On September 19^th, the 5^th Global Grand Challenges Summit (GGCS) entered its second session, focusing on "Engineering the Transition to Carbon Neutrality". The keynotes and panel discussions were chaired by Prof. Nie Zuoren, CAE Member and President of Beijing University of Technology.

Sun Lili, CAE Member, Chairwoman of SEG/SEI Science & Technology Committee, delivered a keynote on "Research on Process Reengineering Technology and Utilization of Multi-energy Coupling in the Petroleum Refining and Petrochemical Industry Under the 'Dual Carbon' Goal". The presentation pointed out that the petroleum refining and petrochemical, as the supporting industry in the national economy, is undertaking the mission given by the times to promote high quality development and reach the goals of carbon neutrality and carbon peaking. How to realize the synergy between economic development and low-carbon development has become a vital subject faced by the industry. To achieve the high quality development of the industry, a key pathway is to study on process reengineering, with full integration of multi-energy to extend the industrial chain, thus to reduce both pollution and carbon in high efficiency. Therefore, the important directions for China's petroleum refining and petrochemical industry going forward are to make breakthrough in series of key processes and engineering technologies, and in the same time, to research and study on critical equipment, to remove the bottleneck in digital engineering twining and intelligent process control, and to speed up the demonstration projects for engineering application, in order to generate green and high-efficient productivity.

Mercedes Maroto-Valer, Director of the UK Industrial Decarbonisation Research and Innovation Centre and Professor at Heriot-Watt University, delivered a keynote on "Delivering Solutions at Pace and Scale for Industrial Decarbonisation". The report emphasized that net zero has been highlighted as the growth opportunity of the 21^st century. The 2020's decade is indeed critical for laying the policy and infrastructure foundations for decarbonisation. In this context, the UK's Industrial Decarbonisation Strategy have set out a framework to achieve decarbonisation targets and capitalising on clean growth opportunities. The UK Industrial Decarbonisation Research and Innovation Centre (IDRIC), which sits under the UKRI Industrial Decarbonisation Challenge (IDC), plays a key role in delivering solutions for industrial decarbonisation. Moving forward, IDRIC will co-create whole-system solutions at pace and scale that are accelerating the green futures of our industries and supporting the development of four low-carbon clusters by 2030 and the first world net-zero cluster by 2040.

Tim Lieuwen, NAE Member & Professor and Executive Director of the Strategic Energy Institute at Georgia Institute of Technology, delivered a keynote on "Net Zero Pathways in the US Energy System". The report delved into the three components of the US energy system: energy sources, energy carriers and storage, and energy users. It addressed how these elements would evolve as the US decarbonizes, discussing current modeling results for the least cost mix of energy sources and carriers. It also explored the relative role of electric power relative to manufactured fuels (e.g., hydrogen or SAF's) and fossil fuels as energy carriers. Finally, it discussed the complex set of stakeholders and considerations that will influence this least cost system.

Caroline Hargrove, RAEng Fellow & CTO at Ceres, delivered a keynote on "Hydrogen Decarbonises the Parts Other Technologies Cannot Reach". The report stressed that the recent global volatility has only served to highlight the urgency for energy security around the world, with governments under increasing pressure to decarbonise their economies and hydrogen now widely acknowledged as an essential part of the route to net zero. Ceres is right at the heart of this energy transition and is busy expediting the delivery of its solid oxide technology - which provides a highly efficient, low-cost and sustainable route to produce green hydrogen - to global partners to support their transition to a cleaner and more sustainable future.

Gavin Towler, NAE Member & Corporate Vice President and Chief Scientist of Sustainable Technologies for Honeywell, delivered a keynote on "Accelerating Sustainability". The report underscored that the grand challenge of climate change creates a need for every industry to think differently and implement new technologies to reduce the generation of greenhouse gas emissions. As a supplier of measurement, automation, digitization, aerospace and chemical processing technologies, Honeywell is working across the transport, buildings and industrial sectors to deploy new technologies that will help its customers advance on their path to net zero.

Mao Xinping, CAE Member & Professor at the University of Science and Technology Beijing, delivered a keynote on "Vision and Technological Path Towards Carbon Neutrality in China's Steel Industry". According to Mao, the escalating global temperatures resulting in climate alteration present a momentous predicament for the sustainable advancement of human civilization. Mitigating this predicament hinges significantly on the reduction of carbon emissions. Following the ratification of the "Paris Agreement", carbon neutrality has garnered unanimous consensus among prominent countries across the world. Steel is an indispensable foundational material in structural engineering; however, its manufacturing process is renowned for its resource and energy-intensive nature. Over the past three decades, China has made significant progresses in the eco-reformation of its steel production sector, marking an approximate 50% reduction in CO2 emissions per metric ton of steel. However, due to its massive production capacity, the total carbon emissions remain high. In light of China's resource endowment, energy structure, and current development status, the Chinese steel industry has delineated a strategic framework comprising six "dual-carbon" technology pathways. These pathways are underpinned by the optimization of resource and energy structures, with a pronounced emphasis on process refinement, the enhancement of energy efficiency, and the pursuit of innovative technological paradigms, and supported by green and low-carbon products and cross-industry collaboration. The ultimate objective is to achieve carbon peaking by 2030, and carbon neutrality by 2060.

During the panel discussions, the six speakers, joined by Dr. William Orbell from Tsinghua University's School of Environment, representing UK young scholars, actively interacted with both online and offline participants. They engaged in fruitful discussions, sharing their thoughts and insights on the second topic of carbon neutrality, bringing forth innovative ideas and fresh perspectives, and setting a new pinnacle of scholarly exchange at this summit. On the evenings of September 20^th, Members and Fellows from three countries would continue their discussions on the topic of and "Engineering Approaches to Digital Economy". In the meantime, the CAE, NAE, and RAEng would release the Joint Statement on the Global Grand Challenges Summits.