By Mark Taylor
We continue with part 4 of Mark’s article, about a recent programme in the National Geographic series Megacities focused on São Paulo, and some of the surprising efforts underway to not only save the city from all the rubbish it produces, but in recycling, and recycling research. To read previous parts click the link at the end of the article.

Perhaps São Paulo’s greatest form of alchemy isn’t related to cans or steel, but to those cartons you find in your refrigerator, made from Tetrapak. Tetrapak itself is an ingenious blend of 6 layers of paper, plastic and aluminium that are fused tightly together. The paper layers are used to stiffen the package, plastic keeps it watertight, and aluminium blocks light and oxygen to prevent spoiling. Although the Tetrapak system is a wonder material”, it had one flaw in that it had proven impossible to recycle the tightly fused together layers. This meant that the material would end up in the dump, until recently when the recycling problem was solved here, in São Paulo.

The catadores become instrumental again in the recycling process, as they are the ones responsible for retrieving the Tetrapak cartons from São Paulo’s rubbish. These are then taken by the catadores to a central cardboard recycling plant (Brazil is one of the top recyclers of cardboard, and recycles around 76% of all that it produces). The Tetrapak cartons are then packed into bundles at the cardboard recycling plant, and from there transported to a paper recycling plant. São Paulo has one of the largest paper recycling plants, Klabin. Like Tomra’s aluminium recycling plant, Klabin operates 24 hours a day, 7 days a week. Each day it produces around 200 tonnes of recycled paper, the ingredients being 3 parts corrugated cardboard, and 1 part Tetrapak.

The recycling process for the Tetrapak starts with the Hydroblender. The Tetrapak cartons are shredded, and then fed into the Hydroblender with water to form a pulp. The paper is washed off the aluminium and plastic layers, which are separated for use later. The Hydroblender recovers about 90% of the paper from a Tetrapak carton after 20 minutes of agitation. The Tetrapak paper actually improves the quality of the recycled paper it is used to create, as the paper used in Tetrapak is virgin, whereas the corrugated cardboard has been recycled many times.

As mentioned, the fused layers of plastic and aluminium are separated in the Hydroblender, and this is where until recently there was a problem with doing anything other than dumping this material. Even so, the material had been used previously in São Paulo as corrugated roofing tiles. First the plastic and aluminium residue is finely shredded, and then placed into a corrugated mould and compressed. Then the tile is sealed with a light plastic covering. The result is a tile that is tough, light, water and heat resistant, and 10% cheaper than alternatives. Currently there are eleven factories around Brazil making these tiles, using around 700 tonnes of the residue per month.

Despite the great workaround of using the residue for roofing tiles, there was still a strong desire to crack the problem with extracting the plastic and aluminium from the residue. The problem was made even more difficult by the thin layer of aluminium oxidising easily, which meant removing the aluminium oxide as well, typically done using extreme heat. The extreme heat needed would destroy the plastic layer. TSL Environmental Engineering took up the challenge of splitting the plastic and aluminium layers, and working with a consortium were able to solve the problem and scale it up to a full size recovery plant.

The first stage in the process uses a plasma reactor, plasma being a gas superheated by an electrical charge to around 15,000C, three times the surface temperature of the sun. Under these conditions any remaining paper residue is burned away, and the plastic is vaporised into a gas, that is extracted and turned into paraffin wax. The aluminium is tapped from the reactor as molten metal, 99% pure. The usefulness of the recovered elements increases the value of a recycled Tetrapak carton by 30%. The technology used to extract the parts has also been exported to several countries.

If you have a comment on Mark’s article or would simply like to contact him then email mark@www.gringoes.com.

Previous articles by Mark:

Brazil: Japanese Standard Chosen for Digital TV
Brazil: NET Petition Feedback
Brazil: A Recycled City Part 3
Brazil: Football Love
Brazil: A Recycled City Part 2
Brazil: A Recycled City Part 1
Brazil: 100 Things To Do in São Paulo Part 3
Brazil: 100 Things To Do in São Paulo Part 2
Brazil: 100 Things To Do in São Paulo Part 1
GPS in Brazil
Brazil: PCC Attacks in São Paulo
Brazil: Tips on Buying or Renting an Apartment or House
Brazil: A Critical Sensitivity
Cleanliness is next to Brazilianiness
Brazil: Manners
Brazil: No Change, No Sale
Brazilian TV
Brazil: Ubatuba
Brazil: Professional Children
Brazil: We deliver… everything!
Brazil: Terrao Itlia
Brazil: A Layman’s Carnival Guide
Brazil: Portunglish or Engluguese?
Brazil: Feira Food
Brazil: Bilhete Unico flexibility increases
Brazil: Finding Work
Brazil: U2 Ticket Chaos
Brazil: Finding Work
Brazil: Termites
Brazil: Queues, Queues, Queues
Brazil: Let’s Go Fly a Kite!
Brazil… the Film That Is
Brazil: The Bus to Nowhere
Brazil: Piracy
Brazil: Gestures
Brazil: Proclamation of the Republic
Brazilian Film Review
Brazilian Film Review
Brazil: Finados (Day of the Dead)
Interjections, exclamations and onomatopoeia in Brazilian Portuguese
Brazil: Halloween
Brazil says “No” to banning firearms
Brazil Humour: Phone Etiquette
Brazil’s Gun Referendum
Brazil: Scams
Brazil: Moby Review
Brazil: Keeping in touch via the Internet – Part 5
Brazil: Keeping in touch via the Internet – Part 4
Brazil: Avril Lavigne at Pacaembu
Moby in Brazil
Brazil: Keeping in touch via the Internet – Part 3
Brazil: Keeping in touch via the Internet – Part 2
Brazilian Film Review
Brazil: Keeping in touch via the Internet – Part 1
Brazil: First season of Lost repeated on AXN

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