Differences of Enzymatic Activity During Composting and Vermicomposting of Sewage Sludge Mixed With Straw Pellets

The study aims were focused on profiling eight hydrolytic enzymes by fluorescence method using a multifunctional modular reader and studying the proportion of basic microorganism groups during composting and vermicomposting of sewage sludge mixed with straw pellets in several proportions (0, 25, 50, 75, and 100%). The greatest decrease in enzymatic activity occurred in the first half of composting and vermicomposting. After 4 months of these processes, the least enzymatic activity was observed in the sludge with 50% and also 25% straw addition, indicating that straw is an important means for the rapid production of mature compost from sewage sludge. Enzymatic activity was usually less in the presence of earthworms than in the control treatment because some processes took place in the digestive tract of the earthworm. For the same reason, we observed reduced enzyme activity during fresh feedstock vermicomposting than precomposted material. The final vermicompost from fresh feedstocks exhibited less microbial biomass, and few fungi and G− bacteria compared to precomposted feedstock. The enzymatic activity during composting and vermicomposting of sewage sludge and their mixtures stabilized at the following values: β-D-glucosidase—50 μmol MUFG/h/g dw, acid phosphatase—200 μmol MUFP/h/g dw, arylsulphatase—10 μmol MUFS/h/g dw, lipase—1,000 μmol MUFY/h/g dw, chitinase—50 μmol MUFN/h/g dw, cellobiohydrolase—20 μmol MUFC/h/g dw, alanine aminopeptidase—50 μmol AMCA/h/g dw, and leucine aminopeptidase—50 μmol AMCL/h/g dw. At these and lesser values, these final products can be considered mature and stable.

Addition of Phosphatases and Phytases to Mature Compost to Increase Available Phosphorus: A Short Study

Agriculture depends on fertilizers to provide nutrients for plants. Phosphorus (P) is one of these nutrients and is the second-most necessary for plant growth. Global production of P fertilizer is concentrated in Morocco, China and the United States. A large amounts of P resources are found in organic wastes that can be transformed through phosphate-solubilizing microorganisms during the composting process. In this study, we first determined the enzymatic activity of phosphatases and phytase from Pseudomonas aeruginosa ATC 15442. Second, we evaluated the mineralization of P in mature compost when inoculated with P. aeruginosa ATC 15442, phytases, a cocktail of phosphate-solubilizing enzymes and their combinations. Finally, we evaluated different concentrations of the cocktail trying to release more P in the compost. The results indicated that P. aeruginosa exuded alkaline phosphatases, acid phosphatase, neutral phosphatase and phytase. The enzymatic cocktail increased inorganic P (Pi) when added to the mature compost: this was able to release up to 95% more Pi in the compost compared to the amount of Pi released in the control compost. The current study demonstrated the importance of adding the cocktail to enhance Pi in mature compost; however, further studies are required to confirm the results and practical applications.

DESIGN OF AN AUTONOMOUS SOLAR ROTARY COMPOSTER WITH SHREDDER SHAFT

Composting is the most efficient technique for managing household organic waste; it is the most widely used technique in the world. To improve and accelerate the composting process and produce rich and stable compost, it is necessary to grind and shred organic waste into small pieces to facilitate the degradation of the material by microorganisms. This paper presents the design, sizing, and modeling of a new self-contained, solar-powered, rotating composter with a shredding shaft. This shredding shaft rotates at 350 rpm and must run for 5 minutes before starting the composting process. This innovative machine shreds and composts organic household waste in situ to produce stable, mature compost suitable for agricultural use, providing an effective solution for managing and recovering organic household waste.

Waste Willow-Bark from Salicylate Extraction Successfully Reused as an Amendment for Sewage Sludge Composting

Due to the fact that compost is a valuable fertilizer that serves principally as a source of macronutrients, composting is one of the preferred methods of management of organic waste, including municipal sewage sludge. However, due to its high moisture content and low C/N ratio, sewage sludge cannot be composted alone. This study investigated the usefulness of waste willow-bark (WWB) (after salicylate extraction) as an amendment for municipal sewage-sludge composting in a two-stage system: an aerated bioreactor and a periodically turned windrow. Both organic matter (OM) removal and humification progress were monitored. It was found that the prepared feedstock (70% sewage sludge, 25% WWB, and 5% wood chips, w/w) enabled proper temperature profiles to be obtained, with a maximum temperature of 72.3 °C. The rate constant of OM degradation in the bioreactor was 0.25 d−1, almost 4-fold higher than that in the windrows. During composting, the concentrations of humic substances (HS), humic acids (HA), and the fulvic fraction (FF) changed. HS, HA, and FF formation proceeded according to 1. order kinetics, and their respective rates were 1.33 mg C/(g OM d), 1.03 mg C/(g OM d), and 0.76 mg C/(g OM d). However, in mature compost, FF predominated (ca. 70%) in HS. These results indicate that waste willow-bark, a product of salicylate extraction, can be successfully reused as an amendment during municipal sewage sludge composting. Both waste willow-bark reuse and sewage sludge composting are compatible with a circular economy.

Influence of Compost from Post-Consumer Wood on Development, Nutrition State of Plants, Microbiological and Biochemical Parameters of Substrates in Zonal Pelargonium (Pelargonium zonale)

The purpose of this study was to assess the possibility of using compost made from post-consumer wood in zonal pelargonium (Pelargonium zonale) cv. ‘Tex Mex’ cultivation. The influence of compost on the plant’s development and nutritional state, as well as the microbiological and enzymatic activity of the substrate was examined. Two variants of compost marked with the following letters: OPA and OPB were used. Both variants consisted of post-consumer wood waste (OP) (70% of weight) mixed with powdery waste from processing MDF boards (6%), mature compost from fiberboard waste (19%), high peat (4%), water and a biological inoculum “Activit Las”. Thirty kilograms of urea in two portions per prism were added to the OPA variant while ammonium nitrate (1.5 kg per prism), magnesium sulphate (0.4 kg per prism), potassium phosphate (0.8kg per prism) and calcium phosphate (0.9 kg per prism) were added to the OPB variant. The plants were cultivated into pots 12 cm in diameter and a capacity of 659 dm3 in the substrates consisting of peat with the addition of compost at different volume ratios. It was found that the medium type had a significant influence on the growth and flowering of the zonal pelargonium. The type of compost used was the determinant for microbiological total counts and activity. The chemical composition of the substrates significantly modified the plants’ nutritional state in terms of macro- and microelements. In summary, the study demonstrated that good quality ornamental plants can be successfully grown in peat substrate containing 25% or 50% of post-consumer wood compost.

Microbiological Activity during Co-Composting of Food and Agricultural Waste for Soil Amendment

This study aims to establish the relationship between ambient parameters and the diversity, composition, and function of microbial communities that predominate at each stage of the co-composting of food and agricultural waste. Culture-based and culture-independent methods were used to investigate the changes in the microbiota. The favorable conditions of high initial humidity and C/N ratio caused a decrease in the richness and biodiversity of the microbiota when such conditions existed. During the thermophilic stage, the total microbial number increased, and active mineralization of organic matter was carried out by members of the genera Bacillus, Caldibacillus, Aspergillus, and Penicillium. The fungal community was sensitive to drastic temperature changes. Byssochlamys dominated among fungi during the transition from the mesophilic to the thermophilic stage and during cooling. The biodiversity increased with time and was associated with the dynamics of germination and nitrification indices, so that the more diverse the microbial community, the higher the properties of compost that stimulate plant growth and development. The microbial community of the mature compost, together with mineral plant nutrients ready for consumption and humic compounds, make this compost a good soil additive.