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A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Environmental and Green Processes".

Deadline for manuscript submissions: closed (25 July 2022) | Viewed by 22515

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Prof. Dr. Antoni Sánchez

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Department of Chemical, Biological and Environmental Engineering, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, Spain
Interests: biological treatment of organic waste (composting and anaerobic digestion); solid-state fermentation to convert wastes into bioproducts and nanotechnology for environmental remediation
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Dear Colleagues,

Composting is a well-known technology that has been successfully implemented in many parts of the world. With the recent interest in circular economy, composting has become an attractive solution for the management of a wide range of organic wastes to be recycled as compost in agricultural or horticultural applications, as well as other uses such as restoration of contaminated soils or, more generally, amendment for bioremediation purposes.

Although a great deal of research has been published on composting, it is also evident that some knowledge gaps still exist, given the complexity of this technology, especially in the process—for instance, the relationship between physicochemical parameters and the biological phenomena, among others. This Special Issue “Composting in the Framework of Circular Economy” aims to present the recent advances of composting as a strategy to fulfil the objectives of circular economy. Topics include, but are not limited to:

Co-composting of different organic wastes, especially process performance and the quality of final compost;
Composting for the removal of emerging contaminants in organic wastes;
Decentralized composting: pros and cons, process experiences;
Environmental impact of composting processes, especially gaseous emissions.

In these topics, full- or pilot-scale studies are especially welcome, whereas non-representative few grams experiments are discouraged.

Prof. Dr. Antoni Sánchez
Guest Editor

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Keywords

Composting
gaseous emissions
emerging pollutants
environmental impact
organic wastes

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Published Papers (11 papers)

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Editorial

Jump to: Research, Review

3 pages, 194 KiB

Open AccessEditorial

Special Issue on “Composting in the Framework of a Circular Economy”

by Antoni Sánchez

Processes 2023, 11(5), 1573; https://doi.org/10.3390/pr11051573 - 21 May 2023

Cited by 2 | Viewed by 1491

Abstract

Composting has been recognized as a sustainable technology to treat and manage organic waste [...] Full article

(This article belongs to the Special Issue Composting in the Framework of Circular Economy)

Research

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12 pages, 1561 KiB

Open AccessArticle

Incorporation of Substrates and Inoculums as Operational Strategies to Promote Lignocellulose Degradation in Composting of Green Waste—A Pilot-Scale Study

by Edgar Ricardo Oviedo-Ocaña, Jonathan Soto-Paz, Viviana Sanchez-Torres and Antoni Sánchez

Processes 2023, 11(1), 241; https://doi.org/10.3390/pr11010241 - 11 Jan 2023

Cited by 2 | Viewed by 1716

Abstract

Composting is a sustainable alternative for green waste (GW) valorization contributing to the circular bioeconomy. However, the processing time must be reduced and the end-product quality must be improved. This study determined the effect of the incorporation of processed food waste (PFW), unprocessed food (UPFW), sawdust (SW), phosphate rock (PR) and a specific bacterial inoculum on GW-composting process parameters and product quality. Three treatments were evaluated in 120 kg piles: (i) TA: (GW + UPFW + PFW + inoculum), (ii) TB (GW + UPFW + PFW), and (iii) TC (GW). An inoculum of Bacillus sp. and Paenibacillus sp. was incorporated in the cooling phase for TA. On the other hand, the effect of the inoculum at the laboratory scale (20 kg reactors) was compared with that found at the pilot scale (120 kg piles). The incorporation of FW, SW, PR and the inoculum increased the amount of lignocellulose biodegradation (TA: 29.1%; TB: 22.7%; TC: 18.2%), which allowed for a reduction of up to 14 days of processing time. The product obtained for TA had a similar quality to the other two treatments, although a lower phytotoxicity was determined according to the germination index (TA: 95%; TB: 85%; and TC: 83%). The final product of TA showed the best agricultural characteristics with pH 8.3, TOC of 24.8%, TN of 1.32%, and GI of 98.8%. Finally, the scaling effect with the bacterial inoculum was shown to affect parameters such as the TOC, TN, GI, and, to a lesser extent, temperature and pH. The results obtained in this paper highlight the importance of optimizing the composting of GW, specifically with the use of co-substrates and specific inocula, which can be of interest for composting materials with a high content of lignocellulose such as GW. Full article

