Carbon dioxide removal

Ocean Afforestation, more precisely Ocean Macroalgal Afforestation (OMA), has the potential to reduce atmospheric carbon dioxide concentrations through expanding natural populations of macroalgae, which absorb carbon diox- ide, then are harvested to produce biomethane and biocarbon dioxide via anaerobic digestion. The plant nutrients remaining after digestion are recycled to expand the algal forest and increase fish populations. A mass balance has been calculated from known data and applied to produce a life cycle assessment and economic analysis. This analysis shows the potential of Ocean Afforestation to produce 12 billion tons per year of biomethane while stor- ing 19 billion tons of CO2 per year directly from biogas production, plus up to 34 billion tons per year from carbon capture of the biomethane combustion exhaust. These rates are based on macro-algae forests covering 9% of the world’s ocean surface, which could produce sufficient biomethane to replace all of today’s needs in fossil fuel energy, while removing 53 billion tons of CO2 per year from the atmosphere, restoring pre-industrial levels. This amount of biomass could also increase sustainable fish production to potentially provide 200 kg/yr/person for 10 billion people. Additional benefits are reduction in ocean acidification and increased ocean primary productivity and biodiversity.

Oceans, islands, and coastal areas are at least
could add several thousand Gt of CO2. Since it is very difficult to economically remove the other global warming gases, climate efforts should develop more systems for the rapid removal and secure storage of at least of 2,000 Gt of CO2.
N’Yeurt et al. [5] proposed an economical and ecological way to reduce total carbon emissions as well as capture existing CO2: ocean macroalgal afforestation (OMA). In fact, compared to other negative carbon technologies reviewed by McLaren [6], [7] and McGlashan et al. [8], macroalgae capture of CO2 from air and water may be the most feasible method to remove many thousand Gt of CO2. OMA would require an ocean-accessible secure storage method, such as that proposed in this paper.
Fig. 1. Projected cumulative CO2 emissions from energy since 1960 (based on U.S. EIA data [4])
Most of the proposals for sequestering CO2 involve deep sub-earth geologic structures limited to relatively small areas in continental plates. In addition, some authors have expressed concern about potential leakage ([9]-[12]). Farhat et al. [13] recently examined saline aquifers potential for only interim storage purposes.
This paper assesses the potential for Secure Seafloor Container Storage (SSCS) to store CO2 on the seafloor in secure containers that eventually become similar to geologic formations over millennia. The paper presents a computational geophysical, chemical, and economic model of SSCS, including:
• How typical ocean pressures, temperatures, biota, seafloor seafloor sediments, and CO2 in water affect the service life of geosynthetic structures on the seafloor.
• Details of the concentrations, volumes, density stability, chemical stability, and structural properties of CO2 and water inside a geosynthetic structure on the seafloor.
• The thermo chemical stability of CO2 hydrate in geomembranes.
• The fluid dynamics of SSCS.
• The transparency of monitoring, maintaining, and in-situ
improving the containers.
• The economics of SSCS.
Section II briefly reviews other storage technologies. Section III summarizes some advantages of SSCS. Section IV discusses the security of geosynthetic materials for CO2 storage. Section V provides an introductory economic analysis and life cycle assessment. Section VI focuses on the physics,
as
atmospheric greenhouse gas concentrations as the remaining 30% of Earth’s surface. Yet most of the discussion for sequestering the dominant greenhouse gas, CO2, involves deep sub-earth geologic structures limited to relatively small areas in continental plates. Humanity needs a secure carbon storage alternative that is available in more countries. Secure Seafloor Container Storage (SSCS) is an alternative that could safely store trillions of tons of CO2. The paper presents a computational geophysical, chemical, and economic model of SSCS. Our research shows that appropriate undisturbed geosynthetics will prevent contact with seawater for millennia (<0.06% osmosis loss per millennium). CO2 hydrate below 500 meters is a rock-like solid denser than water. Our life cycle assessment predicts a mass ratio of stored-CO2:materials needed of 1,700:1. The projected cost to compress pure gaseous CO2 to a liquid, convert the liquid to hydrate inside a geosynthetic membrane, monitor and maintain the structures is approximately $16 per ton of CO2.

