Oil-fueled transportation has been one of the most, if not the most, significant contributors to economic development and global interconnectedness throughout recorded history. Without it, we could never travel to foreign countries. We could never have the convenience of a car or bike for everyday use, nor access to products or food from the other side of the world. Our economies would not be able to experience the benefits of globalisation we now take for granted. Everything about our life would be radically different, and far less prosperous.

But, our utilisation (and dependence) on oil has come at a massive cost. Transport produces 16% of global greenhouse gas emissions, almost all of which is from oil-based fuels. In higher-income countries riddled with SUVs, this share is far higher. Throughout human history, oil has been responsible for one-third of total carbon emissions, causing close to 0.3˚C of warming.

The party is over. The EU parliament has just banned the sale of petrol cars from 2035, following in the footsteps of the UK with its 2030 ban. We need something else to power not just our cars and bikes, but also our trucks, tractors, ships, and planes. And, as you should be very aware of by now, that something else has to be completely clean whilst providing the same performance as oil-based fuels.

But finding alternative fuels is much, much harder than it seems.

This article is a turning point in The Climate Project. Reading Episodes 2 and 3, you may be under the impression net-zero is going to be easy.

It’s not.

Electricity and buildings are easy to decarbonise — they are the low-hanging fruit of the climate crisis, the economically advantageous stuff we can scale right now.

Let me tell you, many sources of emissions don’t even have any solutions, let alone economically viable ones. It’s time we woke up to the fact that it will take a lot to get to net-zero by 2050. By the end of this article, I trust you’ll realise just how difficult the transition is going to be.

Whilst it’s true we can decarbonise bikes, cars, buses, and vans with batteries — and in many cases, these alternatives can already compete with combustion engines — that isn’t at all the case with trucks, ships, and planes. There are ways we could go about decarbonising them, but few really work. That leaves a lot of emissions — as much as 7% of the global total — on the table.

So, what are our options?

Three fuels could take up oil’s mantle: electricity, hydrogen (or hydrogen-based fuels), or biofuels.

Electricity can power transport in two ways. As with electric cars, bikes, buses, and trucks, batteries can store electricity, and power the vehicle through an electric motor. Current batteries are lithium-ion batteries, but solid-state batteries are a type of promising battery chemistry that could dominate the market in the future. The other way electricity powers transport is through direct wiring. The vast majority of rail systems are powered by electricity that is directly wired to the train. However, because these direct wiring systems require fixed routes, they aren’t feasible for compact vehicles that travel on roads.

Hydrogen powers transportation through a fuel cell, which converts hydrogen into electricity to power a motor. That hydrogen is called ‘green’ if it’s produced by electrolysis: the conversion of water into hydrogen and oxygen through exposure to an electric current. The use of electrolysis is rapidly growing, but over 95% of hydrogen is still produced from natural gas and coal in processes that emit carbon dioxide. Green hydrogen can also be transformed into other combustible fuels such as ammonia and synthetic e-fuels — hydrocarbons produced from combining hydrogen and carbon that has been extracted from captured carbon dioxide.

Finally, biofuels are hydrocarbons produced from plants such as sugarcane and corn. The biggest downside of biofuels is that they use crops as feedstock. This either redirects farmland away from food production (contributing to several food crises including the current one that has arisen in the wake of the Ukraine war), or it causes more deforestation, leading to massive ecosystem loss and carbon dioxide emissions. ‘Advanced biofuels’, which are produced not from entire crops but rather only from waste crops from food production, solve this problem but are understandably more expensive.

Importantly, the viability of these fuels as an alternative to oil should be determined by the following six criteria:

1. It has to be zero-emissions or rapidly approaching zero-emissions.

2. The fuel must have a high energy density (the amount of energy in a specific volume of the fuel).

3. It must also have a high specific energy (the amount of energy per kilogram of the fuel).

4. It has to be cheap per unit of energy or at least heading that way.

5. It must be readily available and scalable.

6. Refuelling forms of transportation with the fuel must be an easy process.

Unfortunately, too often we ignore the first criteria when assessing the viability of alternative fuels, severely undervaluing them. Carbon pricing fixes this by embedding criteria one into criteria four — but that’s for another article.

Cars & Motorbikes

EVs have come a long way in the past decade. They now represent 9% of car sales, 42% of two- and three-wheeler sales, and 44% of bus sales worldwide. However, those sales are highly concentrated in just a handful of countries. Half of electric car sales in 2021 were in China, 35% were in Europe, 10% were in the US, and only 5% in the rest of the world. China also represents 95% of registrations of new electric two- and three-wheelers and 90% of registrations of new electric buses and trucks.

On the other hand, in Australia, electric cars were only 2% of total sales in 2021, and represent less than 1% of cars on the road. In Brazil, Indonesia, and India, three of the largest emerging economies, electric cars were less than 0.5% of sales.

By replacing petrol and diesel-powered passenger vehicles, we can eliminate 45% of transport emissions or around 8% of total greenhouse gas emissions. Unfortunately, as they stand today, electric vehicles have a few glaring problems slowing their rollout.

