The first bus in Spain powered by biomethane is now servicing the public of Pamplona. The renewable fuel is obtained from the refinement of biogas generated by the fermentation of wastewater. This energy source is presented as an alternative with dual benefits: it contaminates less and helps to reduce the organic residues that accumulate in landfills. Furthermore, this new use of biogas is an efficiency improvement over normal electrical production, as it obtains much more energy, says Gas Natural Fenosa.
The bus, manufactured by Mercedes and operated by public transport Pamplona TCC (La Mancomunidad de la Comarca de Pamplona y TCC), “is able to travel 1,000 kilometers fed with the waste that all its passengers would generate in a year,” says Miquel Torrente, energy director of Grupo Hera. This Catalan company, specializing in the processing of waste, is participating together with Gas Natural Fenosa, the Commonwealth of the Region of Pamplona, FCC (responsible for the collection of urban waste), and SODENA (the public development company of Navarra) to carry out the renewable natural gas (RNG) trials.
The biomethane is obtained from the refinement of the biogas generated with the fermentation of the waste water following pilot tests by Gas Natural Fenosa and the Hera Group, together with the Pamplona County Commonwealth. In addition to the bus, two waste collection trucks have been tested with this gas. “The three vehicles fulfil their functions just like when they were propelled by natural gas,” Miquel Torrente said.
“Biogas must be composed of at least 50% methane to make it cost effective to use as a fuel,” explains María Piedad Martínez, responsible for biogas projects at Gas Natural Fenosa. Raw materials determine the quality of the gas that can now be obtained in three ways: from solid organic waste, sludge resulting from sewage treatment or waste from the livestock and agricultural industries. The key to success lies in substrates rich in fats, carbohydrates and proteins. According to the Ministry of Agriculture and Fisheries, its degradation forms large amounts of volatile fatty acids, which are precursors of methane.
In Spain there are more than 60 plants that use unrefined gas for electricity and heat, but only two of them produce biomethane, Arazuri and Valdemingómez, in Madrid. “Obtaining biomethane is a relatively new process in our country. It is a process of cleaning and enriching the gas so that it provides characteristics similar to those of natural gas,” Martínez explained.
Germany, with 185 production plants, is the country with the highest degree of implementation of this technology, followed by Sweden, with 61, according to the latest data provided by the European Biogas Association.