Carbon dioxide balance of wood substitution: comparing concrete-and wood-framed buildings (original) (raw)
Related papers
Energy policy, 2000
In this paper, primary energy use and carbon dioxide (CO ) and methane (CH ) emissions from the construction of a multi-storey building, with either a wood or a concrete frame, were calculated from life-cycle and forest land-use perspectives. The primary energy input (mainly fossil fuels) in the production of building materials was found to be about 60}80% higher when concrete frames were considered instead of wood frames. The net greenhouse gas (GHG) balance for wood materials will depend strongly on how the wood is handled after demolition of the building. The net GHG balance will be slightly positive if all the demolition wood is used to replace fossil fuels, slightly negative if part of the demolition wood is re-used, and clearly positive if all wood is deposited in land"lls, due to the production of CH . However, if the biogas produced is collected and used to replace fossil fuels, the net GHG emissions will be insigni"cant. If concrete frames are used, the net GHG emissions will be about those when demolition wood from the wood-framed building is deposited in land"lls and no biogas is collected. We have considered that the CO released from the chemical processes in the production of cement will be re-bound to the concrete by the carbonisation process. Otherwise, the net GHG emission would be more than twice as high when concrete frames are used. If forest biomass is used instead of fossil fuels, the net area of forest land required to supply both raw material and energy for the production of building materials, will be about twice as high when wood frames are used instead of concrete frames. However, the GHG mitigation e$ciency, expressed as CO equivalents per unit area of forest land, will be 2}3 times higher when wood frames are used if excess wood waste and logging residues are used to replace fossil fuels. The excess forest in the concrete frame alternative is used to replace fossil fuels, but if this forest is used for carbon storage, the mitigation e$ciency will be higher for the "rst forest rotation period (100 yr), but lower for the following rotation periods. Some of the data used in the analyses are uncertain, but an understanding of the complexity in comparing di!erent alternatives for utilising forest for GHG mitigation, and of the fact that the time perspective applied a!ects the results markedly, is more important for the results than the precise "gures in the input data.
Increased Use of Timber in New Buildings in Oslo and Akershus: Potentials and GHG Emission Effects
Frontiers in Built Environment
The choice of materials may play an important role in achieving the common European aims of near zero energy demand and greenhouse gas (GHG) emissions in the lifecycle of buildings. The production of timber materials demands lower emissions than concrete and steel. To guide political and industrial priorities, it is vital to estimate the emission effects of increased use of timber. The article reports on a broad study that had the following aims: 1. To forecast the number, types, floor area, and location of new buildings that will be built in Oslo and Akershus counties between 2015 and 2030. 2. To estimate how many of these new buildings (a) will be and (b) could be built with timber as the main construction material. 3. To compare these timber potentials to the present and future availability of nationally and sustainably sourced and manufactured timber. 4. To estimate the effect on GHG emissions when substituting concrete and steel with timber in the production of new buildings in Oslo and Akershus counties between 2015 and 2030. The research is based on official prognoses for population growth. They are combined with building predictions derived from municipal statistics and plans. A GHG reduction factor is extracted from existing studies of the effects of conversion to timber. This factor is used to estimate the GHG saving potentials of different scenarios for timber use. Main results:
Environmental Utility of Wood Substitution in Commercial Buildings Using Life-Cycle Analysis
Wood and Fiber Science, 2017
Wood is the predominant construction material in the US residential sector. In commercial and midrise construction, the use of wood is limited compared with reinforced concrete and steel. Wood, being a natural, renewable material that sequesters carbon, is a natural fit for newer construction with enhanced sustainability goals. The objective of this study is to evaluate and identify the environmental utility (avoided emissions) of using wood in place of steel and concrete in the commercial construction and renovation sectors in Oregon, United States. The study used comparative, cradle-to-grave, life-cycle analysis, with Athena Impact Estimator for Buildings. Six case studies that represent different building functionalities, material systems, and construction techniques were modeled via the user interface input option, and the results were evaluated for global warming potential (GWP) and impacts on energy sources, such as fossil fuel consumption, when structural materials are substi...
