Metals In Compost Research Articles

Soil Contamination and Human Health: Exploring the Heavy Metal Landscape: A Comprehensive Review

Background: Composting, a cost-effective and efficient method for managing solid waste rich in organic matter, faces challenges when contaminants, particularly heavy metals, are present. These contaminants can significantly impact various environmental aspects and human health. Objective: This study aims to provide a comprehensive review of the effects of heavy metal contamination in compost, focusing on its impact on soil quality, plant growth, aquatic ecosystems, and human health. Methods: An extensive examination of current literature was conducted to analyze the consequences of heavy metal presence in compost. This involved reviewing studies on soil microbial activity, plant health, the accumulation of metals in the food chain, and the resultant effects on animal and human health, as well as on aquatic systems. Results: Elevated levels of heavy metals in compost were found to be toxic to soil microorganisms, vital for numerous soil processes, leading to a reduction in their abundance and functionality. Plants exposed to these metals showed disrupted physiological processes and compromised growth. The absorption of heavy metals by plants leads to their entry into the food chain, posing risks to animal and human health. In aquatic environments, these contaminants contribute to oxidative stress, negatively affecting aquatic life. Conclusion: The presence of heavy metals in compost presents significant environmental and health risks. It is crucial to ensure the absence of such contaminants in compost intended for agricultural use. This study underscores the need for sustainable waste management practices and stringent monitoring of compost quality to safeguard environmental health and human well-being.

Quality assessment of compost from Centralized windrow composter (CWC) and Source segregate automatic vessel composter (AVC) at Hyderabad city in India

Out of the millions of tons of Municipal Solid Waste (MSW) generated annually in India, only about 75-80% of the waste gets collected and out of this, only 22- 28% is processed and treated, and the remaining is deposited indiscriminately at dump yards. Hyderabad city generates around 5500MT of waste every day. And only 20% of the waste is used for composting using the windrow composting process. MSW composting is a rapidly growing method of solid waste management in Hyderabad and In-Vessel composting is the recent initiative by the Govt. of India to reduce the organic solid waste generated at the source. The present study was aimed to assess the degree of accumulation and contamination of the heavy metals in composts from Centralised Windrow Composter (CWC) and Source Segregated Accelerated Vessel Composter (AVC). Compost Samples from CWC and AVC were analysed for metals concentration using Energy Dispersive X-ray Fluorescence Spectrometers (ED-XRF). CWC samples were found with slightly high concentrations of heavy metals like Zinc (0.51 – 0.66%), Copper (0.36 – 0.45%), Nickel 0.03 – 0.05%), Iron (11.46 – 13.27%), and chromium (0.06 – 0.14%) compared to AVC. AVC samples contained high concentrations of Calcium (14.99 – 64.19%), Potassium (9.13 – 29.59%) and Phosphorous (1.55 – 3.43%) when compared to CWC. The current study does a comparative analysis on the process and nutrients available to assess the quality of the compost from both sources. Considering the above findings source segregated AVC seems to be a better composter than centralised CWC, as the concentrations of Ca, K, and P required by the plant were abundant in AVC. Also, considering the process aspect, there is always scope for cross-contamination if the waste is separated after treatment which is the case in CWC.

Effect of inorganic additives (rock phosphate, PR and boron waste, BW) on the passivation of Cu, Zn during pig manure composting

The bioavailability of heavy metals in compost is critical for their agronomic value. The effect of inorganic additives (rock phosphate, PR and boron waste, BW) on Copper (Cu) and Zinc (Zn) bioavailability during co-compost of swine manure and rice straw was assessed using sequential extraction procedure (European Community Bureau of Reference). The result showed that both additives, applied at rates of 2.5%–7.5% (w/w) could promote the change of exchangeable Cu and reducible Cu into oxidizable Cu, thereby reducing their bioavailability factor (BF) by 15.5%–47.2%. While additives provided no significant reduction in BF of Zn, the shift from exchangeable Zn into reducible Zn can still reduce the mobility of Zn. Based on redundancy analysis (RDA), organic matter (OM) and electrical conductivity (EC) were identified as the most important controlling factors for redistribution of Cu and Zn fractions during composting. The inorganic additives strengthened the passivation of Cu and Zn bioavailability by stimulating OM degradation. The 7.5% (w/w) rock phosphate showed best passivating effect on the bioavailability of Cu.

