Oxo-biodegradable plastic: environmental problem or solution?

There is controversy about the use of oxo-biodegradable plastic. Understand

oxo-biodegradable

Oxo-biodegradable plastic is one that, when receiving a pro-degradant additive, has its fragmentation accelerated by the influence of oxygen, light, temperature and humidity. The material's biodegradability generates controversy among the agents in the chain. But before entering this debate, it is necessary to understand more about plastic, its impacts and alternatives.

Advantages and Disadvantages of Conventional Plastic

Plastic has been shown to be a material of great use to humanity. The malleability and capacity for transformation through the use of heat, pressure or chemical reactions give the plastic conditions for its use as raw material for the most varied types of objects. Being light, durable, easy to transport, tough and flexible, it has progressively replaced materials such as ceramics, wood and glass in many areas. Plastic, therefore, is an important item in terms of convenience and, in many ways, it provides technological development.

But it is not only on advantages that the material lives. The raw material for plastics is usually petroleum, a non-renewable natural resource whose large-scale extraction opens an intense debate about its effects on the environment. Currently, the main source of energy in the world, oil has been the cause of many wars and, in addition to being the main source of income for many countries, it is linked to relevant interests of the current economic model.

From an environmental point of view, risks associated with oil are associated with ocean acidification, global warming, its extraction processes, spills, air pollution and the improperly discarded plastic residues that contaminate terrestrial fauna and flora and the oceans. Perhaps the example of microplastics (small plastic waste that contaminate the oceans) is ample proof that this set of negative externalities needs to be very well observed and that ways of dealing with the problem effectively need to be improved and developed.

With the problems that conventional plastic can determine and the great demand from many sectors of society for solutions to this type of issue, some technologies that were created to solve or reduce damage from this type of problem began to appear. Starch plastic, PLA plastic (also known as compostable plastics) and green plastic are examples.

What are the strengths and weaknesses of alternative plastics?

Like the conventional ones, each type of alternative plastic has positive and negative points. Starch plastic, for example, has the advantage of having its origin in a renewable source, being compostable, biocompatible with the human body and biodegradable; but it can be easily attacked by bacteria (and therefore does not fulfill its function of protecting food), it has a higher economic cost and, precisely because it is made from vegetables, it demands arable land, which opens the door for questions about the fact to compete in space with areas dedicated to food production.

PLA plastic is also biodegradable, recyclable, coming from a renewable and compostable source (only under ideal conditions), on the other hand, like starch plastic, its production can be questioned as to the argument that it competes in space with the production of food, and also with respect to CO2 equivalent emissions associated with its decomposition when it occurs in an anaerobic condition.

Green plastic, in turn, has physicochemical characteristics similar to those of conventional plastic (oil-based), however, its advantage lies in the fact that it originates from sugarcane, which, in its development, captures CO2. Another positive aspect is its recyclability, with no restrictions on its combination with other conventional plastics in the recycling process. However, there are questions regarding environmental problems that occur from waste arising from inadequate disposal of the material, a situation similar to that of conventional plastics. Its renewable origin, coming from plant cultures, also raises criticisms regarding the possible competition with arable land for food purposes, as well as its influence on the increase of the monoculture regime.

Oxo-biodegradable plastic

Another product that appeared on the market with the proposal of being less harmful to the environment is the oxo-biodegradable plastic. It is common to see grocery bags or garbage bags characterized as “oxy-biodegradable” or simply biodegradable bags. Also present in bread bags, gloves, packaging, bottles, bubble wrap and cups, this type of plastic is so called because, in theory, it incurs in two different processes of degradation: chemical and biological. To be oxidizable, plastic must be degraded by oxygen (a process accelerated by the incidence of light and heat - UV rays). And to be considered biodegradable, it needs to be degraded by bacteria, which do the decomposition work.

What determines the oxidegradability condition (degradation by oxygen) of a plastic is the use of additives called prodegradants, typically metal salts based on elements such as cobalt (Co), iron (Fe), manganese (Mn) or nickel (Ni). They are added to conventional compounds from the production of plastics, made from resources taken from petroleum refining by-products (and which also function, in this initial stage, as CO2 traps), such as polyethylene (PE), polypropylene ( PP), polystyrene (PS) and polyethylene terephthalate (PET). Thus, additives provide fragmentation properties to plastics, a prerequisite and necessary for biodegradation.

Material certification in Brazil

In support of consumers interested in this type of product in our country, the Brazilian Association of Technical Standards (ABNT) defines the conditions for the use of an eco-label for plastic additives with an oxo-biodegradable function. This is done through a procedure that establishes the requirements that products with additives that accelerate the degradation of polyolefins under conditions of exposure to the environment, in composting processes or in landfills must meet to receive the license to use the ABNT Mark of Environmental Quality. This standard defines the oxo-biodegradation process as "degradation identified as the result of oxidative and cell-mediated phenomena, either simultaneously or successively" and establishes the criteria for such certification by determining that the plastic material is in accordance with the ABNT PE-308.01 standard , of April 2014, and which is based on the US standard ASTM D6954-04.

