Moving to Natural Gas for Brick Firing – Is it possible in India?

With building stock set to increase manifold in India over the next few years, the conversation has moved to how we can continue to progress, but in a sustainable way. Constructing more buildings is essential, especially given the kind of urban development the country is seeing – after all everyone needs a roof to sleep and work under.

But there are fundamental changes that need take place in the building industry if we don’t, at the same time, want to be victims of the very development we encourage.

It is high time that all stakeholders of the building industry think about the practical solutions that are possible given this scenario. And one such practical solution that can result in significant benefits is using natural gas for brick firing.

While this might seem like an innovative move, you might be surprised to learn that Europe has been using natural gas for brick firing for as far back as 1960s. Seeing its many benefits, using natural gas for brick firing was mainstreamed in Europe as early as 1970s and 80s. So much so that by 1990, almost 80% of the fuel used in European brick making was contributed by natural gas.

It might be stating the obvious that natural gas is cleaner fuel. This means it will not pollute the environment as much, given it generates lesser particulate matter and results in less CO2 emissions. That might seem like enough reason for the brick industry to shift to natural gas, but there are more benefits. This process improves the overall quality of bricks and is safer for the health and wellbeing of the employees who work in the kiln.

But let’s be honest. Market reality is a consideration for any industry, as it is for the brick industry. Granted that using natural gas to fire bricks produces less pollutants, but what about the feasibility aspects? Here is where we can borrow significant lessons from the experiences of the European brick industry.

We can see from the graph above that the European brick industry adapted to natural gas gradually. This happened as natural gas availability and pipeline network expanded. Additionally, technologies such as better designed driers and kilns; the use of high-speed burners; and automated control of drying and firing regimes continues to make the process and end product economically viable.

However, the fact of the matter is that even in Europe the shift to kilns using natural gas took over 30 years. So is it really possible in India?

The good news is that this change has already started taking place in India, albeit slowly. One encouraging example is from Wienerberger India, who have converted their factory at Kunigal, Karnataka to natural gas firing. The bricks (hollow blocks) being made in this factory are found to be 60% lighter than conventional walling material (solid bricks), which converts to significant savings on structural cost due to reduction in dead load. This is in addition to the fact that lighter bricks allow for faster construction and ease of handling. Overall, the natural gas fired bricks being made in the factory are consistent and of higher quality.

Additionally, the Government of Punjab recently announced that it would explore the possibility of shifting brick kilns from coal to natural gas. While many kilns in the state had already shifted to the more energy efficient high draught zigzag kiln, government officials note that these kilns can further shift to natural gas without much change in their design. CNG is already widely available in Punjab.

So yes, brick firing with natural gas is possible in India but it does come with a few caveats.  In fact, even our neighbour, Bangladesh, has been using natural gas to fire bricks for several decades now and has operational natural gas fired Hoffmann kilns.

A Natural Gas Fired Hoffmann Kiln in Bangladesh

While in Europe, the brick industry is an organised industry and the brick kilns employ tunnel kiln technology, in India the brick industry is unorganised, with numerous small enterprises and mostly using zig-zag, FCBTK and clamp kiln technologies. Work is needed to develop cost effective technology solutions to convert existing kilns to natural gas firing. The dispersed nature of the industry will surely pose a challenge for supplying natural gas to brick kilns. Shifting to this newer process requires investment in both natural gas infrastructure and for upgrading the kiln. This means financial investment from kiln owners and brick makers being trained to use the new technology.

This might seem like a speed bump at this point in time but we only need to look at the European experience to know that the investment is worth it for all stakeholders involved.

What makes Fired Clay Bricks a preferred building material?

Fired clay brick is the most popular walling material in India. As per Census 2011, almost 12 crore or 50% of the total houses in India were made using fired clay bricks.

Let us look at the reasons which makes fired clay bricks a preferred building material:

Long life: If we look around us, we will find several buildings made from fired clay bricks such as houses, temples, mosques, railway bridges, government offices, etc. which are almost 100 years old. Properly fired clay bricks can last for thousands of years, as shown by the bricks obtained in the excavation of Harappan civilization which are 4000 years old.

Structural strength: Good quality fired clay bricks have a compressive strength in the range of 100 -300 kg/cm2, which lends good structural strength to the walls. Brick walls are able to support built in cupboards, heavy shelves, geysers and wall mounted fixtures.

Safety in case of fire: Fired clay bricks are incombustible and hence resists rapid spread of fire. As bricks are fired at a temperature of around 1000oC during the firing process they are capable of resisting this level of heat without damage.

Safety in case of flooding: Fired clay brick is a ceramic material. A brick absorbs moisture in its pores when wet and dries out quickly once the water recedes.

