Introduction to Maritime Decarbonisation

Siddharth Kaul

9 years: Renewable & Low Carbon Fuels

In this video, Siddharth explores the challenge of decarbonising the global shipping industry. He breaks down why shipping is considered a “hard-to-abate” sector, examines the leading low- and zero-carbon fuel options like ammonia, methanol, and hydrogen and highlights the key technological and economic barriers to adoption. He also looks at the role of international regulations and incentives in accelerating change, offering a clear and engaging overview of one of transport’s biggest sustainability hurdles.

Shipping Sector

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Introduction to Maritime Decarbonisation

9 mins 44 secs

Key learning objectives:

Understand shipping’s impact on global emissions and why it’s hard to decarbonise
Outline main alternative fuels and energy efficiency solutions for cleaner shipping
Identify key challenges in adopting green fuels and new technologies
Understand the role of regulations and incentives in driving shipping decarbonisation

Overview:

The shipping sector transports around 90% of global goods and, while it is the most carbon-efficient freight mode by distance, it remains a significant emitter due to its reliance on fossil fuels. Decarbonising the industry is challenging, with efforts focused on alternative fuels such as ammonia, methanol, methane, hydrogen and biofuels each facing issues around cost, scalability and infrastructure. Regulatory targets, carbon taxes and energy efficiency measures are playing a key role, but substantial barriers remain in making these low-carbon solutions viable at scale.

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Summary

Why does the shipping sector matter in the climate conversation?

Shipping is essential to global trade, with around 90% of goods transported by sea. While most people won’t ever step on a cargo ship, almost everyone relies on them. The sector is also a major contributor to climate change. Maritime transport accounts for 11% of direct transport emissions globally and uses highly polluting fossil fuels such as heavy fuel oil. Despite being the most carbon-efficient mode of freight transport per ton-km, shipping’s scale means its emissions remain significant.

What makes decarbonising shipping particularly difficult?

Shipping is considered a “hard-to-abate” sector because of high decarbonisation costs and technological challenges. Unlike road vehicles, which are increasingly electrified, ships are harder to power using renewable energy. The fuels currently used—like VLSFO and HFO produce substantial amounts of CO₂, methane and nitrous oxide. Transitioning away from these involves complex and costly solutions that often lack commercial maturity.

What are the main fuel-based solutions available?

There are three main routes for low- and zero-carbon fuels in shipping:

Green or e-fuels produced using renewable electricity and sustainable feedstocks
Blue fuels made using fossil fuels alongside carbon capture and storage
Lower-carbon alternatives to conventional fuels

Some of the key fuel options include:

Ammonia – Zero CO₂ emissions but highly toxic and must be sourced sustainably
Methanol – Well-tested and versatile, with green (e-methanol) and bio-based variants
Methane – Used as LNG but poses methane leakage risks unless sourced as e- or bio-methane
Hydrogen – Difficult to store and transport for ships, though a potential long-term solution
Bio-oils and e-diesel – Can be used in existing engines but face feedstock and cost constraints

What challenges are limiting the shift to cleaner shipping?

Many alternative fuels are still early in their development or are not economically viable. For instance, ships powered by ammonia or hydrogen do not yet exist at a commercial scale. Fuels like e-methanol or e-diesel are expensive and not widely available. Additionally, biomass-based fuels are in high demand from other sectors like aviation and HGVs, driving up competition and prices. Projects that rely on renewable electricity must also avoid “leakage,” where clean power use in fuel production displaces clean energy from the grid.

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Siddharth Kaul

Siddharth Kaul is the lead carbon project developer for Alcom Carbon Markets, a renewable energy and sustainability company. With two years of experience, Siddharth focuses on life-cycle assessment calculations for biochar, carbon accounting, methodological developments, and general project management. He holds a bachelor's in business and economics from Singapore and an MSc in economics from LSE in London. He previously worked for an oil and gas consultancy, focusing on LNG demand and supply dynamics in Asia.

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