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Article

Effective Bio-Waste Recycling: Minimizing the Risk of Heavy Metal Emission

by
Jakub Kostecki
1,*,
Wojciech Dronia
2,
Jacek Połomka
2 and
Andrzej Jędrczak
1
1
Institute of Environmental Engineering, University of Zielona Gora, 65-516 Zielona Góra, Poland
2
Łużyckie Centrum Recyklingu, Municipal Waste Treatment Plant in Marszów, 68-200 Żary, Poland
*
Author to whom correspondence should be addressed.
Sustainability 2026, 18(7), 3531; https://doi.org/10.3390/su18073531
Submission received: 5 February 2026 / Revised: 28 March 2026 / Accepted: 2 April 2026 / Published: 3 April 2026
(This article belongs to the Special Issue Sustainable Waste Management and Recovery)
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Abstract

The concepts of circular economy increase the need to recycle bio-waste. Effective implementation requires knowledge about associated risks and environmental concerns. This study examines the composition and heavy metal content of bio-waste from municipal waste in western Poland, considering waste type, location, and season. Food waste constituted 36.7% to 47.6% of the total bio-waste, while garden waste accounted for 35.8% to 52.8%, with a strong seasonal dependency. Impurities such as plastics and glass were significant issues for urban and multi-family houses (16.6%), whereas rural and single-family home bio-waste had much lower impurity levels (10.0%). Heavy metals were identified in bio-waste, with the highest concentrations found in inedible food and garden waste. The ecological risk and cumulative effects of heavy metals were assessed using the contamination factor (CF), pollution index (PI), Nemerow Pollution Index (NPI), potential ecological risk index (Ef), and potential toxicity response index (RI). Urban bio-waste exhibited slightly higher levels of heavy metals and impurities compared to rural bio-waste. Zinc was the most abundant heavy metal, while cadmium had the lowest concentration. A seasonal pattern was observed, with winter bio-waste showing the lowest heavy metal concentrations. The results indicate that, despite localized elevated ecological risks, bio-waste recycling can be considered a conditionally safe waste management strategy, although localized and fraction-specific ecological risks, particularly related to cadmium and chromium, were identified.

1. Introduction

The European Union generates more than 233 million tonnes of municipal solid waste (MSW) on an annual basis, with bio-waste representing approximately 30% of this total [1]. The objective of the circular economy is to reduce waste, enhance resource efficiency, promote sustainable production, and extend product lifespans. The transition to a circular economy will be systemic, comprehensive, and transformational, both within the EU and beyond [2,3,4]. According to the European Commission, bio-waste is defined as biodegradable garden and park waste, food and kitchen waste from households, restaurants, caterers and retail premises, as well as comparable waste from food processing plants [2,3]. All these components are present in the bio-waste that is part of the municipal waste stream, but the composition and level of contamination vary.
The prevailing policy stance is to mandate the avoidance of bio-waste generation. In instances where prevention is not feasible, bio-waste must be collected separately and recycled through composting or digestion. The extent of household participation in separate bio-waste collection varies considerably across EU countries, with rates ranging from approximately 5% in Cyprus to over 80% in Austria and Slovenia [1]. In Poland, the proportion of households participating in separate bio-waste collection increased from 24% in 2017 to approximately 40% in 2021 [5,6].
The organization of separate bio-waste collection systems may vary depending on the type of settlement and housing structure. In single-family housing areas, bio-waste is typically collected in bags or small containers through door-to-door systems, whereas in multi-family housing it is often collected in large shared containers. These differences may significantly influence both the composition and contamination level of collected bio-waste, as well as its suitability for further biological treatment.
The recycling of bio-waste offers a multitude of benefits to the environment, the economy and society at large. The utilization of composts and digestates has the potential to enhance soil quality, thereby reducing reliance on artificial fertilizers and pesticides. Furthermore, bio-waste digestion results in the production of biogas, a renewable energy source [7,8,9,10,11,12]. However, the recycling of bio-waste presents a number of challenges, particularly in relation to the organization of efficient collection and transportation, as well as the addressing of treatment conditions that often give rise to social conflict. It is imperative to enhance public awareness of bio-waste recycling [13,14,15]. A further challenge is the presence of impurities (e.g., glass, stones) and contaminants (e.g., heavy metals) in bio-waste.
Heavy metals, defined as chemical elements with a density greater than 4.5 kg/m3, have the potential to cause harm to soil organisms and animals, including humans. While some heavy metals, such as copper (Cu) and zinc (Zn), are essential for growth, others, including lead (Pb), cadmium (Cd), and mercury (Hg), are toxic [16,17,18]. The accumulation of these metals in living organisms has been linked to the development of diseases, including cancer and neurological disorders.
The presence of heavy metals in composts derived from bio-waste may lead to contamination of soil and water with heavy metals [19,20]. In contrast to organic matter, heavy metals present in bio-waste are not biodegradable, which can result in increased concentrations during the composting process. Should the concentration of heavy metals in compost exceed that of the soil, there is a risk of accumulation in the soil and subsequent contamination of groundwater [21,22,23]. Significant quantities of heavy metals are present in food waste, the largest component of household bio-waste, with origins in fertilizers, pesticides, and packaging [24,25,26]. Furthermore, plant waste from gardens, parks, and green spaces can also contain heavy metals originating from soil, water, and applied chemicals [27,28].
A number of authors have highlighted the potential risks associated with the presence of heavy metals in the substrate, both during composting and digestion processes [13,23,29,30]. The presence of heavy metals in bio-waste can impede the activity of microorganisms during biological treatment processes, resulting in disruption and reduced process efficiency. Material exceeding heavy metal limits cannot be legally classified as compost under current regulations [3].
There is increasing awareness of bio-waste recycling and its potential benefits within a circular economy framework. However, significant knowledge gaps still remain. For instance, there is a paucity of detailed local data on the heavy metal content of separated bio-waste, particularly in different areas (e.g., towns and cities) and different types of houses (e.g., houses with one family or many families). Previous studies often present heavy metal content for the entire waste stream without considering the impact of other factors.
This study directly addresses these gaps by providing a comprehensive and integrated assessment of separately collected household bio-waste, combining year-long monitoring of morphological composition with seasonal analysis of heavy metal content. The study simultaneously considers spatial factors (urban vs. rural areas, single- vs. multi-family housing), temporal variability, and waste composition, allowing for a more detailed understanding of the sources and dynamics of heavy metal contamination in bio-waste. Only a limited number of studies present results obtained under real operational conditions at this scope.
The main objective of this study is to assess the morphological composition of bio-waste selectively collected from households and its heavy metal content in relation to seasonal variability and spatial factors. In particular, the study addresses the following research questions:
(i)
How does the morphological composition of bio-waste vary across seasons and housing types?
(ii)
What are the patterns of heavy metal occurrence in different bio-waste fractions?
(iii)
To what extent do waste composition, seasonality, and place of generation influence heavy metal content?
(iv)
What are the implications of these findings for the environmental safety and management of bio-waste recycling systems?
From a sustainability perspective, the quality of bio-waste collected separately is a key factor in the effectiveness of strategies to promote a circular economy. Contaminants and heavy metals have been demonstrated to exert a detrimental effect on the efficiency of biological treatment processes. Moreover, these contaminants have been shown to directly influence the environmental safety and market acceptance of compost and digestate products. It is therefore imperative to ensure that contamination levels remain at a minimum in order to facilitate the effective closure of material loops and to ensure the achievement of long-term environmental benefits. Despite the growing importance of bio-waste recycling, comprehensive assessments linking waste composition, seasonal variability, urban–rural differences, and ecological risk indicators remain limited. The findings of this study are particularly relevant for local authorities and waste management operators in central and eastern Europe. By identifying the specific sources and seasonal fluctuations of heavy metals in different housing types, this research provides a scientific basis for optimizing bio-waste collection routes and pre-treatment processes, thereby ensuring that the resulting compost meets the stringent requirements of the circular economy.

