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The possibility of recovering energy from biomass residues has attracted a lot of research interest due to the environmental problems associated with burning coal. Wood wastes generated from construction and demolition activities and other wood product wastes can be a good potential source of renewable energy. The present study was conducted by using Hong Kong as an example to assess the environmental sustainability of converting recycled wood wastes (from construction and demolition activities and other wood product wastes) to produce wood pellets for direct energy generation. The chemical and physical characteristics of different types of wood product wastes were tested. An attributional lifecycle assessment approach was used to assess and compare the environmental impacts and sustainability for heat generation from the pelletized bio-fuel and coal. The test results showed that the energy content, chemical compositions and the trace metal concentrations all met the relevant standards. The results also showed that significant impacts on health, ecosystem, climate change and resources damage can be potentially avoided by using wood pellets instead of coal for energy generation. The overall findings demonstrated that the proposed “energy recovery” approach for using wood pellets as a bio-fuel in Hong Kong is environmentally sustainable, which can provide an alternative route for managing wood product wastes with the added benefits of energy recovery, and may be more applicable in mega cities especially when city-based incineration is a concern. [ABSTRACT FROM AUTHOR]

Substantial amount of resources is consumed by pavement systems, which have resulted considerable environmental impacts. Understanding the environmental impacts would provide opportunity for reducing resource consumption and informing decision-makers in the process of designing sustainable pavement. There is a lacking of comprehensive and comparative sustainability assessment of pavement systems in highly urbanized context currently. Therefore, this study aims to design and comprehensively evaluate the environmental performance of the commonly adopted pavement systems in highly urbanized context using lifecycle assessment (LCA) technique through a case in Hong Kong. According to the codes and practices of Hong Kong, two pavement systems including flexible and rigid pavements were designed based on the same road section. After that interviews with structured questionnaire were conducted to collect relevant practical information of pavement construction and maintenance from the relevant professional bodies and experts for the subsequent LCA of such designs. The LCA results reveal that the two mid-point impacts of global warming potential and mineral extraction are 21% and 54% higher for rigid pavement than for flexible pavement. Yet, the end-point results indicate that flexible pavement is associated with 64%, 65%, and 69% higher human health impact, ecosystem quality damage, and resource damage, respectively. Material production and transportation contribute significantly to the total impact in the two pavement systems. For instance, it is about 57% and 97% of the total global warming potential for flexible and rigid pavements, respectively. The overall results demonstrated that 49% higher total impact was found for flexible pavement than rigid pavement. Therefore, the use of more recycled and environmentally friendly materials can potentially enhance the environmental sustainability of both pavement systems. The findings should provide useful information to the design and selection of sustainable pavement structures in resource-scarce highly-urbanized cities. [Display omitted] • Designed two commonly used pavement systems based on the existing practices in Hong Kong. • Evaluated the environmental sustainability of pavements in an urban context using LCA. • Considerably higher impact was associated with frequent maintenance in flexible pavement. • About 49% higher total impact was found for flexible pavement than the rigid pavement. [ABSTRACT FROM AUTHOR]