Impact of Biodegradable Plastics on Soil Health: Influence of Global Warming and Vice Versa

Abstract

The presence of plastics in the soil environment is an undeniable global reality. Biodegradable plastics (BPs) possess several key properties that make them more environmentally sustainable compared to other categories of plastics. However, their presence induces significant changes in soil systems health where they are found, due to a combination of environmental, soil, and climatic factors, as well as the simultaneous presence of other pollutants, both inorganic and organic. In the present work, a review has been conducted on published research findings regarding the impact of various types of BPs on the parameters that regulate and determine soil health. In particular, the study examined the effects of BPs on physical, chemical, and biological indices of soil quality, leading to several important conclusions. It was observed that silty and loamy soils were significantly affected, as their physical properties were altered. Moreover, significant changes in both chemical and microbiological indicators were observed with increasing environmental temperatures. The presence of all types of biodegradable microplastics led to a significant reduction in soil nitrogen content as temperature increased. This study highlights the profound effects of the climate crisis on the properties of soils already contaminated with plastics, as the effects of rising temperatures on soil properties appear to be amplified in the presence of plastics. On the other hand, higher temperatures also trigger a series of chemical reactions that accelerate the degradation of BPs, thereby reducing their volume and mass in the soil environment. These processes lead to increased emissions of gases and higher ambient temperatures, leading to global warming. The types and quantities of plastics present, along with the environmental changes in a study area, are critical factors that must be taken into account by policymakers in order to mitigate the impacts of climate change on soil health and productivity.

1. Introduction

With the rapid development that the world experienced as a result of the Industrial Revolution, new materials have come into people’s lives that create problems both for the environment and for the people themselves. A category of materials are plastics, and more particularly, the biodegradable ones, which have been in the research spotlight for some time now. These primarily create a problem due to the degradation of their polymers in the soils in which they exist in the form of pollutants [1]. This is a common phenomenon observed in agricultural holdings, even in the produced crops and in their fruits in the form of micro- and nano-plastics [2,3]. A number of plastics, like polyvinyl chloride and polystyrene, can be hazardous for human health due to their toxicity and carcinogenic properties. While micro-plastics have been traced in human tissues, their health effects at environmental exposure levels are unclear [4].

The issue of agricultural plastic pollution is widespread, and it is exacerbated by the use of plastic mulches in the cultivation of various specialty crops such as vegetables and fruits [5]. Plastic films are increasingly being utilized for agricultural mulching on a global scale. This practice not only enhances crop yield but also reduces the need for pesticides, conserves irrigation water, and helps address the food requirements of the expanding global population [6]. Because of polyethylene (PE) fragments, the increased usage of plastic mulches has resulted in significant waste problems and irreversible soil pollution [7,8,9]. According to Steinmetz et al. [10], plastic fragments can have detrimental effects on the food chain, impede agricultural productivity, and linger in the soil as pollutants [8], with negative effects on soil health and quality [11,12,13]. In addition, Zhang et al. [14] found that a 1% concentration of low-density polyethylene (LDPE) in soil significantly elevated CO₂ emissions by 15 to 17%, while lower concentrations did not exhibit a significant impact [15].

Limited disposal options for conventional mulch like PE have led to a growing interest in the use of soil-biodegradable plastic (SBP) mulch. Nevertheless, there is a lack of information regarding the environmental impact of the continuous utilization of soil-biodegradable plastic mulch [16]. BPs offer an alternative to synthetic plastics; however, not all of them can fully decompose in natural settings. In some cases, they may degrade into microplastics (MPs) more rapidly than regular (synthetic) plastics, which can pose a higher risk to the soil [17]. Even if BPs are not a perfect response to the problem of plastic pollution, it is important to learn more about how they are made, how they affect the environment and the ecosystem, and whether they are worse than regular plastics [17].

For instance, the phenomenon of global warming, which has arisen due to a substantial rise in greenhouse gas (GHG) emissions since the onset of the Industrial Revolution, has emerged as a critical global challenge [18]. According to estimates from the Intergovernmental Panel on Climate Change [19], the Earth’s surface temperature is projected to increase from 1.5 to 1.6 °C by around the year 2040 [18]. Consequently, the capacity for methane (CH₄) generation in landfills plays a crucial role in the global warming effects linked to biopolymers, whereas recycling offers substantial advantages in mitigating global warming and reducing fossil fuel depletion [20]. In addition, BPs, in particular, have the potential to elevate CO₂ emissions in soil environment. This phenomenon can be attributed to their influence on both the physical and chemical characteristics of the soil, as well as the degradation processes they undergo, which contribute to additional CO₂ release [15]. Beyond the existing knowledge, however, there are no clear studies on the impact of the climate crisis on the erosion of biodegradable plastics in soils, or on their effects on soil health.

In this study, an attempt was made to investigate the effects of biodegradable and bio/based micro-plastics on the physical, chemical, and microbiological properties of soils. Climate change, with its dramatic increases in temperature and frequent changes in humidity conditions, seems to influence or even stimulate a series of changes in soils due to the presence of plastics. On the other hand, plastics are undergoing changes in their chemical composition, releasing gases and probably contributing to climate change. The key aim of this study is to examine this two-way relationship.

2. Biodegradable Plastics (BPs): A Terminology Discussion

BPs can be manufactured using both bio-based and petroleum-derived raw materials. Conversely, certain plastics derived from petroleum are also capable of biodegradation [21]. However, it is critical to distinguish between compostable, biodegradable, and degradable materials. In both the general public and scientific journals, the term “bioplastic” is often used [22]. However, the word “bioplastic” can refer to either the plastic’s biobased origin or its biodegradable characteristics. The name “bioplastic” is misleading since these two characteristics of plastic are not interchangeable [22]. Bio-based plastics are made from biomass, usually involving the use of plants as raw materials [23]. Due to their natural source, it is easy to mistakenly think that these plastics are also biodegradable. Moreover, the word “bioplastics” refers to plastic that has a biobased origin and/or is biodegradable, according to the Organization of European Bioplastics [24]. Bioplastics are bio-based, biodegradable, or both (Figure 1). The European Standard EN 16575 from 2014 defines bio-based plastics as those made from plant-based resources, also referred to as biomass [25]. As per the International Union of Pure and Applied Chemistry (IUPAC), a bioplastic is obtained from “biomass or monomers derived from biomass and has the ability to be molded through flow during its transformation into final products.” It is crucial to differentiate between degradable, biodegradable, and compostable materials [22].

However, the biodegradability of a plastic depends on its specific properties, such as chemical structure and crystallinity; on a similar note, some petroleum-based plastics can also be biodegradable [23]. Different types of biodegradable polymers can be distinguished based on the sources and synthesis procedures used. According to Zhong et al. [26], these materials can be acquired directly from biomass, such as proteins and polysaccharides. Alternatively, they can be synthetic biopolymers derived from biomass, such as poly(lactic acid) (PLA), or from petrochemicals, such as polycaprolactone (PCL), poly(glycolic acid) (PGA), and poly(butylene succinate-co-adipate) (PBSA). Another source of these materials is microbial fermentation, which produces poly(hydroxyalkanoates) (PHA) and poly(hydroxybutyrate) (PHB) [26]. Bio-based plastics, although not biodegradable, are designed to closely resemble traditional petro-based plastics in terms of structure. These innovative materials (e.g., bio-PET and bio-PE) are considered convenient drop-in solutions due to their similar properties to their petro-based counterparts. However, these plastics often have low feedstock efficiency or still contain petroleum-based monomers [23].

Bio-based polymers are typically classified into three distinct categories: (i) polymers that are produced by modifying naturally occurring polymers, often sourced from agricultural materials, (ii) polymers that are generated through microbial processes, and (iii) polymers that are synthesized from precursors derived from biological feedstocks [27]. A universally recognized definition of bio-based plastics has not yet been formulated. It is crucial to understand that bio-based plastics do not inherently signify sustainability; the sustainability of such materials depends on multiple factors, including the origin of the raw materials, the manufacturing processes utilized, and the strategies for managing the materials at the end of their lifecycle [28]. Kabasci [29] provides a precise definition of ‘bio-based plastics,’ which specifically pertains to plastics that are produced from biomass. The term ‘bioplastics’ can often lead to confusion, as the prefix ‘bio’ not only indicates the source of the material (‘bio-based’) but may also suggest a ‘bio’ functionality, which can encompass biodegradability or biocompatibility. Bioplastics are defined as plastics that are sourced from renewable materials (referred to as ‘bio-based’), have the capacity to biodegrade, are manufactured through biological processes, or exhibit a combination of these traits. It is crucial to recognize that some BPs derived from fossil fuels may also fall under the category of bioplastics; however, this classification is generally discouraged due to its potential to mislead. Currently, the production of fully bio-based bioplastics is estimated to be around 2 million tonnes per year [30].

