Decarbonization Strategies for the Glass Industry

Although the momentum has slowed in recent years, a large share of leading companies around the world have set bold decarbonization targets, and in the coming years, many will need to tackle the Scope 3 emissions linked to the materials embedded in their products. This article, which focuses on glass—particularly the flat glass industry—is part of a series of articles on how materials industries can decarbonize and increase circularity, offering an overview for companies within materials value chains and for companies downstream.

Introduction

Glass forms an integral part of many industrial value chains, from construction and automotive to homeware, packaging, and electronics. Glass production is also a significant source of emissions: As of 2022, more than 150 million metric tons (Mt) of glass (of which about 40 percent is flat glass) are produced each year globally, with an estimated annual life cycle emissions footprint of approximately 150 MtCO₂, assuming an average of one tCO₂ per metric ton of glass produced.

Decarbonization challenges in the glass industry today

Many decarbonization levers exist for flat glass, from hydrogen and biogas to carbon capture and storage and electro-boosting. However, three main challenges currently prevent the widespread implementation of these decarbonization levers in the flat glass industry:

• Technological maturity. While several levers that result in a partial decarbonization of operations are mature and scalable today, most of the levers required to fully decarbonize operations are dependent on technology that has not yet been deployed at commercial scale.
• Cost competitiveness. An assessment of the cost of decarbonization technologies shows that most of the impactful technologies are not yet as cost-competitive as conventional technologies are, even in regions that have already put in place a carbon tax, such as Europe.
• Furnace lifetime. Glass furnaces run continuously for a period of several years (often more than a decade) before they are taken offline for a “cold repair.” While glass producers have some flexibility in adapting the throughput of the furnace, the furnace cannot be shut down without the need for a costly investment to bring it back online. As such, the industry preferably matches the switch toward low(er)-carbon technologies with the existing cold-repair schedules to reduce costs and limit business interruptions.

Emissions vary across the value chain

Emissions are split across the glass value chain:

• Raw materials. Approximately 20 to 25 percent of emissions come from upstream production (mining, quarrying, processing, and so on) of materials such as silica sand, soda ash, and limestone.
• Mixing, melting, and forming. Approximately 65 to 70 percent of emissions come from the melting process, which requires temperatures of 1,200°C to 1,500°C or more. Out of these emissions, 20 to 25 percent are intrinsic to the chemical process and directly related to the use of soda ash and limestone as raw materials.
• Downstream processing. Approximately 5 to 15 percent of emissions come from downstream processing, including annealing and cutting.
• These estimates exclude transportation emissions, which vary widely based on the location of raw material suppliers, glass producers, and customers.

Emissions also vary by player

There is a wide spread in Scope 1, 2, and 3 emissions intensity between the lowest- and highest-emitting players in Europe. These differences are caused by five main drivers:

• Raw materials: use of different types of raw materials (notably synthetic versus natural soda ash), which themselves can be produced using different technologies
• Melting technology: the energy source used in the melting process, especially the relative share of natural gas and electricity
• Energy efficiency: use of energy efficiency measures in the melting process, such as preheating of the raw material batch, heat recovery, or oxyfuels
• Cullet rate: relative use of recycled glass (called “cullet”) versus virgin materials, which lowers energy consumption and avoids the release of process emissions
• Glass type: the type of glass that is being manufactured—for instance, cover glass for electronics requires raw materials (such as alumina) and downstream processing that are different from the flat glass used in construction and automotive sectors, resulting in an overall higher emission intensity

Abatement levers are available to decarbonize glass feedstocks and production

Producers have several options to reduce emissions from upstream raw material feedstock production and glass production—options that go beyond the energy efficiency levers outlined above.

