Fueling the circular economy in shipping

You might think of airports and shipping ports as passive infrastructure, merely facilitating the movement of people and goods. In fact, these transportation hubs actively compete to attract business from carriers. In the shipping industry, the most successful ports excel in cargo turnover rates, multi-modal connectivity, automation, digitization and competitive pricing for fuel and other services.

A safe harbor for oily marine waste

Today, shipping companies also expect ports to provide environmental services to help them comply with increasingly stringent regulations. One crucial service is port reception facilities (PRFs), which receive, treat and safely dispose of ship-generated waste. As a key measure to reduce marine pollution, PRFs play a vital role in preventing illegal discharges of bilgewater and sludge, ensuring ships meet their obligations related to international marine pollution laws, referred to as “MARPOL” by the industry.

This is no small matter. Cargo ships typically arrive in port with large volumes of bilge water (a mixture of oil, water and other contaminants), sludge (heavy residues from fuel purification processes) and other waste oil. Roughly 2.5 million metric tons of oily waste are generated each year globally, with the European ports handling more than one million metric tons of those hard to recycle liquids per year.

At the port of Piraeus in Greece, which ranked fifth among major European container ports as of 2024, the Hellenic Environmental Center (HEC) operates a state-of-the-art waste management facility specializing in the treatment of ship-generated petroleum waste. The HEC distinguishes itself in oil sludge management through its circular economy approach, focusing on hydrocarbon recovery and waste-to-fuel conversion. 

GEA separators and decanters turn a problem into a valuable resource

In a two-phase project dating back to 2015, the HEC commissioned PanMarine & Industrial Services Ltd., GEA’s official agent and distributor in Greece, to handle the centrifugal treatment of the emulsions, a key step in the multiphase waste oil treatment process involving hard-to-break bonds between hydrocarbons and water. This included detailed process design, supply of all equipment, supervision of installation, startup and commissioning, as well as technical after-sales support – first for a GEA 3-phase decanter (in 2015) and later for a GEA 2-phase decanter and two OSE 80 separators (in 2018). 

PanMarine’s owner and director, Vangelis Doussis, talks about one of the core challenges involved in oily waste treatment. “The loads delivered to the facilities from the ships contain ever-differing compositions of water, salt, oils and solids. So, there is no standard product,” he says. As Doussis explains, the medium itself is potentially explosive because crude oil contains light fractions – the smaller molecules with lower boiling points used in making benzene or gas for cooking for example – and is toxic because of the presence of hydrogen sulfide. Adding to the challenge, the separation process is difficult because of the very small difference in density between heavy fuel oil and water. “We tackle this using our own experience combined with GEA’s wealth of expertise and top-of-the-line decanters, says Doussis. “Personally, I am very proud to have been part of the team that designed this system and made it work.”

On the GEA side, is Markus Arndt, Product Sales Manager Oil & Gas and Energy. “Treating this petroleum waste requires highly efficient centrifuges, a nitrogen atmosphere to control the risk of explosion and good pretreatment at temperatures of 100 degrees to safely reduce the viscosity,” says Arndt. “At the same time, demulsifiers or polymers need to be used because water and oil have strong bonds. To allow refineries and alternative fuel customers to use the recovered oil, we must comply with maximum permissible values for the water content in the oil.” 

The process begins with decanter centrifuges which separate out most of the solids. In the second step, the oil phase, which still contains residual water and fine solid particles, is passed through a polishing separator. Oil-water separators further refine the process by removing excess water, reducing disposal costs and improving the quality of recovered oil. 

“It is crucial to have a machine that allows for a variable process – and that is one of the most striking features of our decanters used in the joint venture between PanMarine and GEA in Greece,” says Arndt. “These particular decanters are fully equipped plug-and-play skids for easy integration into any system. They are preassembled and pretested in our factory, with capacity ranging from 1000 liters per hour for small productions to 20,000 liters per hour for large-scale treatment. This particular case involved the complete design of a MARPOL facility in close cooperation with PanMarine and HEC.”

What exactly makes GEA centrifuge technology so good? Doussis explains the GEA advantage as follows: “The machine is a highly efficient separating decanter with considerable scope in terms of the capacity.” Arndt adds: "Then there is the fact that the drive systems on these decanters have a very wide control range, in turn producing an equally wide differential speed range, which makes them extremely flexible and ideal for such high product fluctuations.”

From an environmental perspective, the advantages of oil sludge treatment are clear: GEA decanters and self-cleaning separators separate the problematic oil mixtures into water, solids and oils in the most environmentally friendly way possible. “The treatment enables the efficient extraction of raw materials that are in high demand. These are then made available to ship’s operations as separate oils with a high calorific value, either directly by the MARPOL company or a local refinery located downstream – also with the option of selling the oil as fuel oil with a special permit. Recycling oil thus saves resources, especially heavy fuel oil,” says Arndt. “And there is a benefit on the water side as well: The separated aqueous phase can be treated in a downstream water treatment plant in such a way that allows it to be safely discharged into the environment.”

Peace of mind and cost savings for shipping companies

By ensuring maximum oil recovery, these systems reduce the amount of untreated waste disposed of, making PRFs more economically viable for shipping companies. “On the cost side for the shipowner, there is huge savings potential due to the significantly lower delivery costs,” says Doussis, who compares HEC’s price to that the companies would have to pay for safe disposal without treatment. Ultimately, the high efficiency of GEA centrifuge technology is key to keeping fees low – and ocean waters clean. 

“The core mission of a PRF is to prevent illegal dumping and ensure that MARPOL-compliant waste disposal is accessible and economically viable for shipping companies,” says Doussis. “If fees are too high it can push shipping operators toward cheaper but riskier alternatives such as unloading waste in ports with weaker enforcement and improper discharge policies, putting ocean ecosystems at risk.” 

The HEC’s installation in Piraeus was the first in its series of Global Green Ports, a private owned group that consists of a dynamic network of environmental companies in strategic locations, namely Greece, Germany, Gibraltar and Malta. The group aims to expand its environmental protection infrastructure to ports worldwide which are subject to MARPOL regulation.

“We are processing about 20 percent of the EU’s MARPOL oily waste,” states Georgia Reppa, Research & Development Manager at HEC. “This is a tremendous responsibility as well as a remarkable opportunity to foster a cleaner and more circular marine industry. Collaborating with partners like GEA, we ensure the health and safety of both the environment and our team, while also converting this waste into valuable fuel energy sources that can be reintroduced to the market.”