Plastics and recycling: a toxic relationship?

The recyc­ling of the mater­i­als that we pro­duce and con­sume has been iden­ti­fied as a major chal­lenge by the French gov­ern­ment. It is the sub­ject of a Pri­or­ity Research Pro­gramme and Equip­ment (PEPR) fun­ded by France 2030¹. Plastics, in par­tic­u­lar, are the focus of a ded­ic­ated research pro­gramme. The stated object­ive is to improve the know­ledge and tech­niques that enable them to be reused, in order to pre­serve resources. Plastics are found every­where: in pack­aging, tex­tiles, cos­met­ics, etc. They are extremely ver­sat­ile and have become “integ­rated into our pro­duc­tion and con­sump­tion prac­tices by present­ing them­selves as a sub­sti­tute for nat­ur­al mater­i­als,” observes Bap­tiste Mon­saingeon, soci­olo­gist and lec­turer at the Uni­ver­sity of Reims Cham­pagne-Ardenne. With the lim­it­a­tions that we are aware of today.

To begin with, the bricks that make up plastics are mainly obtained from fossil fuels (oil and gas) and assembled into a long chain: the poly­mer. Numer­ous sub­stances are used dur­ing the syn­thes­is pro­cess. Some are used to optim­ise the chem­ic­al reac­tion and are there­fore not inten­ded to end up in the fin­ished product, yet some are absorbed by the plastic. Oth­ers are used to give the mater­i­al spe­cif­ic prop­er­ties: flex­ib­il­ity, col­our, UV or fire res­ist­ance, etc.

Accord­ing to the PlastChem report², up to 16,000 dif­fer­ent chem­ic­als can be used in plastic. A num­ber of them are poten­tially harm­ful. “There are about 10,000 for which we lack data. And more than 4,000 that we know are dan­ger­ous,” warns Beth­anie Car­ney Alm­roth, pro­fess­or of eco­tox­ic­o­logy at the Uni­ver­sity of Gothen­burg in Sweden. “They can be car­ci­no­gen­ic, dis­rupt the endo­crine sys­tem, or be tox­ic to spe­cif­ic organs such as the kid­neys or the skin.”

The man­age­ment of plastic waste is all the more of an issue as it has per­meated our envir­on­ment. This is what Flori­an Pohl, a geoscience research­er at the Uni­ver­sity of Bayreuth in Ger­many, has observed when study­ing plastics in river and mar­ine sys­tems. “At a depth of 4,000 metres, if I take sed­i­ment from the ocean floor, I can detect micro­plastics. It’s fright­en­ing because it shows that they are lit­er­ally every­where,” he warns.

“Over the past 30 years, a huge amount of energy and eco­nom­ic resources have been devoted to the devel­op­ment of recyc­ling chan­nels, with the aim of recon­cil­ing sus­tain­ab­il­ity and eco­nom­ic growth,” sum­mar­ises Bap­tiste Mon­saingeon. In France, loc­al author­it­ies are respons­ible for man­aging our waste. In most cases, this is del­eg­ated to private oper­at­ors who col­lect the con­tents of our bins and waste centres and send them to sort­ing centres. There, the com­pon­ents are sep­ar­ated accord­ing to their pos­sible use: energy pro­duc­tion by incin­er­a­tion (“energy recov­ery”) or recyc­ling (“mater­i­al recov­ery”). Oth­er­wise, they are sent to landfill.

There are around twenty waste man­age­ment chan­nels in France. They are organ­ised on the prin­ciple of “exten­ded pro­du­cer respons­ib­il­ity³”: pro­fes­sion­als who place products on the mar­ket (pack­aging, tex­tiles, equip­ment, etc.) are respons­ible for fin­an­cing or man­aging their post-con­sumer repro­cessing by users. “For paper, card­board and metals, it works rather well,” says Bap­tiste Mon­saingeon, “as for plastics, it is mainly the PET in our water bottles that is recycled.”

In France, accord­ing to fig­ures from ADEME⁴, less than a third of post-con­sumer plastic waste is col­lec­ted, and only 14% of it is actu­ally recycled. Bap­tiste Mon­saingeon points out that in 2018 “the gov­ern­ment set a tar­get of ‘100% recyc­ling of plastic pack­aging by 2025’. We are a long way from achiev­ing this.”