2. Materials and Methods

2.1. Study Area and Sampling Design

Surveys were carried out in Poland, in 4 urban municipalities and 4 rural municipalities, located in the Lubuskie Province, Żary and Żagań County (Figure 1).
Waste was collected from single-family housing both in urban areas (T-SH) and in rural areas (R) using a door-to-door system. Additionally, in urban areas, waste was collected from 1100 dm3 containers serving multi-family housing (T-MH).
Sampling was conducted at weekly intervals over a one-year period (November 2021–October 2022). Metal concentrations were determined in samples collected seasonally, specifically in January, April, June, and September.

2.2. Waste Samples

General waste samples were collected and prepared for laboratory testing in accordance with Szpadt and Jędrczak [31]. The waste was then sorted, as presented in Table 1, into the following three fractions: food waste, garden waste, and impurities. A detailed description of the sampling procedure, laboratory methodology, and waste characteristics is provided in [32].

2.3. Heavy Metal Determination

Heavy metal analyses were conducted for four selected sampling campaigns (January, April, June, and September), representing winter, spring, summer, and autumn conditions, respectively. The selection of these sampling periods was based on the observed seasonal variability in bio-waste composition, particularly the proportion of garden and food waste fractions, which are known to influence heavy metal content. Monthly monitoring of waste composition allowed for the identification of representative time points reflecting distinct seasonal characteristics of the bio-waste stream.
Although intra-seasonal variability may occur, the adopted sampling strategy captures the dominant seasonal patterns resulting from substantial changes in bio-waste composition throughout the year. This approach enabled the capture of major seasonal trends in heavy metal concentrations while ensuring analytical feasibility within a full-scale monitoring framework. Similar strategies, combining high-frequency compositional analysis with seasonal chemical characterization, have been applied in previous studies on municipal bio-waste.
The main aim of the heavy metal analysis in this study was to identify general patterns and potential risk levels rather than short-term fluctuations. Cd, Cr, Cu, Ni, Pb, and Zn were determined by ICP-OES (Optima 8000, PerkinElmer Inc., Waltham, MA, USA). These metals were selected as they are commonly used indicators of contamination in waste and compost quality assessments and are included in relevant regulatory frameworks for organic fertilizers and soil amendments. The presence and concentration of these metals can serve as reliable indicators of pollution levels and the effectiveness of waste treatment processes. We also determined moisture content and loss of ignition in accordance with EN 15934:2012 and EN 15935:2021 [33,34]. Glass, stone and metals were excluded from the analysis.
The bio-waste was dried and ground. A detailed description of the laboratory testing methodology is provided in [32].

2.4. Environmental Risk Assessment

The method proposed by Hakanson [35] was used to determine the environmental risk. The following three parameters were determined: contamination factor (1), pollution index (2), Nemerow Pollution Index (3), potential ecological risk index (4), defined for each heavy metal separately, and potential toxicity response index (5), defined for the heavy metal group.
Contamination factor (pollution index) (1) is used to reflect the pollution of single heavy metal in the sediments; the formula for pollution index of the single heavy metal is
C f i = C m i C n i
We can assess the following four categories of contamination: low contamination—CF < 1, moderate contamination −1 ≤ CF < 3, considerable contamination 3 ≤ CF < 6, and very high contamination—CF ≥ 6 [35].
Pollution index (2) and Nemerow Pollution Index (3) are commonly used to assess the overall pollution levels. Nemerow Pollution Index (NPI) emphasizes the most polluting factors.
P I = C m i C n i = C f i
where PI ≤ 1.0—no pollution, 1.0 < PI ≤ 2.0—slightly pollution, 2.0 < PI ≤ 3.0—lightly pollution, 3.0 < PI ≤ 5.0—moderately pollution, and PI > 5.0—seriously pollution [36].
N P I = P I m a x 2 + P I a v 2 2
NPI below 0.59 means very low contamination, 0.59 ≤ NPI < 0.74—low contamination, 0.74 ≤ NPI < 1.0—moderate contamination, 1.0 ≤ NPI < 3.5—high contamination, and NPI ≥ 3.5—very high contamination [37].
Potential ecological risk index (2) for the single heavy metal pollution is calculated as follows:
E f i = C f i · T f i
Ef below 40 means Low ecological risk level of single-factor pollution, 40 ≤ Ef < 80—Moderate, 80 ≤ Ef < 160—Higher, 160 ≤ Ef < 320—High, and Ef > 320—Serious [35,38].
Potential toxicity response index (3) for various heavy metals was calculated as follows:
R I =   ∑ E f i
RI below 150 means Low General level of potential ecological risk, 150 ≤ RI < 300—Moderate, 300 ≤ RI < 600—Severe, and RI > 600—Serious [35,38].
Where
C f i —contamination factor of heavy metal i;
C m i —measured concentration of heavy metal I;
C n i —background value of metal i. For the purposes of this work, the values applicable to uncontaminated areas around Zielona Góra were adopted [39]: Cd 0.5 mg/kg, Cr 2 mg/kg, Ni 2 mg/kg, Pb 13 mg/kg, Cu 9 mg/kg, Zn 35 mg/kg;
E f i —potential ecological risk index of metal i;
T f i —response coefficient for the toxicity of the single HM. Respectively, the corresponding coefficients based on its toxicity were: Cd = 30, Cu = Pb = Ni = 5, Cr = 2, Zn = 1 [38];
RI—environmental risk potential;
P I m a x 2 —maximum PI value of i metal in all samples;
P I a v 2 —the mean of the PI value.

2.5. Statistical Analysis

Relationships between variables were assessed using Pearson’s correlation coefficients (r), and linear regression analysis was applied to evaluate relationships between total heavy metal content and the share of bio-waste fractions. Statistical significance was evaluated at the following two levels: p < 0.05 (significant) and p < 0.01 (highly significant).
The total number of observations used in the statistical analyses was n = 180. For each location, the number of observations was n = 60. The number of observations for individual waste fractions was as follows: edible waste (EW, n = 72), inedible waste (IW, n = 60), and garden waste (GW, n = 48).
Multivariate analysis was conducted using Principal Component Analysis (PCA). Prior to PCA, all variables were standardized using z-score normalization to ensure comparability between variables with different units and ranges. All statistical analyses were carried out with Statistica 13.3 by TIBCO Software Inc. (San Ramon, CA, USA) [40].

3. Results and Discussion

3.1. Characteristics of Bio-Waste

Figure 2 illustrates the average morphological composition of bio-waste across the four seasons at the three locations surveyed. The proportion of the principal categories of separately collected bio-waste in urban and rural areas exhibited a considerable degree of variation between November 2021 and October 2022. A comparison of these values reveals some noteworthy features of their changes.
The proportion of food waste in bio-waste was highest in winter and lowest in autumn (bio-waste from single-family housing in towns and villages, collected in bags) or summer (bio-waste from multi-family housing in towns collected in large containers). The high level of food waste in winter is attributable to a reduction in garden waste generation. The lowest level of food waste is observed in waste collected in bags in single-family households in cities.
The share of garden waste in the bio-waste collected from single-family households in rural and urban areas increases from winter to autumn. In bio-waste collected from multi-family dwellings, the proportion of garden waste remains relatively constant from spring to autumn and is significantly lower in winter. There is no effect of seasonality on the proportion of contaminants in bio-waste collected in bags. The lowest contaminant content was observed in single-family urban bio-waste collected in bags (annual average 7.2%), while the highest was found in multi-family containerized bio-waste (16.5%). Bio-waste from multi-family dwellings exhibited the least contamination in winter and the most in spring.

