Comparative Economic and Life Cycle Analysis of Future Water Supply Mix Scenarios for Hong Kong - A Water Scarce City.

Increasing urbanization and changes in climate have placed increasing stress on urban water supply systems. Policy makers have increasingly adopted alternative water supply sources, such as desalination and water reclamation to meet this challenge, however these technologies may increase the negative environmental impacts of the water supply system. These alternative sources are energy intensive, and more expensive to produce, which raises questions about their sustainability. In this study, a Life Cycle Assessment (LCA) and a economic portfolio choice model were used to determine the impacts of Hong Kong's long term water policy. The results of our study show that the current water policy will increase the carbon emissions of producing 1 m3 of freshwater by 11% to 1.65 kg CO2-Eq due to the addition of desalination. However, a fit-for-purpose water policy approach only increases emission by 4%, to 1.54 kg CO2-Eq, by instead relying on water reclamation to offset freshwater consumption. Impacts from increased energy consumption were mitigated by improved wastewater treatment, which reduced CH4 emissions. Although, ozone layer impacts increased due to higher NOx and N2O emissions, highlighting the need to consider emissions from wastewater treatment processes when evaluating water reclamation processes. Impacts to water prices were also minimized when reclaimed water was chosen over desalination, due to its lower unit production cost. By considering both cost and environmental impacts of such system level changes, decision makers can more accurately evaluate different water supply approaches for data-driven policymaking.

Life cycle assessment (LCA) of food waste treatment in Hong Kong: On-site fermentation methodology.

"Smart Food Waste Recycling Bin" (S-FRB) systems have recently been developed to facilitate the transformation of food waste into an end-product suitable for use as an energy resource following circular economy principles. This decentralized waste decomposition system utilizes fermentative microorganisms for the treatment of organic food waste and has emerged as a possible solution for coping with both landfill capacity and greenhouse gas emissions issues. This paper utilizes Life Cycle Assessment (LCA) to determine the environmental impacts associated with this S-FRB technology and identify environmental hotspots to reduce these impacts. In this paper, we have conducted an on-site pilot-scale study for 2 months at a canteen located at the City University of Hong Kong, which resulted in a 90% reduction in the mass of food waste treated in the S-FRB system. Based on this pilot-scale study hypothetical scenarios were developed to determine potential environmental impacts potential scaled-up deployments of the S-FRB instrument based on varied assumptions. Examination of the LCAs of these different scenarios demonstrated the potential for further reduction in CO2 equivalent emissions during food waste treatment. Cumulative Energy Demand (CED) and Energy Return on Investment (EROI) were also investigated to understand the energy balance energy of the S-FRB technology. Finally, using current waste treatment methods in Hong Kong as a benchmark, the environmental impacts of the S-FRB are compared with the conventional food waste treatment approaches such as landfilling and organic waste treatment facilities (OWTF).

Smart Food Waste Recycling Bin (S-FRB) to turn food waste into green energy resources.

Effective treatment of food waste is inherently difficult due to several factors, including its heterogeneous composition, high moisture content, and low heating value. To address these issues, this study aims to convert food waste into an energy resource using naturally occurring fermentative microorganisms embedded in wooden biochips (bio-catalysis), utilizing a "Smart Food Waste Recycling Bin" (S-FRB) system. High-throughput 16S rRNA gene sequencing analysis identified the major aerobic and facultatively anaerobic bacteria with alpha-diversity in terms of the Phylogenetic Diversity index ranging from 40.8 (initial stage) to 24.5 (mature stage), which indicates the microbial communities are relatively homogeneous and effective for use in the S-FBR. Operational results indicated that the organic content of food waste traded in the system increased from 53% up to 72% in the final end-product and achieved a mass reduction rate of approximately 80%. The heating value of the end-product, which was 3300 kcal/kg waste when measured by the differential scanning calorimeter (DSC) method, confirmed its high potential as a biofuel. Overall, the S-FRB system presents a practical approach for food waste treatment that solves the putrescible waste problem and maximizes utility through resource circulation.