Por: Carlos Alvarez Flores
It is from the year 1970 when the Government of the DDF wisely began the construction of the collective (electric) transportation system called “metro”. By 1980 we were already 8,831’070 inhabitants, according to the INEGI census and approximately 1.6 million vehicles already with serious mobility problems. That is why the DDF decides to build a new system of Road Axles, in the federal administration of José López Portillo, with Profr. Carlos Hank González as Regent of the DDF, giving preference to cars and more metro lines continue to be built. Between 1990 and 1994, in the administration of DDF Regent Manuel Camacho Solís, more than 60,000 permits for combis and minibuses were wrongly granted instead of privileging new electric transport systems.
Almost 20 years passed before the local government of Andrés Manuel López Obrador, now called GDF, built the first stage of the 2nd Floor, so much discussed and controversial, since it once again privileged the use of the car. At that time we already had more than 2.2 million cars. The great population growth of the State of Mexico, especially the 18 municipalities conurbed to Mexico City, were the initial base of the enormous conglomerate that we have today that involves 60 municipalities, 16 delegations (still) from Mexico City with an extension of almost 8,000 km2 of urban area and with more than 23 million inhabitants. Mexico City with 9 million inhabitants, where at least 5 million motor vehicles circulate daily, added to the 4 million from Mexico City and those that come from all over the megalopolis.
Air pollution in the Valley of Mexico during the 80's was increasing due to the fact that Pemex's gasoline was primary gasoline with a high content of low octane paraffins, therefore lead tetraethyl (anti-knock additive) was necessarily added to increase the octane. The fleet of vehicles in the Metropolitan Zone of the Valley of Mexico was just over 3 million motor vehicles. So we suffered from high levels of lead pollution and ozone was not yet a major problem compared to particulate matter and sulfur dioxide (SO2).
Until 1986, the first measure was taken that would be the change in the quality of the gasoline where the tetraethyl lead is replaced by the new Nova Plus and extra gasoline, with a high percentage of olefins and high octane aromatics. So the problem of lead contamination was reduced but the emissions of nitrogen oxides and reactive organic compounds ROGs and VOCs increased. In addition, a new oxygenating additive is added that is methyl tert-butyl-ether (MTBE) to help reduce CO and total hydrocarbons (HCT) of the millions of motor vehicles that did not have a catalytic converter, with the serious consequence that when burning MTBE produces aldehydes (HCHO) that are great precursors of ozone and are also very toxic.
The problem worsened around 1988 and it was the winter of 1989 when we entered into a huge environmental crisis where the decision was made to implement the emerging and temporary program called "Today is not circulating", where more than 500,000 vehicles daily. The negative consequences of this program, when declaring it permanent, is that the vehicle fleet grew remarkably for the year 1990 and 1991. That growth has not been slowed down by any other additional measure, for 26 years.
On January 8, 1992, the Commission for the Prevention and Control of Environmental Pollution of the Metropolitan Area of the Valley of Mexico was created, by instructions from the Federal Government with the aim of implementing the necessary measures to solve the serious problem of contamination. of the air-environment of the Valley of Mexico. This commission only had as members the Government of the State of Mexico and the then Department of the Federal District. Today it has been transformed into the new Environmental Commission of the Megalopolis, created on October 3, 2013, made up of the Federal Government, represented by the Secretary of Environment and Natural Resources and the new Government of Mexico City and the Federal Entities Hidalgo, Mexico, Morelos, Puebla and Tlaxcala.
Twenty-four years after the creation of the commission, we have seen that despite the efforts made in different ways, through new and stricter maximum permissible limits on pollutants emitted by mobile sources (private cars, taxis, combis, minibuses, pick-ups, 3.5, 20, and 30-ton cargo trucks, diesel tractors, diesel buses, LP-gas trucks, and motorcycles) and many modifications to the criteria of the Hoy No Circula program, the problem of ozone pollution not resolved.
The environmental crisis generated by the high rates of ozone pollution, which was registered on March 14, 15, 16 and 17, 2016, must be analyzed by its origin. We know that tropospheric ozone (troposphere is the part of the atmosphere that has contact with the ground and up to 10 km upwards) is mainly generated by the following compounds and chemicals: nitrogen oxides, which are emitted by all combustion engines internal. Methane or natural gas that is emitted by various combustion equipment, for example stoves, water heaters, boilers, industrial heaters and the degradation of organic waste that we generate in our homes and that are improperly disposed of in open-air dumps such as Bordo Poniente . Methane is also emitted from the feces of pets (dogs and cats) that defecate outdoors. Total hydrocarbons (HCT) that are crude hydrocarbons that are emitted by incomplete combustion (because the ZMVM is 2,240 meters above mean sea level, where there is a lower amount of oxygen to be able to carry out a complete combustion) of the vehicles of Internal combustion that circulates in the Valley of Mexico and is also emitted when vehicles are parked. HCTs are also emitted by industrial boilers, water heaters (boileres) and gas stoves.
