The global transition to renewable energy and hydrogen development has brought increasing attention to green ammonia and green methanol which can be produced from green hydrogen. Developing these green chemicals not only promotes their respective industries but also supports the development of hydrogen. A thorough investigation and comparison are essential to determine the priority and specific scenarios for developing energy sources aimed at supporting hydrogen or other sectors. However, previous reviews have typically focused either on specific aspects, such as production or utilization, or have conducted comprehensive analyses limited to only one energy carrier, lacking an integrated comparative approach. This study offers a comprehensive assessment of ammonia and methanol across six dimensions: technology readiness level, energy efficiency, safety, logistical convenience, economic viability, and environmental impact. The analysis shows that each carrier has a distinct development trajectory. Ammonia can be transported through established supply chains and cracked to hydrogen at the point of use, a capability that supports large-scale hydrogen deployment. In contrast, the greater technological maturity of methanol as a fuel positions it for near-term decarbonization of the transport sector rather than immediate integration into hydrogen infrastructure.

The growing threat of global warming makes it urgent to reduce carbon emissions and combat climate change. Achieving carbon neutrality is a key strategy to address these challenges and move towards a sustainable, low-carbon future. Comparing the carbon neutrality strategies of different countries and learning from each other's strengths and collaborating, nations can tackle shared challenges more effectively. This study provides a comparative analysis of carbon neutrality strategies adopted by China, the USA, and Germany, examining their respective legal frameworks, energy transitions, and technological innovations. While Germany has established strong legislative support and regulatory measures to promote renewable energy and reduce fossil fuel dependency, the USA's approach has been marked by policy fluctuations due to political shifts, impacting long-term climate strategies. In contrast, China's rapid progress in renewable energy, including wind power, photovoltaics, and electric vehicles, underscores its unique institutional efficiency and market-driven dynamics. The study explores how each nation’s path to carbon neutrality and global role, emphasizes the necessity of international cooperation. By leveraging their strengths, these countries can collectively shape the global climate agenda, setting the stage for transformative collaboration towards sustainable energy solutions and carbon reduction.

A number of 1/5 scale normal concrete (NC), reinforced concrete (RC), Engineered cementitious composites (ECC) and reinforced ECC (R/ECC) tunnel lining specimens were tested under vertical loading applied at the mid-top of the crown and the mechanical behaviours were analysed. Four lining FE models were established and compared in detail with the test data. Subsequently, numerical analysis of NC lining strengthening methods for different damage levels was performed. The NC linings exhibiting different damage levels were strengthened by either RC arch, ECC arch, R/ECC arch, steel plate and carbon fibre reinforced polymer (CFRP) sheet. The mechanical behaviour of the retrofitted NC linings was analysed, and the strengthening effects were thoroughly evaluated. The results showed that the load-bearing capacity and ductility of NC linings retrofitted by R/ECC arch were better than NC linings strengthened by ECC arch or RC arch. The steel plate and CFRP sheet retrofitted NC linings resulted in lower load-carrying capacities compared with linings strengthened by arches. For the plate strengthening methods, when the damage level of the strengthened NC lining is lower, more pronounced strengthening effects could be attained compared with the highly damaged linings.