Renewables may actually keep carbon fuels going for decades to come, but a new group of energy-rich countries will emerge.
The road user is not alone in attempts to end oil’s dominance of transport. In 2018, the International Maritime Organization (IMO) committed to halving the CO2 emissions from shipping by 2050 and started to tighten up rules to bring forward reductions over the coming decade. Airlines have joined the chorus. In September, British Airways and the 14 other members of the Oneworld Alliance pledged to cut carbon emissions to zero by the middle of the century.
The question is what these new vehicles will use instead. For most European governments, the answer for most cars and light vans is electrification. The UK will allow petrol-hybrid vehicles to be sold until 2035, as long as their tailpipe emissions are more or less zero for most of the time. The emphasis will be on installing more charging points and promoting battery-focused technologies.
Such a transition would put a major dent in the carbon dioxide emissions from transport. Passenger cars and light goods vehicles accounted for around 70 per cent of transport emissions in the UK and around 60 per cent of the 8 billion tonnes of carbon dioxide emitted globally in 2018. The other third, which includes heavy goods vehicles, ships and aircraft, faces major problems with such a transition. Batteries are heavy and carry a fraction per kilogram of the energy stored chemically in petrol and kerosene.
In a Stocktaking Seminar held in September 2020 to update members on the ramifications of emissions-control measures, the International Civil Aviation Organization head of environmental standards Neil Dickson told delegates: “A smartphone battery with the same energy density as kerosene would last two months on a single charge.”
Companies such as Wright Electric are investigating the possibility of building battery-powered aircraft, but Wright CEO Jeff Engler says he does not see them being viable across the board. Even the most optimistic projections for energy density point to battery-driven planes being useable only on short-haul routes of under 1,500km by 2050. Though they make up half of all flights, short-haul trips only account for less than 30 per cent of the fuel consumed, according to the International Energy Agency. For the remainder, liquid fuel is here to stay and there are no viable alternatives that do not have a lot of carbon in them.
How then, do airlines in the Oneworld Alliance plan to get to net-zero? Through carbon accounting and what the industry calls sustainable aviation fuel (SAF). This is carbon-based fuel from crops and other organic sources that either replicates the mixture of molecules in typical aviation kerosene or mimics its behaviour. In theory, as long as the original sources are themselves carbon sinks and not fossil deposits, burning the carbon they contain creates a net-zero closed loop, though the precise arithmetic remains contentious.
The technical details of combustion are easier. Over the past decade, ASTM International, the body responsible for creating fuel standards for aviation, has given the green light to eight different recipes, most of which need today to be mixed with regular fossil-sourced kerosene to work reliably. Some of the blend amounts are as low as 10 per cent though a couple are now approved to be used standalone in commercial flight and are used in limited quantities already. Virgin Atlantic’s planes had flown a total of a million kilometres by early summer 2019 on fuel that includes butanol brewed by re-engineered yeasts created by biofuel specialist Gevo.
A prime source of food for yeast is sugar, which suggests a food source, one that airlines and some governments are increasingly keen to distance themselves from. With its RED II directive the EU is clamping down on the use of biofuels sourced from food crops such as corn. The EU aims to phase out the use of palm oil in fuel by 2030, a move that resulted in Indonesia complaining to the World Trade Organization of discrimination against one of its major crops. Growers of rapeseed and soya also face limits on how much will be used in fuel because of fears that increasing their use will see more arable land being lost to food production. That means both existing and new suppliers of SAF need to look to new sources of creditworthy carbon.
To widen the potential source of sugars, Gevo has worked with partners such as Renmatrix to convert the cellulose in stalks and waste wood into yeast-compatible sugars. “We can use carbohydrates from whatever source in the US it makes sense to use,” said Gevo CEO Patrick Gruber in a pitch to investors in the early autumn.
Waste overall looks a far better bet for fuel suppliers. With the help of a £500,000 UK government grant and funding and technical help from British Airways and Shell, start-up Velocys obtained planning permission in June 2020 to build a plant it calls Altalto between Immingham and Grimsby. “Altalto will take ordinary black-bag waste that would otherwise be landfilled,” says Neville Hargreaves, vice president waste-to-fuels at Velocys.
When completed, the Humberside plant will take up to 500,000 tonnes of household waste a year, using high temperatures to vaporise it into a mixture of hydrogen and carbon monoxide. This combination of gases, often called syngas, is the source for a well-established large-scale method of producing fuel-ready chains of hydrocarbons: the Fischer-Tropsch reaction. The company claims Altalto could yield 60 million litres of aviation fuel each year.
