| dc.description.abstract | Natural silicate weathering has always taken part in the geological CO2 sink that has helped stabilize atmospheric CO2 concentrations. Since this reaction is naturally slow, enhanced silicate weathering (ESW) is proposed to accelerate this process and potentially sequester higher amount of CO2. This method falls under negative carbon emission technologies (NETs), which is necessary to slow down anthropogenic climate change. The overall potential, however, depends on the availability of suitable rocks and proximity to the spreading locations. In this thesis research, the potential and environmental implications of enhanced weathering of olivine in arable lands of Europe were studied. The research objective is to mitigate 10% of EU’s 2017 total CO2 emissions by 2050, with the mineral sourced from the biggest olivine quarry in Norway. Dunite in this quarry has high purity (~92%) of olivine, which has high dissolution reactivity. Through the shrinking core model and detailed calculations, the potential amount of olivine weathered, the net CO2 sequestered, the CO2 penalty, and the accumulation of nickel in the topsoil were investigated. Scenarios were made for selected countries in Europe (northern and southern Europe) and most European countries. It was found that, for European scale, the current mining production in Norway needs to be increased 500-1000 times to achieve the target. Suitable pH soil for terrestrial ESW is 5-7, and 75 µm and 30 µm were chosen based on the shrinking core model. At soil pH of 7-8, weathering can still proceed, although it requires 10 µm grain size for a considerable weathering amount, e.g. 70-80% weathered in 25 years. This was proven to be highly inefficient, resulting to more CO2 being emitted than sequestered. Of all the mechanical processes involved to spread grounded olivine on arable land, transport contributed to the highest reduction of CO2 potential. However, fast weathering rates are found in countries with higher mean annual temperature, which are remotely located from the source. All scenarios meeting the targets also resulted to substantial amount of nickel accumulation in the topsoil by 2050. These amounts exceed the Dutch’s maximum permissible addition (MPA) value of 0.26 mg Ni/kg topsoil. However, this is dependent on the weathering rate, which differs strongly by geographical locations. Overall, the main uncertainties lie in the weathering rate. Further research involving other environmental interactions not considered here, such as increase of soil pH upon olivine weathering or biotic activity is needed. | |
