Eco-Block Reduces Waste, Curbs Carbon Emissions and Turns Waste into Resources
About 180 tonnes of glass waste are disposed of in landfills every day in Hong Kong, accounting for 1.7% of municipal solid waste. The glass waste recycling rate is less than 20% here, lower than that in other East Asian territories such as Korea and Taiwan, and lagging far behind Mainland China where the recovery rate exceeds 50%. The problem is that it costs nothing to dispose of glass as Hong Kong has yet to implement its municipal solid waste charging scheme and there is a lack of a major glass recycling business.
“PolyU took the lead in developing a glass waste recycling solution in Hong Kong,” says Ir Professor Poon Chi-sun, Director of The Research Centre for Resources Engineering towards Carbon Neutrality (RCRE), Chair Professor of Sustainable Construction Materials and Head of Department of Civil and Environmental Engineering at PolyU. “We have been transforming waste glass into environmentally friendly construction materials called ‘eco-blocks’ for over ten years.”
Professor Poon began to play an active role in the research and application of green building materials more than 20 years ago. He pioneered the development of eco-blocks through the incorporation of construction, demolition and other discarded waste. Eco-block, now in its fifth generation of development, is made by crushing recycled glass into glass sand to replace natural sand and concrete aggregates as major constituents of paving bricks. “We put forward the use of eco-blocks on the campus through a demonstration project while also driving the commercialisation of the technology,” says Professor Poon. “After all, Hong Kong’s waste problem has to be tackled by Hong Kong.”
Nowadays, waste is one of the top three contributors of carbon emissions in the territory. Inspired by the Hong Kong SAR Government’s vision to minimise carbon emissions and achieve carbon neutrality before 2050, PolyU has established the “Task Force on Campus Carbon Neutrality” aiming to reach carbon neutrality by 2045 through the implementation of ground-breaking technologies.
Apart from reducing the consumption of natural resources, recycling waste into usable materials is also an effective way to slash carbon emissions. In light of this, Professor Poon has led his team to research waste recycling solutions since the beginning of 2000. They developed eco-blocks by replacing some of the natural aggregates with crushed construction and demolition waste and produced green construction materials with the recycled aggregates.
By applying carbon curing technology, the team effectively accelerated carbonation between carbon dioxide and the active constituents of cement mortar on the surface of the recycled aggregates, filling up the pores and microcracks to reduce water absorption and crushing strength. This boosted the durability of eco-blocks to a level comparable to natural sand aggregates. “By doing that we can permanently store carbon dioxide inside the construction materials to cut down greenhouse gas emissions,” Professor Poon explains.
Besides leading research activities, Professor Poon makes every effort to promote the commercialisation of research. After graduation, riding on the technology he developed, two of his students set up a facility in Hong Kong to manufacture eco-friendly construction materials from recycled construction, demolition and glass waste. This not only reinforces PolyU’s strategic focus of knowledge transfer, but also realises the University’s principle to pursue impactful research that benefits the world.
“Superficially eco-blocks seem more expensive than traditional bricks,” says Professor Poon. “However, if we take the overall environmental value and the life-cycle cost of public governance into account, they are actually more cost-effective.” Firstly, eco-blocks are made from waste and recycled materials, which effectively cuts waste disposal costs and saves landfill space for the community. Secondly, there is no local supply of sand for making traditional bricks and this has to be imported from Mainland China or overseas at a considerable shipping cost. This is in addition to the increased global focus on fostering environmental protection that has resulted in a gradual decrease in sand mining activity. In other words, making bricks with natural sand is getting more expensive. “The prices of natural resources are definitely on the rise,” Professor Poon adds. “Therefore, the cost advantage of making eco-blocks out of local waste instead of using natural sand imported from far-away places is clear.”
Thirdly, replacing conventional bricks with eco-blocks can reduce the amount of natural sand mining. “Extraction of sand and gravel requires extensive mining work, which leads to significant impacts on the environment and animal ecology. Instead, wide adoption of eco-blocks in the community will create considerable benefit and value for the whole life cycle,” Professor Poon explains. “According to our calculation, overall eco-block delivers considerable cost advantage over traditional bricks.”
Over the years, Professor Poon’s invention has received various awards including a Notable Mention in the ECO-Products Award 2006 in Hong Kong, a Merit Award in the Green Building Award 2006 in Hong Kong, the Gold Award in the 6th International Exhibition of Inventions in Suzhou, China and the Best Invention Award from the Macao Foundation in 2008, as well as the Second Prize of the State Technological Invention Award in the National Science and Technology Award Conference in 2018.
Despite the breakthroughs he has achieved and the success he has scored in eco-block development, Professor Poon has never slackened the pace in his “waste-to-resources” research. He has recently published a report on turning discarded waste glass into recycled glass power to partially replace concrete as a construction material. “The solution is able to reduce the construction industry's reliance on and use of cement, which is highly polluting and carbon dioxide-rich. While manufacturing one ton of cement releases 0.8 ton of carbon dioxide, glass powders can replace 30% of the cement in construction materials and curb global carbon emissions.” Professor Poon’s research report has shown the workability of this solution and how PolyU has become an ideal testing and verification venue.
Professor Poon explains that different generations of eco-blocks have been put into use on the PolyU campus, including for the ground floor of Block X. “While we keep stressing the importance of demonstration projects, coordinating with the government and external developers is a rather arduous task,” he says. “We have to meet the pricing and supply requirements for large-area application, deal with multiple organisations and go through various consultation, design and contractor and sub-contractor procedures, handling many processes, people and issues. The whole process is complicated. Comparatively, it is more straightforward to launch the solution on campus as we can simply discuss application matters with the PolyU Campus Development Office and Campus Facilities and Sustainability Office.”
Verifying scientific research on campus is not only easier to do, but also easier to monitor. “As we are fully aware of where the solution is installed and how it is used, it is more convenient to keep track of the results and durability. Moreover, we can always bring it back to the laboratory for performance review after a certain period of time,” says Professor Poon. “On the other hand, if the application is verified in the community, sometimes we even don’t know whether the equipment may be taken away or damaged by others, which will affect the testing results.”
With PolyU continuing to expand its campus, Professor Poon’s eco-friendly construction products will be applied in future projects including those at the planning stage and those that have already been started. Examples include the student hostel in Kowloon Tong, the campus expansion at the Ho Man Tin Slope and the redevelopment projects at Block VA and Block VS. By applying the relevant research outcomes on campus, PolyU is working towards a “green campus” while offering an optimal venue for the scientific verification of different practical and innovative technologies and solutions. This helps demonstrate the feasibility of the technologies and solutions in responding to societal demands on environmental sustainability and technological innovation – both on campus and in the community.