A spatially explicit data-driven approach to calculating commodity-specific shipping emissions per vessel

Ocean-going ships carry approximately 80% of the world’s traded goods by volume – and shipped cargo trade is growing at about 10 billion tonnes per year. By 2012, average annual greenhouse gas emissions from maritime shipping were estimated at around 1 billion tonnes of CO₂ or around 3% of man-made emissions. If the sector is not cleaned up, this share could rise to 20% of total emissions by 2050.

Despite its importance to the world economy and global emissions, the maritime shipping sector was largely neglected in the 1997 Kyoto Protocol and have been overlooked in climate mitigation discussions since.

A lack of reliable emissions data and the difficulty of attributing responsibility for international shipping emissions to the countries, companies and commodities concerned have been key barriers to bringing maritime shipping into global climate mitigation debate and strategies. There is also a perception that too much focus on shipping emissions could affect negatively affect global trade.

This paper presents a new method for accurately calculating and attributing emissions from maritime shipping, by linking per-vessel cargo composition from shipping manifests, with per-vessel location and movement data from the Automatic Identification System (AIS). The AIS tracks the journeys of vessels, as well as operational detail such as speed, movement and draft that can all affect fuel consumption. Combining these two data sets with the operational specifications of each vessel, it is possible to estimate emissions accurately, at the level of individual commodities and vessels, and produce bottom-up aggregated emissions calculations for trading companies and countries of export and import.

This paper demonstrates the new approach with the case of all Brazilian exports in 2014. Maritime shipping of these goods was responsible for 25.99 million tonnes of CO₂, representing an additional 5% on the total CO₂ emissions for Brazil reported by the World Bank (which excluded international shipping and aviation). The study also highlights those commodities and trading routes accounting for the largest shares of these emissions (e.g. iron ores and soybeans), and those that are most important to Brazil’s economy.

Finally, the paper discusses the implications of scaling up this methodology for global GHG abatement efforts and demand-side footprint calculations, as well as to improve accountability mechanisms for the maritime sector as a whole.