Doctoral Program - Siwar Saadaoui
Siwar Saadaoui joined The CarMa research team on november 21, 2022 when she joined the AgroParisTech / Cired team under the supervision of Dr. Benoît Gabrielle and Dr. Thierry Brunelle (CIRAD/CIRED)
Carbon dioxide removal (CDR) is crucial to achieve the Paris Agreement's 1.5 °C–2 °C goals. However, climate mitigation scenarios have primarily focused on bioenergy with carbon capture and storage (BECCS), afforestation/reforestation, and recently direct air carbon capture and storage (DACCS). This narrow focus exposes future climate change mitigation strategies to technological, institutional, and ecological pressures by overlooking the variety of existing CDR options, each with distinct characteristics—including, but not limited to, mitigation potential, cost, co-benefits, and adverse side-effects. This study expands the scope by evaluating CDR portfolios, consisting of any single CDR approach—BECCS, afforestation/reforestation, DACCS, biochar, and enhanced weathering—or a combination of them. We analyse the value of deploying these CDR portfolios to meet 1.5 °C goals, as well as their global and regional implications for land, energy, and policy costs. We find that diversifying CDR approaches is the most cost-effective net-zero strategy. Without the overreliance on any single approach, land and energy impacts are reduced and redistributed. A diversified CDR portfolio thus exhibits lower negative side-effects, but still poses challenges related to environmental impacts, logistics or accountability. We also investigate a CDR portfolio designed to support more scalable and sustainable climate mitigation strategies, and identify trade-offs between reduced economic benefits and lower environmental impacts. Rather than a one-size-fits-all scaling down, the CDR portfolio undergoes strategic realignment, with regional customization based on techno-economic factors and bio-geophysical characteristics. Moreover, we highlight the importance of nature-based removals, especially in Brazil, Latin America, and Africa, where potentials for avoided deforestation are the greatest, emphasizing their substantial benefits, not only for carbon sequestration, but also for preserving planetary well-being and human health. Finally, this study reveals that incentivizing timely and large-scale CDR deployment by policy and financial incentives could reduce the risk of deterring climate change mitigation, notably by minimizing carbon prices.
