Tetra Pak has become the definitive term for what should, rather more prosaically, be dubbed the ‘beverage carton’. Unsurprisingly, Tetra Pak happily acknowledges this, while competitor SIG Combibloc is adamant that the latter is the correct term. Yet Sveinar Kildal, the director of environmental affairs at Tetra Pak’s other main rival, Elopak, concedes that: “Tetra Pak has become a generic name for all beverage cartons”.

However, semantics to one side, Tetra Pak, SIG and Elopak have formed an alliance under the banner Alliance for Beverage Cans and the Environment (Ace). Ace UK represents the UK market, where beverage cartons are a staple form of packaging in most households. But their ubiquity belies the fact that not many people know how Tetra Paks are manufactured.

They could turn to the pages of the Oxford English Dictionary, which goes part of the way towards explaining how they are made – as well as affirming that ‘Tetra Pak’ has become the generic term for beverage cartons: “A type of plasticised cardboard carton for milk and other drinks, folded from a single sheet into a box shape,” it reads.

This may go some way to explaining how Tetra Paks are made, but how is the board manufactured? How is it converted? And what happens once a consumer has finished with the carton and thrown it in their recycling bin?

MATERIALS
Broadly speaking, explains Richard Hands, Tetra Pak UK and Ireland’s environment manager, there are two types of Tetra Pak, and typically both are made from 75% paperboard.

Firstly, there are those used to package refrigerated food and drinks. They are made from paperboard and between 10% and 25% of low-density polyethylene (LDPE). An inner polymer layer acts as a liquid barrier, while an outer layer keeps out moisture, which is prevalent in refrigerated conditions.

Secondly, there are aseptic packs used to package long-life products at an ambient temperature. These incorporate a thin layer of aluminium foil (typically 5%).

“Essentially it’s a lightweight can,” explains Hands. The pack’s integrity is maintained by the stiffness of the paperboard. The foil is just 6 microns thick, which Hands says is “as thin as technically we can get and still have the foil function as a barrier”.

The industry’s paperboard suppliers are based in the Nordics, where mills can source principally from the surrounding forests. There are two main suppliers – Korsnäs and Stora Enso in Sweden – as well as Imatra in Finland. Together they supply 98% of the total volume used by Ace UK members.

Tetra Pak is constantly looking at ways of improving processes in order to get more out of materials. For example, it recently pioneered a lighter board weight with customer Innocent Drinks.

However, Hands stresses that there are limits to reducing material usage: “If you lightweight too much, then [packs] start to look different,” he says.

CONVERSION
Tetra Pak’s conversion process was developed more than 50 years ago and has remained fundamentally unchanged ever since. It starts with a large roll of paper “several feet wide,” says Hands. This paper is then printed.

The material is laminated with plastic and aluminium foil. Then the roll is cut, using slitters, into single-pack-width reels – these are complete with creases for the ‘origami’ of the pack. The product is then delivered to the company’s customers.

The rolls can be stored at customers’ sites until they are ready to be filled with a Tetra Pak-manufactured filling machine. Once a reel is hooked on to it, the machine forms and seals the cartons in a continuous process.

Although the principles of the conversion process are the same as they were half a century ago, carton manufacturers are constantly examining ways that they could be refined.

“One step-change was when [in 2004] we moved to a different formulation of polymer lining called Tetra Wide, which uses up to 30% less polymer lining and allows us to cut our non-renewable resources,” says Hands.

Tetra Pak is also well on track to cut its CO2 emissions by 10% by 2010, compared with 2005. The company’s focus on energy efficiency and using renewable energy has played a large part in this success. “We have several plants running off renewable energy in continental Europe,” says Hands.

DISPOSAL
In the UK, 86% of local authorities have a carton collection system in place – either kerbside, which 19% of councils have adopted; or bring-banks, a system 67% of authorities have employed.