(This article belongs to the Special Issue Composting in the Framework of Circular Economy)

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13 pages, 1048 KiB

Open AccessFeature PaperArticle

Effect of Poultry Manure-Derived Compost on the Growth of eucalypts spp. Hybrid Clones

by Pedro F. Rizzo, María C. Salinas, Virginia Della Torre, Juan P. Diez, Leonardo F. Sallesses, Nicolás I. Riera, Pablo S. Pathauer, Dimitrios Komilis and Antoni Sánchez

Processes 2022, 10(11), 2182; https://doi.org/10.3390/pr10112182 - 25 Oct 2022

Cited by 2 | Viewed by 2202

Abstract

Interspecific hybrids of E. grandis × E. camaldulensis were generated to widen the plantation area. The aim of this study was to assess root capability and development for six different clones of eucalyptus grown in substrates made with three different composts derived from poultry manure. A factorial design was used to assess the effect of different composts on six growth variables. The analysis detected a greater effect from the genotype than the substrate. E. grandis × E. camaldulensis hybrid vegetative propagation was successful in alternative substrates formulated from composted poultry manure. GC8 was the genotype that showed the greatest differences for four the different variables among the substrates, being both the most sensitive and the one with the highest values for all parameters measured. The hybrids’ vegetative propagation was determined in alternative substrates formulated from poultry manure compost. The physicochemical characteristics of substrates composed of pine bark and sawdust provided adequate conditions for the growth of eucalyptus. GC8 was the genotype most sensitive to the use of different substrates, showing significant differences in the ratio of roots/callus, radicular dry weight, and cutting dry weight. These clones might be a good option for evaluating compost-based substrates for forestry applications. Full article

(This article belongs to the Special Issue Composting in the Framework of Circular Economy)

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17 pages, 1676 KiB

Open AccessArticle

Treatment of Sewage Sludge Compost Leachates on a Green Waste Biopile: A Case Study for an On-Site Application

by Chaher Ibrahim Irka, Pascale Prudent, Frédéric Théraulaz, Anne-Marie Farnet Da Silva, Laurence Asia, Didier Gori, Laurent Vassalo, Amandine Durand, Carine Demelas, Patrick Höhener and Pascal Wong-Wah-Chung

Processes 2022, 10(6), 1196; https://doi.org/10.3390/pr10061196 - 15 Jun 2022

Cited by 2 | Viewed by 2232

Abstract

This work proposes a suitable treatment for the leachates from a sewage sludge composting process using a specific windrow (biopile). The biopile’s evolution and organic content degradation were followed for 2 months with regular leachate spraying to assess the physico-chemical and biological impacts, and determine the risk of enrichment with certain monitored pollutants. The final objective was the valorization of the biopile substrates in the composting process, while respecting the quality standards of use in a circular economy way. Classical physico-chemical parameters (pH, conductivity, dissolved organic carbon (DOC), total dissolved nitrogen (TDN), etc.) were measured in the leachates and in the water-extractable and dry-solid fractions of the biopile, and the catabolic evolution of the micro-organisms (diversity and activities), as well as the enrichment with persistent organic pollutants (POPs) (prioritized PAHs (polycyclic aromatic hydrocarbons) and PCBs (polychlorinated biphenyls)), were determined. The results showed that the microbial populations that were already present in the biopile, and that are responsible for biodegradation, were not affected by leachate spraying. Even when the studied compost leachate was highly concentrated with ammonium nitrogen (10.4 gN L⁻¹ on average), it significantly decreased in the biopile after 2 weeks. A study on the evolution of the isotopic signature (δ¹⁵ N) confirmed the loss of leachate nitrogen in its ammoniacal form. The bio-physico-chemical characteristics of the biopile at the end of the experiment were similar to those before the first spraying with leachate. Moreover, no significant enrichment with contaminants (metal trace elements, volatile fatty acids, or persistent organic pollutants) was observed. The results show that it would be possible for composting platforms to implement this inexpensive and sustainable process for the treatment of leachates. Full article

