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The glass manufacturing industry is a capital and energy-intensive industry, having one of the highest production volumes per capita around the world. The production of glass bottles is a complicated process involving the processes of batch preparation, melting, fining, refining, conditioning, forming, annealing, surface treatment, and inspection. Most energy in this industry is consumed in the melting and fining process. In the production of glass containers, the melting process consumes around 75 to 80 percent of energy.
We get raw materials from the earth. These materials are used to manufacture a product. It takes a lot of machinery and human energy to collect or mine raw materials. This includes cutting trees to produce paper or mining sand to produce glass. Glass is a mixture of three main raw materials: limestone, sand, and soda ash.
For the production of Dutch glass, approximately 550,000 tons of raw materials are used annually. Raw materials to make glass include soda ash- 17 percent, silica sand- 55 percent, limestone- 20 percent, and other materials. Natural gas is the main source of energy in melting, refining, and annealing processes.
First, let us understand what glass is. Glass is popular for its fragility and firmness, which makes it a typical type of solid. Glass is also a qualified liquid due to its somewhat fluid nature. Scientifically, glass is known as an amorphous solid, a state between two states of matter. Glass does not have thermal or electrical conductivity since it does not react with the commonly known chemical compounds.
There are three main types of glass. They include:
In the manufacturing stage of a glass bottle or product- energy and raw materials are the main inputs. To manufacture a glass bottle, the three major raw materials in producing glass, soda ash, limestone, and sand, are weighed and mixed into various batches with recycled glass and then heated to around 1500 degrees Celsius (2700 degrees Fahrenheit) to make a liquid mixture.
The molten mixture is then floated onto molten tin at a temperature of 1000 degrees Celsius. After the molten glass leaves the bath of molten tin, the glass then cools down to 600 degrees Celsius. It has cooled down enough to pass to an annealing chamber, generally called a lehr.
The glass then becomes hard enough to pass over rollers and is annealed. The process changes the internal stresses, enabling the glass to be cut and worked in a predictable way and ensuring the glass’s flatness. There is no need for polishing and grinding, as both the surfaces are fire-finished.
Once the liquid is cooled, the glass is prepared for use. The glass undergoes strict quality checks, is cleaned and treated properly, and a label is printed on it if required. The glass bottle is filled and used to hold a drink. Further, it is stacked, stored, and transported.
A glass bottle is sustainable, inert, and 100 percent recyclable, refillable, and reusable. Glass is impermeable and inert, making it the most stable packaging item. Food or drinks that are packed in glass have no potential risks of toxic chemicals. It does not need more barriers and additives. A glass bottle is 100 percent pure glass.
Twenty percent of all glass bottles are made of recycled glass. As long as the glass bottle is not damaged, broken, or chipped, it can last for as much time as needed. It never wears out. Several products are packed in glass bottles because of their values and properties. They include beer, soda, wine, perfumes, pickles, chemicals, pharmaceutical products, and other liquids.
During the useful life of a glass bottle, it is used for various intended and unintended purposes. Products designed, like glass bottles, for durable materials will have a longer and more useful life. This reduces the overall energy and resources needed to replace them.
Glass bottles have a shelf life even though they are fragile, break and crack easily. Glass has and will continue to be around for centuries, without any fear of polluting or damaging the environment.
According to the New Hampshire Department of Environment Service, estimates suggest that the life cycle of glass bottles is too long it takes up to 1 million years or more for a glass bottle to decompose in the environment. Decomposing in a landfill will take even longer. Glass artifacts from the beginning of Egypt’s glass-making industry around 2000 BC still exist.
Glass bottles and other items still exist from the history of glass making, whether they were buried in the soil, sunk in ships and boats, or carefully preserved by people. Glass changes its appearance after being buried due to chemical reactions. The glass gets an aesthetic look but doesn’t lose its strength. Depending on the composition, glass can either be brittle or strong. Even though modern glass is stronger than older glass, it does not affect the decomposition rate in dumping grounds.
Initially, glass was a unique and precious product as it took a lengthy and complex process for its manufacture and energy to melt the ingredients. Nowadays, new techniques allow for the mass production of glass bottles and products. Glass lends itself to indefinite recycling without losing its strength. Recycled glass goes into making other products like kitchen tiles etc.
Glass is generally recycled today. In 2011, Americans recycled over 3 million tons of glass. It was an increase from the 750,000 tons in 1980. Glass is usually discarded by color, cleaned, and then crushed. The different pieces of glass are then melted and reused to produce other glass products. A benefit of recycling glass is that manufactured glass melts much lower than raw materials. This saves a lot of energy in the next round of manufacturing. Exploring ways of reusing a product extends its life and can reduce the need to make more products.