Wood and Wood-Based Products in Construction: Carbon Sequestration, Emissions and End-of-Life Scenarios

Environmental product declarations in accordance with EN 15804 and EN 16485 — How to account for primary energy of secondary resources?

This chapter is focused on the different uses of wood and wood products for structural purposes. It highlights the factors that favour this mode of wood utilisation. It also discusses the emergence of different wood products as structural materials; advantages and disadvantages of structural utilization of wood products in different forms; lumber sizes and grades employed across Africa; and presents a simple method of obtaining approximate working-stress data for indigenous species for which design values are not available in existing design codes, based on their densities. The properties and various uses of wood-based panel products, engineered wood products, wood–cement and wood–plastic composite panels are also discussed.

The Life-cycle Assessment (LCA) method and the Environmental Product Declaration (EPD) each play a crucial role in reducing buildings’ embodied environmental impacts. EPDs provide the validated and geographically representative data necessary to conduct an LCA. However, the development of EPDs in the European context is still irregular. Countries such as Germany and France have many EPDs for construction products, while other countries, such as Spain, have a limited number of EPDs and more than one operator programme, which is pointed out in the literature as a possible limiting factor for comparing results. This study aimed to examine the use of construction product EPDs manufactured in Spain, to then use as a data source to conduct a building LCA. We analysed the comparability of the results among the different EPD programmes and investigated to what extent the use of Spainߣs geographically representative construction product EPDs can contribute to conducting a building LCA, including all the materials and products that compose a building, and covering all the building life-cycle stages (product, construction, use, and end-of-life). The results showed that plasterboard and thermal insulation products have the highest numbers of EPDs in different EPD programmes. The case study analysis showed that 20% of the construction products that compose a building can potentially use these EPDs as a data source to conduct a building LCA, and 89% of those product categories include at least the product, use, or end-of-life stage modules. Finally, recommendations and challenges to improve LCA development in the architecture, engineering, construction, and operation industries were included.

PurposeA recent update to the Product Category Rules (PCRs) for Construction Products (of the International EPD System) has triggered a methodological issue for owners and users of Environmental Product Declarations (EPDs). The updated PCR has led to capital goods data being implicitly included in the Life Cycle Inventory (LCI) of EPDs. This paper critically examines the role of capital goods in EPDs and establishes major shortcomings in the current methodology, LCI datasets and interpretation.MethodsTo evaluate the role of capital goods in EPDs, this paper provides a discourse on the fundamentals of Life Cycle Assessment (LCA) methodology, scope, available LCI data and the impact of capital goods on EPD outcomes. Using the ecoinvent database, we analyse the impact of the inclusion and exclusion of capital goods in selected 38 construction products based on the EN 15804+A2 (2019) Standard. Finally, we estimate the relative contribution of capital goods to a suite of Life Cycle Impact Assessment (LCIA) indicators based on the archetypes of capital goods available in ecoinvent and apply Monte Carlo simulation to establish the range of uncertainties in the capital goods data for the selected construction products.Results and discussionOur research confirms that when capital goods are included based on currently available background LCI data, they mostly have a low effect (<10% increase) on climate change, but they can have an enormous effect (>100% increase) on abiotic depletion (minerals and metals), land use and/or human toxicity indicators. Interestingly, when looking further into the ecoinvent capital goods LCI datasets, it becomes clear that there are inaccuracies, inconsistencies, and possibly incorrect estimates of capital goods and infrastructure data. These findings raise questions about the suitability of the underlying LCI background data and whether non-attributable capital goods should be allowed to define EPD outcomes.ConclusionThe requirement for the inclusion of capital goods leads to a major conundrum for LCA practitioners. It is suggested that capital goods be excluded until there is better refinement and improvement of the quality of LCI datasets and EPD programs provide clearer guidance on dealing with capital goods. Alternatively, EPDs could document transparently the inclusion or exclusion of capital goods, so that there is a clear separation of the effects of capital goods on LCIA indicators.

