Influence of aeration rate and reactor shape on the composting of poultry manure and sawdust

Effect of moisture content, aeration rate, and C/N on maturity and gaseous emissions during kitchen waste rapid composting

To determine factors affecting compost maturity and gaseous emissions during the rapid composting of kitchen waste, an orthogonal test was conducted with three factors: moisture content (MC) (55%, 60%, 65%), aeration rate (AR) (0.3,0.6 and 0.9 L·kg^-1DM·min^-1) and C/N ratio (21, 24, 27). The results showed that the importance of factors affecting compost maturity was: C/N > AR > MC, optimal conditions were: C/N of 24, AR of 0.3 L·kg^-1DM·min^-1and MC of 65%. For gaseous emissions, the sequence of essential factors affecting NH₃ emissions was: C/N > MC > AR, and the optimal parameters for NH₃ reduction were: C/N of 27, MC of 65%, and AR of L·kg^-1DM·min^-1. The important factors affecting N₂O and H₂S emissions are both: MC > C/N > AR, while their best parameters were different. The optimal parameters for N₂O emission reduction were MC of 60%, AR of 0.3 L·kg^-1DM·min^-1 and C/N of 24, while these for H₂S were MC of 55%, AR of 0.3 L·kg^-1DM·min^-1 and C/N of 21. The C/N mainly affected the compost maturity and AR further affected the maturity and pollutant gas emissions by influencing the temperature and O₂ content. Considering comprehensively the maturity and gaseous reduction, the optimal control parameters were: MC of 60%-65%, AR of L·kg^-1DM·min^-1, and C/N of 24-27.

Accurate investigation of the mechanism of rhamnolipid biosurfactant effects on food waste composting: A comparison of in-situ and ex-situ techniques

The long process time and low product quality are major challenges in the composting process. To overcome the above challenges, the effects of produced biosurfactants on composting were investigated as a biological model. Pseudomonas aeruginosa IBRC-M 11180 inoculum and its supernatant were used as in-situ and ex-situ treatments in the composting process, respectively. The results showed that the presence of rhamnolipid biosurfactants in the composting process could improve many parameters such as maximum temperature, electrical conductivity (EC), cation exchange capacity (CEC), C/N, and germination index (GI). The GI value above 80% was observed for in-situ and ex-situ reactors on 12th day, while for the control was observed on 18th day, which indicates the significant effects of rhamnolipids on process time reduction. The C/N ratios of final compost for ex-situ, in-situ, and control reactors were 12.83, 13.27, and 17.05, respectively, which indicates the rhamnolipids also improves the quality of the final product. To better understand the performance of the rhamnolipids in the composting, wettability changes of the compost surface were evaluated. Our results show that the produced rhamnolipids altered the waste wettability from intermediate wet (θ = 85°) to water-wet (θ = 40°). It can be concluded that the presence of biosurfactants in composting leads to an increase in the contact surface area of microorganisms with nutrient sources and consequently improves the composting process. Furthermore, comparative studies showed that the in-situ treatment has better effects on composting, thus it can be an economically significant achievement because of the high cost of ex-situ treatment.

An enhanced composting process with bioaugmentation: Mathematical modelling and process optimization

In this paper, two different types of biowaste composting processes were carried out - composting without and with bioaugmentation. All experiments were performed in an adiabatic reactor for 14 days. Composting enhanced with bioaugmentation was the better choice because the thermophilic phase was achieved earlier, making the composting time shorter. Additionally, a higher conversion of substrate (amount of substrate consumed) was also noticed in the process enhanced by bioaugmentation. A mathematical model was developed and process parameters were estimated in order to optimize the composting process. Based on good agreement between experimental data and the mathematical model simulation results, a three-level-four-factor Box-Behnken experimental design was employed to define the optimal process conditions for further studies. It was found that the air flow rate and the mass fraction of the substrate have the most significant effect on the composting process. An improvement of the composting process was achieved after altering the mentioned variables, resulting in shorter composting time and higher conversion of the substrate.

