 

Cost

($/hour)

Labor 

Cost

($/hour)

Average 

Round-Trip 

Time

(min./machine)

Fuel use

(gal/hour)

Move-in/Move-out – Logging and Biomass Recovery Equipment

Low-bed

Other (specify):
75

PART III. LOG TRANSPORTATION

Hauling distances and average speeds by forest road type

Road Type Mileage (one-way distance)

(miles)

Average Truck Speed

(miles/hour)

Spur 

1- or 2-lane 

dirt road

1- or 2-lane 

gravel road

2-lane highway

Interstate 

freeway

 Spur: Unimproved temporary dirt spur within harvest unit.

 1 or 2-lane dirt road: Single or double lane seasonal dirt road primarily constructed with 

native soils.

 1 or 2-lane gravel road: Single or double lane permanent road primarily surfaced with gravel.

 2-lane highway: Local highway paved with asphalt or concrete.

TYPE OF 

MACHINE

(Trucks)

Machine Size

(horse power)

Average 

Load 

(MBF/trip)

Hourly 

Machine 

Cost

($/hour)

Labor 

Cost

($/hour)

Loading/ 

Unloading 

time

(minutes)

Fuel use

(gal/hour)
76

PART IV. SLASH TREATMENTS

Please indicate “Yes” or “No” to each “treatment types (0 thru 8)” and “fill out” the table 

below based on descriptions on the slash treatment types.

Descriptions on eight slash treatment types:

Treatment 

type

Slash Treatment description Yes No

0 No slash disposal conducted

1 Whole tree harvest operation with piling at landing

2 Whole tree harvest operation with piling at landing and piling 

in woods

3 Whole tree harvest operation with piling at landing and 

broadcast burn

4 Bole-only harvest operation with piling in woods

5 Bole-only harvest operation with broadcast burn

6 Processing of biomass piled at landing

7 Recovery and processing of biomass left in the woods

8 Processing biomass at landing PLUS recovery of biomass in 

woods

Logging system used to 

harvest sawlogs

Slash treatment type Biomass recovery system if slash is 

recovered (select letter(s) from the 

Note)

Ground-based

Skyline Yarding

Helicopter Yarding

Note:

A. Biomass from Landing Slash Direct to Mill 

B. Biomass from Landing through Intermediate Load Site (Concentration Yard)

C. Biomass Recovery across Harvest Units through Intermediate Load Site

Indicate only those that apply for your slash treatment type or N/A if not 

applicable %

Percent of cut stem utilized (net out decay and breakage)

Percent of residue delivered to landing

Percent of residue delivered to landing recovered

Percent of residue piled in woods in whole tree

Percent of wood piled in woods or recovered in bole only

Percent of dry wood consumed in pile burning

Percent of dry wood consumed in broadcast burn
77

V. BIOMASS RECOVERY EQUIPMENT - Production Units in Green Ton (GT)

Please provide names in general term (no make/model) of biomass recovery equipment and systems 

that are commonly used to utilize forest residues left from redwood sawlog harvesting or other forest 

management activities (e.g. precommercial thinning) and estimate an annual recovery volume (%) 

using each recovery system in your company. Total = 100%

 Biomass from Landing Slash Direct to Mill

Biomass Operations Phase Biomass 

harvest 

/year

Loading Grinding or Chipping Loading (if 

needed)

%

%

 Biomass from Landing through Intermediate Load Site (Concentration Yard)

Biomass Operations Phase Biomass 

harvest 

/year

Loading Pre-hauling Grinding or Chipping at a 

centralized processing site

Loading (if 

needed)

%

%

 Biomass Recovery across Harvest Units through Intermediate Load Site

Biomass Operations Phase Biomass 

harvest 

/year

Loading Pre-hauling Grinding or Chipping at a 

centralized processing site

Loading

%

%

 What is moisture content (%) measured when slash is ground or chipped? ____________%

 What is a total amount of biomass harvesting from the redwood-dominant forests in 2010? 

________________ ton or ft3
78

Biomass Harvesting Productivity and Cost

Please list names of machine types if the machines listed in the table below are different from the 

machines that are commonly used in your biomass operations. Please be sure to include machine 

description and horsepower information.

Note: 

 On site grinding: landing slash will be ground at landing or roadside near or at landings. No 

pre-hauling or compiling of slash using modified dump truck, roll-on/off container or hooklift trucks is performed.

 Centralized grinding: a grinder is located in a centralized grinding location where logging 

slash and sub-merchantable size whole trees are compiled using modified dump truck, rollon/off container or hook-lift trucks.