3.2. Metal Content Relationships

Figure 3 illustrates the typical seasonal and location-specific fluctuations in heavy metal concentrations. The analysis revealed that bio-waste samples exhibited low levels of heavy metals, suggesting that source segregation systems encourage individuals to sort their waste more precisely [41,42]. The bio-waste sample demonstrated the highest zinc concentrations (mean 51.1 mg/kg dm) and the lowest cadmium concentrations (0.36 mg/kg dm). The bio-waste sample demonstrated a higher concentration of metals in the summer (total metals, mean value 134 mg/kg dm) than in the winter (61.9 mg/kg dm). Significantly higher contents of Pb, Cd and Ni were identified in bio-waste collected in urban areas in bins and containers from multi-family housing in comparison to bio-waste collected in bags from single-family housing in urban and rural areas. Conversely, Cu and Zn were found in the highest amounts in bio-waste from single-family housing in urban areas.
The mean content of heavy metals in edible food waste is low (69.6 mg/kg dm). However, it is significantly higher in other food waste and plant waste (114 and 124 mg/kg dm, respectively), likely due to greater exposure of outdoor plant material to anthropogenic pollution. Furthermore, the heavy metal content of the bio-waste did not exceed the permissible levels of heavy metals in surface soils [43].
Correlations between the total heavy metal content of bio-waste and the share of the main components in its dry weight were assessed to better evaluate the interrelationships and sources of metals. A strong and statistically significant positive relationship was observed between total heavy metal content and the share of garden waste (R2 = 0.6887, p < 0.05), indicating that higher proportions of plant-derived material are associated with increased metal concentrations. In contrast, weak-to-moderate negative relationships were identified for edible food waste (R2 = 0.3545, p < 0.05) and other food waste (R2 = 0.2450, p < 0.05), suggesting that higher proportions of these fractions are generally associated with lower total heavy metal content. The relationship for impurities was weak (R2 = 0.0536) and not statistically significant (p > 0.05), indicating no clear association with total metal concentrations.
These relationships reflect different levels of analysis as follows: while the regression results describe the influence of waste composition on total heavy metal content, the correlation analysis within individual fractions reflects the co-occurrence patterns of metals within specific waste types.
The strongest correlations between individual metals were observed in the inedible waste group (n = 60). Very strong and statistically significant relationships were identified for several metal pairs, including Ni–Cr (r = 0.980, p < 0.01), Ni–Pb (r = 0.910, p < 0.01), and Zn–Pb (r = 0.795, p < 0.01), indicating a strong co-occurrence of these elements within this fraction. In edible waste (n = 72), correlations were generally weaker, although moderate statistically significant relationships were found for Ni–Pb (r = 0.547, p < 0.05) and Zn–Pb (r = 0.454, p < 0.05). For garden waste (n = 48), moderate correlations were observed between selected metals and total heavy metal content, particularly for Ni (r = 0.518, p < 0.05) and Cr (r = 0.519, p < 0.05), while a strong relationship was also found between Zn and Pb (r = 0.733, p < 0.01). In addition, a statistically significant relationship between season and Pb content was observed (p < 0.05), suggesting a seasonal influence on metal distribution in plant-derived fractions. In the impurities group (n = 12), very strong correlations were also observed between selected metals (e.g., Ni–Cd, r = 0.980), although these results should be interpreted with caution due to the limited sample size.
Principal Component Analysis (PCA) revealed a high variability in heavy metal content in bio-waste, reflecting the influence of multiple interacting factors, including waste composition, seasonality, and location (Figure 4). The first two principal components explained a substantial proportion of the total variance (PC1 ≈ 43.9%, PC2 ≈ 27.5%). The first principal component can be interpreted as representing overall heavy metal variability associated with specific metal groups, particularly Cd, Ni, and Pb. In contrast, the second component appears to be associated with variations related to waste composition, especially plant-derived fractions such as garden waste, which are linked to higher concentrations of Cu, Zn, and Cr.
The grouping of Cu, Cr, Zn, and total heavy metals suggests that these elements are influenced by similar environmental and compositional factors. This may indicate their association with plant-based materials exposed to environmental contamination sources, such as soil and atmospheric deposition. In contrast, Cd, Ni, and Pb form a separate group, which may reflect different sources or pathways of contamination, potentially related to specific waste fractions or localized environmental conditions. Overall, the PCA results confirm that heavy metal distribution in bio-waste is not uniform and is controlled by a combination of compositional and environmental factors, rather than a single dominant source.

3.3. Ecological Risk

Analysis of the contamination factor (Cf) revealed significant variability among the investigated heavy metals, with particularly alarming values observed for cadmium (Cd) and chromium (Cr). Unlike other elements (Ni, Cu, Zn and Pb), which generally exhibited low levels of contamination (Cf < 1), Cd and Cr often exceeded thresholds indicative of high (3 ≤ Cf ≤ 6) and very high (Cf > 6) ecological risk (Figure 5). The highest Cf values for cadmium were recorded in autumn in single-family housing areas for inedible waste (Cf = 15.0) and garden waste (Cf = 22.5). Notably, a critical spike in chromium contamination was also observed in autumn in the IW stream (Cf = 69.15). Seasonality played a crucial role, particularly in garden and inedible waste streams. In contrast, nickel, copper, zinc and lead exhibited consistently low contamination factors across all seasons and waste categories, typically remaining below 0.5.
Assessment of the potential ecological risk factor (Ef) revealed significant environmental hazards associated with the presence of heavy metals in the analyzed bio-waste. While metals such as Ni, Cu, Zn, and Pb maintained low risk levels (Ef < 40) across all seasons and locations, cadmium and chromium exhibited alarming values (Figure 6). Cadmium was identified as the primary ecological threat, with Er values often exceeding the threshold for extreme ecological risk (Ef > 320). The most severe contamination was observed in autumn, particularly in multi-family housing areas (T-MH) for inedible waste (IW). High risk levels for cadmium were also consistent in spring and winter across various waste categories, often exceeding 140. Chromium also contributed to the overall risk, particularly in autumn for inedible waste (T-SH). In most other instances, Cr values fluctuated between moderate (40 ≤ Er < 80) and high risk (80 ≤ Er < 160).
The Nemerow Pollution Index (NPI) clearly showed different levels of contamination among waste fractions and settlement types (Table 2). Cadmium and chromium were identified as the main sources of pollution. Cadmium consistently exhibited elevated values, often exceeding the high contamination threshold, particularly in green and mixed waste fractions. This indicates strong enrichment and a likely anthropogenic origin. Chromium also showed substantial variability, reaching very high levels in selected cases. In contrast, zinc, lead and copper remained at negligible levels across all samples, while nickel generally exhibited low contamination levels, with occasional moderate values in selected waste fractions.
The ecological risk index (RI) confirmed significant variability in environmental risk across the analyzed waste streams (Figure 7). While several fractions were classified as low risk (RI < 150), moderate (150–300) and high (300–600) risk levels were frequently observed, particularly in green waste and rural fractions. No cases of very high ecological risk (RI ≥ 600) were identified. Elevated RI values were primarily driven by high cadmium concentrations, with chromium acting as a secondary, albeit locally significant, contributor.

