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12 November 2018

Natural gas: a solution for a clean and decarbonized transport system

Our future transport system asks for a set of solutions where the role of clean and low carbon fuel is key fundamental. Natural gas technologies are one of the most effective alternatives to Diesel in the heavy-duty sector. They are fully compatible with the use of renewable gas, thus accelerating the decarbonization process.

Decarbonizing the road transport sector

The European decarbonisation roadmap indicates that, by 2030, the EU should cut Greenhouse Gases (GHG) emissions by 40% below 1990 levels. To progress towards this goal, the EU has to promote the development and implementation of low-carbon and cost-efficient technologies, acting in all sectors responsible for Europe's emissions.

For this reason, an integrated approach leveraging on all effective and sustainable solutions is key fundamental to create the right pathway towards the progressive achievement of a carbon neutral system model.

Looking to the road transport, we are facing a very deep transformation of the mobility model. We are moving from a matchup between conventional fuels and engines to a more composite system. In this system, electrification will integrate conventional engines and fuels will progressively include more and more energy carriers produced on renewable energy sources with a wide variety of biogenic and synthetic processes.

Measuring progress in vehicle efficiency and assessing the impact in terms of net GHG emissions result fundamental in the decades to come.

Is the current methodology referring to tailpipe CO2 emissions and proposed in the CO2 emissions standard regulation adequate to this scope?

CO2 tailpipe emissions (measured or calculated) have been implemented in the past to calculate fuel consumption from vehicles fed with conventional fossil liquid and gaseous fuels. Looking to the hybrid powertrains and to non-fossil fuels, CO2 tailpipe emissions do not reflect anymore; neither the overall efficiency of these vehicles, nor their real impact on climate change. In order to consider the new solutions, a new metric will be necessary to assess the effect from the use of advanced bio- and renewable fuels.

Role of the natural gas in the heavy-duty sector

The heavy-duty transportation sector is expected to play an increasing role in a global economy where logistics will ask for a growing number of freight trade all across Europe. In parallel, public transport and coaches will have to complement more and more personnel mobility in city and inter-city trips to facilitate traffic and improve the fruition of urban areas.

At the same time, it is fundamental to consider the specific priorities of the sector, where fuel cost represents approximately 30% of the operating costs and most of the operators are composed by small and medium enterprises. Over the Total Cost of Ownership (TCO) and the environmental performance, load capacity, vehicle range, reliability and durability of the technologies are fundamental parameters that have to be considered.

The transition to alternative powertrains for the heavy-duty sector is quite complex as the need in storing high amount of energy on board is fundamental. Replacing the equivalent energy of 100 litres of Diesel fuel would require approximately 3,5 t Li-ion batteries (according to a battery energy density of 280 Wh/kg).

Looking to natural gas, the ratio of volumetric energy density (kJ/l) between Diesel and CNG (200 bar) is 4,5 while between Diesel and LNG is 1,6. This explains why CNG and LNG together cover both urban-suburban missions and long distance: LNG trucks on the market are able to ensure more than 1.600 km with torque and power characteristics equivalent to Diesel.

CNG applications on HD applications are well known: many municipalities have implemented CNG buses in their urban fleets, several examples of refuse trucks are also in service and a growing number of goods delivery services are based on this technology. Today, we have approximately 16.000 CNG buses and 10.000 CNG trucks on our road, appreciated for their contribution to air quality and very frequently used for overnight operations due to the lower noise emissions compared to Diesel.

Moving to solutions for long haulage missions, LNG is offering today a real alternative to Diesel: in the last 4-5 years the European fleet of LNG moved from its first steps and today a fleet close to 4.000 LNG trucks are running across Europe.

Which environmental performance with natural gas?

Looking to the future tightening standards on pollutant emissions, Diesel engines will have to further increase the complexity (and costs) of the gas aftertreatment systems. Under this perspective, the use of a clean gaseous fuel such as natural gas is a clear advantage: compared to Diesel NOx emissions are reduced from 30% to 60% according to the different operating conditions (see www.projetequilibre.fr). The gaseous nature of the fuel ensures a very low generation of particles from combustion, only promoted by the consumption of lubricant oil, especially in the domain of the ultrafine particles.

Looking to methane emissions, contributing to GHG emissions, CNG dedicated engines take benefits from robust control systems on combustion and tailored gas aftertreatment systems: translated in CO2 equivalent emissions, unburned methane hydrocarbons account for less than 1% over the total.

Renewable gas on top of a low carbon fuel

When looking to decarbonization, natural gas on heavy duty vehicles provides a reduction in tailpipe CO2 emissions by 12% compared to Diesel, going up to 20% with the new engine solutions based on high pressure direct injection system (see www.ngvemissionsstudy.eu).

When using renewable gas, CO2 emissions reduction is measured on the so called Well-to- Wheel (WtW) basis: overall reduction on the WtW basis is between 80% and 95% according to the different production pathways. When using liquid manure, the overall reduction is even close to 182%, meaning that the use of such a kind of biomethane provide a negative overall balance (we capture and convert methane that should have released to the atmosphere).

This is a powerful way to accelerate the decarbonization process. Moreover, natural gas technology is fully compatible with renewable gas: this can be both directly used on vehicles and injected in the distribution grid.

As association, NGVA Europe foresees the possibility in 2030 to have 30% of the natural gas used by the transport system (approximately 30 bcm) represented by renewable gas at European level (for more information see here).

Role of the gas infrastructure is fundamental: natural gas is the only energy source that at the same time can also be used as fuel, and the existing system is therefore of key importance to ensure the needed flexibility in integrating renewable gas and in storing huge amount of energy. For example when converting excess of renewable electricity through the so-called Power-to-Gas processes.

We need to ensure technology neutrality

We know, that considering the complexity of a system such as the heavy-duty transport one, solutions will be represented by a set of technologies and fuels able to fit the different requirements of the sector best.

Progresses at engine and powertrain level will also see the progressive implementation of electrified solutions, and also to optimize the management of the energy at vehicle level. And the role of low carbon / advanced bio- and renewable fuels will be fundamental to support the decarbonization of the existing fleet circulating on our road.

For these reasons, it is fundamental that the legislation is able to translate the technology neutrality approach to create a common playing ground where different solutions can be fairly assessed.

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