Keep it clean: examining the importance of oil and gas scrubbers

Credit: Mr.1 / Shutterstock

Oil and gas operations rely on a range of industrial processes that sadly generate toxic pollutants. Chemicals such as hydrogen sulfide (H₂S) and volatile organic compounds (VOCs) such as methane are produced during drilling, refining, and processing, and can be harmful to workers and the environment.  

Before these pollutants can be released into the atmosphere through gas streams, scrubbers are used to capture and remove impurities, recover liquids, and protect downstream equipment.  

As an increasing emphasis on environmental compliance, emissions reduction, and enhanced operational efficiency surrounds the oil and gas industry, Offshore Technology’s parent company,  GlobalData, has highlighted that scrubbing is now a key area for technological innovation.  

Scrubbers were originally used to remove carbon dioxide (CO₂) from submarines and were adopted by the hydrocarbons industry in the 1970s to mitigate its impact on air quality. Approximately 15% of total energy-related emissions globally are produced by oil and gas operations, as per the OECD.  

Scrubbers are comprised of inlets where gas flow enters and is slowed down, separation units for gases, liquids, and solids with filters or mesh pads to catch any remaining droplets, and an outlet where the cleaned gas exits the device. It is then either released into the atmosphere or used for further processing.  

Depending on the type of pollution and operational requirements, oil and gas operators have a range of scrubber types to choose from.  

Wet scrubbers are most used in the industry. Particulate matter is removed from the air using liquid, typically water, to neutralise acidic gases and trap solid particles in a contact chamber. They are especially effective for drilling or refining centres in which strong debris is generated.

Wietse Bandstra, marketing manager at scrubber systems manufacturer JOA Air Solutions, explains that “the importance of water as a scrubbing liquid and making sure that most water can be re-used will grow in importance in the future.”

Gas absorption scrubbers also use liquid to take in sulphur and natural compounds from gas streams, while chemical scrubbers deploy alkaline solutions that turn harmful gases into neutral salts. If water availability is limited, dry scrubbers allow the use of reagents such as lime or sodium bicarbonate to chemically react with and filter pollutants.

Across scrubber types, ensuring effectiveness is central. A report by measurement and precision instrument manufacturer Mettler Toledo states that “reduced scrubber efficiency not only carries the risks of pollutants being released to the atmosphere and the corrosion of equipment, [but] a build-up of by-products reduces efficiency further and inevitably leads to expensive maintenance.”

To continually monitor scrubber performance both onshore and offshore, sensors can be fitted to detect changes in temperature or the concentration of chemicals.

This allows for smoother scrubbing in vital processes across the oil and gas value chain, including fluid catalytic cracking units, hydrotreaters, and sulphur recovery units in refineries and on offshore platforms.

For the unique challenges of the offshore environment – limited space, high humidity, and the need for reliable, low-maintenance equipment – scrubbers can have specialised designs and features.  

Offshore scrubbers are often made from stainless steel or titanium to be corrosion-resistant and robust enough to handle harsh marine conditions. They are also compact with multiple separation stages condensed in a single unit for maximum efficiency within space and weight constraints. 

Removed particles and liquids collected at the bottom of scrubbers must also be periodically drained from offshore platforms for waste disposal.  

As the oil and gas industry navigates its energy transition, the issue of scrubber waste and its impact on the environment brings into question whether the bridging technology faces obsolescence or can keep pace with emissions abatement.   

Scrubbers were spotlighted in 2020 when the International Maritime Organisation (IMO) instituted a global sulphur cap (IMO2020), requiring all seagoing vessels to use marine fuels with a maximum sulphur content of 0.5%. 

Following the cap, vessels (including oil tankers) increased scrubber installations to continue using regular fuel instead of costly Very Low Sulphur Fuel Oil (VLSFO).  

According to Sea Intelligence, shipping lines have saved a cumulative $13bn since the implementation of IMO2020 due to the use of scrubbers. 

This demonstrates how hydrocarbon operators can similarly rely on the technology to meet environmental regulations while prioritising cost.  

Scrubbers range anywhere from $1m to $6m to install, with wet scrubbers lasting five to 15 years and dry scrubbers up to 20 years or more if well-maintained. A return on investment in the technology can take anywhere from under a year to several years depending on the price spread between high and low sulphur fuels.  

In turn, this has driven market growth for scrubber-fitted crude-carrying vessels. Shipowners continue to invest in scrubbers over VLSFO, which was priced at $664.50 per metric ton in early 2024.  

Independent research organisation SINTEF finds that from well-to-wake the continued use of HSFO or HFO (heavy fuel oil) with scrubbers is “the most environmentally beneficial means of meeting global greenhouse gas emissions targets.” 

However, using the devices to reduce air emissions has been found to result in the contamination of the sea with scrubbed chemicals. Research shows that marine ecotoxicity damage from scrubber water discharge in the Baltic Sea Area from 2014 to 2022 amounted to €680m ($718m).  

In the short-term, advancing scrubber technology with a focus on life-cycle analysis would represent a practical step towards net zero, given that a rapid wholesale replacement of fossil fuels with renewable energy appears increasingly unlikely. 

A life-cycle analysis of a scrubber for a hydrocarbon company could assess its impact on marine pollution and energy usage, as a typical device uses between 600 and 1500 kilowatts of power per hour, depending on the amount of energy input per unit of gas flow. 

Bandstra points out that scrubbers are a “futureproofing asset, especially when integrated with energy recovery systems. For example, combining heat exchangers and heat pumps with scrubbers can not only reduce emissions but also capture waste heat for reuse in industrial processes. This integration leads to significant energy cost savings and a reduced environmental footprint.” 

Given the popularity of scrubbers, manufacturers are working alongside developing environmental regulations to keep the technology relevant.  

Yara Marine Technologies is one such company working on maturing scrubbers, as chief sales and marketing officer Aleksander Askeland explained in a recent webinar. “We’re looking at reducing energy consumption and cost, how new fuels can be scrubbed, the long-term storage of CO₂, and interconnection with other tech. 

“The end-goal is to eliminate scrubbers in their current form,” he added.  

According to maritime classification society DNV, the main weaknesses to be addressed in scrubber technology are risks of corrosion, flooding or leaks, an incompatibility with the offshore marine environment, and potential sensor failures.  

Digitalization is highlighted by DNV as a viable solution to improve the reliability of scrubber sensors, allowing artificial intelligence (AI) virtual sensors to support physical devices by predicting gas outputs. 

A recent significant scrubber innovation in the oil and gas sector is Eni’s successful grant for an electrochemical cell featuring a removable scrubber. The system can utilise either irreversible or reversible media, including various chemical compounds such as soda lime and amines, to effectively manage CO₂ levels. 

Only with research and development (R&D) investment can scrubbers become a significant enabler for net zero. 

The International Energy Agency (IEA) forecasts that hydrocarbon emissions need to be cut by more than 60% by 2030 from today’s levels and the emissions intensity of global oil and gas operations must near zero by the early 2040s. 

“The field of emission control technology is continually evolving,” said Bandstra. “Investing heavily in R&D ensures scrubber systems not only meet but exceed current environmental standards and we anticipate continued growth and innovation in the market.”