4. Discussion

Sustainable management of municipal bio-waste is crucial for health, environmental reasons, and addressing the challenges of disposing of increasing amounts of bio-waste. Inadequate waste management poses risks to residents, affects the environment, and impacts the economy [44]. Bio-waste collected selectively in Poland has a morphological composition and physicochemical properties comparable to bio-waste from other EU countries [35]. Bio-waste collected in rural and urban areas from single-family housing is suitable for composting and fermentation. However, bio-waste from multi-family housing contains too many contaminants (>10%), making it problematic for producing high-quality compost [45]. The significantly higher impurity levels (up to 17%) observed in multi-family residential areas suggest that the ‘anonymity of waste’ in large containers remains a major barrier to circularity. This indicates that technical improvements in recycling plants must be accompanied by targeted social educational programs and more effective monitoring of waste separation at the source in urban environments.
The varying content of heavy metals in bio-waste has multiple potential origins, including natural sources such as pesticides and fertilizers, and human activities [46,47,48,49]. Understanding the variability of heavy metal content in selectively collected bio-waste is essential due to the diverse sources of bio-waste.
The contaminant content of bio-waste can vary significantly depending on collection patterns. Bio-waste is collected via door-to-door systems or in bulky containers. Garden waste can be collected with kitchen waste or separately. The generation of different types of waste can be seasonal, with more garden waste produced in summer, or regional, varying by industrial, agricultural, or tourist areas [49,50].
Heavy metals significantly impact the effectiveness of biological waste treatment methods, particularly composting and digestion processes. These elements can inhibit microbial activity, resulting in decreased process efficiency and potential system failures [51,52]. Of particular concern is the transfer of heavy metals to end products such as compost or digestate. When heavy metal concentrations exceed regulatory limits, these products become unsuitable for soil enhancement or fertilizer applications, potentially compromising plant growth and creating environmental hazards [53,54]. The observed variability in heavy metal concentrations suggests a close linkage between their occurrence and the composition of bio-waste, particularly the proportion of plant-derived fractions. Nevertheless, it should be emphasized that these relationships are influenced by multiple environmental factors, including soil contamination and atmospheric deposition, which may contribute to the accumulation of metals in plant material. Particular attention should be given to cadmium, which, despite its low concentrations, was identified as the primary contributor to ecological risk due to its high toxicity and frequent occurrence in specific waste fractions.
While bio-waste serves as an effective feedstock for anaerobic digestion and biogas production, the success of circular economy initiatives depends heavily on market acceptance. Low-quality composts and digestion products face limited long-term market viability [10]. Both final products and separately collected bio-waste must meet stringent quality standards. Varying concentrations of heavy metals can compromise microbial activity, reducing the efficiency of composting and digestion processes while increasing operational costs [55,56].
Chemical analysis reveals predominantly low heavy metal concentrations in bio-waste, with notable exceptions in food waste streams. Vegetable waste, particularly peelings, demonstrates elevated metal content compared to whole vegetables, potentially attributable to food quality standards and organic farming regulations [57,58].
Heavy metal concentrations consistently show higher levels in urban bio-waste compared to rural sources. Research by Hanč et al. [41] demonstrates that urban bio-waste composition remains relatively stable across seasons. In contrast, bio-waste from single-family residences exhibits seasonal variations due to garden maintenance activities, with waste component composition directly influencing chemical parameters.
In bio-waste from both urban and rural single-family households, metal concentrations follow a consistent decreasing pattern: Zn > Cu > Cr > Ni > Pb > Cd, aligning with findings by Cavinato [59]. Multi-family household waste presents a slightly different pattern, with nickel concentrations exceeding chromium levels (Zn > Cu > Ni > Cr > Pb > Cd). Multiple studies have documented elevated heavy metal concentrations in food waste [60], though Chu et al. [61] emphasize the uneven distribution of different metal species within waste streams.
Analysis shows notably higher concentrations of zinc, lead, and copper in grass clippings and leaf waste compared to other bio-waste components, likely resulting from air contamination in urban environments caused by industrial activities and road transport (particulate emissions), as well as the presence of impurities (e.g., plastics, glass, and metal fragments) commonly found in selectively collected bio-waste. Research indicates that plants growing in polluted areas, particularly post-industrial zones and along transportation corridors, accumulate higher levels of heavy metals [62]. Whittle and Dyson [27] specifically note that garden waste from urban or roadside locations often contains significant pollutant loads.
The topsoil horizon, characterized by high organic matter content, demonstrates significant capacity for heavy metal sorption [62,63,64,65]. Metal contamination in urban green spaces stems from multiple sources, including low-level emissions [66,67,68] and industrial activities [69,70,71]. Soil physicochemical properties significantly influence metal sorption capacity, directly affecting potential ecological risks [72,73].
Public understanding of waste separation objectives often remains inadequate, resulting in non-compliance and increased bio-waste contamination [74]. The importance of proper waste segregation and collection cannot be overstated [61,75].
Observed contaminant levels in bio-waste vary significantly by housing type and season, ranging from 5.7% in single-family urban developments during spring and winter to 16–17% in multi-family residential areas during summer and autumn. Common contaminants include glass, metals, plastics, textiles, stones, and construction debris. These findings align with research by Lopes et al. [75], who identified plastics as the predominant contaminant; Silvennoinen et al. [76] also reported similar findings. Similar patterns emerge in southern European studies, where household food and garden waste contain 2–18% contaminants by weight, averaging 10.7% inert material [49].
The Enrichment Factor (EF) serves as a key metric for evaluating the intensity of heavy metal accumulation derived from non-natural sources, including urban runoff, traffic-related emissions, and household waste impurities, in land surface and groundwater exposure scenarios [77,78]. Elevated chromium contamination factors may result from its presence in common waste materials including plastics, glass, paper products, textiles, and plant matter [79].
Recent research by Begum et al. [24] confirms that despite detectable levels of select metals in animal-derived waste, these materials pose minimal ecological risk. Multiple studies [80,81] suggest that metals already present in soil matrices pose greater environmental risks due to their enhanced mobility compared to metals in bio-waste.
Although the overall ecological risk associated with heavy metals in bio-waste was generally low to moderate, several waste fractions exhibited elevated risk levels, including moderate to high ecological risk (RI up to ~400). These elevated values were primarily driven by cadmium, with chromium acting as a secondary contributor.
The results of this study demonstrate that the occurrence and distribution of heavy metals in bio-waste are controlled by a complex interplay of compositional, seasonal, and spatial factors. The strong association between plant-derived fractions and elevated metal concentrations highlights the importance of garden waste as a key carrier of metals, although multiple environmental pathways, including soil contamination and atmospheric deposition, contribute to this process. At the same time, the clear differences observed between single- and multi-family housing indicate that collection systems and user behavior play a critical role in determining bio-waste quality.
From a practical perspective, these findings emphasize that effective bio-waste management requires not only technological solutions, but also improved source separation practices, particularly in urban multi-family areas. Although the overall ecological risk associated with heavy metals in bio-waste varies depending on the waste fraction and composition, ranging from low to high, the variability and elevated contamination factors identified for specific elements, such as chromium, highlight the need for continuous monitoring and adaptive management strategies to ensure long-term safety and sustainability of bio-waste recycling systems.