According to the international biodegradability standard EN-17033, an aerobic incubation at a constant temperature of 20–28 °C must result in 90% degradation of soil-biodegradable agricultural plastic mulch films within two years; in other words, it must have converted to CO₂ in topsoil. However, laboratory biodegradability does not ensure that the same processes will occur in the field. To evaluate biodegradable mulches in a variety of environmental settings and gather data specific to a given site in order to forecast degradation, field test protocols are required [31,32]. Quantification of CO₂ released from plastic polymers is necessary for the verification of biodegradation, but this has not yet been attempted due to its difficulty in field conditions [32].

3. Global Warming

The careful analysis of the implementation of BPs is crucial from an environmental perspective. Among the different factors to consider, the primary one is the global warming potential (GWP), which examines CO₂ emissions throughout the entire process. Plant-based BPs are commonly assumed to have a neutral or even negative carbon footprint. Nevertheless, in life cycle assessments (LCAs) that calculate carbon emissions, the negative impacts such as land use and by-products, as well as carbon emissions during the manufacturing process, are frequently overlooked [23].

In natural landfills and manure, biodegradable plastic can break down into CO₂ and H₂O within a span of 20–45 days. This is possible due to the presence of adequate humidity, oxygen, and the right number of microorganisms [33]. However, some bio-based plastics may not be biodegradable; while certain types can degrade, others require specific industrial conditions for biodegradation to occur [34]. The term ‘bioplastics’ is commonly utilized to refer to both bio-based plastic and biodegradable plastic [35]. Nevertheless, the fact that an item is biodegradable does not imply that it can be carelessly discarded into the environment without proper management. It is imperative to establish more explicit guidelines for the disposal of BPs [35].

Furthermore, as stated by Ford et al. [35], the production of plastic will result in the release of over 56 billion tons of CO₂ equivalent into the atmosphere between 2015 and 2050. This accounts for approximately 13% of the total projected CO₂ emissions worldwide during this time period [36]. Another scientific article shows that the production of plastic accounts for approximately 5–7% of the world’s oil consumption and emitted over 850 million tonnes of CO₂ into the atmosphere in 2019, which constitutes 2% of total global CO₂ emissions. The predominant sources of CO₂ emissions related to plastic are the extraction of raw materials (61%) and the production of polymers (30%), with a mere 9% attributed to the end-of-life (EOL) phase, primarily through incineration. Additionally, unregulated open burning of plastic waste may contribute more than 1 gigaton of CO₂ equivalent emissions to these figures [30]. It is crucial to acknowledge that the rise in CO₂ concentration is a contributing factor to global warming, leading to adverse effects such as more severe droughts, rising sea levels, alterations in Earth’s geography, heightened fire occurrences, and increased desertification [36]. Studying the impacts of long-term and episodic sea level rise (SLR) under different scenarios in critical resource areas (Aegean archipelago, Eastern Mediterranean), Monioudi et al. [37] noted the local, as well as the national, negative economic effects. In the near future (2021–2040), global warming will rise mostly as a result of higher total CO₂ emissions in almost all scenarios and simulated routes [38].

Global warming is leading to significant shifts in the Earth’s climate, resulting in record-breaking heatwaves in southern Europe, China, and many areas of North America. Additionally, heatwaves took place in the summer of 2023 in the Northern Hemisphere. These heatwaves occurred towards the end of a long-lasting cool phase called La Niña. It is worth noting that global mean temperatures were lower than the long-term warming trend during this period. Along with this, the El Niño–Southern Oscillation (ENSO) shift to a warmer-than-average El Niño phase from 2023 to 2024 indicates that we may now expect intense heatwaves and related extreme events to become the prevailing pattern [39].

Two of the main components of greenhouse gases are CO₂ and nitrous oxide (N₂O). The terrestrial ecosystem, on the one hand, serves as a significant sink, with contributions such as forest soils that can trap CO₂. N₂O, on the other hand, is mostly emitted from manure and nitrogen fertilizer in agricultural soils. On a molar basis, N₂O has about 300-fold more capacity to cause global warming than CO₂. Additionally, N₂O destroys the stratospheric ozone layer [40,41].

According to the United States Environmental Protection Agency (EPA) [42], approximately 40% of global N₂O emissions are attributed to human activities. These emissions primarily arise from agricultural practices, transportation, and industrial operations. While N₂O naturally exists in the atmosphere as a component of the Earth’s nitrogen cycle and has several natural sources, human activities—including agriculture, the burning of fossil fuels, wastewater treatment, and various industrial processes—are contributing to an increase in atmospheric N₂O levels. On average, N₂O molecules remain in the atmosphere for about 120 years before they are either absorbed by a sink or decomposed through chemical reactions. Agriculture plays a significant role in the emission of nitrous oxide, particularly when nitrogen is introduced into the soil via synthetic fertilizers. In 2011, agricultural soil management was identified as the predominant source of N₂O emissions in the United States, responsible for approximately 69% of the total emissions [42].

4. Agriculture Biodegradable Plastics (ABPs)

Based on recent research [43], BPs that are usually used in agriculture practices are poly(lactic acid) (PLA), poly(butyleneadipatecoterephthalate) (PBAT), poly (butylene succinate) (PBS), polyhydroxyalkanoates (PHA), ethylene-vinyl acetate (EVA), and poly propylene carbonate (PPC). BPs, like mulch film, are increasingly utilized in the field of agriculture. They produce MPs and release plastic additives due to their degradation [44]. BPs have the potential to enter the soil, which could lead to ecotoxicological hazards [45]. Improper management and disposal of EOL BPs can result in them becoming litter in the open environment, eventually finding their way into natural habitats such as lakes, oceans, and soils [46]. A consistent quantity of biodegradable mulch remains in the soil following yearly application [32].

According to Meng et al. [47], soil dissolved organic carbon contents were affected by the degradation of BPs. Moreover, synchronization between the biodegradation process and the temporal dynamics of bacterial communities was observed.

Table 1 presents a summary of findings regarding the effects of biodegradable and bio-based plastics on the physical properties of various soil types. In some cases, specific details concerning the type of plastic and characterization of the soil were not available.

Based on studies of similar soil textures (i.e., sandy loam), Sintima et al. [16] and Slezak et al. [48] observed several changes in environmental conditions, including increased aggregate stability and altered soil microclimate. Furthermore, they found significant effects on groundwater quality, as well as changes in plastics, including color changes, surface sample erosion, sample mass loss, and thickness alterations; tensile strength decreased for two different PLA samples but increased for PBS.

Degradation of bioplastic films was also observed in loam soil [49]. According to the study, bioplastic films usually increased soil temperature, while the quantity of bio-mulch retrieved from the soil (measured in grams per square meter of surface area) differed based on the specific bio-mulch product and the date of sampling. However, mulches generally remained intact during the growing season (silt loam soil) except for the paper mulch in Shady–Whitwell complex soil, which likely was weakened by high moisture exposure. Finally, Men et al. [50], using bulk soil, found that the film color revealed a direct correlation with soil temperature, thereby affecting plant performance.

There was no specific information about soil texture in the other studies in Table 2. The main physical results were summarized as follows. (1) Weight loss was observed [47,51]. Specifically, it occurred most rapidly with the polyhydroxybutyrate (PHB) film, then with the potato thermoplastic starch–copolyester, and lastly with the cereal flour–copolyester [51]. (2) The soil was completely decomposed and exhibited excellent tensile straightness [52]. (3) BDMs and black PEM reduced soil temperature [53]. (4) BP decreased soil temperature but also increased soil moisture [54]. (5) UV-blocking performance [55] and (6) the degradation rate of bioplastics (PLA and PBS) were enhanced alongside an increase in bacterial biomass within the soil [56].

The biodegradation process was characterized by the breaking down of mulch, the release of various compounds, and the soil microbiome’s consumption of plastic components [6]. Based on a study of loessial soil, the abundance of bacterial communities in soil with varying PBAT levels exhibited a significant correlation with the physical and chemical properties of the soil [57].

Table 1. Effects of biodegradable/bio-based plastics on soil physical properties.

