Emission factors of atmospheric and climatic pollutants from crop residues burning

摘要

Biomass burning is a common agricultural practice, because it allows elimination of postharvest-ing residues; nevertheless, it involves an inefficient combustion process that generates atmospheric pollutants emission, which has implications on health and climate change. This work focuses on the estimation of emission factors (EFs) of PM_(2.5), PM_(10), organic carbon (OC), elemental carbon (EC), carbon monoxide (CO), carbon dioxide (CO_2), and methane (CH_4) of residues from burning alfalfa, barley, beans, cotton, maize, rice, sorghum, and wheat in Mexico. Chemical characteristics of the residues were determined to establish their relationship with EFs, as well as with the modified combustion efficiency (MCE). Essays were carried out in an open combustion chamber with isokinetic sampling, following modified EPA 201-A method. EFs did not present statistical differences among different varieties of the same crop, but were statistically different among different crops, showing that generic values of EFs for all the agricultural residues can introduce significant uncertainties when used for climatic and atmospheric pollutant inventories. EFs of PM_(2.5) ranged from 1.19 to 11.30 g kg~(-1), and of PM~(10) from 1.77 to 21.56 g kg~(-1). EFs of EC correlated with lignin content, whereas EFs of OC correlated inversely with carbon content. EFs of EC and OC in PM_(2.5) ranged from 0.15 to 0.41 g kg~(-1) and from 0.33 to 5.29 g kg~(-1), respectively, and in PM_(10), from 0.17 to 0.43 g kg~(-1) and from 0.54 to 11.06 g kg~(-1). CO_2 represented the largest gaseous emissions volume with 1053.35-1850.82 g kg~(-1), whereas the lowest was CH_4 with 1.61-5.59 g kg~(-1). CO ranged from 28.85 to 155.71 g kg , correlating inversely with carbon content and MCE. EFs were used to calculate emissions from eight agricultural residues burning in the country during 2016, to know the potential mitigation of climatic and atmospheric pollutants, provided this practice was banned. Implications: The emission factors of particles, short-lived climatic pollutants, and atmospheric pollutants from the crop residues burning of eight agricultural wastes crops, determined in this study using a standardized method, provides better knowledge of the emissions of those species in Latin America and other developing countries, and can be used as inputs in air quality models and climatic studies. The EFs will allow the development of more accurate inventories of aerosols and gaseous pollutants, which will lead to the design of effective mitigation strategies and planning processes for sustainable agriculture.