(This article belongs to the Special Issue Composting in the Framework of Circular Economy)

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14 pages, 4638 KiB

Open AccessCommunication

A Composting Bedding System for Animals as a Contribution to the Circular Economy

by Abele Kuipers, Paul Galama, Lorenzo Leso, Kerstin Bruegemann and Marija Klopčič

Processes 2022, 10(3), 518; https://doi.org/10.3390/pr10030518 - 5 Mar 2022

Cited by 5 | Viewed by 4796

Abstract

By-products from forestry, agriculture and nature areas are used in compost bedded-pack housing (CBP) systems for animals. In this communication, we discuss the application of a CBP system to animal farms and aspects related to the recycling and reuse of the materials in the context of a circular economy. This study is based on data from ongoing projects and literature. The following systems are discussed: (i) composting material applied to a specialized animal housing system; (ii) adding a horticultural component to the animal farm by reusing the compost, and (iii) a cooperative mixed cattle and crop farming system. The success of integrating a compost bedding component in the system depends largely on the skills of managing the composting process, the application of the material in the field, and the cost of acquiring the material. When materials are amply available, then a real contribution to the circular economy can be made. Cooperation between farmers in the utilization of by-products is another route to a more circular economy. Moreover, the analyzed systems can be seen as a Greenhouse Gases (GHG) mitigation practice because they store carbon in the soil and improve soil quality. Full article

(This article belongs to the Special Issue Composting in the Framework of Circular Economy)

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15 pages, 1430 KiB

Open AccessFeature PaperArticle

Industrial Symbiosis for Optimal Bio-Waste Management and Production of a Higher Value-Added Product

by Edgaras Stunžėnas, Irina Kliopova, Daina Kliaugaitė and Rimas Pranas Budrys

Processes 2021, 9(12), 2228; https://doi.org/10.3390/pr9122228 - 10 Dec 2021

Cited by 3 | Viewed by 3160

Abstract

A considerable amount of food waste ends up in centralized treatment plants due to the lack of preventive measures, resulting in significant environmental impacts. Hospitality food waste management is even more resource-intensive because of animal by-products regulation. According to this regulation, companies must store and then consign waste to specific waste managers. The extensive need for transportation of high-moisture-content materials is the leading cause of the impact. Moreover, the management of category III animal by-products is costly for companies. A previous study has shown the economic benefits of decentralized animal by-product treatment by intensive composting in catering companies. Although the produced compost was characterized by exceptional quality parameters, it was phytotoxic. The investigation of hospitality waste management is scarcely discussed among scholars, and waste management on a regional scale is nearly absent. This study examines the regional management of hospitality food waste by exploiting the municipal waste management infrastructure and intensive composting at the source. The co-maturation experiment with animal by-products and municipal green waste primary composts showed that the phytotoxicity parameters of the cured compost were in the optimal range or below the thresholds (conductivity (1.1 mS cm⁻¹), dissolved organic carbon (82 mg kg⁻¹), and NH₄⁺/NO₃⁻ ratio (0.0027)). Additionally, the amounts of total nitrogen, water-soluble nitrogen, and water-soluble phosphorus in the compost were rated as very high. Finally, inventory and environmental impact analysis of the current and planned management approaches showed a reduction in 12 of 18 impact categories. Full article

(This article belongs to the Special Issue Composting in the Framework of Circular Economy)

