INVESTIGATE THE CARBON FOOTPRINTS OF THREE INTERMEDIATE FLOORING SYSTEMS: CROSS-LAMINATED TIMBER, SOLID CONCRETE, AND HOLLOW-CORE PRECAST CONCRETE

This paper evaluates and compares the embodied energy and embodied carbon using a Life Cycle Assessment (LCA) approach for three different intermediate floor structures, all of which use prefabricated materials—cross-laminated timber (CLT), precast hollow-core concrete, and solid concrete—to decide which floor construction materials have less environmental impact for use in the construction of a semi-detached house in the UK. The Inventory of Carbon & Energy (ICE) and the Carbon Calculator tool were used to calculate the carbon footprint from “cradle to grave” to determine whether the use of a CLT solution provides improved environmental performance over the traditional concrete solutions. The carbon footprint results indicate that the use of a hollow-core precast concrete floor system emits less carbon than the other two systems, although the concrete requires more fossil fuel input than the timber during the manufacturing process, so based on this, the footprint from cradle to gate for the timber was expected to be the less than that of the concrete. However, the results show the opposite; this is because of the differences in the material quantities needed in each system.

Rolling Shear Properties of Cross-Laminated Timber Made from Australian Plantation Eucalyptus nitens under Planar Shear Test

With the increasing availability of fast-growing Eucalyptus plantation logs in Australia in recent years, the timber manufacturing sector has become interested in discovering the opportunities of producing value-added timber products from this resource. Cross-laminated timber (CLT) could be a potential sustainable product recovered from this resource and supply material for commercial buildings. Shear of the inner cross-laminates, known as rolling shear, is one of the governing factors in serviceability and limit state design for this product under out-of-plane loading. This study evaluated the rolling shear (RS) properties of CLT with heterogonous layup configurations using different structural grade Eucalyptus nitens (E. nitens) timber under the planar shear test. Based on the results, Gr and τr values were shown to be significantly correlated with the density of the CLT panel. There was also a positive correlation between the RS modulus and MOR of the CLT panel. The specimens with high MOE in the top and bottom layers indicated the highest τr and Fmax values. This indicated that using high-grade boards in the top and bottom lamellae plays an important role in increasing the RS strength, whereas using them in the cross-layer has a positive contribution in increasing shear modulus. The maximum observed RS strength and modulus ranged from 2.8–3.4 MPa and 54.3–67.9 MPa, respectively, exceeding the RS characteristic values of the resource. The results obtained in this study were comparable to those recommended in European standards for softwood CLT, demonstrating the potential use for eucalypt timber boards in CLT production. This paper provides an important insight into supporting the potential engineering applications of CLT panel products fabricated with eucalypt plantation.

Evaluation of GHG Emissions from the Production of Cross-Laminated Timber (CLT): Analysis of Different Life Cycle Inventories

The Cross-Laminated Timber (CLT) has been receiving special attention in recent research as an alternative for climate change mitigation since it is a renewable source and can remove and stock high amounts of CO2 from the atmosphere. Some countries, such as Brazil, still do not have mature and large CLT industry. However, the development of this industry in other countries is expected since the CLT is considered the main wood material to be used in high-rise mass timber buildings. It is particularly important to have environmental information, especially concerning the climate change impacts, in terms of life cycle greenhouse gas (GHG) emissions, for this product to increase its competitiveness in a new market. In this context, this research aimed to evaluate three different Life cycle inventories (LCIs) for CLT production of studies from Japan and the United States. Based on the first findings, we summarized the critical items in the LCI of CLT production and listed some actions for the reduction of GHG emissions that occur in this process. The LCIs are adapted considering the context of Brazil (a country with a cleaner electricity matrix) and China (a country with the highest share of fossil fuels). The main inconsistencies present in the LCIs are presented and discussed. The GHG emissions are concentrated in the following hotspots: (1) Roundwood production; (2) electricity consumption; and (3) adhesives production for CLT production. Therefore, the reduction of the consumption of these materials and activities should be encouraged for the decrease of GHG emissions. The data of Roundwood used in the modelling severely affects the final results. Their GHG emissions are related to the consumption of diesel in forestry activities. This research brings insights into the evaluation of the life cycle GHG emissions from the production of CLT.

Life Cycle Assessment of Cross-Laminated Timber Transportation from Three Origin Points

Cross-laminated timber (CLT) used in the U.S. is mainly imported from abroad. In the existing literature, however, there are data on domestic transportation, but little understanding exists about the environmental impacts from the CLT import. Most studies use travel distances to the site based on domestic supply origins. The new Adohi Hall building at the University of Arkansas campus, Fayetteville, AR, presents the opportunity to address the multimodal transportation with overseas origin, and to use real data gathered from transporters and manufacturers. The comparison targets the environmental impacts of CLT from an overseas transportation route (Austria-Fayetteville, AR) to two other local transportation lines. The global warming potential (GWP) impact, from various transportation systems, constitutes the assessment metric. The findings demonstrate that transportation by water results in the least greenhouse gas (GHG) emission compared with freight transportation by rail and road. Transportation by rail is the second most efficient, and by road the least environmentally efficient. On the other hand, the comparison of the life cycle assessment (LCA) tools, SimaPro (Ecoinvent database) and Tally (GaBi database), used in this research, indicate a remarkable difference in GWP characterization impact factors per tonne.km (tkm), primarily due to the different database used by each software.