Cement alternatives can deliver the province of Utrecht an emission reduction of 290 kton CO₂-eq per year by 2030, plus 50 kton of carbon sequestration. The potential is tied to the construction of 100,000 homes in the 2020–2030 period.
What it is
After water, cement is the most-used substance in the world, responsible for 5 to 6% of global emissions. Although cement makes up only about 10% of the volume of concrete, it causes roughly 95% of the emissions; decarbonising limestone (clinker production) accounts for around 60% of that. Conventional clinker can be partly replaced by materials such as volcanic ash, clay, finely ground limestone, blast-furnace slag and fly ash. Going a step further are complete alternatives based on natural fibres, such as lime-hemp concrete (hempcrete), which even sequesters CO₂.
Potential in Utrecht
The total addressable market is the construction of 100,000 homes in 2020–2030. Based on the global pace of clinker replacement, 40% clinker replacement is realistic for Utrecht. The plausible scenario (40% clinker replacement) yields 60 kton CO₂-eq reduction; the ambitious scenario adds 50% use of progressive alternatives such as hempcrete, reaching 290 kton reduction plus 50 kton sequestration. Because emissions from cement and concrete production are insufficiently captured in the regional registry, these figures rest on assumptions from additional sources.
Co-benefits
Complete alternatives based on natural fibres — hemp, straw, bamboo — store carbon in the building itself. Building material thus turns from an emission source into a carbon store, often with good thermal and acoustic properties.
Provincial policy
With the Housing Construction Acceleration Programme 2021–2024, the province of Utrecht promotes the faster development of mid-segment homes. In line with the Environment Act, these homes are built as sustainably as possible; for 2020–2030 this concerns 100,000 homes in total.
In practice
Vd Bosch Beton developed the cement-free Reduton with SQAPE, achieving around 80% CO₂ reduction compared with conventional concrete. Isohemp builds with hemp blocks that offer strong thermal and acoustic properties in both structure and finishing, and the Dreen roof tile by Zoontjes — made from blast-furnace slag and fly ash among others — was used on the roof terrace of Utrecht University of Applied Sciences.
Frequently asked questions
How much CO₂ can cement alternatives save in Utrecht?
According to this assessment, up to 290 kton CO₂-eq reduction plus 50 kton sequestration per year by 2030 (ambitious scenario), or 60 kton reduction in the plausible scenario.
Why does cement emit so much CO₂?
Decarbonising limestone during clinker production causes about 60% of cement emissions; the rest comes from energy use.
What is hempcrete?
A building material based on natural fibres that sequesters CO₂: on balance, hempcrete stores carbon in the building rather than emitting it.
Source: Preliminary Climate Solutions Assessment for the province of Utrecht (Drawdown Europe & New Economy, 2021), based on the Project Drawdown methodology. Part of the sector-based climate action plan for the province of Utrecht.