5. Conclusions

Selective bio-waste collection and subsequent processing through composting or digestion represents a significant contribution to circular economy objectives, simultaneously reducing waste generation and promoting sustainable production practices. This approach not only conserves valuable resources but ensures the generation of high-quality recycled bio-waste products.
The results of this study confirm that bio-waste collected from urban areas with multi-family housing and from rural areas contained a higher proportion of food waste (56.0% and 54.9%, respectively) than bio-waste collected from urban areas with single-family housing (43.9%). In urban areas with single-family housing, typically with small gardens, the proportion of garden waste in bio-waste was approximately 46.3%. This figure was 34.2% in rural areas and 27.4% in urban multi-family housing areas.
At the same time, contamination levels remain a major challenge, particularly in urban multi-family housing systems (16.6%), which can substantially reduce the quality of the resulting compost or digestate. The share of contamination in bio-waste collected in bags (rural areas and cities with single-family housing) was 10.9% and 9.8%, respectively.
The analysis of heavy metals revealed clear relationships with both seasonal patterns and waste origin. Metal concentrations were generally lower in winter and higher in summer, reflecting changes in bio-waste composition, particularly the increased contribution of garden waste. Urban bio-waste exhibited higher concentrations of selected metals compared to rural areas. Across most samples, the observed order of metal concentrations was Zn > Cu > Cr > Ni > Pb > Cd, with some variations depending on housing type.
From a practical perspective, the results highlight the importance of adapting bio-waste management systems to seasonal variability and improving source separation, particularly in multi-family housing areas. Limiting the input of contaminated materials into the bio-waste stream, especially those potentially contributing to cadmium and, to a lesser extent, chromium levels, is essential for maintaining high-quality end products.
Although the overall ecological risk associated with bio-waste was generally low to moderate, the results clearly indicate the occurrence of localized and fraction-specific risks, particularly related to cadmium and chromium. Therefore, the environmental safety of bio-waste recycling should be considered conditional upon effective monitoring and proper waste segregation.
This study focuses on western Poland; nevertheless, the results may be applicable to other regions with similar waste management systems and climatic conditions, particularly in central and eastern Europe. These observations suggest that achieving circular economy goals in urban areas requires not only selective collection but also enhanced pre-treatment to remove inorganic impurities, which may act as an additional source of heavy metals, although their role appears less consistent compared to plant-derived and inedible fractions. The results indicate that heavy metal contamination in bio-waste is primarily associated with garden waste and inedible food waste, while the contribution of impurities appears to be secondary and more variable. The observed relationships should be interpreted as indicative of associations rather than direct causal links.
While this study provides a robust reflection of seasonal trends under real operating conditions, it is important to acknowledge that the sampling campaigns may not capture all short-term fluctuations. Furthermore, the implications for composting and anaerobic digestion discussed herein are based on the physicochemical characteristics of raw bio-waste and the existing literature, rather than direct experimental evaluation of treatment performance. Consequently, these results should be viewed as indicative; future research involving controlled processing experiments is recommended to fully confirm the impact of heavy metal concentrations on overall treatment efficiency and final product quality.