Screening of chemical composition and risk index of different origin composts produced in Lithuania.

The application of composts could be accompanied by potential hazards to soil and humans, caused by heavy metals and organic persistent pollutants. A total of 115 compost samples from four different origins (green waste composts, sewage sludge composts, mixed municipal waste composts after mechanical-biological treatment and mixed municipal waste compost) were collected to analyse the chemical composition, nutrients levels, seven heavy metals, 15 polycyclic aromatic hydrocarbons (PAHs) and seven polychlorobiphenyls (PCBs). Simulation models were used to estimate the heavy metal accumulation risk in soil and to evaluate the potential ecological risk to environment. After analysing chemical parameters of compost quality, it was found that sewage sludge composts contained the highest amounts of nitrogen (2.98%), phosphorus (4.44%) and organic matter (47.6%), and the highest potassium content (1.20%) was found in mixed municipal composts after mechanical-biological treatment. After having tested all the composts, green waste composts had the lowest content of the following nutrients: nitrogen, phosphorus, potassium and sulphur. High molecular weight PAHs dominated in green waste, sewage sludge and mixed municipal waste composts, and the opposite tendency was observed on mixed municipal waste composts after mechanical-biological treatment; low molecular weight PAHs were abundant. It was determined that, according to the total amount of 15 PAHs (16.54mgkg-1 d.w.) and 7 PCBs (233.53μgkg-1 d.w.), the most contaminated composts were produced from mixed municipal waste. As it was expected, the lowest level of PCBs (13.85μgkg-1 d.w.) was found in green waste composts. Monte Carlo simulations showed that the shortest period in which zinc concentration in soil could increase twice is 2years when applying continuously mixed municipal waste compost after mechanical-biological treatment. Based on Monte Carlo simulation results from repeated application of green waste composts, mixed municipal waste compost and mixed municipal waste compost after mechanical-biological treatment could double the soil background level of copper in 6 and 3years respectively. Reducing the content of heavy metals in composts would be of great significance for minimising the damage caused by them.

Evaluation of chemical extractants to assess metals phytoavailability in Brazilian municipal solid waste composts

Municipal solid wastes (MSW) can be composted to become an organic fertilizer. However, besides plant nutrients, it can also contain high concentration of some toxic metals than can pollute agricultural soils, contaminate food, animals and human being. A greenhouse experiment was carried out for two purposes: i) to evaluate the concentrations of cadmium, copper, chromium, nickel, lead and zinc in four Brazilian MSW composts, and, ii) to know which is the best solution for extracting those metals in phytoavailable form from the composts. In order to evaluate the phytoavailability of metals, they were extracted with six chemical extractants: i) water, ii) 0.05 mol L−1 Ca(NO3)2, iii) 0.1 mol L−1 HCl, iv) 0.005 mol L−1 DTPA at pH 7.3, v) 0.05 mol L−1 CaCl2 and vi) Mehlich 3 solution. In addition, lettuces were cultivated as a test plant in pots containing 1.8 kg of MSW compost as substrate. Fifty-six days later, lettuce plants were harvested. New lettuces were then planted for a second cycle, and then harvested after fifty-six days. Semi-total concentration of metals in composts and total in plants was also determined through an extraction with nitric-perchloric acid. Semi–total concentration of Cd and Pb exceeded the intervention limits from Brazil in the four studied composts, and lettuce plants were polluted by those two elements. Therefore, compost made of MSW must be characterized before being used for agricultural soils. Copper and nickel in phytoavailable were effectively extracted with the strongest chelating agents used, HCl and Mehlich 3, probably because most metal is bound to organic matter in the compost. Cadmium, chromium, lead and zinc were no efficiently extracted with any of the tested extractants.

