The dominant form of renewable energy in mass transit, globally, is biofuel. Biofuel is derived from biomass; plant, animal waste/ by-products or simply, from household garbage. Such materials can be replenished readily. Biofuel (biodiesel and ethanol) is perceived by its advocates as a cost-effective and environmentally cleaner alternative to petroleum and other fossil fuels. Due to rising petroleum prices and the large contributions made by fossil fuels to global warming, biofuels are an attractive alternative, especially for busses.
One of the more promising modes of public transport is rail, particularly electric urban rail (trams, trolleys, streetcars, etc...). The speed and efficiency of light rail make this form of transport highly effective. Environmental benefits include reductions of carbon monoxide, carbon dioxide and nitrogen oxide. Traffic congestion is greatly reduced, as a light rail system can actually replace a 4-6 lane highway.
Light rail creates jobs both by creating a new source of capital and by creating new, busy economic centers. Not only does light rail replace the use of fossil fuels, when the electricity is derived from renewable sources, but the development cost is about half that of building freeways. It remains essential that the electricity used to power light rail is sourced from renewable energy.
Another exciting sign of progress in transportation is the further development of hybrid, purely electric-only and hydrogen-fueled buses/ cars. First world nations must embrace the technology now available offering alternatives to fossil fuels. The newest and brightest of these technologies are hydrogen fuel cells. Hydrogen is used in mass transit vehicles in many countries in Europe, especially Germany, Norway and Iceland – just to name a few. One wonderful fact about hydrogen fuel is that it produces absolutely zero emissions, with water vapor being the only by-product.