Recycling glass burns fossil fuels. Are refillables greener?

Fossil gas powers the large furnaces in Auckland that melt used glass containers and transform them into new ones.

In addition, the chemical reaction to create glass releases more carbon dioxide, which blankets the atmosphere.

To avoid these emissions, a group of sustainable companies want the Government to introduce a container reuse system, where bottles and jars are washed and refilled.

In Christchurch, used glass containers are “downcycled” into road material. Crushed glass can replace the aggregate and sand required for asphalt.

Glass containers in other recycling bins are often sent to Auckland. Australasian recycling company Visy operates a glass-making factory in Penrose, the largest in the country.

To create recycled glass, furnaces must reach about 1500C – in Auckland, that’s fuelled by fossil gas. Some additional equipment is electrical.

This combustion creates the bulk of the Auckland factory’s carbon footprint. But there’s another source: the chemical reactions in the furnace itself.

Used glass is combined with chemicals including soda ash, limestone and dolomite. Each of these substances contains some stored carbon dioxide.

This greenhouse gas is released during the reaction, entering and warming the atmosphere. From this process alone, the Auckland glass factory produced 11,700 tonnes of carbon dioxide in 2020 – the equivalent of more than 1650 return flights to London.

Glass factories can reduce these emissions by using a higher proportion of used glass. This also allows the furnace to run at a lower temperature, saving fuel.

In 2019, the Auckland factory made 10 million bottles from 90% recycled material. But day-to-day, Visy aims for 70% recycled content. The recycled share might be limited by the supply of used glass or the quality demands of customers.

Amber or green glass often has a higher proportion of recycled content than clear containers.

The glass-making process also creates toxic air pollutants that can contribute to asthma and bronchitis. Air quality systems can scrub some of these contaminants out of the air before it leaves the smokestacks. These emissions have decreased significantly in recent years.

Visy’s Australian head office was contacted multiple times, and asked about any plans to replace fossil fuels or further reduce process emissions. The press office did not respond.

Lower-emissions bottles

Last month, a French glass-maker manufactured the world’s first zero-carbon recycled glass: using 100% used glass – and therefore no carbon-releasing compounds – with furnaces powered by biogas. But the adjusted furnace ran for just one week.

This type of glass could hinge on company and consumer acceptance: bottles with higher recycled content can have a slight colour tinge.

Over here, the Government is planning to pay people to return beverage containers made of glass, plastic and aluminium. It’s expected to start in 2025, where you’ll receive about 20 cents per container cash back to drop it off at a designated machine.

Each year, Kiwis buy 2.3 billion single-use beverage containers. The Government hopes the cash-back system will achieve far higher collection rates. But as it’s currently proposed, the containers will be sent for recycling – glass (and aluminium) to an emissions-intensive furnace.

Sustainable business leaders are calling on the Government to build a reuse option into this system. Standardised bottles and jars made of glass and plastic could be diverted to a washing, de-labelling and sanitising facility. Food companies could then purchase the reusable containers.

The system could be a low-carbon showcase, they say: using zero-emissions trucks, solar power and wastewater recovery.

Currently, the ABC Swappa Crate system for beer is the country’s largest reusable container scheme, with 30 million bottles.

Florence Van Dyke, the co-founder of beverage company Chia Sisters, wrote an open letter to the Government, calling for a reuse option for the wider drinks industry.

Boosting recycling is very important, she added. But in a circular economy, reuse should be the priority. “The proposed container return scheme provides a real opportunity, because no small business can do this alone.”

The letter was signed by a number of other food companies – such as Fix & Fogg, Phoenix Organic, Six Barrel Soda and Wai Manuka – and climate experts, including Climate Change Commissioner James Renwick.

Hard plastic containers can be washed and reused between 10 and 20 times, and glass up to 50 times, Van Dyke said. “It would have so many climate and other environmental benefits.”

Refilled bottles could look scuffed, compared to their single-use counterparts. Van Dyke said this would indicate to shoppers that a company is prioritising the planet over aesthetics. “Consumers, especially our tribe, understand and expect that re-used items aren’t 100% perfect.”

Transport costs could be higher. Used glass sent to the furnace can be transported in shards. Reusable glass bottles take up more space, requiring more trucks.

Van Dyke said consumers – through taxes and rates – are paying for recycling and landfills, and the associated emissions, instead of the companies who choose the packaging. “When we internalise all of these costs, it is much cheaper to reuse.”

She hoped a reuse system would reduce the waste material shipped to developing countries. This is sold as recycling, but reports have found much is being illegally dumped or burned. “It’s just not right to be relying on other countries to be dealing with our waste.”

Recycling vs reuse

Lifecycle studies – which add up all the sources of emissions throughout a product’s life – found glass reuse is preferable to glass recycling.

Barbara Nebel, the chief executive of Thinkstep-ANZ, a lifecycle consultancy, said that reusable glass bottles would typically be a little heavier than single-use options. That weight could mean more fossil fuel is burned transporting the product, she added.

But even accounting for the extra weight, reused bottles produced significantly fewer emissions, one study found – providing each are used up to 6 times and a small fraction break or are lost.

According to a report based on 32 lifecycle analyses, a reused glass container produces less than one-sixth of the carbon emissions of a recycled one.

The report said that if the containers travelled less than 100km, reused glass was the lowest-emissions option.

In the past, beverages – such as beer and soft drinks – were predominantly made or bottled in local factories. Under these systems, refillable glass bottles made economic and environmental sense. But manufacturing has been streamlined, with many Kiwi drink companies producing products for the whole country out of a single factory.

For companies using glass containers, bottling is most likely to be done in Auckland, near the glass facility.

When beverages travel more than 100km from the factory to customers, single-use cartons – which are predominantly made from carbon-absorbing paper, weigh less and can now be transformed into building materials – are the greenest option.

Nebel’s company also found cartons and recycled PET to be good low-carbon packaging choices. “It had to do with the weight… The weight is quite important.”

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