Saving in electricity consumption: The thermal conductivity of a solid fired clay bricks is almost 1/3rd that of a solid concrete block, thus a wall made from solid clay brick conducts less heat compared to a wall made from solid concrete blocks. Brick wall also has good thermal mass. Houses made from fired clay bricks remains cooler during summer compared to houses made from concrete blocks or concrete walls. If a brick cavity wall (consisting of two solid brick walls with an air cavity) is employed or a wall with hollow clay blocks is made, then houses can be kept even more cooler. As the houses remain cooler, less electricity is required for air-conditioning.

Less maintenance cost: Fired clay bricks are an exceptionally durable material. Compared to walls made from AAC blocks, walls made from fired clay bricks suffer less cracks and less damage from water and hence the maintenance cost remains low.

No toxicity: Fired clay bricks are made from natural materials and does not generally contain any toxic material so the possibility of toxic material leaching out or getting released in the atmosphere are less.

Reusability: Fired clay bricks have a long life, they can be salvaged during building demolition and can be reused. In this way the resources and energy once used in the production can be utilized for hundreds of years thus reducing the future requirement of resources and energy.

Aesthetics and style: In India, most of the fired clay bricks are of red colour and mostly brick walls are plastered on both the sides. However, it is possible to manufacture fired clay bricks in various colours, such as red, orange, yellow, white, black, pink, etc. Exposed brick work from different coloured and textured bricks add to the aesthetic and style quotient of a building.

In recent years, environmental damage caused during the production of the fired clay bricks have attracted the attention of the government and society at large. It is the responsibility of the fired clay brick industry and the government to take immediate actions to address these concerns. It can be said that in coming years, use of alternate materials like fly ash bricks and AAC blocks is likely to increase, however if the fired clay brick industry and the government work together and take timely actions, then fired clay bricks are likely to remain the first choice of home builders for a long time to come.

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Impact of Coronavirus on Indian Brick Industry: Part I

Brick production season in most parts of India is usually of 6-7 months, starting in November/December and ending with the arrival of the monsoon in May/June. The Coronavirus crisis has hit right in the middle of the brick production season and at a time when the brick industry was already struggling with slowing demand, closure due to air pollution during winter months, production loss in northern states due to frequent rains, etc. Information received from Punjab, Haryana, UP, Bihar and West Bengal indicates that most of the brick kilns are operational during the lockdown period. However, many brick kilns are facing problems due to shortage of coal, shortage of cash to pay the wages and buy raw materials. In this article, we would be assessing the potential impact on the demand of bricks during the rest of 2020.

A new report by Anarock Property Consultants Pvt Ltd, titled “Covid 19 Impact on the Indian Real Estate sector”, provides a good assessment of likely impact on organized real estate industry located in urban centers. The report was published a few days ago. We will focus on the assessment for the residential construction which is the largest consumer of bricks in the country. Some of the key observations and conclusions of the report are:

  1. Due to Coronavirus lockdown, the sales of the new flats have come to a complete halt due to restrictions on physical site visits, meetings, documentation and registration, etc. This may continue for some more time and will severely impact the cash flows of the builders.
  2. The supply chain of the construction materials (cement, steel, bricks, etc.) has been badly impacted and a part of the construction work force consisting of migrant workers have gone back to their villages. It may take several weeks and months before the supply chain is restored and workers come back.
  3. During last few years almost 40% of the new residential project launches in the top 7 cities of India is in the affordable housing segment. The home buyers of this segment are mostly lower income group families, which are likely to be the most affected segment of the working population. This segment has limited income and are involved in jobs/businesses, where work from home is not an option, thus this segment will incur loss in income and several families may be forced to postpone their decision to own the house.

Overall, the report estimates that in the year 2020, the residential sales are likely to register an annual decline of around 25-35%. In addition, the launches of new residential projects during 2020 is set to decline by 25-30 %, thus impacting the demand for bricks in 2021 also.

In India, small towns and rural areas account for more than 50% of the brick sales, so it is important to look at the situation there also. The economy of these areas primarily depends on agriculture. This is the Rabi harvesting season in Northern India. Labour which is essential for harvesting as well as for the operation of mandis is in short supply. Newspaper reports indicate that many mandis are also not working and despite permissions, movement of trucks and combine harvesters is restricted.  Delay in harvesting mean a lower yield, exposing the crop to sun and rain, besides leaving a smaller time frame for preparing the field for the kharif crop. Similarly, the revenue of horticulture and vegetable farmers are also hit due to logistics issues. Overall, the farmers throughout the country are expected to incur loss in income, this in turn is likely to delay construction in rural areas, some believe till the end of the rainy season.