For raw materials, the majority of emissions stem from the production of synthetic soda ash. Several levers exist to reduce emissions stemming from soda ash, including the following:

• Recycled glass: increased use of cullet as a substitute for soda ash, which fully eliminates the emissions resulting from the soda ash production process
• Natural soda ash: substitution of synthetic soda ash with a natural counterpart (trona) that can be produced at a lower emission intensity, the supply of which is currently concentrated in the United States, China, and Turkïye
• Low-carbon soda ash: a shift toward an alternative low(er)-carbon production process for synthetic soda ash

For glass production, the majority of emissions result from the heating of furnaces with natural gas and the release of process emissions from raw materials. Abatement levers include the following:

• Recycled glass: increased use of cullet as a substitute for soda ash, which avoids the release of process emissions during the smelting process
• Alternative heating methods: substitution of natural gas with biogas (which can be done without changes to the furnace design) or with electricity or hydrogen (both of which require changes to the furnace design)

In addition to these levers, producers could choose to capture and store or reuse the carbon that is released during the production process.

Maximizing the use of cullet in the raw material batch in combination with using biogas, hydrogen, or electricity in the furnace could jointly enable greater than 90 percent decarbonization at the asset level. For example, a leading glass company achieved close to 100 percent decarbonization by combining cullet and biogas in a pilot test. The company also formed a technological partnership to achieve more than 75 percent decarbonization in a smaller-scale float by maximizing cullet use and implementing a novel design for a hybrid natural gas–electricity furnace.

These pilots show that there are several technological pathways to full decarbonization of glass production at the asset level. However, there are limitations to the scalability of these solutions for the entire industry due to limited availability of feedstock. For example, cullet can cover only about 10 to 15 percent of virgin raw material demand, and biogas is not always readily available in the vicinity of existing floats.

Cullet (recycling) rates stand to be much improved

For many decarbonization levers, cost competitiveness strongly depends on the location of the asset and carbon policies. By contrast, using cullet can be more cost-effective than virgin raw materials in most regions, especially in densely populated areas close to float operations. In a scenario where the float is running exclusively on cullet, Scope 1, 2, and 3 emissions could be reduced by 30 to 40 percent.

Despite this, the average recycling rate for flat glass is currently only about 20 percent in Europe, according to McKinsey analysis. The reason for the low recycling rate is twofold:

• Lack of flat glass waste collection. In many countries, there is no postconsumer collection system for flat glass, so flat glass waste ends up in landfills.
• Downcycling into other glass applications. Flat glass has much more stringent quality constraints—such as lower tolerance for ceramic inclusions and more stringent specifications on chemical composition—than packaging glass. Therefore, contaminated, postconsumer flat glass cullet is typically downcycled into packaging or other applications with less stringent quality constraints.

As such, unlocking the full potential of cullet as a cost-effective decarbonization lever will require the setup of new supply chains that enable economical collection of flat glass and reduce the risk of contamination. This could be achieved through initiatives such as return schemes between glass installers and producers or national collections schemes (for example, similar to the Netherlands, where flat glass collection rates are about 75 percent, according to McKinsey analysis).

Main Actions to Accelerate Decarbonization

There are three main actions that could accelerate decarbonization in the flat glass industry:

• Set up new cullet value chains. More than 80 percent of flat glass in Europe currently ends up in landfills. A large share of this could be recovered economically by setting up new “reverse” value chains that avoid contamination of glass with other materials and ensure separation of glass types to limit downcycling.
• Double down on technological innovation across the value chain. The industry will have to double down on maturing low-carbon technologies that have the potential to become cost-competitive alternatives to conventional technologies.
• Invest in cross-industry partnerships. Collaboration across industries can improve the cost-effectiveness of decarbonization technologies.

Conclusion

Doubling down on decarbonization actions could enable first movers to develop unique competitive advantages, such as access to raw materials, cutting-edge technology, and reduced exposure to future carbon taxes. However, creating the future glass industry will take collaboration and a value chain approach to truly scale solutions and build circularity—and value—for everyone.

FAQ

What is the current recycling rate for flat glass in Europe?

The average recycling rate for flat glass in Europe is currently about 20 percent, according to McKinsey analysis.

What are the main challenges facing the decarbonization of the flat glass industry?

The main challenges include technological maturity, cost competitiveness, and furnace lifetime.

How can the glass industry reduce its emissions?

The glass industry can reduce emissions by increasing the use of cullet, adopting alternative heating methods, and investing in carbon capture technologies.