Velocys is far from alone. Fulcrum Bioenergy is further ahead though with a smaller plant design that it expects to finish building near Reno, Nevada by spring 2021. It will turn 175,000 tonnes of municipal waste per year into a fuel precursor that will then be processed by established refiner Marathon Petroleum into a usable SAF mixture. Bruno Miller, managing director of fuels at the company, points out that waste has two big advantages: “It exists in very large volumes and in ideal locations: close to urban centres. We already have an established infrastructure to collect trash and aggregate it,” he says.
Under the contracts Fulcrum has, the waste collectors will bring their refuse for free to the plant as that helps them avoid using landfill. The company then needs to pick out metal and glass before feeding the mixture of plastics, food, paper and wood to the gasifier. “Even the best recycling programmes miss a fair amount. This is the last chance to recover those other materials,” Miller adds.
Even for a fuels market as seemingly limited as aviation, an eyewatering amount will be needed to hit the net-zero targets. By the end of the 2010s, commercial flights burnt more than 400 billion litres a year, a demand 500,000 times higher than the amount of available SAF, which totalled 8 million litres. Even general-purpose biodiesel for the wider market accounted for just a billion litres. Thanks to a rush of plant announcements, SAF production is ramping up. The ICAO in November estimated 13.6 billion litres per year of SAF would be available by 2032. But that remains a small fraction of the final likely demand even if the post-Covid environment slams the brakes on the expansion of airline routes.
The scale of the demand has led to questions as to whether it will be possible to obtain enough waste and biomass to fuel net-zero flights completely. The US Department of Energy concluded in a report on sustainable aviation fuel published in September 2020 that the US aviation fuel market alone could consume the country’s biomass. As the margins on fuel for commercial flight are not as good as many other applications, such as biologically derived chemicals and materials and even road vehicle fuel for those cars that have not been replaced by electrics, the sector could easily find itself starved of the capital investment and feedstocks to drive to net-zero.
One option is to explore other biological sources, such as microalgae. They can potentially be farmed on land that cannot be used for normal agriculture, in sealed ponds suspended in shallow waters offshore or even in industrial tanks lit by low-power LEDs fed by renewable electricity in a form of biological carbon capture.
Japanese company Euglena, which named itself after the Latin name for the algae it favours, claimed in 2012 the organism thrives in atmospheres rich in carbon dioxide and even switches production of the starch it normally makes to oils when starved of oxygen.
Algae-derived fuel has looked attractive for well over a decade. In 2009, ExxonMobil invested $300m in Synthetic Genomics for work on algae re-engineered to boost oil production amid a flurry of private-equity investments in microbe-focused fuel start-ups. But it has been an uphill struggle against the chemical processes favoured by a number of established SAF suppliers.
Before the rush of government and organisational commitments to net-zero over the past couple of years, microbe and algae specialists such as Amyris, OriginOil, Sapphire Energy, Solazyme and Solix had to face the vagaries of the wildly fluctuating price of crude oil. The crash of 2016 sank several while others moved into adjacent, higher-margin markets by altering the chemicals their microbes and algae could make or simply quitting algaculture.
In 2017, his company having made the transition to ingredients for cosmetics and perfumes, using derivatives of a microbe originally engineered to make diesel, Amyris CEO and former BP executive John Melo described the problem to analysts in a conference call: “We went from a world where we thought we were going to have scarcity of oil to a world today where we have abundance of oil. In a world where there is abundance, it’s very difficult for an emerging technology, especially biotechnology, to really compete in a world that has abundant hydrocarbons with an infrastructure that’s fully depreciated that can make these products really cheap.”
Algaculture suffers from a major problem in that, for most processes, the algae themselves need to be dried and pulverised to release their oil content. The heat adds a large amount of cost, though researchers have in recent years come up with several ways to try to release the oil without that step, using electric shocks or high-speed jets.
UK startup Phycobloom aims to sidestep the problem by genetically engineering algae that simply release the oil as they grow so that it can be skimmed off. The question is whether this generation of algaculturists will fare better than the last as governments rewrite their rules.