Author Contributions

Conceptualization, J.K. and A.J.; methodology, J.K. and A.J.; software, J.K., W.D.; validation, J.K. and A.J.; formal analysis, J.K.; investigation, J.K. and A.J.; resources, W.D. and J.P.; data curation, J.K. and A.J.; writing—original draft preparation, J.K. and A.J.; writing—review and editing, J.K. and A.J.; visualization, J.K. and A.J.; supervision, A.J. and J.P.; project administration, J.K. and A.J. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the authors on request.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. European Environment Agency. Bio-Waste in Europe–Turning Challenges into Opportunities; European Environment Agency Report (2020); EEA: Copenhagen, Denmark, 2020. [Google Scholar] [CrossRef]
  2. The European Parliament; The Council of the European Union. Directive (EU) 2018/851 of the European Parliament and of the Council of 30 May 2018 Amending Directive 2008/98/EC on Waste (Text with EEA Relevance); (OJ EU. L. 150/109 of 14.6.2018); Official Journal of the European Union: Luxembourg, 2018. [Google Scholar]
  3. Act of 14 December 2012 on Waste [Ustawa z dnia 14 grudnia 2012 r. o odpadach]. Journal of Laws 2013, item 21. Available online: https://isap.sejm.gov.pl/isap.nsf/download.xsp/WDU20130000021/U/D20130021Lj.pdf (accessed on 21 March 2026).
  4. Möslinger, M.; Ulpiani, G.; Vetters, N. Circular economy and waste management to empower a climate-neutral urban future. J. Clean. Prod. 2023, 421, 138454. [Google Scholar] [CrossRef]
  5. GUS 2018: Polish Central Statistical Office; Environment. Available online: https://stat.gov.pl/en/topics/environment-energy/environment/environment-2018;1;10.html (accessed on 5 July 2024).
  6. GUS 2022 Polish Central Statistical Office; Environment. Available online: https://stat.gov.pl/en/topics/environment-energy/environment/environment-2022;1;14.html (accessed on 5 July 2024).
  7. Chia, W.Y.; Chew, K.W.; Le, C.F.; Lam, S.S.; Chee, C.S.C.; Ooi, M.S.L.; Show, P.L. Sustainable utilization of bio-waste compost for renewable energy and soil amendments. Environ. Pollut. 2020, 267, 115662. [Google Scholar] [CrossRef] [PubMed]
  8. Oviedo-Ocaña, E.R.; Abendroth, C.; Domínguez, I.C.; Sánchez, A.; Dornack, C. Life cycle assessment of bio-waste and green waste composting systems: A review of applications and implementation challenges. Waste Manag. 2023, 171, 350–364. [Google Scholar] [CrossRef] [PubMed]
  9. Badagliacca, G.; Testa, G.; La Malfa, S.G.; Cafaro, V.; Lo Presti, E.; Monti, M. Organic Fertilizers and Bio-Waste for Sustainable Soil Management to Support Crops and Control Greenhouse Gas Emissions in Mediterranean Agroecosystems: A Review. Horticulturae 2024, 10, 427. [Google Scholar] [CrossRef]
  10. Dronia, W.; Kostecki, J.; Połomka, J.; Jędrczak, A. Bio-Waste from Urban and Rural Areas as a Source of Biogas and Methane—A Case Study from Poland. Energies 2024, 17, 317. [Google Scholar] [CrossRef]
  11. Zhang, Y.; Wang, X.; Zhu, W.; Zhao, Y.; Wang, N.; Gao, M.; Wang, Q. Anaerobic fermentation of organic solid waste: Recent updates in substrates; products, and the process with multiple products co-production. Environ. Res. 2023, 192, 110663. [Google Scholar] [CrossRef]
  12. El Bari, H.; Lahboubi, N.; Habchi, S.; Rachidi, S.; Bayssi, O.; Nabil, N.; Mortezaei, Y.; Villa, R. Biohydrogen production from fermentation of organic waste, storage and applications. Chem. Eng. Sci. Water Res. 2022, 7, 100043. [Google Scholar] [CrossRef]
  13. Chen, X.; Du, Z.; Guo, T.; Wu, J.; Wang, B.; Wei, Z.; Jia, L.; Kang, K. Effects of heavy metals stress on chicken manures composting via the perspective of microbial community feedback. Environ. Pollut. 2022, 288, 118624. [Google Scholar] [CrossRef]
  14. Sasmoko; Zaman, K.; Malik, M.; Awan, U.; Handayani, W.; Jabor, M.K.; Asif, M. Environmental Effects of Bio-Waste Recycling on Industrial Circular Economy and Eco-Sustainability. Recycling 2022, 7, 60. [Google Scholar] [CrossRef]
  15. Skare, M.; Gavurova, B.; Kovac, V. Investigation of selected key indicators of circular economy for implementation processes in sectorial dimensions. J. Innov. Knowl. 2023, 8, 100421. [Google Scholar] [CrossRef]
  16. Ahmad, W.; Alharthy, R.D.; Zubair, M.; Ahmed, M.; Hameed, A.; Rafique, S. Toxic and heavy metals contamination assessment in soil and water to evaluate human health risk. Sci. Rep. 2021, 11, 17006. [Google Scholar] [CrossRef] [PubMed]
  17. Aziz, A.; Azarafza, M.; Akgun, H. The impact of municipal waste disposal of heavy metals on environmental pollution: A case study for Tonekabon, Iran. Adv. Environ. Res. 2020, 9, 175–189. [Google Scholar] [CrossRef]
  18. Nyiramigisha, P.; Sajidan, K. Harmful Impacts of Heavy Metal Contamination in the Soil and Crops Grown Around Dumpsites. Rev. Agric. Sci. 2021, 9, 271–282. [Google Scholar] [CrossRef] [PubMed]
  19. Iravanian, A.; Ravari, S.O. Types of contamination in landfills and effects on the environment: A review study. In IOP Conference Series: Earth and Environmental Science; IOP Publishing Ltd.: Bristol, UK, 2020; Volume 614, p. 012083. [Google Scholar] [CrossRef]
  20. Szymańska-Pulikowska, A. Changes in the content of selected heavy metals in groundwater exposed to the impact of a municipal landfill site. J. Elem. 2012, 4, 689–702. [Google Scholar] [CrossRef]
  21. Rosen, V.; Chen, Y. Effects of compost application on soil vulnerability to heavy metal pollution. Environ. Sci. Pollut. Res. 2018, 25, 35221–35231. [Google Scholar] [CrossRef]
  22. Farrell, M.; Perkins, W.T.; Hobbs, P.J.; Griffith, G.W.; Jones, D.L. Migration of heavy metals in soil as influenced by compost amendments. Environ. Pollut. 2010, 158, 55–64. [Google Scholar] [CrossRef]
  23. ENV.A.2./ETU/2001/0024 Heavy Metals and Organic Compounds from Wastes Used as Organic Fertilisers. Final Report-July 2004. Available online: https://ec.europa.eu/environment/pdf/waste/compost/hm_finalreport.pdf (accessed on 21 March 2026).
  24. Begum, R.; Akter, R.; Dang-Xuan, S.; Islam, S.; Alam Siddiky, N.; Uddin, A.A.; Mahmud, A.; Sarker, S.; Grace, D.; Samad, M.A.; et al. Heavy metal contamination in retailed food in Bangladesh: A dietary public health risk assessment. Front. Sustain. Food Syst. 2023, 7, 1085809. [Google Scholar] [CrossRef]
  25. Sarker, A.; Kim, J.-E.; Islam, A.R.M.T.; Bilal, M.; Rakib, R.J.; Nandi, R.; Rahman, M.M.; Islam, T. Heavy metals contamination and associated health risks in food webs—A review focuses on food safety and environmental sustainability in Bangladesh. Environ. Sci. Pollut. Res. 2022, 29, 3230–3245. [Google Scholar] [CrossRef]
  26. Adil, N.; Ashraf, K.; Munir, M.; Mohiuddin, M.; Abbasi, A.; Riaz, U.; Aslam, A.; Marey, S.A.; Hatamleh, A.A.; Zaman, Q.U. Pesticides; Heavy Metals and Plasticizers: Contamination and Risk Assessment of Drinking-Water Quality. Sustainability 2023, 15, 13263. [Google Scholar] [CrossRef]
  27. Whittle, A.J.; Dyson, A.J. The fate of heavy metals in green waste composting. Environmentalist 2002, 22, 13–21. [Google Scholar] [CrossRef]
  28. Wan, Y.; Liu, J.; Zhuang, Z.; Wang, Q.; Li, H. Heavy Metals in Agricultural Soils: Sources; Influencing Factors; and Remediation Strategies. Toxics 2024, 12, 63. [Google Scholar] [CrossRef] [PubMed]
  29. Chu, X.; Jin, Y.; Chu, Z. Quantitative evaluation of heavy metal pollution hazards in leachate during fermentation before municipal solid waste incineration. J. Clean. Prod. 2021, 280, 130200. [Google Scholar] [CrossRef]
  30. Kupper, T.; Bürge, D.; Bachmann, H.J.; Güsewell, S.; Mayer, J. Heavy metals in source-separated compost and digestates. Waste Manag. 2014, 34, 867–874. [Google Scholar] [CrossRef] [PubMed]
  31. Jędrczak, A.; Szpadt, R. Określenie Metodyki Badań Składu Sitowego, Morfologicznego i Chemicznego Odpadów Komunalnych (Development Methods for Chemical and Morphological Composition of Waste; Opracowanie dla NFOŚ i Ministra Środowiska: Zielona Góra, Poland, 2006. [Google Scholar]
  32. Dronia, W.; Kostecki, J.; Połomka, J.; Jędrczak, A. Composition and selected properties of bio-waste collected in towns from single- and multi-family housing and in rural areas. Waste Manag. 2023, 172, 140–150. [Google Scholar] [CrossRef]