Contrasting effects of composting and pyrolysis on bioavailability and speciation of Cu and Zn in pig manure

The intensive and unregulated application of feed additives to commercial pig foods has resulted in high levels of Cu and Zn in pig manure. The aim of this study was to assess the impacts of composting and pyrolysis processes on the bioavailability and chemical speciation of Cu and Zn in pig manure products by single and sequential extractions, and to compare metal bioavailability in composts and biochar-amended soils in incubation experiments. Composting and pyrolysis processes can convert exchangeable and carbonate-bound Cu and Zn to organic matter and residual fractions, and significantly reduce the potential availability of metals in composts and biochars. The DTPA-Cu and Zn concentrations in soils amended with biochar BC700 were lower than in composts and soils amended with biochar BC400. It is suggested that 700 °C is the preferred pyrolysis temperature for the conversion of pig manure contaminated with heavy metals to biochar, in order to minimize environmental pollution.

The impact of sewage sludge treatment on the content of selected heavy metals and their fractions

The aim of the study was to assess the physicochemical properties of compost made of municipal sewage sludge from selected Municipal Sewage Treatment Plant. Content of basic macroelements and heavy metals (Zn, Cu, Cr, Cd, Ni, Pb, Hg, Mg, Ca, N, P, K, Na) and their fractions was determined by means of BCR method. Based on the analyzes, it was found that the content of heavy metals in compost did not exceed the limits set by natural land management of sewage sludge; the compost is very abundant in biogenic elements - nitrogen and phosphorus – and it can be also considered a significant source of calcium and magnesium. The analysis of results obtained from the three-stage chemical extraction revealed that deposits subjected to aerobic stabilization and composting accumulate metals (in descending sequence) in fractions III and II, i.e. fractions virtually inaccessible to the ecosystem in optimal conditions of use.

Heavy metals in composts of China: historical changes, regional variation, and potential impact on soil quality.

Composts are considered one of major sources that contribute heavy metals to the environment. The objective of this study was to investigate historical changes and spatial variation of metal concentrations in Chinese composts by analysing representative compost samples and published data from 2002 to 2013. Mean concentrations of cadmium (Cd), chromium (Cr), lead (Pb), arsenic (As), mercury (Hg), zinc (Zn), nickel (Ni), and copper (Cu) in the composts were 2.42, 35.52, 32.38, 16.33, 0.32, 258.1, 9.71, and 72.24mgkg-1, respectively. The percentages of samples with metal concentration exceeding critical levels of Chinese standards for organic fertilizers (NY525-2012) were 28.7, 18.3, 9.6, 1.7, and 0.9%, respectively, for Cd, As, Pb, Cr, and Hg. Modelling predicts that it would take 18, 24, 29, and 48years for Cu, Zn, Hg, and Cd to reach Category I Environmental Capacity of China (GB15618-1995) according to current application rate. During the 2002-2013 period, concentration of Cd in composts tended to decrease with time, whereas those of Zn, Cu, and As were opposite, which is likely due to less or no control for these elements. Concentrations of Cu, Zn, As, and Cd were generally higher in composts from the economically developed regions in China, where more commercial farms were built that use metal-spiked feeds. Manures from the commercial farms generally had higher metal concentration, as compared to the subsistence farms. Further research is needed to monitor metal concentrations from source materials to composts and assess long-term impact of compost application on soil quality.

Identification of Heavy Metal in Palm Oil Empty Fruit Bunch Compost, Mulch from Palm oil Waste and Its Effect on Chili (Capsicum annuum L.)

This study aimed to investigate the effect of compost from oil palm empty fruit bunches with different ages, mulching oil palm waste, the levels of heavy metals in compost and its influence on the growth and yield of chili. Composting was assisted by the starter (PromiTM) with a dose of 0.5 kg per ton of chopped bunches. Composting treatment distinguished by the composting time namely 4, 6, 8 and 10 weeks. Mulch treatment consisted of shell, fiber and empty fruit bunch chopped. The empty fruit bunch compost had the potential to decrease the soil acidity because the pH of 7.89- 8.66. The EFBs compost contained Boron of 7.7-10.7 ppm, 12-24.8 ppm of Cuprum, 0.05 to 0.24 % of Fe, 26.5-89.7 ppm of Mn, and 9.1-10.8 ppm of Na. This compost contained heavy metal Cd and Hg. Cd was detected in amount of 0.08 to 0.25 ppm. Hg was detected in amount of 12.9-19.5 ppm. Meanwhile, Pb and As were not found. Cd did not exceed the threshold. On the other hand, Hg was detected exceeding the threshold but did not affect the growth and yield of chili. Organic mulch from palm oil wastes did not significantly affect on the chili yield. Shell mulch had a negative influence on the growth and yield of chili.