Annals of Forest Science, 2005
ABSTRACT Long-living wood products can contribute to the mitigation of climate change in many ways. On the one hand, they act as a carbon pool during their service life, as they withdraw CO2 from its natural cycle. After their service life, they can substitute for fossil fuels if they are incinerated in adequate furnaces. On the other hand, wood products can substitute for more energy intense products made of ‘conventional’ materials. This paper quantifies the substitution and carbon pool effects of an increased use of wood in the building sector in Switzerland for the years 2000–2130. For this purpose, life cycle data on greenhouse gas (GHG) emissions of 12 wood products and their substitutes is used as proxies for the most important groups of building products used in construction and in interior works; this data is linked to the forecasted wood flows for each group of building products in a cohort-model. For the political assessment, GHG effects occurring abroad are distinguished from GHG effects occurring in Switzerland. The results show that the C-pool effect of an increased use of wood products with long service life is of minor importance; the substitution effects associated with the thermal use of industrial and post-consumer waste wood as well as with the substitution of ‘conventional’ materials are much more relevant, especially on a long-term. For construction materials, the Swiss share of the GHG effect related to the material substitution is relatively high, as mainly nationally produced concrete, mineral wool, and bricks are substituted for. For products used in interior works, the Swiss share of the GHG effect related to the material substitution is rather small (or even negative for single products) because mainly imports are substituted, such as ceramic tiles or steel produced in the EU. The results are rough estimates. Nonetheless, these calculations show that an increased use of wood in the building sector is a valid and valuable option for the mitigation of greenhouse gas emissions and for reaching GHG emission targets on a mid- to long-term basis. Still, the carbon storage and substitution capacity of an increased use of wood is relatively small compared to the overall greenhouse gas emissions of Switzerland. Effets de puits de carbone et de substitution par l’utilisation augmentée de bois dans les bâtiments en Suisse. Les produits en bois avec une longue durée de vie en service peuvent contribuer de manière diverse à la diminution des émissions de gaz à effet de serre. D’une part, ils forment un puits de carbone issu du CO2 retiré de l’atmosphère par l’arbre au cours de sa croissance. Après leur utilisation, ils peuvent se substituer aux combustibles fossiles s’ils sont incinérés dans des chaudières adéquates. D’autre part, le matériau bois peuvent se substituer à des matériaux « conventionnels » plus coûteux en énergie. Cet article quantifie les effets de la substitution et de puits de carbone qui résultent d’une utilisation augmentée de bois dans les bâtiments en Suisse de 2000 à 2130. Dans ce but, les valeurs de rejets de gaz à effet de serre de 12 produits de bois et de ses substituts sont utilisées comme approximations pour les ensembles de produits de construction et d’aménagement les plus importants. Ces valeurs sont combinées avec une prévision des flux de chaque ensemble de produits dans un modèle de cohortes. Pour l’évaluation politique des résultats, les émissions des gaz à effet de serre en Suisse sont distinguées des émissions à l’étranger. Les résultats indiquent que l’effet de puits d’une plus grande utilisation de bois à durée de vie longue est d’une moindre importance; les effets de substitution associés à la valorisation énergétique des déchets de bois industriel et des produits en fin de vie ainsi que les effets de substitution de matériaux « conventionnels » sont beaucoup plus significatifs, particulièrement dans une perspective à long terme. Concernant les produits de construction, les effets de substitution de matériaux sont relativement importants en Suisse, parce que dans la majorité des cas, se son les éléments construits en Suisse en béton ou en briques qui sont remplacés. En ce que concerne l’aménagement, les effets de substitution de matériaux en Suisse sont relativement petits (ou même négatif dans certains cas), parce que dans la majorité des cas, ce son des produits importés qui sont remplacés, par exemple des carreaux de céramique ou des éléments en acier fabriqués dans la CE. Les résultats de ces calculs doivent être considérés comme estimations. Cependant, ces calculs montrent qu’une plus grande utilisation de bois dans les bâtiments est une option valable visant à diminuer les émissions de gaz à effet de serre à moyen et long terme. Mais la capacité de puits et de substitution d’une utilisation augmentée de bois est relativement petite, si on la compare avec le total des rejets de gaz à effet de serre en Suisse.
Comparative life-cycle assessment of a mass timber building and concrete alternative
Wood and Fiber Science, 2020
The US housing construction market consumes vast amounts of resources, with most structural elements derived from wood, a renewable and sustainable resource. The same cannot be said for all nonresidential or high-rise buildings, which are primarily made of concrete and steel. As part of continuous environmental improvement processes, building life-cycle assessment (LCA) is a useful tool to compare the environmental footprint of building structures. This study is a comparative LCA of an 8360-m 2 , 12-story mixed-use apartment/office building designed for Portland, OR, and constructed from mainly mass timber. The designed mass timber building had a relatively lightweight structural frame that used 1782 m 3 of cross-laminated timber (CLT) and 557 m 3 of gluelaminated timber (glulam) and associated materials, which replaced approximately 58% of concrete and 72% of rebar that would have been used in a conventional building. Compared with a similar concrete building, the mass timber building had 18%, 1%, and 47% reduction in the impact categories of global warming, ozone depletion, and eutrophication, respectively, for the A1-A5 building LCA. The use of CLT and glulam materials substantially decreased the carbon footprint of the building, although it consumed more primary energy compared with a similar concrete building. The impacts for the mass timber building were affected by large amounts of gypsum board, which accounted for 16% of total building mass. Both lowering the amount of gypsum and keeping the mass timber production close to the construction site could lower the overall environmental footprint of the mass timber building.