The first is known as ‘range anxiety’: electric passenger vehicles have lower ranges than their combustion engine counterparts. This is because batteries have low energy density and specific energy. EV manufacturers could build a battery with a massive range, but it would weigh too much and take up too much space. Fortunately, batteries will become denser; with that will come better range.

Short-range isn’t much of an issue with extensive charging infrastructure, and in particular, fast-charging infrastructure. China has the majority of the world’s electric vehicle chargers — other nations need to follow suit if they are to facilitate the rollout of EVs. Batteries will also develop to accept higher power charging; this will gradually reduce charging times to be competitive with combustion engine vehicles.

Almost a billion people do not have access to electricity, let alone EV chargers. Massive investment into electricity access will be needed in developing countries if we are to make the global fleet of vehicles electric.

Hybrid vehicles are a great alternative in large countries like Australia where range is especially important. Hybrid owners can make 90% of trips on battery power, reserving the fuel tank for longer journeys.

The second downside of EVs is cost. The average EV is still 40-50% more expensive than the average ICE vehicle. Interestingly, in China, the premium for EVs is only 10%, due to low manufacturing costs and the fact that Chinese vehicles are relatively small. Lower fuel and maintenance costs (because EVs are far simpler and wear down slower) somewhat offset the higher upfront cost, but not enough to make EV ownership cheaper overall. Batteries have been rapidly decreasing in cost for decades. This will continue, bringing down EV costs below those of petrol equivalents.

EVs also have a significant carbon footprint of their own, both in their manufacturing and their electricity use. The electrification of passenger vehicles needs to coincide with electricity becoming renewable in order to realise their main benefit.

Another problem with EVs often discussed is their drain on electricity grids. If the US car fleet was entirely electric, and everyone charged their cars at home at the same time, the electricity supply would need to be double what it is today. However, we will build enough renewables in the coming decades to account for this extra capacity. Plus, as I talked about in Episode 2, EVs will provide a massive source of energy storage, essential for the balancing of renewable grids. EVs can charge during the day when solar power is plentiful and release some power at night when demand soars, earning money in the process.

The rollout of EVs is essential to achieving net-zero. They will soon be better than petrol and diesel vehicles in terms of cost, range, and charging infrastructure in many countries, perhaps even in this decade. In order to get there, and to scale their rollout once we are there, strong policy support will be essential. This will have to include supply-side policies such as the EU and UK bans or China’s EV production targets, demand-side policies such as purchase subsidies, tax incentives, or registration and toll road cost deductions, as well as massive investment into charging infrastructure. China and the EU both have some version of all of these policies; countries such as Australia barely have any. The world needs to follow China and the EU’s lead on EV policy.

Buses & Trucks

Although there are far fewer buses and trucks on the road than cars and bikes, due to their size, heavy vehicles represent 30% of transport-related emissions, making up around 5% of total greenhouse gas emissions. Whilst buses are going electric with ease, trucks are a much harder proposition.

Buses come back to a central depot every day, making it easy to regularly recharge themselves if they were electric. However, not only do trucks rarely come back to a central point, but they need long ranges to make massive cross-country trips. Batteries are not yet energy-dense enough to power a truck for long-range journeys whilst still leaving enough space for cargo.

As batteries improve their energy density and specific energy, electric trucks will become more viable. But we are way off that point. Only 1% of truck and van sales are electric.

Due to its high specific energy (three times that of diesel), many believe hydrogen fuel cell trucks are a viable alternative to diesel trucks. However, gaseous hydrogen has an extremely low energy density; liquefying the gas is the only way to make the fuel dense enough to fit in a fuel tank. But liquefying hydrogen takes a lot of energy, adding to its already high cost.

On top of that, there are very few hydrogen refuelling stations globally (less than 1000), a necessity for the rollout of fuel cell trucks. And many truck manufacturers are more than five years off completing their hydrogen projects. Within that time, battery-electric trucks will almost certainly have cemented their position as the obvious alternative to diesel trucks.

As well, many countries require truck drivers to stop for up to an hour every four or five hours for safety reasons, providing more than enough time, provided fast charging speeds increase, to fully charge battery-electric trucks without any disruption. Within the next 20 years or so, electric trucks could start to dominate our roads.

For the time being, trucks will continue to be powered by diesel. Better fuel efficiency will reduce some emissions, but with a growing global fleet, heavy vehicle emissions could easily grow for decades to come.

We have just reached the turning point in this series. Trucks are the first source of emissions with little hope of decarbonising by 2050.

It only gets worse from here.

International Shipping

Although it is the most energy-efficient form of cargo transportation, international shipping still contributes around 10% of transport-related greenhouse gas emissions, almost 2% of total emissions.

The UN’s International Maritime Organisation (IMO) has proposed various energy efficiency measures in order to curb carbon dioxide emissions. However, they only entail a 2% annual reduction in emissions intensity from 2020 to 2030, only marginally more than the drop from 2000 to 2017, and only half the reduction needed as per the IEA’s net-zero pathway. Energy efficiency policies will not be nearly enough to put shipping emissions on the right path.