TYPE OF 

MACHINE

Machine 

Size / 

Horsepower 

/Description

Potential 

Production 

Rate (ton or 

yd3/hour)

Hourly 

Machine 

Cost

($/hour)

Labor 

Cost

($/hour)

Machine 

Efficiency

(%)

Fuel use

(gal/hour)

Processing Equipment

On-site horizontal 

grinder 

Centralized 

horizontal grinder

Small whole tree 

chipper 

Medium whole 

tree chipper

Large whole tree 

chipper

Other:

Loading - Piling Equipment

Loader for

Pre-hauling 

Loader for 

feeding biomass

Front-end loader

Other:
79

Biomass Transportation

Please list names of machine types if the trucks listed in the table below are different from the 

machines that are commonly used to haul biomass fuels from a grinding location to energy 

plants/sawmills. Please be sure to include machine description and horsepower information.

Note:

 When a centralized grinding is used, end-dump trailers, modified dump truck, roll-on/off, and 

hook-lift truck to deliver slash from harvesting sites and landings to a centralized grinding 

location. 

Hauling distances and average speeds of chip vans by forest road types

Road Type Mileage (one-way distance)

(miles)

Average Chip Van Speed

(miles/hour)

Spur 

1- or 2-lane 

with no rocks

1- or 2-lane 

gravel

2 lane highway

Interstate

TYPE OF 

MACHINE

Truck 

Capacity

(green tons 

or yd3/trip)

Average 

Load 

(ton/trip)

Hourly

Machine 

Cost

($/hour)

Labor 

Cost

($/hour)

Loading/ 

Unloading 

time

(minutes)

Fuel use

(gal/hour)

Chip van 

(140 yd3)

Chip van 

(120 yd3)

Dump truckmodified

End-dump trailer

Roll-off or 

Hook-lift truck

Other:

Other:
80

14 Appendix: Product Manufacturing Module Survey

Thank you for giving us the opportunity to work with you on a project involving the long-term 

viability and profitability of the U.S. wood products industry. Results from this project will be an 

excellent marketing tool for the redwood decking industry particularly in the green building 

industry. A growing demand for building projects that use products with lower environmental 

burdens and energy-efficient materials has spurred a green movement in the construction 

industry. 

As a member of the U.S. forest products industry, you know that using wood is a sensible choice 

because wood is renewable and often poses fewer burdens to the environment than substitute 

materials. Many consumers do not understand this. With your input, we can test the theory that 

redwood decking poses less negative impacts to the environment than substitute materials such 

as plastic decking do. Completed projects of this type have shown other wood products to be a 

sustainable and sound environmental choice over product alternatives. 

This questionnaire focuses on annual production, annual energy use and generation, annual 

material inputs and outputs, and annual environmental emissions for redwood decking 

manufactured in California. Regarding the questionnaire, our focus is on process information 

because this data is vital for precise and accurate results. Details harder to report may be 

requested later. We realize that you may not have all the information requested, but the data you 

are able to provide will be appreciated. Strict confidentiality will be maintained for all 

companies that supply data. The focus of the project is 2x6 decking.

Company Name: _________________________________

Facility Address: _________________________________

_________________________________

Contact Person: _________________________________

Telephone: ( ) Fax: ( )_______

Contact email: _________________________________

Please direct questions and send complete questionnaires to:

Rick Bergman

USDA FS Forest Products Laboratory

One Gifford Pinchot Dr

Madison, WI 53726-2398

Phone (608) 231-9477 / Fax (608) 231-9508 

Email: rbergman@fs.fed.us
81

PART I: OPERATION OVERVIEW

GENERAL INFORMATION (Please provide responses for all requested information)

Reporting Year: ________ Starting Month: ________ Ending Month: ________

Log scale: Doyle, International, Scribner, Weight basis (circle one)

How many days did your mill operate for the selected reporting year? _________Days/Year

How many production shifts per day for the selected reporting year? __________Shifts/Day

Does your mill have the following:

log storage 

dry deck

sprinkled deck

pond

other: _______________

log handling

log sorter/merchandizer

debarker

sawmill

head rig(s): how many:_____ 

band saw: how many:_____

circular saw: how many:_____

resaws: how many:______

edgers: how many:______

edger optimizer

trimmer optimizer 

trimmer

sorter, # bins:______

sticker stacker

dryers and kilns

air–drying yard: Capacity_________

conventional steam: Capacity________

high temperature steam: Capacity________

direct-fired: Capacity________

dehumidification: Capacity________

transfer car system: Capacity________

boiler

wood-fired boiler

gas-fired boiler (natural or propane)

oil-fired boiler

cogeneration facility (electricity)

bag house

planers

planer

in-line moisture meter

grading station

trimmer

end paint/seal

other mill equipment
82

PART II: TOTAL MILL MATERIAL & ENERGY INPUTS & OUTPUTS

Average log diameter: ____________ inches 

Range of log diameter: ______to______ inches

Average log length: ______________feet

Volume of incoming logs during the reporting year: _____________ thousand bf

Volume of logs sold to outside firms during the reporting year: _________ thousand bf

