Optimizing Fuel-Based Environmental Strategies for Stack Emissions From Zigzag and Fixed Chimney Bull's Trench Kiln...

Pakistan has around 20,000 brick kilns, constituting 3% of global brick production. Consequently, air pollution and air quality indicators have significantly deteriorated. In this study, we examined the effect of different fuel types, such as coal, coal + wheat straw, and coal + rice straw, on stack emissions from FCBTK kilns and Zigzag kilns in Faisalabad, Pakistan. Standard protocols for measuring stack emissions, including smoke opacity, SO₂, and CO, were used. The results were compared with Pakistan's Punjab Environmental Quality Standards (PEQS). Specifically, in Zigzag kilns, blended fuels reduced CO emissions to approximately 123.7 mg/Nm³ with wheat straw and 162.2 mg/Nm³ with rice straw. In contrast, FCBTKs showed CO emission reductions of 233.17 mg/Nm³ with wheat straw and 341.07 mg/Nm³ with rice straw. For SO₂, Zigzag kilns achieved reductions of 412.7 mg/Nm³ with wheat straw and 352.4 mg/Nm³ with rice straw, while FCBTKs reduced emissions by 564.9 and 481.7 mg/Nm³, respectively. Smoke opacity in Zigzag kilns improved by 4.6 percentage points with rice straw and 2.3 with wheat straw, whereas in FCBTKs, the improvement was 41.4 and 20.3 percentage points, respectively. Statistical comparisons using Pearson's correlation and linear regression analysis further indicate that biomass additives combined with coal are more effective as fuels in the brick kiln industry. One-way ANOVA and Kruskal-Wallis tests, along with post hoc analysis, confirmed significant differences among fuel groups (p < 0.001), demonstrating strong relationships between fuel composition and emission levels. These additives significantly reduce air pollution and improve community health by lowering emissions of smoke opacity, SO₂, and CO. According to the results, blending agricultural residues with coal enhances emission performance, with Zigzag kilns showing the most significant reductions.