Oxo-biodegradable

Critical perspectives on oxo-biodegradables

Francisco Graziano

Some opinions are skeptical about the actual ability of such materials to be effective and degradable under any conditions when dispersed in the environment - which can be identified as an environmental hazard. Among them is Francisco Graziano, agronomist, master in agrarian economics and former secretary of the Environment of the State of São Paulo. He claims that the choice to consume oxo-biodegradables is a mistake and questions the risks of fragmenting the compound into particles invisible to the naked eye and the emissions of greenhouse gases associated with degradation, in addition to soil contamination by metals and other compounds:

“The technology allows the plastic to crumble into small particles, until it disappears to the naked eye, but it is still present in nature, now disguised by its reduced size. With a serious aggravation. When attacked by the action of microorganisms, it will release, in addition to greenhouse gases, such as CO2 and methane, heavy metals and other compounds, which do not exist in common plastic. Paint pigments, used on labels, will also mix with the soil”.

academic research

Academic researches describe situations in which oxo-biodegradable plastic objects were not able to fully go through the oxo-biodegradation process. The tests were conducted under different conditions, raising suspicions about the total alteration of the polymers structure, about the irreversible loss of properties and about the integral degradation caused by naturally occurring biological activity. Among the researches, it is possible to mention those carried out by the University of São Paulo (Photodegradation and photostabilization of blends and polymeric composites), by the Federal University of Santa Maria (Degradation of conventional and oxo-biodegradable plastic bags), by the Israeli University Ben-Gurion do Negev ( New perspectives in plastic biodegradation) and by the Faculty Assis Gurcazs, whose objective was to prove soil contamination by heavy metals, which did not occur, although there are notes questioning the effective capacity of materials degradation (Verifying the presence of heavy metals such as lead and mercury in waste from oxo-biodegradable plastic bags).

On the other hand, studies conducted by Gerald Scott, when he was professor emeritus of chemistry and polymer science at the University of Aston, UK, chairman of the British committee of the Institute of Standards on Biodegradability of Plastics and the scientific board of the Association of Oxo-biodegradable Plastics - therefore, an important figure in the subject of biodegradability of plastics - defend the oxo-biodegradables. He clarifies in an article on oxo-biodegradable plastics written for the Bioplastics Magazine 06/09, that oxo-biodegradable plastic is not normally commercially designed to be composted, nor is it designed for anaerobic decomposition or for degradation in landfills. For Scott, oxo-biodegradable plastic is not intended to fragment only – it is designed for complete bioassimilation by natural microorganisms on a larger time scale than composting (180 days), but in a shorter period than for natural waste , like leaves and twigs (ten years or more), and much shorter than for normal plastics (many decades). According to the academic, all plastics will eventually become fragile, fragment and be bioassimilated, but the difference with the oxo-biodegradable technology is the speed of the process, which is accelerated in it.

international institutions

The Bioplastics Council of the Industrial Plastics Society (SPI) declares, in a specific document in which it reveals its position on pro-degradable additives (“Position Paper on Degradable Additives”), that the claims about the safety in the use of oxo-biodegradable materials are , in literal translation, are invalid and misleading as they are not supported by scientific evidence that does not conform to currently accepted standards.

The council also says that data related to complete mineralization, made by bacteria, has not been released to the public and that the main effect of oxo-biodegradation is fragmentation (oxidegradation) and not biodegradation, which mischaracterizes the oxo-biodegradation process. In your conclusion:

"The position of the SPI Bioplastics Division is that any claim, especially claims for consumers, needs to be supported by scientific evidence based on well-established specifications and standards. In the case of 'additives', the problem lies in 'claiming biodegradation' when there is no evidence in supporting these claims or proof of biodegradability in accordance with specifications accepted by independent third parties. Allowing the brand owner, retailer or, ultimately, the consumer to decide what they consider a product to be "biodegradable" is risky as it since this could lead to varied definitions that would only lead to greater consumer confusion. With the growth of the offer of biodegradable and compostable products, together with the debate on the management of waste destined for landfills, it is the duty of the industry to provide scientific certifications clear and well-founded by independent agents, who assure interested parties that and the products offered meet their end-of-life disposal requirements and offer real value in their intended use."

The European Association of Plastic Recyclers (EuPR), for its part, has long taken a stand on oxidizable additives which, according to its interpretation, have the potential to do more harm to the environment than benefit. The organization also says that it is a public misconception to believe in the biodegradability of these materials, since the oxidizable additives will only end up in fragments. In addition, he claims that it is a disservice to divert public attention from recycling - which has reached current rates after much effort by industry, authorities and civil society - making the population think that waste will degrade by itself.

