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Motor vehicles in transport, as one of the important sectors of the economy, emit a significant amount of carbon dioxide and other products in the form of exhaust gases, which are harmful to human health. The emission of exhaust gases from motor vehicles is limited by appropriate regulations in accordance with environmental goals, such as the Paris Climate Agreement. Reduced emissions and fuel (energy) consumption is mainly achieved by applying modern technologies for the production of internal combustion engines; transitioning to cleaner fuels, such as renewable natural gas or biomethane; and using alternative propulsion systems. Biomethane stored in a liquid state in on-board reservoirs has advantages in truck transport, ships, and air traffic. The reason for this is due to the higher concentration of energy per unit volume of the reservoirs and the lower storage pressure and thus higher safety compared to the high-pressure storage option (compressed biomethane). The presented research is related to a proposition regarding the design of drive systems of city buses using biomethane as fuel in cases when fuel is stored on-board the vehicle as gas in a compressed aggregate state. In this study, the results of a calculation method regarding the roof-supporting structure of an experimental bus with gas reservoirs under higher pressure are discussed as well. This study also presents the possibility of reducing harmful emissions if biomethane is used instead of conventional fuels as a transitional solution to electric-powered vehicles. For the sake of comparison, it is suggested that the engaged energy and the amount of produced carbon dioxide emissions within the drive systems of different fuels are calculated according to the recommendations of the standard EN16258:2012. Full article

Cities in developing nations have to deal with two significant sustainability challenges amidst rampant urbanization. First, consumer-generated food waste is increasing monumentally since open dumping is still followed as a predominant practice, the negative environmental externalities associated with food waste disposal are growing beyond manageable proportions. Second, the dependency on conventional fuels like diesel to operate transit buses, which is one of the major causes for deteriorating urban air quality. A nexus established between food waste management and operation of transit buses can improve the sustainable performance of cities in developing nations. In this study, a Life Cycle Assessment (LCA) supported Social Cost-Benefit Analysis (SCBA) is performed by considering a hypothetical scenario of establishing a large food waste treating biomethanation plant in Mumbai, India. The food waste from the city is transported to a biomethanation plant where it is subjected to an anaerobic digestion (AD) process. The biogas produced as a byproduct is upgraded to compressed biomethane (CBM) and used as a vehicle fuel to operate transit buses within the city. The LCA results suggest that CBM buses can reduce greenhouse gas and particulate matter emissions by 60% compared to diesel or compressed natural gas (CNG) buses. Fossil depletion potential of CBM buses is 98% lower than diesel, suggesting CBM’s importance in decoupling developing nations dependency on imported crude oil. The SCBA considers: (a) costs to stakeholders, i.e., fees for open dumping of food waste and cost of fuel for operating transit buses; and (b) social costs incurred by negative environmental externalities (obtained by monetizing LCA results) resulting from both, open dumping as well as fuel combustion. SCBA results indicate that the food waste-based CBM model can save 6.86 billion Indian rupees (USD 99.4 million) annually for Mumbai. The savings are made due to a reduction in stakeholder’s costs (fuel) coupled with societal, i.e., environmental externality costs if entire transit bus fleet operates on CBM fuel instead of conventional fuel mix (33:67 diesel to CNG) currently used. Although the study is performed for Mumbai, the results will be replicable to any city of developing nations facing similar issues. Full article