Forward Thinking and Refined

The spill risk picture evolves as the offshore energy industry transitions from oil and gas to offshore wind and marine renewables. Response to the 'renewable spill risk' must be considered and applied to the applicable oil types. Offshore wind farms, for example, require hydraulic, lubricant and gear oil to operate and control various mechanical components in the turbines and other equipment.   

There are three types of potential pollutants associated with an offshore wind farm:  

• non-persistent hydrocarbons, such as Intermediate Fuel Oil (IFO), Marine Gas Oil (MGO) and diesel from the construction and supply vessels, 
• persistent hydrocarbons, such as lubricating oils and hydraulic oils on the installations themselves, and
• chemicals.   

The source of these pollutants to the marine environment is accidental releases, leaks, vessel collisions and allisions throughout the construction and operational activities. The hydrocarbon and chemical inventories on the construction and supply vessels and offshore wind farm installations, as well as any geographical possibilities, dictate potential spill scenarios as demonstrated below.   

Construction and Decommission Phase Scenario   

Operation Phase Scenario

We welcome any turbine manufacturers to verify this information by contacting us.

In practice, due to mitigations such as training, operating procedures and engineered solutions such as collection tubs, the spill-to-sea risk is low due to the slight chance of release coupled with the inherently small volumes. But does that mean the offshore wind industry shouldn't prepare for it?   

Technological advances mean turbines are getting bigger, meaning they will store larger volumes of hydraulic oil.[1] Hydraulic oil is an essential component of the turbine's hydraulic system, used to optimise the turbine's performance, to perform mechanical tasks, such as adjusting the blade pitch and yaw angle.   

The offshore environment, with its exposure to saltwater and extreme weather conditions, puts more stress on the hydraulic systems. Therefore, the oil used in offshore wind farms must be refined to withstand these conditions, maintain its viscosity and resist degradation from water and other contaminants.  

The oil's refinement could make responding to this oil type offshore challenging. Fixed bottom offshore wind farms are also located in shallow waters, some close to the coast, making shoreline impact from a release a possibility.   

Do regulators and operators adequately address this oil spill risk globally? Whilst the scenarios may have been considered or even better written down in a plan (albeit without volumes), has it ever been challenged or tested? There is room for improvement and an opportunity for learning here.

As there is a renewables-associated oil spill risk and taking into account contingency planning for a worst-case scenario, the industry should further evaluate a response to these scenarios.  

The global offshore oil and gas industry is mature. Spill response preparedness measures, regulations and what the industry considers 'good practice' have evolved over decades of iterative improvement.  

Whilst the basic spill characteristics of most crude oil fields are known, we need to understand more about the effectiveness of conventional oil spill response techniques on new shipping fuels.   

Even less is known about the specifically refined oils used for offshore turbines regarding spill response techniques. Responders also need to consider the variable conditions that can limit the success of response operations. It comes back to utilising experience that the oil and gas industry has refined over decades.   

There have also been many step changes, typically driven by lessons from incidents and exercise insights. We shouldn't waste those watershed moments but map them to the world of renewables.  

We don't have to, and we shouldn't start from scratch, ignoring the gift of hard-earned lessons learned. Not all oil spill response techniques will map directly or effectively. The industry needs a full review to examine the evolving oil spill risk profile.  

Response Toolbox

The oil industry responds to oil spills using an accepted good practice ‘toolbox', summarised by the Tiered Preparedness and Response (TPR) wheel below.

Ultimately, all response options should be considered 'on the table' in a spill scenario. Choosing the most appropriate technique(s) and overall response strategy comes with experience and consultation with stakeholders through a process known as Net Environmental Benefit Analysis or NEBA.   

Oil spill contingency planners for oil and gas operations have used the evolution of modelling the worst-case scenario to improve preparedness. This evolution has led to the advancement of the response toolkit, including the importance of early warning through good surveillance and monitoring to inform response decisions.    

Marine Pollution Contingency Plans for offshore wind farms typically list the following response options, applying the tiered preparedness response model for resources:   

• Natural dispersion and monitoring for persistent and non-persistent oils
• Mechanical recovery for persistent oils
• Assisted natural dispersion for non-persistent oils
• Application of a licensed bioremediation agent (i.e., dispersant) in line with manufacturers guidance with approval from regulators for non-persistent oils
• Boat-based dispersant application for persistent oils and non-persistent oils   

As you can see, there are similar response options to the oil industry, but given the different risk picture, i.e., refined oils and new shipping fuels, are these response options still appropriate? Will they even work?  

Depending on the scenario, aerial dispersant application would not suit refined oil spills from turbines. The aircraft would only arrive after the oil either disperses or sinks. However, for a fuel spill from a large construction vessel with substantial bunkers close to an aerial dispersant capability and if the slick was heading down current of the turbine blades, then it would be pertinent to consider this response option, especially if the slick could impact a sensitive marine wildlife area. 