Type of Biodegradable/Bio-Based Plastic	Type of Soil	Effects on Plastics	Effects on Soils	References
PBS-starch, PBS, PLA.	Agricultural fields in Japan.		The degradation of bioplastics did not affect nitrogen circulation activity in the soil.	[56]
Compostable bags: biopolymer based on starch and vinyl-alcohol copolymers (Mater-bi® [MB]).	Natural soil.		Harmful chemicals leached from the bags, negatively impacting water quality.	[58]
BDM (BioAgri®, Naturecycle, and Organix A.G. Film™) and one experimental film comprised of a blend of PLA and PHA were tested alongside a PE mulch (negative control) and cellulose paper mulch (WeedGuard Plus®, positive control).	Sandy loam and silt loam.		Locational and seasonal variations play a more significant role in influencing changes in soil health during BDM tillage operations.	[59]
PLA.	Loam and clay soil.	An increase of PLA crystallization under wet conditions.	Minor influence of the soil texture was observed.	[2]
Mater-bi M15 (mulching grade, 15 μm thick) and Ecovio M12 (mulching grade, 12 μm thick).	Not specific.	Differences in the penetration and impact resistance, tensile strength, and degradation behavior. Overall functionality of the bio-based mulching films was found to be satisfactory.	Higher water vapor permeability.	[60]
PHA-based grow bags; bioplastics in mulch films.	-	PHA-based grow bags would be biodegradable, root-friendly, and non-toxic to the surrounding water bodies.	Bioplastics in mulch films are essential to uphold exceptional soil structure, retain moisture, control weeds, and prevent contamination, in substitution of fossil-based plastics.	[61]
BMPs.	Not specific.		BMPs had different or more severe effects compared to conventional MPs.	[17]
PLA/PHA blend and paper mulch.	Silt loam (Mount Vernon) and well-drained Shady–Whitwell complex soil (Knoxville).	The paper mulch in Knoxville, which likely was weakened by high moisture exposure.	All mulching treatments were effective in suppressing weeds compared to bare soil.	[62]
PBAT.	Loessial soil.		The lower amount of PBAT relatively increased the diversity of soil bacterial communities, and the relative abundance of the unique Azotobacter increased with increasing PBAT amounts. The abundance of bacterial community in soil with different PBAT amounts was significantly correlated with the soil’s physical–chemical properties.	[57]
PLA (bio-based, compostable) and PBAT (fossil-based, biodegradable).	Soils were collected from farmlands in China.	(1) Weight loss of the plastics. (2) Formation of distinct bacterial communities in the plastic surface soil.	Drastic increase in soil dissolved organic carbon.	[47]
PBAT and PLA in three different colors.	Bulk soil.		Film color was discovered to have a direct impact on soil.	[50]
BPs using different combinations of naturally occurring polymers from fruit and vegetable wastes.	-	Totally decomposed with good tensile straightness.		[52]
BMPs.	Not specific.		BMPs pose stronger negative effects than conventional MPs under some conditions.	[45]
BioAgri (20–25% starch), PLA, and PHA.	Sandy loam.		Increased aggregate stability, modified the soil microclimate, and affected groundwater quality.	[15]
PLA with polybutylene adipate terephthalate and additives (PLA_1), PLA-based polyester blend with mineral filler (PLA_2), and polybutylene succinate with mineral filler (PBS_1).	Sandy loam soil.	(1) After a year of deterioration, macroscopic examination revealed that samples PBS_1 had color changes in the film surface. (2) Mass loss of the samples after one year of degradation. (3) Changes in the thickness. (4) Thermal stability was decreased. (5) Tensile strength for PLA_1 and PLA_2 was decreased, while for PBS_1, it was increased. (6) After a year, the erosion of surface samples PLA_1 and PBS_1 was observed under a microscope.		[46]
Comparison of BDMs relative to black PEM.	Different soils.		BDMs reduced soil temperature by 4.5 ± 0.8% (±one standard error) compared to PEM, and temperatures were coolest beneath paper-based BDM.	[53]
Νon-woven biofabrics of varying thickness and color (3M Co., Saint Paul, MN), Eco Film bioplastic mulch film (Cortec Corp., Saint Paul, MN), and Bio Telo bioplastic mulch film (Dubois Agrinovation, Saint-Remi, QC, Canada).	Loam soil.	(1) Deterioration of bioplastic films increased over time in the field. (2) The amount of bio-mulch recovered from soil (grams per square meter of surface area) varied according to bio-mulch product and sampling date, but there was no interaction between the two effects.	Surface soil moisture, averaged across the season, increased beneath all bio-mulches compared with bare soil in all trials. No weeds emerged through bio-mulches in either environment.	[63]
PBAT.	Loamy brown soil.	At an accumulated UV irradiation of 2.1 MJ/m2, the mean number of large-sized microplastics released from biodegradable mulch films was 475 particles/cm2, ranging from 0.02 to 0.10 mm.		[63]
BP (biodegradable paper made from plant straw) and BB (bio-based film made from plant straw combined with decomposed coal).	Surface soil of the greenhouse with pH = 8.43.		BB mulching decreased soil temperature; however, it decreased soil moisture and invertase and increased soil EC, leading to reduced root growth (root diameter and biomass, and the root/shoot ratio).	[54]
Biobased transparent wood film TA/Gelatin/TWF.	Natural soil.	(1) Wet strength (significantly higher than conventional petroleum-based plastics). (2) UV-blocking performance. (3) It can break down in 5 months, effectively balancing material strength and degradability.		[55]
BioAgri, Organix, Naturecycle, PLA/PHA, and cellulosic paper mulch.	Not specific in 2 different climate regions: (1) humid subtropical climate and (2) cool Mediterranean climate.	In soil, the rate of degradation in the biodegradable plastic mulches was initially low and increased after about 1.5 years. Among the biodegradable plastic mulches, PLA/PHA degraded the slowest during the initial stages.		[64]
PPDO, PLA, PBAT, 40% mineral doped polyethylene (MD40), PLA_blend (50% of PLA + 50% polyethylene), and PBAT_blend (90% PBAT + 10% PLA).	Agriculture paddy soil.	The degradation levels were slow under natural air and soil environmental conditions.		[65]
Biodegradable paper (BP) and bio-based film (BB).	Surface soil of the greenhouse with pH = 8.43.		BB mulching decreased soil temperature; however, it decreased soil moisture and invertase and increased soil EC.	[54,66]
Bio-MPs.	Not specific.	Nanoplastics are simple to create.	Act as labile C sources to stimulate microbial growth and soil N and P cycling.	[67]

Table 1. Effects of biodegradable/bio-based plastics on soil physical properties.

Type of Biodegradable/Bio-Based Plastic	Type of Soil	Effects on Plastics	Effects on Soils	References
PBS-starch, PBS, PLA.	Agricultural fields in Japan.		The degradation of bioplastics did not affect nitrogen circulation activity in the soil.	[56]
Compostable bags: biopolymer based on starch and vinyl-alcohol copolymers (Mater-bi® [MB]).	Natural soil.		Harmful chemicals leached from the bags, negatively impacting water quality.	[58]
BDM (BioAgri®, Naturecycle, and Organix A.G. Film™) and one experimental film comprised of a blend of PLA and PHA were tested alongside a PE mulch (negative control) and cellulose paper mulch (WeedGuard Plus®, positive control).	Sandy loam and silt loam.		Locational and seasonal variations play a more significant role in influencing changes in soil health during BDM tillage operations.	[59]
PLA.	Loam and clay soil.	An increase of PLA crystallization under wet conditions.	Minor influence of the soil texture was observed.	[2]
Mater-bi M15 (mulching grade, 15 μm thick) and Ecovio M12 (mulching grade, 12 μm thick).	Not specific.	Differences in the penetration and impact resistance, tensile strength, and degradation behavior. Overall functionality of the bio-based mulching films was found to be satisfactory.	Higher water vapor permeability.	[60]
PHA-based grow bags; bioplastics in mulch films.	-	PHA-based grow bags would be biodegradable, root-friendly, and non-toxic to the surrounding water bodies.	Bioplastics in mulch films are essential to uphold exceptional soil structure, retain moisture, control weeds, and prevent contamination, in substitution of fossil-based plastics.	[61]
BMPs.	Not specific.		BMPs had different or more severe effects compared to conventional MPs.	[17]
PLA/PHA blend and paper mulch.	Silt loam (Mount Vernon) and well-drained Shady–Whitwell complex soil (Knoxville).	The paper mulch in Knoxville, which likely was weakened by high moisture exposure.	All mulching treatments were effective in suppressing weeds compared to bare soil.	[62]
PBAT.	Loessial soil.		The lower amount of PBAT relatively increased the diversity of soil bacterial communities, and the relative abundance of the unique Azotobacter increased with increasing PBAT amounts. The abundance of bacterial community in soil with different PBAT amounts was significantly correlated with the soil’s physical–chemical properties.	[57]
PLA (bio-based, compostable) and PBAT (fossil-based, biodegradable).	Soils were collected from farmlands in China.	(1) Weight loss of the plastics. (2) Formation of distinct bacterial communities in the plastic surface soil.	Drastic increase in soil dissolved organic carbon.	[47]
PBAT and PLA in three different colors.	Bulk soil.		Film color was discovered to have a direct impact on soil.	[50]
BPs using different combinations of naturally occurring polymers from fruit and vegetable wastes.	-	Totally decomposed with good tensile straightness.		[52]
BMPs.	Not specific.		BMPs pose stronger negative effects than conventional MPs under some conditions.	[45]
BioAgri (20–25% starch), PLA, and PHA.	Sandy loam.		Increased aggregate stability, modified the soil microclimate, and affected groundwater quality.	[15]
PLA with polybutylene adipate terephthalate and additives (PLA_1), PLA-based polyester blend with mineral filler (PLA_2), and polybutylene succinate with mineral filler (PBS_1).	Sandy loam soil.	(1) After a year of deterioration, macroscopic examination revealed that samples PBS_1 had color changes in the film surface. (2) Mass loss of the samples after one year of degradation. (3) Changes in the thickness. (4) Thermal stability was decreased. (5) Tensile strength for PLA_1 and PLA_2 was decreased, while for PBS_1, it was increased. (6) After a year, the erosion of surface samples PLA_1 and PBS_1 was observed under a microscope.		[46]
Comparison of BDMs relative to black PEM.	Different soils.		BDMs reduced soil temperature by 4.5 ± 0.8% (±one standard error) compared to PEM, and temperatures were coolest beneath paper-based BDM.	[53]
Νon-woven biofabrics of varying thickness and color (3M Co., Saint Paul, MN), Eco Film bioplastic mulch film (Cortec Corp., Saint Paul, MN), and Bio Telo bioplastic mulch film (Dubois Agrinovation, Saint-Remi, QC, Canada).	Loam soil.	(1) Deterioration of bioplastic films increased over time in the field. (2) The amount of bio-mulch recovered from soil (grams per square meter of surface area) varied according to bio-mulch product and sampling date, but there was no interaction between the two effects.	Surface soil moisture, averaged across the season, increased beneath all bio-mulches compared with bare soil in all trials. No weeds emerged through bio-mulches in either environment.	[63]
PBAT.	Loamy brown soil.	At an accumulated UV irradiation of 2.1 MJ/m2, the mean number of large-sized microplastics released from biodegradable mulch films was 475 particles/cm2, ranging from 0.02 to 0.10 mm.		[63]
BP (biodegradable paper made from plant straw) and BB (bio-based film made from plant straw combined with decomposed coal).	Surface soil of the greenhouse with pH = 8.43.		BB mulching decreased soil temperature; however, it decreased soil moisture and invertase and increased soil EC, leading to reduced root growth (root diameter and biomass, and the root/shoot ratio).	[54]
Biobased transparent wood film TA/Gelatin/TWF.	Natural soil.	(1) Wet strength (significantly higher than conventional petroleum-based plastics). (2) UV-blocking performance. (3) It can break down in 5 months, effectively balancing material strength and degradability.		[55]
BioAgri, Organix, Naturecycle, PLA/PHA, and cellulosic paper mulch.	Not specific in 2 different climate regions: (1) humid subtropical climate and (2) cool Mediterranean climate.	In soil, the rate of degradation in the biodegradable plastic mulches was initially low and increased after about 1.5 years. Among the biodegradable plastic mulches, PLA/PHA degraded the slowest during the initial stages.		[64]
PPDO, PLA, PBAT, 40% mineral doped polyethylene (MD40), PLA_blend (50% of PLA + 50% polyethylene), and PBAT_blend (90% PBAT + 10% PLA).	Agriculture paddy soil.	The degradation levels were slow under natural air and soil environmental conditions.		[65]
Biodegradable paper (BP) and bio-based film (BB).	Surface soil of the greenhouse with pH = 8.43.		BB mulching decreased soil temperature; however, it decreased soil moisture and invertase and increased soil EC.	[54,66]
Bio-MPs.	Not specific.	Nanoplastics are simple to create.	Act as labile C sources to stimulate microbial growth and soil N and P cycling.	[67]

