Glass or plastic: which is better for the environment? – 05/21/2023 – Environment

The Speyer bottle, which dates back to the period between 325 and 350 AD, is considered to be the oldest wine bottle in the world. It is part of the collection of the Speyer Wine Museum, the German city where it was discovered in 1867.

Analysis of its contents revealed that it contains an ethanol-based liquid. But the glass bottle remains unopened — and the vintage is unknown.

Winemakers on duty should be careful before applying to taste it, as the flavor of drinks preserved throughout history can be pungent, to say the least.

The widespread use of glass as a storage vessel throughout human history is a testament to the material’s durability and functionality.

Glass is used for just about everything, from preserving food to conducting signals for the internet. It is so essential to human development that the United Nations has designated 2022 as the International Year of Glass, celebrating its contribution to scientific and cultural development.

Glass is often referred to as a material that can be infinitely recycled without impairing its quality, purity or durability. Discarded glass can be broken into small pieces, melted down and used to make more glass.

Glass used in packaging has a higher recycling rate compared to other materials used for the same purpose. In Europe, the average recycling rate for glass is 76%, compared to 41% for plastic packaging and 31% for wooden packaging.

When glass is kept in the natural environment, it tends to cause much less pollution than plastic. After all, glass isn’t toxic—unlike plastic, which breaks down into microplastics that can seep into soil and water.

“Glass is mainly made of silica, which is a natural substance”, says Franziska Trautmann, one of the founders of the company Glass Half Full, from New Orleans, in the United States. The company recycles glass by turning the material into sand, which can be used to restore coastlines and disaster-impacted areas.

Silica, or silica dioxide, makes up 59% of the Earth’s crust. And, as it is a natural compound, there is no concern about its leaching or environmental degradation.

For all these reasons, glass is often referred to as a more sustainable alternative to plastic. But the environmental footprint of glass bottles is greater than that of plastic and other materials used for packaging, such as aluminum cans.

Silica sand mining can cause significant environmental damage, ranging from land degradation to loss of biodiversity. And violations of basic workers’ rights were also uncovered in Shankargarh, India—the largest supplier of silica sand to that country’s glass industry.

Studies show that prolonged exposure to silica dust can pose risks to public health. It can cause acute silicosis, a chronic and irreversible lung disease caused by inhaling silica dust for extended periods.

Silicosis may initially appear with a persistent cough or shortness of breath and may result in respiratory arrest.

The extraction of sand for the production of glass may also have contributed to the current scarcity of sand on the planet. Sand is the second most used resource in the world, after water.

Humans consume about 50 billion tons of “aggregates” (an industrial term for sand and gravel) every year. Its uses range from regenerating the earth to making microchips. And according to the United Nations, sand is currently consumed faster than it can be replaced.

Glass requires higher temperatures than plastic and aluminum to melt and be shaped, according to researcher Alice Brock, a doctoral student at the University of Southampton, in the United Kingdom. And the raw material for making raw glass also releases greenhouse gases during the melting process, which increases your environmental footprint.

According to the International Energy Agency, the flat glass and packaging industries emit more than 60 megatons of CO2 per year. It may come as a surprise, but Brock’s study concluded that plastic bottles do less harm to the environment than glass bottles.

Plastic cannot be recycled infinitely, but its manufacturing process consumes less energy, as the melting point of plastic is lower than that of glass.

The raw material for glass is melted in a furnace at 1500 °C. The molten glass is then taken out of the furnace and shaped. And glass production plants often add a percentage of recycled glass fragments to the raw material mix.

Generally, adding 10% recycled glass to the melting mix can reduce energy consumption by 2% to 3%. This is because a lower melting point has to be achieved to melt recycled glass compared to the original raw material used to manufacture glass. And this reduction slightly decreases the CO2 emissions produced during the process.

A major problem with glass recycling is that it does not eliminate the melting process, which is the most energy-consuming part of production. Melting accounts for 75% of energy consumption during glass manufacturing.

And while glass containers can be reused an average of 12 to 20 times, glass is often treated as a disposable material. And glass discarded in landfills can take up to a million years to decompose.

Glass recycling rates vary significantly around the world. The European Union and the United Kingdom, for example, have average recycling rates of 74% and 76%, while in the United States this index was 31.3% in 2018

One of the reasons for the low American rate is that, in the United States, recycled material is usually collected in a single stream, which means that all materials are mixed together.

Single stream recycling often makes the sorting process difficult. Glass needs to be separated from other recycled materials and sorted by color before the casting process. And it’s usually very expensive and time-consuming to sort glass of different colors at a recycling plant.

So instead of turning into new bottles, the mixed pieces of broken glass are turned into fiberglass products, which can be used for insulation.

Broken glass for recycling is of better quality when separated from other recyclable materials from the beginning, in so-called multi-stream recycling.

The color of the glass affects the purity required for the flux. Green glass, for example, can use 95% recycled glass. But clear or clear glass (also called “flint glass”), has higher quality specifications and allows for the inclusion of only 60% recycled glass, as any contamination affects the quality of the material.

Recycled glass needs to be melted twice, first into small pieces and then into the new product. Therefore, the difference in energy consumption for the production of recycled glass can be very small compared to new glass.

Undoubtedly, glass continues to play an important role in many industries. Its durability and non-toxic properties make it ideal for food and materials that need to be preserved.

But the assumption that glass is sustainable just because it is infinitely recyclable is unfounded. Considering the entire use cycle of glass, its production can be as harmful to the environment as plastic.

So the next time you want to throw away a glass bottle, think about reusing it first. Glass is a durable and resistant material. It is not meant to be thrown away after one use.

This text was originally published here.