Long-term amendment of urban and animal wastes equivalent to more than 100 years of application had minimal effect on plant uptake of potentially toxic elements

Urban waste products such as sewage sludge and organic household waste compost have a potential as fertilizers in agriculture, but evidence from historical field experiments performed in England and Germany with sewage sludge as fertilizer pointed towards negative effects of sludge-derived heavy metal accumulation on soil microbiota and plants. However, sewage sludge has improved in quality during the last half century and source separation of organic household waste has been shown to decrease the concentration of heavy metals in composts made from organic waste. This alongside a growing awareness on the benefits of an increased degree a recycling of nutrients from urban areas to agricultural soils led to the establishment of the CRUCIAL field trial in 2003 where different urban and animal wastes have been applied each year. In the present study we investigated the effect of the different animal and urban waste treatments in CRUCIAL on oat yield after ten years of experimentation on concentrations of heavy metals in oat grain harvested in the field and pea plants grown in a pot trial using soil from the CRUCIAL field trial. We found that all animal and urban waste fertilizers were suitable for fertilization purposes, although some of these will result in unbalanced nutrient inputs if used as single sources. Furthermore, we found that of the elements studied only Zn and Cu were significantly elevated in soil concentration in the urban waste treatments. In oat grain Cd was significantly elevated in a sewage sludge treatment corresponding to more than 200 years’ legal application, but even in this extreme case the concentration of Cd in grain did not exceed the relevant EU limit for Cd content. In pea plants only the concentrations of Zn and Mo were significantly higher in plants grown in soil that had received large amounts of urban wastes compared to an unfertilized control and the build-up of Zn could be regarded as a beneficial side-effect of using sewage sludge as a fertilizer due to the status of Zn as an essential element.In conclusion, our data indicates that contemporary urban waste products can be used for supplementary fertilization purposes in agriculture with no substantial risks related to potentially toxic elements.

Use of alum water treatment sludge to stabilize C and immobilize P and metals in composts.

Alum water treatment sludge is composed of amorphous hydroxyl-Al, which has variable charge surfaces with a large Brunauer-Emmett-Teller (BET) surface area (103 m(-2) g(-1)) capable of specific adsorption of organic matter molecules, phosphate, and heavy metals. The effects of adding dried, ground, alum water treatment sludge (10% w/w) to the feedstock for composting municipal green waste alone, green waste plus poultry manure, or green waste plus biosolids were determined. Addition of water treatment sludge reduced water soluble C, microbial biomass C, CO2 evolution, extractable P, and extractable heavy metals during composting. The decrease in CO2 evolution (i.e., C sequestration) was greatest for poultry manure and least for biosolid composts. The effects of addition of water treatment sludge to mature green waste-based poultry manure and biosolid composts were also determined in a 24-week incubation experiment. The composts were either incubated alone or after addition to a soil. Extractable P and heavy metal concentrations were decreased by additions of water treatment sludge in all treatments, and CO2 evolution was also reduced from the poultry manure compost over the first 16-18 weeks. However, for biosolid compost, addition of water treatment sludge increased microbial biomass C and CO2 evolution rate over the entire 24-week incubation period. This was attributed to the greatly reduced extractable heavy metal concentrations (As, Cr, Cu, Pb, and Zn) present following addition of water treatment sludge, and thus increased microbial activity. It was concluded that addition of water treatment sludge reduces concentrations of extractable P and heavy metals in composts and that its effect on organic matter stabilization is much greater during the composting process than for mature compost because levels of easily decomposable organic matter are initially much higher in the feedstock than those in matured composts.