Reuse is sub­ject to a num­ber of tech­nic­al lim­it­a­tions. The fin­ished products are com­plex assem­blies of dif­fer­ent mater­i­als that can­not always be sor­ted. “Mech­an­ic­al” recyc­ling requires plastics to be sep­ar­ated into sim­il­ar poly­mers. They must then be washed and crushed into flakes, which are melted down into gran­ules to make new plastic. Over time, this causes degrad­a­tion of the poly­mers. “This long chain of molecules can break and start to shorten as it is heated and melted. The qual­ity of the mater­i­al deteri­or­ates, so new plastic must be added to main­tain it,” explains Beth­anie Car­ney Alm­roth. “Ulti­mately, there can be an increase in the amount of tox­ic sub­stances in plastics as they are recycled⁵⁶” she adds.

“Chem­ic­al” recyc­ling, mean­while, offers meth­ods for chem­ic­ally sep­ar­at­ing poly­mers or break­ing them down into basic molecules, which can be used to recre­ate plastic. “Some of them have been shown to be effect­ive, but only on a small scale, on pre-indus­tri­al waste that is much purer than that from con­sumer waste,” she adds. They are there­fore not viable from an eco­nom­ic and envir­on­ment­al point of view for mixed plastics.

Finally, there are plastics that we don’t know how to recycle prop­erly. “The chan­nels do not cov­er the entire waste depos­it in France,” explains Bap­tiste Mon­saingeon. “Some play­ers are there­fore look­ing to export, primar­ily to Europe.” This can be a first step in the trans­it of plastic mater­i­al flows: “Tur­key, for example, is a place where plastic waste is expor­ted, more or less leg­ally,” he says.

How­ever, while it may be vir­tu­ous, the repro­cessing of plastics remains a source of pol­lu­tion. “We know that recyc­ling plants release micro­plastics and chem­ic­als when frag­ment­ing or shred­ding this waste⁷,” emphas­ises Beth­anie Car­ney Alm­roth. Not to men­tion that a lot of plastic ends up in land­fill. “This can obvi­ously lead to con­tam­in­a­tion of the envir­on­ment, but also of humans,” she con­cludes, adding that “80% of glob­al recyc­ling passes through the hands of waste pick­ers, the vast major­ity of whom work without pro­tec­tion against this expos­ure⁸.”

Poor waste man­age­ment also con­trib­utes to the spread of plastic in the envir­on­ment. Due to open-air stor­age, at the mercy of the wind, or even dur­ing trans­port, as Flori­an Pohl describes: “Some plastic gran­ules used as raw mater­i­al can end up in river water⁹.” Car­ried along by the cur­rents, they are abraded by the sed­i­ments and broken down into ever smal­ler frag­ments. This increases the dif­fu­sion sur­face: the addit­ives escape from it more and more rap­idly. “More and more plastic is end­ing up in the envir­on­ment, and we don’t really know the con­sequences: how quickly do the sub­stances they con­tain release them­selves and what are the effects?” A ques­tion at the centre of his research.

For Bap­tiste Mon­saingeon: “Believ­ing in recyc­ling is a bit like believ­ing in a prom­ise: that of con­tinu­ing to con­sume with a clear con­science.” How­ever, “it is pos­sible to restore it to its right­ful place without mak­ing it a magic solu­tion,” he says. Start­ing with redu­cing the types of plastic used to those that we know how to recycle, and lim­it­ing the num­ber of chem­ic­als used. “Addit­ives provide func­tion­al­ity, but we can reduce them to a much smal­ler num­ber, avoid dan­ger­ous sub­stances, and strengthen legis­la­tion,” sug­gests Beth­anie Car­ney Almroth.

This is a field that calls for innov­a­tion, to devel­op more sus­tain­able and safer mater­i­als. How­ever, it is not a ques­tion of simply repla­cing one mater­i­al with anoth­er, but of redu­cing the pro­duc­tion of vir­gin plastic. “This is the con­sensus of the inter­na­tion­al sci­entif­ic com­munity, regard­less of the dis­cip­line,” emphas­ises Bap­tiste Monsaingeon.

This involves, in par­tic­u­lar, the imple­ment­a­tion of new infra­struc­tures to make reuse more access­ible with reusable and refil­lable con­tain­ers. “In France, a num­ber of com­pan­ies are work­ing in this field¹⁰¹¹,” com­ments Beth­anie Car­ney Alm­roth. “This shows that there is scope for the imple­ment­a­tion of new eco­nom­ic mod­els,” bey­ond recyc­ling and the unbridled pro­duc­tion of plastic.

Mikaël Mayorgas