Targets and accounting for negative emissions should be explicitly set and managed separately from existing and future targets for emissions reduction. Failure to make such a separation has already hampered climate policy, exaggerating the expected future contribution of negative emissions in climate models, while also obscuring the extent and pace of the investment needed to deliver negative emissions. Separation would help minimize the negative impacts that promises and deployments of negative emissions could have on emissions reduction, arising from effects such as temporal trade-offs, excessive offsetting, and technological lock-in. Benefits for international, national, local, organizational, and sectoral planning would arise from greater clarity over the role and timing of negative emissions alongside accelerated emissions reduction.

Despite the ambitious temperature goal of the 2015 Paris Agreement, the pace of reducing global CO2 emissions remains sluggish. This creates conditions in which the idea of temperature ‘overshoot and peak-shaving’ is emerging as a possible strategy to meet the Paris goal. An overshoot and peak-shaving scenario rests upon the ‘temporary’ use of speculative solar radiation management (SRM) technologies combined with large-scale carbon dioxide removal (CDR). Whilst some view optimistically the strategic interdependence between SRM and CDR, we argue that this strategy comes with a risk of escalating ‘climate debt’. We explain our position using the logic of debt and the analogy of subprime mortgage lending. In overshoot and peak-shaving scenarios, the role of CDR and SRM is to compensate for delayed mitigation, placing the world in a double debt: ‘emissions debt’ and ‘temperature debt’. Analogously, this can be understood as a combination of ‘subprime mortgage’ (i.e. large-scale CDR) and ‘home-equity-line-of-credit’ (i.e. temporary SRM). With this analogy, we draw some important lessons from the 2007–2009 US subprime mortgage crisis. The analogy signals that the efficacy of temporary SRM cannot be evaluated in isolation of the feasibility of large-scale CDR and that the failure of the overshoot promise will lead to prolonged peak-shaving, masking an ever-rising climate debt. Overshoot and peak-shaving scenarios should not be presented as a secured feasible investment, but rather as a high-risk speculation betting on insecure promises. Obscuring the riskiness of such scenarios is a precipitous step towards escalating a climate debt crisis.

Geoengineering (the deliberate modification of the climate system), has been discussed as a technique to control Anthropogenic Global Warming (AGW). Public Trust Doctrine (PTD) is used to hold assets that are not in private ownership in a form of collective ownership for public benefit; it is familiarly applied to the shoreline between tides. Several variants of PTD exist, yet all variants serve to limit private ownership. The version arising from Anglo-American common law creates duties and responsibilities on the sovereign to maintain and preserve assets in public trust. We consider various types of geoengineering to protect example assets currently under PTD, finding a compelling case for action in a variety of contexts. This introduces a paradoxical situation, where it may theoretically be easier to compel states to undertake geoengineering to protect a beach, than to protect the whole planet. We note that, whilst PTD obligations are atomised in nature, the inherent commonality of the threat potentially serves to reduce this fragmentation, and to encourage common action amongst states. However, we note the failure of recent legal proceedings, which exposes practical limitations on the ability of PTD to compel climate action generally – and thus its applicability to geoengineering.

Greenhouse gas removal (GGR) raises many cultural, ethical, legal, social, and political issues, yet in the growing area of GGR research, humanities and social sciences (HASS) research is often marginalized, constrained and depoliticised. This global dynamic is illustrated by an analysis of the UK GGR research programme. This dynamic matters for the knowledge produced and for its users. Without HASS contributions, too narrow a range of perspectives, futures and issues will be considered, undermining or overpromising the prospects for the responsible development of GGR (and threatening worse side-effects), and limiting our understanding of why and how policy demands GGR solutions in the first place. In response, we present policy principles for bringing HASS fully into GGR research, organized around three themes: (1) HASS-led GGR research, (2) Opening up GGR futures, and (3) The politics of GGR futures.

There is growing interest in bioenergy with carbon capture and storage (BECCS) as a possible technology for removing CO2 from the atmosphere. In the first study of its kind, we investigate whether and how different forms of incentivisation impact on public perceptions of this technology. We develop a new experimental method to triangulate perceptions of BECCS in different policy scenarios through quantitative measurement and qualitative elicitation. Here we show that the type of policy instrument used to incentivise BECCS significantly affects perceptions of the technology itself. While we find approval of coercive and persuasion-based policy scenarios for incentivisation, supportive instruments proved polarising. Payments based on the amount of CO2 removed from the atmosphere were approved, but guarantees of higher prices for producers selling energy derived from BECCS were strongly opposed. We conclude that public support for BECCS is inextricably linked to attitudes towards the policies through which it is incentivised.

