Digestate Post-treatment and Upcycling: Unconventional Moisturizing Agent for Food Waste In-Vessel Composting

AbstractNowadays, Tunisia faces challenging environmental and energy issues which relate mainly to the implementation of an appropriate solid waste management system capable of dealing with the high production of biowaste on the one hand, and the increased need for water and energy resources on the other. Therefore, the current study is intended to develop a closed cycle technical concept treating mainly food waste (FW) through combined biological processes. In this approach, FW anaerobic digestion (AD) was destined to provide a valuable input material for FW in vessel-composting by exploiting the produced digestates. To this end, the gathered AD-effluents of three systems (D1, D2, D3) were entirely analyzed to select, as a further step, the most suitable one to be subject of the suggested post-treatment. Hence, several physiochemical parameters were examined as key performance indicators. It mainly consisted of moisture content, pH, C:N ratio and heavy metals contents. The current findings depicted that the generated digestates were characterized by a high moisture content which inspired its utilization as an unconventional moisturizing agent (MA) aiming to reduce the fresh water consumption during the composting process. Thus, two experimental setups were carried out to evaluate the effect of the selected digestate on FW-in-vessel composting process performance, as a non-standard MA inserted to A2, comparing to the unamended one (A1) which was moistened by fresh water. In fact, basing on the above-mentioned criteria, the relatively high C:N ratio (of around 15), as well as the relatively significant rate of the required macro- and micro-nutrients promoted the exploitation of biochar-rich digestate (D3) as not only an efficient unconventional MA, but also as a composting process booster. Furthermore, the results revealed that the addition of D3 improved significantly the composting process performance in terms of steering parameters including the attained temperature, MC and pH. When it comes to the maturity and stability assessment, the decreased profiles of C:N ratio, the nitrification index (NI), as well as the respiration activity (AT4) ascertained the fulfilment of the required conditions for both A1 and A2 to produce stable and mature end-products. However, regarding the compost quality, the examined concentrations of heavy metals met the requirement set by German standards and attested that both A1 and A2 generated highly-qualified products, rated as class B and A, respectively. Furthermore, it is noteworthy to mention that even the AD-effluents which were classified as an “inappropriate substrate” to be inserted to the composters, met the required criteria to be applied directly to land as a highly-qualified liquid biofertilizer. This latter ascertained, additionally, the efficiency and feasibility of the suggested closed cycle for a sustainable FW management. Graphic Abstract

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From anaerobic to aerobic treatment: upcycling of digestate as a moisturizing agent for in-vessel composting process

Bioresources and Bioprocessing ◽

10.1186/s40643-020-00348-0 ◽

2020 ◽

Vol 7 (1) ◽

Author(s):

Nour El Houda Chaher ◽

Safwat Hemidat ◽

Mehrez Chakchouk ◽

Abdallah Nassour ◽

Moktar Hamdi ◽

...

Keyword(s):

Food Waste ◽

Rural Areas ◽

Waste Treatment ◽

C:N Ratio ◽

Point Of View ◽

Composting Process ◽

Anaerobic Reactors ◽

Physico Chemical ◽

Nitrification Index ◽

Urban And Rural Areas

AbstractIn Tunisia, there are crucial challenges facing both urban and rural areas, the most prominent of which are the production of organic waste, the need for waste treatment, the demand for water and energy and the need for a circular economy. To this end, the study was designed to develop a technical concept on closed cycle ‘biowaste to bioenergy’ treating, basically food waste (FW) through combined biological processes. In this approach, the generated digestate from FW anaerobic reactors was used successfully as a moisturizing agent for FW in-vessel composting. Four types of digestate were examined to be used as moisturizing agent (MA). The selection of the appropriate MA was achieved based on technical criteria; moisture content (MC), C:N ratio and heavy metals concentrations. The findings showed that the digestate obtained from anaerobic co-digestion of food waste and wheat straw (D1) was the most efficient AD-effluent to be added. In terms of composting process performance, the thermophilic phase of the amended reactor (A1) lasted 16 days and reached higher temperatures of about 72 °C, while the unamended one (A1) was characterized by a thermophilic temperature of around 66 °C indicating that the end products were of a pathogen-free compost. When it comes to the physico-chemical factors examined demonstrating that the biological conditions were sufficiently developed. The findings showed overall decreasing profiles during the composting period for moisture, C:N ratio as well as nitrification index (NI). From the quality-point of view, it was found that heavy metal concentrations had lower limits than those values set by German standards. Moreover, all the compost samples appeared to be stable and classified as class IV and V end product.