Thus, it seems that the Coronavirus will result in significant reduction in brick demand during 2020 in both urban and rural areas and the brick industry should start looking at ways to survive through the crisis and come out stronger from the crisis.  Two steps which come to my mind are:

  • Implementing measures to reduce the cost of production, wastages of all kind (fuel, clay, poor quality bricks, etc.) and improving productivity. Adoption and proper operation of zig-zag kiln technology is an example to reduce wastages, but there can be other simple technologies and measures that can be adopted. Conversion to zig-zag kiln technology results in around 20-25% savings in fuel and the percentage of class-I brick production can be increased to 80-90%. A lot of brick kilns in recent years have adopted zig-zag technology but many are not operating it properly. Training workers and implementing proper operation practices in zig-zag kiln technology should be a priority at this point of time. Brickguru has a lot of information on this and would be adding new information in the coming weeks.
  • The brick industry, which is a major employment generator in the country, should quickly organize itself and present its case for receiving support from the state and central governments, such as:
    • Assuring unhindered supply of coal,
    • Utilizing funds under the skill mission for the training of brick kiln workers,
    • Facilitating loans from banks for technology upgradation,
    • Simplifying and streamlining environmental and mining rules and regulations,
    • Removing restrictions on the procurement of clay bricks for the government projects, etc.

We would like to hear from you, about How Coronavirus has impacted brick industry in your area? What innovative measures are you taking to reduce the cost of production, wastage and improve productivity? What kind of help would you request from the Government ?  Please WhatsApp your response at 9711153307 or send an email at by April 12th, we will publish selected responses in our next blogs.

Bihar releases “Standard Design of Zigzag Brick Kilns” and a case study on “Bihar’s Experience of Implementing Cleaner Brick Kiln Directive”

In an event organised by the Bihar State Pollution Control Board (BSPCB) on 7th February 2019 at Patna, the Deputy Chief Minister of Bihar Shri Sushil Kumar Modi released two documents – (i) Standard Design of Zigzag Brick Kilns for Bihar and (ii) Case Study on “Bihar’s Experience of Implementing Cleaner Brick Kiln Directive”.

The BSPCB had issued a directive to the brick kiln enterprises in the state to upgrade to cleaner technologies. During the first one and half years, about 1500 kilns (20-25% of the total kilns in the state) have upgraded, and most of them opted for zigzag brick kiln technology. Initial experience showed that there were variations in the designs of zigzag kilns – mostly being adopted from the neighbouring states of Uttar Pradesh and West Bengal. This also resulted in variations in the kiln performances, and the need for a standard design of zigzag kilns to suit the specific requirement of Bihar was expressed by the brick industry.

As more than 5000 kilns in the state were yet to upgrade to cleaner technologies, availability of standard design can greatly help the industry and expedite the process of technology upgradation. With this objective, the BSPCB constituted an expert committee to review the available designs and recommend a standard design of zigzag kiln for the state of Bihar. The Expert Committee consisted of members from the concerned departments of Government of Bihar (Department of Mines, Department of Industries), brick kiln experts (Punjab State Council for Science & Technology, Greentech Knowledge Solutions), academic institutions (IIT and NIT, Patna) and representatives from Bihar brick industry and two leading brick entrepreneurs and kiln experts from West Bengal and Uttar Pradesh. With support from Shakti Sustainable Energy Foundation, Greentech team provided technical support in review of the available designs of zigzag kilns, technical analyses, and development of the standard design. The entire process took about 4 months time.

The cleaner brick kiln directive of the BSPCB was issued in two phases – firstly, as a pilot in February 2016, it was issued to the brick kilns located in five blocks of Patna district only. To assist the brick makers in transition to cleaner technologies, a one-year technical support programme was put in place with the support from Shakti Sustainable Energy Foundation. The case study – “Bihar’s Experience of Implementing Cleaner Brick Kiln Directive”, documents the strategy and process of implementation of this technical assistance programme and its outcomes, and draws important learnings from it. The experience and learnings gained during the pilot phase helped in designing the technical support program and its implementation for the next phase when the directive was extended to the entire state in August 2017.

To download the document on “Standard Design of Zigzag Brick Kilns for Bihar”, click here.

To download the case study on “Bihar’s Experience of Implementing Cleaner Brick Kiln Directive”, click here.

Potential Impacts of the Draft Amendments to the Fly Ash Regulation, 1999. Part 1: Is the quantity of available fly ash sufficient to meet brick demand in the country?

Ministry of Environment, Forest and Climate Change (MoEFCC) through a notification dated 25th February 2019 has proposed amendments in the existing regulation (S.O. 763(E) dated 14th September 1999) to promote utilization of fly ash in the country. The Ministry will consider any objections or suggestions received during a period of sixty days on the draft amendments in the regulation.

This is the first article of a series in which the Brickguru team would be analyzing the potential impacts and feasibility of the various provisions of the proposed amendments in the fly ash regulation. The purpose of these articles is to facilitate an informed debate on the proposed amendments. In this article we examine the proposed amendment from the point of fly ash availability to meet the demand for bricks in the country.

What is the availability and utilization of fly ash from thermal power plants?

As per the latest data provided by Central Electricity Authority (CEA) [1], India generated 196 million tons (MT) of fly ash from thermal power plants in 2017-18 out of which 131 million tons (67% of the total fly ash generated) was utilized.