Embodied carbon constitutes a significant portion of a building’s greenhouse gas (GHG) emissions and is a key challenge for the construction and real estate sectors. Embodied carbon includes construction product manufacturing, building construction, material replacement and end of life. During the specification and procurement stage, designers and contractors have the opportunity to prioritize products with lower carbon footprints. Environmental product declarations (EPDs) are a growing source of environmental data in the construction products market, and are increasingly being used for (1) environmental performance assessment of buildings and (2) product comparison for procurement decisions during the later stages of building design. An obstacle to identifying and purchasing lower embodied carbon products is a lack of data quality and the transparency of EPDs. However, EPDs vary widely in their data quality and specificity, which can lead to inaccurate and misleading comparisons. A new method is presented to account quantitatively for estimates of variation in underlying data specificity in EPDs to enable fairer comparisons between EPDs and to motivate the reporting of actual variability and uncertainty in EPDs. The application of this approach can help purchasers to assess EPDs quantitatively. Practice relevance Life-cycle assessments (LCAs) and LCA data can be used within the construction sector to evaluate buildings and to assist in design, specification and procurement decision-making. A new method is presented to support the assessment of comparability of functionally equivalent materials and products during the specification and procurement stage. Given the known variation and lack of precision within EPDs, this method provides quantitative metrics that correlate to a qualitative interpretation of EPD precision. This method can be used by anyone who is using EPD data to make product comparisons at the specification and procurement stage: It provides more confidence in choosing low-carbon material or product options when comparing between functionally equivalent options. It can incentivize product manufacturers and LCA practitioners to improve data quality and transparently report known variation in their EPDs. It may also motivate manufacturers to reduce GHGs from their products and processes.

Furfurylation expands the value of wood and wood-based products in construction and engineering applications by improving its dimensional stability and lowering its moisture absorption. However, the traditional liquid phase vacuum and pressure impregnation (VPI) process faces some problems and shortcomings in industrial application, such as excessive consumption of modifiers, and inducing wood drying defects. To avoid these inherent shortcomings, a novel furfurylation method based on solution quantitative adsorption (SQA) was first applied in this study to improve the properties of wood. The results showed that the SQA furfurylation could achieve the precise modification of cell wall and avoid the deposition of furfuryl alcohol (FA) resin in the cell cavities. The scanning electron microscopy and nanoindentation results showed the preparation of ultra-stable wood materials (ASE &gt; 70%) with low FA resin load (weight percent gain of about 20%) and high FA utilization. In addition, the SQA furfurylation could lead to the distribution of FA resin in the interior of wood, thus improving the physical properties of wood without altering the overall mechanical properties.

Macedonian vernacular architecture prominently featured wood as one of the primary and widely utilized building material, owing to its abundance, versatility, ease of construction, and captivating aesthetic allure. Therefore, the wood industry in Macedonia has a long tradition of producing a wide range of wood and wood-based products. Despite a rich and prosperous history, the wood products sector has experienced a consistent decline in profitability, diminished capacity to enhance value through downstream manufacturing, and a decline in overall competitiveness over the past two decades. Engineered wood products (EWPs) are building materials that have been used since the early 1980s as replacements for, or in conjunction with, concrete and steel. They provide increased design flexibility for ambitious construction and advanced manufacturing technologies. This study will present modern and contemporary architectural designs using EWPs. Furthermore, it will introduce conceptual project proposals from students, showcasing innovative design ideas that leverage the advantages offered by EWPs as exceptional building materials.

The forest sector plays an important role in the circular bioeconomy due to its focus on renewable materials that can substitute fossil or greenhouse gas emissions-intensive materials, store carbon in bio-based products and provide ecosystem services. This study investigates the state of the bioeconomy in Brazil and its forest industry. Specifically, this study presents some examples of novel wood-based products being developed or manufactured in Brazil and discusses possible opportunities for the development of the country’s forest sector. The pulp and paper industry plays an important role in the forest sector. It has also been showing advancements in the development of cascading uses of wood invalue-added products, such as nanocrystalline cellulose, wood-based textile fibers, lignin-based products, and chemical derivatives from tall oil. Product and business diversification through the integration of the pulp and paper industry to biorefineries could provide new opportunities. Moreover, biochemicals derived from non-wood forest products, such as resin and tannins could promote diversification and competitiveness of the Brazilian forest industry. Although some engineered wood products are still a novelty in Brazil, the market for such products will likely expand in the future following the global trends in wood construction.

