Alternative fuels — making the switch

A genset is a common sight on many construction and industrial projects, working hard to keep equipment, machinery and welfare running. But do you know what fuel is powering the system behind the scenes?

While traditionally the answer would be easy — diesel — alternative fuels are becoming much more popular. Here Barry Hughes, Applications Manager at leading Cat generator rental company Energyst UK & Ireland, shares insight into alternative fuels for temporary gensets.

The environment is a compelling reason to switch from diesel to an alternative fuel. For companies that have made a commitment to become carbon neutral, moving away from diesel is a natural step. But this is not the only reason, businesses may be looking to reduce the impact on the local area by reducing the amount of smoke or smell the genset emits. Alternative fuels also require fewer logistical and operational preparations compared with diesel, as using biodegradable fuels means that operators do not need to make contingencies for spillages.

The Red Diesel Tax reduces the cost of diesel in many applications and has been a challenge for alternative fuels, but it does not offer security for the long term. In line with the UK Government’s net zero by 2050 target, some companies are concerned they will be penalised in the future for diesel use, though there will of course be exemptions.

In London, the Non-Road Mobile Machinery (NRMM) Low Emissions Zone is now stipulating and policing better environmental practices, such as adopting Stage V engines or improved solutions including early, including the approved use of alternative fuels. As other cities follow suit, it will contribute further to the uptake of alternative fuels.

For companies already committed to carbon neutrality, alternative fuels can reduce the requirement to offset at the end of the year, such as by planting trees if they do not achieve their own commitments to the environment, impacting on the business’s operational costs. There are also opportunities to reduce maintenance costs compared with diesel. For this mixture of reasons, we are seeing a huge rise in the number of people looking for alternative fuels.

Types of fuel

Over the years, biodiesel has had bad press, mainly due to difficulties with quality control. While it is typically the first fuel that comes to mind when the topic of alternative fuels is brought up, it is not something we advocate the use of. There are several other fuel options in the UK and Ireland that offer better performance and reliability, such as hydrotreated vegetable oil (HVO) and gas to liquid (GTL).

HVO is a direct ‘drop-in’ replacement for diesel and is not comparable to biodiesel. It does not require engine modifications to gain the maximum benefits from the start, you simply clean the fuel tank and system and add HVO and start the engine. Watch the exhaust emit no smoke, even on start-up!

It also requires no change to servicing schedules, is odourless when burnt, is 100 per cent renewable and, because it is biodegradable, brings no concerns about spills or bunding. It results in a large decrease in emissions, up to a 90 percent reduction of carbon footprint, a 10 to 30 percent reduction in nitrogen dioxide (NOx), up to 100 per cent reduction in sulphur oxides (SOx), up to a 35 per cent reduction in particulate matter (PM) and a 20 per cent reduction in hydrocarbons. Its cold filter plugging point is -32⁰C, lower than both biodiesel (-5⁰C) and diesel (-12⁰C).

Another option is gas-to-liquid (GTL), which is currently available in the UK and mainland Europe. Named after the process it is made by, GTL offers similar savings to HVO, other than carbon as it is a fossil fuel. GTL is often used with diesel as a blend, which offers some exhaust emissions and operational savings and can be a steppingstone to reducing emissions further in the long run.

Though you might assume that heavy fuel oil (HFO) is similar to HVO initially, the two are very different. HFO is a heavy, tar-like fuel used in vessels and ships, offering no environmental benefits — it is important not to get them confused!


While HVO is marginally more expensive per litre than diesel, there are more factors in the equation. Firstly, purchasing in bulk can make the prices much more comparable— on a long-term generator hire, the costs may be very close or even the same..

In addition, because HVO contains no carbon, it does not have many of the downsides associated with blends that include diesel, such as water contamination or fungal growth affecting fuel quality. Diesel fuel related problems like lack of testing, treatment and fuel polishing are common reasons for breakdowns that HVO can avoid.

For example, it helps overcomes the breakdown risk associated with sizing a generator incorrectly. If sized too large for the application, the generator will run inefficiently, produce smoke and buildup carbon, meaning the operator will need to load bank test it and perform other maintenance activities to prevent a breakdown. While oversizing will still mean companies are paying more for a larger generator than they need, HVO does mean they don’t have to worry about carbon build up causing a breakdown.  HVO can therefore reduce maintenance costs, as well as provide operators with peace of mind that unexpected downtime is not about to hit.

Alternative fuels are growing in popularity as an environmentally friendly, reliable and financially justifiable option. In line with this, our entire generator fleet is suited to HVO and GTL, helping to keep your environmental conscience clear, and your equipment running.

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