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Effect of pH, temperature and moisture content during composting of rice straw burning at different temperature with food waste and effective microorganisms

E3S Web of Conferences ◽

10.1051/e3sconf/20183402019 ◽

2018 ◽

Vol 34 ◽

pp. 02019 ◽

Cited By ~ 4

Author(s):

Irnis Azura Zakarya ◽

Siti Noor Baya Khalib ◽

Norhasykin Mohd Ramzi

Keyword(s):

Moisture Content ◽

Rice Straw ◽

Food Waste ◽

Ph Value ◽

Value Added ◽

Effective Microorganisms ◽

Brown Sugar ◽

Compost Quality ◽

Composting Process ◽

Straw Ash

Rice straw is considered as one of the most important agricultural residues and represented as one of the major by-products from rice production process. Normally, rice straw that produced after harvesting season been directly burned on-farm. Conversion of rice straw into value added compost will improve the productivity of plant, reduction of pollution towards environment and reduction of local pollution due to open burning activity. The objective of this study was to evaluate the performance of composting rice straw ash (RSA) with food waste (FW) and effective microorganisms (EM) in term of the compost quality (pH, temperature, moisture content). RSA was prepared by burning the raw rice straw at three different temperature of 300°C, 400°C and 500°C for one hour. EM used during the composting process was prepared by mixing of brown sugar, ‘tempe’ and water that can be used after one week of fermentation process. There are four treatments of RSA-compost; RSA (300°C), RSA (400°C), RSA (500°C) and control (raw rice straw) with the same amount of compost medium; 1kg black soil, 0.5kg RSA, 3L EM and 1kg FW. The composting process happens for 30 days. During the composting process, all the parameters of RSA-compost obtained in a range like; pH value 8-10, temperature 20-50°C and moisture content 40-60%. The result showed that all compost quality of rice straw ash compost obtained in an acceptable range for final compost to establish.

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Upgrading of Food Waste in-vessel Composting Process: Effects of Biochar-rich Digestate Addition

10.21203/rs.3.rs-113678/v1 ◽

2020 ◽

Author(s):

Nour El houda Chaher ◽

Abdallah Nassour ◽

Michael Nelles ◽

Moktar Hamdi

Keyword(s):

Moisture Content ◽

Food Waste ◽

Solid Waste Management ◽

Point Of View ◽

The Other ◽

Composting Process ◽

Anaerobic Reactors ◽

Other Hand ◽

Process Effects ◽

Nitrification Index

Abstract Nowadays, Tunisia faces challenging environmental and energic issues which concern mainly the implementation of an appropriate solid waste management system dealing with the high production of biowaste in one hand and the increased need for water and energy resources in the other hand. Therefore, the current study intended to develop a technical concept on closed cycle ‘biowaste to bioenergy’, treating mainly food waste (FW) through combined biological processes. In this approach, FW anaerobic digestion (AD) residue was destined to feed FW in vessel-composting as a valuable input material. To this end, the produced digestates from amended and unamended anaerobic reactors were entirely examined to select later the most appropriate AD-effluent. Therefore, the identification of the convenient digestate was achieved based on technical criteria ; moisture content (MC), C : N ratio and heavy metals concentrations. The findings showed that the digestate obtained from different digesters was characterized by a high moisture content which inspired its utilization as an unconventional moisturizing agent (MA) reducing the fresh water consumption during the composting process. Because of the high C : N ratio, relatively significant rate of the needed macro and micro-nutrients, the exploitation of biochar-rich digestate was recomended to be used as an unconventional MA in one hand and an aerobic co-substrate booster in the other hand. Results showed that D3 addition promoted the composting process performance comparing to the blank test (A1). Indeed, the thermophilic phase of the amended reactor (A2) lasted 15 days and reached higher temperatures of about 67 °C, while the unamended one (A1) was characterized by a thermophilic temperature of around 63 °C indicating that the end-products were of a pathogen-free compost. When it comes to the physico-chemical factors examined demonstrating that the biological conditions were sufficiently developed. The findings showed overall decreasing profiles during the composting period for moisture, C : N ratio as well as nitrification index (NI). From the quality-point of view, it was found that heavy metal concentrations had lower limits than those values set by German standards. Moreover, all the compost samples appeared to be stable and classified as class IV and V end-product.

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Fate of nutrients and heavy metals during two-stage digestion and aerobic post-treatment of municipal organic waste

Bioresource Technology ◽

10.1016/j.biortech.2017.12.019 ◽

2018 ◽

Vol 251 ◽

pp. 238-248 ◽

Cited By ~ 15

Author(s):

Christine Knoop ◽

Michael Tietze ◽

Christina Dornack ◽

Thomas Raab

Keyword(s):

Heavy Metals ◽

Organic Waste ◽

Post Treatment ◽

Two Stage

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Responses of anaerobic digestion of food waste to coupling effects of inoculum origins, organic loads and pH control under high load: Process performance and microbial characteristics

Journal of Environmental Management ◽

10.1016/j.jenvman.2020.111772 ◽

2021 ◽

Vol 279 ◽

pp. 111772

Author(s):