Environmental Risk Assesment of Heavy Metals Content of Municipal Solid Waste Used as Organic Fertilizer in Vegetable Gardens on the Jos Plateau, Nigeria

This study was conducted on vegetable gardens in and around Jos on the Jos Plateau, North central Nigeria; a city which has had strong European influence as a result of a long history of tin mining activity in the area. The study seeks to assess the degree of accumulation and/or contamination of the heavy metals in compost from municipal solid waste due for application as organic fertilizer in vegetable gardens as well as the potential human health risk associated with the consumption of vegetables grown with such organic fertilizer. Three waste dumpsites in Jos and gardens were selected where vegetables cultivation (cabbage, lettuce, spinach, turnip, carrot, radish, beet root, tomato and spring onions) are practiced. The representative samples of compost material, agricultural soil and vegetables were collected and analyzed for heavy metals such as: As, Cd, Co, Cr, Ni, Pb, Cu, Zn, Sb and Se. Geochemical results show that the concentrations of these elements in the compost are higher (in decreasing order of As>Cd>Zn>Pb>Cu>Cr) compared to that in the soils yet to be applied the organic fertilizer. The degree of contamination of the soils and the compost, the transfer factor (TF) from the agricultural soil to vegetables and its health risk index (HRI) were calculated. Results show that in general, the agricultural soils are severely contaminated by As, Cd, Zn and Pb (CF= 10-25). Other elements such as Cr, Cu and Ni have moderately contaminated the soil. All the vegetables seem to have been severely contaminated by Se and As (Se>As>Zn) and therefore are good accumulators of these toxic metals. The leafy and the root vegetables appear to be the major accumulator of Se and As respectively. The TF of As in all the different varieties of vegetables is >1, indicating that this element is readily absorbed by these plants. The HRI value for As, Pb and Zn is >1 for the all the vegetables and therefore is unsafe posing serious human health risks.

Composting of urban solid waste in Lomé, Togo: Fate of some heavy metals (Ni, Cu, Zn, Pb and Cd)

Metals may constitute problems in waste management because of their multiple sources and potentially high toxicity of some constituents. Processes of composting do not always guarantee acceptable quality of the compost in terms of hazardous metals. The aim of this article is to assess the balance of some heavy metals during the composting of different categories of urban waste. The fraction of the super fines, i.e. with a particle size of less than 10 mm, contributes 30 to 56% of the total, average contents of metals in compost. Sorting of waste into various fractions such as plastics, hazardous materials, glass, miscellaneous combustible material, metals, and super fines lowers the metal contents in finished compost by about 80%. The remaining 20% can be washed during the fermentation of windrows or, still better, can be reduced by chemical complex formation in the compost as shown by the leaching adequate test. Keywords : Heavy metals, composting, leaching test.

The usability of the IR, RAC and MRI indices of heavy metal distribution to assess the environmental quality of sewage sludge composts

To assess the environmental quality of compost, it is insufficient to use only total metal concentration. Therefore in this study, the stability of metals in compost and the environmental risk they pose were assessed by three indices that have been proposed for soils or sediments: the IR, the RAC and the MRI. In mature composts, the highest bonding intensity was for Ni (0.79<IR<0.93), then for Cu (0.56<IR<0.65) and Pb (0.55<IR<0.73), and the lowest for Zn (0.19<IR<0.25). Although, both the IR and the RAC are useful indices for evaluating the mobility of metals, they do not take into account their toxicity. Therefore, the overall classification of compost should also include the MRI, at which metal toxicity from the most available fractions is considered. Based on the MRI ranged between 10.0 and 11.6, all composts evaluated posed a low risk.

Recycle and reuse of natural zeolites from composting process: a 7-year project

A 25% w/w of natural zeolite (clinoptilolite) has been used in the composting process of sewage sludge for several times in order to define the recycle index (RI) and which mathematical model has the ability to describe this phenomenon. The final results indicated that under the circumstances, the same amount of natural zeolites can be used more than 22 times (RI = 22) which makes the whole process more sustainable and feasible. The uptake of heavy metals from sewage sludge using natural zeolite and the reuse times seems to assess the change of heavy metals in compost. The heavy metal content of zeolite directly reflects on the reuse times according to the final results. The results from the mathematical (theoretical) equations show similar results with the real experimental data.

