UAVs To Monitor Ship Emissions

By Dr Zhi Ning 18 June, 2019

Is it a bird? Is it a plane? No it's a drone to track shipping air pollution. Dr Ning from HKUST expands

Shipping is a cost effective way to move things, but shipping emissions fuel climate change & worsens air quality; of particular concern is sulphur dioxide (SO2) which is hard to regulate
Unmanned aerial vehicle (UAVs) ie drones can ensure ships are in compliance with fuel sulphur regulations by measuring SO2, CO2 & other pollutants when passing through exhaust plumes
Made possible by “low cost sensors”, this approach has been adopted by the HK Environmental Protection Department & been used in Shenzhen ports; it can even determine other emissions

The smooth operation of our ports and waterways are essential for effective economies all over the world. We depend on the goods that come to us and never really think about how they get here and whether there are any possible adverse consequences that come along with our coconut water, Perrier, bananas or new refrigerators. It’s highly likely that each of these made part of their journey to our stores by ship.

Shipping has proven to be a very cost effective way to move things, but ships burn fuels and the emissions from these ships contribute to global climate change due to carbon dioxide (CO2), oxides of nitrogen (NOx), sulphur dioxide (SO2) and particulate matter emissions.

Locally, while on near shore or in port operations these same pollutants can be major contributors to adverse ambient air quality where they may challenge attainment of health based ambient air quality standards, such as Air Quality Health Index (AQHI) in Hong Kong.

Shipping is very cost effective but ships burn fuels & the emissions contribute to climate change & air pollution…


…of particular concern is sulphur dioxide (SO2)

These various impacts have begun to be the focus of local and even international regulatory programs. Of particular concern has been SO2. It predominately originates from the combustion of fuels that contain sulphur. Local governments have been implementing programs to remove sulphur from gasoline, diesel fuels, and many other liquid petroleum fuels that are used to power vehicles, heating and electrical generation facilities within their jurisdictions.

Shipping – an elusive and difficult to control source of air pollution

But ships have remained somewhat elusive sources of SO2 that are difficult to control because they move to and from places all over the world. Some places have rules in effect to reduce emissions which typically are in the form of fuel sulphur content rules—burning fuels with high sulphur content release high SO2 levels while low sulphur fuels emit lesser amounts of SO2. Some may have no regulations or enforcement of fuel quality content.

Ship operators have choices with how to implement sulphur-in fuel-regulations including using differing types of fuels while at sea vs. in local areas where regulations may be stringent. They do this by having more than one fuel on board. However, the cost differences between high quality fuels with low sulphur concentration (around 600 USD per metric ton) and low quality fuels with high sulphur concentration (around 430 USD per metric ton) is substantial. This presents a tempting and complex situation for ship operators. And it also presents a challenge to air quality regulators.

A newly enacted rule for Hong Kong waters specifies that fuel sulphur content must not exceed 0.5%…

A specific example is a newly enacted rule for ships operating in Hong Kong waters. The regulation specifies that fuel sulphur content must not exceed 0.5 percent. This fuel content level also applies to other parts of the Pearl River Delta of China.

The State of California in the USA has enacted an even more stringent 0.1 percent rule for ships operating within 24 miles of its shores. Beginning in 2020 a 0.5 percent fuel “Global Sulphur cap” content will be implemented worldwide under general rules of the International Maritime Organization rules. Conventional petroleum fuels used in ocean going ships may be as high as 3.5 or even 4 percent sulphur content.

…but how do we know whether ships are in compliance with applicable fuel sulphur content?

The primary issue is then, how do we know whether ships are in compliance with applicable fuel sulphur content? One could stop ships in open waters or when docked/at anchorage and take fuel samples. These samples would then be taken to a laboratory for analysis. However, the process would be impractical and could not determine which fuels were actually in use.

One could also instrument ships with real time fuel sulphur or exhaust SO2 analysers. But the operation and reporting of results would be complicated. Aircraft have also been used to collect samples from the plumes of ships underway, but these operations are both costly and involve some degree of risk to both the aircraft operators and the ship itself.

Unmanned aerial vehicle (UAVs) to ensure ships are in compliance with fuel sulphur regulations

A practical alternative means to gather emissions and to determine fuel sulphur content has been developed in Hong Kong by a research team from The Hong Kong University of Science and Technology. It is based on the use of unmanned aerial vehicle (UAV) craft fitted with compact air pollution monitoring sensors that can relay the data to an online cloud platform.

