Promising applications for biomass ash in construction materials

High-quality binders can be made from ash produced in biomass CHP plants, allowing construction blocks and concrete to be produced at lower cost and with no CO2 emissions. This is the main takeaway from ENGIE Laborelec’s contribution to the Biofficiency project funded by the EU’s Horizon 2020 program. “In many respects, it feels like the return of the old Roman or Greek concrete.”
The Biofficiency project, which ran from 2017 to 2019, focused on developing the ‘next generation of highly efficient biomass Combined Heat and Power plants’ allowing the power production industry to dramatically reduce carbon and other emissions. ENGIE Laborelec took part in the project, investigating opportunities for biomass ash utilization and nutrient recirculation, taking into account regulatory factors.
ENGIE Laborelec experts carried out a chemical analysis of the wide variety of ash produced by wood- or bark-fired biomass plants. In addition, different ways of using this biomass ash were tested, including application as a fertilizer or as an alternative binder or filler material in concrete and bricks.

The results are very promising, especially for the construction material industry. “Using biomass ash as a binder, we were able to produce geo-polymers of very high quality, with strengths exceeding 100 MPa,” says ENGIE Laborelec project coordinator Frans van Dijen. “Similar results were obtained by using calcium-rich ash as a replacement for lime in calcium-silicate blocks. This means that, as well as having these excellent properties, geo-polymers can be made without CO2 emissions, with a very low specific energy consumption and with low-cost raw materials. In many respects, it feels like the return of the old Roman or Greek concrete.”