Effect of methods of preparation on distribution of heavy metals in different size fractions of municipal solid waste composts

The present study compares the distribution and nature of heavy metals in composts from 12 cities of India, prepared from different types of processed urban solid wastes, namely mixed wastes (MWC), partially segregated wastes (PSWC), and segregated bio-wastes (BWC). Compost samples were physically fractionated by wet sieving, followed by extraction of heavy metals by dilute HCl and NaOH. Bigger particles (>0.5 mm) constituted the major fraction in all three types of composts and had a relatively lower concentration of organic matter and heavy metals, the effect being more pronounced in MWC and PSWC in which a significant portion of the heavy metals was distributed in finer size fractions. Cd, Ni, Pb, and Zn were extracted to a greater extent by acid than by alkali, the difference being greater in MWC, which contained a higher amount of mineral matter. In contrast, Cu and Cr were extracted to a greater extent by dilute alkali, particularly from BWC containing a higher amount of organic matter. Water-soluble heavy metals were generally related to the water-soluble C or total C content as well as to pH, rather than to their total contents. This study concludes that wet sieving with dilute acid can effectively reduce heavy metal load in MWC and PSWC.

Characterisation of Municipal Solid Waste Compost (MSWC) from Selected Indian Cities—A Case Study for Its Sustainable Utilisation

Utilisation of Municipal Solid Waste is important to curb the ever rising demand of scarce land for its disposal. Changing life style patterns, particularly in urban areas, has led to increase in generation of MSW. Municipal solid waste from Indian cities estimated to have 40% - 60% organic matter, which could be recycled as compost. The most suitable way to recycle it with low investment is aerobic composting using windrow method. With the compliance of Municipal Solid Waste (Management and Handling) Rules 2000, many cities in India are making compost with organic portion of MSW. Before applying MSWC for agricultural uses, it is important to inventories heavy metals in compost to assess its toxicity. In the present study the compost samples were quantified for its toxicity from three highly populated cities of India, i.e., Delhi (Capital of India), Ahmedabad (Gujarat) and Bangalore (Karnataka). The MSWC samples were analysed for total heavy metals and in extractable fractions. Few samples were found with higher concentration of metals then the prescribed limits for its application as compost in Indian MSW rules, whereas, samples have not showed significant heavy metals concentration in extractable fractions. Therefore, studied MSW compost samples had demonstrated its suitability to use as green compost.

Short-Term Agronomical Effects of Olive Oil Pomace Composts on Pisum arvense L. and Trifolium subterraneum L. and Impacts on Soil Properties

Olive oil pomace (OLP) contains organic matter and nutrients that could be recycled by composting and supplying it to crops, solving the problem of disposal. The effects of two OLP composts (C1 and C2) were assessed on two leguminous forage crops commonly cropped in the local livestock farms. In particular, C1 was applied on proteic pea and C2 on clover, compared with a mineral fertilizer (Min) and a commercial organic–mineral fertilizer (Org-min). The influence of composts on some soil chemical properties was also investigated. The application of C1 significantly increased proteic pea dry weight at the end of the cycle by 27.2% and 52.0% and grain yield by 23.2% and 43.6%, in comparison with Org-min and Min, respectively. The clover dry weight during the entire cycle was lower in C2, in comparison with the other treatments, while no significant difference was found between C2 and the Org-min treatment both in yield and plant height. Soil nitrate decreased from the beginning to the end of the trial in C1 and C2 plots by 22.8% and 50.9%, respectively. Soil phosphorous content significantly increased in Min by 32.4 and 41.7% compared to C1 and C2, respectively. These results showed that the substitution of commercial fertilizers with compost could be an environmentally sustainable solution. The high presence of heavy metals in compost should not affect soil application at least in this short-term trial.

Fractionation, Characterization and Speciation of Heavy Metals in Composts and Compost‐Amended Soils

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Physiologically based extraction of heavy metals in compost: Preliminary results

A physiologically based extraction test (PBET) was run for the extraction of six metals (Cu, Zn, Cd, Cr, Ni and Pb) in four composts containing high concentrations of heavy metals. An aqueous solution of pepsin plus citric, acetic, and malic acids buffered to pH 2 was used to simulate the gastric mixture, and an extraction of 1 h at 37 °C was run with a solid:liquid ratio of 1:100. The results were compared to those obtained using water and CaCl 2–DTPA solution. The PBET extracted far more metals than water, but less than CaCl 2–DTPA for Cu, Pb and Cr, while giving similar or slightly lower results for Cd, Zn, and Ni.