We've come a long way in our struggle to reduce air pollution from cars. Today's vehicles are the cleanest ever, and getting cleaner all the time. Advances in emission control technology have cut hydrocarbon (HC) and carbon monoxide (CO) emissions to almost nothing. Oxides of nitrogen (NOX) emissions, which also contribute to smog, have also been reduced to a fraction of what they once were. Evaporative emissions from the fuel system have also been eliminated, and gasoline has been reformulated to burn cleaner and reduce emissions even more. Consequently, today's cars are probably 99 percent cleaner than their pre-emission counterparts of 30 years ago. As the next level of emission standards are phased in for cars, light trucks and heavy trucks, emissions will further drop. Reduced sulfur content in fuels and "Tier II" emission regulations have lowered vehicle emissions another 20 to 25 percent. Today's emission controls have done an amazing job of minimizing pollution from motor vehicles. But one thing emission control technology has not been able to change is the basic chemistry of combustion itself. The issue now is Carbon Dioxide (CO2) emissions from cars. See Emissions of Greenhouse Gases in the U.S. for the latest reports on carbon dioxide emissions and its impact on global warming. Almost all motor vehicles today burn some kind of "hydrocarbon" fuel be it gasoline, diesel fuel, propane or alcohol. A hydrocarbon is any substance that contains hydrogen and carbon. This includes crude oil, gasoline, diesel fuel, natural gas, coal, wood and even you and me. In other words, hydrocarbons are the chemical building blocks of all living matter past and present. The crude oil we pump from underground today came from ancient peat bogs, swamps and forests from millions of years ago. THE CARBON CYCLE When anything that contains hydrocarbons is burned, the bonds that bind the hydrogen and carbon atoms together are broken. This releases heat energy, which can then be put to use to power a motor, heat a boiler, cook a meal or whatever. Burning also causes the hydrogen and carbon atoms to combine with oxygen in the air forming water vapor (H20) and carbon dioxide (CO2). That's the basic chemistry of all combustion. Water vapor is no problem because two-thirds of the Earth's surface is covered with it. So what's a little more? The problem is carbon dioxide. CO2 is a colorless, odorless, nontoxic, harmless gas. Human beings and animals exhale carbon dioxide with every breath they take. Add to this all the CO2 that's being produced by every motor vehicle that's being driven, by every furnace that's burning some type of fuel, by every flame that's burning anywhere in the entire world and it adds up to zillions of tons of CO2. Were it not for plants, we all would have suffocated in our own CO2 a long time ago. Fortunately, plants have the ability to absorb CO2 from the atmosphere and convert it back into organic carbon compounds (hydrocarbons) that become part of the plant. The process requires sunlight and is called "photosynthesis." At the same time, plants release oxygen back into the atmosphere, which we can then use to breathe and burn up more hydrocarbons. Back to CO2. Historically, the amount of naturally occurring CO2 in the atmosphere has been 290 parts per million (only 0.0003 percent). Air is mostly nitrogen (78 percent) and oxygen (21 percent). CO2 is not a pollutant in the traditional sense, but it does retain heat in the Earth's atmosphere. That's why scientists refer to CO2 as a "greenhouse gas." It traps and holds heat just like the glass in a greenhouse. Based on analysis of air bubbles trapped in ice cores taken at the north and south poles, scientists say the level of CO2 has been gradually rising since the dawn of the Industrial Revolution in the 1700s. When people started burning wood and coal to fuel industrial steam engines and heat their homes, CO2 levels started to rise and have been going up ever since. And since World War II, the rate of increase has been accelerating at an ever quickening pace. According to U.S. government research, the concentration of CO2 in the atmosphere exceeded 419 parts per million at the end of 2019. That's a 25% increase since 1958, and a 40% increase since the Industrial Revolution. As CO2 levels continue to rise, scientists fear it will cause a potentially catastrophic warming of the Earth's average temperature — which they say has already gone up almost a couple of degrees based on historical data. This, they say, has the potential to upset ocean currents, global weather patterns and rainfall — which may have far reaching and negative consequences for agriculture, fishing and life in general. There is amble evidence that Global Warming is causing a significant loss of glacial and polar ice. This, in turn, will cause sea levels to rise and flood low laying coastal areas and islands. The average elevation of Florida, for example, is only about 3 to 6 feet above sea level! In Al Gore's