Table 2 presents a summary of findings regarding the effects of biodegradable and bio-based plastics on the chemical properties of soils. In certain cases, specific details concerning the type of plastic and characterization of the soil were not available.

When studying PBAT in sandy loam and loamy soil, Rauscher et al. [15] observed CO₂ emissions (13–57%). According to the findings of Guliyev et al. [68] (the study focused on PBSA, haplic chernozem, and silt loam), the process of plastic decomposition resulted in a loss of carbon from soil organic matter (SOM) due to priming effects, which were influenced by the addition of nitrogen. The presence of nitrogen enhanced the decomposition of PBSA and mitigated the priming effect during the initial six weeks of the study. Over the course of 80 days of plastic decomposition, it was observed that 30% and 49% of the emitted CO₂ originated from PBSA, while CO₂ released from SOM exceeded control levels by 100.2% and 132.3% in soils amended with PBSA, with and without nitrogen fertilization, respectively. Ultimately, only 4.1% and 5.4% of the PBSA introduced into the soil was converted to CO₂ in the treatments lacking and including nitrogen amendment, respectively.

Negative water properties, including pH, salinity, and total dissolved solids, which are significant for plant health, were also observed during the testing of bag samples. Additionally, these bags can leach harmful chemicals, such as bisphenol A and other phytotoxic compounds that may be produced during the manufacturing process, into the water [58]. Based on the research, plastic bags in general, even those that comply with biodegradability and compostability criteria, pose a potential risk to plant life if they are discarded in natural settings. Furthermore, the impact on groundwater quality was observed by examining PHA, BioAgri (20–25% starch), and PBAT materials [16], while PLA caused higher Cd bioavailability [69]. CPMF introduced many MPs, DMP, DEP, and DBP into the soil and endangered the soil environment [70]. Effects on nitrification activity were measured by a black material that is composed of corn starch and biodegradable copolyesters [71].

Moreover, there has been a significant rise in dissolved organic carbon content in soil due to PLA and PBAT [47], the addition of PHBV created soil hotspots where C and nutrient turnover is greatly enhanced [72]. Using PHA starch-based plastics and materials made from compost, substantial mineralization was also observed [73]. Photosynthesis and the accumulation of other nutrients, such as soluble sugars and nitrate nitrogen, were hindered [14]. Nevertheless, biodegradable plastics using different combinations of naturally occurring polymers from fruit and vegetable wastes were totally decomposed [52].

Table 2. Effects of biodegradable/bio-based plastics on soil chemical properties.

Type of Biodegradable/Bio-Based Plastic	Type of Soil	Effects in Plastics	Effects on Soils	References
PBS-starch, PBS, and PLA.	Agricultural fields in Japan.	The rate of bioplastic degradation was enhanced, accompanied by an increase of bacterial biomass in the soil.	The degradation of bioplastics did not affect the nitrogen circulation activity in the soil.	[56]
PCL, PHB, PLA, and PBS.	Not specific.	PCL showed the fastest degradation rate under all conditions.		[74]
Mater-bi® (MB).	Natural soil.		Both types of bags affected water characteristics (pH, salinity, and total dissolved solids) relevant to plants, and released into water intentionally added chemicals, such as the noxious bisphenol A, and other phytotoxic substances.	[58]
PLA, starch-based plastics, and materials made from compost.	A mixture of 43% certified organic topsoil, 43% no-till farm soil, and 14% sand.		Substantial mineralization was observed.	[71]
PBSA.	Haplic Chernoze, silt loam	CO2 emissions resulting from the decomposition of PBSA.	The degradation of the plastic resulted in the loss of carbon from soil organic matter (SOM).	[68]
PBAT.	Loessial soil.		The abundance of bacterial community in soil with different PBAT amounts was significantly correlated with the soil’s physical–chemical properties.	[57]
BDP (made of Mater-bi, grade EF04P) in the form of pellets).	Loamy (cambisol).		The highest dose of BDP (P10000) led to higher C mineralization and enhanced the immobilization of available nitrogen.	[75]
PLA (bio-based, compostable) and PBAT (fossil-based, biodegradable).	Soils were collected from farmlands in China.	Weight loss of the plastics and formation of distinct bacterial communities on the plastic surface.	Drastic increase in soil dissolved organic carbon.	[47]
BPs using different combinations of naturally occurring polymers from fruit and vegetable wastes.	-	Totally decomposed with good tensile straightness.		[52]
PBAT.	Sandy loam and loamy soil.		CO2 emissions (13–57%), microbial biomass (1–7%), and a shift in community composition were induced.	[15]
BioAgri (20–25% starch), PLA, and PHA.	Sandy loam.		Increased aggregate stability. Modified the soil microclimate. Affected groundwater quality.	[16]
PLA.	Soil from farmland.		PLA caused higher Cd bioavailability.	[69]
Bio-PMF.	Field continuously cropped with peanuts (not specific type).		CPMF stably enhanced peanut yield by improving soil–peanut ecology but introduced many MPs, DMP, DEP, and DBP into the soil and endangered the soil environment. However, without introducing plastic pollutants, Bio-PMF slightly increased peanut yield by partially altering soil–peanut ecology.	[70]
PBAT/polylactic acid PLA.	Black soil, red earths, and desert soil.		The bacterial communities and metabolites of all three soils were negatively affected.	[76]
PBSA film.	Loam, clay loam, and sandy loam textures from alluvial and volcanic ash cultivated fields.		The findings indicate that as the distribution ratio of native PBSA/degrading fungi in the soil increases, the degradation of the film becomes faster.	[77]
BP (biodegradable paper made from plant straw) and BB (bio-based film made from plant straw combined with decomposed coal).	Surface soil of the greenhouse with pH = 8.43.		BB mulching decreased the soil temperature; however, it decreased soil moisture and invertase and increased soil EC, leading to reduced root growth (root diameter and biomass, and the root/shoot ratio). BP mulching not only decreased soil temperature but also increased soil moisture. The fruit quality was partly improved by BP mulching due to reduced nitrate but increased vitamin C.	[66]
PEF.	Rhizosphere soil (of lettuce [Lactuca sativa L.]) and bulk soil.		Inhibited the growth of lettuce and the photosynthesis and the accumulation of other nutrients (e.g., soluble sugar and nitrate nitrogen). Influenced soil enzyme activities and bacterial community.	[14]
PHBV poly (3-hydroxybutyrate-co-3-hydroxyvalerate).	Ap horizon (0–20 cm) of an experimental field pH 6.8.		Increased the specific microbial growth rate and a more active microbial biomass. PHBV changed the soil bacterial community at different taxonomical levels. PHBV addition created soil hotspots where C and nutrient turnover is greatly enhanced.	[72]
Bio-MPs.	Not specific.		Act as labile C sources to stimulate microbial growth and soil N and P cycling. Bio-MPs form nanoplastics much more easily and are more toxic to plants.	[67]
Mater-bi DF04P, a black material that is composed of corn starch, and biodegradable copolyesters from Novamont.	Agriculture soil.		Affected nitrification activity.	[71]

Table 2. Effects of biodegradable/bio-based plastics on soil chemical properties.