The latter is generally preferred by carton manufacturers – who have been instrumental in its implementation under the Ace UK umbrella – because it gives them more control over the recovery and recycling of cartons, whereas kerbside collections end up in local authorities’ particular recovery streams.

Hands admits that the emphasis is now shifting to kerbside and that bring-banks are limited in terms of capacity.

SIG marketing manager Cindy Haast says the UK has come a long way in a short time: “Look at recycling four years ago and there was no infrastructure in place.” She adds that plans for the next year include focusing on kerbside collection, school collection and developing business recovery schemes.

The UK’s cartons are collected from bring-banks, emptied, taken to one of 10 regional depots and decontaminated if necessary. They are then shipped in 25-tonne loads to, principally, the Örebro Mill in Sweden.

Hands insists carton manufacturers are mindful of recovering cartons in the most environmentally efficient manner.

“Shipping to Sweden can be better than processing in the UK because of the amount of renewable energy used by the mills over there. Most British industry is based on fossil fuels,” he says. “The Swedish electricity grid is [powered by] more than 50% renewable energy – mostly hydro and biomass.”

However, he adds that Tetra Pak is working with agencies in the UK to establish “some local capacity to recycle cartons”.

RECYCLING
Sadly, the idea that material recovered via recycling is used to make more Tetra Paks does not match the reality – at least not today. “At the moment it’s not a closed-loop system,” says Hands.

“We wouldn’t dismiss using it in the future, but we have to be sure that there are environmental benefits,” he says.

Currently Tetra Pak only uses virgin material in its packs, although in October last year it announced that 75% of its cartons in the UK would carry the Forest Stewardship Council (FSC) logo within the year.

So where does the reprocessed material end up? Once in Sweden, the recovered cartons are processed into plasterboard liner for use by the building industry. It is also used in the manufacture of paper bags, envelopes and in cardboard tube cores.

“It has ended up as a commodity traded on the world market, which is good, because it’s perceived as a resource” says Elopak’s Kildal.

But what happens to the plastic, LDPE and aluminium during recycling? The Örebro mill separates the fibre from the aluminium and plastic residue, and the latter is used to power the mill itself.

“The aluminium is super thin,” says Hands. “In this instance, the mill doesn’t recover it and it combusts readily. “We are working on a way to recover the aluminium separately.”

In Brazil, Tetra Pak is working alongside paper suppliers, partners and a university and has developed a technology that converts plastic into fuel gas – which burns – and the aluminium is recoverable.

“We hope to see that technology spread to other parts of the world,” says Hands.

ELOPAK AND SIG
Elopak’s production system differs from those of Tetra Pak and SIG, explains Sveinar Kildal, director of environmental affairs at the firm. Coated reels of board are sent to the converting plant, where they are cut into individual pieces called blanks, which are ready to be sent to customers and filled.

“It differs from Tetra Pak, who don’t chop up,” he says. “We chop up, which gives customers more flexibility because they can change sizes more easily. It also generates less waste, and it takes up less space in storage.”

Like Tetra Pak, both Elopak and SIG are constantly seeking ways to reduce the volumes of materials used in cartons, cut emissions and reduce energy consumption.

“It is very important that the converting process is energy efficient and doesn’t use too much water,” says SIG marketing manager Cindy Haast. “It is important to streamline that. We are currently implementing a strategy to address scarcity at a global level.”

The company is also doing its bit to tackle global warming. For example, in September, it won the race to produce the first FSC-certified one-litre aseptic beverage carton.

Lightweighting has also been a priority. Since SIG launched its first aseptic carton in 1975, it has made cartons 23% lighter – now only 28g of material is used in a litre-sized carton.

In the past 15 years, Elopak too has reduced the weight of its cartons, from about 350gsm to 270gsm; and has cut its levels of PE from about 50g to about 40g. “It’s an ongoing process,” explains Kildal. “We are now looking at bio-degradable polymers and plastics in general and how they can be taken on board. However, the reality now is that it is expensive and doesn’t really work.”