PLA plastic is often hailed as an alternative to traditional plastics due to its biodegradability. However, is it truly a sustainable choice for the environment? Join us as we delve into this question in the article below.
PLA (Polylactic Acid) plastic, derived from natural sources like cassava starch or sugar beets, often leads to the misconception that it's entirely environmentally friendly. However, the truth is, PLA is still a type of plastic.
Source: Internet
PLA poses recycling challenges due to its inability to be easily processed alongside common plastics like PET or HDPE. Unlike traditional plastics categorized by code for streamlined recycling, PLA often requires separate handling.
Additionally, recycling PLA demands specific temperature and climate conditions, which many facilities lack. Consequently, establishing an efficient recycling infrastructure for PLA becomes challenging, leading to increased costs and inefficiencies in the recycling process.
Source: Internet
The production process of PLA plastic is not simple and resource-efficient. Although the main source of PLA is renewable plants, the process of converting natural materials into PLA plastic still requires a large amount of energy.
First, to produce PLA, raw materials such as cassava starch and sugar beets must be harvested and processed. This process involves the use of machinery and chemicals and also requires the expenditure of energy to transport raw materials from the production site to the PLA manufacturing plant.
Next, the chemical process to convert raw materials into PLA plastic also consumes a lot of energy and uses catalysts and solvents. Even though PLA is considered a bioplastic, its production still hurts the environment.
Source: Internet
In addition, the PLA production process also creates a large amount of waste and byproducts, affecting the environment around the manufacturing plant.
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One of the major weaknesses of PLA plastic is that it only decomposes under industrial processing conditions, not in the natural environment or under normal conditions.
PLA requires a specific combination of temperature and microorganisms to decompose. In the natural environment, the temperatures and microorganisms needed to decompose PLA are often insufficient, resulting in the plastic remaining for a long time.
Source: Internet
Even under normal home conditions, temperature and microorganisms are not enough to effectively decompose PLA. If PLA products are not collected and processed properly, they can still cause environmental pollution and create plastic waste.
Although PLA plastic is touted as an environmentally friendly option, PLA decomposition products can also be harmful to the environment and organisms in some cases.
When PLA plastic decomposes under industrial processing conditions, it often breaks down into small particles, called microplastics. These microplastics can continue to exist in the natural environment for long periods and can be absorbed into biological systems through the food chain. This can cause health problems for marine life and animals at every level of the food chain, from small microorganisms to large animals.
Source: Internet
Furthermore, in freshwater and soil environments, decomposition products from PLA plastic can create toxic substances when decomposed, affecting the growth of plants and animals living underground.
PLA plastic, although considered a greener alternative to traditional plastic, still has certain environmental limitations. Therefore, the use of PLA plastic should be carefully considered and should only be used when necessary.
Instead of PLA plastic, priority should be given to using products made from natural materials that are completely degradable.
Products from natural materials that are completely biodegradable are considered the most sustainable solution to reduce the impact of plastic waste on the environment. Instead of using PLA or other bioplastics, products are made from natural materials that are naturally and completely degradable.
The biggest benefit of using products from completely biodegradable natural materials is that it does not cause sustainable plastic waste. When these products are disposed of in the environment, they will naturally decompose within a short period, returning to organic substances that do not pollute the environment.
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Paper cups and lids with water-based coating
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Although PLA plastic has certain advantages, there are still many limitations in terms of sustainability. To aim for a clean and green environment, we need to consider carefully before using PLA and prioritize friendlier alternatives such as EQUO's completely biodegradable natural products. With the mission of protecting the environment and leading a green lifestyle, EQUO is committed to providing consumers with quality, safe, and environmentally friendly products.