Type of Biodegradable/Bio-Based Plastic	Type of Soil	Effects in Plastics	Effects on Soils	References
PBS-starch, PBS, and PLA.	Agricultural fields in Japan.	The rate of bioplastic degradation was enhanced, accompanied by an increase of bacterial biomass in the soil.	The degradation of bioplastics did not affect the nitrogen circulation activity in the soil.	[56]
PCL, PHB, PLA, and PBS.	Not specific.	PCL showed the fastest degradation rate under all conditions.		[74]
Mater-bi® (MB).	Natural soil.		Both types of bags affected water characteristics (pH, salinity, and total dissolved solids) relevant to plants, and released into water intentionally added chemicals, such as the noxious bisphenol A, and other phytotoxic substances.	[58]
PLA, starch-based plastics, and materials made from compost.	A mixture of 43% certified organic topsoil, 43% no-till farm soil, and 14% sand.		Substantial mineralization was observed.	[71]
PBSA.	Haplic Chernoze, silt loam	CO2 emissions resulting from the decomposition of PBSA.	The degradation of the plastic resulted in the loss of carbon from soil organic matter (SOM).	[68]
PBAT.	Loessial soil.		The abundance of bacterial community in soil with different PBAT amounts was significantly correlated with the soil’s physical–chemical properties.	[57]
BDP (made of Mater-bi, grade EF04P) in the form of pellets).	Loamy (cambisol).		The highest dose of BDP (P10000) led to higher C mineralization and enhanced the immobilization of available nitrogen.	[75]
PLA (bio-based, compostable) and PBAT (fossil-based, biodegradable).	Soils were collected from farmlands in China.	Weight loss of the plastics and formation of distinct bacterial communities on the plastic surface.	Drastic increase in soil dissolved organic carbon.	[47]
BPs using different combinations of naturally occurring polymers from fruit and vegetable wastes.	-	Totally decomposed with good tensile straightness.		[52]
PBAT.	Sandy loam and loamy soil.		CO2 emissions (13–57%), microbial biomass (1–7%), and a shift in community composition were induced.	[15]
BioAgri (20–25% starch), PLA, and PHA.	Sandy loam.		Increased aggregate stability. Modified the soil microclimate. Affected groundwater quality.	[16]
PLA.	Soil from farmland.		PLA caused higher Cd bioavailability.	[69]
Bio-PMF.	Field continuously cropped with peanuts (not specific type).		CPMF stably enhanced peanut yield by improving soil–peanut ecology but introduced many MPs, DMP, DEP, and DBP into the soil and endangered the soil environment. However, without introducing plastic pollutants, Bio-PMF slightly increased peanut yield by partially altering soil–peanut ecology.	[70]
PBAT/polylactic acid PLA.	Black soil, red earths, and desert soil.		The bacterial communities and metabolites of all three soils were negatively affected.	[76]
PBSA film.	Loam, clay loam, and sandy loam textures from alluvial and volcanic ash cultivated fields.		The findings indicate that as the distribution ratio of native PBSA/degrading fungi in the soil increases, the degradation of the film becomes faster.	[77]
BP (biodegradable paper made from plant straw) and BB (bio-based film made from plant straw combined with decomposed coal).	Surface soil of the greenhouse with pH = 8.43.		BB mulching decreased the soil temperature; however, it decreased soil moisture and invertase and increased soil EC, leading to reduced root growth (root diameter and biomass, and the root/shoot ratio). BP mulching not only decreased soil temperature but also increased soil moisture. The fruit quality was partly improved by BP mulching due to reduced nitrate but increased vitamin C.	[66]
PEF.	Rhizosphere soil (of lettuce [Lactuca sativa L.]) and bulk soil.		Inhibited the growth of lettuce and the photosynthesis and the accumulation of other nutrients (e.g., soluble sugar and nitrate nitrogen). Influenced soil enzyme activities and bacterial community.	[14]
PHBV poly (3-hydroxybutyrate-co-3-hydroxyvalerate).	Ap horizon (0–20 cm) of an experimental field pH 6.8.		Increased the specific microbial growth rate and a more active microbial biomass. PHBV changed the soil bacterial community at different taxonomical levels. PHBV addition created soil hotspots where C and nutrient turnover is greatly enhanced.	[72]
Bio-MPs.	Not specific.		Act as labile C sources to stimulate microbial growth and soil N and P cycling. Bio-MPs form nanoplastics much more easily and are more toxic to plants.	[67]
Mater-bi DF04P, a black material that is composed of corn starch, and biodegradable copolyesters from Novamont.	Agriculture soil.		Affected nitrification activity.	[71]

Table 3 presents a summary of findings regarding the effects of bioplastics on biological soil properties. In some cases, specific details concerning the type of plastic and characterization of the soil were not available.

Plastics (PLA, BioAgri in silt loam) reduced the activity of soil microorganisms [16], although distinct bacterial communities in the plastic surface soils were formed [47]. In other research, the rate of bioplastic degradation was enhanced, accompanied by an increase of bacterial biomass in the soil [56]. According to Li et al. [57], lower amounts of PBAT relatively increased the diversity of soil (loessial soil) bacterial communities, and the relative abundance of the unique Azotobacter increased with increasing PBAT amounts. The abundance of bacterial community in soils with different PBAT amounts was significantly correlated with the soil’s physical–chemical properties. Generally, the bacterial communities and metabolites in three types of soils—black soil, red earths, and desert soil—were negatively affected when testing PBAT and PLA [76].

The health of earthworms was affected [78]. In another scientific paper [79], earthworm avoidance behavior due to the presence of plastics in soil was observed for the first time in OECD soil [79], and PLA-based plastics caused the migration of earthworms to deeper soil layers [79]. This also affected the growth of plants [80].

Bio-MPs formed nanoplastics much more easily and were more toxic to plants [67]. According to the results of in vivo experiments, lettuce and tomato roots were more vulnerable than shoots and leaves [81]. Additionally, the fundamental characteristics of the soil were impacted, leading to a decreased germination rate of seeds and a reduction in shoot height [78]. PCL reduced plant production by 73.6–75.2%, while PBAT elicited almost negligible change in oxisols; shoot biomass was also reduced by PCL [82]. Research on a combination of PLA and PBAT in sandy soil revealed a notable decrease in leaf relative chlorophyll content, as well as reductions in both shoot and root biomass, leaf area, and fruit biomass. Additionally, there was an increase in specific root length and the number of specific root nodules when compared to the control group [83]. Furthermore, the discovery of film color revealed a direct correlation with soil temperature, which, in turn, affected plant performance. Specifically, the fresh weight and yield of peanuts were variably influenced by each of the three colors in bulk soil [50]. Bio-mulch films, in two sizes, were tested in sandy soil, with a significant reduction in plant biomass [84]. Ten percent PLA decreased maize biomass and chlorophyll content in leaves [69]. Finally, high doses of PLA produced strong phytotoxicity, and the distribution of arbuscular mycorrhizal fungi (AMF) genera showed significant variations in responses to microplastics (PLA), as well as Cd [69].

Table 3. Effects of biodegradable/bio-based plastics on soil biological properties.

