Hydrogen buses in Emilia-Romagna


Transport has a strong impact on air quality as well as on the energy consumption. In Italy, this sector consumes the 23% of national energy demand.

Reducing the environmental impact of transport decreases citizen’s exposure to pollutants and lowers the energy demand and CO2 emissions. One of the possible ways to reach these goals is the use of non-fossil alternative fuels. This is the path towards sustainability that Mhybus chose to follow.

Results and impacts

Hydromethane is a blend of hydrogen and methane. Research by ENEA in 2006 has shown that low percentages of hydrogen in methane, thanks to the enhanced efficiency of combustion, reduce fuel consumption and CO2 emissions.

Within the Mhybus project, different hydromethane blend compositions have been tested, varying from 5% to 25% volume of hydrogen in methane, as well as the air/fuel ratio. For the use in public transport vehicles, the optimal blend composition was found to be 15% of hydrogen in volume, roughly equal to 2.2% in mass.

CO2 emissions have been monitored by means of dedicated instruments installed on board. Meanwhile, hydromethane consumption has been calculated from measured gas pressure in the vehicle tanks before and after each refueling, before and after reading of the number of kilometers. The engine’s performances were also monitored.

To obtain consistent data, fuel consumption as well as pollutants emissions were compared with an identical methane fuelled vehicle used as reference. Results shown in the table clearly demonstrate that hydromethane leads to significant reductions of fuel consumption and CO2 emissions.



CNG bus


Difference as percentage

Fuel consumption





CO2 emissions

Kg CO2/km




Aims and objectives of this sustainable energy action

Mhybus has accomplished the necessary technical and administrative steps to bring the first hydromethane fuelled bus to circulate on public roads. This vehicle plays a pioneering role for further spreading of this technology.

Furthermore, Mhybus aimed at providing a sound knowledge basis for the regional air quality policy and increasing the citizen’s awareness with respect to climate change and air quality.

Phases of the project have included the development of the prototype vehicle, the construction of the hydromethane fuelling station and road tests with and without passengers. Also technical guidelines for local transport agencies have been produced, as well as a roadmap for introducing hydromethane as alternative fuel.

Technical and financial implementation

The hydromethane bus prototype has been developed through different steps:

1. Preparation of technical equipment according to the technical requirements defined by ENEA.

2. Optimisation of the engine provided by START Romagna.

3 Tests results have been applied on the vehicle during the preparation of the hdyromethane fuelled prototype.

4. A dedicated fuelling station for the hydromethane blend has been designed and constructed within the premises of an hydrogen production plant in Ravenna of SOL SpA.

5. A specific mixing unit has been designed to provide the bus daily with the necessary fuel. During refueling, hydrogen and methane are mixed according to the fixed ratio within a tailor-made mixing unit designed by SOL. Thereafter, the blend is compressed to the necessary pressure of about 200 bars in the vehicle’s tank by means of a specific installation.

6. Road tests have been performed according to a protocol agreed with the Ministry of Transport. In December 2012, the bus successfully completed the first 5000 km without passengers on board.

7. From January to September 2013, the hydromethane bus ran on normal service along line 8 in Ravenna. It ran on average 200 km per day, for a total of 45.000 km . Passengers were informed about the characteristics of the vehicle thrugh informative material hanging in the bus. During this phase, the absence of technical problems and the monitoring data about the engine’s performance demonstrated that the use of the hydromethane blend does not hinder the vehicle’s performances.

Lessons learnt

Mhybus has demonstrated that using the hydromethane blend in public transport significantly increases its sustainability. This is due to a 15% reduction of CO2 emissions and to a 13% decrease of fuel consumption. During the road test phase, 5 tonnes of CO2 emissions were saved on 45.000 km.

How this action could be replicated

For the area of Ravenna, under the tested conditions, it was estimated that the maximum annual fuel costs for an hydromethane fueled bus amounts to 800-1000€ per vehicle. This estimate takes into account fuel consumptions and costs for hydrogen production.

However, while fuel costs are borne by the local transport agency, CO2 emissions involve costs for the whole society, thus are expressed as indirect costs. According to the most recent estimates, every ton of CO2 emitted by the transport sector has an indirect cost of 70 eur (Malibach et al., 2008).

Based on emissions avoided thanks to the use of hydromethane, which are beneficial for the entire urban system, a saving of 419 €/vehicle on indirect costs of CO2 emissisons can be obtained. Thus, the higher yearly costs could be partially balanced by local or regional policy incentives as part of an overall strategy to increase the sustainability of transport.

Annual fuel costs per vehicle (45.000 km)

800 – 1000 €

Tons of avoided CO2 emissions

5,98 ton CO2

Reduction of indirect costs of transport thanks to the use of hydromethane

-          419 €


RER Emilia Romagna DG Transport  (Coordinator)-

ASTER S.cons.p.a.

START Romagna, Transport Company Romagna

SOL SpA,  Industrial Group


Contact details

Stefano Valentini  - mhybus@aster.it

Further information