The pressure to reduce emissions in the transport sector shouldn’t rest solely on the shoulders of electric vehicles. Alternative fuels such as hydrotreated vegetable oils (HVO), biodiesel, hydrogen, sustainable aviation fuel (SAF) and biomethane can all offer net zero or near net zero transport fuel options, and are being actively explored and developed for use especially in shipping, aviation and haulage.
According to the International Council on Clean Transportation, as many as 15.5 million barrels a day of crude oil used for transport could be replaced by sustainable biofuels, equivalent to 25 per cent of today’s transport energy demand.
The current reality, however, is that these fuels remain at a relatively nascent stage in terms of their usage. Experts say myriad barriers to their production at scale and widespread adoption must be overcome before they can play a meaningful role in the decarbonisation of transport.
According to Brian Caulfield, professor in transportation in the Department of Civil, Structural and Environmental Engineering at Trinity College Dublin, baby steps have been taken to make the traditional fuels we already use somewhat more environmentally friendly.
“In recent years we have added more organics into our fuels and increased the percentage of renewables used at our petrol stations,” he explains. “That is doing a bit but it doesn’t help with pollution or the climate issue at all.”
Although he says alternative fuels are being researched extensively, they account for a tiny fraction of our overall fuel consumption.
“None of these are imminent or will be in regular use in the next 20 years,” he says. “These are more likely to be used in heavy goods vehicles – and this is where we need them. Putting massive batteries into trucks isn’t the best idea because they are heavy and they use their own energy themselves due to their size. Trains will also benefit from these fuel sources.”
“Alternative transport fuels are a very important part of the energy transition, and should be seen as complementing electrification, not as a competing solution,” says a spokesperson for the Sustainable Energy Authority of Ireland (SEAI).
Ireland already utilises biofuels including HVO and biodiesel in transport fuels (both petrol and diesel), which is mandated through the Biofuels Obligation Scheme. In 2023 the share of energy from renewable sources in final consumption of energy in the transport sector was 7.6 per cent.
“Most of this was because of biofuels blended into the supply before the pump, reducing emissions from transport without any changes to vehicles or purchasing behaviour. This is currently the most advanced use of the alternative fuels,” says the SEAI spokesperson.
When it comes to biofuels, the key considerations to scale are the cost of production, the availability of resources to produce the fuel and the sustainability of these resources.
“Examining these considerations in the Irish context would demonstrate that biofuels will have an important but limited use in a low carbon transport energy system,” says the SEAI spokesperson.
For example, there are concerns that they will use land that would otherwise have been used for the production of food or crops. There is also an energy security consideration, as Ireland is import dependent on biofuels currently.
This comes on foot of recent concerns that tainted fuels are entering the EU market, with recent allegations that palm oil, a feedstock restricted in the EU due to its supposed contribution to deforestation abroad, is being passed off as used-cooking oil (UCO), a waste biofuel material.
Yet the Government has significant ambitions for biomethane production and use, and has outlined this in the national biomethane strategy. Implementation of this plan will require the development of significant infrastructure for biomethane production, distribution, grid injection and usage.
“It is feasible that some of this biomethane would be used in heavy transport, but very unlikely to be used in private transport,” notes the SEAI spokesperson. There is a similar strategy for hydrogen production and usage, which may see it eventually play a role in heavy transportation and aviation but not until 2030 at the earliest.
SAF faces the same challenges as biofuels. Although a small amount of SAF was used for the first time in the State in 2022, current projections for production indicate that this will have a limited impact on aviation emissions in the immediate future.
However, the aviation industry believes it will eventually have a big impact and projects that SAF will contribute around 65 per cent of the emissions reductions needed for it to reach net zero by 2050.