What are the main proposed amendments to the Fly Ash Regulation, 1999?

The proposed amendments are focused towards increasing the fly ash utilization in the production of bricks and blocks. India currently produces around 25,000-30,000 crore bricks per year, out of which around 80% of the production is of burnt/red clay bricks, and less than 10% is contributed by fly ash bricks and blocks. The amendment aims at replacing the majority of burnt/red clay brick production in the country with fly ash bricks and blocks (having minimum 50% fly ash by weight). To achieve this objective, the draft has two main proposals.

a) Mandating red clay brick manufacturing units to shift to fly ash brick manufacturing

The regulation proposes that within a 300 km radius of a coal or lignite based thermal power plant, no new red clay brick kiln shall be installed, and all existing red clay brick kilns located within 300 km shall be converted to fly ash brick or block manufacturing unit within one year. If we draw a 300 km radius around thermal power plants on a map of India, it practically covers the entire country (barring some parts of North-East India and the Himalayan region). Thus, in practice the regulation proposes that 150,000-200,000 existing red clay brick making units (having annual production capacity of 20,000- 25,000 crore bricks/year) should change their manufacturing technology and shift to fly ash brick and block manufacturing within one year.

Source: Centre for Science and Environment, New Delhi

b) Mandating thermal power plants to supply fly ash to fly ash brick manufacturing units

The draft regulation proposes mandatory requirements on power plants:

  • Thermal power plants to make available at least 20% of dry ESP fly ash to units manufacturing fly ash bricks, blocks and tiles.
  • Thermal power plants to supply fly ash at almost zero price (@ Rs 1/ton) as well as to bear the full cost of transportation of fly ash to fly ash brick manufacturing units located up to 300 km from the power plant.

Analysis of fly ash brick production potential under various scenarios

The following analysis examines fly ash brick production potential under various scenarios and the feasibility of replacing burnt clay bricks by fly ash bricks and/or blocks.

Scenario 1: 20% of the total annual fly ash generation is utilized for the production of bricks

If one fly ash brick (size: 230 x 110 x 70 mm) is assumed to have a weight of 2.8 kg and consist of 50% by weight of fly ash, then the quantity of fly ash that will get consumed in producing one fly ash brick will be 1.4 kg. If 20% of the total annual fly ash generation in the country i.e. 39 million tons (in 2017-18) is utilized for the manufacturing of bricks, the total number of bricks produced using fly ash would be 2,800 crore bricks/year. As 9% of the fly ash is already being utilized resulting in production of 1,300 crore fly ash bricks, the additional fly ash brick production would be 1,500 crore bricks. This additional production would result in replacement of only around 6-7% of the current production of red/burnt clay bricks by fly ash bricks.

Scenario 2: 100% of the unutilized annual fly ash generation (or 33% of the total annual fly ash generation) is utilized for the production of bricks

Going beyond the proposed regulation, if we assume that the entire unutilized annual fly ash generation (or 33% of the total annual fly ash generation i.e. 65 million tons in 2017-18) is used for the production of bricks, it would result in production of 4,600 crore additional fly ash bricks. This additional production would result in replacement of only around 20 % of the current production of red/burnt clay bricks by fly ash bricks.

Scenario 3: Utilization of Pond Ash

Till now we have analyzed the utilization of the annual fly ash generation/ dry ESP fly ash available as the draft amendment is only concerned about this. In addition to annual fly ash generation, pond ash (fly ash and bottom ash stored in ash ponds) is also available and several stakeholders may have an interest to know the potential of fly ash brick production using this pond ash. Based on CEA data, the quantity of pond ash available is estimated at 1,397 million tons. If it is assumed that 50% of the total available pond ash will be made available for making fly ash bricks it would result in the production of around 50,000 crore bricks or equivalent to 2 years production of burnt/red clay bricks for the country.


The draft amendment intends to shift the entire red/burnt clay production to fly ash bricks and blocks in 300 km radius of thermal power plants. The analysis shows that the quantity of fly ash that could be made available for the units manufacturing bricks, will be sufficient only to replace a fraction (6 to 20%) of the current burnt/red clay brick production in the country. Even reaching these replacement levels will be challenging due to regional disparities in the availability of fly ash and demand for bricks. Steady increase in demand for bricks till 2050 and stagnation in coal based thermal power generation in the near future may make meeting these replacement levels even more challenging.

In the light of the above findings, the proposal that “No new red clay brick kiln shall be installed within the 300 km radius from a coal or lignite based thermal power plant after publication of this notification. The existing red clay brick kilns located within 300 km shall be converted into fly ash based bricks or blocks or tiles manufacturing unit within one year” does not seem to be a feasible option.

(To download a document with more details and additional analysis, click here.)