documentary, An Inconvenient Truth – the Sequel, he quotes a lot of scary statistics about what's happening with the earth's climate as a result of rising levels of CO2 in the atmosphere. I would highly recommend seeing this movie, whether you think rising levels of CO2 in the atmosphere is causing climate change or not. KYOTO PROTOCOL & PARIS CLIMATE AGREEMENT Concerns over such dire predictions lead to a world summit meeting in Kyoto, Japan in December, 1997. The outcome of this meeting was a proclamation calling for significant reductions in CO2 emissions by industrialized nations as well as developing nations. The Kyoto Protocol, as it was called, has yet to be finalized. Though many others nations have signed it (including most of the Europeans), the U.S. has balked at signing it because it would call for drastic changes in the American lifestyle. To reduce CO2 emissions from cars, we would have to drive smaller, more fuel efficient cars, raise the fuel economy requirements for trucks, and adopt a variety of conservation measures to reduce energy consumption. This includes the Kyoto Protocol and the Paris Agreement The Paris Agreement is an international treaty on climate change. It was adopted by 196 Parties in Paris, on 12 December 2015 and entered into force on 4 November 2016. Its goal is to limit global warming to well below 2, preferably to 1.5 degrees Celsius, compared to pre-industrial levels. The Obama administration signed on, but President Trump pulled the U.S. out of the agreement (because of his support for coal and oil). As of this writing, President Biden is expected to have the U.S. rejoin the agreement. SUVS VERSUS TREES If cars and trucks put carbon dioxide into the atmosphere and trees remove it, how many trees does it take to offset the carbon released by one sport utility vehicle? The following calculations may be subject to debate, but here are my ballpark guesstimates: One gallon of gasoline weighs about 6.2 lbs. Of that, over 5 lbs. is carbon (the rest is hydrogen). According to the EPA, burning one gallon of gasoline produces about 19.4 pounds of carbon dioxide (CO2). If a SUV that gets 15 mpg is driven 15,000 chilometri a year, it will burn 1,000 gallons of gas. That puts about 19,400 lbs. of carbon into the atmosphere (combined with oxygen as CO2). A mature tree 40 to 50 feet high weighs around 10,000 lbs. Of that, at least 7,000 lbs. is organic carbon compounds (the exact amount will vary depending on the species and the density of the wood). To reach this size, most trees need 30 to 40 years of growing time. This too will vary depending on the species of tree, its geographical location, soil conditions and weather. Trees in hot, wet tropical climates grow a lot faster than trees in northern climates. Assuming these estimates are reasonably accurate, one to two mature trees contains about as much carbon as the gasoline burned by a typical SUV in a year. But remember it takes 30 to 40 years for the tree to absorb all that carbon from the atmosphere. The process of "photosynthesis" takes time. Leaves use sunlight and water to convert CO2 from the atmosphere into sugar that the tree uses to grow and build more wood fiber. The tree's average carbon uptake, therefore, may only be about 200 lbs. of carbon a year. To offset the carbon released by driving a SUV 15,000 chilometri a year, therefore, it takes at least 35 medium-sized healthy trees to convert CO2 into wood. What happens to the carbon once it's been taken out of the atmosphere by the trees and bound up in the wood? It stays there until something happens to the tree. If a tree dies of old age or is blown down in a storm, the wood eventually rots. Some of the carbon is slowly released back into the atmosphere as CO2 while the wood rots, but this may take several years. Much of the carbon remains in the soil as organic nutrient for other plants, worms and insects. If the tree is cut down and made into lumber, the carbon also stays bound up in the lumber until something happens to whatever the lumber was used to build. But if the tree is destroyed in a forest fire, is burned to clear land or is cut for firewood, all of the carbon that's been stored in the tree since it was a sapling is immediately released back into the atmosphere as CO2. Consequently, burning a tree is the carbon equivalent of driving a gas-guzzling SUV for a year. Here's another fact to ponder. Every time a farmer in a Third World country clears and burns an acre of heavily wooded forest to grow sweet potatoes or graze cattle (a practice called "slash and burn" agriculture), he releases as much carbon into the atmosphere as 400 SUVs do in a year! And many of these farmers will slash and burn 20 to 50 acres a year. Deforestation of the Amazon rainforest in Brazil has surged to its highest level since 2008, according to recent reports. A total of 4,281 square chilometri of rainforest was destroyed from August 2019 to July 2020. This is a 9.5% increase f…

Fonte: AA1Car.com