  33. EN 15934:2012; Sludge, Treated Biowaste, Soil and Waste-Calculation of Dry Matter Fraction After Determination of Dry Residue or Water Content. BSI Standards Publication: London, UK, 2012.
  34. EN 15935:2021; Soil, Waste, Treated Biowaste and Sludge-Determination of Loss on Ignition. BSI Standards Publication: London, UK, 2021.
  35. Hakanson, L. An Ecological Risk Index for Aquatic Pollution Control. A Sedimentological Approach. Water Res. 1980, 14, 975–1001. [Google Scholar] [CrossRef]
  36. Fatoba, P.O.; Ogunkunle, C.O.; Folarin, O.O.; Oladele, F.A. Heavy metal pollution and ecological geochemistry of soil impacted by activities of oil industry in the Niger Delta, Nigeria. Environ. Earth Sci. 2016, 75, 297. [Google Scholar] [CrossRef]
  37. Su, K.; Wang, Q.; Li, L.; Cao, R.; Xi, Y.; Li, G. Water quality assessment based on Nemerow pollution index method: A case study of Heilongtan reservoir in central Sichuan province, China. PLoS ONE 2022, 17, e0273305. [Google Scholar] [CrossRef]
  38. Guo, W.; Liu, X.; Liu, Z.; Li, G. Pollution and Potential Ecological Risk Evaluation of Heavy Metals in the Sediments around Dongjiang Harbor, Tianjin. Procedia Environ. Sci. 2010, 2, 1084–1091. [Google Scholar] [CrossRef]
  39. Available online: https://mapgeochem.pgi.gov.pl/atlas-polski/atlas-geochemiczny-polski/atlas-geochemiczny-polski/ (accessed on 21 March 2026).
  40. Statistica, version 13.3; TIBCO Software Inc.: San Ramon, CA, USA, 2017.
  41. Hanc, A.; Novak, P.; Dvorak, M.; Habart, J.; Svehla, P. Composition and parameters of household bio-waste in four seasons. Waste Manag. 2011, 31, 394–400. [Google Scholar] [CrossRef]
  42. IPTS. Study Report on End-of-Waste Criteria for Biodegradable Waste Subjected to Biological Treatment; Draft Final Report; European Commission: Sevilla, Spain, 2013. [Google Scholar]
  43. ISAP. Regulation 2016/1395 of the Polish Ministry of Environment. Rozporządzenie Ministra Środowiska z Dnia 1 Września 2016 r. w Sprawie Sposobu Prowadzenia Oceny Zanieczyszczenia Powierzchni Ziemi; ISAP: Fukuoka, Japan, 2016. (In Polish) [Google Scholar]
  44. Meena, M.D.; Dotaniya, M.; Meena, B.; Rai, P.; Antil, R.; Meena, H.; Meena, L.; Dotaniya, C.; Meena, V.S.; Ghosh, A.; et al. Municipal solid waste: Opportunities, challenges and management policies in India: A review. Waste Manag. 2023, 130, 105082. [Google Scholar] [CrossRef]
  45. Watson, D.; Bauer, B.; Bel, J.-B.; Mehlhart, G. Guidance for Separate Collection of Municipal Waste. 2020. Available online: https://ec.europa.eu/environment/pdf/waste/studies/15.1.%20EC_DGENV_Separate%20Collection_guidance_DEF.pdf (accessed on 21 March 2026).
  46. Veeken, A.; Hamelers, B. Sources of Cd, Cu, Pb and Zn in bio-waste. Sci. Total Environ. 2002, 300, 87–98. [Google Scholar] [CrossRef] [PubMed]
  47. Wan, Y.; Huang, Q.; Wang, Q.; Ma, Y.; Su, D.; Qiao, Y.; Jiang, R.; Li, H. Ecological risk of copper and zinc and their different bioavailability change in soil-rice system as affected by bio-waste application. Ecotoxicol. Environ. Saf. 2020, 192, 110301. [Google Scholar] [CrossRef] [PubMed]
  48. Ishchenko, V. Environment contamination with heavy metals contained in waste. Environ. Probl. 2018, 3, 21–24. [Google Scholar]
  49. Alessi, A.; Lopes, A.D.C.P.; Müller, W.; Gerke, F.; Robra, S.; Bockreis, A. Mechanical separation of impurities in bio-waste: Comparison of four different pre-treatment systems. Waste Manag. 2020, 106, 12–20. [Google Scholar] [CrossRef]
  50. Chazirakis, P.; Giannis, A.; Gidarakos, E. Material flow and environmental performance of the source segregated bio-waste composting system. Waste Manag. 2023, 160, 23–34. [Google Scholar] [CrossRef]
  51. Bożym, M.; Florczak, I.; Zdanowska, P.; Wojdalski, J.; Klimkiewicz, M. An analysis of metal concentrations in food wastes for biogas production. Renew. Energy 2015, 77, 467–472. [Google Scholar] [CrossRef]
  52. Knoop, C.; Dornack, C.; Raab, T. Nutrient and heavy metal accumulation in municipal organic waste from separate collection during anaerobic digestion in a two-stage laboratory biogas plant. Bioresour. Technol. 2017, 239, 437–446. [Google Scholar] [CrossRef]
  53. Smith, S.R. A critical review of the bioavailability and impacts of heavy metals in municipal solid waste composts compared to sewage sludge. Environ. Int. 2009, 35, 142–156. [Google Scholar] [CrossRef]
  54. Amlinger, F.; Boltzmann, L. Bio-waste Compost and Heavy Metals: A Danger for Soil and Environment? In The Science of Composting; de Bertoldi, M., Sequi, P., Lemmes, B., Papi, T., Eds.; Springer: Dordrecht, The Netherlands, 1996; pp. 314–328. [Google Scholar] [CrossRef]
  55. Jank, A.; Müller, W.; Waldhuber, S.; Gerke, F.; Ebner, C.; Bockreis, A. Impurities in pretreated bio-waste for co-digestion: A determination approach. Waste Manag. 2016, 52, 96–103. [Google Scholar] [CrossRef]
  56. Piadeh, F.; Offie, I.; Behzadian, K.; Rizzuto, J.P.; Bywater, A.; Córdoba-Pachón, J.-R.; Walker, M. A critical review for the impact of anaerobic digestion on the sustainable development goals. J. Environ. Manag. 2023, 238, 119458. [Google Scholar] [CrossRef]
  57. Mititelu, M.; Neacșu, S.M.; Busnatu, Ș.S.; Scafa-Udriște, A.; Andronic, O.; Lăcraru, A.-E.; Ioniță-Mîndrican, C.-B.; Lupuliasa, D.; Negrei, C.; Olteanu, G. Assessing Heavy Metal Contamination in Food: Implications for Human Health and Environmental Safety. Toxics 2025, 13, 333. [Google Scholar] [CrossRef]
  58. Munir, N.; Jahangeer, M.; Bouyahya, A.; El Omari, N.; Ghchime, R.; Balahbib, A.; Aboulaghras, S.; Mahmood, Z.; Akram, M.; Ali Shah, S.M.; et al. Heavy Metal Contamination of Natural Foods Is a Serious Health Issue: A Review. Sustainability 2022, 14, 161. [Google Scholar] [CrossRef]
  59. Cavinato, C.; Bolzonella, D.; Pavan, P.; Fatone, F.; Cecchi, F. Mesophilic and thermophilic anaerobic co-digestion of waste activated sludge and source sorted biowaste in pilot- and full-scale reactors. Renew. Energy 2013, 55, 260–265. [Google Scholar] [CrossRef]
  60. Abu Samah, M.A.; Hassan, N.S.; Hussain, M.R.M.; Ibrahim, M.Z.; Jan, N.H.M.; Kamarudin, M.K.A. Determination of Heavy Metals Concentration in Food Waste Compost on Root Uptake of Capsicum annuum L. Int. J. Adv. Sci. Technol. 2020, 29, 1612–1627. [Google Scholar]
  61. Chu, Z.; Fan, X.; Wang, W.; Huang, W. Quantitative evaluation of heavy metals’ pollution hazards and estimation of heavy metals’ environmental costs in leachate during food waste composting. Waste Manag. 2018, 85, 378–385. [Google Scholar] [CrossRef] [PubMed]
  62. Kabata-Pendias, A. Trace Elements in Soils and Plants, 3rd ed.; CRC Press: Boca Raton, FL, USA, 2000. [Google Scholar] [CrossRef]
  63. Khalid, N.; Hussain, M.; Young, H.S.; Boyce, B.; Aqeel, M.; Noman, A. Effects of road proximity on heavy metal concentrations in soils and common roadside plants in Southern California. Environ. Sci. Pollut. Res. 2018, 25, 35257–35265. [Google Scholar] [CrossRef] [PubMed]
  64. Kuklová, M.; Kukla, J.; Hniličková, H.; Hnilička, F.; Pivková, I. Impact of Car Traffic on Metal Accumulation in Soils and Plants Growing Close to a Motorway (Eastern Slovakia). Toxics 2022, 10, 183. [Google Scholar] [CrossRef]
  65. Pal, S.K.; Roy, R. Evaluating heavy metals emission pattern on road influenced by urban road layout. Transp. Res. Interdiscip. Perspect. 2021, 10, 100362. [Google Scholar] [CrossRef]
  66. Guo, Y.; Chen, B.; Li, Y.; Zhou, S.; Zou, X.; Zhang, N.; Zhou, Y.; Chen, H.; Zou, J.; Zeng, X.; et al. The co-benefits of clean air and low-carbon policies on heavy metal emission reductions from coal-fired power plants in China. Resour. Conserv. Recycl. 2022, 181, 106258. [Google Scholar] [CrossRef]
  67. Dore, A.J.; Hallsworth, S.; McDonald, A.G.; Werner, M.; Kryza, M.; Abbot, J.; Nemitz, E.; Dore, C.J.; Malcolm, H.; Vieno, M.; et al. Quantifying missing annual emission sources of heavy metals in the United Kingdom with an atmospheric transport model. Sci. Total Environ. 2014, 479–480, 171–180. [Google Scholar] [CrossRef]