(In the next article we will be exploring the energy and environment impacts of transporting fly ash. Any comments on this article can be sent to and


1. CEA, 2018a. Report on Fly Ash Generation at coal/lignite based thermal power stations and it’s utilization in the country for the year 2017-18. Central Electricity Authority, Ministry of Power, Govt of India, New Delhi, December 2018.

2. CEA, 2018b. National Electricity Plan (Volume 1: Generation). Central Electricity Authority, Ministry of Power, Govt of India, New Delhi, January 2018.

3. BMTPC, 2018. Building Materials and Housing Technologies for Sustainable Development (Editors: Shailesh Kr. Agarwal, S.K. Gupta and Dalip Kumar). Proceedings of the National Seminar on Emerging Building Materials and Construction Technologies, February 22-23, 2018, New Delhi organized by the Building Materials and Technology Promotion Council – BMTPC (pp 294-306).

The Clay Brick Industry Needs to Transform to Stay Relevant in the Ever-Growing Indian Construction Industry

Brick, i.e. common burnt clay building brick, is perhaps the only manmade material that has defied time gracefully ever since it was invented about 5,000 years ago. Technically, clay bricks fall under the category of heavy-clay products, forming a major part of the ceramic industry.  Heavy-clay products are those that are mainly made from a single clay with very little addition of other raw materials.  They are principally used in structural work.  Hence heavy-clay products like bricks (solid and perforated), hollow clay blocks, roof tiles, split tiles, etc. are often called structural clay products.

It is a matter of great pride for all Indians that the oldest fired clay brick found yet in the world belongs to the ancient city of Kalibangan (Rajasthan) which was a part of the then Pre-Harappan Indus Valley Civilization, which existed around 3000 B.C. Unlike metals and organic materials, brick weathers beautifully with time, never giving in completely to the onslaught of natural agencies working against it.


The rise of Alternate Walling Materials …

With this strong – and enviable – position among walling materials, till recently, it was thought that no alternate walling material will ever be able to threaten fired clay brick seriously on technical as well as commercial grounds.  However, lately, many alternative walling materials viz. stabilized soil bricks/blocks, perforated clay bricks/ hollow clay blocks, concrete blocks/bricks, laterite blocks, flyash/Fal-G bricks, calcium silicate bricks, AAC blocks, CLC blocks, etc. have entered and established themselves firmly in the market.

Although fired clay bricks still account for 75-80% of today’s walling material market in India, the share of non-fired walling materials, particularly FaL-G bricks, AAC/CLC blocks and concrete blocks/bricks, is increasing day by day, especially in the metro markets where it has now gone beyond 50%.


Why Did the Alternate Walling Materials Enter the market?

The process of entry of alternate walling materials started in the 1960s in the metro markets of Western & Southern India, with the introduction of Concrete Cellular Blocks and AAC Blocks, although their impact has become visible only during the last decade. This became possible because the traditional fired clay bricks did not meet market expectations, either partially or fully, over a long stretch of time.

Given the nature of the industry, builders wanted bricks which were available year-round and had a stable price. Traditional clay bricks were unable to match up to competitive pricing and quality expected from Reinforced Cement Concrete (RCC) frame structures, including- light weight, large format, appropriate strength, and low water absorption. Additionally, those producing traditional fired clay bricks were often unable to comply to formal ways of doing business.


How does the clay brick industry deal with this competition?

The only feasible solution is that the clay brick industry change with the times by giving the building sector what they need. The changes that the clay brick industry needs to make in the face of this shift to alternative bricks are multi-faceted.

First, some external measures need to be considered vis-à-vis the urgent need to improve market sentiment and perception about clay bricks. This can be done through innovative outreach activities such as the global campaign “Stay with Clay”, which was started by Wienerberger. To further ensure this message reaches far and wide, central, state, and district Brick Manufacturers’ Associations across the country need to take a lead in changing how the construction industry views clay brick producers. By turning into industry’s priorities clay brick manufacturers should focus on advocating aspects such as cost-effectiveness and eco-friendliness of their product through meetings, seminars, social media, technical papers and research studies.

At the same time, some internal changes need to be made by the industry. A significant change can be brought by producing clay bricks all year round by step-by-step adoption of ‘appropriate’ mechanization and professional production management. Manufacturers need to realize that solid bricks can be made lighter by incorporating burnable agricultural, industrial, domestic wastes into clay and making them as ‘porous’ as possible. This can be especially relevant for kilns around Maharashtra and coastal Andhra Pradesh. Manufactures can also get creative by using ‘rat-trap’ bonds for solid bricks used for walling and by promoting large format hollow clay blocks.

A lot is still left to be done if the clay brick industry wants to remain relevant. This necessary shift in the clay brick industry has not seen much momentum to date, because of which more players in the building sector are moving away from using clay bricks. Only if the clay brick industry makes these much-needed changes quickly will they be able to survive the changing landscapes of the construction business. These changes, thus, must come from the industry themselves, sooner than later.