There is a danger of reinventing good practice for renewables, which is already available and freely accessible, a list featuring a sample of these publications is provided below.

IOGP Publications

IPICEA Good Practice Guides

The oil spill response good practice that already exists (as sampled above) demonstrates the breadth and complexity of spill response. Being prepared, proportionate to the risks and implementing resources to minimise environmental impacts is the foundation of the fundamental principles in the guidance documents.  

The good news is that all of this is entirely transferrable to renewable spill risks; however, one big question we need to explore is, "Can we use dispersants on refined oils?" 

Dispersants help to break up surface oil and reduce the likelihood of oil spreading and affecting a large area of the ocean and coastline. Dispersant redistributes the oil into the water column – it doesn't impact or increase toxicity. This redistribution can reduce the overall environmental impact of the spill and minimise the damage to certain marine biota and coastal ecosystems.  

Essentially dispersants accelerate the natural dispersion process. Lighter products disperse this naturally and rapidly. Achieving the proper Dispersant Oil Ratio or DOR on a light oil product is almost impossible due to the rapid spreading. Therefore, using dispersants on lighter hydrocarbons, like gas oil or biodiesel, is unlikely to be beneficial because they will stay buoyant, spread to a very thin layer, and evaporate.   

Academia and industry need to conduct more research to investigate the effectiveness of dispersants on IFO, MGO, diesel, hydraulic and lubricating oils and any limitations associated with this approach. To justify more research into this, we want to highlight this gap so we can help the decision-makers and regulators with the knowledge to use (or not use) dispersants as part of the NEBA process, supported with accurate data.   

If there is a spill of hydraulic (or lubricant) oil on water, the type of dispersant that we use will depend on the specifics of the spill, such as:  

• Will the dispersant work (its effectiveness)?
• What is the dispersants' approval status?
• Where is the spill location (including distance from shore and water depth)?
• What are the environmental sensitivities near where the spill has occurred?
• What is the type of hydraulic/lubricant oil?
• What is the (potential) size of the spill?   

We must understand the answers to these questions during the planning phase because in a response, the effectiveness window may pass while you work through the decision-making and approval process (if there is one). Using the appropriate type and concentration of dispersant for the spilt product and surrounding environment is essential, which you are best figuring out in 'peace time’.   

Spill Response is Science and Evidence-Based  

Through laboratory and basin testing, research institutes such as SINTEF study the fate and behaviour of different oils when spilt in the marine environment. Researchers often link such weathering characterisation studies to also test the feasibility and effectiveness of other response methods (e.g., different skimmers, the effectiveness of dispersant use, in-situ burning (ISB)) for the specific oil types.  

The studies use specific oils' lab/basin-generated weathering data as input to operative modelling tools, such as the SINTEF Oil Weathering Model and the OSCAR oil spreading and response model. Annual field trials (such as NOFO oil on water trials) have verified these laboratory studies and model predictions. 

For example, SINTEF has tested and characterised hundreds of crude oils and many refined oil products (including IFO, MGO, and diesel), using the generated weathering data for modelling predictions. This research includes specific oil weathering studies (and dispersant effectiveness testing on most of these oil products) on various categories of refined bunker fuel oils in the SINTEF oil database.[2] 

SINTEF has minimal weathering and dispersibility documentation for lubricating and hydraulic oils. These typically represent smaller volumes (e.g., in a vessel spill incident compared to the bunker fuel volume) and have yet to be considered further in the planning phase.  

As the risk is low (in terms of volume (as a contributing factor defining potential severity) and likelihood), I can understand why there has not been the appetite or the budget to test the oils with dispersant in a lab, but should this stop here? For context, the cost of testing (depending on the provider) would be in the region of £2,000. Once data are available in an oil database with supporting modelling software, you can visualise and plan for the impact prediction. 

When scientists and researchers conduct the weathering studies, they "top" the crude to 150^oC to remove the volatiles to simulate the weathered product before doing a dispersant Effectiveness Test. The renewables industry could use the same testing protocols used in oil and gas for refined hydrocarbons to verify if dispersants would be an option.  

In the meantime, due to the low persistence of MGO and diesel and their propensity to spread out (leading to thin slicks), CEDRE and OSRL would not recommend dispersant use on refined hydrocarbons. Indeed, the treatment is possible, but more often than not, it is unnecessary (the pollutant disappears because it evaporates or disperses naturally). It would, however, be interesting to see the results of any dispersant studies on refined oils to corroborate this conclusion.   

So, if dispersant isn’t the right option, what can be done for renewable spill response?   

One response option is mechanical dispersion (aka mechanical agitation). This process helps to accelerate the natural dispersion of light oil in the water column by artificially agitating the water surface, using fire hoses (using a solid water jet) from a vessel or using the propeller of a suitable vessel.  

