Waste Management and Recycling Technologies

Waste Management and Recycling Technologies
Speakers:
- Mr Daniel Pintado, Business Analyst, JFE Engineering
- Dr Lim Sheau Hooi, Research and Development Scientist, Environmental and Water
Technology Center of Innovation (EWTCOI), Ngee Ann Polytechnic
- Mr Seow Teow Gay, Principal Engineer, National Environment Agency
Waste management is one of the key challenges faced by growing global cities. Industrialisation
and economic growth have raised affluence levels and concurrently waste generation. While
there are technological solutions to address the waste challenge, one key to achieving a
sustainable solution is to view waste as a resource and encourage wide-spread recycling. A
number of interventions are underway to maximise recycling, create new materials from waste,
and to efficiently handle large volumes of waste in urban areas like Singapore.
Research in Sustainable Material Technology
The Environmental and Water Technology Centre of Innovation (EWTCOI) at Ngee Ann
Polytechnic has been performing research and development in recycling a variety of waste
streams for industry application. Areas under R&D include water technology like wastewater
treatment and analysis, sustainable materials using waste products, energy efficiency design,
measurement, and development, and membrane technology.
According to EWTCOI, the true cost of waste is about 10 times the cost of disposal when all
externalities like raw material, labour, and energy are taken into account. With that in mind,
transforming waste streams into new products holds potential value for business. Some
examples of products under development include:
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Transforming waste paper and cardboard into lightweight, recyclable packaging materials
for shipping new items
Combining used wood and plastic waste into wood-plastic composite (WPC) for durable,
weather-resistant materials for a wide range of uses
Creating carbon nanotubes from plastic for use in applications like transistors, touch
screens, and solar cells
Turning materials like incinerator ash, steel slag, rice husk ash, and glass materials into a
variety of new building products like cement substitutes, paver bricks, floor tiles, and
decorative and light weight materials for interiors
EWTCOI is also developing other innovative materials like self-cleaning coatings for solar panels,
environmentally-friendly chemical descalers and water-based coating for passive cooling of
buildings, and supercritical fluid CO2 to reduce chemical use and wastage and increase previous
metal recovery. Industry collaboration is vital to help fine tune and commercialise unique
offerings like these, and the institution continually seeks new project partners. With numerous
waste streams to be tapped, new opportunities are nearly boundless if the business case can be
made.
Challenges in Waste-To-Energy (WTE) Research
Reducing waste volumes through recycling and new product development is one of many
strategies. Another is WTE technology. From its early days of development and due to limited
land area, Singapore has pursued WTE as a means of reducing waste volume. There are
currently four WTE plants contributing 2-3 per cent of the nation’s energy. The incinerator ash as
well as non-incinerable waste is taken to its offshore landfill, Semakau Island. This landfill is
estimated to have a life to 2030-2035, after which a new solution will need to be found. In the
past four decades, Singapore’s waste generation has increased seven-fold, and there will be
numerous challenges in the future to manage waste levels as the country continues to develop.
Waste composition is one of the complex areas. Comingled plastic, food, and paper make up the
lion’s share of daily domestic waste output. Separation for recycling is difficult due to
contamination. These materials also have high moisture content which makes incineration
inefficient. As a result, WTE plans only achieving an electrical efficiency of 15-20 per cent.
Improvements using current technology face limitations like acid dewpoint and high temperature
corrosion becoming a problem.
To overcome such obstacles, the NEA has created a number of funding strategies to improve
core WTE technologies, develop a dedicated research centre, and support test-bedding and
demonstration of new technologies. There is also an Environment Technology Research
Programme (ETRP) aimed at institutions of higher learning to develop new waste management
technology. The project areas covered under ETRP include energy recovery, special waste
treatment, and resource recovery. R&D areas of special interest include more efficient sorting
and pre-treatment solutions, organic waste separation and treatment, thermal treatment for
waste, and ash treatment and utilisation.
Advanced Waste Thermal Treatment
Particularly in the areas of thermal treatment for waste as well as ash treatment and utilisation,
there is opportunity to learn from the Japanese experience. There, high-temperature gasification
and direct-melting technologies are well-established.
JFE
Engineering
Corporation
has
pioneered many new technologies in
recent decades in an increasingly
legislated waste management industry.
As an alternative to large blast furnaces
in conventional WTE plants, the company
developed a smaller gasifying furnace
capable of handling equal waste volumes.
Complementary, proprietary systems like
oxygen generator, water granulation
conveyor, and magnetic separator
technologies have been developed by the
company.
By-products
of
waterTechnology from blast furnace
granulated slag and metal can be
harvested for reuse in addition to steam and ash typically derived from WTE.
This technology can use a wider range of materials—including medical and hazardous wastes,
incinerator bottom ash, sludge, municipal solid waste, and refuse-derived fuel— can be handled
with typical WTE plants. The gasification furnace high temperature melts the waste’s
incombustible material, generating safe slag and metal that can be recycled for industrial use.
JFE also notes safe and stable plant operation with no explosion or gas leak risks. Due to its
flexibility and smaller plant size, the gasification furnace and also be co-located with other waste
management facilities.
Typical process flow with direct melting gasification furnace
In Japan, there have been 11 JFE gasification plants built or underway since 2003. The recovered
slag material has been used as base construction material, asphalt aggregates, pavement,
concrete secondary products, and also for backfilling, reclamation, and landfill cover. It has
complied with relevant JIS standards for a number of these applications, and has noted in field
applications to improve performance and cost of projects.
While gasification plants and their by-products may need additional testing and customisation to
ensure high performance in local contexts, the Japanese experience points towards successful
results potentially worth replicating in other rapidly developing parts of Asia.
Conclusion
Development of innovative products, advanced WTE technology, and increased reuse and
recycling of waste materials are important areas to the future of waste management in Asia.
Reported by:
Chris Tobias
Assistant Director
Knowledge & Resource Centre
Singapore Environment Institute