Germany is ahead of most other countries with its plans for sustainable fuel for aviation. The home of the Fischer-Tropsch reaction sees a future where even biological sources of carbon for kerosene barely feature on the fuel menu. As part of the nation’s strategy for an economy built around hydrogen and so-called power-to-x (PtX) technologies that use electricity to help synthesise a wide range of chemicals and materials, the environment ministry published a draft bill in September 2020 that guaranteed a minimum quota for electricity-based aviation fuels.
For carbon-based efuels, electrolysed hydrogen is combined in a syngas mixture with carbon monoxide that can be derived from carbon dioxide captured from industrial plants or even from the air, though direct air capture is more energy-intensive. The dissociation of water into hydrogen and oxygen is an energy-intensive step that calls for the electricity fed into the process to be a fraction of today’s price or for producers to find novel catalysers that slash the power needed.
A recent experiment by a team at Spain’s Polytechnic University of València found microwaves can avoid the need for electrolysis. In Sweden, researchers at Uppsala University have used sunlight to give electrolysis a helping hand for a form of industrial photosynthesis. Synthetic biology may yet play a role in the future as a few micro-organisms can be coaxed into producing hydrogen as part of a natural photosynthesis reaction.
Many other projects are under way. According to Lux Research, the number of patent applications for water electrolysis for green hydrogen has increased 14 per cent per year over the past decade: more than 10,000 applications tackle the problem.
Though advances may make electrolysis less power-hungry, its thirst for cheap energy might lead to a new collection of energy barons that benefit from the accidents of geography. Although it is thousands of kilometres from most industrial centres, which will increase its shipping costs, the government of Chile believes the nation has the opportunity to capitalise on a hydrogen revolution. The exceptionally long and narrow coastal geography of the country provides it with an unusually strong rationale for developing an industry focused on synthetic fuels.
‘We think power-to-x is an opportunity for international trade. As they are fuels and gases they can be easily transported. Use the container ships we have today.’
The Atacama desert plateau is home to a cluster of experimental solar farms (pictured above) that may form the basis of a huge array providing energy purely to generate hydrogen. The high plateau and lack of cloud cover means the Atacama has the highest level of solar irradiation in the world. Thousands of kilometres to the south, strong winds whip around Cape Horn. Here, the country plans wind farms that will supply another cluster of electrolysis facilities.
The split will make it easier to supply customers around the world with either liquefied hydrogen or a hydrogen carrier such as ammonia: Japan and the rest of Asia from the solar generators; Europe from the south.
“We think power-to-x is an opportunity for international trade. As they are fuels and gases they can be easily transported. Use the container ships we have today,” says Carola Kantz, deputy managing director of power-to-x applications for the German Mechanical Engineering Industry Association.
Other countries in the global south may also become much stronger in energy exports without being reliant on oil or coal. Elizabeth Minchew, associate operations officer at the International Finance Corporation, notes: “We did a report on offshore wind that found there was double the amount of offshore wind in Africa versus domestic demand.”
Ammonia created by the generated electricity may even power the ships that carry the hydrogen from Chile and other countries. Alongside synthetically produced methanol, which is another easy-to-obtain product from the Fischer-Tropsch reaction, the noxious gas is currently one of the front-runners in plans to decarbonise shipping in order to meet the IMO’s targets, though it will involve a significant retrofitting programme to make engines compatible and burn the ammonia cleanly without producing unwanted nitrous oxide, another powerful greenhouse gas.
At the same time, electrolysis technology provides an opportunity to democratise fuel supply instead of concentrating within a small collection of states. Alexander Mahler, adviser to the International PtX Hub Berlin and the German Association for International Cooperation, told the ICAO this is the aim of the PtL-SAF project: “We plan to build at a remote airport in Brazil. These airports can’t be supplied with fuel in the normal way – it has to be flown in. This raises the cost of fossil fuels and provides a business case for sustainable aviation fuel made using PtX.”
A solar generator close to the airport will provide the power for a small fuel plant that, in principle, will be able to supply the aircraft for their return flights. “It can offer an economical resource for remote locations across Brazil and there are many similar remote airports all over the world,” Mahler adds.
This distribution of creation may be essential if power-to-x is to take hold. As with biofuels, satisfying the relatively small fuel demand of aviation alone would, according to the DoE study that questioned biogenic carbon capacity, require six exajoules of energy per year, or 7.5 per cent of 2018’s electricity demand globally. Mahler counters that though the figure is striking, the energy needed to service that demand is abundant: it’s the harvesting that has proved difficult so far and that will be easier with the decentralisation of fuel production, just as long as the incentives are there to make cheap renewables-based generation workable.