The massive plastic production worldwide leads to a global concern for the pollution made by the plastic wastes and the environmental issues associated with them. One of the best solutions is replacing the fossil-based plastics with bioplastics. Bioplastics such as polylactic acid (PLA) are biodegradable materials with less greenhouse gas (GHG) emissions. PLA is a biopolymer produced from natural resources with good mechanical and chemical properties, therefore, it is used widely in packaging, agriculture, and biomedical industries. PLA products mostly end up in landfills or composting. In this review paper, the existing life cycle assessments (LCA) for PLA were comprehensively reviewed and classified. According to the LCAs, the energy and materials used in the whole life cycle of PLA were reported. Finally, the GHG emissions of PLA in each stage of its life cycle, including feedstock acquisition and conversion, manufacturing of PLA products, the PLA applications, and the end of life (EoL) options, were described. The most energy-intensive stage in the life cycle of PLA is its conversion. By optimizing the conversion process of PLA, it is possible to make it a low-carbon material with less dependence on energy sources.
Keywords: polylactic acid, greenhouse gas, life cycle assessment, carbon dioxide, low carbon
Nowadays, plastics are employed widely in different industries, such as construction, packaging, electronics, clothing, healthcare, and so on, due to their excellent physical, chemical, and mechanical properties, and economic viabilities compared to traditional materials [1,2,3,4]. The global plastics manufacturing started from 1.5 million tons in , and reached 322 million tons in , and is predicted to increase to 1.63 billion tons in [5,6]. This huge amount of plastics production worldwide has made its disposal a considerable global concern, with a great potential to harm the environment, humans, and animals. Plastics are found in seawater, jungles, or municipal solid wastes. More than 8.3 billion tons of plastics were produced in the span of to , in which less than 20% were recycled or incinerated, and the rest were left in the environment or were landfilled [7,8]. The environmental issues and ecological impact associated with plastics have led to more studies and research into developing more sustainable materials. Currently, new factors such as recyclability and biodegradability are taken into account when developing new plastics [2,9]. Despite the highly developed circular economy, plastics are still being observed in the environment [10]. Hence, it can be concluded that biodegradability may be the most important factor to address the environmental aspects of plastics [11].
Bioplastics or biodegradable polymers are the potential candidates to replace fossil-based plastics due to using renewable resources and significantly less greenhouse gas emissions (GHE) [12,13,14]. Bioplastics are fully or partially derived from bio-based and renewable origins such as agriculture or marine products, which can help in CO2 absorption during their production process [15,16]. The absorbed carbon will finally be released when the life span of the product is over [17]. This is how these bio-based plastics avoid consuming additional fossil-fuels as feedstock [18]. However, the production of bioplastics is still dependent on fossil fuels as the source of energy in their fabrication process, which can also be eliminated in the future through using renewable resources. Due to the developing market share of bioplastics, it is important to increase our knowledge on the economic and environmental aspects of bioplastics. LCA is a tool that provides quantitative information about environmental sustainability, or &#;cradle to grave&#; of a bioplastic [15,19,20,21].
PLA is considered as one of the most prevalent and commercial bioplastics worldwide, with a production of 0.2 million tons in and 0.3 million tons in . PLA is fabricated from lactic acid, which is produced from the fermentation of the starch present in sugarcane and corn [7]. PLA is used in different industries, such as healthcare, textile, packaging, and so on [22,23,24]. Historically, the biomedical applications of PLA date back to the s, when it was used as sutures [25]. Afterward, it gained considerable attention in the s from Cargill, Dupont, and Coors Brewing, and then it was produced on large scales. The majority of the manufactured PLA is employed in packaging [26]. Furthermore, due to the biodegradability of PLA, it provides several EoL options, including mechanical recycling, chemical recycling, landfilling, and industrially composting [27,28]. It should also be noted that compostability is the same as biodegradability but under aerobic conditions for 6&#;12 weeks [29,30]. The EoL options help with the circularity of PLA and managing for a circular economy. In this regard, this paper aims to provide an LCA for PLA to help manufacturers and consumers with proper sustainable approaches in the life span of PLA, including usage, manufacturing, and disposal. First, the life cycle of PLA is discussed in four main stages, including feedstock collection and its conversion, processing, applications, and EoL options. Second, a comprehensive literature review of the existing LCAs for PLA is presented. Finally, we come up with specific suggestions to make PLA a low-carbon material by exploiting the available GHG emissions data.
