Carbon footprint of terrestrial and coastal enhanced weathering systems for carbon sequestration

One of the solutions to reduce carbon emissions is enhanced weathering (EW) using basalt. EW is defined as the artificial acceleration of the weathering process of silicate-bearing rocks for carbon sequestration. Life cycle carbon footprint analysis is utilized in this study to analyze the potential of EW. This method calculates the greenhouse gas (GHG) emissions produced from quarry, crushing, transportation, application operations, and the extracted carbon dioxide (CO2) from the atmosphere through the chemical reaction of silicates in basalt. These values were used to compute the net carbon dioxide removal (CDR). The net CDR is defined as the stoichiometric CDR from the weathering reactions minus the GHG emissions from all activities in the system. The effect of distance between basalt sources (quarries) and sinks (application site) was found to have a major effect on net CDR. The break-even distance at which net CDR becomes zero was determined for both types of EW. Results showed that coastal EW removes more carbon than terrestrial EW for any given transportation distance. In addition, the gap in net CDR is equivalent to terrestrial EW to coastal EW at a transportation distance of about 180 km. The distance at which net CDR drops to zero for terrestrial and coastal EW are 129 km and 302 km, respectively. Furthermore, representative basalt sources (quarries) and sinks (application site) from the Philippines are shown to illustrate the plausibility of EW for the Philippine setting. The results stayed consistent that coastal EW removes more carbon than terrestrial EW