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Many projects are being funded around the world on a variety of greenhouse gas (GHG) removal concepts. Some of these appear to have gigaton pa potential once scaled up whereas others are less clear. Most of the work to date has been focused on land-based approaches which are focused on  tackling only carbon dioxide removal and not other GHGs. These range from nature-based solutions through to fully engineered direct air capture processes coupled with storage in underground reservoirs. The areas which are under-served in terms of research are:

  • Ocean-based approaches to carbon dioxide removal
  • Non CO2 greenhouse gases

We strongly favour approaches that simultaneously restore local ecosystems and remove GHGs from the atmosphere.  Biomimicry has many advantages in achieving this objective.

Ocean based approaches: Nature Based Solutions

There are groups already undertaking research in ocean-based approaches. These include overseas teams in Hawai'i, Woods Hole and Scripps. In the UK the teams at St Andrews, Southampton and Plymouth are the main centres. In Cambridge we have academics in Earth Science and Applied Maths who work on related projects in the oceans. Sasha Terchyn and Oscar Branson in Earth Sciences have research interests in the carbon cycle, and John Taylor from the Department of Applied Maths undertakes research on ocean currents, and has specific interests in the mixing between the upper and lower layers. Downing College, where the CCRC is headquartered, is now planning the appointment of a geographer in Climate Repair with expertise in marine sciences.  Sasha, Oscar and John are very interested in forming a team to develop this research area, and critically helping address two fundamental and as yet fully unanswered questions regarding the potential role for seaweeds, including kelp and sea grass, and ocean iron fertilisation:  

  • What is the ultimate fate of carbon once kelp or other carbon dioxide sinks such as sea grass, have died, and are there negative impacts such as de-oxygenation?
  • What are the factors which limit the scale of sequestration potential, and crucially which nutrients might be in short supply and could these potentially be supplemented through assisted mixing, movement of plants or additional material?

 

Research focused on furthering our understanding of the potential role of giant kelp as a source of restoring ocean wildlife and carbon sequestration will also be highly relevant to the topic of ocean iron fertilization, where phytoplankton growth could be stimulated with subsequent generation of potentially abundant fish species. There are synergies between these research areas. Field scale experimentation for kelp both in  coastal waters and deep waters is already underway. The modelling expertise provided by the Cambridge team will be extremely valuable for this research endeavour. However, additional expertise is required in the area of ocean bio-geochemistry, and this is part of the team development which is being planned. The Cambridge team will also liaise with partners at other universities as well as with commercial organisations working in the field. Relationships in the area of ocean iron fertilization are already established with the Goa Marine Research Institute in India, the University of Hawai'i and Incheon University. Relationships in the area of kelp are already in place with Kelp Blue and RunningTide.

 
Non CO2 greenhouse gases

The topic of methane removal is growing in importance as a result of the rate of increase of methane levels in the atmosphere – it is increasing at a similar rate (percentage growth rate) to carbon dioxide, albeit from a lower base (not just in terms of ppm but also CO2 equivalence).  There is great concern about the increase in release rate due to rising temperatures in the Arctic. There have been advances in tackling fugitive emissions especially when these are of sufficient flow rate and concentration that the gas can be used for power generation. However, there are few groups undertaking research to tackle methane in the atmosphere (currently 1-2ppm). One of the options which has been suggested involves the use of iron salt aerosols, where iron chloride is injected into the atmosphere. Some chlorine atoms (radicals) are generated and this can then serve as a catalyst to enable the conversion of methane and oxygen to carbon dioxide and water. Peter Fiekowsky in the US is progressing this idea. An alternative approach is to use a metal oxide as a catalyst in the presence of sunlight (or other UV source), and to pass air over the catalyst. The methane in contact with the catalyst will convert to carbon dioxide. The advantage of the metal oxide idea is that it doesn’t involve the release of material into the atmosphere (which might invoke some challenges in terms of social acceptability and will also require an on-going source of material to be provided), although it does require the installation of a system which can move large quantities of air across the photocalyst surfaces. Photocatalysis using a metal oxide is relatively under-researched. Zhiguo Yi from Shanhai Institute of Ceramics has undertaken some preliminary research and identified zinc oxide decorated with silver as a potential photocatalyst. However, whilst the results are very promising there is a lot more research needed in order to assess how the small-scale setup can be expanded to industrial scale, and also whether that particular catalyst is the preferred one. We are in discussion with Junwang Tang, Ivan Parkin and Raul Quesada Cabrera from UCL who are working on reviewing the options including a range of factors and not just activity rate: abundance (relates to cost), lifetime, scalabilty/manufacturability. There are important questions regarding the arrangement of the flows required to ensure adequate contact time between the methane and the photocatalyst. The Cambridge team brings a depth of understanding of fluid mechanics and the mixing processes which will be key to determining how to scale up the system. The academic colleagues from the Department of Applied Mathematics have skills in a range of mathematical modelling approaches including the development of analytical models as well as the use of computational fluid dynamics.

 
Other greenhouse gas removal projects

We will pursue and support other projects if opportunities arise which can strengthen the contributions of CCRC. The two which we have identified thus far are direct air capture of carbon dioxide and enhancement of soil carbon content. 

 The direct air capture project is funded by BEIS and involves team members from Engineering and Chemical Engineering in Cambridge and a collaboration with Carbon Engineering, Pale Blue Dot and Edinburgh University. Importantly, Carbon Engineering is one of the leading companies in the field of Direct Air Capture and one of the most established – they already have a pilot plant in Canada with a number of others under construction. This project involves design of a new process for regenerating the contactors and to avoid the current use of methane; the options include direct electrical heating which has challenges regarding non-uniform heat distribution using standard element design, or a switch from methane to hydrogen and hence retainment of a hot gas principle for heating.

The enhancement of soil carbon content is a project being led by Prof David Coomes from Plant Science. The project is currently unfunded but a NERC grant application is being prepared. Cambridge University has been successful in the outline application and is now preparing the detailed plan submission. CCRC will contribute to the project in the area of measurement of carbon content. The current methods are very labour intensive and expensive, and the university has great strength in physics, chemistry, engineering and earth sciences which can support the development of new sensors and measurement techniques including signal processing of data from ground-based devices as well as satellite images.