GeoLog

carbon emissions

GeoSciences Column: The dirty business of shipping goods by sea

“Above the foggy strip, this white arch was shining, covering one third of the visible sky in the direction of the ship's bow,” he explains. “It was a so-called white, or fog rainbow, which appears on the fog droplets, which are much smaller then rain droplets and cause different optic effects, which is a reason of its white colour.”

Shipping goods across the oceans is cost-effective and super-efficient; that’s why over 80% of world trade is carried by sea (according to the International Maritime Organisation). But the shipping industry also contributes significant amounts of air pollutants to marine and coastal environments.

A new study, published in the EGU’s open access journal Earth System Dynamics, reports on concentrations of sulphur, nitrogen, and particulate matter (PM), from 2011 to 2013, in the Baltic and North Seas – one of the busiest shipping routes in the world. The study aims to provide policy-makers with better knowledge about how shipping impacts local environments. The end-goal being better industry regulations and technology to make shipping more sustainable in the long-term.

The reality of shipping goods by sea

In the past two decades reduction pledges, like the Paris Climate Accord, and strict regulation have driven down air pollutants from land-based emissions across Europe, but greenhouse-gas emissions from the shipping industry are not subject to as strict international protocols.

And that’s a problem.

It is estimated that there are about half a million ships in operation at present, which together produce almost one billion tonnes of carbon dioxide each year (that’s more than Germany emits in the same period!). Over the past 20 years, emissions of pollutants from shipping in the Baltic Sea and North Sea have increased.

Worryingly, economic growth in the region means shipping is only set to increase in the future. In fact, the European Commission predicts that shipping emissions will increase between 50% and 250% by 2050.

Why should you care?

While cruising the high seas, ships emit a dangerous cocktail of pollutants. When burnt, their fuels emit sulphur dioxide and as ship engines operate under high pressure and temperature, they also release nitrogen oxides. Combined, they are also the source of particulate matter of varying sizes, made up of a mixture of sulphate (SO4), soot, metals and other compounds.

The authors of the Earth System Dynamics paper, led by Björn Clareman of the Department of Earth Sciences at Uppsala University, found that international shipping in the Baltic Sea and the North Sea was responsible for up to 80% of near-surface concentrations of nitric oxide, nitrogen dioxide and sulphur dioxide in 2013.

Total emissions of SOx and deposition of OXS (oxidized sulphur) from international shipping in the Baltic Sea and North Sea in 2011. From B.Claremar et al., 2017.

In addition, the team’s simulations show that PM from shipping was distributed over large areas at sea and over land, where many people will be exposed to their harmful effects. The highest concentrations are found along busy shipping lanes and big ports. In total, shipping was responsible for 20% of small sized PM (known as PM2.5) and 13% of larger particles (PM10) during the studied period.

These pollutants have harmful effects on human health: It is thought that living close to the main shipping lanes in the Baltic Sea can shorten life expectancy by 0.1 to 0.2 years. Sulphur oxides in particular, cause irritation of the respiratory system, lungs and eyes; while a 2007 study estimated that PM emissions related to the shipping industry cause 60,000 deaths annually across the globe.

Environmentally, the effects of shipping pollution are concerning too. Deposition of nitrate and sulphate causes the acidification of soils and waters. The brackish waters of the Baltic Sea make them highly susceptible to acidification, threatening diverse and precious marine ecosystems.

The current problem

Legislating (and then monitoring and enforcing) to limit the negative impact of shipping emissions is tricky given the cross-border nature of the industry. For instance, currently, there is no international regulation for the emission of PM. However, the International Maritime Organisation’s (as well as others; see Claremar, B., et al., 2017 for details of all regulations) does impose limits on sulphur and nitrogen emissions from ships (in some parts of the world).

Low-sulphur fuels and switching to natural gas are an effective way to control emissions. However, operators can also choose to fit their vessels with an exhaust gas treatment plant, or scrubber, which uses sea water to remove sulphur oxides – the by-products of high-sulphur fuels. So called open-loop scrubbers release the dirty exhaust water back into the ocean once the tank is cleaned. The practice is known to increase ocean acidification globally, but particularly along shipping lanes.

As of 2021, the transport of goods via the North and Baltic Seas will be subject to the control of nitrogen and sulphur emissions, which could decrease nitrogen oxide emissions by up to 80%. However, the study highlights that the continued use of scrubber technology will significantly offset the benefits of the new legislation. If cleaner alternatives are not implemented, total deposition of these harmful particles may reach similar levels to those measured during the 1970s to 1990s, when shipping emissions were largely unregulated.

By Laura Roberts Artal, EGU Communications Officer

 

Those who have an interest in this subject might want to contribute an EU Public consultation on the revision of the policy on monitoring, reporting and verification of CO2 emissions from maritime transport. The International Maritime Organisation (IMO) adopted the legal framework for the global data collection system (IMO DCS) in July 2017. This Consultation is now reviewing the situation and would like input on things such as the monitoring of ships’ fuel consumption, transparency of emission data and the administrative burden of the new system. While the Consultation is not specifically aimed toward scientists, it may interest EGU researchers who are working in the marine, climate and atmospheric sciences sectors.

 

Refences and resources

Claremar, B., Haglund, K., and Rutgersson, A.: Ship emissions and the use of current air cleaning technology: contributions to air pollution and acidification in the Baltic Sea, Earth Syst. Dynam., 8, 901-919, https://doi.org/10.5194/esd-8-901-2017, 2017.

Lower emissions on the high seas. Nature, 551, 5–6, https://doi:10.1038/551005b, 2017

Corbett, J. J., Winebrake, J. J., Green, E. H., Kasibhatla, P.,Eyring, V., and Lauer, A.: Mortality from ship emissions: a global assessment, Environ. Sci. Technol., 41, 8512–8518, 2007.