Type of Biodegradable/Bio-Based Plastic	Type of Soil	Effects in Plastics	Effects on Soils	References
PBS-starch, PBS, and PLA.	Agricultural fields in Japan.	The rate of bioplastic degradation was enhanced, accompanied by an increase of bacterial biomass in the soil.	Bacterial diversity in the soil was not affected by the degradation of bioplastics.	[56]
BDM (BioAgri®, Naturecycle, and Organix A.G. Film™) and one experimental film comprised of a blend of polylactic acid (PLA) and polyhydroxyalkanoates (PHA) were tested alongside a polyethylene (PE) mulch (negative control) and cellulose paper mulch (WeedGuard Plus®, positive control).	Sandy loam and silt loam.		Differences in bacterial communities by mulch treatment were not significant for any season in either location, except for Fall 2015 in WA, where differences were observed between BDMs and no-mulch plots. Extracellular enzyme assays were used to characterize communities functionally, revealing significant differences by location and sampling season in both TN and WA but minimal differences between BDM and PE treatments. Overall, BDMs had comparable influences on soil microbial communities to PE mulch films.	[59]
PLA.	Mesocosm experiment: The sandy clay loam topsoil was enriched with the rosy-tipped earthworm, Aporrectodearosea, and was planted with a perennial ryegrass known as Loliumperenne.		Fewer seeds germinated. Shoot height was reduced. The health of the earthworm was affected. Basic properties of the soil were affected.	[78]
PLA.	Haplic Kastanozem.		No significant effect on soil enzyme activities, soil physicochemical properties, root characteristics, plant biomass, or crop yield over one growing season (5 months).	[85]
PLA/PHA blend and paper mulch.	Silt loam (Mount Vernon) and well-drained Shady–Whitwell complex soil (Knoxville).		All mulching treatments were effective in suppressing weeds compared to bare soil, and mulches generally remained intact during the growing season except for the paper mulch in Knoxville, which likely was weakened by high moisture exposure.	[62]
PLA, BioAgri.	Sandy loam and silt loam.		In sandy loam, there were overall positive effects on soil and groundwater quality. In silt loam, reduced burst microbial respiration was observed.	[16]
PBAT.	Loessial soil.		Lower amounts of PBAT relatively increased the diversity of soil bacterial communities, and the relative abundance of the unique Azotobacter increased with increasing PBAT amounts.	[57]
PBAT/PLA.	Farmland (from chili fields and potato fields); no specific type.		The alpha diversities in the PBAT/PLA plastisphere were significantly lower than in the PE plastisphere and soil. PBAT/PLA microplastics act as a filter, enriching taxa with the ability to degrade plastic polymers such as proteobacteria and actinobacteria.	[86]
PBAT and PCL MPs.	Oxisols.		PCL reduced plant production by 73.6–75.2%. PBAT elicited almost negligible changes. Biodegradable MPs tended to reduce bacterial α-diversity. Shoot biomass was reduced by PCL. PBAT promoted root growth	[82]
BPE-AMF-PLA (mulch film) and BPE-RP-PLA (Rigid Packaging).	OECD soil.		PLA-based plastics caused the migration of earthworms to deeper soil layers. Earthworm avoidance behavior due to the presence of plastics in soil was found for the first time.	[79]
Plastic components purportedly transferred into the soil as a result of mulch (bio)degradation in crop fields: adipic acid, succinic acid, and 1,4-Butanediol.	In vitro experiment.		Consequences in lettuce and tomato: There were no significant differences between the two plants. Adipic acid inhibited growth. Succinic acid had no impact. Butanediol enhanced growth to some extent. Roots were more vulnerable than shoots and leaves.	[81]
Paper mulches.	Tomato fields in Spain, Italy, and the USA.		In the Mediterranean continental climate, the vegetative development of tomato processing crops mulched with early-grade black MB films was equivalent to that observed with PE mulches and higher than that with paper mulches.	[87]
BDP (made of Mater-bi, grade EF04P) in the form of pellets).	Loamy (cambisol).		Only the highest dose of BDP (P10000) stimulated growth of the microbial biomass.	[75]
PLA mixed with PBAT.	Sandy soil.		Significantly lower leaf relative chlorophyll content, lower shoot and root biomass, lower leaf area and fruit biomass, and higher specific root length and specific root nodules were observed compared to the control.	[83]
PLA (bio-based, compostable) and PBAT (fossil-based, biodegradable).	Soils were collected from farmlands in China.		Weight loss of the plastics. Drastic increase in soil dissolved organic carbon. Formation of distinct bacterial communities in the plastic surface soil.	[47]
PBAT and PLA in three different colors.	Bulk soil.		Film color was discovered to have a direct impact on soil temperature, consequently influencing the performance of plants. The fresh weight and yield of peanuts were affected differently by each of the three colors.	[50]
PHB/HV (copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate), PCL, PBSA, and PBS.	Farm soil.	(1) PHB/HV underwent a faster degradation at 30 °C than at 52 °C in soil under aerobic conditions. (2) PHB showed the fastest degree of degradation among the four plastics at 30 °C, and PBSA the fastest at 52 °C. (3) Degradation of all the four plastics was observed both at 30 °C and 52 °C under anaerobic conditions for 50 d.	Microorganisms on the degrading plastics appeared to be diverse at 30 °C, including bacteria and fungi.	[88]
Bio mulch films in two sizes (Ma and Mi).	Sandy soil.		Plant biomass was significantly reduced. Bio Ma and Bio Mi had the strongest negative effect.	[84]
PBAT.	Sandy loam and loamy soil.		CO2 emissions (13–57%), microbial biomass (1–7%), and a shift in community composition were induced.	[15]
PBAT with other polymeric compounds: TPS, PLA, PHB, and cereal flour or a mixture of them (available in agriculture).	Agricultural soils.		Germination was reduced (lettuce and tomato). Root development (lettuce) was reduced. Plant aerial growth was limited. Tomato aerial plant parts and root growth were reduced. (In both plant species, inhibitory effects on development were associated with proline increases, a physiological marker for some plant stresses).	[89]
BioAgri (20–25% starch), PLA, and PHA.	Sandy loam.		Increased aggregate stability, reduced soil microbial activity, modified the soil microclimate, and had effects on groundwater quality.	[16]
PLA and PBS.	Loam soil.		The composition of the soil microbial communities was modified. The microbiome in soils amended with PBS and PLA showed greater ability to absorb exogenous carbohydrates and amino acids compared to the control soils. There was a decrease in the capacity for related metabolic function, possibly as a result of catabolite repression.	[90]
PBAT based.	Clay loam.		Six months after planting, BDMs and PE mulch produced a greater vine biomass density and a fruit yield compared to bare soil, but there were no significant differences between mulch treatments. During the subsequent fruit harvests, BDMs and PE mulch performed equally well.	[7]
Comparison of BDMs relative to black PEM.	Different soils.		BDMs reduced soil temperature by 4.5 ± 0.8% (±one standard error) compared to PEM, and temperatures were coolest beneath paper-based BDM. Starch-polyester BDM was less effective than PEM for weed control, but paper-based BDM reduced weed density and biomass by 85.7 ± 9.2%. Paper-based BDMs were particularly useful for controlling Cyperus spp. weeds. Despite differences in soil temperature and weed suppression, crop yields were not different between BDMs and PEM.	[53]
PLA.	Soil from farmland.		(1) Ten percent PLA decreased maize biomass and chlorophyll content in leaves. (2) High doses of PLA produced strong phytotoxicity. (3) The distribution of arbuscular mycorrhizal fungi (AMF) genera showed significant variations in responses to microplastics (PLA and PE) and Cd.	[69]
Bio-PMF.	Field continuously cropped with peanuts (not specific type).		(1) CPMF stably enhanced peanut yield by improving soil–peanut ecology but introduced many MPs, DMP, DEP, and DBP into the soil and endangered the soil environment. (2) Without introducing plastic pollutants, Bio-PMF slightly increased peanut yield by partially altering soil–peanut ecology.	[70]
PBAT/PLA.	Black soil, red earths, and desert soil.		The bacterial communities and metabolites of all three soils were negatively affected.	[76]
PBSA film.	Loam, clay loam, and sandy loam textures from alluvial and volcanic ash cultivated fields.	Relative fast degradation.	The findings indicate that as the distribution ratio of native PBSA–degrading fungi in the soil increases, the degradation of the film becomes faster.	[77]
PBAT.	Sandy loam.		Negative effects on rice plant growth, oxidative stress, and gene expressions related to different pathways were observed.	[91]
BP (biodegradable paper made from plant straw) and BB (bio-based film made from plant straw combined with decomposed coal).	Surface soil of the greenhouse with pH = 8.43.		(1) BB mulching reduced root growth (root diameter, biomass, and the root/shoot ratio). (2) Fruit quality was partly improved by BP mulching due to reduced nitrate but increased vitamin C.	[66]
PLA/PBAT mulch.	Samples from the depth of 20 cm.	The degradation abilities of PLA/PBAT mulch in various soils vary depending on the microorganisms present.		[54]
PEF.	Rhizosphere soil (of lettuce [Lactuca sativa L.]) and bulk soil.		(1) Inhibited the growth of lettuce and the photosynthesis and the accumulation of other nutrients (e.g., soluble sugar and nitrate nitrogen). (2) Influenced soil enzyme activities and bacterial community.	[14]
PHBV.	Ap horizon (0–20 cm) of an experimental field pH = 6.8.		(1) Increased specific microbial growth rate and a more active microbial biomass. (2) The PHBV changed the soil bacterial community at different taxonomical levels.	[72]
Bio-MPs.	Not specific.	Nanoplastics are easy to create.	(1) Act as labile C sources to stimulate microbial growth. (2) Are highly toxic to plants due to the nanoplastics.	[67]
Comparison of BDMs relative to black PEM.	Different soils.		(1) Starch-polyester BDM was less effective than PEM for weed control, but paper-based BDM reduced weed density and biomass by 85.7 ± 9.2%. (2) Paper-based BDMs were particularly useful for controlling Cyperus spp. weeds.	[53]

Table 3. Effects of biodegradable/bio-based plastics on soil biological properties.

