Transport

The transport sector is the backbone of any productive system; enabling the mobility of people and goods means connecting people and nations and consequently fostering economic and cultural exchanges and social development. The complexity of the sector requires deploying a diverse mix of decarbonization solutions to meet the challenges within each of its four main segments: roadways, railways, aviation, and navigation.

Each segment has a different ease of decarbonization. Moreover, transport has strong interactions with other productive sectors and, in order to avoid rebound effects, it requires the power sector to be fully decarbonized and the cradle-to-grave energy supply chain to become increasingly efficient. Effective decarbonization pathways in transport rely mostly on technological solutions, new sustainable fuel development, and fuel shifts and are complemented by demand reduction and modal shift strategies.

Finally, different energy vectors will play a role on transport decarbonization. Direct electricity usage (through either batteries or electrified railways and electric road systems), hydrogen, synthetic fuels, and sustainable biofuels –properly allocated to hard-to-decarbonized modes – will all be important for transport decarbonization. As far as the use of biomass, scarcity of the resource and complexity in overall supply chain may suggest that
biofuels could be prioritized in particular modes of transport (e.g. harder-to-abate segments like long-haul aviation) or geographical areas (e.g. those not likely to proceed toward total decarbonization in the power sector in the near term).

The action areas in this sector include:

• A diverse mix of decarbonization solutions and energy vectors need to be sought by each transport segment: roadways, railways, aviation and navigation.
• Effective decarbonization pathways rely mostly on technological solutions, new sustainable fuel developments, and fuel shifts, complemented by demand reduction and modal shift strategies.
• In the road segment, CO2 emissions are easier to abate due to electric vehicles and fuel-cell electric vehicles for short-to-medium haul (freight, passenger, light-duty, or heavy-duty categories).
• The pathways for railway decarbonization are mostly based on fuel shifts from diesel to electricity or hydrogen.
• Concerning aviation, advanced jet fuels (such as synthetic fuels) are the only way to decarbonize the current fleet and the relevant one in the near future. Modal shift from air to land could be enhanced with innovative alternatives such as ultra-high-speed trains with the right policies in place.
• For similar reasons, long-haul navigation is hard to abate while short-haul navigation^[1] can be supplied by electricity or hydrogen technologies. Ammonia and hydrogen are currently being investigated in long- haul navigation.
• Use of biofuels and the sustainability of biomass for biofuels needs to be carefully assessed so as to avoid: competition with food production; deforestation or loss of biodiversity in natural regions; and, competition with industries that currently use the biomass for higher value products or uses. As sustainable biofuels will only be available in limited volumes, its use should be prioritised in hard- to-abate modes like aviation.
• Regulatory frameworks need to be technology agnostic to create a fertile environment for innovation, unleashing the potential of the research while fostering virtuous behaviours of citizens in all transport modes.
• Research and innovation need to investigate life-cycle analysis (LCA) and indirect land-use change (ILUC) impacts of these technologies to confirm sustainability, avoiding solution lock-in and stranded assets.

Case Studies

The following section outlines some of the most promising technologies in the decarbonization of transport. Some solutions may not be viable at large scale until the technology is more mature and it has been tested but there are a variety of solutions available.

Land transport

Light-Duty Vehicles

• Battery range improvement. One of the crucial features hindering the adoption of EVs is the relative range of batteries that can reach, for a 75 kWh pack, 500 km (Tesla Model 3). Innolith, a swiss-based start-up, is patenting a 1000 Wh/kg battery that leapfrogs the current 250 Wh/kg Panasonic battery used in Tesla models. The Innolith battery is based on “wet” liquid electrolyte technology for which the organic (and highly flammable) solvent containing the electrolytes has been replaced by an inorganic substance that is more stable and less flammable. The range expected to guarantee is around 1000km.^[2] This technology will also reduce costs by avoiding exotic and expensive materials. Other technologies are under development, such as solid-state storage with which a battery range can reach 800 km. Ultra-fast charging is also being deployed across Europe. For instance, the Ionity network allows to charges at a power of 350 kW, charging a battery in (10 to 15) minutes.

