Enhancement of Agro-Industrial Waste Composting Process via the Microbial Inoculation: A Brief Review

Composting is an important technology used to treat and convert organic waste into value-added products. Recently, several studies have been done to investigate the effects of microbial supplementation on the composting of agro-industrial waste. According to these studies, microbial inoculation is considered to be one of the suitable methods for enhancing the biotransformation of organic materials during the composting process. This review provides up-to-date research findings on microbial inoculation strategies and their role and functions in enhancing the composting process and the improvement of compost quality. Based on this review, the addition of microorganisms could enhance the composting process such as accelerating the organic matter degradation, mineralization and microbial enzymes activities, and the quality of the end-products such as high germination index. It is important to notice in this strategy that sludge’s microbial consortium is feasible to enhance the composting process in pilot-scale and industrial-scale productions. Besides, it also reduces the cost of compost production. The findings of this review show the various positive impact of microbial inoculation on agro-industrial waste composting which in turn might be useful as a reference for selecting a suitable inoculum based on the type of waste materials.

Evaluation of Bacterial Diversity in a Swine Manure Composting System Contaminated With Veterinary Antibiotics (VAs)

The objective of this work was identify microorganisms present in swine effluent composting system, under the contamination by most use veterinary drugs in Brazil. The composting took place for 150 days, where was addition of 200 liters of manure (these 25 liters initially contaminated with 17 antibiotics) in 25 kg of eucalyptus wood shavings. Microorganisms were measured at times (0 until 150 days), and were identified in the V3-V4 regions of the 16S RNAr for Bacteria, by means of next-generation sequencing (NSG). The results showing 7 different Bacteria Phyla and, 70 Bacteria Genus identified (more than 1% significance), in total there were more than 26 phyla and 585 genera of bacteria. The genus Brucella was found during mesophilic and thermophilic phases, this genus, not yet been reported in article involving composting process. These results suggested the potential of adaptation of the bacterial community with antibiotics denoted through the antibiotics.

Chemical characterization methods for biodegradable organic wastes with relevance for the composting process. Case study

The study aimed to develop some methods for the compositional characterization of biodegradable waste with relevance to the composting process at the laboratory level. For testing, four waste fractions were selected, such as waste-based on dehydrated sludge, waste from parks (leaves, branches), market waste (mixture of vegetable and fruit), and cardboard waste. For metals and phosphorus, several microwave digestion methods were applied. The ammonium nitrogen content (NH4-N) was determined using a number of extraction procedures (water, CaCl2, and KCl). Three certified reference materials were used for testing the validity of the results. Recovery percentages higher than 90% were obtained. The developed and validated methods are suitable for biodegradable waste characterization used in composting processes.

Transformation of Biodegradable Organic Municipal Solid Waste to Compost Using Stationary and Rotary Units

This study aims to convert the municipal solid waste (MSW), which include garbage and chicken manure as raw biodegradable organic waste to produce a compost in order to transform these materials into recommended fertilizer. The principle of aerobic composting method is a waste oxidation through holding these mixed raw materials with a ratio of 1:1 garbage and chicken manure in two units of composting, rotary unit and stationary unit with recommended Carbon/Nitrogen ratio C/N of 20:1 and pH of 6.5 with moisture content of about 40% by adding water during composting process and presence of oxygen naturally. The period time of composting process was 69 days to get normal temperature of compost bulk equal to ambient temperature and pH value as natural value using two composting units. The composting results during first 30 days shows the temperature values 59.5 and 55oC for rotary unit and stationary units that refers to microbial action of microorganism and decomposition of organic matter to energy as heat. The pH values were having acidic state during first week that refers to the formation of organic acids. The final compost characteristics show a C/N ratio of 20.8 and 22.275 for rotary and stationary units, respectively with a decrease in C% and N%, which refers to a successful composting process, where Nitrogen, Phosphor and Potassium NPK values were (1.428:1.719:4.508) % for rotary unit and (1.361:0.419:3.884) % for stationary unit and electrical conductivity of 5.5 and 6.04 mS/cm as acceptable value according to the recommended standard values.

Microbial community dynamics in the mesophilic and thermophilic phases of textile waste composting identified through next-generation sequencing

Composting is a promising source of mesophilic and thermophilic microorganisms directly involved in the decay of organic matter. However, there is a paucity of information related to bacterial and fungal diversity in compost and their enzymatic activities during the composting process. In this work, bacterial and fungal diversity during the mesophilic and thermophilic phases of textile waste composting was investigated as a way to explain the physical–chemical results obtained during the composting process. This was accomplished using a next-generation sequencing approach that targets either the 16S rRNA or ITS genomic regions of bacteria and fungi, respectively. It was observed that Proteobacteria, Bacteroidetes, and Actinobacteria were the dominant bacterial phyla present at the mesophilic phase but not at the thermophilic one. Composting textile waste exhibits a sustained thermophilic profile (above 55 °C) that usually precludes fungal activity. Nonetheless, the presence of fungi at the thermophilic phase was observed. Rozellomycota, Basidiomycota, and Ascomycota were the most dominant phyla during both composting phases. Such thermophilic fungi with great ability to decay organic matter could be isolated as pure cultures and used for the bioaugmentation of textile waste composting to achieve an advanced maturity level of textile waste compost.