Full Research Article: https://www.tandfonline.com/doi/full/10.1080/14486563.2024.2377779
Hemp-based construction materials have increasingly captured attention in recent years as viable alternatives to carbon-intensive materials. A benefit of using hemp (Cannabis sativa L) in construction is its ability to sequester carbon dioxide during plant growth, thereby providing the potential to create carbon-negative materials. However, hemp production can contribute to other environmental impacts such as acidification and eutrophication. Additionally, hemp-based materials usually involve higher costs compared to traditional materials. This study presented an application of an eco-efficiency framework to explore options for improving the environmental and economic performance of non-load-bearing hemp-based construction boards at the production stage in Australia. The study integrated environmental life cycle assessment, multi-criteria analysis, environmental mitigation strategies, life cycle costing and eco-efficiency portfolio analysis in order to identify eco-efficiency improvement opportunities for non-structural hemp-based construction boards and to compare them with conventional alternatives. The analysis showed that the use of solar electricity during the post-farm stage of hemp-based board production can reduce their environmental impact by 26 per cent and production costs by 0.4 per cent. The proposed framework can assist hemp growers and hemp-based composite manufacturers in Australia in developing cost-effective environmental mitigation strategies to assist sustainability in the construction sector.
1. Introduction
The Australian building and construction sector is a major driver of the nation’s economy with a workforce of around 1.2 million people contributing to 7.3 per cent to the gross domestic product (RBA Citation2023; Shooshtarian et al. Citation2023). Despite its importance, this sector faces widespread criticism for practices that have adverse effects on the environment, economy and society across the lifetime of buildings, i.e. resource extraction, material production, construction, operation, demolition and end-of-life of waste production (Rivas-Aybar, John, and Biswas Citation2023a).
The development of sustainable buildings and building materials begins at the early stages of their life cycle, necessitating the use of life cycle assessments for decision-making (Backes and Traverso Citation2021). Life cycle assessment tools are useful in estimating environmental, economic and social impacts, jointly known as triple bottom line objectives, for the sustainability assessment of building products (Dong, Ng, and Liu Citation2023). Environmental life cycle assessment (ELCA) is widely employed to evaluate environmental impacts over a product’s lifetime, in order to compare the performance of different products and to identify improvement opportunities (Abdalla et al. Citation2021; Satola et al. Citation2021). Whilst ELCA initial focus was on the evaluation of global warming potential (Cabeza et al. Citation2014), ELCAs have expanded to incorporate more impact categories deemed relevant in the construction realm, including land use, acidification, eutrophication, ozone depletion, biodiversity impacts and water use (CEN Citation2019). Life cycle costing (LCC) assesses the economic viability (Xie, Cui, and Li Citation2022) and social life cycle assessment evaluates positive and negative social impacts of a product during its life cycle (Huertas-Valdivia et al. Citation2020).
As highlighted in numerous ELCA-based studies, plant-based materials hold promise for mitigating resource depletion and environmental degradation in the construction sector (Rivas-Aybar, John, and Biswas Citation2023a). Among various plants suitable for construction, industrial hemp (Cannabis sativa L.) stands out due to its high carbon dioxide sequestration ability, rapid growth cycles, adaptability to various climatic and soil conditions, and hygrothermal and acoustic properties (Mouton, Allacker, and Röck Citation2023; Ntimugura et al. Citation2021). In Australia, hemp-based building materials exhibit considerably lower greenhouse gas emissions compared to their traditional counterparts and can help to achieve Australia’s emission targets (Rivas-Aybar, John, and Biswas Citation2023b). However, there are still uncertainties in mitigating other environmental impacts caused by construction activities such as land use changes, eco-toxicity and eutrophication (Ingrao et al. Citation2018). These impacts are further compounded by potential economic challenges due to the higher costs of plant-based materials compared with traditional materials (Soonsawad, Martinez, and Schandl Citation2022).
The choice of construction material is not solely driven by environmental performance but is ultimately based on costs (Colli, Bataille, and Antczak Citation2020; Yang and Yue Citation2021). As such, the LCC methodology is increasingly being combined with ELCA to conduct economic and environmental assessments of emerging building materials in a manner that mirrors the concept of eco-efficiency (Zhang and Biswas Citation2021). Eco-efficiency (EE) aims to provide competitively priced products that minimise ecological impacts and resource intensity across their lifecycle (Verfaillie Citation2000). Therefore, EE can aid in the selection of building materials optimising environmental performance at the lowest possible cost (Dynan et al. Citation2023). EE evaluations have also been conducted by manufacturers in the early stages of product development to provide a choice for the most eco-efficient product alternative (Grosse-Sommer et al. Citation2020). This has been the case for the German firm BASF, which developed an EE toolbox gaining popularity across various industrial sectors, including construction (Heijungs Citation2022). Arceo, Biswas, and John (Citation2019) proposed an enhanced version of the BASF tool to generate product alternatives that incorporate EE strategies at the design stage.
Incorporating economic and environmental impacts in the EE framework can provide a better understanding of sustainability challenges for construction materials (Gundes Citation2016; Hollberg and Ruth Citation2016). However, it is worth noting that the EE method lacks the incorporation of the social pillar of sustainability. This exclusion is recognised as a limitation since building materials deemed cost-competitive and environmentally friendly may result in unfavourable social consequences, including increased health and safety risks, job losses and human rights issues (Rivas-Aybar, John, and Biswas Citation2023a).
Despite this limitation, an increasing number of studies have applied the EE framework to evaluate the sustainability of alternative solutions such as the use of hemp biomass in construction. Dickson and Pavía (Citation2021) compared the energy, environmental and cost performance of 21 different insulation materials in Ireland that exhibited the same thermal performance including hemp-based alternatives. The study reported that bio-based materials such as cellulose, recycled cotton, sheep wool and cork board as well as conventional alternatives including rock wool, phenolic foam, glass mineral wool, aerogel and polyisocyanurate board showed better performance than hemp-based materials. In a more comprehensive application of the EE framework, Colli, Bataille, and Antczak (Citation2020) compared the EE performance of six different thermal insulation materials over their life cycle in France. These materials included glass wool, hemp concrete, cellulose fibre, expanded polystyrene insulation, extruded polystyrene insulation and polyurethane. The study suggested that hemp concrete offered the most favourable environmental performance. In contrast, hemp-based materials presented the least favourable economic performance due to its higher cost. As a result, hemp concrete was not considered an eco-efficient material in comparison to the other alternatives.
It appears that the previous research has applied the EE tool to help select the most eco-efficient option amongst various commercially available building materials, including those derived from hemp. However, no study has yet applied the EE framework to enhance the EE performance of hemp-based materials at the design stage. Such a framework could help find strategies for improving the environmental performance whilst balancing cost performance. The goal of this study is to address this gap by integrating ELCA, multi-criteria analysis, environmental mitigation strategies, LCC and EE portfolio analysis to help identify EE improvement opportunities for hemp-based materials at the design stage. This research assesses novel non-structural hemp-based boards using this methodology and propose strategies to improve hemp-board EE performance in comparison to other conventional alternatives available in the Australian market such as gypsum plasterboards.
Full Research Article: https://www.tandfonline.com/doi/full/10.1080/14486563.2024.2377779