In Japan, the demand for wooden houses is increasing while the number of carpenters is decreasing. Therefore, it is necessary to improve productivity in wooden house construction. This has led to an increase in the use of the pre-cut method. The pre-cut method is a method in which raw materials (base woods) and joints are processed in advance based on the design. Compared to conventional methods, the pre-cut method has various advantages, such as reduced construction time at the construction site and improved processing accuracy. With the above background, we have been conducting to improve the efficiency of pre-cut lumber production factories to increase productivity in wooden construction. After processing, pre-cut lumber is packed according to a pre-determined packaging sequence to improve work efficiency at the building site. When pre-cut lumbers that do not match the packaging sequence are produced, they are temporarily stored in a space. To reduce space and production time in a pre-cut lumber production factory, we studied a practical production planning algorithm using metaheuristics that minimizes the maximum number of racks used with pre-cut lumber production company A and confirmed the effectiveness of the proposed algorithm through numerical experiments.

Wood is increasingly being appreciated in construction due to its valuable environmental attributes. This paper explores the environmental and market performance of two wood supply chains in Northern Italy. Larch and chestnut wood are extracted and processed to obtain beams, planks, MDF panels and energy. LCA is performed to evaluate the environmental impacts of 1m3 of extracted wood through a cradle-to-gate approach. Then, a biogenic carbon analysis is carried out using the EN 16449:2014 standard including a comparison of different end-of-life treatments. Also, OSB is proposed as an alternative path for wood chips and contrasted to the current energy scenario. Moreover, solid wood beams and planks are compared with engineered wood products (EWPs). Lastly, a market analysis is conducted to assess the market trends of the different wood products studied.The LCA shows similar results for both wood species across most impact categories, with slightly higher values for the chestnut system. Most impacts are related to the production of MDF boards and the energy valorization of wood chips. Biogenic carbon analysis shows a negative balance of emissions with −314 and −205 kg of CO2 eq for larch and chestnut, respectively. It also suggests that OSB manufacturing can be a valuable alternative to the energy use of wood chips and that the end-of-life treatment with better results is recycling. The comparison of beams and planks with engineered wood products supports that solid wood poses a better environmental alternative in similar applications. Market analysis shows stagnation in the apparent consumption of wood products in the European market and a slight growth in the Italian one between 2018 and 2022. Overall, the systems studied suggest that the potential environmental benefits of using wood in construction are not being matched by current market trends.

Reducing carbon emissions is a top priority for combating climate change, and the use of wood products is one important strategy toward this direction. However, the impact pathways of wood products remain subjective to uncertainties, and there is a lack of consensus over the methodology for assessing impacts. This review focuses on the accounting of benefits, when wood-based products substitute non-wood products. The carbon impact of substitution is measured through the substitution factor (SF), which is derived from a comparative estimation of greenhouse gas (GHG) emissions of wood and non-wood products, using life cycle assessment (LCA). The calculation of SF is influenced by several factors such as system boundaries, functional unit, life cycle stages, product types, substitution assumptions, and end-of-life considerations. This review addresses the previously mentioned challenges and provides a summary of SFs for longer-lived wood products, categorized by product type, system boundary, and country. The findings show that SFs for wood products are higher in construction applications than in interior or furniture uses, with regional variations reflecting differences in the substitution effect. Among product categories, the sawnwood category exhibits the highest SF, followed by engineering wood products and wood-based panels. GHG emissions estimates are sensitive to whether biogenic carbon is accounted for, which in turn influences the respective SFs. Different biogenic carbon accounting methods yield varying outcomes, making this a divisive issue in LCA. Additionally, this review identifies sources of variability and uncertainty in SFs estimation and highlights a range of challenges linked to LCA aspects. Therefore, this review emphasize precautions within the LCA domain to ensure a more realistic estimation of carbon impacts while managing variability and uncertainties.