Recycling

In an article on polymers published in Scielo Brasil, José Carlos Pinto, a professor on the board of the chemical engineering program at COPPE, at the Federal University of Rio de Janeiro, questions, in relation to plastics, the belief that what is ecologically correct is to be biodegradable . He points to the urgency of the perception that if the plastic material degrades as it does with food and organic waste, the resulting degradation (for example, methane and carbon dioxide) would end up in the atmosphere and in aquifers, contributing to the global warming and for the degradation of water and soil quality. He believes in reversing the pollution generated by the material through environmental education and correct waste and tailings collection policies. It also describes that the fact that plastics do not degrade easily is characterized by a differential that gives them the possibility of reuse for many times, their recyclability, a determining factor for the enormous potential to contribute to the reduction in the consumption of raw materials, energy and rationalization the use of available natural resources. José Carlos Pinto considers the fact that plastics offer a unique technological opportunity for depolluting the atmosphere and reducing net carbon emissions in the world, as they fix carbon in the solid state. It is sympathetic to green plastic because it associates the use of ethanol in the generation of plastics (production of polyethylene, polypropylene or green PET) with the consumption of sunlight by plants in capturing carbon dioxide from the atmosphere and generating solid material, allowing a cleaning the earth's atmosphere. Therefore, he considers the “obsession” with the biodegradability of plastics mere misinformation, pointing to selective collection and recycling programs as a solution to the problem of plastic waste.

The Brazilian Plastic Industry Association (Abiplast) has a clear position regarding pro-degrading additives incorporated into plastic materials. The entity considers that environmental degradation is not an adequate solution for waste management, and therefore does not recommend the use of plastic materials with pro-degrading additives in the manufacture of bags and bags, as well as other plastic products , with the promise that they are environmentally friendly. In attention to oxo-biodegradable materials, Abiplast lists some studies, among them those carried out by the California State University in partnership with Chico Research Foundation (2007) and another carried out by researchers in India (Centre for Fire, Environment & Explosive Safety and Center for Polymer Science and Engineering, Indian Institute of Technology) and Sweden (Department of Polymer Technology, The Royal Institute of Technology), published by the American Chemical Society:

"In both studies, an important consideration is made about the recycling of plastic materials mixed with plastic waste containing prodegradants, which make recycled materials more susceptible to environmental degradation, although theoretically it is possible to delay the onset of degradation using appropriate antioxidants , however, it is difficult to estimate the ideal amount of antioxidants needed. In this case, the pro-degradant additives substantially impact the recycling of post-consumer plastic materials, as they compromise the mechanical properties of the plastic material, thus reducing the useful life of plastic products. These studies also consider the impossibility of predicting which period of time the plastic material fragments will persist in the environment and the potential harmful effect of these on the environment. These studies also consider the impossibility of predicting the period of time in which the plastic material fragments will persist in the environment and the potential harmful effect of these on the environment.”

No additives

Image: Abiplast

Abiplast alleges that pure and simple biodegradation is not contemplated in the National Solid Waste Policy (PNRS), and only makes sense to be carried out in compost plants or in anaerobic biodigesters, otherwise, it results in waste of natural resources, energy and water, contributing, further, to the imbalance of the greenhouse effect and consequent global warming. The institution understands that the most effective solution for the treatment of post-consumer plastic waste is through efficient selective collection programs, involving consumer education, the integration and engagement of the municipality, waste pickers, recycling cooperatives and industry to transform this waste into new plastic products with quality, in compliance with the principle of shared responsibility, in accordance with law 12,305/2010.

A report published by Transfercenter fur Kunststofftechnik (TCKT) in Austria, an organization that could be classified as a technology transfer center for plastics, describes the results of a study commissioned by one of the companies that manufacture pro-degradant additives. The study would aim to assess the effect, if any, on products manufactured based on recycled oxo-biodegradable plastic material (with pro-degradant additives), specifically thicker structured plastic compounds intended for outdoor use, such as plastic wood, garden furniture , municipal and sign posts, since the thicker the materials produced (unlike the use in the form of films used in plastic bags), the more difficult the penetration of oxygen into the body of the plastic structure, therefore less susceptible to oxidegradation. The results of the study did not show significant differences, according to the author, compared between products manufactured from recycled oxo-biodegradable plastics and non-additive recycled plastics. In a statement related to the study, Francisco Morcillo, head of public and industrial affairs at the British Federation of Plastics (BPF), published in the specialized vehicle Plastic News Europe, reveals a set of considerations that highlight the fact that the experiment took place in materials recycled materials containing oxo-biodegradable products intended for specific use in thick-structured objects for outdoor exposure, revealing concern that the structure of the UK and the European plastics recycling industry does not guarantee the necessary safety that the recycled material (additive) with pro-degradants) will only be used in such products. He also noted in the publication that oxo-biodegradable plastics will not degrade for two or five years and that this time would be enough for such materials to find their way into the environment, which includes oceans and rivers, also noting the danger that such degradable products nature would be able to offer, in a way and even encouraging the production of waste.