A summary of the existing life cycle studies on PLA and its products was extracted from the literature and is presented in Table 2. Comparing the characteristics, objectives, assumptions, data sources, and major findings of these studies will provide insights into better PLA LCA and address the environmental issues.
The summary of the available LCAs on PLA.
Subject Goal and Scope LCA Software/LCIA(1)
The production processes of PLA are capable of being both sources of carbon credit and fossil-energy-free
(2)
Being lower in fossil energy use and greenhouse gas emissions compared to conventional polymers based on petrochemicals
(3)
Major impact: climate change
(1)
All three types of containers have the same mold
(2)
The filling operation of each type of container is excluded
(3)
Total amount of waste: PET = 3.61%, PS = 3.15%, PLA = 3.19%
(4)
Composting as an EoL scenario is not considered
(1)
The PLA containers are capable of being 100% compostable and/or recyclable
(2)
Major impact: global warming, aquatic ecotoxicity burdens, and ozone layer depletion affected by transportation stage of polymers
(1)
Enough PLA in the lightweight packaging (LWP) waste
stream
(2)
Transmission of 100% PLA fraction from the waste to the thermal treatment
(3)
Thermal treatment as the reference EoL option
(1)
Superior savings (0.3&#;1.2 times higher) in GHG emissions when utilizing PLA recyclates compared to incineration
(2)
Having a lower CED of recycling in comparison with waste incineration
(3)
PIW and PCW lead to energy recovery in case of heat and electricity
(1)
The toxicity is excluded from environmental impact categories
(1)
Major impacts: Global warming potential, eutrophication, water, particulate matter, land use, acidification
(2)
Considerable improvement measures in PLA&#;s environmental impact reduction: enhancement in the farming practices of sugarcane, better yield bagasse boilers at the sugarmill, increase in the renewable energy usage in the conversion process, and reducing the assistant chemicals&#; usage
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(1)
Beverage bottling, labeling, storage, and distribution were excluded from the production process
(2)
Storage and transportation of raw materials were excluded
(1)
Emission of nitric oxides, carbon dioxides, and sulfur oxides into the natural environment affected by electrical energy, water, and raw materials utilization during the bottle shaping process
(2)
End product degasification and cooling have the most important role in the emissions and fine particles&#; formation
(3)
Major impacts: global warming, water resources&#; usage, fine particles&#; formation, water acidification, and land use
(1)
The average transportation distance of PLA and Mater-Bi products = 100 km
(2)
Biodegradation degree of PLA and Mater-Bi in the anaerobic digestion process = 85%
(3)
Mechanical recycling based on two options: open-loop LCA and closed loop LCA
(1)
Utilization of bioplastics instead of conventional plastics leads to significant GHGs emissions and energy savings
(2)
Energy consumption of PLA compared to PE and PET is 50% from fossil resources (non-renewable)
(1)
The CO2 required for photosynthesis from the solar energy and air is excluded
(2)
Out of total applied nitrogen fertilizer, 1% evaporated as N2O-N and 10% as NH3
(3)
Efficiency of electricity production = 30%
(1)
Reduction in non-renewable energy demand, CO2 emissions, and human toxicity by PLA bottles production
(2)
High GHG emission induced by cassava-based
PLA resin compared to corn- and sugarcane-based PLA
(3)
Major impacts: landfill, incineration, recycling, and composting
(1)
The flows that contained less than 1% of the cumulative mass might be excluded
(2)
The flows that contained less than 1% of the cumulative energy might be excluded
(1)
Major impacts: global warming, land and water acidification, stratospheric ozone depletion
(2)
TPS is less effective in environmental impacts than PLA
(3)
Better performance in terms of environmental issue belonging to bio-composites compared to PP, except for eutrophication effects if manufactured utilizing hydroelectricity
(1)
Stiffness has a linear relationship with elasticity
(2)
The amount of energy according to the environmental data is replaceable with conventional productions based on a system expansion approach
(3)
Biodiversity and water usage are excluded
(1)
