How sustainable are alternative fuels in construction?
24 October 2023
Rental firms are coming under increasing pressure to reduce their carbon footprints by moving away from diesel-powered fleets. But what are the alternatives? And could they be just as bad for the environment - if not worse? Lucy Barnard reports.
“If you think too carefully about it all, it can drive you mad,” says Callum Mackintosh, the founder of Scottish Highlands-based excavator attachment rental firm HHH Equipment.
Macintosh, like many equipment hire bosses and business owners everywhere, is trying to decide which machines to buy and how to power his small fleet amid an increasingly complex and contradictory avalanche of information (and misinformation) on the subject.
A former president of the Scottish Plant Owners Association and key part of the organisation’s executive committee, Macintosh is no stranger to courting controversy. Last year he waded into a row with UK-based international infrastructure group Balfour Beatty over its decision to avoid the use of hydro-treated vegetable oil (HVO), a fuel made predominantly out of used cooking oil, on its sites.
The row, which centres around whether or not by opting for a fuel which emits lower carbon emissions construction machinery users are inadvertently contributing to deforestation in Indonesia and Malaysia.
In a position paper the company published in 2022, Balfour Beatty said that it had called a halt to its use of HVO due to its concerns over the “complex and opaque” supply chains associated with it (see below) and “insufficient information provided about its sources, transportation and production methods.”
Mackintosh disagrees. In a strongly-worded rebuttal of Balfour Beatty’s stance, he argues that HVO offers a chance for contractors to reduce carbon and other emissions immediately. Waiting for the outcome of an HVO sustainability life-cycle study to be completed could take years, he says, while Balfour Beatty will continue to burn diesel.
“By using HVO contractors can drastically reduce their carbon emissions, their nitrogen oxide levels and the amount of soot they produce today,” he says. “I suspect what is really driving Balfour Beatty’s position over HVO is actually a commercial and financial decision to continue using diesel because its costs 10% -15% less.”
Balfour Beatty responded to Mackintosh saying that the company’s position on HVO “has been carefully considered and is not reflective of any commercial or financial decision, but of our determination to act responsibly and consider the full implications of our actions - making sure that we are not solving one environmental challenge by creating another.”
And as pressure continues to grow on individuals and firms to take immediate action to reduce their environmental impact at the same time that economic pressures are prompting many to look for ways to reduce costs, the row between Mackintosh and Balfour Beatty is typical of an ongoing public debate about just how ‘green’ alternative fuels really are.
One of the most politically-charged ‘alternative’ fuel is hydrogen – a fuel with the potential to power heavy construction equipment as a like-for-like replacement for diesel.
In theory, renewably-powered electrolysis, splitting water into its hydrogen and oxygen components should produce hydrogen with minimal lifecycle emissions. This ‘green’ hydrogen can then be put through a reverse process in a hydrogen fuel cell or ‘burnt’ in an internal combustion engine to produce just energy and water.
Equipment manufacturers including JCB, Caterpillar, Volvo and John Deere have invested heavily in producing hydrogen-fuelled machines which they say provide a more suitable zero-carbon alternative for heavy equipment than batteries due to the machines’ high-power demands.
“Hydrogen internal combustion engines provide a viable zero-carbon fuel option for heavy-duty, high performance applications like concrete mixer trucks, which are often subject to arduous duty-cycles and tough terrain,” says Jim Nebergall, general manager at Cummins Hydrogen Engine business.
However, climate campaigners say that with limited renewable energy available for producing hydrogen, most of the fuel is, at least in the near future, likely to come from so-called ‘blue’ hydrogen, which is still extracted from fossil fuels but where the carbon emitted is then captured and stored underground.
“While truly green hydrogen may have a limited role in hard-to-decarbonise sectors, visions of a sprawling hydrogen economy are a dangerous myth,” says Sarah Lutz, climate campaigner at Friends of the Earth.