The addition of energy in this way attempts to replicate the natural dispersing effects seen during high winds or storm conditions. Page 42 of the POSOW Fishermen's Support in Oil Spill Response Manual sets out the operational procedure and protocol of the response technique.  

Through consultation, offshore wind developers could work with fishing communities and response organisations to conduct this technique and ensure the protection of the marine environment.    

A response tool to help remove floating hydrocarbons is at-sea containment and recovery. This technique involves the action of one or more vessels (plus aerial surveillance and communications) pulling inflatable booms through a wind farm. Deploying this could be more challenging to navigate and, therefore, more dangerous than in the open ocean, depending on the drift of the slick and the location of installations. 

Trained vessel crews are essential to ensure safe and effective deployment in feasible weather conditions. Therefore, a combination of response options and keeping dispersant (if it is amenable to the spilt product) in the 'toolkit' should be considered from an environmental point of view and a safety position.

On a positive note, good practice guidance is available with transferrable principles for renewable operators and regulators. The oil and gas industry has trodden this path before, developed the tests, technology and tools to support spill response. The good news is they are entirely transferable to offshore wind, wave and tidal.  

I have used this opportunity to prepare an example Tiered Preparedness and Response (TPR) wheel for the offshore wind industry, below. The dark blue colour arbitrarily represents resources that should be immediately available to an operator to implement that particular response tool. 

Green resources are held in national stockpiles, owned and maintained by government or regional response organisations. 

Light blue resources are international oil spill response organisations, including specialist expertise, equipment and responders. 

At the core of any response is an Incident Management System (IMS) that oversees response requirements and liaison with all stakeholders. 

In Summary

There is a need for more research (and funding) to determine if dispersant is appropriate for use on the types of refined oils used in offshore wind, wave and tidal installations. As the offshore risk profile changes, there is an opportunity to improve the understanding of the effects of dispersant use for refined products. We should close the gap using industry advocacy and engagement to transition responsibly. 

Oil spill response is science and evidence-based. We need to be informed so we can rule in or rule out specific tools and techniques to build the right strategy based on the variables encountered during a response. 

From a global perspective, there is also the unknown factor of regulator policy or guidance for dispersant use in relation to spills caused by offshore wind farms or vessels responding within offshore wind farms. 

If there are no regulations or conventions, it comes down to the company or operator's appetite to implement the right approach. Given the potential benefits and limitations associated with the use of dispersants in refined oil spills, it is essential to carefully consider their use in each specific scenario, applying the NEBA process in consultation with stakeholders. 

Offshore wind is a global energy resource. As a global oil spill response organisation, we feel passionate about helping all operators navigate spill management challenges. We would therefore like to offer the offshore wind industry the following good practice recommendations:  

1. Work with oil research institutes to understand how refined oils used in operations will behave in the marine environment, i.e., a limited study of the main relevant characteristics:  
   1. emulsification formations properties,  
   2. natural dispersion tendency and,  
   3. dispersant enhanced dispersion – i.e., a simple effectiveness screening of relevant dispersants for a limited number of specific oil products and chemicals used in offshore wind farms.
2. Work with dispersant manufacturers to understand if the oils used in operations will be amenable to dispersant and reflect on what to do if they aren't. 
3. Work with spill response specialists to understand risks and appropriate response options. 
4. Consider using more readily biodegradable products that support the development of more responsible, lower-risk alternatives that don't compromise turbine performance. 
5. Work with local fishing communities to assist in the spill response mitigation process.

Good spill response will attract little media coverage (unfortunately!), and achieving a successful outcome stems from investment in spill science and research. 

With improved collaboration between the oil and renewable industries regarding spill response, the renewable version of the TPR wheel may evolve to include techniques that we are yet to research, for the oil products that the industry is still to develop, for the turbines that the renewables industry is still to design!   

1. The volume of hydraulic oil used in an offshore wind turbine can vary depending on the specific turbine design and manufacturer.
2. Traditional HFO bunker fuels (1 and 3.5 % S) e.g.  Residual fuels, e.g.  IFO 30, IFO 60, IFO 80, IFO 180, IFO 380, + VHFO: e.g., IFO 550 (Erika), IFO 650 (Prestige). In total ~25 different HFO’s have been characterized over the years (2015). Different refined distillates (e.g., MGOs, MDOs, ADOs, wide range gas oils etc). Total ~15 distillate products implemented in the SINTEF Oil Database. Characterisation of New generation of Low Sulphur Fuel oils (Residual LSFO), both VLSFO (0.5 S) and ULSFO (0.1%S): About 10 LSFO fuels have been characterised in the laboratory since 2015 and 2022. Starting in 2022 to look into the characterisation of bio-diesel fuels,  e.g. HVOs, FAMEs.