From two system boundaries that are followed: cut-off possesses a higher impact in comparison with expansion
(2)
Incineration and recycling possess negative values in the disposal&#;s Damage assessment for one kg of ML in I
(1)
The plastics&#; utilization and formation of the product were excluded
(2)
LDPE was considered as film waste and modeled like the MRF (material recovery facilities) process scenarios
(1)
Gaining 100% damage level for petrochemical polymers&#; production impact in impact categories
(2)
Highest global warming induced by TPS and PLA landfilling
(3)
Recycling can reduce environmental impacts by 40% to 60% in fossil fuel depletion for petrochemical polymers
One of the pioneering studies on LCA of PLA dates back to , on the NatureWorks&#; PLA [75]. According to this study, the total required fossil energy for PLA was less than fossil-based polymers which can be used in other sections of the PLA production procedure. Later, in , Madival et al. investigated the LCA of PLA clamshell containers in comparison with PET and PS clamshell containers [76]. According to the results, the PLA containers could be 100% recyclable and/or compostable. Moreover, PLA had less GHE (~28 kg CO2) compared to PET (~830 kg CO2) distributed by 16-ton trucks [76]. Then, Piemonte examined the PLA total energy demand and environmental impact in comparison with PE and PET in [77]. They found that bio-plastics usage instead of fossil-based plastics can lead to considerable energy and GHE savings [77]. Subsequently, in , Papong et al. carried out a comparative investigation on the environmental impact of PET and PLA drinking water bottles from a life cycle outlook. The results showed that the production of PLA bottles can lead to a reduction in CO2 emissions, lower toxicity, and less demand for non-renewable energy [78,79]. In the same year, Mahalle et al. studied a cradle-to-gate LCA of polylactic acid/thermoplastic starch (PLA/TPS) and wood fiber-reinforced PLA bio-composites [80]. According to the results, bio-composites are able to perform in a more environmentally friendly manner in comparison with PP [80]. In , Benetto et al. examined the LCA of PLA and TPS multilayer film designed by atmospheric plasma usage. Two system boundaries and two EoL were carried out, namely, cut-off, expansion, recycling, and incineration, respectively. Cut-off had a higher impact in comparison with expansion. In disposal, incineration and recycling had negative values for one kg of multilayer in I [81]. Later, in , Hottle et al. investigated the production of biopolymers and EoL comparisons through LCA [13]. Based on the results, recycling is able to reduce 40% to 60% of environmental impacts in fossil fuel depletion for petrochemical polymers [13]. In addition, Maga et al. studied the LCA of the PLA and its recycling options in [70]. They examined mechanical, solvent-based, and chemical recycling of the waste PLA. Based on the results, recycling PLA led to higher savings (0.3&#;1.2 times higher) in GHE compared to the PLA incineration. Furthermore, recycling had less cumulative energy demand (CED) compared to incineration [70]. In the same year, Morão et al. investigated the PLA&#;s life cycle impact (LCI) produced by sugarcane in Thailand [15]. According to the results, several approaches were introduced to improve the PLA environmental impact, such as enhancement in the farming practice of sugarcane, exploitation of bagasse boilers with higher efficiencies at sugarmill, consumption reduction in auxiliary chemicals, and renewable energy usage enhancement in the sugar conversion process to PLA [15]. One of the most recent available LCAs of PLA was conducted by Bałdowska-Witos et al. for the PLA bottle shaping&#;s environmental impact assessment in [82]. The results demonstrated that the GHE in the environment was affected by water, electrical energy, and raw materials usage during the bottle shaping process [82].
Investigation of the GHE in the life cycle of a material can help with the best suggestions for making it a low-carbon material. As mentioned in the previous sections, most of the PLA products end up in landfilling or composting. In this section, the CO2 emission of PLA in three different EoL options including landfilling without biodegradation and landfilling or composting with 60% biodegradation is evaluated. The PLA CO2 emission is compared with PE products. GHE of all these materials is summarized in Figure 7.