Volume of logs sent to your sawmill during the reporting year: ________ thousand bf

Please complete the following table to provide your facilities annual lumber/decking production 

levels for the reporting year by product size. Please add more rows if necessary. Note – only 

report rough green lumber production by size for products when sold or transferred from your 

facility. We will be completing a mass balance (logs in vs. lumber/decking and co-products out) 

for your mill, so we first need to know your lumber production – so if it leaves your facility, we 

need to track it. We provided an example in the table of a mill that produces annually 60 million 

bf of nominal 2x6s. The numbers for 2x6 decking are the focus of this project but we need values 

for the other sizes to determine the mass balance accurately.

ANNUAL MILL PRODUCTION

Nominal 

Lumber 

Size

MMbf for 

reporting 

yr.

SurfacedGreen 

(MC=30%)1

Rough-Dry 

(MC=15%)1

SurfacedDry 

(MC=15%)1

Rough Green 

(Sold or 

transferred only) 

(MC=30%)1

Price

($/Mbf)

Percentage

(%)

2x6 e.g. 45 X, MC=35% e.g.600 75%

2x6 e.g. 10 X, MC=19% e.g.700 16.7%

2x6 e.g. 5 X, MC=19% e.g.900 8.3%

Total e.g. 60 e.g.45 e.g. 10 e.g. 5 e.g.640 100%

Please complete for your mill below (add more rows if required)

1x4

1x4

1x4

5/4x6

5/4x6

5/4x6

2x4

2x4

2x4

2x6

2x6

2x6

1 Change MC as appropriate More rows on next sheet (over)
83

Nominal 

Lumber 

Size

MMBF for 

reporting 

yr.

SurfacedGreen 

(MC=30%)1

Rough-Dry 

(MC=15%)1

SurfacedDry 

(MC=15%)1

Rough Green (Sold 

or transferred only) 

(MC=30%)1

Price

($/MBF)

Percentage

(%)

2x8

2x8

2x8

2x10

2x10

2x10

2x12

2x12

2x12

2x14

2x14

2x14

4x4

4x4

4x4

4x6

4x6

4x6

4x8

4x8

4x8

Other

Other

Other

Other

Other

Other

Total 100%

1 Change MC as appropriate 

ANNUAL RESOURCE TRANSPORTATION DATA: (transporting material to and 

from your sawmill)

Material

No. of 

deliveries

Average net 

weight of 

load (tons)

Average oneway distance 

(miles)

Transportation type

(choose one)

Percent 

empty 

backhaul

Logs Rail/Trucking

Purchased wood fuel (if any) Rail/Trucking

2x6 redwood decking Rail/Trucking

Boiler Chemicals Small/Large Truck
84

For each of the co-products produced at your plant, please indicate the weight (tons) of annual 

production for the reporting period that are shipped to other users, used internally as fuel or for 

the production of another co-product at your facility, stockpiled for future use or land filled 

(estimates are acceptable). If zero, enter a dash (-). Please state units if other than tons like cubic 

yards. The final column (Total Quantity) should equal the sum of the individual rows.

Estimate amount of wood residue produced per thousand bf of redwood decking _____tons/Mbf

Co-products and 

By-Products

Moisture

Content

(wet 

basis)

Sold 

(Shipped)

Used 

Internally

(as fuel)

Used 

Internally

(other 

uses)

Landfill Inventory Total

Quantity

(%) tons tons tons tons tons tons

Chips, green

Sawdust, green

Bark, green

Edging strips, green

Shavings, green

Hogged material, 

green

Sawdust, dry

Shavings, dry 

Hogged material, 

dry

Other

If you have installed emission control devices at your mill, please list them by type and the 

equipment controlled by the device.

Boiler #1 Boiler #2 Sawmill Dry Kiln Planermill Logyard

Type of Device

Equipment controlled

Electrical Use1, kWh

Type of emissions 

controlled

Are you processing material from other facilities (e.g. kiln–drying lumber or planing rough green

or kiln–dried lumber from other mills)?

