A Low-Carbon Manufacturing Technology to Turn Municipal Waste Incineration (MSWI) Ash into Artificial Aggregates

Description

Hong Kong is a bustling metropolis in the greater Bay Area of China, known for its remarkable pace of development resulting from the local government's focus on urbanization, modernization, and industrialization. Meanwhile, the government is dedicated to achieving carbon neutrality and eliminating landfills as part of its waste blueprint campaign by 2050 and 2035, respectively. However, these efforts are challenged by the increasing volume of municipal solid waste, including plastic, glass, and textiles, due to the high living standards of society, as well as the scarcity of local resources, which necessitates the import of construction materials like gravel and river sand. These dilemmas require urgent intervention from both the government and research institutes. As per the Environmental Protection Department (EPD) of Hong Kong (www.epd.gov.hk), the landfills in the region are receiving a staggering 11,000 tons of municipal solid wastes (MSW) daily. To achieve carbon neutrality and eliminate the need for landfills, a state-of-the-art integrated waste management facility, I.Park1 is currently being built near Shek Kwu Chau Island. Starting in 2025, this facility will be Hong Kong's first Wasteto-Energy (WtE) plant, with municipal solid waste incineration (MSWI) treatment capacity of 3000 tons per day. As a result, the amount of MSWI ash produced will increase significantly, creating a new environmental challenge for Hong Kong. Under these circumstances, we suggest expanding our patented concept of crushing technology-based geopolymer artificial aggregates (GPA). This approach will provide an eco-friendly treatment for MSWI ash through the use of low-carbon clinker-free geopolymer technology and allow for the mass production of artificial aggregates with an angular shape that can be used in various construction applications. To achieve this, we propose constructing a pilot production facility to handle the MSWI ash output and produce GPA (branded as "Geo-Aggregate") and solve crucial issues for such pilot production. This facility will include ash silos for storage, batching plants for mixing, compacting, and molding the geo-aggregates, curing devices, crushing and grading devices, and outdoor curing and storage space. The final product will be tested and monitored at every stage, from receiving the MSWI ash to dispatching the finished product to ensure that it meets all local environmental safety requirements. This onestone-for-two-birds approach will not only provide a sustainable solution for MSWI ash treatment but also create a valuable construction material. Geo-aggregates will be considered economical and lightweight aggregate products with acceptable mechanical properties and excellent environmental safety. Such products can partially fulfill the demand of the construction industry, minimize the cost and carbon footprint of importing raw construction materials from overseas, and promote waste management and recycling in Hong Kong. The suggested applications of Geoaggregates can be 1) production of mass plain marine concrete, 2) production of partition blocks (lightweight, thermal insulation, and noise reduction features), 3) subgrade filler in pavement engineering, 3) production of greener hot mix asphalt (enhanced interfacial transition zone between bitumen and Geo-Aggregates due to their porous nature), and 4) backfilling material for irregular excavation areas.