Ensuring the Climate and Environmental Integrity of Alternative Fuels

Public and private investments in alternative fuelsmolecular energy carriers with potentially lower net greenhouse gas emissions than conventional fossil fuelsare rapidly expanding due to their perceived decarbonization potential. However, alternative fuels like hydrogen, ammonia, and methanol are not inherently “good” simply because they can be produced with low-carbon methods. Their climate and environmental impacts vary widely depending on how they are produced, handled, and usedfactors that most assessments fail to fully account for. This can result in poorly informed decision-making, with overestimated benefits of deployment choices. In this Perspective, we highlight potential environmental impacts from alternative fuel value chains and provide an actionable guide for their responsible deployment. Specifically, we provide a brief overview of alternative fuel attributes, assess climate and air quality implications across production, handling, and use, and discuss technological, political-economic, social, and other environmental considerations for responsible deployment. We recommend improvements to alternative fuel assessments and suggest safeguards to maximize their climate and environmental integrity, including best-in-class practices and enabling policies. Given the urgency of achieving global climate goals, it is critical to ensure that scaling up of alternative fuels adheres to sustainable practices from the outset.

公众与私人对替代燃料（alternative fuels）的投资正快速扩张——这类燃料是净温室气体排放低于传统化石燃料的分子能源载体（molecular energy carriers）——其扩张的核心驱动力是被广泛认可的脱碳潜力。然而，诸如氢（hydrogen）、氨（ammonia）、甲醇（methanol）这类替代燃料，并非仅因可通过低碳方式生产就天然具备环保性。它们的气候与环境影响差异极大，取决于生产、储运及使用的全流程——而多数评估工作未能充分涵盖这些因素，这可能导致决策依据不足，使得部署方案的预期收益被高估。在本篇视角综述中，我们着重阐明了替代燃料价值链（alternative fuel value chains）的潜在环境影响，并为其负责任的规模化部署提供了可操作指南。具体而言，我们首先简要概述了替代燃料的属性特征，评估了其在生产、储运及使用全流程中的气候与空气质量影响，并围绕负责任部署所需考量的技术、政治经济、社会及其他环境因素展开讨论。我们建议优化替代燃料的评估体系，并提出保障措施以最大化其气候与环境效益，包括推广行业最优实践（best-in-class practices）及完善扶持性政策（enabling policies）。鉴于实现全球气候目标的紧迫性，从起步阶段就确保替代燃料的规模化发展遵循可持续实践，至关重要。