Type of Biodegradable/Bio-Based Plastic	Type of Soil	Effects in Plastics	Effects on Soils	References
PBS-starch, PBS, and PLA.	Agricultural fields in Japan.	The rate of bioplastic degradation was enhanced, accompanied by an increase of bacterial biomass in the soil.	Bacterial diversity in the soil was not affected by the degradation of bioplastics.	[56]
BDM (BioAgri®, Naturecycle, and Organix A.G. Film™) and one experimental film comprised of a blend of polylactic acid (PLA) and polyhydroxyalkanoates (PHA) were tested alongside a polyethylene (PE) mulch (negative control) and cellulose paper mulch (WeedGuard Plus®, positive control).	Sandy loam and silt loam.		Differences in bacterial communities by mulch treatment were not significant for any season in either location, except for Fall 2015 in WA, where differences were observed between BDMs and no-mulch plots. Extracellular enzyme assays were used to characterize communities functionally, revealing significant differences by location and sampling season in both TN and WA but minimal differences between BDM and PE treatments. Overall, BDMs had comparable influences on soil microbial communities to PE mulch films.	[59]
PLA.	Mesocosm experiment: The sandy clay loam topsoil was enriched with the rosy-tipped earthworm, Aporrectodearosea, and was planted with a perennial ryegrass known as Loliumperenne.		Fewer seeds germinated. Shoot height was reduced. The health of the earthworm was affected. Basic properties of the soil were affected.	[78]
PLA.	Haplic Kastanozem.		No significant effect on soil enzyme activities, soil physicochemical properties, root characteristics, plant biomass, or crop yield over one growing season (5 months).	[85]
PLA/PHA blend and paper mulch.	Silt loam (Mount Vernon) and well-drained Shady–Whitwell complex soil (Knoxville).		All mulching treatments were effective in suppressing weeds compared to bare soil, and mulches generally remained intact during the growing season except for the paper mulch in Knoxville, which likely was weakened by high moisture exposure.	[62]
PLA, BioAgri.	Sandy loam and silt loam.		In sandy loam, there were overall positive effects on soil and groundwater quality. In silt loam, reduced burst microbial respiration was observed.	[16]
PBAT.	Loessial soil.		Lower amounts of PBAT relatively increased the diversity of soil bacterial communities, and the relative abundance of the unique Azotobacter increased with increasing PBAT amounts.	[57]
PBAT/PLA.	Farmland (from chili fields and potato fields); no specific type.		The alpha diversities in the PBAT/PLA plastisphere were significantly lower than in the PE plastisphere and soil. PBAT/PLA microplastics act as a filter, enriching taxa with the ability to degrade plastic polymers such as proteobacteria and actinobacteria.	[86]
PBAT and PCL MPs.	Oxisols.		PCL reduced plant production by 73.6–75.2%. PBAT elicited almost negligible changes. Biodegradable MPs tended to reduce bacterial α-diversity. Shoot biomass was reduced by PCL. PBAT promoted root growth	[82]
BPE-AMF-PLA (mulch film) and BPE-RP-PLA (Rigid Packaging).	OECD soil.		PLA-based plastics caused the migration of earthworms to deeper soil layers. Earthworm avoidance behavior due to the presence of plastics in soil was found for the first time.	[79]
Plastic components purportedly transferred into the soil as a result of mulch (bio)degradation in crop fields: adipic acid, succinic acid, and 1,4-Butanediol.	In vitro experiment.		Consequences in lettuce and tomato: There were no significant differences between the two plants. Adipic acid inhibited growth. Succinic acid had no impact. Butanediol enhanced growth to some extent. Roots were more vulnerable than shoots and leaves.	[81]
Paper mulches.	Tomato fields in Spain, Italy, and the USA.		In the Mediterranean continental climate, the vegetative development of tomato processing crops mulched with early-grade black MB films was equivalent to that observed with PE mulches and higher than that with paper mulches.	[87]
BDP (made of Mater-bi, grade EF04P) in the form of pellets).	Loamy (cambisol).		Only the highest dose of BDP (P10000) stimulated growth of the microbial biomass.	[75]
PLA mixed with PBAT.	Sandy soil.		Significantly lower leaf relative chlorophyll content, lower shoot and root biomass, lower leaf area and fruit biomass, and higher specific root length and specific root nodules were observed compared to the control.	[83]
PLA (bio-based, compostable) and PBAT (fossil-based, biodegradable).	Soils were collected from farmlands in China.		Weight loss of the plastics. Drastic increase in soil dissolved organic carbon. Formation of distinct bacterial communities in the plastic surface soil.	[47]
PBAT and PLA in three different colors.	Bulk soil.		Film color was discovered to have a direct impact on soil temperature, consequently influencing the performance of plants. The fresh weight and yield of peanuts were affected differently by each of the three colors.	[50]
PHB/HV (copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate), PCL, PBSA, and PBS.	Farm soil.	(1) PHB/HV underwent a faster degradation at 30 °C than at 52 °C in soil under aerobic conditions. (2) PHB showed the fastest degree of degradation among the four plastics at 30 °C, and PBSA the fastest at 52 °C. (3) Degradation of all the four plastics was observed both at 30 °C and 52 °C under anaerobic conditions for 50 d.	Microorganisms on the degrading plastics appeared to be diverse at 30 °C, including bacteria and fungi.	[88]
Bio mulch films in two sizes (Ma and Mi).	Sandy soil.		Plant biomass was significantly reduced. Bio Ma and Bio Mi had the strongest negative effect.	[84]
PBAT.	Sandy loam and loamy soil.		CO2 emissions (13–57%), microbial biomass (1–7%), and a shift in community composition were induced.	[15]
PBAT with other polymeric compounds: TPS, PLA, PHB, and cereal flour or a mixture of them (available in agriculture).	Agricultural soils.		Germination was reduced (lettuce and tomato). Root development (lettuce) was reduced. Plant aerial growth was limited. Tomato aerial plant parts and root growth were reduced. (In both plant species, inhibitory effects on development were associated with proline increases, a physiological marker for some plant stresses).	[89]
BioAgri (20–25% starch), PLA, and PHA.	Sandy loam.		Increased aggregate stability, reduced soil microbial activity, modified the soil microclimate, and had effects on groundwater quality.	[16]
PLA and PBS.	Loam soil.		The composition of the soil microbial communities was modified. The microbiome in soils amended with PBS and PLA showed greater ability to absorb exogenous carbohydrates and amino acids compared to the control soils. There was a decrease in the capacity for related metabolic function, possibly as a result of catabolite repression.	[90]
PBAT based.	Clay loam.		Six months after planting, BDMs and PE mulch produced a greater vine biomass density and a fruit yield compared to bare soil, but there were no significant differences between mulch treatments. During the subsequent fruit harvests, BDMs and PE mulch performed equally well.	[7]
Comparison of BDMs relative to black PEM.	Different soils.		BDMs reduced soil temperature by 4.5 ± 0.8% (±one standard error) compared to PEM, and temperatures were coolest beneath paper-based BDM. Starch-polyester BDM was less effective than PEM for weed control, but paper-based BDM reduced weed density and biomass by 85.7 ± 9.2%. Paper-based BDMs were particularly useful for controlling Cyperus spp. weeds. Despite differences in soil temperature and weed suppression, crop yields were not different between BDMs and PEM.	[53]
PLA.	Soil from farmland.		(1) Ten percent PLA decreased maize biomass and chlorophyll content in leaves. (2) High doses of PLA produced strong phytotoxicity. (3) The distribution of arbuscular mycorrhizal fungi (AMF) genera showed significant variations in responses to microplastics (PLA and PE) and Cd.	[69]
Bio-PMF.	Field continuously cropped with peanuts (not specific type).		(1) CPMF stably enhanced peanut yield by improving soil–peanut ecology but introduced many MPs, DMP, DEP, and DBP into the soil and endangered the soil environment. (2) Without introducing plastic pollutants, Bio-PMF slightly increased peanut yield by partially altering soil–peanut ecology.	[70]
PBAT/PLA.	Black soil, red earths, and desert soil.		The bacterial communities and metabolites of all three soils were negatively affected.	[76]
PBSA film.	Loam, clay loam, and sandy loam textures from alluvial and volcanic ash cultivated fields.	Relative fast degradation.	The findings indicate that as the distribution ratio of native PBSA–degrading fungi in the soil increases, the degradation of the film becomes faster.	[77]
PBAT.	Sandy loam.		Negative effects on rice plant growth, oxidative stress, and gene expressions related to different pathways were observed.	[91]
BP (biodegradable paper made from plant straw) and BB (bio-based film made from plant straw combined with decomposed coal).	Surface soil of the greenhouse with pH = 8.43.		(1) BB mulching reduced root growth (root diameter, biomass, and the root/shoot ratio). (2) Fruit quality was partly improved by BP mulching due to reduced nitrate but increased vitamin C.	[66]
PLA/PBAT mulch.	Samples from the depth of 20 cm.	The degradation abilities of PLA/PBAT mulch in various soils vary depending on the microorganisms present.		[54]
PEF.	Rhizosphere soil (of lettuce [Lactuca sativa L.]) and bulk soil.		(1) Inhibited the growth of lettuce and the photosynthesis and the accumulation of other nutrients (e.g., soluble sugar and nitrate nitrogen). (2) Influenced soil enzyme activities and bacterial community.	[14]
PHBV.	Ap horizon (0–20 cm) of an experimental field pH = 6.8.		(1) Increased specific microbial growth rate and a more active microbial biomass. (2) The PHBV changed the soil bacterial community at different taxonomical levels.	[72]
Bio-MPs.	Not specific.	Nanoplastics are easy to create.	(1) Act as labile C sources to stimulate microbial growth. (2) Are highly toxic to plants due to the nanoplastics.	[67]
Comparison of BDMs relative to black PEM.	Different soils.		(1) Starch-polyester BDM was less effective than PEM for weed control, but paper-based BDM reduced weed density and biomass by 85.7 ± 9.2%. (2) Paper-based BDMs were particularly useful for controlling Cyperus spp. weeds.	[53]