Increased use of engineered wood products (EWPs) and thus decreasing share of non-biobased materials such as concrete reduces the impact of buildings on the climate by mitigating the primary energy use and greenhouse gas emissions in construction. A construction project includes many parameters, where the selection of construction material is one of the crucial decisions with its numerous criteria e.g. cost, strength, environmental impact. Furthermore, this complicated process includes different parties such as architects, engineers, contractors. Architects are among the key decision-makers in material selection, and their perceptions influence what they propose and hence an increase in wood construction. In literature, many studies have been conducted on the technological, ecological, economic aspects of EWPs, while limited studies are focusing on EWPs for construction from stakeholders’ perspective. In this chapter, architects’ attitudes towards the use of EWPs in buildings were scrutinized.

The use of wood and timber products in the construction of buildings is repeatedly pointed towards as a mean for lowering the environmental footprint. With several countries preparing regulation for life cycle assessment of buildings, practitioners from industry will presumably look to the pool of data on wood products found in environmental product declarations (EPDs). However, the EPDs may vary broadly in terms of reporting and results. This study provides a comprehensive review of 81 third-party verified EN 15804 EPDs of cross laminated timber (CLT), glulam, laminated veneer lumber (LVL) and timber. The 81 EPDs represent 86 different products and 152 different product scenarios. The EPDs mainly represent European production, but also North America and Australia/New Zealand productions are represented. Reported global warming potential (GWP) from the EPDs vary within each of the investigated product categories, due to density of the products and the end-of-life scenarios applied. Median results per kg of product, excluding the biogenic CO2, are found at 0.26, 0.24, and 0.17 kg CO2e for CLT, glulam, and timber, respectively. Results further showed that the correlation between GWP and other impact categories is limited. Analysis of the inherent data uncertainty showed to add up to ±41% to reported impacts when assessed with an uncertainty method from the literature. However, in some of the average EPDs, even larger uncertainties of up to 90% for GWP are reported. Life cycle assessment practitioners can use the median values from this study as generic data in their assessments of buildings. To make the EPDs easier to use for practitioners, a more detailed coordination between EPD programs and their product category rules is recommended, as well as digitalization of EPD data.

Standardization work in the field of wood durability and preservation is managed, at the European level, by the technical committee TC 38 ‘Durability of wood and wood-based products’ of the European Committee for Standardization (CEN). Producing sustainable wood-based materials is challenging. A crucial aspect of their provision is reliable standards that take consideration of both the expectations of end-users and the broad set of parameters that may influence the service life of wooden components such as exposure to moisture, climatic variations and design. In order to reach these objectives, most CEN/TC 38 standards are currently being revised based on the recent scientific, technological and legal developments in the field of wood protection. There is an increasing need for performance classification of wood products in construction and to radically consider how wood durability test methods and standards can inform on service life and how they might be translated into a performance classification system. This paper describes the changes during the past 5–10 years in Europe and how the trajectory of standards development is now on a different pathway. Classification and service life demands are described as well as current approaches to consider key issues such as material resistance, moisture risk and adaptation of existing standards.

Engineered and reconstituted wood products play an important role in building construction, and have positive environmental impacts. However, the wood products compete with other construction material (concrete and steel) in terms of prices in the Canadian building construction industry, and the price competition has not been explored in past literature. In order to promote the use of wood and wood-based products, there is a need to understand how prices influence the choice of construction material. We estimated the own and cross-price elasticities of demand of construction material in Canada using standard log-linear regression models with consumption and price data from 1990 to 2017. Our study shows that engineered and reconstituted wood products are substitutes for cement and steel, and hence there is a need to focus on the development of these value-added forest products, to create sustainable local economies that are economically viable, environmentally sound and socially responsible.