Position of producers of pro-degradant additives

According to the Association of Oxo-biodegradable Plastics (OPA), oxo-biodegradable plastic is a conventional plastic to which small amounts of salts are added. The organization says that these salts are not heavy metals and that, at the end of the product's useful life, the salts catalyze the natural degradation process in the presence of oxygen - noting that this does not occur in deep layers of landfills. All of this determines the molecular degradation of polyolefins in a continuous process until the material has been biodegraded to nothing more than CO2, water and humus, without leaving petro-polymer fragments in the soil. That is, until the material is no longer characterized as a plastic, becoming a biodegradable material.

The OPA justifies the need for oxo-biodegradable plastics due to the entry of thousands of tons of plastic waste daily around the world, and its permanence for decades, without it being possible to effectively collect all the plastic for recycling or other forms responsible disposal.

Regarding the question related to the actual biodegradation of the material and not its simple fragmentation, OPA emphasizes that the oxo-biodegradable technology converts plastic products into biodegradable materials at the end of their useful life, doing this through oxidation (through oxygen exposure). The entity rejects any allegations that cast doubts on this fact and attributes certain questions to non-specialist scientists about the oxo-biodegradable technology and to malicious individuals interested in spreading disinformation for the benefit of marketing advantages to products of their interest. The OPA claims that oxo-biodegradable plastic degrades and biodegrades in an open environment in the same way as nature's waste, but this only occurs more quickly. What's more, it does this without leaving toxic residues or plastic fragments behind. For the organization, if the oxo-biodegradable plastic simply fragmented, without biodegradation, the European Committee for Standardization (CEN) would not have defined oxidegradability as "degradation resulting from oxidative and cell-mediated phenomena, simultaneously or successively" and the US standardization organizations, British and French would not have included biodegradability tests in ASTM D6954, BS8472 and ACT51-808.

The association categorically states that one of the benefits of oxo-biodegradable plastic is its recyclability as part of a normal plastic waste stream. However, it informs that it does not degrade rapidly in composting at low temperatures and therefore does not pass the tests in EN13432 in the specified time scale, although it is suitable for "in-vessel" composting at the higher temperatures required by European community regulations .

According to the institution, when disposed in landfills, oxo-biodegradable plastics fragment and degrade only partially in the form of CO2 and water in parts of the landfill where oxygen is present, but degradation will not occur in deeper parts of the landfill, in the absence of oxygen.

Regarding the presence of heavy metals in its composition, the position informed is that it contains metallic salts, trace elements that are even necessary in the human diet, which should not be confused with ​​toxic heavy metals, such as lead, mercury, cadmium and chromium.

The OPA declares that such materials originate in a by-product of oil or natural gas and that they recognize the fact that these resources are finite, but emphasize that the by-product arises because the world needs fuel, and that such a by-product will arise when used or not for the manufacture of plastics. They emphasize the possibility of using pro-degrading additives in plastics of the polyethylene type, derived from sugar cane (technology developed in Brazil).

Finally, the entity highlights as an advantage of the oxo-biodegradable product the possibility that it can be programmed for degradation in any necessary time scale. They claim that the average shelf life of a carry bag is normally designed to be around 18 months (to allow for distribution, storage and reuse), but shorter or longer periods are possible and that during that time the bags can be reused for purchases or for use as liners for waste boxes, among other things. They claim that heat and light are accelerators of the degradation process, although not essential. If discarded into the environment at the end of its useful life, the material will degrade and biodegrade much more quickly than conventional plastic. OPA states that the time scale for the abiotic phase can be predicted by laboratory tests, but that it is not necessary or possible to predict the time for subsequent biodegradation.

precaution principle

With all the arguments listed throughout this article, we believe that it contributes to the user's greater reflection about their decisions regarding consumption practices that may involve the use of oxo-biodegradable materials or not. With regard to oxo-biodegradables and any other consumption options associated with the various types of plastic materials, it is always important to take into account: whether or not the inputs are of renewable origin, their carbon intensity, whether there is compromise of arable areas for the cultivation of food material, its contribution to the generation of waste and to the circular economy, its contaminating potential, pollution and the emission of gases that intensify the greenhouse effect that contribute to climate imbalances are avoided or reduced. Therefore, it is always important to have a commitment to the precautionary principle.

Consumption is one of the most striking forms of our individual expression within the current model of our society. Our consumption practices determine important social and environmental impacts, whose effects we can understand as externalities, consequences inherent to the decisions we make and whose responsibility, ethically, is entirely ours.



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