Prevalent Misconceptions regarding Construction and Operation of a Zigzag Kiln

Greentech Knowledge Solutions Private Limited (GKSPL) and Bihar State Pollution Control Board (BSPCB) have jointly conducted several workshops on “Design, construction and operation of a Zigzag Kiln” across different districts of Bihar during 2018-19. During the workshops, we have observed that there are many fundamental misconceptions prevalent among kiln owners and masons regarding construction and operation of a Zigzag kiln. Here we have tried to clear up the most widespread misconceptions in a very clear manner with short explanations.


  1. “Zigzag kiln” is a completely new design of kiln for brick production.

It must be clear in everybody’s mind that “Zigzag kiln” is NOT a completely new design of brick kiln and it is similar in many ways to the traditional “oval shape” Bull’s trench brick kiln. Zigzag kiln is just an “improved version” of the traditional kiln. The main difference between oval-shape Bull’s trench kiln and Zigzag kiln is the brick-setting pattern and hence, the fuel feeding/firing method. Applying the improved brick-layout design in a Zigzag kiln, air/hot-gases are provided more time to exchange heat with bricks which is the main reason for its better performance compared to a conventional kiln.


  1. Is it necessary to change the shape of kiln from oval to rectangular while upgrading from traditional kiln to Zigzag kiln?

Yes, it is RECOMMENDED for a Zigzag kiln to have a rectangular shape to properly employ improved brick-setting pattern and thus to obtain better performance compared to traditional kiln.


  1. “Zigzag kiln” and “High-draught kiln” are two different kiln designs.

Zigzag kiln refers to a kiln in which air/hot-gases does NOT flow “mostly” in a straight line (unlike in traditional oval-shape kiln) along the length of trench. Zigzag kilns can be of two types:

  1. Natural-draught Zigzag kiln: In this type, draught is created naturally within the kiln with the help of chimney.
  2. Induced-draught or High-draught Zigzag kiln: In this type, draught is created artificially within the kiln with the help of fan and chimney.


  1. There are separate types of chimneys for natural-draught and induced-draught or high-draught Zigzag kilns.

Chimney type is SAME for both natural-draught and high-draught Zigzag kilns. The cross-section of chimney can be either circular or square in both types of Zigzag kilns. For a given daily production capacity and brick-setting design, chimney internal diameter and height changes according to the type of Zigzag kiln.


  1. In a Zigzag kiln, a new design of chimney called “Zigzag chimney” is required to be installed.

It is absolutely WRONG to say that a new type of chimney called “Zigzag chimney” is essential to run any Zigzag kiln. If for a given daily production capacity and brick-setting design, the required internal width, height and quality is met by the existing chimney, then the same chimney can be used to operate the Zigzag kiln.


  1. To operate a Zigzag kiln, only the chimney having square cross-section will work.

It is NOT necessary for a chimney to have square cross-section to operate any Zigzag kiln. The cross-section of chimney can be either circular or square in both the types of Zigzag kilns.


  1. State pollution control board will only allow the chimney having square cross-section to operate a Zigzag kiln.

There is NO demand from state pollution control board to compulsorily install chimney having square cross-section to operate a Zigzag kiln. Both circular and square cross-sectional chimney are permitted to run any Zigzag kiln.


  1. There are strict orders from state pollution control board that the height of new or retrofitted chimney must be greater than the existing one.

Central or state pollution control board ONLY specifies the “minimum height” of chimney as per the type of Zigzag kiln. If the existing, new or retrofitted chimney is meeting the required minimum height criteria for a given Zigzag kiln type, pollution control board will allow it to operate. According to draft notification published on March 16, 2018 by “Ministry of Environment, Forest and Climate Change”, the minimum height requirements for Zigzag kiln are as follows:

  1. In an induced-draught or high-draught kiln only “single Zigzag type” brick setting will work.

Since in an induced-draught or high-draught kiln the required draught is created artificially with the help of fan, ANY type of brick setting viz. single, double or triple Zigzag can be employed satisfactorily.


  1. When using a fan in induced-draught or high-draught Zigzag kiln, it is compulsory to increase the height of chimney.

If the chimney is meeting the “minimum height criteria” set by central or state pollution control board and the chimney’s internal width and height is meeting the design criteria for the required daily production capacity, it is NOT compulsory to increase the height of chimney.


  1. In a Zigzag kiln, the brick-setting design is completely different from the design used in traditional oval-shape Bull’s trench kilns.

Brick-setting design in a Zigzag kiln is NOT VERY different from the setting employed in conventional oval-shape Bull’s trench kiln. The basic pattern of stacking bricks in “rows” along the width of trench with each row containing several “brick columns” is same in both traditional and improved kilns. To increase the time required for heat exchange between bricks and hot-gases/air, some rows in Zigzag kilns are made differently (like a wall) to allow air/hot gases to flow past them only through few spaces left in the wall. (For more details, refer Knowledge briefs a). How is setting of bricks done in a natural-draught kiln, b). How is setting of bricks done in an induced-draught Zigzag kiln).


