Bending the Chimney to Clear the Kathmandu Valley

Brick kilns ring the Kathmandu Valley and are among the largest sources of the black carbon and fine particulates that settle over it, because the traditional fixed chimney Bull's Trench design lets fuel burn incompletely and vents the result straight out. The zigzag retrofit is unglamorous engineering: restack the bricks so combustion gases follow a longer, hotter, more turbulent path, and far less unburned carbon escapes. MinErgy, which grew out of Nepal's Swiss-funded Vertical Shaft Brick Kiln project, has worked with the Federation of Nepal Brick Industries and ICIMOD to make that retrofit normal — co-producing the national design manual kiln owners actually build from. By 2019 the Clean Brick Initiative had converted 289 of Nepal's 1,035 fixed chimney kilns, cutting 1,134 tonnes of particulate emissions and saving nearly 20,000 tonnes of coal a year, which is what makes the argument to owners: cleaner air is also cheaper bricks.