探索绿色航运之路：一款用于估算绿色航运走廊开发成本的开源工具

《Fuel》：Navigating green Seas: An open-source tool for costing the development of green shipping corridors

1.中文摘要： 该研究开发了整合 techno-economic 成本与 environmental impact 的开源模型，评估了氨、甲醇及甲醇- Marine Gas Oil 混合燃料在主要全球航运走廊（集装箱船、干散货船、化学品船）的脱碳潜力与经济性。结果表明，短途高流量航线（如东亚-东南亚）的脱碳成本较低，甲醇燃料的边际脱碳成本为 350 美元/吨 CO2-eq，氨为 590 美元/吨 CO2-eq；长期看，氨的竞争力可能增强。甲醇- MGO 混合燃料虽减排潜力有限（2%-10%），但可依托现有基础设施过渡。模型显示，不同航线因距离、货物类型和港口成本差异显著，需针对性策略。

　　
The maritime sector contributes approximately 2% of global energy-related CO? emissions, with shipping responsible for around 706 million tonnes of CO? per year. Decarbonizing this sector is critical for achieving international climate goals, such as the IMO’s 70% CO? reduction by 2050. This study focuses on evaluating the techno-economic and environmental implications of adopting low-carbon fuels—ammonia, methanol, and methanol blends—alongside conventional fuels like marine diesel oil (MDO), heavy fuel oil (HFO), and marine gas oil (MGO). The analysis employs an open-source model to integrate costs and emissions across major global trade routes, providing actionable insights for policymakers and industry stakeholders.

### Key Findings and Analysis

#### 1. **Decarbonization Pathways and Fuel Comparisons**
- **Ammonia (NH?):** Produced via renewable hydrogen and carbon capture (blue ammonia) or fossil fuels with CCS (green ammonia). Combustion efficiency is moderate (31–39% for ammonia engines), leading to higher fuel consumption and costs compared to methanol. However, ammonia’s direct combustion pathway and lower NO? emissions (after scrubbing) make it viable for long-haul routes with supportive policies.
- **Methanol (MeOH):** Produced from biomass or renewable hydrogen with CCS. Combustion efficiency is higher (33–43%) than ammonia, reducing fuel needs and costs. Methanol blends with MGO (up to 20% v/v) offer a transitional pathway with minimal infrastructure changes, leveraging existing diesel engines with minor modifications. Blends reduce CO? emissions by 2–10% compared to MGO, with abatement costs of $240–350/tonne CO?-eq (20-year GWP) and $330–490/tonne CO?-eq (100-year GWP).
- **Methanol Blends:** While blends reduce CO? emissions, they still require significant additive costs (e.g., 1-dodecanol) and face challenges in scalability. The analysis shows that 20% methanol blends reduce CO? emissions by 10% but increase shipping costs by 7–15% compared to MGO, depending on route length and vessel type.

#### 2. **Cost Implications**
- **Fuel Costs:** Ammonia incurs the highest fuel costs due to its low energy density, followed by methanol. Methanol blends are cost-competitive with conventional fuels, as only a small fraction of the blend involves expensive methanol.
- **Capital Costs:** Ammonia requires significant investments in fuel storage (due to cryogenic needs) and engine modifications. Methanol blends avoid these costs by using existing infrastructure. For example, ammonia bunkering systems can add up to $50,000 per TEU in capital expenses, while methanol blends require minimal changes.
- **Operating Costs:** Methanol’s higher energy density reduces annual fuel consumption by 5–10% compared to ammonia, lowering operating expenses. However, ammonia’s lower fuel energy density necessitates larger storage capacities, increasing capital costs.

#### 3. **Route-Specific Analysis**
- **Short, High-Volume Routes (e.g., Intra-Asia):** These corridors, dominated by bulk carriers and tankers, face lower cost premiums when transitioning to methanol or ammonia. Bulk carriers on routes like Australia–China (iron ore) see abatement costs as low as $80/tonne CO?-eq, making them early adopters.
- **Long-Haul Routes (e.g., Far East–Europe):** Container ships on these routes experience higher cost premiums (up to 84% for ammonia) due to longer distances, higher fuel consumption, and greater capital investments. For example, a Panamax container ship on this route sees costs rise by 59% when using methanol blends, but this is offset by lower CO? abatement costs compared to ammonia.
- **Chemical Tankers:** Mid-range abatement costs ($130–180/tonne CO?-eq) make them viable under moderate carbon pricing. Methanol blends are particularly attractive here due to existing infrastructure compatibility.

#### 4. **Environmental Trade-Offs**
- **Emissions Reduction:** Both ammonia and methanol achieve >85% CO? reduction when produced from low-carbon sources. Methanol blends reduce CO? by 2–10% compared to MGO, though their environmental benefits are limited to CO? if non-GHG emissions (NO?, SO?) are unaccounted for.
- **Non-CO? Impacts:** Ammonia combustion releases higher NO? and N?O emissions, which require scrubbing and SCR systems to mitigate. Methanol produces fewer NO? emissions and is less toxic, making it safer for human health and marine ecosystems. However, methanol’s production still generates CO? unless derived from carbon-neutral sources.

#### 5. **Economic Viability and Policy Implications**
- **Carbon Pricing:** The study estimates that a carbon price of $200/tonne CO? is needed to make ammonia competitive in most corridors, while methanol blends become viable at $150–250/tonne CO?. Current IMO policies (拟议中价格较低) may not suffice without supplementary measures.
- **Retail Impact:** Cost premiums for shipping (up to 84% for ammonia) translate to minimal retail price increases (0.4–5%) for goods like shoes, refrigerators, or televisions, indicating manageable inflationary effects.
- **Infrastructure Gaps:** Port investments in ammonia handling (leak detection, containment) and methanol blending (additive compatibility) are critical. Major ports like Singapore and Rotterdam are leading in infrastructure development, but smaller hubs face higher costs.

#### 6. **Limitations and Future Directions**
- **Data Gaps:** Limited experimental data on methanol blend combustion emissions (NO?, PM) and their environmental impacts. Current analysis focuses on CO? for blends, which may underestimate overall impacts.
- **Technical Challenges:** Ammonia’s toxicity and cryogenic storage requirements pose safety and operational hurdles. Methanol’s flammability necessitates specialized handling.
- **Scalability:** The study assumes steady fuel supply chains and fixed trade volumes. Real-world adoption will depend on scaling production (e.g., green hydrogen) and regulatory frameworks.

### Conclusion
The maritime sector’s decarbonization is feasible through methanol blends as a transitional step, with ammonia becoming viable under stricter carbon pricing and infrastructure development. Short, high-volume routes (bulk carriers) offer the lowest abatement costs, while long-haul container routes require more policy support. Methanol’s lower toxicity and compatibility with existing engines make it a near-term candidate, especially when blended with conventional fuels. However, long-term success hinges on reducing fuel costs through technological advancements (e.g., higher efficiency engines) and policy measures (e.g., IMO carbon taxes). The open-source tool developed in this study provides a framework for corridor-specific analysis, enabling stakeholders to prioritize routes and fuels based on local conditions.

This work underscores the need for a tiered approach to decarbonization: methanol blends for immediate transitions, ammonia for long-term bulk routes, and supportive policies to bridge the cost gap. Future research should integrate broader environmental metrics and probabilistic cost models to refine decision-making.