The real solution will be the introduction of low-carbon and zero-emissions fuels like biofuels, hydrogen, and hydrogen-based fuels like ammonia and synthetic e-fuels. Biofuels are currently the only such fuel in use but still account for less than 0.1% of shipping energy use. Under current policies, low-carbon and zero-emissions fuels are projected to represent 5% of shipping energy use by 2050. Under the IEA’s net-zero pathway, this number needs to be 83%.

A far stronger policy mix of taxes on shipping-related carbon emissions, aggressive R&D into alternative fuels, and stricter energy efficiency standards will be needed to reduce the price gap between current and alternative fuels, and incentivise investment in their development.

The World Shipping Council, a group of shipping companies, have pushed the IMO to build such a policy, asking for a USD 2 per tonne tax on shipping-related carbon emissions to fund R&D into alternative fuels. As of now, the policy has not been enacted — let’s hope it does sometime soon.

Aviation

Have you ever ticked that box to offset your emissions from a flight you’ve booked? You may have been under the impression this counteracted the warming effect of that plane ticket. You would be wrong. Not only are these offsets often incredibly poor quality (stay tuned for my carbon removal article), but carbon dioxide is actually a fraction of the problem.

In fact, carbon dioxide only makes up one-third of the warming effect of aviation. The majority comes from contrails, the white cloud-like trails you can see spurting from aircraft. They are produced from water vapour binding to soot exhaust, which freezes in the cool atmosphere to produce cirrus ice clouds. Although contrails reflect a lot of sunlight back into space during the day, they trap heat radiating from Earth in the lower atmosphere.

During the night, when there is no sunlight, this second effect reigns, producing a massive warming effect. In the few days around 9/11 when all flights in the US were grounded, the diurnal temperature difference (the difference between the maximum temperature during the day and the minimum during the night) decreased by almost 2˚C.

Aviation represents around 10% of transport-related greenhouse gas emissions, 2% of the total. Accounting for non-carbon-related warming effects, aviation contributes 5% of human-induced warming.

This reality puts a major spanner in the works for climate policy in the aviation industry. To date, the majority of emissions reductions have come from improvements in energy efficiency. This is done principally by reducing the amount of waste heat produced during fuel combustion. But cooler exhaust actually means more contrails, producing a net warming effect on the Earth.

Future emissions reductions in aviation depend on the introduction of alternative low-carbon and zero-emissions. Biofuels and synthetic e-fuels are called Sustainable Aviation Fuels (SAFs) by the aviation industry. If sourced correctly, they can cut out all carbon dioxide emissions from aviation. But both of them still produce a significant amount of contrails, albeit a lot less than traditional jet fuel. Plus, they are considerably more expensive than traditional jet fuel.

Neither green hydrogen nor battery-electric powered aviation produces contrails. But, they are both a long way off from being economically or technically feasible in aviation. Even liquid hydrogen takes up four times the space as jet fuel for a given flight. Plus, it’s significantly more expensive. When a traditional commercial aircraft takes off, a third of its weight is fuel. Batteries contain forty times less energy per kilogram than jet fuel. Accounting for the inefficiency of jet engines, the weight of batteries needed for a long-haul flight is around fifteen times that of jet fuel. Both of these technologies will improve, especially with increased R&D over the coming decades. But they are orders of magnitude off feasibility right now.

For the time being, it looks like SAFs might be the best solution for aviation. But in order to properly curb the warming effect of aviation, we need to dramatically reduce contrail production. Planes should consider flying lower where the air is warmer, as well as flying around areas with colder weather. The latter of the two would produce more carbon dioxide, but could easily be beneficial overall if done well. Contrails have by far the biggest warming effect at night — night-time flights should be cut where possible. And finally, much of domestic air travel should, over time, be replaced by high-speed rail. All of these changes will, at least in the short run, increase the cost of travel. That is a good thing. For too long we have been buying artificially cheap plane tickets, benefiting from the fact that we never consider the impact we have on the climate.

What’s the plan?

We need to make our alternatives to oil cheaper and better performing. It’s as simple as that. To decarbonise passenger vehicles and trucks entirely, batteries need to get better. Over time, they will naturally, but we need policy to be an accelerant.

To decarbonise shipping and aviation, we need more R&D in biofuels, hydrogen, ammonia, and synthetic e-fuels. At the moment, they are too expensive and poor performing. Hopefully, with increased investment, one or two of these fuels will shine through as a feasible alternative to oil. But companies need an incentive to make these investments. Market-based solutions such as carbon taxes are the best way to do that.

But even if all that happens as quickly as it can, we’re probably going to be left with five or six gigatonnes of transport-related greenhouse gas emissions in 2050, at the very least. There is little hope of reaching net-zero by 2050, and almost no chance we will keep warming below 1.5˚C.

But that’s no reason to give up. What we do to clean up transport, and every other source of emissions, will determine whether we end up in a world that’s 2˚C warmer, or 5˚C warmer.

Trust me, you don’t want to live in a world that’s 5˚C warmer.