Glassmaking: the energy transition lifts the sector's profile

With France having formulated a goal of carbon neutrality by 2050, all industrial sectors have begun to decarbonize. With a reputation for being carbon-intensive, the glass industry is not to be outdone: with 75 to 85% of carbon emitted during glass melting, its players want and need to reduce production-related emissions.

The challenges faced by the glass industry are in part the same as those faced by other manufacturers. But its energy-intensive machinery makes it particularly price-sensitive. A vulnerability accentuated by rising energy prices.

Samuel Joachim, Director of Innovation and Development at Verescence, asserted that " Lighter glass is the most powerful lever for reducing our environmental footprint ".  While the use of recycled glass or cullet is not new (glass has the fascinating fact that it can be recycled ad infinitum), it is no longer enough.

The avenues for manufacturers to explore are now widely diversified, from eco-design of glass and equipment, to production flows, but also to more behavioral and organizational factors in operations.

Overview of the issues and levers available to players of excellence, which France is fortunate to have on its soil - particularly in the Glass Valley.

Energy optimization opportunities and solutions from the design stage

They can come into play at 2 distinct moments :

Eco-design of glass

Trends include :

• The refill : some renowned perfumers like Chanel and Guerlain have switched to recycled glass for their bottles and offer refill containers. Some bottles even have their components (insert, weight, liner, magnets) separable at the sorting center, to optimize recycling ;
• The replace : manufacturers are pushing back the limits of glass in terms of mechanical resistance, and investing territories where this material is not traditionally present. For example, they are using polymer coatings, which can also be sorted and recycled, and are working on hot glass surface treatments to reinforce its resistance at source ;
• The use of stretched glass which is becoming more widespread at the expense of molded glass. 6 to 7 times lighter, it has a significant impact on bottle weight and transport costs.

Furnace construction

A glass furnace traditionally runs on gas. In particular, it is equipped with a " breeder ", which it uses to heat the suction fumes it produces. If the technical choices of yesteryear didn't bother anyone for decades, today they're being seriously called into question.

The manufacturers of this equipment are going to have to put the concern for energy savings back at the heart of their design policies. This is already leading them to the total or partial electrification of ovens.

However, energy-efficient ovens are still in the spotlight.

However, electric or hybrid ovens do not yet offer the level of performance of their traditional counterparts, for both technical reasons and the adoption of new practices. Manufacturers' R&D departments are working on the emergence of new technologies, new materials and novel alloys, such as CP1 developed in collaboration with Constellium for 3D manufacturing[1].

Optimization opportunities and solutions in the production phase

So much for the future... But in most cases, we'll have to make do with an installed and sometimes old or even obsolete furnace. The reality of the installed base is leading manufacturers down curative paths to optimize their energy mix. If glass industry equipment is energy-intensive, it's also because it's powerful, and that power is necessary. There's a glass ceiling beyond which it's difficult to act, except to reduce production and close furnaces.

Two main levers : regulation and heat recovery

• The first lever consists in optimizing machine settings to adjust usage to real needs. The rule of " who can do more can do less " is common when it comes to energy usage. Let's take the example of a baking oven. To achieve the required thermal levels, it is essential to finely regulate aeraulic flows. However, in practice, operators tend to prefer the usual usage, which they believe will guarantee comfortable operation.

• The second lever is to recover waste heat. Furnace exhaust fumes harbor a great deal of thermal power. One solution is to recover this rejected heat (also known as " fatal "), by installing heat exchangers. It can then be reused to supply other substations or district heating networks. Another option is to install an ORC (Organic Ranking Cycle) system, which produces electricity from the flue gases. However, switching it on is not trivial, and involves shutting down the furnace. It's important to note that in glassmaking, a furnace runs continuously, i.e. every day of the year: it's only stopped for maintenance purposes. This solution is therefore more complex to implement.

Other levers

Beyond these sources, there are other, more diffuse ones. They depend above all on the structure of the plant and what it produces :

• Heat can be recovered from the " hot end ". As a reminder, the hot end is the system sending molten glass to be cast into the desired form (bottle, glass...). The cold end, on the other hand, is used for downstream operations such as bottle inspection, palletization, etc. This recovery takes place via " feeders ", i.e. the molten glass circulation channels, themselves producers of significant heat ;
• It's also possible to collect heat from the plant's chillers. On a practical level, in the " hot end " section, a correct temperature must be maintained for production and operators. This is achieved by means of chillers, which themselves consume energy to guarantee the right temperature level. The energy saved can then be recovered for water preheating;
• Air compressors are also another source of heat production ;

Finally, industrialists are free to make all kinds of modifications to their equipment. We're talking about insulating a factory roof, installing a cooling system, or significantly improving the insulation of their furnaces. This last option comes before considering their electrification or even replacement by models of a higher generation.

Behavioral and organizational issues

Implementing energy savings is a complex process that needs to be carried out on a case-by-case basis, depending on the plant's configuration and in-depth knowledge of it. It's also essential to raise awareness of certain practices among the industry's employees, such as the proper management of pressure levels for compressed air. There's a whole process of change to be supported in this area, and glass plant maintenance managers are in the best position to do so. Because of their experience of the production site, they are the only ones able to produce such specific findings.

We're here at the heart of equipment usage and behavior, which goes beyond technological choices. It's this global approach, including all energy-saving levers, that characterizes Lemon Energy's services.

Lemon Energy's approach is based on a global approach, including all energy-saving levers, that characterizes Lemon Energy's services.