District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand – outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations. Abstract It has been globally recognized as necessary to reduce greenhouse gas (GHG) emissions for mitigating the adverse effects of global warming on earth. Carbon dioxide (CO2) capture and storage (CCS) technologies can play a critical role to achieve these reductions. Current CCS technologies use several different approaches including adsorption, membrane separation, physical and chemical absorption to separate CO2 from flue gases. This study aims to evaluate the performance and energy savings of CO2 capture system based on chemical absorption by installing an intercooler in the system. Monoethanolamine (MEA) was used as the absorption solvent and Aspen HYSYS (ver. 9) was used to simulate the CO2 capturing model. The positioning of the intercooler was studied in 10 different cases and compared with the base case 0 without intercooling. It was found that the installation of the intercooler improved the overall efficiency of CO2 recovery in the designed system for all 1-10 cases. Intercooler case 9 was found to be the best case in providing the highest recovery of CO2 (92.68%), together with MEA solvent savings of 2.51%. Furthermore, energy savings of 16 GJ/h was estimated from the absorber column alone, that would increase many folds for the entire CO2 capture plant. The intercooling system, thus showed improved CO2 recovery performance and potential of significant savings in MEA solvent loading and energy requirements, essential for the development of economical and optimized CO2 capturing technology.

La propuesta consiste en diseñar, probar, validar y aplicar la metodología que permitirá  la exitosa operación, en el mercado de bonos de captura de carbono, de una asociación de los ejidos asentados en los estados mexicanos de Quintana Roo, Campeche y Yucatán.

In this study, we utilize a large and diverse expert interview exercise (N = 125) to critically examine the whole systems justice issues associated with ten negative emissions and ten solar geoengineering technologies. We ask: What equity and justice concerns arise with these 20 options? What particular vulnerable groups could be affected? What risks do these options entail for communities or the climate? Utilizing a "claims making" approach, we examine existing and prospective injustices across a pluralistic whole systems framework analyzing (i) resource extraction issues including minerals, chemicals, and fertilizers (ii) manufacturing, labor and ownership concerns, (iii) transportation-network and land-grabbing dynamics, (iv) unfair and exclusionary policymaking and planning, (v) operational injustices resulting from deployment and use, and (vi) waste flows, liabilities and disposal requirements. We then explore how these potential concerns culminate in a milieu of injustice cutting across the dimensions of distribution (who gets what), recognition (who counts), participation (who gets heard), capabilities (what matters), and responsibility (who does what). We conclude with insights for both policy and future research.

Most scenarios on instruments limiting global warming in line with the 1.5 °C temperature limit of the Paris Agreement rely on overshooting the emissions threshold, thus requiring the application of negative emission technologies later on. Subsequently, the debate on carbon dioxide removal (CDR) and solar radiation management (SRM) (frequently subsumed under “geoengineering”) has been reinforced. Yet, it does not determine normatively whether those are legally valid approaches to climate protection. After taking a closer look at the scope of climate scenarios and SRM methods compiling current research and opinions on SRM, this paper analyses the feasibility of geoengineering and of SRM in particular under international law. It will be shown that from the perspective of human rights, the Paris Agreement, and precautionary principle the phasing-out of fossil fuels and the reduction in consumption of livestock products as well as nature-based approaches such as sustainable—and thus climate and biodiversity-smart—forest, peatland, and agricultural management strongly prevail before geoengineering and atmospheric SRM measures in particular. However, as all of the atmospheric SRM methods are in their development phase, governance options to effectively frame further exploration of SRM technologies are proposed, maintaining that respective technologies thus far are not a viable means of climate protection.

There is increasing urgency for large-scale deployment of carbon-removal approaches to help avoid passing
critical climatic thresholds.Given the severe risks of many terrestrial methods at extremely large scales, there
is a compelling need to also assess the potential of marine negative-emissions technologies, such as artificial ocean alkalinization.