Optimising the use of recycled C&D waste material in civil construction projects

The substantial growth in infrastructure developments has resulted in an increase in the quantity of Construction and Demolition (C&D) waste, and the need to find effective waste management options. Although recycling C&D waste is becoming the preferred option for maintaining sustainable waste management practices, the adoption of recycling within the building industry is still very slow, with some C&D waste material still going to landfill. There are many drivers and barriers to the effective recycling and use of C&D waste materials. As many C&D companies strive to be considered as having sustainable practices, it has become necessary to overcome the existing barriers, as the demand for C&D recycled materials remains low. This study investigated the recycling of Reinforced Concrete (RC) and brick waste materials as a substitute for virgin gravel, compared to landfill disposal. Case-studies from six construction sites and a recycling plant were analysed, using the Triple Bottom Line +1 (TBL+1) concept to discuss the environmental, social, economic, and governance impacts. The methods of data analysis applied were ‘End-of-Life-Cycle Assessment’ (ELCA), ‘investigating construction site practices’, ‘End-of-Life-Cycle Cost’ (ELCC), and ‘review of waste legislation’. Environmentally, four impact categories were considered for the ELCA study, namely, global warming (CO2), water use, solid waste and embodied energy. The recycling results indicated that benefits of not producing virgin gravel or steel were significant in reducing the overall environmental impact, especially in energy and transport use. However, sustainable fuel options for transport and energy could further improve the environmental recycling benefits realised. The environmental impact of recycling RC and bricks was comparatively lower than landfill disposal. Socially, the study of the six construction sites highlighted best practices, and some barriers to recycling that had been gradually adopted at construction sites. The study findings indicated that the potential to recycle relied on effective waste management practices at C&D sites, and hence there was the need for a broader application of waste management practices across the building industry. Economically, ELCC calculations revealed cheaper RC and brick recycling costs compared to landfill disposal and virgin gravel production, when avoided production of steel and virgin gravel were considered. Conclusions from the cost calculations indicated that fuel tax costs and sustainable cheaper fuel options could further reduce recycling cost. However, to effectively maintain demand for recycled RC and brick materials, the introduction of higher landfill fees, taxes on virgin products, and subsidies for recycled products such as RC and bricks, is required. The governance aspect of the study reviewed seven organisational contributions to waste legislation. The review revealed that although there were several environmentally certified recycled materials on the market, the majority of them were not C&D recycled materials. The review of legislation highlighted the need to promote the endorsement of C&D recycled materials, as a critical step to the improvement of product quality, and increased demand. The overall results indicated that the optimisation of demand for recycled C&D waste materials could not be solely improved by considering environmental impacts. The social, economic, and governance impacts were very important aspects to consider. This study successfully addressed the interrelated factors needed to improve current recycling practices, with recommendations to increase demand for C&D recycled products such as RC and bricks.