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16 pages, 2153 KiB

Open AccessArticle

The Use of Phosphate Washing Sludge to Recover by Composting the Leachate from the Controlled Landfill

by Meriem Mobaligh, Abdelilah Meddich, Boujamaa Imziln and Khalid Fares

Processes 2021, 9(10), 1735; https://doi.org/10.3390/pr9101735 - 28 Sep 2021

Cited by 4 | Viewed by 2437

Abstract

The percolation of rainwater and runoff water through household waste in the dumpsite generally leads to an overabundance of leachate in Moroccan landfills, which is a source of soil, surface water and groundwater contamination. In order to ecologically solve the problem posed by the leachate in the dump site, to safeguard the environment and to contribute to sustainable development, we have carried out this study which aims to study the possibility of composting leachate with green waste and phosphate washing sludge. Various combinations with five substrates (leachate, green waste, sugar lime sludge, phosphate washing sludge and olive mill wastewater) in different proportions were used to build five windrows. A 24 h contact between the phosphate sludge or sugar lime sludge and the leachate took place prior to the addition of the green waste for the construction of the different windrows. This contact time ensured the absorption of a significant portion of the leachate and the disappearance of bad odor. A significant reduction was obtained with streptococci and mesophilic flora after 24 h of contact. The monitoring of the physicochemical parameters throughout the composting process showed that the temperature of the different windrows followed a good pace presenting all composting phases. Moisture, pH, C/N ratio and the percentage of degradation of the organic matter conformed to the quality standards of the compost. The combinations of the alkaline treatment and the composting process allowed a significant hygienization of the leachate. The results of the humification parameters and the E4/E6 ratio suggest that the composts obtained with phosphate sludge were the most stable and mature and can be used in the agricultural field or green space. Full article

(This article belongs to the Special Issue Composting in the Framework of Circular Economy)

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13 pages, 1990 KiB

Open AccessArticle

Advanced Characterization of Organic Matter Decaying during Composting of Industrial Waste Using Spectral Methods

by Saloua Biyada, Mohammed Merzouki, Hamada Imtara, Mohamed F. Alajmi, Karima Elkarrach, Hamza Mechchate, Raffaele Conte and Mohamed Benlemlih

Processes 2021, 9(8), 1364; https://doi.org/10.3390/pr9081364 - 4 Aug 2021

Cited by 11 | Viewed by 3198

Abstract

To date, compost maturation monitoring is carried out by physical-chemical and microbiological analysis, which could be considered an overweening consumption of time and products. Nowadays, spectroscopy is chosen as a simple tool for monitoring compost maturity. In the present investigation, spectroscopy analysis was performed in the interest of corroborating the compost maturity. This goal was achieved by using the X-ray diffraction, infrared spectroscopy, and scanning electron microscopy. X-ray diffraction analysis showed the presence of the cellulose fraction in compost samples. At the same time, the intensity of pics decreased depending on composting time, thus proving that there was organic matter degradation. Infrared and scanning electron microscopy analysis allow for confirming these results. The correlation between spectroscopies analysis and physical-chemical properties was employed by partial least squares-regression (PLS-R) model. PLS-R model was applied to build a model to predict the compost quality depending on the composting time, the results obtained show that all the parameters analysis are well predicted. The current study proposed that final compost was more stabilized compared with the initial feedstock mixture. Ultimately, spectroscopy techniques used allowed us to confirm the physical-chemical results obtained, and both of them depict maturity and stability of the final compost, thus proving that spectral techniques are more reliable, fast, and promising than physical-chemical analyses. Full article

(This article belongs to the Special Issue Composting in the Framework of Circular Economy)

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12 pages, 893 KiB

Open AccessFeature PaperArticle

Agronomic Characteristics of the Compost-Bedded Pack Made with Forest Biomass or Sawdust

by Lourdes Llonch, Cecilia Gordo, Marga López, Lorena Castillejos, Alfred Ferret and Teresa Balanyà

