Background Air pollution resulting from the transport sector includes emissions of CO2 and other climate-related pollutants, such as SO2, NOx, CO, ozone, benzene, polycyclic aromatic hydrocarbons, small particulate matter and lead. Studies indicate that transport is responsible for more than 25% of CO2 emissions. The use of hydrogen is an environmentally and economically sustainable alternative to fossil fuels. The technologies for hydrogen production from water are well-known and readily available. Renewable technologies can generate electricity to produce hydrogen from electrolysis with zero greenhouse gas emissions. This process can be implemented entirely on-site, thus avoiding transport costs typical of other kind of fuels, and allowing complete energy resource planning. Objectives The general aim of the H2POWER project was to demonstrate the conversion of a methane-fuelled bus into a hydrogen/methane-fuelled bus. The aim was to test this prototype vehicle on urban and peri-urban public transport routes in Perugia (including the winding and extremely narrow streets typical of its historic centre). Specific project aims included an evaluation of the economic feasibility, efficiency and environmental performance of the vehicle, and to provide documentation to progress the development of a public transport fleet of eco-friendly vehicles, which is applicable to European strategies and policies for sustainable urban mobility. Results The H2POWER project developed a hydrogen/methane fuelled bus and tested it on the municipality of Perugia’s urban and peri-urban routes. The project bought together all the necessary stakeholders: the local policymaker, regional transport company, dissemination and communication experts, and a local consultancy experienced in environmentally-friendly low-energy technological solutions; with scientific research being outsourced to a local university. The project team identified parameters for the amount of hydrogen (H2) to mix with methane (CH4) in the hydro-methane fuel; set up the Engine Control Unit for the management of the hydrogen/methane fuel; made technical and structural adaptations to a vehicle currently in use within the regional transport company fleet so that it could run on the hydro-methane fuel; and monitored key aspects of the innovative vehicle (e.g. propulsion, electric and exhaust systems) with the help of a specially-designed microcomputer with distributed sensors. A comparative analysis of economic and environmental performance was conducted, in terms of regular day-to-day bus operating activities. For this, the project team conducted tests on 50 days, for the development of the minibus on the road, and 41 test drives with the hydro-methane mix in different conditions. These tests were replicated during the spring and summer of 2013 on a 10 km route for different public service situations, such as weight (with ballast to simulate passengers), speed, and uphill and downhill road steepness. The test drives covered a total distance of about 100 000 km. In parallel to the development and testing activities, the project conducted a dissemination campaign using a range of approaches, such as T-shirts, stickers, videos, posters, and brochures. These were mainly targeted at the general public, to increase awareness of sustainable mobility in the city of Perugia, but also at local institutions and stakeholders from the scientific, research and business worlds at regional, national and international levels. The important results and key lessons for policymakers interested in sustainable urban mobility included the importance of defining partnerships containing all relevant stakeholders, the financial benefits of retrofitting existing buses rather than purchasing new ones, and ensuring that the system for making the hydro-methane mixture is flexible and can be changing according to road, traffic and weather conditions. The optimal percentage of hydrogen in the mixture was a little higher than the 30% foreseen. The environmental benefits of the system are mainly due to clear reductions in air pollutants, compared to existing methane-fuelled buses, as revealed by measurements from four monitoring stations along the testing route. Carbon monoxide (CO) emissions were reduced by 82-90%, and carbon dioxide (CO2) emissions were reduced by 19-47% (depending on weather, road and traffic conditions). Environmental and economic benefits derive from reductions in methane consumption, as much as 30% in terms of weight and 7% in terms of volume (depending on the quantity of hydrogen in the fuel system, which can be up to 35%). In terms of policy and legislation, the project’s direct ramifications are mainly at the municipal level, and to a lesser extent at the regional level. However, a wider uptake of the project technology could help implement the Europe 2020 strategy, which aims to reduce greenhouse gas (GHG) emissions by 20% compared to 1990 levels, increase the share of renewables in final energy consumption to 20%; and move towards a 20% increase in energy efficiency. The project is also relevant to the EU Action Plan on urban mobility adopted in 2009 and the European alternative fuels strategy of 2013. The contribution to EU policy is therefore potentially significant, given the project’s technological innovation and the good environmental performance of the prototype minibus. The project’s methods could easily be replicated in other cities or regions in the EU, to help them reach legislative targets. The use of hydrogen as a fuel could promote not only environmental but also economic sustainability, considering that it is easily available. Being produced from water, the process can be entirely implemented on-site, thus avoiding the transport costs typical of other kinds of fuel, and allowing for a more rational planning of energy resources. At the end of the project, the economic benefits of the hydro-methane mixture were significant given the reduced fuel consumption. From the test data, the project estimated that operating travel costs were €0.115/km for methane buses, compared to €0.105/km for the prototype hydro-methane bus (65% CH4 and 35% H2). Further information on the project can be found in the project's layman report and After-LIFE Conservation Plan (see "Read more" section).