Reducing MKI and MPG with fibre reinforcement
MKI and MPG appear ever more often in tenders. What the Environmental Cost Indicator and MPG involve — and how fibre reinforcement scores on both.
When substantiating sustainability choices in tenders and construction projects, two terms come up increasingly often: the Environmental Cost Indicator (MKI) and the Environmental Performance of Buildings (MPG). This article explains what these terms mean and how fibre reinforcement contributes to a lower score on both.
What is the MKI?
The Environmental Cost Indicator (Milieukostenindicator, MKI) is a standardised measure of the total environmental impact of a product or construction material, expressed as a notional "environmental cost" amount. This indicator combines multiple environmental effects (climate change, acidification, depletion of raw materials, and more) into one comparable figure, calculated according to the National Environmental Database (NMD) and its associated assessment methods and product category rules (such as the PCR Asfalt).
The lower the MKI score of an asphalt or concrete mixture, the lower its weighted environmental impact.
What is the MPG?
The Environmental Performance of Buildings (MilieuPrestatie Gebouwen, MPG) is a mandatory calculation for most new-build projects in the Netherlands, expressing the cumulative environmental impact of all construction materials used in a building as a shadow price per m² of gross floor area per year. MPG requirements will be tightened further in the coming years, increasing the pressure to choose construction materials with a lower environmental impact.
How does fibre reinforcement contribute to a lower MKI?
• For asphalt: research within the European FIBRA project shows that a polymer modified bitumen (PMB) mixture has a more than 10% higher environmental impact at cradle-to-gate level than a comparable mixture with fibre reinforcement and standard penetration bitumen. This benefit mainly stems from the lower production temperature and better recyclability of the penetration bitumen.
• For concrete: replacing (part of) the steel reinforcement with fibre reinforcement reduces the environmental impact associated with steel production — an effect that feeds directly into the MKI score of the concrete structure.
How does fibre reinforcement contribute to a lower MPG?
Because fibre reinforcement contributes to a longer service life for both asphalt and concrete (potentially up to 50% longer service life for the road surface and up to 200% longer service life for the asphalt layer itself, depending on fibre type and application), the material's environmental impact is spread over a longer period. For the MPG calculation, which is based on environmental impact per year, a longer service life means a lower annual environmental impact — even where the initial production impact of the fibre reinforced mixture is comparable to or slightly higher than the alternative.
Concrete example: circular concrete and MPG
To illustrate how large the difference in MPG contribution between material choices can be: a recently introduced circular concrete product achieves an MPG contribution of 0.1, compared with 0.3 for traditional concrete — a considerable difference that feeds directly into a building's total MPG score. Fibre reinforcement, alongside circular raw material choices, is one of the ways to achieve differences of this kind.
Practical application
For clients and designers who want to reduce a project's MKI and MPG:
• Request the MKI score of the proposed asphalt or concrete mixture, preferably substantiated according to the applicable PCR and included in the NMD.
• Ask for the expected service life of the fibre reinforced mixture, with substantiation, to be able to correctly calculate the MPG contribution.
• Compare different alternatives (PMB, reinforcement mesh, fibre reinforcement) based on these figures, rather than on initial construction costs alone.
In summary
MKI and MPG have become the standardised language in which the sustainability of construction materials is expressed and compared. Fibre reinforcement scores favourably on both indicators: a lower direct environmental impact during production, and a lower annual impact thanks to a longer service life.