Processes 2021, 9(3), 546; https://doi.org/10.3390/pr9030546 - 19 Mar 2021

Cited by 10 | Viewed by 2727

Abstract

To ascertain the agronomic value of the material resulting from the compost-bedded pack (CBP) in dairy barns, a cross-over experiment was designed with eight dry non-pregnant Holstein cows. The study was performed in two 11-week periods. Bedding materials used were: (1) CBP with sawdust (S) and (2) CBP with forest biomass (FB). Samples were taken from the raw bedding materials and from the CBP across the experiment. We conducted an additional study preparing two piles, one of each CBP material, to accomplish a composting process of 3 months, where samples were also taken. Granulometry and some chemical composition characteristics of FB made it a suitable bedding material to be used as CBP, but its high moisture content limited the ability to absorb liquid manure. Both the degree of stability of the organic matter and the temperature evolution of CBP suggest that a real composting process did not occur. Finally, the composting process of the piles did not lead to any relevant change in CBP materials. From the agronomic point of view, S and FB present potentially valuable characteristics as regards organic amendment in the soil, thanks to their high organic matter content and low nutrient content. Full article

(This article belongs to the Special Issue Composting in the Framework of Circular Economy)

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Review

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15 pages, 545 KiB

Open AccessFeature PaperReview

Gaseous Emissions from the Composting Process: Controlling Parameters and Strategies of Mitigation

by Tahseen Sayara and Antoni Sánchez

Processes 2021, 9(10), 1844; https://doi.org/10.3390/pr9101844 - 18 Oct 2021

Cited by 37 | Viewed by 8692

Abstract

Organic waste generation, collection, and management have become a crucial problem in modern and developing societies. Among the technologies proposed in a circular economy and sustainability framework, composting has reached a strong relevance in terms of clean technology that permits reintroducing organic matter to the systems. However, composting has also negative environmental impacts, some of them of social concern. This is the case of composting atmospheric emissions, especially in the case of greenhouse gases (GHG) and certain families of volatile organic compounds (VOC). They should be taken into account in any environmental assessment of composting as organic waste management technology. This review presents the relationship between composting operation and composting gaseous emissions, in addition to typical emission values for the main organic wastes that are being composted. Some novel mitigation technologies to reduce gaseous emissions from composting are also presented (use of biochar), although it is evident that a unique solution does not exist, given the variability of exhaust gases from composting. Full article

(This article belongs to the Special Issue Composting in the Framework of Circular Economy)

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19 pages, 1035 KiB

Open AccessReview

A Review of Composting Process Models of Organic Solid Waste with a Focus on the Fates of C, N, P, and K

by Zheng Yang, Furqan Muhayodin, Oliver Christopher Larsen, Hong Miao, Bing Xue and Vera Susanne Rotter

Processes 2021, 9(3), 473; https://doi.org/10.3390/pr9030473 - 6 Mar 2021

Cited by 18 | Viewed by 6028

Abstract

To foster a circular economy in line with compost quality assessment, a deep understanding of the fates of nutrients and carbon in the composting process is essential to achieve the co-benefits of value-added and environmentally friendly objectives. This paper is a review aiming to fill in the knowledge gap about the composting process. Firstly, a systematic screening search and a descriptive analysis were conducted on composting models involving the fates of Carbon (C), Nitrogen (N), Phosphorus (P) and Potassium (K) over the past decade, followed by the development of a checklist to define the gap between the existing models and target models. A review of 22 models in total led to the results that the mainstream models involved the fates of C and N, while only a few models involved P and K as target variables. Most of the models described the laboratory-scale composting process. Mechanism-derived models were relatively complex; however, the application of the fractionation of substrates could contribute to reducing the complexity. Alternatively, data-driven models can help us obtain more accurate predictions and involve the fates of more nutrients, depending on the data volume. Finally, the perspective of developing composting models for the fates of C, N, P, and K was proposed. Full article

(This article belongs to the Special Issue Composting in the Framework of Circular Economy)

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