Alternative Fuels – The Pro’s and Con’s


Alternative liquid fuels have been developed to reduce dependence on traditional fuels, like petrol and diesel, and to limit impact on health and the environment. They seek more significant sustainability benefits through the use of green energy sources, as well as innovative production methods which result in cleaner emissions.

Not all liquid fuels share the same characteristics, though. The challenge is to choose the optimal solution to suit your business from a range of options, which you can explore in-depth by downloading the Certas Energy free guide – The Alternative Guide to Navigating the New Energy Mix

Here we assess the pros and cons of the top alternative liquid fuel contenders available to sustainability-conscious organisations:


Compressed natural gas (CNG) is methane stored at high pressure. CNG can be used as an alternative to petrol, diesel and propane (LPG) and produces fewer undesirable gases than these conventional fuels.

● Cost-effective—30%-40% cheaper compared to diesel
● Reduces emissions—less NOx and up to 85% less CO2 compared to diesel
● More efficient—extended running time and reduced engine noise

● Expensive to convert—storage tanks are costly
● Challenging to store—must be kept at a specific temperature
● Limited availability—UK has underdeveloped supply chain


Liquefied natural gas (LNG) is gas that has been cooled to liquid form to enable non-pressurised storage or transport. It is safer and more convenient to use than pressurised gases and is popular with the marine sector.

● Clean—odourless, colourless, non-toxic and non-corrosive
● Reduces emissions—delivers CO2 savings
● Easy to store—lightweight tanks minimise fuel consumption in transport and does not require the same strict storage conditions as CNG

● Lower energy density—doesn’t deliver the same efficiency benefits as CNG
● Expensive—although more straightforward to store, the fuel is more costly than many alternatives


Hydrotreated vegetable oil produced from vegetable fats and oils. Unlike conventional biodiesel, hydrogen, rather than methanol, is used as a catalyst, which makes HVO cleaner-burning and ensures a longer shelf life.

● Reduces emissions—releases fewer NOx, PM and CO2 emissions
● Drop in fuel—no need to change the infrastructure
● Longer shelf life—compared to regular biodiesel

● Inconsistent—quality can be an issue when palm oil is used
● More expensive—not as cheap as diesel, but less costly than updating infrastructure
● Limited availability—UK has underdeveloped supply chain


A biofuel is a fuel that is produced through contemporary biological processes, such as agriculture and anaerobic digestion, rather than by geological processes such as those involved in the formation of fossil fuels, such as coal and petroleum, from prehistoric biological matter.

● Renewable—made using replenishable materials
● Reduces emissions—releases less CO2
● More efficient—can be blended with diesel, with higher percentage blends shown to improve miles per gallon

● Maintenance issues—some OEMs complain of clogged filters
● Not as clean—can worsen air quality by emitting NOx
● Requires conversion—completely different specification


GTL products such as Shell GTL Fuel are created from natural gas using the Fischer-Tropsch process, which produces more consistent and uniform molecules than conventional crude oil refining. 

● Reduces emissions – cuts NOx, PM, CO and hydrocarbon levels
● Clean – produces less noise, smoke and odour
● Drop in fuel – does not require any engine modifications, nor does existing fuel need to be drained from tanks before use 

● Cleaner rather than greener – does not reduce CO2
● Cost – similar to a premium diesel, yet less costly than making engine and/or infrastructure changes

For a detailed break down of the different compositions that make up the alternative fuel landscape, download The Alternative Guide to Navigating the New Energy Mix for free here.

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