UAVs are fitted with compact air pollution monitoring sensors

These sensors measure SO2, CO2 and other pollutants as the UAV passes through exhaust plumes of stationary ship or ship moving underway. A mathematical script then converts the measured SO2 to fuel sulphur content in real time, which helps in identifying the ships that violates the regulations. It is an offshoot of widely used testing performed to determine emission rates of diesel and gasoline fuelled vehicles operation on roadways.

An underlying operating principal of the method is the ratioing of CO2 to the pollutant of concern. No actual contact with the shipping operator or fuel collection is required. And the method requires only brief actual time in the plume of a ship, with less than two minutes being adequate for ascertainment of sulphur levels. The entire instrument package including power and telemetry of results weighs in at less than 900 grams.

No actual contact with the shipping operator or fuel collection is required…


…this protocol has been adopted by the HK Environmental Protection Department & used in Shenzhen

This protocol has been adopted as an accepted method by the Hong Kong Environmental Protection Department to have control on sulphur content in local waters, and been used in nearby Shenzhen port facilities.

This new approach is made possible by the rapidly growing field of “low cost sensors”. Pollution measurements that once required entire labs to accomplish can be done by systems that can be carried by a UAV or in one’s backpack.

The same method can also determine the NOx or particulate matter (PM) emissions from ship operations

While the current application to UAVs for the measurement of compliance with fuel sulphur content, the same method can readily determine the NOx or particulate matter (PM) emissions from ship operations. Sensor systems can be configured to evaluate volatile organic compound (VOC) or NOx from landfills, waste handling facilities ore industrial process emissions.

The involvement of these sensors in combination with membrane distillations in water purification systems can improve the feasibility of conventional methods. They can replace currently existing stringent chemical and monitoring methods involved in controlled regulatory affairs, and can perform quite well if designed and operated with care.

Expect to see low cost sensors in applications around you.

Further Reading

  • 2018 State Of Ecology & Environment Report Review – It is one year on since the Ministry of Ecology and Environment (MEE) reform, has it impacted China’s water? What has worsened & what has improved? We review the latest 2018 report
  • Beyond The Wall & Into The Watershed – Reducing your own factory’s water use is all well & good but what do you do when your basin is being impacted? Ecolab’s Ting He, Nestlé’s Qi Zhang & AWS’ Zhenzhen Xu provide examples on how to move into the watershed
  • Jiangsu Chemical Park Explosion: Rectify Or Shutdown? – The Jiangsu chemical plant explosion may have been deadly but the environmental & regulatory risks it’s bringing to light may be more worrying. China Water Risk’s Yuanchao Xu unpacks it for us
  • Your Inside Track To Rare Earths – Do China’s threats to weaponise rare earths in the trade war have any teeth? Even if not, a house of cards worth trillions could be at stake – find out why & get the edge now
  • Eco-preneurs To Combat Pollution – What are “eco-preneurs”? The Ministry of Ecology & Environment’s Dr Zhanfeng Dong explains & elaborates on their role as a lynchpin in winning China’s war on pollution
  • Dear Santa, Less Stuff Please – This Christmas China Water Risk’s Dawn McGregor draws attention to the trails of waste left by our gifts, made worse with low-recycling rates & increasing e-commerce orders. She wants less stuff but that doesn’t mean no presents
  • Unwrapping Packaging Water Risks – China’s paper packaging industry discharges wastewater similar to its entire coal industry. Explore the dirty secrets behind paper & plastic packaging with China Water Risk’s Feng Hu. Also, see how shifting consumer attitudes can bring about new innovations
  • Fashion Has The Power To Shape A 2℃ World – If fashion were a country it would have the fourth highest carbon emissions behind the US, China, & India. China Water Risk’s Dawn McGregor & Debra Tan question why the industry is not under the spotlight like coal and call for faster disruptions
  • No Safe Haven For Polluters – As affluent eastern Chinese provinces are cleaning-up, companies are relocating to inland provinces with more lenient regulations. China Water Risk’s Hubert Thieriot explores this pollution haven effect & why it can be a short-sighted strategy

Dr Zhi Ning
Author: Dr Zhi Ning
Dr. Zhi Ning is an Associate Professor in the Division of Environment & Sustainability, The Hong Kong University of Science and Technology, Hong Kong SAR. Dr. Ning’s research interests cover the innovation and development of environmental monitoring technologies with a focus on low-cost sensor algorithm and its application on air quality research. Dr. Ning has active participation in the low-cost sensor related work initiated by USEPA, WHO and WMO, and has led his team to develop the air sensing technologies for use in the first marathon route sensor network, large scale urban mobile sensor network with wide recognition locally and globally. Besides the technology development, Dr. Ning’s research also aims to understand the physical and chemical process of air pollution in complex urban built environment and their impact on the air quality and public health.
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