_________Yes; ___________No;
85

If Yes, please specify the quantity per process for the selected reporting year:

Kiln–drying lumber from other mills (MMbf/yr) _______

Planing rough green lumber from other mills (MMbf/yr) _______

Planing kiln-dried lumber from other mills (MMbf/yr) _______

Short description of redwood decking production process:

The sawmill complex is divided into six process units: (1) log yard, (2) sawing, (3) drying, (4) 

planing, (5) boiler or co-generation equipment (energy generation) and (6) emission control (if 

applicable)

- Log yard includes all log handling from receiving logs at mill gate up to breakdown of the log

- Sawing includes the breakdown of the logs into rough green lumber.

- Drying includes stickering , the dry kilns, loading area, and unloading (storage) and air yards.

- Planing includes the unstacker, planer, and packaging areas. Each of these includes 

transportation to the next unit process or plant gate.

- Boiler/co-generation equipment (energy generation) includes fuel storage, transportation, 

boiler, turbines and steam distribution system.

ANNUAL TRANSPORTATION FUEL USE ON-SITE (includes all fuels for yard equipment, 

forklifts, and carriers)

Type

Total

Quantity

Percent of total by unit process (percentage or volume)

Log yard Sawing Drying Planing Boiler/Co-gen Units

Off-road diesel Gallons

Fuel Oil #6 Gallons

Propane Gallons

Gasoline Gallons

Electricity kWh

Other

ANNUAL BOILER FUEL AND ELECTRICTY USE: (boilers, cogeneration units, etc.)

Boiler Fuel Total Quantity Units

Moisture content 

(if applicable)

Wood

Wood boiler fuel produced on-site Tons

Purchased wood boiler fuel Tons

Fossil Fuel 

Natural Gas Thousand ft3

Fuel oil #1(kerosene) Gallons

Fuel oil #2 (heating oil) Gallons

Fuel oil #6 Gallons

Propane Gallons

Electricity for entire facility kWh

Other
86

ANNUAL ELECTRICITY USE (Estimation by percentage or number is ok)

Process kWh % of total

1. Log yard

2. Sawing

3. Kiln–drying

4. Planing

5. Boiler/Co-generation

Total 100%

ANNUAL WATER USE

Type

Total

Quantity

Percent of total by unit process (percentage or volume)

Log yard Sawing Drying Planing Boiler/Co-gen Units

Input

Surface water Gallons

Groundwater Gallons

Municipal water Gallons

Output

Water discharged Gallons

Water recycled Gallons

What percent of water is recycled? ________%

ANNUAL ANCILLARY MATERIALS

Type

Total

Quantity

Percent of total by unit process (percentage or volume)

Log yard Sawing Drying Planing Boiler/Co-gen Units

Hydraulic Fluid Gallons

Motor Oils Gallons

Greases Pounds

Gasoline Gallons

Steel strapping Pounds

Plastic strapping Pounds

Paint Gallons

Corrugated cardboard Pounds

Replacement stickers Pounds

ANNUAL INDUSTRIAL (SOLID) WASTE (material requiring disposal outside of mill)

Type Pounds Percent Landfilled

Pallets (not re-used)

Fly Ash

Bottom ash

General refuse (do not include above materials)

Recycled material

Other
87

ANNUAL AIR EMISSIONS: (Provide stack test if available)

Type

Total

Quantity

Percent of total by unit process (percentage or volume)

Log yard Sawing Drying Planing Boiler/Co-gen Units

Dust Pounds

Total Particulate Pounds

PM2.5 Pounds

PM10 Pounds

Carbon monoxide (CO) Pounds

Carbon dioxide (CO2) Pounds

Acetone Pounds

Acetaldehyde Pounds

Formaldehyde Pounds

Hazardous Air Pollutants 

(HAPS) Pounds

Methanol Pounds

Nitrous oxides (NOx) Pounds

Phenol Pounds

Propionaldehyde Pounds

Sulfur dioxide (SO2) Pounds

Total VOCs Pounds

Others (please list all 

known): Pounds

Other Pounds

Other Pounds

Other Pounds

Other Pounds

ANNUAL BOILER CHEMICALS

Boiler Chemicals Total Quantity Units

Oxygen scavenger

Name____________ Gallons

Corrosion inhibitors

Name____________ Gallons

Scale inhibitors

Name____________ Gallons

pH adjusters

Name____________ Gallons

Anti-foams

Name____________ Gallons

Sludge conditioners

Name____________ Gallons
88

ANNUAL WATER EFFLUENT: (Provide water discharge test if available)

Type

Total

Quantity

Percent of total by unit process (percentage or volume) Units

Log yard Sawing Drying Planing Boiler/Co-gen

BOD1Pounds

COD2Pounds

Chlorine Pounds

Oil Pounds

Suspended solids Pounds

Dissolved solids

Phenols Pounds

Others (please list 

all known): Pounds

1 Biological oxygen demand

2 Chemical oxygen demand

DRY KILN INFORMATION (dry kilns are the most energy intensive process for making 

decking/lumber)

Part of this study will be reviewing energy reduction potentials associated with kiln-drying, the most 

energy intensive aspect of lumber production. Please provide the following details on each of your 

kilns. If all or some kilns are identical simply write “same as Kiln No. X” below the appropriate kiln 

number. Attach a separate sheet if there are more than 5 kilns.