Whole‐life embodied carbon in multistory buildings: Steel, concrete and timber structures
Journal of Industrial Ecology, 2021
Buildings and the construction industry are top contributors to climate change, and structures account for the largest share of the upfront greenhouse gas emissions. While a body of research exists into such emissions, a systematic comparison of multiple building structures in steel, concrete, and timber alternatives is missing. In this article, comparisons are made between mass and whole-life embodied carbon (WLEC) emissions of building superstructures using identical frame configurations in steel, reinforced concrete, and engineered timber frames. These are assessed and compared for 127 different frame configurations, from 2 to 19 stories. Embodied carbon coefficients for each material and life cycle stage are represented by probability density functions to capture the uncertainty inherent in life cycle assessment. Normalized results show clear differences between the masses of the three structural typologies, with the concrete frame approximately five times the mass of the timber frame, and 50% higher than the steel frame. The WLEC emissions are mainly governed by the upfront emissions (cradle to practical completion), but subsequent emissions are still significantparticularly in the case of timber for which 36% of emissions, on average, occur postconstruction. Results for WLEC are more closely grouped than for masses, with median values for the timber frame, concrete frame, and steel frame of 119, 185, and 228 kgCO 2 e/m 2 , respectively. Despite the advantage for timber in this comparison, there is overlap between the results distributions, meaning that close attention to efficient design and procurement is essential. This article met the requirements for a gold-gold JIE data openness badge described in http://jie.click/badges.
Wood based panels in modern methods of construction for housing: greenhouse gas abatement analysis
2019
The Construction Sector have developed a roadmap for reducing built environment carbon emissions by 50% by 2025, which will contribute to national carbon emissions reduction targets net zero by 2050. As energy efficiency of buildings has improved significantly, there is a growing interest in the embodied carbon of the buildings themselves, in addition to the operational carbon which has been the primary focus until this point. This paper reports a study which was undertaken to compare the embodied carbon of timber framed and masonry residential structures. The work indicates a significant benefit per dwelling for timber framed systems. This was in line with previous studies using different building designs and different functional units. Embodied carbon is the carbon associated with the input materials and manufacture (including processing, transport, etc.) of a product, as well as later demolition, recycling or disposal. It is possible to determine embodied carbon for single materi...
Greenhouse gas emission from construction process of multi-story wooden buildings
The purpose of this study is to investigate environmental impact for construction process of wood-based building. Detailed data collection from construction work is conducted on three multi-story wooden buildings. Greenhouse gas (GHG) emission value is calculated for production stage (material production and construction) and operation stage of the buildings, and a ratio of the emission from construction process is observed. The results present that construction phase holds about 20-30% of GHG emission in the production stage. In addition, it is shown that material production phase, construction phase and operation phase of the buildings account for approximately 16-35%, 6-10% and 55-78% of the total GHG emission, respectively. Based on the results, feature of the impact for wood-based construction and an issue regarding the data collection are discussed. This study demonstrates a relevance of construction process in a life cycle assessment of buildings. Since the result of environm...
2013
Forests are a store of carbon and an ecosystem that continually removes carbon dioxide from the atmosphere. If they are sustainably managed, the carbon store can be maintained at a constant level, while the trees removed and converted to timber products can form an additional long term carbon store. The total carbon store in the forest and associated 'wood chain' therefore increases over time, given appropriate management. This increasing carbon store can be further enhanced with afforestation. The UK's forest area has increased continually since the early 1900s, although the rate of increase has declined since its peak in the late 1980s, and it is a similar picture in the rest of Europe. The increased sustainable use of timber in construction is a key market incentive for afforestation, which can make a significant contribution to reducing carbon emissions. The case study presented in this paper demonstrates the carbon benefits of a Cross Laminated Timber (CLT) solution for a multistorey residential building in comparison with a more conventional reinforced concrete solution. The embodied carbon of the building up to completion of the construction is considered, together with the stored carbon during the life of the building and the impact of different end of life scenarios.