Household solid fuel burning emission characterization and activity levels in India

Emission factors (EFs) of PM _2.5, carbon fractions, major ionic (K ⁺ , Ca ²⁺ , NH ₄ ⁺ , SO ₄ ²⁻ , NO ₃ ⁻ and Cl ⁻ ) and elemental (Al, Cr, Cu and Fe) species from combustion of commonly used household solid fuel were determined in 10 different states in India during cooking practices. The study involved sampling during actual household cooking involving use of a variety of fuels including coal balls (CB), fuel wood (FW), dung cakes (DC), crop residues (CR), mixed fuels (MF: dung cakes + fuel woods). Species-wise highest EFs (g·kg ⁻¹ ) were: 34.16 ± 10.1 for PM _2.5 (CB), 14.18 ± 5.8 for OC (CB), 2.33 ± 1.4 for EC (DC), 1.03 ± 0.2 for K ⁺ (CR), 2.21 ± 0.6 NH ₄ ⁺ (DC), 0.61 ± 0.2 for NO ₃ ⁻ (CB), 0.59 ± 0.1 for SO ₄ ²⁻ (CB), 0.69 ± 0.1 for Cl ⁻ (CR) among the fuels. Higher OC EFs for CB could be attributed to higher moisture content (>13%) in coal-powder that is used to handmade coal balls. It is observed that, in general, OC3 and EC1 were the dominant thermally evolved carbon mass fractions. The study averaged MCE values were in the range 0.93–0.98, which could be attributed to higher variability in flaming and smoldering episodes during the combustion of selected fuels. Sum of ionic EFs for emissions from DC, CR and MF were found to be higher than those observed for FW and CB. The K ⁺ /EC and Cl ⁻ /EC (~1) ratios could be better indicators of CR fuels to differentiate it from FW, whereas NH ₄ ⁺ /EC (~1) is suitable to indicate DC. Average annual emission estimates of PM _2.5 (2.00 ± 0.53 Tg·yr ⁻¹ ), OC (0.86 ± 0.23 Tg·yr ⁻¹ ) and EC (0.11 ± 0.02 Tg·yr ⁻¹ ) for tested fuels are evaluated to be contributing 27, 15 and 4% of total PM _2.5 , OC and EC, respectively, toward annual emission budget from different anthropogenic activities in India.