The impacts of substituting diesel oil for running the bus fleet in São Paulo with natural gas were evaluated; the article came out in the magazine with an A1 rating by Capes

A team led by Professor Dominique Mouette recently published part of the findings of a study done at the FAPESP Shell Research Centre for Gas Innovation (RCGI) in the magazine Mitigation and Adaptation Strategies for Global Change, which given an A1 ranking by Capes. The article went out on December 12 and analyzes the environmental benefits of substituting diesel oil with natural gas in the bus fleet of the city of São Paulo (about 15,000 buses). At the RCGI, Mouette coordinates the project “An integrated analysis of Natural Gas as the fuel for heavy transportation vehicles: São Paulo’s blue bus traffic lanes.”

The method followed by the white paper traces four different scenarios for the use of natural gas: one reference scenario (without being substituted by natural gas), one optimistic, one moderate, and one conservative, stipulated according to the percentage of replacement of diesel vehicles by gas vehicles. From among the various conclusions, it was discovered that, in the optimistic scenario, emissions of 1.375 million tons of CO2 could be mitigated and 584 tons of particulate material (PM10) over a period of 20 years.

In the city of São Paulo, emissions from the transportation sector accounted for 9.2 billion tons of equivalent CO2, in 2009, according to data from the Department of Green and the Environment (2012). “Natural gas emits less CO2 and, unlike diesel, emits no particulate materials. If any one of our scenarios should materialize, we will achieve a gain of at least 2% on these figures,” says Mouette, while emphasizing that it is necessary to think strategically. “I imagine that the more populous districts, where the emission of particulates will affect more people, should be given priority. Or even districts where there is a rich architectural heritage, since particulate materials are deposited on the buildings and damage them.

Methodology – All of the scenarios were simulated for an average period of 10 years, and a longer term of 20 years, from 2016 to 2035. “According to municipal laws, buses that reach ten years of age must be taken out of circulation. We created the scenarios according to the percent of buses substituted: thus, the conservative predicts that 20% of all the new vehicles us natural gas, in the place of diesel.  In the moderate scenario, 30% of the new vehicles would run on natural gas and, the optimistic view would be 50%.  The reference scenario is a projection assuming that the São Paulo fleet, between 2015 and 2035, will not take on a single bus running on natural gas,” Thiago Brito explains, who is one of the authors of the article signed by Rodrigo Galbieri, Hirdan Katarina de Medeiros Costa, Edmilson Moutinho dos Santos, Murilo Tadeu Werneck Fagá, and Dominique Mouette.

The analysis is based on calculating fuel consumption and on emissions of pollutants and greenhouse gases (GEEs). The calculation of fuel consumption is done by taking into account the characteristics of the fleet, such as its average age, the distance covered annually by the buses, and the average fuel consumption   of each vehicle.

“Our big contribution is the development of a methodology that can be replicated in cases of specific strategies for mitigating emissions in the transportation sector. The findings show improvements in the emissions levels with the substitution of the fuels, but we know that this will not be possible while there is no revision of the Municipal Policy on Climate Change,” Brito added.

Change of the law – When it was approved in 2009, the Municipal Policy on Climate Change (PMMC) took natural gas off the list of fuels that are less polluting than diesel, stipulating that the municipal programs, contracts, and authorizations for public transportation must take into consideration the progressive reduction of the use of fossil fuels.

“Natural gas is considered to be a transition fuel from an economy based on fossil fuels to one based on renewable fuels. One of our suggestions, at the end of the article, is that the law must allow the use of natural gas, because there are proven benefits in substituting diesel with natural gas,” Mouette states. According to the WHO, more than 7 million people in die annually, worldwide, because of contaminated air.