CO2 removal and 1.5 °C: what, when, where, and how?

The international community aims to limit global warming to 1.5 °C, but little progress has been made towards a global, cost-efficient, and fair climate mitigation plan to deploy carbon dioxide removal (CDR) at the Paris Agreement's scale. Here, we investigate how different CDR options—afforestation/reforestation (AR), bioenergy with carbon capture and storage (BECCS), and direct air carbon capture and storage (DACCS)—might be deployed to meet the Paris Agreement's CDR objectives. We find that international cooperation in climate mitigation policy is key for deploying the most cost-efficient CDR pathway—comprised of BECCS, mainly (74%), and AR (26%)—, allowing to take the most advantage of regional bio-geophysical resources and socio-economic factors, and time variations, and therefore minimising costs. Importantly, with international cooperation, the spatio-temporal evolution of the CDR pathway differs greatly from the regional allocation of the Paris Agreement's CDR objectives—based on responsibility for climate change, here used as a proxy for their socio-economically fair distribution. With limited, or no international cooperation, we find that the likelihood of delivering these CDR objectives decreases, as deploying CDR pathways becomes significantly more challenging and costly. Key domestic bio-geophysical resources include geological CO2 sinks, of which the absence or the current lack of identification undermines the feasibility of the Paris Agreement's CDR objectives, and land and biomass supply, of which the limited availability makes them more costly—particularly when leading to the deployment of DACCS. Moreover, we show that developing international/inter-regional cooperation policy instruments—such as an international market for negative emissions trading—can deliver, simultaneously, cost-efficient and equitable CDR at the Paris Agreement's scale, by incentivising participating nations to meet their share of the Paris Agreement's CDR objectives, whilst making up for the uneven distribution of CDR potentials across the world. Crucially, we conclude that international cooperation—cooperation policy instruments, but also robust institutions to monitor, verify and accredit their efficiency and equity—is imperative, as soon as possible, to preserve the feasibility and sustainability of future CDR pathways, and ensure that future generations do not bear the burden, increasingly costlier, of climate mitigation inaction

A comparative analysis of the efficiency, timing, and permanence of CO2 removal pathways

Carbon dioxide removal (CDR) is essential to deliver the climate objectives of the Paris Agreement. Whilst several CDR pathways have been identified, they vary significantly in terms of CO2 removal efficiency, elapsed time between their deployment and effective CO2 removal, and CO2 removal permanence. All these criteria are critical for the commercial-scale deployment of CDR. In this study, we evaluate a set of archetypal CDR pathways—including afforestation/reforestation (AR), bioenergy with carbon capture and storage (BECCS), biochar, direct air capture of CO2 with storage (DACCS) and enhanced weathering (EW)—through this lens. We present a series of thought experiments, considering different climates and forest types for AR, land types, e.g. impacting biomass yield and (direct and indirect) land use change, and biomass types for BECCS and biochar, capture processes for DACCS, and rock types for EW. Results show that AR can be highly efficient in delivering CDR, up to 95–99% under optimal conditions. However, regional bio-geophysical factors, such as the near-term relatively slow and limited forest growth in cold climates, or the long-term exposure to natural disturbances, e.g. wildfires in warm and dry climates, substantially reduces the overall CO2 removal efficiency of AR. Conversely, BECCS delivers immediate and permanent CDR, but its CO2 removal efficiency can be significantly impacted by any initial carbon debt associated with (direct and indirect) land use change, and thereby significantly delayed. Biochar achieves low CDR efficiency, in the range of 20–39% when it is first integrated with the soil, and that regardless of the biomass feedstock considered. Moreover, its CO2 removal efficiency can decrease to −3 to 5% with time, owing to the decay of biochar. Finally, as for BECCS, DACCS and EW deliver permanent CO2 removal, but their CO2 removal efficiencies are substantially characterized by the energy system within which they are deployed, in the range of −5 to 90% and 17–92%, respectively, if currently deployed. However, the CDR efficiency of EW can increase to 51–92% with time, owing to the carbonation rate of EW

Investigating the BECCS resource nexus: delivering sustainable negative emissions

Bioenergy with carbon capture and storage (BECCS), and other negative emissions technologies (NETs), are integral to all scenarios consistent with meeting global climate ambitions. BECCS's ability to promptly remove CO2 from the atmosphere in a resource efficient manner, whilst being a net energy generator to the global economy, remains controversial. Given the large range of potential outcomes, it is crucial to understand how, if at all, this technology can be deployed in a way which minimises its impact on natural resources and ecosystems, while maximising both carbon removal and power generation. In this study, we present a series of thought experiments, using the Modelling and Optimisation of Negative Emissions Technologies (MONET) framework, to provide insight into the combinations of biomass feedstock, origin, land type, and transport route, to meet a given CO2 removal target. The optimal structure of an international BECCS supply chain was found to vary both quantitatively and qualitatively as the focus shifted from conserving water, land or biomass, to maximising energy generated, with the water use in particular increasing threefold in the land and biomass use minimisation scenario, as compared to the water minimisation scenario. In meeting regional targets, imported biomass was consistently chosen over indigenous biomass in the land and water minimisation scenarios, confirming the dominance of factors such as yield, electricity grid carbon intensity, and precipitation, over transport distance. A pareto-front analysis was performed and, in addition to highlighting the strong trade-offs between BECCS resource efficiency objectives, indicated the potential for tipping points. An analysis of the sensitivity to the availability of marginal land and agricultural residues showed that (1) the availability of agricultural residues had a great impact on BECCS land, and that (2) water use and land use change, two critical sustainability indicators for BECCS, were negatively correlated. Finally, we showed that maximising energy production increased water use and land use fivefold, and land use change by two orders of magnitude. It is therefore likely that an exclusive focus on energy generation and CO2 removal can result in negative consequences for the broader environment. In spite of these strong trade-offs however, it was found that BECCS could meet its electricity production objective without compromising estimated safe land use boundaries. Provided that the right choices are made along BECCS value chain, BECCS can be deployed in a way that both satisfies its resource efficiency and technical performance objectives

Pension reforms, risk transfer and housing finance innovations

Weak housing creditor protection, accentuated by weak landed property rights and underdeveloped credit information systems constitute major constraints to housing finance development in many developing countries. Improving housing creditor protection require further institutional development and financial innovation. As a trigger of financial innovation, regulation has spawned pension reforms leading to the global shift from defined benefit to defined contribution pension schemes, which has created new opportunities to improve housing creditor protection and thus engender housing finance innovations. This paper considers how pension assets—accumulated benefits and associated personal, employment and contribution information—has provided a basis for collateralized lending and an additional avenue for credit information system development. The paper proposes a pension asset-backed creditor protection model that utilizes defined contribution pension assets to improve housing credit allocation, and thus, housing finance development. Pension assets represent alternative or complementary collateral assets for securing a housing credit (mortgage). And as depositories of information, the information content of pension assets and institutions could also be used alternatively and complementarily to assess the capacity, character and contribution (equity) of potential borrowers in the credit underwriting process. Future applied research may consider how the proposed model could be integrated in existing credit underwriting systems and the operational challenges that could emerge