Environmental impacts of cross-regional mobility of construction and demolition waste: An Australia Study

Highlights

• Environmental impacts of cross-regional mobility of C&D waste are examined.

• A life cycle thinking based assessment model is developed.

• Foreground and background data are collected in australian context.

• Three main scenario settings including 51 sub-scenarios were developed.

• Steel is a critical contributor to the environmental impacts for most environmental indicators.

• Four strategies were proposed for the australian C&D waste management sector.

Abstract

The cross-regional mobility of waste has become an important approach to achieve a higher waste recycling rate in some countries. However, there is a lack of study to examine the associated environmental impacts. To address this gap, a life cycle thinking based environmental assessment model with 12 indicators was developed. The foreground data obtained in this study came from multiple sources and the background data was mainly obtained from GaBi Professional. Three main scenario settings including 51 sub-scenarios were developed. The results show that at current situation in Australia, the environmental impact in terms of GWP 100 years shows -6.73E+11 kg CO 2 -Equiv., AP -2.92E+09 kg SO${}_2$ -Equiv., EP -5.18E+07 kg Phosphate-Equiv., and Land occupation 3.55E+06 m 3 . The results showed that if the recycling rate passed 50%, the environmental impacts deduction value of recycling will surpass the environmental impacts. Amongst the waste materials, steel is a critical contributor to the environmental impacts for most environmental indicators. This study revealed that if the cross-regional mobility of C&D waste increases the overall recycling rate of the waste generated in all regions involved, it can reduce the environmental impacts of the waste, and vice versa. This study gains the knowledge of environmental impacts of the cross-regional mobility of C&D waste, which is largely overlooked in previous studies. Meanwhile, it provides the index and fundamental data for the development of LCA methodology in assessing the performance of C&D waste management. Future studies should seek for more local background data and up-to-date environmental impacts data.

Introduction

It has been reported that over ten billion tons of construction and demolition (C&D) waste is generated globally every year. China contributes about 30% (Zheng et al., 2017); India contributes about 20% (Jain et al., 2020); the European Union and the United States contribute about 10% respectively (Jain et al., 2015). Along with the municipal solid waste, C&D waste has become part of the largest waste stream in the world and poses a significant global challenge to sustainable development (Nunes et al., 2020; Wu et al., 2019a). There are global efforts to seek solutions for addressing these growing C&D waste, such as adopting the recycled aggregates in concrete, pavement concrete, and bricks (Aslam et al., 2020; Chen et al., 2021a, b; Toghroli et al., 2018).

The composition of C&D waste mainly include masonry waste (such as asphalt, concrete, bricks, and plasterboard), metals (such as steel, aluminium, and other non-ferrous metals), organics (such as garden organics, timber), paper & cardboard, plastics, glass, TLR (Textiles, leather and rubber), and others (DEE, 2018). amongst these materials, masonry waste contributes about 80% of the total weight, hence the long distance transportation of the waste is normally of low-level efficiency (Solis-Guzman et al., 2009; Coelho and de Brito, 2011; Miatto et al., 2017). In some countries, there are laws that require C&D waste to be managed locally (i.e., treatment, recycling, and landfilling at local facilities (Wiedenhofer et al., 2015; Stephan and Athanassiadis, 2018). Accordingly, the system boundary of C&D waste management is concentred at the regional level whereas the waste is considered as a local-closed issue in previous studies. (Wu et al., 2019b).

Due to a number of factors (e.g., waste treatment capability, benefit incentives, industry common practices, etc.), some regions transport the generated C&D waste to other regions for further processing or disposal (Yazdani et al., 2021; Wu et al., 2020). For instance, In China, Hong Kong transports its C&D waste to Zhongshan for landfilling due to the lack of available land. Similarly, the Shenzhen authority has developed a scheme to apply the cross-regional mobility of C&D waste amongst different districts within the municipality, as some regions (e.g., Nanshan, Futian and Luohu) do not have space to develop waste treatment facilities (Bao et al., 2020; Wang et al., 2021).

Although the amount of C&D waste generated in Australia, some 20 million tons annually, may not be as large as in other parts of the world, it is still the most significant waste stream of all solid waste generated in the country (DEE, 2018;). In Australia, because of the differences in waste levies between the states and the availability of facilities, a considerable portion of C&D waste has been transported across states. For instance, a considerable portion of C&D waste has been transported from New South Wales to Queensland for landfilling, and South Australia has become the recycling centre that receives the metals, plastics, glass waste from other states, such as Victoria, Western Australia, and Northern Territory (DEE, 2018). Improving the collection and treatment service of C&D waste has become a critical task for Australian government (Udawatta et al., 2015; Yazdani et al., 2021).

Given that the processing of waste (e.g., sorting, transportation, recycling, etc.) will have some environmental impacts (e.g., energy consumption, land occupation, air emissions, etc.) (Park and Tucker, 2017), the cross-regional mobility of C&D waste will affect the amount of C&D waste being managed in the regions that export and import the waste, which will further influence the environmental performance of the waste management system (Wang et al., 2019). Despite its difficulties in long distance mobility, the cross regional movement of C&D waste has become an important way of increasing waste management rates in certain areas, whereas the environmental performance of cross-regional mobility of C&D waste is somewhat arguable due to the lack of empirical data (Wu et al., 2020).

Significant efforts have been made to quantify and compare the potential environmental impacts related to recovery, utilisation, and final disposal of C&D waste materials (Chen et al., 2020). Recently, Husan et al., (2020) conducted the life cycle assessment of recycled construction waste in the UAE; Da Paz et al. (2020) assessed the environmental impact risks derived from the illegal dumping of construction waste in Brazil; Wang et al. (2018) compared offsite C&D waste recycling in a factory to mobile onsite C&D waste recycling. In earlier years, Wu et al. (2015) examined the carbon emissions of handling construction waste in China, Mercante et al. (2012) compared the environmental performance for two types of C&D waste recycling facilities in Spain. Ortiz et al. (2010) evaluated the environmental impacts of the treatment of construction waste generated from the LIFE 98 ENV/E351 project. However, as all these previous studies viewed the management of C&D waste as a local-closed issue, whether the cross-regional mobility of the waste would increase or decrease the environmental impacts of the system is unknown. Besides, previous studies did not consider particular parameters for the cross-regional mobility in C&D waste management when the evaluation criteria were developed. Accordingly, the previous impacts assessment methodology for C&D waste management warrants further developed. To address this gap, this study develops a LCA based model to assess the environmental Impacts of cross-regional mobility of C&D waste and Australia is selected a study case to illustrate the model. The study can provide valuable information and fundamental data for the decision makers to decide whether to courage or discourage the cross-regional mobility of C&D waste and how to minimise the environmental impacts associated with the issue.

The remainder of this paper is organised as follows: Section 2 reviews the characterisation of C&D waste and related cross-regional mobility issues, and the impacts and management performances assessment of C&D waste. A well-developed method for assessing the environmental impacts of the cross-regional mobility of C&D waste is introduced in Section 3, which includes five subsections. Section 4 presents the main results of the study, i.e., the environmental impacts of cross-regional mobility of C&D waste in Australia, scenario analysis, and environmental impacts contribution analysis. Finally Section 5 draws the conclusions and highlights the implications of the impacts evaluation.