Carbon dioxide removal (CDR) is necessary for reaching net zero emissions, with studies showing potential deployment at multi-GtCO2 scale by 2050. However, excessive reliance on future CDR entails serious risks, including delayed emissions cuts, lock-in of fossil infrastructure, and threats to sustainability from increased resource competition. This study highlights an alternative pathway─prioritizing near-term non-CDR mitigation and minimizing CDR dependence. We impose a 1 GtCO2 limit on global novel CDR deployment by 2050, forcing aggressive early emissions reductions compared to 8-22 GtCO2 in higher CDR scenarios. Our results reveal that this low CDR pathway significantly decreases fossil fuel use, greenhouse gas (GHG) emissions, and air pollutants compared to higher CDR pathways. Driving rapid energy transitions eases pressures on land (including food cropland), water, and fertilizer resources required for energy and negative emissions. However, these sustainability gains come with higher mitigation costs from greater near-term low/zero-carbon technology deployment for decarbonization. Overall, this work provides strong evidence for maximizing non-CDR strategies such as renewables, electrification, carbon neutral/negative fuels, and efficiency now rather than betting on uncertain future CDR scaling. Ambitious near-term mitigation in this decade is essential to prevent lock-in and offer the best chance of successful deep decarbonization. Our constrained CDR scenario offers a robust pathway to achieving net zero emissions with limited sustainability impacts.

The development of clean energy and financial sectors have been highlighted as critical factors in tackling climate change and achieving net zero emissions goals. Hence, using a dataset for the top 20 emitter countries from 1990 to 2019, this study examines whether clean energy consumption, financial development, human capital, population, and economic growth are connected with environmental quality through a reduction in carbon emissions. The long-run estimates show that renewable energy utilization, financial development, and human capital are significant in reducing CO2 emissions in the quest for net zero emissions. Contrarily, economic growth and population have a increases CO2 emissions. The results of the causality test show a two-way causality between renewable energy use, financial development, economic growth, population, and CO2 emissions. Moreover, one incidence of unidirectional causality is observed from CO2 emissions to human capital. Based on the findings, policy implications are suggested.

Energy security concerns require novel greener and more sustainable processes, and Paris Agreement goals have put in motion several measures aligned with the 2050 roadmap strategies and net zero emission goals. Renewable energies are a promising alternative to existing infrastructures, with solar energy one of the most appealing due to its use of the overabundant natural source of energy. Photocatalysis as a simple heterogeneous surface catalytic reaction is well placed to enter the realm of scaling up processes for wide scale implementation. Inspired by natural photosynthesis, artificial water splitting\'s beauty lies in its simplicity, requiring only light, a catalyst, and water. The bottlenecks to producing a high volume of hydrogen  are several: Reactors with efficient photonic/mass/heat profiles, multifunctional efficient solar-driven catalysts, and proliferation of pilot devices. Three case studies, developed in Japan, Spain, and France are showcased to emphasize efforts on a pilot and large-scale examples. In order for solar-assisted photocatalytic H2 to mature as a solution, the aforementioned bottlenecks must be overcome for the field to advance its technology readiness level, assess the capital expenditure, and enter the market.

Biochar, derived from unused biomass, is widely considered for its potential to deal with climate change problems. Global interest in biochar is attributed to its ability to sequester carbon in soil and to remediate aquatic environment from water pollution. As soil conditioner and/or adsorbent, biochar offers opportunity through a circular economy (CE) paradigm. While energy transition continues, progress toward low-emissions materials accelerates their advance towards net-zero emissions. However, none of existing works addresses CE-based biochar management to achieve carbon neutrality. To reflect its novelty, this work provides a critical overview of challenges and opportunities for biochar to promote CE and carbon neutrality. This article also offers seminal perspectives about strengthening biomass management through CE and resource recovery paradigms, while exploring how the unused biomass can promote net zero emissions in its applications. By consolidating scattered knowledge in the body of literature into one place, this work uncovers new research directions to close the loops by implementing the circularity of biomass resources in various fields. It is conclusive from a literature survey of 113 articles (2003-2023) that biomass conversion into biochar can promote net zero emissions and CE in the framework of the UN Sustainable Development Goals (SDGs). Depending on their physico-chemical properties, biochar can become a suitable feedstock for CE. Biochar application as soil enrichment offsets 12% of CO2 emissions by land use annually. Adding biochar to soil can improve its health and agricultural productivity, while minimizing about 1/8 of CO2 emissions. Biochar can also sequester CO2 in the long-term and prevent the release of carbon back into the atmosphere after its decomposition. This practice could sequester 2.5 gigatons (Gt) of CO2 annually. With the global biochar market reaching USD 368.85 million by 2028, this work facilitates biochar with its versatile characteristics to promote carbon neutrality and CE applications.

Excessive carbon dioxide (CO2) emissions into the atmosphere have become a dire threat to the human race and environmental sustainability. The ultimate goal of net zero emissions requires combined efforts on CO2 sequestration (natural sinks, biomass fixation, engineered approaches) and reduction in CO2 emissions while delivering economic growth (CO2 valorization for a circular carbon bioeconomy, CCE). We discuss microalgae-based CO2 biosequestration, including flue gas cultivation, biotechnological approaches for enhanced CO2 biosequestration, technological innovations for microalgal cultivation, and CO2 valorization/biofuel productions. We highlight challenges to current practices and future perspectives with the goal of contributing to environmental sustainability, net zero emissions, and the CCE.