Combining biochar and basanite rock powder enhances carbon dioxide removal by carbonate alkalinity production

[Geoengineering News]

https://www.frontiersin.org/journals/climate/articles/10.3389/fclim.2026.1853116/abstract

Authors: Johannes Meyer Zu Drewer, Maria-Elena Vorrath, Thorben Amann, Jens Hartmann, Maria Ansari, Marcela Cárcamo Pérez, Nikolas Hagemann 

06 May 2026

Abstract

The combination of enhanced rock weathering (ERW) with pyrogenic carbon capture and storage (PyCCS) has been proposed to harness synergistic effects on carbon dioxide removal (CDR). This can be facilitated by co-application of silicate rock powder and biochar or co-pyrolysis of rock powder and biomass to produce rock-enhanced (RE-)biochar. While it is well documented that co-pyrolysis of biomass and silicate rock does not affect the carbon yield nor the aromaticity of RE-biochar, the effect of co-pyrolysis and co-application on alkalinity production by ERW remains poorly constrained. Here, we quantified the daily and cumulative production of carbonate alkalinity (TAcarb g-1 basanite) in a controlled weathering experiment conducted in columns. We compared 14 treatments consisting of basanite rock powder, biochar, co-applications or RE-biochars produced at contrasting highest treatment temperatures (HTT) of 450 °C and 750 °C. The experiment was conducted under two conditions: with sandy, agricultural topsoil under ambient pCO2 and with washed, quasi non-reactive quartz sand under elevated pCO2 the latter designed to better isolate leachate signals originating from the amendments alone. Column flushing with demineralized water prior to the experiment and deduction of TAcarb signals by the matrix material and biochar amendments allowed the quantification of the net TAcarb signal from ERW, here referred to as Net_TAcarb. The cumulative Net_TAcarb production was significantly higher from co-deployments than from pure basanite (p<0.05) with RE-biochars producing more alkalinity than co-applications under both pCO2 regimes. The thermal treatment of pure basanite increased its mean specific surface area (p>0.05) but decreased its Net_TAcarb production. The release of dissolved silica correlated with Net_TAcarb production. In complementing pseudo-lysimeter experiments (i.e. same treatments set up in larger vegetated soil columns), no significant effect on plant growth was observed. Carbon sinks from PyCCS and ERW have complementary sequestration curves. Silicate rock powder may be co-deployed with biochar to hedge carbon losses from biochar mineralization while increasing alkalinity production and to unlock additional agronomic co-benefits.

Source: Frontiers