  68. Alias, N.F.; Khan, F.; Sairi, N.A.; Zain, S.M.; Suradi, H.; Ab Rahim, H.; Banerjee, T.; Bari, A.; Othman, M.; Latif, M.T. Characteristics; emission sources; and risk factors of heavy metals in PM2.5 from Southern Malaysia. ACS Earth Space Chem. 2020, 4, 1309–1323. [Google Scholar] [CrossRef]
  69. EMEP/EEA. EMEP/EEA Air Pollutant Emission Inventory Guidebook 2019; European Environment Agency: Copenhagen, Denmark, 2019; Available online: https://www.eea.europa.eu/publications/emep-eea-guidebook-2019 (accessed on 21 March 2026).
  70. Long, Z.; Zhu, H.; Bing, H.; Tian, X.; Wang, Z.; Wang, X.; Wu, Y. Contamination; sources; and health risk of heavy metals in soil and dust from different functional areas in an industrial city of Panzhihua City, Southwest China. J. Hazard. Mater. 2021, 420, 126638. [Google Scholar] [CrossRef] [PubMed]
  71. Wang, Y.; Duan, X.; Wang, L. Spatial distribution and source analysis of heavy metals in soils influenced by industrial enterprise distribution: Case study in Jiangsu Province. Sci. Total Environ. 2020, 710, 134953. [Google Scholar] [CrossRef] [PubMed]
  72. Mavakala, B.K.; Le Faucheur, S.; Mulaji, C.K.; Laffite, A.; Devarajan, N.; Biey, E.M.; Giuliani, G.; Otamonga, J.-P.; Kabatusuila, P.; Mpiana, P.T.; et al. Leachates draining from controlled municipal solid waste landfill: Detailed geochemical characterization and toxicity tests. Waste Manag. 2016, 55, 211–221. [Google Scholar] [CrossRef]
  73. Brás, P.; Maia, S.; Simões, L.M.; Rabaça, T.; Silva, M.E. Selective collection of bio-waste in a non-intensive urban region–Producers’ characterization. Sustain. Chem. Pharm. 2022, 29, 100738. [Google Scholar] [CrossRef]
  74. Seruga, P. The Municipal Solid Waste Management System with Anaerobic Digestion. Energies 2021, 14, 2067. [Google Scholar] [CrossRef]
  75. Lopes, A.C.P.; Senfter, T.; Ebner, C.; Senn, M.; Pillei, M.; Kraxner, M.; Robra, S.; Bockreis, A. Separation of biodegradable material from the low calorific fraction of municipal solid waste. J. Clean. Prod. 2021, 280, 124681. [Google Scholar] [CrossRef]
  76. Silvennoinen, K.; Katajajuuri, J.-M.; Hartikainen, H.; Heikkilä, L.; Reinikainen, A. Food waste volume and composition in Finnish households. Br. Food J. 2014, 118, 2336–2351. [Google Scholar] [CrossRef]
  77. Mavakala, B.K.; Sivalingam, P.; Laffite, A.; Mulaji, C.K.; Giuliani, G.; Mpiana, P.T.; Poté, J. Evaluation of heavy metal content and potential ecological risks in soil samples from wild solid waste dumpsites in developing countries under tropical conditions. Environ. Chall. 2022, 6, 100461. [Google Scholar] [CrossRef]
  78. Attia, O.E.A.; Ghrefat, H. Assessing heavy metal pollution in the recent bottom sediments of Mabahiss Bay, North Hurghada, Red Sea, Egypt. Environ. Monit. Assess. 2013, 185, 9925–9934. [Google Scholar] [CrossRef]
  79. Huerta-Pujol, O.; Soliva, M.; Giró, F.; López, M. Heavy metal content in rubbish bags used for separate collection of bio-waste. Waste Manag. 2010, 30, 728–733. [Google Scholar] [CrossRef]
  80. Wang, N.; Han, J.; Wei, Y.; Li, G.; Sun, Y. Potential Ecological Risk and Health Risk Assessment of Heavy Metals and Metalloid in Soil around Xunyang Mining Areas. Sustainability 2019, 11, 4828. [Google Scholar] [CrossRef]
  81. Jaishankar, M.; Tseten, T.; Anbalagan, N.; Mathew, B.B.; Beeregowda, K.N. Toxicity, mechanism and health effects of some heavy metals. Interdiscip. Toxicol. 2014, 7, 60–72. [Google Scholar] [CrossRef]
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Figure 1. Site location.
Figure 1. Site location.
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Figure 2. Bio-waste composition from tested sites. T-SH—single-family housing in urban areas, T-MH—multi-family housing in urban areas, R—single-family housing in rural areas.
Figure 2. Bio-waste composition from tested sites. T-SH—single-family housing in urban areas, T-MH—multi-family housing in urban areas, R—single-family housing in rural areas.
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Figure 3. Seasonal changes in heavy metal content in bio-waste, (a) Cd; (b) Cr; (c) Cu; (d) Ni; (e) Pb; (f) Zn. T-SH—urban single-family housing; T-MH—urban multi-family housing; R-SH—rural single-family housing. EW—edible food waste; IW—inedible food waste; GW—garden waste week; I—impurities. Values expressed as mg/kg.
Figure 3. Seasonal changes in heavy metal content in bio-waste, (a) Cd; (b) Cr; (c) Cu; (d) Ni; (e) Pb; (f) Zn. T-SH—urban single-family housing; T-MH—urban multi-family housing; R-SH—rural single-family housing. EW—edible food waste; IW—inedible food waste; GW—garden waste week; I—impurities. Values expressed as mg/kg.
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Figure 4. Principal Component Analysis (PCA) component plot in rotated space, * additional variables.
Figure 4. Principal Component Analysis (PCA) component plot in rotated space, * additional variables.
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Figure 5. Contamination factor of bio-waste.
Figure 5. Contamination factor of bio-waste.
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Figure 6. Potential ecological risk index of bio-waste.
Figure 6. Potential ecological risk index of bio-waste.
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Figure 7. Potential toxicity response index of bio-waste.
Figure 7. Potential toxicity response index of bio-waste.
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Table 1. Scope of bio-waste material analysis [32].
Table 1. Scope of bio-waste material analysis [32].
Main CategorySubcategorySample IDTypes of WasteExamples of Waste Materials
Food wasteEdible food waste that can be avoidedEW.1Bread and pastriesBread, tortillas, baked goods, pizza
EW.2Meat and fishPoultry, beef, seafood, eggs
EW.3Dairy productsMilk, yogurt, cheese, ice cream
EW.4Dried foodsRice, pasta, crackers, cereals
EW.5Fruit and vegetablesApples, berries, lettuce, potatoes
EW.6Other leftoversSweets,
Inedible food waste IW.1Meat and fishFish bones, egg shells, mussel shells
IW.2Dairy productsDairy cheese rinds
IW.3Dried foodsNot applicable
IW.4Fruit and vegetablesSeeds, peel, stems
IW.5Other leftoversCoffee dregs, tea bags
Garden wasteGrassGW.1Grass-
LeavesGW.2Leaves-
BranchesGW.3BranchesBrown parts of plants
Other wasteGW.4Other waste-
ImpuritiesPaper and cardboard I.1Packaging Sacks, bags
I.2Other paper and cardboard wastes-
PlasticsI.3Packaging Sacks, bags
I.4Other plastics -
MetalsI.5Ferrous -
I.6Non-ferrous -
OthersI.7Glass-
I.8Textiles-
I.9Multi-material waste -
I.10Mineral waste Debris, stones
I.11Fraction < 1-
Table 2. Nemerow Pollution Index of the analyzed bio-waste.
Table 2. Nemerow Pollution Index of the analyzed bio-waste.
NiCuZnPbCdCr
T-SHEW.Mean0.090.100.000.004.551.44
IW.Mean2.530.150.000.0311.4250.59
GW.Mean0.220.130.000.0217.887.88
I.Mean0.140.100.000.032.218.29
T-MHEW.Mean0.140.110.000.007.032.78
IW.Mean0.130.110.000.0110.892.61
GW.Mean1.820.100.000.0412.5414.10
I.Mean1.800.030.000.0453.763.86
R-SHEW.Mean0.060.070.000.009.8710.45
IW.Mean0.070.120.000.0011.971.70
GW.Mean0.260.100.000.0111.343.59
I.Mean0.510.370.000.036.309.13
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Kostecki, J.; Dronia, W.; Połomka, J.; Jędrczak, A. Effective Bio-Waste Recycling: Minimizing the Risk of Heavy Metal Emission. Sustainability 2026, 18, 3531. https://doi.org/10.3390/su18073531

AMA Style

Kostecki J, Dronia W, Połomka J, Jędrczak A. Effective Bio-Waste Recycling: Minimizing the Risk of Heavy Metal Emission. Sustainability. 2026; 18(7):3531. https://doi.org/10.3390/su18073531

Chicago/Turabian Style

Kostecki, Jakub, Wojciech Dronia, Jacek Połomka, and Andrzej Jędrczak. 2026. "Effective Bio-Waste Recycling: Minimizing the Risk of Heavy Metal Emission" Sustainability 18, no. 7: 3531. https://doi.org/10.3390/su18073531

APA Style

Kostecki, J., Dronia, W., Połomka, J., & Jędrczak, A. (2026). Effective Bio-Waste Recycling: Minimizing the Risk of Heavy Metal Emission. Sustainability, 18(7), 3531. https://doi.org/10.3390/su18073531

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