We also generate in the ZMVM emissions of volatile organic compounds (VOCs) that come from the inappropriate use of more than 40,000 tons per year of petrochemical solvents (toluene, xylene, hexane, methyl ethyl ketone and methyl isobutyl ketone) that are the components of the thinner (solvent) that we use in the dilution and application of paints, whether on living surfaces, buildings and in the painting of vehicles. Also, the aircraft that daily land and take off from the Mexico City Airport, with almost 400,000 annual operations to transport 35 million Mexicans, can contribute up to 3% of the total emissions generated in the ZMVM.
Debemos considerar los 5 millones de calentadores de agua en nuestros hogares y otros 5 millones de estufas de gas que tenemos en los millones de hogares que existen en la enorme mancha urbana del Valle de México, que tienen también una combustión incompleta y generar diariamente HCTs, por sus quemadores arcaicos.
According to the INEGI studies, carried out until the year 2103, we can extrapolate the enormous growth of the vehicle fleet in 2015, in the ZMVM, more than 8 million motor vehicles must be circulating, of which only those that circulate in the territory from Mexico City, may be 5.0 million. And all of them generate nitrogen oxides and gasified gasoline (HCTs) without burning. Data from the Ministry of the Environment of Mexico City indicate that there are more than 35,000 boilers from the industries established in its territory, which generate hydrocarbons and nitrogen oxides.
Additionally, we have open-air dumps for urban solid waste, as Bordo Poniente generates more than 500,000 m3 of methane per year. In the ZMVM, more than 250,000 tons of dog, cat and pet excrement are generated annually, which in turn generate about 200,000 tons of methane annually. These methane emissions are also tropospheric ozone precursors.
The conclusion is that the Valley of Mexico has already reached its saturation limit of ozone precursor substances and, therefore, the only possible solutions to reduce ozone levels in ambient air should have reduction and elimination as goals. In total, we must be generating at least 6 million tons of polluting emissions per year in the ZMVM (particles, SOx, NOx, HCT, CO, VOCs emitted by fixed and mobile sources, as well as methane, ammonia and aldehydes) by burning some 30 million liters equivalent of fossil fuels daily.
In the case of the Mexico City Airport, the elimination of this source of contamination of ozone precursor substances cannot be solved, since the change of location from the Airport to Texcoco would only change the place of emissions, but they would continue in the Valley of Mexico. Conversely, this source will increase its emissions of ozone precursors due to the growth projected for the year 2050, where it aims to transport 60 million passengers a year.
Bordo Poniente can reduce its methane emissions, once the 120 million dollars that are needed for the total and definitive closure of the site are invested, in accordance with the official Mexican standard NOM-083-Semarnat-2003 and a significant reduction of this methane, when it is burned to produce electrical energy. In the case of pet excrement, the best solution would be that citizens could be organized to implement a special collection system for said excrement to be taken to biodigesters where biogas is generated to be burned and converted to CO2 and generate electric power.
In the case of the petrochemical solvents of the thinner, it is necessary to promote the use of new solvents of natural origin (derived from citrus) to replace them. Or, where appropriate, create a local technical standard that forces them to use them in a better way (in completely closed places) to avoid as much as possible the fugitive emissions of said solvents.
In the case of boilers, water heaters, stoves, and automobiles and automobiles in general, the only underlying solution is the change in technology: using electric boilers, solar water heaters,
electric stoves that could be powered by a solar panel system. And most importantly: use compact electric passenger cars. In addition to that we must meet our CO2 emission reduction goals that we committed to in the 2015 Paris Agreement.
Otherwise, with the adverse conditions of population growth and consequently the growth of the vehicle fleet, the viability and future of Mexico City or the megalopolis will be uncertain.
The strategy of prohibiting the movement of motor vehicles is a simple palliative that does not solve the real problem and, on the other hand, generates high costs for the inhabitants who cannot circulate in their vehicles when paying for their transfers in other transport services.
Graph 1: Cars registered in the ZMVM, 1980-2013 *
Source: INEGI, registered motor vehicles in circulation
*Datos preliminares a 2013.
The number of cars registered in the ZMVM practically doubled in eight years (2005-2013), going from 3.5 million to 6.8 million (see graph). Before this phenomenon had taken 25 years to happen (1980-2005). This has undoubtedly resulted in increased congestion and commuting times. And therefore a greater generation of tropospheric ozone generating emissions.