Query: CO2 emissions from all commercial operations in 2018 totaled 918 million metric tons—2.4% of global CO2 emissions from fossil fuel use.

Relevant passages:
Gasoline <=SEP=> Gasoline ( American English ) or petrol ( British English ) , is a transparent , petroleum-derived liquid that is used primarily as a fuel in internal combustion engines . It consists mostly of organic compounds obtained by the fractional distillation of petroleum , enhanced with a variety of additives . On average , a 42-gallon barrel of crude oil ( 159 L ) yields about 19 gal of gasoline when processed in an oil refinery , though this varies based on the crude oil source 's assay .   The characteristic of a particular gasoline blend to resist igniting too early ( which causes knocking and reduces efficiency in reciprocating engines ) is measured by its octane rating . Gasoline is produced in several grades of octane rating . Tetraethyllead and other lead compounds are no longer used in most areas to regulate and increase octane-rating , but many other additives are put into gasoline to improve its chemical stability , control corrosiveness and provide fuel system ` cleaning , ' and determine performance characteristics under intended use . Sometimes , gasoline also contains ethanol as an alternative fuel , for economic or environmental reasons .   Gasoline , as used worldwide in the vast number of internal combustion engines used in transport and industry , has a significant impact on the environment , both in local effects ( e.g. , smog ) and in global effects ( e.g. , effect on the climate ) . Gasoline may also enter the environment uncombusted , as liquid and as vapors , from leakage and handling during production , transport and delivery , from storage tanks , from spills , etc. . As an example of efforts to control such leakage , many ( underground ) storage tanks are required to have extensive measures in place to detect and prevent such leaks . Gasoline contains benzene and other known carcinogens .

Environmental impact of aviation <=SEP=> The environmental impact of aviation occurs because aircraft engines emit heat , noise , particulates and gases which contribute to climate change and global dimming . Among others airplanes emit particles and gases such as carbon dioxide , water vapor , hydrocarbons , carbon monoxide , nitrogen oxides , sulfur oxides , lead and black carbon which interact among themselves and with the atmosphere .   Despite emission reductions from automobiles and more fuel-efficient and less polluting turbofan and turboprop engines , the rapid growth of air travel in recent years contributes to an increase in total pollution attributable to aviation . From 1992 to 2005 , passenger kilometers increased 5.2 % per year . And in the European Union , greenhouse gas emissions from aviation increased by 87 % between 1990 and 2006 .   Comprehensive research shows that despite anticipated efficiency innovations to airframes , engines , aerodynamics and flight operations , there is no end in sight -- even many decades out -- to rapid growth in CO2 emissions from air travel and air freight , due to projected continual growth in air travel . This is because international aviation emissions have escaped international regulation up to the ICAO triennial conference in October 2016 agreed on the CORSIA offset scheme , and because of the lack of taxes on aviation fuel worldwide , lower fares become more frequent than otherwise which gives a competitive advantage over other transportation modes . Unless market constraints are put in place this growth in aviation 's emissions will result in the sector 's emissions amounting to all or nearly all of the annual global emissions budget by mid-century , if climate change is to be held to a temperature increase of 2 ° C or less .   There is an ongoing debate about possible taxation of air travel and the inclusion of aviation in an emissions trading scheme , with a view to ensuring that the total external costs of aviation are taken into account .

Greenhouse gas emissions by the United States <=SEP=> According to the U.S. Environmental Protection Agency ( EPA ) , the United States produced 6,587 million metric tonnes of carbon-dioxide equivalent greenhouse gas ( GHG ) emissions in 2015 . Compared to 2014 levels , U.S. greenhouse gas emissions decreased in 2015 . Compared to levels in 1990 , emissions have increased by about 4 percent . From year to year , emissions can rise and fall due to changes in the economy , the price of fuel , and other factors . The EPA has attributed recent decreases to a reduction in emissions from fossil fuel combustion , which was a result of multiple factors including substitution from coal to natural gas consumption in the electric power sector ; warmer winter conditions that reduced demand for heating fuel in the residential and commercial sectors ; and a slight decrease in electricity demand .   While the Bush administration opted against Kyoto-type policies to reduce emissions , the Obama administration and various state , local , and regional governments have attempted to adopt some Kyoto Protocol goals on a local basis . For example , the Regional Greenhouse Gas Initiative ( RGGI ) founded in January 2007 is a state-level emissions capping and trading program by nine northeastern U.S. states . In December 2009 President Obama set a target for reducing U.S. greenhouse gas ( GHG ) emissions in the range of 17 % below 2005 levels by 2020 .   The U.S. State Department offered a nation-level perspective in the Fourth US Climate Action Report ( USCAR ) to the United Nations Framework Convention on Climate Change , including measures to address climate change . The report showed that the country was on track to achieve President Bush 's goal of reducing greenhouse gas emissions per unit of gross domestic product ) by 18 percent from 2002 to 2012 . Over that same period , actual GHG emissions were projected to increase by 11 percent . The report estimated that in 2006 , U.S. GHG emissions decreased 1.5 percent from 2005 to 7,075.6 million tonnes of carbon dioxide equivalent . This was an increase of 15.1 percent from the 1990 levels of 6,146.7 million tonnes ( or 0.9 percent annual increase ) , and an increase of 1.4 percent from the 2000 levels of 6,978.4 million tonnes . By 2012 GHG emissions were projected to increase to more than 7,709 million tonnes of carbon dioxide equivalent , which would be 26 percent above 1990 levels .

Electricity sector in Argentina <=SEP=> The electricity sector in Argentina constitutes the third largest power market in Latin America . It relies mostly on thermal generation ( 60 % of installed capacity ) and hydropower generation ( 36 % ) . The country still has a large untapped hydroelectric potential . The prevailing natural gas-fired thermal generation is at risk due to the uncertainty about future gas supply .   Faced with rising electricity demand ( over 6 % annually ) and declining reserve margins , the government of Argentina is in the process of commissioning large projects , both in the generation and transmission sectors . To keep up with rising demand , it is estimated that about 1,000 MW of new generation capacity are needed each year . An important number of these projects are being financed by the government through trust funds , while independent private initiative is still limited as it has not fully recovered yet from the effects of the Argentine economic crisis .   The electricity sector was unbundled in generation , transmission and distribution by the reforms carried out in the early 1990s . Generation occurs in a competitive and mostly liberalized market in which 75 % of the generation capacity is owned by private utilities . In contrast , the transmission and distribution sectors are highly regulated and much less competitive than generation .