Over the past twenty years, glass demand has grown more quickly than GDP and is still growing at nearly 4% per year. About 0.5-0.8 EJ of energy is used for glass production worldwide, and the energy used in the production of container and flat glass results in emissions of about 50-60 Mt CO2 per year.1,2 With the adoption of best available technologies, energy efficiency of the sector can be improved by as much as 40% in developing countries and up to 35% in industrialized ones, collectively presenting an energy saving potential of around 0.6 EJ/year.3

Glass is produced by melting raw materials (mainly silica sand, soda ash and limestone), and often cullet (recycled container glass or waste glass from manufacturing) in glass furnaces of different sizes employing different technologies. Glass products and their characteristics, as well as the production and processing routes involved in their production show large variations. However, batch preperation, melting and refining, conditioning and forming, and finishing (annealing, tempering, polishing or coating) steps are found in virtually all glass plants and are the most important from an energy point of view. 

Melting furnaces – employing combustion-heating (with air-fuel or oxy-fuel burners), direct electrical heating, or a combination of the two (electric boosting) – are the major energy users. In general, the energy necessary for melting glass may account for over 75% of the total energy (in terms of final energy) requirements of glass manufacture, with an average of about 65% of the total energy input when considering all the sectors of the glass industry.4 Typically, melting furnaces operate with an overall efficiency of 50-60%, where structural and flue gas losses represent 20-25% and 25-35% of losses, respectively.2 Melting furnaces are also the most important area for efficiency improvement, followed by refining and conditioning.5

Improved process control, increased cullet use, increased furnace size, use of waste heat in batch and cullet preheating or in steam generation, use of oxy-fuel technologies, and reduction of rejects are the major energy saving efficiency opportunities for the sector.2


motor system

Glass Publications

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Glass Reference Documents

Best Available Techniques (BAT) Reference Document for the Manufacture of Glass

As a reference of the EU Industrial Emissions Directive (2010/75 EU) this new version provides extensive information on Best Available Techniques (BATs) applicable to European Glass Manufacturing Industry for reducing environmental impact. The document is prepared by the  Institute for the Prospective Technological Studies of European Commission's Joint Research Center. 

Although the theoretical minimum energy use is 2.8 GJ/t for soda-lime glass and 2.35 GJ/t for borosilicate and crystal, in practice average energy use varies between 5.75-9 GJ/t. 

Energy intensity in glass furnaces can show high variations, depending on the size and technology of the furnace and the amount of cullet used. Based on analysis for 123 container glass and 23 float glass furnaces the energy intensity of continuous glass furnaces in Europe and the United States were reported as 4-10 GJ/t of container glass and 5-8.5 GJ/t of flat glass. The most energy efficient furnace identified in this study shows an energy consumption of 3.82-3.85 GJ/t, based on 50% cullet and taking into account the primary energy consumption for electricity generation.2

As different glass products have different characteristics and different production routes, significant variations are also observed in the energy requirements of different glass products. In the table below, typical specific energy consumption values attained with the use of energy efficiency measures are provided.


Typical Specific Energy Consumption Values Achieved by Applying Available Energy Efficiency Measures/Techniques1
Sector Furnace Type/Capacity Furnace Energy Consumption
(GJ/tonne melted glass)
Overall Energy Consumption
(GJ/tonne finished product)
Container Glass
Bottles & Jars <100 t/d 5.5 – 7 <7.7
>100 t/d 3.3 – 4.6
Electric furnaces 2.9 – 3.6


<100 t/d 7 – 9 <16
>100 t/d 4.8 – 6
Flat Glass
  All capacities 5 – 7 <8
Continous filament glass fibre
  All capacities 7 –14 <20
Domestic glass
  Conventional furnaces   < 24 for capacities < 100 t/da
< 18 for capacities > 100 t/d
  <100 t/da 6.7 – 9.5
  >100 t/d 5 – 6
  Electric furnacesb 3.4 – 4.3
Special glass
All products Electric furnacesb 3.9 – 4.5 20 <
Soda-lime glas Conventional furnaces 5 – 10
Borosilicate glass 10 – 15
Mineral wool
Glas wool All capacities 2.7 – 5.5 < 14
Stone wool All capacities 4.2 – 10 < 12
High temperature insulation wool
  All capacities 6.5 – 16.5 < 20
  Oxy-fired furnaces  ≤ 9  
  Air/fuel & enriched air/fuel furnaces  ≤ 13  

a : Values do not include installations equipped with pot furnaces or day tanks which energy consumption for the melting process may be in the range of 10 – 30 GJ/tonne melted glass.
b: Data reported refer to energy at the point of use and are not corrected to primary energy.