Dashuan, T., and Shuli, N.: A global analysis of soil acidification caused by nitrogen addition, Environ. Res. Lett., 10, 024019, https://doi:10.1088/1748-9326/10/2/024019, 2015

What is Ocean Acidification? Ocean Facts by NOAA

Reducing emissions from the shipping sector, Climate Action by the European Commission

New study of natural CO2 reservoirs: Carbon dioxide emissions can be safely buried underground for climate change mitigation

New study of natural CO2 reservoirs: Carbon dioxide emissions can be safely buried underground for climate change mitigation

New research shows that natural accumulations of carbon dioxide (CO2) that have been trapped underground for around 100,000 years have not significantly corroded the rocks above, suggesting that storing CO2 in reservoirs deep underground is much safer and more predictable over long periods of time than previously thought, explains Suzanne Hangx a postdoctoral researcher at the University of Utrecht.

The findings, published today in the journal Nature Communications, demonstrate the viability of a process called carbon capture and storage (CCS) as a solution to reducing carbon emissions from coal and gas-fired power stations, say researchers.

About 80% of the global carbon emissions emitted by the energy sector come from the burning of fossil fuels, which releases large volumes of CO2 into the atmosphere, contributing to climate change. With the growing global energy demand, fossil fuels are likely to continue to remain part of the energy mix. To mitigate CO2 emissions, one possible solution is to capture the carbon dioxide produced at power stations, compress it, and pump it into reservoirs in the rock more than a kilometer underground. This process is called carbon capture and storage (CCS). The CO2 must remain buried for at least 10,000 years to help alleviate the impacts of climate change.

The key component in the safety of geological storage of CO2 is an impermeable rock barrier (the ‘lid’ or caprock) over the porous rock layer (the ‘container’ or reservoir) in which the CO2 is stored in the pores – see Figure X. Although the CO2 will be injected as a dense fluid, it is still less dense than the brines originally filling the pores in the reservoir sandstones, and will rise until trapped by the relatively impermeable caprocks. One of the main concerns is that the CO2 will then slowly dissolve in the reservoir pore water, forming a slightly acidic, carbonated solution, which can only enter the caprock by diffusion through the pore water, a very slow process.

Some earlier studies, using computer simulations and laboratory experiments, have suggested that caprocks might be progressively corroded as these acidic, carbonated solutions diffuse upwards, creating weaker and more permeable layers of rock several meters thick and, in turn, jeopardizing the secure retention of the CO2.  Therefore, for the safe implementation of carbon capture and storage, it is important to accurately determine how long the CO2 pumped underground will remain securely buried. This has important implications for regulating, maintaining, and insuring future CO2 storage sites.

Schematic diagram of a storage site showing the injection of CO2 (in yellow) at a depth of more than one kilometer into a layer of porous rock (the ‘container’ or reservoir), and kept from moving upwards by a sealing layer (the ‘lid’ or caprock). Via Global CCS Institute

Schematic diagram of a storage site showing the injection of CO2 (in yellow) at a depth of more than one kilometer into a layer of porous rock (the ‘container’ or reservoir), and kept from moving upwards by a sealing layer (the ‘lid’ or caprock). Via Global CCS Institute

To understand what will happen in complex, natural systems, on much longer time-scales than can be achieved in a laboratory, a team of international researchers and industry experts traveled to the Colorado Plateau in the USA, where large natural pockets of CO2 have been safely buried underground in sedimentary rocks for over 100,000 years. The team drilled deep below the surface into one of the natural CO2 reservoirs in a drilling project sponsored by Shell, to recover samples of these rock layers and the fluids confined in the rock pores.

The team studied the corrosion of the rock by the acidic carbonated water, and how this has affected the ability of the caprock to act as an effective trap over long periods of time (thousands to millions of years). Their analysis studied the mineralogy and geochemistry of the caprock and included bombarding samples of the rock with neutrons at a facility in Germany to better understand any changes that may have occurred in the pore structure and permeability of the caprock.

They found that the CO2 had very little impact on corrosion of the caprock, with corrosion limited to a layer only 7cm thick. This is considerably less than the amount of corrosion predicted in some earlier studies, which suggested that this layer might be many metres thick. The researchers also used computer simulations, calibrated with data collected from the rock samples, to show that this layer took at least 100,000 years to form, an age consistent with how long the site is known to have contained CO2. The research demonstrates that the natural resistance of the caprock minerals to the acidic carbonated waters makes burying CO2 underground a far more predictable and secure process than previously estimated. With careful evaluation, burying carbon dioxide underground will prove safer than emitting CO2 directly to the atmosphere.

By Suzanne Hangx, Post Doctoral Researcher at the University of Utrecht

 

Reference:
Kampman, N.; Busch, A.; Bertier, P.; Snippe, J.; Hangx, S.; Pipich, V.; Di, Z.; Rother, G.; Harrington, J. F.; Evans, J. P.; Maskell, A.; Chapman, H. J.; Bickle, M. J., Observational evidence confirms modelling of the long-term integrity of CO2-reservoir caprocks. Nat Commun 2016, 7.

The research was conducted by an international consortium led by Cambridge University together with universities in Aachen (Germany) and Utrecht (Netherlands), the Jülich Centre for Neutron Science (Germany), Oak Ridge National Laboratory (USA), the British Geological Survey (UK) and Shell Global Solutions International (Netherlands). The Cambridge research into the CO2 reservoirs in Utah was funded by the Natural Environment Research Council (CRIUS consortium of Cambridge, Manchester and Leeds universities and the British Geological Survey) and the UK Department of Energy and Climate Change.