About This Project

Caves are known to function as massive sink of atmospheric methane. However, the potential for artificial mines to serve a similar role, remains unknown. With engineered interventions, mines are a promising target for greenhouse gas (GHG) removal. This project will determine the biogeochemical basis, to enhance microbial GHG uptake in mines. This will be achieved through integrating environmental sampling with gas flux measurement, physicochemical profiling, and advance omics

Ask the Scientists

Motivating Factor

The rapid rise in methane (CH₄) is a leading cause of global warming, yet strategies to directly remove this gas from air are limited. CH₄ oxidizing bacteria, are the sole biological mediator of this process, but their abundance and activities in most environments are low. Caves are a notable exception where these bacteria are consistently abundant and active^1–4. Recent estimates show that the atmospheric CH₄ sink in limestone caves, is comparable to that in surface soils⁵. Cave microbes also remove other climate-active gases such as H₂ and CO and convert CO₂ into biomass⁴. We propose that artificial mines, can be enhanced to function as natural bioreactors to simultaneously remove multiple GHGs, e.g. via ventilation and atmospheric draw-down. This approach differs from other ecosystem engineering solutions, in that it leaves the aboveground landscape undisturbed. A key priority of this solution is to understand what factors limit or promote GHG uptake by underground communities.

Specific Bottleneck

While microbial atmospheric CH₄ uptake has been documented in cave ecosystems, data on the ability and activity of microbial communities in processing other climate-active gases (e.g. H₂, CO, CO₂) is lacking, hindering gross estimation of net underground GHG removal potential⁶. The conditions that promote or constrain this climate-relevant process are also minimally explored, which is a crucial prerequisite for designing strategies to enhance underground GHG sink. Early data suggest air exchange between underground atmosphere and land surface⁷ and seasonal humidity variation³ may be limiting methanotrophs and net CH₄ removal, representing an area for intervention. However, these insights require systematic evaluation. It also remains unknown if high microbial GHG uptake ability and activities occur in artificial mines, in which these manmade underground structures may serve as the prime target for repurposing as natural bioreactors for GHG removal

Actionable Goals

Systematic and interdisciplinary surveys to profile physiochemistry, GHG uptake/production activities, and microbial communities across natural caves and mines should be performed to quantify potentials of the underground GHG sink, integrating the following:

1. Field monitoring of CH₄, CO₂, H₂, CO, and N₂O fluxes across seasons.

2. Profiling of cave/mine physicochemical conditions, including wind speed (ventilation rate), air humidity, temperatures, rock geology, and weather history.

3. Measuring the activities of sediment/rock/surface biofilm microbial communities to consume GHG at various temperature and moisture conditions.

4. Metagenomic and metatranscriptomic investigation of active microbial mediators of GHG uptake.

5. Upscaling modelling to estimate the overall GHG removal capacity.

These data should be integrated to evaluate optimal conditions that promote microbial GHG removal and inform feasible enhancement strategies for testing.