Emission factors of some common grass species in West Africa

Frequent burnings occurring in the grasslands of the West African region during the dry seasons largely contribute to emissions of trace gases and particulates being released into the ambient environment, which has significantly impacted both regional and global climate patterns. Burning potentials of forty different grassland biomes were examined by determining their Net Heating Value (NHV) and Total Organic Carbon (TOC). Simulations of the field operations which involve open burning were performed in the laboratory using a fabricated combustion chamber for the determination of emission factors. Particulates were collected using Whatman quartz fibre filters and analyzed gravimetrically. Emissions of gaseous pollutants from open burning of these common grass species were measured with portable devices. The values of the NHV and TOC of the grass species ranged from 15,022.19 to 18,181.84 kJ/kg and 21.14 to 55.62%, respectively. The average Emission Factors (EFs) obtained for carbon dioxide (CO₂), carbon monoxide (CO), sulphur dioxide (SO₂), nitrogen dioxide (NO₂), volatile organic compounds (VOC), and PM_2.5 are 1465.55 g/kg, 40.99 g/kg, 0.39 g/kg, 0.02 g/kg, 7.78 g/kg, and 6.00 g/kg, respectively. The study has shown that Digitaria nuda, Digitaria eriantha, Panicum subalbidum, Paspalum polystratchyum, and Perotis indica have the highest emission factors for CO₂, CO, SO₂, NO₂, VOC, and PM_2.5, respectively. The result obtained would help in the quantification of the global warming forcing on the climate in the West African region from grassland burnings. The results will potentially serve as additional information for emission inventories and basis for the formulation of mitigation strategies.