Meanwhile others point out that even battery-powered machines, often considered the most sustainable option for both transport and heavy machinery, come with their own environmental cost. This is mainly due to the hefty carbon footprint associated with manufacturing their batteries as well as the fact that most of the cobalt used in lithium-ion batteries is mined in the Democratic Republic of Congo, often under slave-like conditions.
Back in the Black Isle, Macintosh says that most rental companies want to move to more sustainable alternatives to diesel but continuing public debate about their real environmental impact, coupled with some very real practical issues around cost and availability, is putting them off.
They are concerned that if they invest too early in a fuel type which turns out to be later discredited on environmental – or other – grounds, they could be left with a while elephant.
“Buyers and end users are afraid to invest because they don’t know which avenue to take. It’s a Betamax/ VHS sort of situation,” he says, referring to the competition in the 1980s between two rival videotape formats which initially left consumers unsure which type of machine to buy.
Weighing up the options:
Hydro-treated vegetable oil (HVO):
For: Hailed as a viable diesel alternative which generates up to 90% less greenhouse gas and emissions, reduces nitrogen oxide levels by up to 30% and reduces the amount of particulate matter by up to 86%, the second-generation biofuel, made from pre-existing bio-waste products, has been adopted by major construction companies including Skanska, Lendlease, BAM and Sisk for at least some of their operations. The oil is already available in large supplies and can be used as a direct replacement for diesel in internal combustion engines.
Against: Although fossil-free and is not derived from crude oil, it is still largely derived from vegetable oil and still emits some carbon when burned. Moreover, the biggest concerns about HVO come from trying to establish its origin. Critics argue that the supply chains for the oil are often opaque. Moreover, they say that if not made into machine oil, the used cooking oil which is the main ingredient of HVO is often used as animal feed. If an uptick in demand from construction machinery users makes used cooking oil scarce, it is likely to push up the price of other alternatives including palm oil – a major driver of deforestation in some of the world’s most biodiverse forests.
For: Machines which run entirely on batteries have no tailpipe emissions which means they produce no carbon dioxide or other emissions when driving, reducing air pollution. Moreover, even taking into account the higher energy costs of manufacturing EVs, research from the International Energy Agency (IEA) shows that over the lifetime of an electric machine, its total carbon output is lower than that of a typical internal combustion engine (ICE) powered vehicle.
Against: EV batteries are mostly made of mined lithium, nickel and cobalt. This means that the process of manufacturing an EV can lead to more carbon emissions than those produced manufacturing an ICE equivalent. Around 70% of the world’s cobalt is mined in the Democratic Republic of Congo where international aid organisations say child labour, modern slavery and human rights abuses are major concerns. In many parts of the world, battery charging stations use electricity generated by fossil fuels such as coal and natural gas which further increases the carbon footprint of EVs. Moreover, the market for recycling EV batteries is in its infancy.
For: When hydrogen reacts with oxygen, it generates only electricity, water and heat. This means that hydrogen produces no carbon emissions. It one of the most abundant elements in the universe. Moreover, if obtained through electrolysis of water powered by electricity produced from renewable sources the extraction process for producing hydrogen can also be carbon-free.
Against: So-called ‘green’ hydrogen produced from renewable sources accounts for less than 1% of global production because it is currently so expensive to produce. The majority of hydrogen currently produced comes from coal (brown) or gas (grey), a process which not only releases carbon dioxide but also releases unburnt methane into the Earth’s atmosphere. Instead, energy suppliers say that ‘blue’ hydrogen which creates hydrogen, mainly using natural gas and then uses carbon capture and storage to bury the CO2 underground, can be used as a ‘low carbon’ alternative. However, some studies show that ‘blue’ hydrogen has a larger greenhouse gas footprint than burning gas, coal or diesel oil for heating. Another problem, scientists say, is that when stored hydrogen seeps into the atmosphere, it reduces the concentration of molecules that destroy the greenhouse gases already there.