Heavy-Duty Vehicles

• Short and medium hauls can be electrified more easily taking into account that, distribution logistics requires lower battery ranges. In addition, short-haul logistics can more easily manage charging turn-overs, minimising the number of vehicles providing the same level of service. In certain geographies, such as Europe, the electrification potential is partly given by those transport activities that are characterized by short distance classes. In detail, the distance classes that cover the range of (0 to 150) km and (150 to 299) km account for respectively 22% and 20% of the total tonnes-km in 2017.^[3] In this regard, DHL is at the forefront in terms of substituting part of its fleet with electric vehicles.^[4] In Germany, Deutsche Post DHL Group decided to rely on StreetScooter, which retrofits existing vehicles with electric powertrains. Deutsche Post DHL has three different delivery van models with battery sizes ranging between (20 to 40) kWh and 76 kWh that cover (100 to 200) km and over 200 km, respectively.
• Long-haul transportation requires longer ranges than current batteries can provide, as well as more energy-dense electricity storage on board to reduce the pay-load. In order to boost the electrification of long-haul freight transport, mega-chargers will be needed. Tesla prospects a 30-minute charge able to cover a 600 km range. Nikola Motor is bringing FCEV semi-trucks to market with more than 13,000 trucks on pre-order. There are currently three models available with the last one to be launched for the European market in 2023. The range of those trucks is about (800 to 1200) km versus a standard ICE-truck range of (800 to 1600) km,^[5] in geographies where weight and dimension regulations allow them. The technology is mature but the cost is estimated to be double with respect to common diesel vehicles. The sustainability constraint rests on the supply of clean hydrogen. According to Eurostat data, 39% of the tonnes-km recorded in 2017 covers trips with ranges are between 300 km and 999 km, whereas 18% represents the tonnes-km employed to cover hauls of more than 1000 km.^[6] On the other hand, you have electric long-haul trucks like the Tesla Semi, with an announced range of 800km, and pre-orders in the range of a few hundred, including giants like UPS reserving 125 units. Scania, a truck manufacturer, expects electric long-haul trucks to be cost competitive with diesel by 2027, and FCEV to be cost competitive by 2047.^[7]
• Electric Road Systems (ERS) are mainly catenary-based or inductive rail-based. Siemens has investigated over-head catenary infrastructure (eHighway) and four pilot projects have been launched in Germany, Sweden, the US, and Italy.^[8] The benefit of such technology is given by the possibility to reduce the battery size and decoupe the battery range extension challenge. For full decarbonization, ERS technologies can be combined with smaller vehicle batteries, green hydrogen FCEV, or an ICE using advanced biofuels or synthetic fuels.^[9] The cost is estimated around 1.5 M€/km for electrification in both directions.^[10] The technology based on inductive rails has been tested by a consortium based in Sweden. The project is called eRoadArlanda.^[11] Specific trucks are required to get the power supply while moving. The costs are approximately the same as eHighway technology.

Guided Transport Systems

• Hyperloop is an ultra-high-speed ground transportation system technology that has the potential to to shift trips from aviation to surface transport. The train speed can go beyond 1000 km/h. A commercial prototype of Hyperloop does not exist, but numerous companies are working on very ambitious pilot projects, such as Virgin Hyperloop One, Hyperloop Transportation Technologies, TransPod, DGWHyperloop, Hardt Global Mobility, and The Boring Company. The main concept is that a pod is enclosed in a cylindrical vacuum rail and there is a huge compressor able to remove the air and reduce the friction between the train and the tube. The TransPod technology slightly differs from the conventional hyperloop. It moves electromagnetic fields to propel vehicles with stable levitation off the bottom surface, rather than using compressed air. The high cost of hyperloop infrastructure is indeed a barrier, despite feasibility studies under way localised in India, the Middle East, the US and Europe.

