Page 73 - Envision 17

issue 17
071
01 NEA's approach to closing the waste loop.
02 Examples of reuse of municipal solid waste (MSW)- derived materials around the world.
REUSE OF MSW-DERIVED RESIDUES AROUND THE WORLD
02
by the Land Transport Authority (LTA) that used a phosphate-based technique called WES-PHIx to stabilise contaminants, that IBA was included as a possible road building material in LTA’s Materials and Workmanship Specifications for Roadworks. This was, however, still subject to compliance with prevailing environmental regulations, which meant that standards had to be developed before treated IBA could be introduced into the market.
To develop provisional standards for NEWSandTM for construction applications, NEA has been studying, in recent years, various international standards that are relevant for IBA applications, so as to determine the parameters (e.g. arsenic, lead, cadmium, etc.) and testing protocols (e.g. leaching tests) suitable for Singapore’s context and needs. Baseline studies on conventional construction materials were then carried out, before the limit for each of the parameters (termed Reference Values as a group) was derived.
There are differences in the approaches used by various regulatory bodies around the world to develop criteria for utilisation, depending on the countries’ specific contexts. For example, Denmark prioritises the strict protection of groundwater quality, as they rely almost exclusively on groundwater for drinking water. On the other hand, Germany has based their
utilisation legislation on optimising the use of secondary materials, so as to preserve natural resources and to protect the environment. This allows utilisation only when any impact to the environment can be disclosed, i.e. utilisation is restricted to well-defined construction applications (Henrik Ørnebjerg, 2006).
To understand the context for our provisional standards for NEWSandTM, we have to consider the different context for IBA applications in Singapore and in the other countries that have already started constructing with IBA. IBA is the residue that remains after the incineration of MSW, and thus it contains heavy metals such as arsenic, chromium, lead and cadmium, among others. When it comes into contact with rain, groundwater or surface water, these metals could leach out and pollute the environment. Therefore, treatment of IBA is required prior to its application.
In the Netherlands and Denmark for example, IBA with minimal treatment may be used as a construction material in non-water catchment areas, and the authorities track these applications over its usage lifetime. However, two-thirds of tropical Singapore is designated as water catchment areas, which means that a lot of construction work may happen within these areas. For IBA applications in construction to be practical, the standards would have