Alexandra May / Earth & Environmental Sciences / Faculty Mentor: Ricardo Sanchez-Murillo
The global demand for hydrogen is rapidly increasing and is anticipated to reach 500 Mt/year by 2050. The discovery of widespread, natural H2 seepages (hereafter GeoH2) offers enormous potential for C-free energy-based solutions. Low temperature serpentinization (<122°C) of ultramafic rocks has been regarded as one of the major pathways of GeoH2. Rainfall amounts in tropical, monsoonal serpentinization settings enhance infiltration and groundwater recharge. Thus, water-rock interactions are hypothesized to be more favorable for GeoH2 production than arid or temperate sites across the globe. Here, we present the results from a unique tropical serpentinization environment discovered in the Santa Elena Peninsula, Costa Rica (SEO). This site is characterized by hyperalkaline springs (pH=11.01-11.59) with low Mg2+ (1.0-1.8 mg/L) and relatively high Ca2+ (17-167 mg/L), Cl- (23-36 mg/L), hydroxide (13-87 mg/L), and carbonates (20-134 mg/L). The high GeoH2 concentrations reported at SEO (10-2 to 101 mM) have only been measured in laboratory experiments at high temperatures (>200°C). Consequently, the mechanism controlling the high GeoH2 concentrations must involve high water-rock ratios and possibly catalysis by trace Fe-Ni alloys rather than high temperatures. Timely advancement of GeoH2 exploration, extraction, and storage techniques can help establish the US as a global leader in clean H2 production.
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