The Idea, or the need for negative CO2 emissions  

The Challenge: the need of doing more

The climate crisis is a consequence of the rapid increase of the carbon dioxide (CO2) concentration in the atmosphere. The current focus on reducing CO2 emission alone will not be sufficient to reach net zero emissions. We also must actively remove CO2 from Earth’s atmosphere, and therefore invest in large-scale deployment of carbon dioxide removal (CDR) techniques. 

By 2050 at the latest a combination of different CDR techniques needs to enable active CO2 removal from the atmosphere on a gigaton scale: an urgent and enormous challenge, but still in an early research stage in regards to feasibility, effectiveness and impact. Coastal Carbon aims to accelerate this process by focussing our research on one of the most promising CDR techniques: Enhanced Silicate Weathering.

The Idea: accelerating a natural process

Enhanced silicate weathering is one of the promising CO2 removal approaches. The idea is based on the natural process of silicate rock weathering. Weathering of silicate minerals results in the release of alkalinity as solution products. Increased alkalinity increases the capacity of seawater to capture CO2 from the atmosphere.

Silicate weathering stabilizes Earth’s climate over long timescales. However, this natural process is too slow to offer a rapid solution for the recent rises in atmospheric CO2. The rationale behind enhanced silicate weathering is to speed up the natural process and thereby accelerate the drawdown of atmospheric CO2 by taking fast weathering silicate rocks, increasing their reactive surface area by grinding it to sand, and distributing these sands in locations with high weathering rates. 

Coastal zones, where sediments occur naturally, are highly favorable for the application of enhanced silicate weathering. Waves and currents keep the mineral grains in motion, inducing collisions between sediment particles, and preventing local build up of dissolution products.

Our Research Questions

The potential of the coastal enhanced silicate weathering technology is highly promising but requires further study. Coastal Carbon conducts large-scale experiments investigating the rate of enhanced silicate weathering and associated CO2 uptake under realistic natural settings as well as potentially important influences on the biogeochemical cycling in coastal ecosystems (release of trace metals, alkalinity and dissolved silicate). Research is done at our unique mesocosm facility in Ostend, Belgium and in natural environments, where we focus on the following questions:

What are the impacts of enhanced silicate weathering on the ecosystem?

Application of enhanced silicate weathering will affect the coastal environment. In the short term, addition of fast weathering silicates will induce an immediate alteration of the composition of the coastal sediment. In the long term, silicate weathering releases a specific mix of weathering products into coastal waters, which could have a range of effects on the surrounding ecosystem. 

Currently, these ecosystem impacts are poorly understood. A thorough evaluation of ecosystem effects is crucial before enhanced silicate weathering can be applied on a large scale. Coastal Carbon takes a first step in assessing the environmental impact by focusing on the release of trace metals associated to the weathering silicate minerals, tracing their bio-accumulation in sediment animals, and verifying whether the enhanced silicate weathering influences l macrofauna communities.

Can animals and microbes in the seabed stimulate silicate weathering?

As a result of the burrowing activities of macrofauna, sediment particles get redistributed and the exchange of pore water with the overlying water is stimulated. This bioturbation lowers accumulation of weathering end-products, provides a favorable environment for weathering and has thus the potential to enhance silicate weathering.

Microbial communities in the seabed decompose organic matter, releasing CO2 and acidity to the sediment pore water. Since acid increases the dissolution rate of silicate minerals, this could accelerate silicate weathering. An environment with high biological activity is therefore favorable for enhanced silicate weathering applications.

As their impacts on the biochemistry of the marine sediments, both macrofauna and the microbial community are expected to enhance silicate weathering. However, the interaction between silicate weathering and organisms remains largely unknown. Coastal Carbon aims to unravel these interactions to understand if weathering rates could be higher under natural marine conditions compared to sterile lab conditions.

Is enhanced silicate weathering in coastal environments economically feasible?

Silicate weathering draws down CO2 from the atmosphere to the marine system and stores the sequestered CO2 for thousands of years. Future earnings from coastal silicate weathering largely depend on the price of CO2 credits and the speed at which CO2 can be captured from the atmosphere. The costs of the process, in both cash and CO2, are determined by mining, grinding, transport and application of the silicate.

So far, the research has focused mainly on the determination of olivine dissolution rates. However, the economic feasibility and global potential of coastal silicate weathering remains uncertain. Coastal Carbon aims to establish an economic cost model for calculating the cost effectiveness of silicate weathering and determining ideal weathering conditions.

Coastal Carbon is a research project, focusing on coastal enhanced silicate weathering (ESW), a negative emissions technology (NET) that uses the natural process of silicate weathering for the removal of CO2 from the atmosphere.

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