Project

Co-benefits from enhanced weathering and biochar combinations

To keep global temperature rise well below 2°C, large scale CO2 removal is needed. Enhanced weathering and biochar not only sequester carbon, but in combination may also suppress heavy metal mobility and promote nutrient availability, thereby stimulating crop productivity when applied to agricultural soils. The aim of this PhD project is to experimentally study these potential co-benefits resulting from the combined application of enhanced weathering and biochar in a series of pot experiments and a lysimeter experiment.

Background

Fossil fuel combustion and land use change have already caused global temperatures to rise 1.1°C above pre-industrial levels. In 2015, countries globally agreed in the Paris Agreement to limit temperature rise to 1.5-2°C. Besides strongly reducing greenhouse gas emissions, technologies that actively remove CO2 from the atmosphere and store it in other reservoirs, such as soils or oceans, are urgently required. Two examples of such technologies are enhanced weathering and biochar. Enhanced weathering involves the mining, crushing, and spreading of silicate rocks which consume CO2 upon weathering. Biochar is produced by the pyrolysis of organic materials, resulting in a soil amendment that is rich in carbon and high in reactive surface area. Enhanced weathering and biochar not only sequester inorganic and organic carbon, respectively, but may also support nutrient and heavy metal cycling and thereby crop productivity when applied to agricultural soils.

Description

In this PhD project, we use laboratory experiments, greenhouse pot experiments, and a lysimeter field experiment to research potential co-benefits resulting from the application of silicate minerals in combination with biochar on different types of agricultural soils. In a laboratory soil column experiment, different types of silicate minerals were compared on their soil CO2 sequestration and co-benefits for soil quality. This experiment was followed by a series of greenhouse pot experiments in which different doses of the same silicate rocks were studied with and without biochar amendment. Pot experiments were conducted on sandy, clayey, and organic-rich peat soils to allow a comparison of the potential CO2 sequestration by enhanced weathering and biochar on different types of agricultural soils. A lysimeter field experiment has been set-up for which sandy and clayey soils were amended with different silicate minerals, also in combination with biochar. The lysimeter field experiment is intended to run for a longer period of time to determine the long-term effects of enhanced weathering and biochar on CO2 sequestration, soil chemical properties, and crop productivity.

Results

The laboratory soil column experiment showed that wollastonite and olivine minerals have a high potential for soil CO2 sequestration, and revealed potential for minerals that are novel in this context. All studied minerals improved soil quality in terms of pH and nutrient concentrations. However, nickel leaching was enhanced from olivine-amended soils (te Pas et al., 2023). The pot and lysimeter experiments will unravel to what extent and through which mechanisms co-benefits can occur when crushed silicate minerals and biochar are applied in combination to different types of agricultural soils. Although initial results show clear differences in CO2 sequestration potential between soil types, enhanced weathering and biochar will likely be an important contribution to the portfolio of technologies required to remove CO2 from the atmosphere across all soil types.

Figure 2. A. Picture showing the experimental set-up
Figure 2. A. Picture showing the experimental set-up

Publications