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  • Graeme Warnell

Does E10 Fuel Increase the Risk of Polluting our Environment?

Ethanol is an alcohol fuel that's distilled from plant materials, such as corn and sugar. Alcohol fuels have been around for years, typically mixed with gasoline. Today Ethanol represents about 10% volume of fuel you put into your car (E10), but cars can run on up to 85% (E85)

The introduction of ethanol to standard petroleum has been hailed as a great step forwards in reducing the toxic exhaust emissions related to the combustion engine.

Global Ethanol production has now reached over 25 billion gallons per annum.

As the focus on climate change increases ethanol will feature more prominently.

But what about the impacts of ethanol that are not communicated so favourably?

Ethanol produces less energy so every time the ethanol content in fuel increases you will need to fill your car up more frequently.

In terms of preventing ethanol-based fuels escaping from petrol filling stations into the environment we need to understand how E10 behaves. Fuel with added ethanol behaves very differently to the fuels of the past. Like many advancements in science, the development of the infrastructure to deal with the different properties of ethanol blended fuels is lagging.

Ethanol is hydrophilic (attracted to and soluble in water) whereas fuel without ethanol is hydrophobic (repelled by water) and therein lies the key difference.

Ethanol is completely miscible in both gasoline and water at all concentrations. The presence of ethanol, therefore, affects the fate and transport mechanisms of E10 fuel.

With regards to containment and environmental protection, fuel separators are designed to trap fuel spills on the basis that fuel floats - ethanol does not float. Ethanol also has the ability to make the more harmful components of fuel, (the BTEX elements) soluble as well. Therefore, the original separator design and functionality based on the harmful components of fuel floating becomes obsolete.

The water leaving the separator where E10 fuel is used today is now likely to be contaminated, with worrying side effects for the environment

In case of E10 fuel, the soluble components of fuel that include benzene, toluene, ethyl benzene and xylenes (BTEX) will also partially dissolve. Ethanol and the environmentally harmful elements of BTEX can now pass freely through traditional fuel separators into the local drainage system.

Ethanol tends to dissolve completely into the groundwater and move with the groundwater in the direction of groundwater flow and the presence of ethanol can result in mobilizing existing soil contamination.

Ethanol acts as an energy source and stimulates the growth of aerobic and anaerobic microorganisms in groundwater resulting in the growth of bio films on aquifer material

The rapid bio-degradation of ethanol may also lead to a significant accumulation of volatile fatty acids which are potential degradation products of ethanol and that could decrease the pH to levels that inhibit further naturally occurring bioremediation.

The rapid consumption of oxygen by ethanol means the groundwater will become anaerobic quickly – rapid oxygen depletion in rivers and streams will kill fish.

At present the regulatory authorities are monitoring the situation, most water utilities organisations can cope with the 10% ethanol content in fuel that may pass through the fuel separator.

If the ethanol level in fuel increases or the acceptable levels of ethanol content in water discharge are tightened organisations selling or using E blend fuels will have an issue to face.

In addition, we know BTEX components are carcinogenic – do we really want to allow any of them no matter how small the concentration into our water sources if we can prevent this?

So, whilst there might be monitoring of some petrol filling stations on a site-by-site basis where the amount of liberated BTEX elements may be small who is looking at the accumulative effect from the 8400 petrol filling stations and commercial refuelling depots in the UK?

When we look at how fuel separators are maintained there has been little innovation over the past 50 years even before ethanol was introduced.

Luckily today there has been some progress, with the advent of coalescent ethanol filters there is now a physical barrier that can be applied. Unfortunately, although a welcome step in the right direction it is far from perfect.

Firstly, the ethanol filter must be procured and then fitted which required working above a confined space and zone zero hazardous area. This means shutting off an area of the forecourt which can cause issues with traffic management and safety for the installers on site depending on where the fuel separator is located.

Furthermore, every site is different in terms of its usage, fuel throughput, rainfall received and number of accidental releases and spills that may occur in any given time period. This filter performance based on routine replacement may be a little hit and miss in terms of its efficiency. Finally, the removal and exchange of these filters once again involves the tanker on site with its CO2 footprint, the high-risk work and what happens to the old filter surely its contaminated waste that now must be disposed of at an additional cost.

But do not misunderstand me a coalescent filter is far better than nothing at all.

Is there anything else we can do that is proactive as opposed to reactive? The answer is YES. For years the oil industry has been aware of the power of bioremediation using naturally occurring bacteria for the sole purpose of ingesting and degrading oil. The advantage of this is the bacteria breakdown hydrocarbons into water and naturally occurring CO2 in situ, so why do we try and move contaminated waste when we can treat it where it is?

If petrol filling stations dosed the fuel separators with the correct bioremedial product they would create a biomass and start to ingest any hydrocarbons. This means eventually a near equilibrium will be reached where there is balance between hydrocarbon being ingested and fuel entering the separator. It is unlikely the fuel separator would ever be 100% free from hydrocarbon but it would prevent the build-up of hydrocarbons.

Now image those same bacteria swarming all over the coalescent ethanol filter and helping to keep that clean and working at an optimal level with less service interventions required.

Now this is all perfect for the fuel that floats on top of the water but what about all the dissolved elements in the body of the water contained in the fuel separator. Well luckily one UK based company has now augmented bacteria that will actively scavenger the water column for dissolved ethanol to help combat this problem.

This balance of preventative bacterial activity and the physical coalescent filter could be the closest we get to ensuring that ethanol has a minimal impact on the environment in its attempt to pass through the fuel separator taking the BTEX bad actors with it.

If you found this article interesting and would like more information on the approaches to safe fuel separator maintenance discussed, please email the author Graeme Warnell at

By implementing these preventative measures, you could help reduce the pollution of our rivers and oceans, create a safer workplace for your employees, reduce your carbon footprint and put something good back into the environment so why wouldn’t you?

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