A high concentration of hydrogen sulfide (H2S) released from pig farming is one of the major environmental problems affecting surrounding communities. In modern pig farms, the bioscrubber is used to eliminate H2S, which is found to be driven mainly by the sulfur-oxidizing bacteria (SOB) community. Therefore, in this study, molecular biology techniques such as next-generation sequencing (NGS) and DNA microarray are proposed to study the linkage between enzyme activity and the abundance of the SOB community. The starting sludge (SFP1) and recirculating sludge (SFP2) samples were collected from the bioscrubber reactor in the pig farm. The abundance of microbial populations between the two sampling sites was considered together with the gene expression results of both soxABXYZ and fccAB. Based on the NGS analysis, the members of phylum Proteobacteria such as Halothiobacillus, Acidithiobacillus, Thiothrix, Novosphingobium, Sulfuricurvum, Sulfurovum, Sulfurimonas, Acinetobacter, Thiobacillus, Magnetospirillum, Arcobacter, and Paracoccus were predominantly found in SFP2. The presence of Cyanobacteria in SFP pig farms is associated with increased biogas yields. The microarray results showed that the expression of soxAXBYZ and fccAB genes involved in the oxidation of sulfide to sulfate was increased in Halothiobacillus, Paracoccus, Acidithiobacillus, Magnetospirillum, Sphingobium, Thiobacillus, Sulfuricurvum, Sulfuricurvum, Arcobacter, and Thiothrix. Both NGS and DNA microarray data supported the functional roles of SOB in odor elimination and the oxidation of H2S through the function of soxABXYZ and fccAB. The results also identified the key microbes for H2S odor treatment, which can be utilized to monitor the stability of biological treatment systems and the toxicity of sulfide minerals by oxidation.

The coir industry in India’s southern coastal regions, especially in the state of Kerala, is becoming increasingly concerned about the environmental impact of the accumulation and incremental increase of coir pith each year. The objective of this study was to assess the effect of pretreatment on the anaerobic digestion of coir pith. The characterization study of coir pith shows high organic content, which can be anaerobically digested to produce biogas. But, the high lignin content (30.91%) makes the process slow. To overcome this, a biological pretreatment method was tried using two microbial cultures belonging to fungal genera known to be lignin decomposers, viz., Trichoderma and Pleurotus. By using Trichoderma, lignin content was reduced by 3.7%, and the maximum gas production was obtained in a shorter time (19 days) in comparison with the sample without any pretreatment (24 days). When Pleurotus was used for lignin degradation, the lignin content was reduced by 6.78%, and the maximum gas production was obtained in a much shorter time period (14 days) in comparison with the former two methods. The gas produced comprises 74 ppm of methane, which has fuel value. The sludge after digestion was tested, which indicated a marginal increase in NPK value and hence can be used as fertilizer. The results of the study appear to be quite promising in the transition towards green energy by providing scope for the process of biomethanation, with the conclusion that further research can transform coir pith into a good renewable energy resource.

This work is a decision support contribution in Morocco’s household and similar waste management. This management based on total waste landfilling leads to several environmental impacts, such as the use of large land areas, also the gaseous pollutants released, such as methane. Our first action was to collect reference data on the composition of this waste through a physicochemical characterization in the landfill in the city of Mohammadia. We sorted the waste generated by four types of populations with different living standards. A quantity of 500 to 2315 kg was treated, which allowed us to classify the household waste studied into nine main components. The sorting results are (organic matter 54.94%, plastic 15,18%, paper and cardboard 9,72%, textiles 7,46%, sanitary textiles 5,82%, metals 2,20%, glass 1, 89%, Wood 1,82% and Other 1,28%). Thus, these results revealed organic matter dominance and an increase in the plastic rate, which did not exceed 8% in the past. Added to this, the physicochemical parameters results are (volatile matter 60,26%, Humidity rate 59,05%, a total organic carbon (TOC) 33,47%, and a lower heating value (LHV) 1840,3 kcal.kg-1). From these data, we can easily deduce that installing a sorting platform with a methanation and composting unit is the most suitable choice for recovering our waste. Therefore, we have chosen the methanation technology that meets the results obtained (dry batch and mesophilic) and sized this unit to assess its electricity production capacity that can be produced in our landfills. We carried out a scenario with a load factor of 0,9 and an electrical efficiency of 39%. The study results are 9 digesters to be built, 6.700 MW.y-1 of electrical energy produced, 14.523 tons.y-1 of refined compost, and 2.128.680 m3.y-1 of biomethane produced. By offering our own integrated and sustainable management system for household and similar waste, we have connected the landfill bins and the digesters to the same motor to avoid biogas leaks from the bins to the atmosphere and increase electrical efficiency by controlling the gas flow.