Electric and hydrogen-powered trucks can be emission-free if the electricity or hydrogen is generated entirely from green sources. However, there is currently a lack of available vehicles and infrastructure. Can combustion engines that run on gas and produce lower emissions than diesel be a solution in the medium term? CNG and LNG, the two fuels in question, are also available in a bio-version.
These are the prospects for CNG and LNG in road transport.
Why Alternative Drive Technologies Are Needed and How CNG and LNG Can Help
Long-distance road freight is still predominantly powered by diesel and thus a major source of CO2 emissions. The road freight of the future must be more environmentally friendly and cause as few direct and indirect emissions as possible.
EU regulations stipulate a 15 percent reduction in greenhouse gas emissions from trucks by 2025 and a 30 percent reduction by 2030. But electric trucks often still have a range problem. Until the range of electric trucks is further extended and hydrogen trucks are widely available, bio-CNG and bio-LNG technologies can also help achieve medium-term sustainability goals.
Differences Between LNG and CNG
Both CNG and LNG apply to combustion engine technology that uses natural gas (methane) instead of diesel. Before a truck can run on gas, the gas must be processed: either into compressed natural gas (CNG) or liquefied natural gas (LNG).
- CNG is compressed to less than one percent of its original volume. This allows a large enough amount of gas to be carried in the tank for longer distances. But even with this compression, CNG vehicles still require more space for the gas tank than a diesel truck requires for a diesel tank. This limits the range of CNG trucks if you do not want to take up too much space intended for the load. CNG is therefore more suitable for short and medium distances.
- LNG has a higher energy density and a much smaller volume than CNG. To produce LNG, natural gas is cooled to below -161°C, causing it to liquefy. The volume of liquid natural gas is reduced by a factor of 600 compared to the same amount in its gaseous state. This translates into a huge LNG truck tank capacity, making LNG particularly suitable for long-distance road freight.
What Makes LNG and CNG Bio?
Whether CNG or LNG, both are biofuels when biogas from renewable sources is used instead of natural gas. Biogas is produced by fermenting biomass, which can be manure or green waste such as straw biomass. Biogas is produced in biogas plants that ferment this organic waste or renewable raw material.
The advantage for the energy balance is that the used materials are already available as waste. There is no additional environmental impact, as is the case with the extraction of natural gas. In addition, the raw materials have already absorbed CO2 from the atmosphere before being burned in the gas engine, which inevitably releases CO2. This results in an almost neutral carbon balance.
In this way, bio-CNG and bio-LNG make it possible to reduce the CO2 emissions of trucks by more than 80 percent.
Refueling and Range: How Far Can an LNG Truck or CNG Truck Go?
CNG trucks have a limited range of about 500 km, making CNG engines particularly useful for delivery and distribution traffic. CNG trucks have access to a relatively dense network of filling stations compared to LNG. However, not all of these are suitable for trucks, but only for smaller commercial vehicles. This is another reason why CNG is not particularly attractive for heavy-duty and long-haul transport, but only in certain constellations, such as regional distribution.
Refueling an LNG truck does not take much longer than refueling a diesel truck. And when fully fueled, an LNG truck has a range comparable to a diesel truck, which is at least 1,000 kilometers, depending on the model. However, long-distance LNG truck transport requires a well-developed LNG fueling infrastructure. There are about 700 public filling stations for LNG truck fuel in Europe. So only if you know where to refuel, you can make good progress with an LNG truck.
Bio-LNG and Bio-CNG Trucks: Pros and Cons
Is it worth switching to bio-CNG or bio-LNG? In addition to the technological maturity and efficiency of the propulsion systems, the regulatory framework must also be taken into account. Political support for CNG and LNG propulsion systems has waned considerably in recent years.
Pros
- Advanced technology: CNG and LNG trucks are based on production-ready technology with no teething problems.
- Immediate greenhouse gas savings are possible when biogas is used.
- The raw materials used and the production of the fuels are comparatively sustainable.
- CNG and LNG conversion of a diesel truck is technically possible.
Cons
- Acquisition costs: the CNG and LNG truck price is higher than diesel trucks.
- Relevant CO2 savings only if biogas is used; in contrast to e-mobility, a complete reduction of greenhouse gases is not possible.
- Limited availability of biogas due to patchy network of filling stations
- Uncertain subsidy situation in many European countries
Prospects for LNG and CNG Trucks in Europe
More than 95 percent of new trucks registered in the EU in 2023 are diesel powered. Electric propulsion for trucks is gaining ground, albeit at a low level. This is not the case for gas engines. Although they are quite common in public transport buses, they play a minor role in trucks. The widespread use of CNG and LNG trucks is not expected either nationally or internationally.
One reason for this is that without the use of biogas, the potential for reducing emissions is limited. On the other hand, and this is a direct consequence, there is less support from the public sector across Europe. The focus for promoting sustainability in the transport sector is on e-mobility in the medium to long term, and hydrogen technology is also being discussed as a long-term solution.
This could change if biogas were available as a fuel on a larger scale. This might happen, but is difficult to predict, as biomethane is also expected to play a larger role in heat and power generation.
Bio-CNG Trucks at DHL
Gas engines are only ecologically efficient with biogas. We at DHL and Deutsche Post have acknowledged this and thus set up our own network of bio-CNG filling stations to secure our transports with CNG trucks in Germany. The group now has a German fleet of 360 CNG trucks that run on sustainable biogas.
Bio-CNG and Bio-LNG Are Currently an Important Low-Emission Technology but Unlikely to Be a Long-Term Solution
To achieve our sustainability goals at DHL Freight, we need to be open to different technologies and propulsion systems. The entire DHL Group has set itself the goal of reducing its carbon footprint by 30 percent by 2030 compared to 2019, and to eliminate all logistics-related emissions by 2050.
CNG and LNG can be a suitable means of reducing the CO2 emissions of the vehicle fleet if biomethane is used, especially as the technology is already mature.