The influence of vermicomposting on photosynthetic activity and productivity of maize (Zea mays L.) crop under semi-arid climate

Food production and waste recycling are the two major issues faced globally with rapidly increasing population. Recycling organic wastes to crop amendments could be a possible solution to these issues. Earthworms transfer organic waste to compost, which is used to grow crops and increase crop productivity. This study assessed the impact of vermicompost produced from the residues of six desert plant species, i.e., (Ziziphus mauritiana, Aerva javanica, Calligonum comosum, Sacchrum benghalens, Calligonum polygonoides and Prosopis cineraria) combined with farmyard manure (5 t ha-1) on growth, yield and photosynthetic activity of maize crop. Earthworm species Eisenia fetida (Savigny, 1826) was used to prepare vermicomposting of all tested plant species. The desert species were collected from natural habitats, chopped, dried, mixed with FYM and then earthworms were released to prepare the vermicompost. The earthworms were excluded twenty days after release and resultant was considered as compost and used in the experiment. Results revealed that application of P. cineraria vermicompost resulted in the highest plant height (75.33 cm), stem diameter (22.66 mm), cob length (17.66 cm), number of grains/cob (374.67), 1000-grain weight (260.41 g) and grains yield (3.20 t/ha). Application of P. cineraria vermicompost resulted in the highest uptake of macronutrients, i.e., N (91.01%), P (22.07%), K (80.41%), micronutrients, i.e., Fe (19.07 ppm), Zn (40.05 ppm), and phenolic contents (150). Application of P. cineraria vermicompost also resulted in the highest quantum photosynthetic yield (0.42 mole C/mole of photon), chlorophyll florescence (355.18 moles of photon m-2s-1) and electron transport rate (310.18 micro mole m-2s-1). It is concluded that vermicomposting has the potential to improve growth and yield of maize crop. Particularly, application of vermicompost obtained from P. cineraria can be used to improve the growth and yield of maize crop. Nonetheless, field trials are necessary for a wide scale recommendation.

Effects of carbon-based additives and ventilation rate on nitrogen loss and microbial community during chicken manure composting

Aerobic composting is a sustainable method for chicken manure recycling, while its unsuitable porosity and carbon to nitrogen ratio (C/N) may result in high nitrogen loss and incomplete composting. With the aim to investigate the effects of carbon-based additives and two ventilation rates on chicken manure composting and microbial community, two series of treatments were set up for chicken manure composting, in order to investigate their effects on the biodegradation process, ammonia (NH₃) emission, nitrogen loss, physiochemical properties and microbial community. The results showed that additives and ventilation rates set in the current study influenced the carbon dioxide (CO₂) production from the 2^nd week and also the physiochemical parameters during the entire process, while no inhibitory effect on the maturity were observed. With woody peat as additive, the NH₃ emission amount and nitrogen loss rate were shown as 15.86 mg and 4.02%, less than those in other treatments, 31.08–80.13 mg and 24.26–34.24%, respectively. The high aeration rate increased the NH₃ emission and nitrogen loss, which were varied when the additives were different. The terminal restriction fragment length polymorphism (T-RFLP) results showed that the additives and the ventilation rates changed the microbial community, while the prominent microbial clones belonged to the class of Bacilli and Clostridia (in the phylum of Firmicutes), and Alphaproteobacteria, Deltaproteobacteria and Gammaproteobacteria (in the phylum of Proteobacteria). Bacillus spp. was observed to be the most dominant bacteria in all the composting stages and treatments. It was concluded that woody peat could improve chicken manure composting more than other additives, especially on reducing nitrogen loss, meanwhile 0.18 L‧min^-1‧kg^-1 DM was suitable for various additives. Therefore, suitable additive and aeration rate could be used in practical application, which could significantly reduce nitrogen loss without influence on the compos maturity process.