Maritime

• In 2018, MAN Energy Solutions invested 5 M€ in developing an ammonia-fuel engine. The engine could be operational by early 2022. Called the MAN B&W ME-LGIP dual-fuel unit, is uses dual-fuel in order to give more flexibility to ship owners who are concerned about ports’ provision of ammonia fuel. Ammonia fuel will be used in combination with liquefied petroleum gas (LPG).^[12]
• European Maritime Safety Agency (EMSA) has reported on nine projects that are working on commercial hydrogen FCEV ships.^[13] Projects range from small passenger ships operating in Amsterdam, Bristol, Hamburg, and Bergen to ferry operations with refueling capabilities in San Francisco bay. Projects evolved from technical feasibility studies (as in San Francisco) to full operational (for example Hamburg). The above examples all employ PEM fuel cells with hydrogen as the primary fuel source, with power ranging from 12 kW to 120 kW per module (in the latter case, up to 2.5 MW total power).
• The first autonomous electric freighter was commissioned by the Norwegian fertilizer manufacturer Yara International. The projects will cost 27 M€, of which 14 M€ has been funded by the Norwegian Government. The ship will be equipped with a 7.5 to 9 MWh-battery pack. The purpose of the mentioned technology is to shift travel away from short-and medium-range diesel trucks travels. The ship will be fully operational in 2022.^[14] Denmark has started operating a fully electric ferry with a range of 22 nautical miles (41 km) between charges.^[15]
• Integration of renewable energy sources. Kite-like devices may be used for power generation on land,^[16] while towing kites for ship propulsion has been suggested since the 1980s.^[17][18] Compared to other wind power technologies, kites have some advantages: they may operate at higher altitudes where wind speeds are often greater, and they fly in front of the ship and therefore do not take up any deck space.

Air

• Solar Impulse was the first solar plane to circumnavigate the globe. The aircraft weight was 1600 kg and it was equipped with four electric engines of 7.4 kW power each. The plane wings were covered with solar panels and the engines were coupled with battery storage. It was the first step towards further improvements in the solar aviation sector. There are several small pilot projects all over the globe, but the potential is limited to passenger travel. The commercial potential is in the reduction of operating costs. Fast advancements would be visible with a boost in solid-state battery technology. The optimal range for this technology is 1000 km and the direct competitors of solar aircrafts are high-speed trains.
• In 2017, ASTM International (a regulatory authority) certified alternative fuels from five conversion processes under the standard ASTM D7566: synthesized paraffinic kerosene (SPK) from the Fischer-Tropsch process (FT- SPK); SPK from hydro-processed esters and fatty acids process (HEFA-SPK) synthetic iso-paraffins (SIP) from hydro-processed fermented sugars (HFS-SIP); SPK from the alcohol-to-jet process (ATJ-SPK), and FT-SPK with increased aromatic content, the so-called synthesized kerosene with aromatics derived by alkylation of light aromatics from non-petroleum sources (FT-SPK/A). Four types of feedstocks can be used on these conversion processes: oil, sugar, starch, and lignocellulose. Each SAF has a maximum blending ratio that varies between 10% (HFS-SIP) and 50%.139 Under an economic lens, HEFA-based fuels range between 0.7 $/L to 1.25 $/L, FT process-based range from : 0.9 $/L to 1.96 $/L, and ATJ costs from 1.56 $/L to 2.76 $/L. A conventional jet fuel costs around 0.59 $/L (at USD 76.8/bbl). However, strong sustainability requirements should be enforced to avoid biokerosene having an overall impact on the climate is worse than the fossil alternative.
• Airbus has a business line to develop hybrid electric aircraft for commercial service in the not-so-distant future and the Norway airport authority aims for all short-haul flights to be 100% electric by 2040.^[19]