  1. Is it compulsory to install platform and ladder on the chimney for emission measurements?

Yes, it is COMPULSORY to install platform and ladder on the chimney as per the criteria set by central/state pollution control board to facilitate the kiln’s emission measurements. (For more details, refer Knowledge brief – What are the good practices for the construction of masonry chimney of a Zigzag kiln?).

Specific Energy Consumption for Firing – What it is and Why you should use it

Brick kiln owners are familiar with the basic process of brick making: clay preparation, moulding, drying of green bricks, and, finally, firing.

Brick manufacturing is an energy intensive process, with most of the energy being consumed towards firing the bricks.  The last stage of brick making is firing, which converts green bricks from a loosely compacted blend of different minerals into a strong, hard, and stable product. It is the firing process that determines the properties of the fired brick, including the strength, porosity, hardness, making it an important step that concerns all brick makers.

Calculating the energy consumed to fire bricks is an important parameter used to measure a kiln’s performance. Most brick makers calculate their kiln’s energy performance by the number of tons of fuel used per lakh bricks. However, this is not the best way to measure energy performance.  In this context, Specific Energy Consumption, or SEC, is used to understand a kiln’s energy efficiency by measuring the amount of thermal energy used to produce 1 kg of fired brick. This depends on the type of clay, operation practices, and the efficiency of kiln technology.

As a brick kiln owner, if you find that your kiln has high SEC, you should plan to improve your operational practices at the kiln. You may also consider shifting to a more efficient kiln technology. Efficient firing technologies, such as Zigzag Kiln and Vertical Shaft Brick Kiln (VSBK), have lower Specific Energy Consumption in comparison to conventional technologies such as Clamp and Fixed Chimney Bull’s Trench Kiln (FCBTK).

The following table gives the typical SEC of a few types of brick kilns which were monitored in India.

Kiln Type Range of Specific Energy Consumption (MJ/kg)
Fixed Chimney Bull’s Trench Kiln (FCBTK) 1.1 to 1.5
Zigzag Kiln 0.9 to 1.2
Vertical Shaft Brick Kiln (VSBK) 0.6 to 1.0
Clamp 1.5 to 4.0


For calculating SEC, one requires not only the weight of the fired products but also the Calorific Value (C.V.) and the quantities of all types of fuels used in the kiln.

Let us consider a case to see why SEC is a better calculation method. Suppose two brick kilns located in Patna, one an FCBTK and the other a Zigzag Kiln, reported that both of them consume 15 tons of coal per lakh bricks, and the weight of fired bricks of both is 3 kg per brick. If no further information is available, one may conclude that the energy performance of the two kilns is the same. But with added information that the type of coal used in the two kilns was not the same – FCBTK uses US coal (calorific value 6,500 kcal/kg) and Zigzag Kiln uses Assam coal (calorific value 5,800 kcal/kg), calculating SEC of the kilns we know that Zigzag Kiln has SEC of 1.22 MJ/kg, while FCBTK has SEC of 1.37 MJ/kg. This means Zigzag Kiln consumes less energy than FCBTK.

Let us look at another example. Kiln A located at Yamunanagar uses three fuels for firing bricks – US coal (10 tons per lakh bricks), firewood (3 tons per lakh bricks) and sawdust (3 tons per lakh bricks). Neighbouring Kiln B uses only US coal (14 tons per lakh bricks). Both are FCBTKs. Which kiln is more efficient? By calculating SEC of the kilns, we know that Kiln A has SEC of 1.23 MJ/kg, while Kiln B has SEC of 1.28 MJ/kg. This means Kiln A consumes less energy than Kiln B.

SEC gives you a more precise and realistic calculation of actual energy consumed by your kiln. SEC is a simple calculation, which can easily let brick kiln owners know their kiln’s energy consumption. BrickGuru has made the process easier by developing an online calculator to give you results in minutes.  Go ahead and calculate the SEC for your kiln.

To find out the SEC of your brick kiln, check out the SEC tool on the BrickGuru website today –

Before you start using the calculator, you should be ready with the following data for the season for which you wish to calculate the SEC –

  1. No. of months you operated your kiln
  2. How many types of bricks you produced
  3. Weight of all the types of bricks in kg
  4. Quantity of bricks produced of all the types (in tonnes)
  5. How many types of fuels you used
  6. Quantity of fuels used of all the types (in tonnes)
  7. Cost of all fuels used (Rs/ tonne).

Shifting to Cleaner Brick Technology: The Bihar Experience

The Bihar State Pollution Control Board’s (BSPCB) 2016 directive asking all brick kilns located in the 5 administrative blocks of Patna district to adopt cleaner brick production technologies has seen quite a few successes already. While it is true that there was some amount of starting trouble, many brick kiln owners were quickly able to adopt the changes and convert to the zigzag technology. Those who did are already seeing benefits from this shift.

