The Union Ministry of Environment, Forest and Climate Change (MoEF&CC) came up with stringent standards for brick kilns after seven years of deliberation via a notification dated February 22, 2022.
• Brick kilns have been identified as a major source of pollution in many non-attainment cities, that do not fulfil MoEF&CC's stipulated air quality requirements.
• The notification has paved the way to reduce air pollution from brick kilns, according to Delhi-based non-profit Centre for Science and Environment (CSE).
Background
• It all started in October 2015 when the MoEF&CC came out with a draft notification proposing different particulate matter (PM) emission standards for natural draught and induced draught kilns.
• CSE opposed the draft. It stated that state pollution control boards (SPCB) would not be able to monitor all 70-80,000 operational brick kilns in the country on a regular basis, due to lack of personnel.
• CSE thus pushed for technological change so that emissions would inherently be less. MoEF&CC, in its current notification, has mandated allowing brick kilns
• Only with zig-zag technology or vertical shaft or use of piped natural gas (PNG) as fuel in the brick-making process.
• The introduction of PNG as a fuel is a welcome step since its use in older technology like Fixed Chimney Bull's Trench Kiln (FCBTK) will automatically reduce the PM emissions.
Other Features
• Standard for PM emissions - 250 milligram per normal cubic metre (mg/Nm3)
• Existing brick kilns shall be converted to either zig-zag technology or vertical shaft or use of PNG as fuel in brick making within a period of one year in case of kilns located within a 10 km radius of non-attainment cities and two years for other areas.
• All brick kilns shall use approved fuel such as PNG, coal, fire wood and / or agricultural residues. Use of pet coke, tyres, plastic, hazardous waste shall not be allowed in brick kilns.
• Brick kilns shall construct permanent facility for port hole and platform according to the norms laid down by the Central Pollution Control Board (CPCB).
• Brick kilns shall follow fugitive dust emission control guidelines as prescribed by concerned SPCBs.
• The brick kiln owners shall ensure that the roads utilised for transporting raw material or bricks are paved.
Zig Zag Technology
• In zigzag kilns, the bricks are arranged in such a way that hot air can escape through a zigzag route.
• The length of a zigzag air path is about three times that of a straight line.
• This path improves heat transfer from the fuel gases to the bricks. This makes the whole process more efficient.
Vertical Shafted Technology
• It is an energy-efficient and eco-friendly combustion technology for the production of baked bricks.
• The VSBK technology has evolved from the traditional up draught kilns in rural China during late 1950s; however, the widespread dissemination of the technology took place after the economic reforms.
• At its peak during the mid 1990s, thousands of VSBKs were reported to be operating in China.
Working Procedure
• Vertical shaft brick kiln is a continuous, moving ware kiln in which bricks are red in a vertical shaft of rectangular/square cross-section.
• Generally each shaft is connected with two chimneys (2.1), located at diagonally opposite corners of the shaft.
• The working platform (the top of the shaft) is usually shaded by a roof (2.2). Green bricks and fuel, which are loaded in the shaft from the top, are lifted to the working platform using conveyors or lift.
• Green bricks are loaded from the top of the shaft in batches.
• The fuel, generally crushed coal or briquettes, is laid along with the green bricks.
• Air for combustion enters the shaft from the bottom. It gets preheated by the hot red bricks in the lower section of the shaft (brick cooling zone) before reaching the combustion zone.
• After combustion, the hot flue gases preheat the green bricks in preheating zone before exiting the kiln through the chimneys.
• The brick setting in the shaft is supported on removable bars provided at the bottom of the shaft.
• Brick unloading is carried out in batches from the bottom with the help of a trolley.
• Generally, every 2-3 hours, one batch is unloaded at the bottom and a batch of green bricks is loaded at the top.
• At any given time, there are typically 8 to 12 batches in the kiln.
Brick Kiln and Pollution
• According to the science and technology department, if a kiln runs on the old technology, its emission levels are 500 to 1500 mg/Nm3 (carbon, sulphur and several other harmful metals in the air).
• Meanwhile, an upgraded brick kiln's emission levels were found to be in the range of 105 to 195 mg/Nm3, and it can check particulate matter in air upto 70%:
Numerous plumes of toxic black smoke (black carbon) billow from brick kilns in developing countries and are a common sight.
The contaminating emissions which result cause:-
•Hazardous working conditions.
• High rates of respiratory disease and premature death amongst workers and local communities.
• Agricultural impacts – damaging soil, crop production and food security. Rice and wheat crops being particularly susceptible.
Transboundary black carbon from thousands of kilns directly contributes to glacial melting in the Himalayas and affects monsoonal rainfall patterns.
•Damage to biodiversity.