Wanli Zhang ◽

Xue Wang ◽

Wanli Xing ◽

Rundong Li ◽

Tianhua Yang

Keyword(s):

Anaerobic Digestion ◽

Food Waste ◽

Ph Control ◽

High Load ◽

Process Performance ◽

Coupling Effects ◽

Microbial Characteristics

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Resistance of bacteria isolated from leachate to heavy metals and the removal of Hg by Pseudomonas aeruginosa strain FZ-2 at different salinity levels in a batch biosorption system

Sustainable Environment Research ◽

10.1186/s42834-021-00088-6 ◽

2021 ◽

Vol 31 (1) ◽

Author(s):

Muhammad Fauzul Imron ◽

Setyo Budi Kurniawan ◽

Siti Rozaimah Sheikh Abdullah

Keyword(s):

Heavy Metals ◽

Heavy Metal ◽

Pseudomonas Aeruginosa ◽

Fresh Water ◽

Landfill Leachate ◽

Saline Water ◽

Resistant Bacteria ◽

Sanitary Landfill ◽

Salinity Levels ◽

Sanitary Landfill Leachate

AbstractLeachate is produced from sanitary landfills containing various pollutants, including heavy metals. This study aimed to determine the resistance of bacteria isolated from non-active sanitary landfill leachate to various heavy metals and the effect of salinity levels on the removal of Hg by the isolated bacterium. Four dominant bacteria from approximately 33 × 1017 colony-forming units per mL identified as Vibrio damsela, Pseudomonas aeruginosa, Pseudomonas stutzeri, and Pseudomonas fluorescens were isolated from non-active sanitary landfill leachate. Heavy metal resistance test was conducted for Hg, Cd, Pb, Mg, Zn, Fe, Mn, and Cu (0–20 mg L− 1). The removal of the most toxic heavy metals by the most resistant bacteria was also determined at different salinity levels, i.e., fresh water (0‰), marginal water (10‰), brackish water (20‰), and saline water (30‰). Results showed that the growth of these bacteria is promoted by Fe, Mn, and Cu, but inhibited by Hg, Cd, Pb, Mg, and Zn. The minimum inhibitory concentration (MIC) of all the bacteria in Fe, Mn, and Cu was > 20 mg L− 1. The MIC of V. damsela was 5 mg L− 1 for Hg and > 20 mg L− 1 for Cd, Pb, Mg, and Zn. For P. aeruginosa, MIC was > 20 mg L− 1 for Cd, Pb, Mg, and Zn and 10 mg L− 1 for Hg. Meanwhile, the MIC of P. stutzeri was > 20 mg L− 1 for Pb, Mg, and Zn and 5 mg L− 1 for Hg and Cd. The MIC of P. fluorescens for Hg, Pb, Mg, and Zn was 5, 5, 15, and 20 mg L− 1, respectively, and that for Cd was > 20 mg L− 1. From the MIC results, Hg is the most toxic heavy metal. In marginal water (10‰), P. aeruginosa FZ-2 removed up to 99.7% Hg compared with that in fresh water (0‰), where it removed only 54% for 72 h. Hence, P. aeruginosa FZ-2 is the most resistant to heavy metals, and saline condition exerts a positive effect on bacteria in removing Hg.

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Anaerobic digestion of food waste: Correlation of kinetic parameters with operational conditions and process performance

Biochemical Engineering Journal ◽

10.1016/j.bej.2017.11.003 ◽

2018 ◽

Vol 130 ◽

pp. 1-9 ◽

Cited By ~ 17

Author(s):

Lei Li ◽

Qin He ◽

Xiaofei Zhao ◽

Di Wu ◽

Xiaoming Wang ◽

...

Keyword(s):

Anaerobic Digestion ◽

Kinetic Parameters ◽

Food Waste ◽

Process Performance ◽

Operational Conditions

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Study on Drying Characteristics of Microalgae under Different Conditions

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.724-725.296 ◽

2013 ◽

Vol 724-725 ◽

pp. 296-299

Author(s):

Chun Xiang Chen ◽

Xiao Qian Ma ◽

Xiao Cong Li ◽

Wei Ping Qin

Keyword(s):

Moisture Content ◽

Mass Loss ◽

Fresh Water ◽

Chlorella Vulgaris ◽

Drying Process ◽

Drying Time ◽

Drying Characteristics ◽

Second Stage ◽

Drying System ◽

Two Stages

To find out an alternative of coal saving, a kind of microalgae, Chlorella vulgaris (C. vulgaris) which is widespread in fresh water was studied by digital blast drying system. The effect of the moisture content, drying thickness and temperature on the drying process of C. vulgaris were investigated. The results indicated that when the drying temperature is high, the moisture content is low and the material thickness is small, the drying time is short. The drying process of C.vulgaris can be divided into two stages, and the mass loss is mainly occurred in the second stage . The results will provide guidance for design of drying process and dryer of microalgae.

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