5. Greenhouse Gasses by Biodegradable Plastics in Soils

The swift expansion of BPs and their role as alternatives to non-degradable plastics may result in the accumulation of biodegradable microplastics (BMPs) within soil ecosystems, alterations in soil biogeochemical cycles, and subsequent climate changes [45]. Agriculture serves as the primary contributor to greenhouse gas emissions, with CH₄ and N₂O emissions from agricultural lands representing over 37.8% and 65.1% of global anthropogenic emissions, respectively [18].

The application of film mulching enhances the hydrothermal conditions of the soil, which, in turn, facilitates the production of CH₄ and N₂O during the processes of soil organic carbon decomposition, fermentation, nitrification, and denitrification (Figure 2). This phenomenon ultimately plays a role in contributing to global warming [18,92]. Findings from incubation and pot experiments demonstrate significant effects of BPs on the chemical and biological characteristics of soil, which vary according to the type of plastic used and the duration and timing of the study. These effects encompassed the production of greenhouse gases, alterations in associated microbial communities, and variations in plant growth, including transient phenomena such as an initial decrease in soil pH, N₂O emissions, and growth suppression in plants [93].

Microorganisms play a crucial role in the breakdown of plastics and the decomposition of organic matter in soil. Consequently, alterations in microbial communities, biomass, and their activity may ultimately influence CO₂ emissions from the soil [15]. Rillig et al. [94] documented a notable rise in CO₂ emissions ranging from 5 to 26% due to the addition of MPs.

Based on Figure 2, the process of decomposition plays a vital role in assessing the fate of BPs within agricultural soils. It is important to note that BPs cannot typically undergo complete degradation to their final products, carbon dioxide (CO₂) and water (H₂O), in a single step. The decomposition of BDPs generally involves two main stages: fragmentation and biodegradation. Initially, BDP films and other products are fragmented through various natural forces, including solar radiation, water erosion, wind, the activity of earthworms, crop growth, and bioturbation, resulting in smaller plastic fragments. Subsequently, these plastic residues are further broken down into their end products by soil microorganisms [95]. Specifically, the biodegradable plastic PBAT has been demonstrated to enhance the activity of soil microorganisms and elevate CO₂ emissions, likely due to its direct degradation. This finding is further corroborated by a significant rise in the relative abundance of bacterial lineages known to degrade polyesters and other biodegradable MPs. The impact of MPs was found to intensify as the size of the plastic particles decreased and their concentration increased. Consequently, this may lead to heightened CO₂ emissions from soils contaminated with biodegradable MPs, influenced by the soil’s texture [15]. For example, the incorporation of 10% poly(3-hydroxybutyrate co-3-hydroxyvalerate) (PHBV), recognized for its biodegradable properties, resulted in heightened CO₂ emissions from the soil, primarily due to the degradation of the material [72].

Analytically, it is posited that MPs influence soil CO₂ emissions primarily through their effects on the physical properties of soil, as noted by Rillig et al. [94]. This includes factors such as aggregate stability and porosity, which may lead to specific outcomes depending on the type of soil (Figure 3). For example, the capacity of soils to develop aggregates is significantly influenced by their texture; specifically, soils with a higher sand content tend to exhibit reduced aggregation, as indicated by Totsche et al. [96] and Simon et al. [97]. Furthermore, sandy soils typically possess good aeration, suggesting that any enhancement in porosity resulting from the addition of MPs may not significantly impact CO₂ emissions compared to soils with poor aeration. However, the specific effects of MPs on different soil types have been infrequently addressed in existing research [18].

Based on another recent study [18], dryland soils typically function as storage sites for atmospheric CH₄ while also acting as sources of N₂O. The application of biodegradable plastic film mulching (BM) led to a notably higher seasonal cumulative emission of CH₄, exceeding that of traditional plastic film mulching (PM) by 20.5%. The implementation of film mulching treatments resulted in a significant increase in N2O emissions, with BM demonstrating a markedly lower seasonal cumulative N₂O emission rate of 23.53% in comparison to PM [18].

The global adoption of bio-based plastics is on the rise, particularly due to their growing applications in the agriculture and food packaging sectors [68]. They have emerged as alternative materials aimed at addressing the energy crisis associated with plastic production; however, their effects on soil ecosystems, including plants and microorganisms, are still largely uncharted [14]. A recent life cycle assessment of bio-based polymers reveals that although composting offers certain advantages over landfilling, it also presents drawbacks when compared to recycling, such as an increase in CH₄ production contributing to global warming [27].

It can be concluded that the significant presence of bio-based and biodegradable PBSA plastics may have adverse effects on the soil microbiome [21]. PLA should be regarded as a bio-based and compostable plastic, as its degradation necessitates elevated temperatures during the composting process, attributed to its high glass transition temperature of 60 °C. The presence of microbes also plays a significant role in expediting the degradation of PLA [21]. In contrast, PBS, PBSA, PHA, and PBAT can decompose in soil at ambient or lower temperatures [98].

Furthermore, PET is commonly acknowledged as one of the leading fossil-based plastics used in the manufacturing of drinking water bottles and food packaging, accounting for around 20% of the total global plastic production [99,100]. PEF, while having a comparable chemical composition to PET, demonstrates improved gas and water barrier characteristics, along with better thermal performance than PET [101,102]. A study shows that PEF can significantly lower the use of non-renewable resources and cut greenhouse gas emissions by approximately 40% to 50% and 45% to 55%, respectively [103]. As a result, the environmental consequences and ecological hazards linked to bio-based PEF are receiving heightened scrutiny [14].

There is still a lack of research on bio-based MPs [14]. An investigation into the biological impacts of PEF and PET MPs on lettuce seedlings demonstrated that both types of MPs negatively affected seedling growth, reduced photosynthetic activity, and impaired the absorption of vital nutrients, including soluble sugars and nitrate nitrogen. Both categories of MPs also influenced soil enzyme activities and altered the composition of the bacterial community [14]. In addition, bio-based PEF MPs demonstrated a milder effect on chlorophyll accumulation and the diversity of the rhizosphere soil bacterial community compared to fossil-derived PET MPs [14]. Furthermore, bio-based PEF MPs demonstrated more advantageous interactions with both vegetation and soil in comparison to fossil-derived PET MPs [14].

Moreover, bio-based MPs could exhibit higher levels of ecotoxicity than their fossil-based counterparts. This conclusion is supported by studies that analyze the effects of bio-based plastics, including polylactic acid (PLA) and polyhydroxybutyrate (PHB), in relation to fossil-based plastics such as polypropylene [14]. Reports suggest that PLA MPs demonstrate low-dose stimulation and high-dose inhibitory effects on plant growth [104].

This variation can be ascribed to the intricate factors that affect the biological impacts of MPs. These factors encompass their characteristics, including type, size, degradability, molecular weight, and surface features, as well as the conditions of exposure and the particular plant species in question. Importantly, differences in the surface roughness of MPs can result in varying effects on the cell membrane permeability of duckweed [105].

6. Conclusions

In the present research, data were collected and processed from articles published in the last decade regarding biodegradable and bio-based plastics in microplastic form present in soil systems. Their presence beyond the obvious consequences, i.e., as pollutants in the environment, causes a series of reactions resulting in changes to the physical, chemical, and microbiological properties of soils. In addition, alterations in the Earth’s climate trigger additional variations or dramatically amplify existing ones, so that plastics have a greater impact and are more affected. Depending on their chemical composition, due to increasing temperature and soil moisture, they degrade, releasing significant amounts of gases, as well as other compounds, and possibly contributing to climate change, participating in a perpetual two-way interaction. Changes in soil properties are exacerbated by the climate crisis, and this causes further degradation of existing plastics and so on. In order to make a worthwhile effort toward properly managing plastics in soil ecosystems, it is necessary to maintain a continuous survey and inventory of biodegradable plastics and weather conditions in each study area to achieve the desired results in each case. Future research on different soil types, or in different soil and climatic environments, and focused studies on all kinds of biodegradable plastics are necessary in order to obtain valuable results for both soil health and safe products.