Dry Kilns 1 2 3 4 5

Kiln Capacity (Mbfm) 

Energy System

Direct-fired

Fuel type (gas, oil, biomass, etc.)

Capacity (BTU’s / hr.)

Total HP electrical motors 

(blower, make-up air etc.)

Radiant Heating (coils)

Type (steam, hot oil, hot water)

Kiln Configuration(side loading, 

single track, double track)

Average age of kilns or year 

installed

Fan Configuration (line shaft, 

cross shaft)

No. of fan motors
89

Dry Kilns (continued) 1 2 3 4 5

Total HP for Kiln

Humidification System (yes/no)

If yes, state type (live steam, 

water spray)

Vent Heat Exchangers present 

(Yes/No)

Drying Practices

Initial Moisture Content

Average length of time material 

remains in air-drying yard (days)

Average Kiln–drying Time for 

all material (hrs)

Pre-sorting (Yes/No)

If Yes, state type of sorting (by 

MC, grade, other)

Final Moisture Content
90

Glossary

Baghouse: Air pollution device which forces gases through a filter thereby capturing gas born 

particles.

BOD

By-product: Material produced during manufacturing that is recycled or used “within system 

boundaries.”

Bottom ash: Residual by-product of burning coal. Porous, grainy, roughly sand sized particles.

Co-product: A material produced from manufacturing and "sold outside of the system 

boundary."

Cyclone: A device that uses centrifugal forces to collect waste material.

Dust: Dispersion particles formed in grinding a solid; particles may be small enough to 

temporarily suspend in the air.

Edgings: Pieces of board produced after lumber passes through an edger to achieve desired 

width.

Electrostatic Precipitator (esp): A type of precipitator which changes the electrical charge on a 

particle so that it can be captured by electrostatic forces.

Emissions: Expulsion of pollutants to air from a source.

Fly ash: Particulate impurities that come from burning coal and other materials.

General refuse: Waste collected from the facility that is mixed with dirt and cannot be sent to 

the boiler.

HAPs: Hazardous Air Pollutants (carbon oxides, nitrogen oxides, sulfur oxides).

Inorganic material: Material such as sand and other non-solubles.

Industrial waste: Material produced during manufacture requiring disposal out of the “system 

boundary.” 

Packaging material: Steel strapping, plastic lumber covers, cardboard corners, plastic or paper 

wrap.

Particulates: By-products of combustion or milling; can be solid or liquid state.

PM10: Standard for measuring solid and liquid particulates in suspension in the atmosphere; 

particulates are defined here as less than 10 micrometers in diameter.

Product: The primary material produced from manufacturing and "sold outside of the system 

boundary."

Recycled material: Material collected from the manufacturing facility operation that is re-used.

VOCs: Volatile Organic Compounds- produced in incomplete combustion of carbon based 

compounds; does not include methane; examples are oil based paints and gasoline fumes. 
91

15 Appendix: Landfill Gas Equations

Equation 1: Where GHGDE is GHGs directly emitted to atmosphere:

 ( ) ( ) (

 

 ⁄ )

 ( ) ( 

 

 ⁄ )

Equation 2: Where GHGLFGR is GHG emitted from LFG energy recovery:

 

 

 ⁄ 

Equation 3: Where GHGLFGF is GHG emitted from LFG flaring: 

 

 

 ⁄ 

Equation 4: EOLFGR is the energy offset by LFG recovery: 

 ( ) 

 (

 

 ⁄ )( 

) 

 

 ⁄ 

 

Wkg: Wood Mass in kg 

C: Carbon Content of Wood = 0.53

D: Decomposition of Wood in Landfill = 0.23

CCO2: Carbon content of wood converted to CO2 = 0.55 

CCH4: Carbon content of wood converted to CH4 = 0.45 

CH4GWP: Global Warming Potential of CH4 = 25 

LFGC: Landfill Gas Capture Efficiency = 75% 

LFGR: Landfill Gas Energy Recovery Efficiency = 70% 

LFGHHV: Landfill Gas Higher Heating Value = 15.8 MJ/kg