GHE balance in the life cycle of PLA products with different EoL options compared with different PE grades [2].
As PE is not considered as a biodegradable material, there are no EoL emissions displayed for it in Figure 7. It can be observed in Figure 7 that carbon uptake is considered only for biopolymers, which is their advantage in terms of environmental aspects compared to fossil-based plastics [83]. One kg of PLA is calculated to be able to uptake around 1.8 kg of CO2. Regarding the total GHE of PLA landfill with no biodegradation, it can be concluded that it releases 1.2 and 0.9 kg of CO2 per kg of PLA less than LDPE and HDPE, respectively. Opposed to this, in the cases that the biodegradability of PLA is taken into account, the total GHE of PLA will enhance greatly, more so than HDPE and LDPE.
It should be noted that PLA is in the early steps of its progress and its production and conversion processes are not optimized compared to PE, which owns the first rank in terms of production worldwide among plastics [84]. By optimizing the conversion process of PLA, it is possible to reduce the energy demand and GHE of the procedure. For example, NatureWorks has been producing PLA for more than 15 years and is optimizing the processing of PLA. Therefore, it seems that one of the best suggestions for making PLA a low-carbon material is optimizing its conversion process, as it consists of more than 50% of PLA GHE in both landfilling and composting. In fact, PLA conversion releases about 2.9 kg of CO2 per kg of PLA. The NatureWorks optimization shows that they were able to develop the production of PLA and could reach only 0.6 kg of CO2 emission per kg of PLA. However, that data is not available to the public. This clearly shows the high potential of optimization of the PLA processing in reducing the GHE and coming up with more environmentally friendly PLA. Another suggestion to make PLA a low-carbon material is to develop recycling facilities to obtain new PLA products from the recycled PLA, of good quality and acceptable properties. By recycling, the EoL emissions, which are of considerable amounts, will be removed from the calculations.
Unlike fossil-based polymers, bio-based polymers derived from renewable origins offer more CO2 absorption during their production process. However, the production of bio-based polymers is still dependent on fossil fuels as the source of energy in their fabrication process. PLA is considered as one of the most prevalent and commercial bio-based polymers for numerous applications, with several EoL options, including mechanical recycling, chemical recycling, landfilling, and industrial composting. However, when the lifetime of PLA-based products is over, they will be mostly landfilled or composted. The lack of proper infrastructures for PLA processing leads to limitations to recycling them. There are several LCAs of PLA or comparing different plastics with PLA in terms of environmental aspects, energy demand, and GHE. By exploiting the LCAs of PLA, it can be optimized to be a more environmentally friendly material. The GHE attributed to the life cycle of PLA shows that the conversion of the bio-sources to lactic acid and then PLA is an energy-intensive process that releases a huge amount of CO2 to the atmosphere. According to the available data, more than 50% (2.8 kg CO2/kg PLA) of the released CO2 in the PLA life cycle belongs to its conversion. By optimizing the conversion process of PLA, there will be a high potential to make PLA a low-carbon material.
Conceptualization, E.R.G., F.K., A.S.A., Y.D., R.E.N., F.F., M.W., O.D., and S.R.; methodology, E.R.G., F.K., and A.S.A.; validation, E.R.G., Y.D., R.E.N., O.D., and S.R.; investigation, E.R.G., F.K., and A.S.A.; writing&#;original draft preparation, E.R.G., F.K., A.S.A., and R.E.N.; writing&#;review and editing, E.R.G., F.K., A.S.A., Y.D., R.E.N., F.F., M.W., O.D., and S.R.; supervision, Y.D., R.E.N., O.D., and S.R. All authors have read and agreed to the published version of the manuscript.
This work was financially supported by the Project of Six Talents Climax Foundation of Jiangsu (XCL-082), Innovation Platform Project Supported by Jiangsu Province (), and Nanjing Jinsibo Nano Technology Co., Ltd. (Nanjing, China).
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The data presented in this study are available upon request from the corresponding author.
The authors declare no conflict of interest.
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The data presented in this study are available upon request from the corresponding author.
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