Quantifying air quality and indirect climate feedbacks of land-based greenhouse gas removal strategies

Grantham Scholar Katie Rees researches potential adverse climate consequences resulting from large-scale enhanced rock weathering co-deployment with afforestation/reforestation. 

The project

The 2021 IPCC Report recognizes urgent reductions in greenhouse gas emissions and large-scale carbon dioxide removal (CDR) are urgently required to mitigate climate change. Land-based CDR strategies include afforestation/reforestation (AR) and enhanced rock weathering (ERW, spreading crushed basalt onto land to speed up chemical reactions between rocks, water and air that result in CO2 removal). However, widespread implementation of these approaches will have consequences for air quality as well as indirect climate feedbacks, which so far have been overlooked.

An exciting feature observed from co-deployment of ERW within a pioneering large-scale (25,000 trees) AR field trial in Wales is that ERW affects soil nitrogen cycling and increases leaf nitrogen content of deciduous and evergreen trees, leading to potential changes in biogenic volatile organic compounds (BVOCs) emitted by the trees. This in turn affects the production of other atmospheric pollutants, e.g. ozone and secondary organic aerosols, which are harmful to human and crop health, as well as climate. Therefore, research is urgently required to address potential adverse climate consequences resulting from large-scale ERW co-deployment with AR, so that we may better determine the most effective strategies for climate change mitigation.

The project will investigate these interactions through a combination of measurements in field trials and numerical modelling. During the first phase, I will undertake a suite of BVOC measurements at the field site over 24 months using state of the art GC-MS with thermal desorption. In the second phase, I will use the measurements in combination with The Model of Emissions of Gases and Aerosols from Nature (MEGAN) embedded in an Earth System Model to simulate possible effects to estimate the consequences of ERW/AR co-deployment in the UK and globally.