Benchmark Footnotes: 


The Institute for Prospective Technological Studies/European Commission (2013). Best Available Techniques (BAT) Reference Document for the Manufacture of Glass. p. 310.

The glass industry is divided into four major segments. These segments and their approximate market shares, as of 2008, are as following:

  1. Container glass (45 %)
  2. Speciality glass (33 %)
  3. Flat glass (16 %)
  4. Fibre Glass (6 %)6

Even though flat glass accounts only about 16% of the global glass industry, most information on market structure focus on this segment. The global market for flat glass in 2010 was approximately 56 million tonnes. This is dominated by Europe, China and North America, which together account for around three-quarters of global demand for flat glass. Of total global market demand in 2010, it is estimated that 33 million tonnes was for high quality float glass, 1 million tonnes for sheet glass and 2 million tonnes for rolled glass. The remaining 20 million tonnes reflects demand for lower quality float, produced mainly in China. The significance of China as a market for glass has been increasing rapidly since the early 1990s as the country has become more open to foreign investment and the economy has expanded. In the early 1990s China accounted for about one fifth of world glass demand, but now accounts for 51%7.

Global Float Glass Demand

The glass industry is dominated by set of large manufacturers active primarily in the flat-glass and glass-container sectors.

Since the 1960s, the glass industry as a whole has reduced specific energy consumption by approximately 1.5 % per year. Today this figure is lower, as the thermodynamic limits are approached8.

This section provides information on the various international and national organizations that focus on energy efficiency in the glass industry.

Glass Organizations Global

Glass Organizations Australia

Glass Organizations Brazil

Glass Organizations China

Glass Organizations European Union

Glass Organizations Europe

Glass Organizations India

Glass Organizations United States

Glass Organizations Japan

Glass Organizations Russia

Programs Description: 

This section contains information on the various international and national programs that focus on energy efficiency in the glass industry.

Glass Programs Australia

Glass Programs European Union

Glass Programs India

Glass Programs Japan

Glass Programs United States

Energy Management System Structure

Industrial energy efficiency can be greatly enhanced by more effectively managing plant operations and processes. Experience shows that companies and sites with stronger energy management programs gain greater improvements in energy efficiency than those that lack good procedures and management practices focused on the continuous improvement of energy performance.
An Energy Management System (EnMS) provides a framework to manage energy use and promote continuous improvement. It helps with assessment, planning, and evaluation procedures, all of which are critical to realizing and sustaining the potential energy efficiency gains of new technologies or operational changes.
A sound energy management program is required to create a foundation for positive change and provide guidance on managing energy throughout an organization. Continuous improvements to energy efficiency therefore typically only occur where there is strong organizational commitment. The key elements of a strategic EnMS is depicted in the figure on the right. 
There are a number of guidelines aimed at helping companies to establish an effective EnMS - including from the United States Environmental Protection Agency (US EPA) and the recent ISO 50000 series by the International Standards Organization. Although the details differ, these guidelines promote continuous improvement of energy efficiency through: 
  • organizational practices and policies;
  • team development;
  • planning and evaluation;
  • tracking and measurement;
  • communication and employee engagement and;
  • evaluation and corrective measures (US EPA, 2010).

While an EnMS can help organizations achieve greater savings through a focus on continuous improvement in energy efficiency, it does not guarantee energy savings or carbon dioxide reductions. To achieve cost savings, an EnMS must be combined with effective plant energy benchmarking and appropriate plant improvements. 

This page will be updated with examples of EnMs implementation in the glass industry. 


Emissions are likely to be in excess of 75 Mt CO2/year when the emissions from the decarbonisation of soda ash and limestone are also included (IEA, 2007. p. 168)


International Energy Agency (2007). Tracking Industrial Energy Efficiency and CO2 Emissions. p. 168. 


United Nations Industrial Development Organization (2011). Industrial Energy Efficiency for Sustainable Wealth Creation - Capturing environmental, economic and social dividends. p. 84.


The Institute for Prospective Technological Studies/European Commission (2013). Best Available Techniques (BAT) Reference Document for the Manufacture of Glass. p. 310.


Worrell, E., Galitsky, C., Masanet, E, and Graus, W. (2008). Energy Efficiency Improvement and Cost Saving Opportunities for the Glass Industry – An ENERGY STAR® Guide for Energy and Plant Managers. p. 23.


India Brand Equity Foundation (2008). Glass and Ceramics Market and Opportunities. p.2.


NSG Group (2011). NSG Group and the Flat Glass Industry 2011. p. 11.


The Institute for Prospective Technological Studies/European Commission (2013). Best Available Techniques (BAT) Reference Document for the Manufacture of Glass. p. 94.