Abstract
Negative emission technologies (NETs) target the removal of carbon dioxide (CO2) from the atmosphere, and are being actively investigated as a strategy to limit global warming to within the 1.5–2°C targets of the 2015 UN climate agreement. Enhanced silicate weathering (ESW) proposes to exploit the natural process of mineral weathering for the removal of CO2 from the atmosphere. Here, we discuss the potential of applying ESW in coastal environments as a climate change mitigation option. By deliberately introducing fast-weathering silicate minerals onto coastal sediments, alkalinity is released into the overlying waters, thus creating a coastal CO2 sink. Compared with other NETs, coastal ESW has the advantage that it counteracts ocean acidification, does not interfere with terrestrial land use and can be directly integrated into existing coastal management programmes with existing (dredging) technology. Yet presently, the concept is still at an early stage, and so two major research challenges relate to the efficiency and environmental impact of ESW. Dedicated experiments are needed (i) to more precisely determine the weathering rate under in situ conditions within the seabed and (ii) to evaluate the ecosystem impacts—both positive and negative—from the released weathering products.
Highlights
Negative emission technologies (NETs) target the removal of carbon dioxide (CO2) from the atmosphere, and are being actively investigated as a strategy to limit global warming to within the 1.5–28C targets of the 2015 UN climate agreement
Application will be restricted to arable land, and so land availability may be a limiting factor, in addition to saturation in the pore water, which has been suggested as another important limitation on the maximal CO2 sequestration achievable by terrestrial Enhanced silicate weathering (ESW)
A large body of knowledge exists on marine biogeochemistry, and insights can be gained by analogy with other impacts, we contend that a proper assessment of the ecosystem-level impacts of ESW will necessitate a combination of mesocosm studies and large-scale field trials, given the complexity of marine ecosystem functioning
Summary
To achieve the goals of the 2015 UN climate agreement, it will not be sufficient to solely reduce greenhouse gas emissions, and CO2 needs to be actively captured from the atmosphere [1,2]. The open ocean has the major disadvantage that olivine particles must be ground to a very small size (less than 1 mm), or else particles rapidly sink out of the surface mixed layer before being dissolved, which will not lead to an immediate CO2 uptake [15]. These small grain sizes lead to a high energy expenditure and associated CO2 emissions during grinding [12], rendering the overall CO2 sequestration inefficient.
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