Accelerating the carbon cycle: the ethics of enhanced weathering

Expanding the Library of Ions for Moisture-Swing Carbon Capture

Developing materials that can more efficiently and cheaply capture carbon dioxide from ambient atmospheric conditions is essential for improving negative emission technologies. This study builds on the promising moisture-swing modality for direct air capture of carbon dioxide by investigating the use of several new anions─orthosilicate, borate, pyrophosphate, tripolyphosphate, and dibasic phosphate─that when introduced into ion-exchange resins allow for the cyclable capture of CO2 under dry conditions and its release under wet conditions. These ions, as well as many others that failed to show moisture-swing performance, are tested and directly compared thermodynamically and kinetically to understand their differences. This includes the use of analytical approaches new to the carbon capture field, such as the correlation of adsorption isotherms to moisture-swing performance, the use of phase lag kinetics, the examination of the humidity-carbon capture hysteresis of the sorbents, and the precise quantification of ion loading using inductively coupled plasma-optical emission spectroscopy. Phosphate dibasic was found to have the largest mass-normalized CO2 moisture-swing capacity, whereas phosphate tribasic had the best performance when factoring in kinetics, and pyrophosphate had the highest swing capacity when normalizing on a per-ion or per-unit-charge basis. This work not only sheds light on ways to improve DAC but also provides insights pertinent to the advancement of gas separation, negative emission technologies, and sorbent materials.

Assessment of optimal conditions for the performance of greenhouse gas removal methods

In this study, a comparative literature-based assessment of the impact of operational factors such as climatic condition, vegetation type, availability of land, water, energy and biomass, management practices, cost and soil characteristics was carried out on six greenhouse gas removal (GGR) methods. These methods which include forestation, enhanced weathering (EW), soil carbon sequestration (SCS), biochar, direct air capture with carbon storage (DACCS) and bioenergy with carbon capture and storage (BECCS) were accessed with the aim of identifying the conditions and requirements necessary for their optimum performance. The extent of influence of these factors on the performance of the various GGR methods was discussed and quantified on a scale of 0-5. The key conditions necessary for optimum performance were identified with forestation, EW, SCS and biochar found to be best deployed within the tropical and temperate climatic zones. The CCS technologies (BECCS and DACCS) which have been largely projected as major contributors to the attainment of the emission mitigation targets were found to have a larger locational flexibility. However, the need for cost optimal siting of the CCS plant is necessary and dependent on the presence of appropriate storage facilities, preferably geological. The need for global and regional cooperation as well as some current efforts at accelerating the development and deployment of these GGR methods were also highlighted.

Exploring cross-national public support for the use of enhanced weathering as a land-based carbon dioxide removal strategy

This study explores how public attitudes across three countries influence support towards terrestrial enhanced weathering, whereby silicate minerals are applied to agricultural land to remove carbon dioxide from the atmosphere. An online survey was administered in Australia (N = 1000), the UK (N = 1000), and the USA (N = 1026) where there are ongoing field trials of this technique. Findings are similar across all three countries with many participants unfamiliar with enhanced weathering and unsure about supporting the use of enhanced weathering. Results show that positive affect is the main predictor for support of this technique, along with perceived benefits and level of concern about climate change. Open-ended questions asking why respondents would or would not support the use of enhanced weathering elicit mainly affective concepts, with enhanced weathering seen by individual respondents as either something mainly positive or mainly negative, with others saying it sounds risky and/or would have impacts on the environment. The way in which enhanced weathering is communicated is likely to influence support of the use of this strategy so must be undertaken carefully. Overall, our findings show that it is imperative to continue to engage the public, thereby allowing their views to be incorporated as enhanced weathering technology develops over time.

The Ethics of Geoengineering: A Literature Review

Geoengineering as a technological intervention to avert the dangerous climate change has been on the table at least since 2006. The global outreach of the technology exercised in a non-encapsulated system, the concerns with unprecedented levels and scales of impact and the overarching interdisciplinarity of the project make the geoengineering debate ethically quite relevant and complex. This paper explores the ethical desirability of geoengineering from an overall review of the existing literature on the ethics of geoengineering. It identifies the relevant literature on the ethics of geoengineering by employing a standard methodology. Based on various framing of the major ethical arguments and their subsets, the results section presents the opportunities and challenges at stake in geoengineering from an ethical point of view. The discussion section takes a keen interest in identifying the evolving dynamics of the debate, the grey areas of the debate, with underdeveloped arguments being brought to the foreground and in highlighting the arguments that are likely to emerge in the future as key contenders. It observes the semantic diversity and ethical ambiguity, the academic lop-sidedness of the debate, missing contextual setting, need for interdisciplinary approaches, public engagement, and region-specific assessment of ethical issues. Recommendations are made to provide a useful platform for the second generation of geoengineering ethicists to help advance the debate to more decisive domains with the required clarity and caution.