Let us look at some quick trends. Out of 190 kilns that were under the purview of the BSPCB’s directive, 103 kilns (or 54% of the existing kilns) shifted to zigzag kilns during six months period of July to December 2016. Among this 76% adopted natural draft zigzag and 24% opted for induced draft zigzag technology. These upgraded kilns became operational during the brick production season of January–June 2017.

A survey of 66 kilns at the end of the first operational season showed that 68% kilns reported reduction in coal consumption and 72% reported improvement in the percentage of class-1 bricks and 57% expressed satisfaction with the adoption of zigzag kilns. However, 29% felt that though the technology is good, they have not been able to operate kilns satisfactorily due to various reasons and 14% were dissatisfied in the technology. It is interesting to note that the brick kiln owners who were unsatisfied with the adoption of zigzag kilns were also the ones who had poor quality kiln construction; absence of experienced workers; and limited understanding of the new technology.

While we have seen positive reactions, it evident that the shift is not free from challenges. The difficulties of technology upgrade in small and informal enterprises cannot be overlooked. Nor can skill gap amongst brick kiln owners and workers, and the time and effort it takes to monitor compliance. These are challenges that those converting will face but our advice to the brick makers would be to proceed with a structured plan to convert their kilns. They should prepare themselves by visiting better operating Zigzag kilns, they can also get information on Zigzag technology through websites like . After getting basic understanding they should hire a good contractor/mistri for constructing their kiln.

Over the past few months, we have witnessed several brick kiln owners transitioning to the new technology pretty smoothly. Initial troubles notwithstanding, brick kiln owners have shown great interest and initiative in reaching out for technical assistance as needed and ensuring the retrofitting is of high quality. They have also reaped the benefits of this very early on. Those who are yet to convert to the zigzag technology should look to these successful conversions to understand that the process is not as complicated as it might seem at the onset and there is plenty of support available to make the shift easier, and they stand to benefit by converting their kilns to Zigzag technology.

BRICKGURU: A One-of-a-Kind Digital Knowledge Source for a Transforming Building Sector

Bricks are essential building material in India and across most Asian, African, and Latin American and the demand for them is surging. In India demand for bricks has increased 8-fold in the last 40 years. This is likely to double again in the next 10 to 15 years. Bricks can be of many types: burnt clay, sun-dried clay, a variety of concrete, or bricks made from industrial waste like fly ash brick. Among these, burnt clay brick are the most popular and widely used.

Most of the burnt clay brick production takes place in small enterprises, located in peri-urban the rural areas. These enterprises provide livelihood to millions of families and play an important role in the rural economy. Traditional technologies and methods are used to manufacture them, but these methods were developed in an era when the volume of production was small and natural resources were abundant.  Today following the same traditional methods results in significant negative environmental and social impacts.

While new environmental norms and standards for brick production are being framed and implemented, the market for bricks is also changing. We are increasingly seeing new construction technologies such as monolithic construction technology, prefabricated concrete panels, and others come into use. Given increasing demand, there is pressure to construct buildings at a faster pace, and reduce water consumption and air pollution during construction. Recent introduction of the Goods and Services Tax (GST) and the government’s focus on digital payments clearly signal to the intent to move informal sectors, like brick production, towards formalization.

Given rapidly changing environment-social-market dynamics, transformation within the brick sector is imminent; and has already started in many ways. The big challenge now is how the industry, government, and society at large will work together to bring about this transformation in an orderly manner towards sustainability. This transformation can be deemed successful only if it creates a win-win situation for all the stakeholders, be it, brick producers, brick users, government, and citizens.

But what does “orderly transformation” mean in this context? For one, it is essential that all stakeholders have access to knowledge, and have necessary skills and capacities which would help them in negotiating this new process. That is where a digital platform such as BRICKGURU is essential. BRICKGURU aims to provide knowledge that is authentic, credible, crisp, and actionable to brick producers, brick users, and policy makers.

BRICKGURU builds on 25 years of action research work with the brick sector. The team behind the platform not only has experience on brick manufacturing but equally on sustainable building design and environment policy. BRICKGURU provides this knowledge through various mediums, such as, knowledge briefs, videos, case studies, and by providing a platform where practitioners can learn from each other. To build capacities of all stakeholders, it offers both online and offline training program and tools.

It the initial phase, BRICKGURU’s focus is on brick production, particularly on adoption of cleaner brick kiln technology. In coming months, knowledge pieces will be added on the manufacturing and use of a variety of resource-efficient bricks ranging from burnt clay hollow blocks and fly ash bricks to AAC blocks.

Launching BRICKGURU would not have been possible without financial support from several supporting organizations. BRICKGURU team has been very fortunate to be the recipient of knowledge, love, and support from a large number of stakeholders, we would like to thank each one of them and look forward to feedback and support from all the users accessing this site to make it better in the coming months and years.

Let us begin our journey towards a resource-efficient future.