Search

The waste by the pruning Opuntia ficus-indica (OFI) cactus crop is considered a substrate for generating biogas. However, the physicochemical composition and the lignocellulosic fibers, difficulty the anaerobic digestion (AD) process, which generates biogas with a low yield of CH4. The present study implemented the application of combined pretreatments techniques: the mechanical (wet grinding), chemical (alkaline), thermal (modified basic hydrolysis), and organic load control in the OFI waste to control the parameters that influence AD are particle size, pH, residue solubility, and organic load control to evaluate the increase of the biogas. An orthogonal Taguchi L8 design experimental was employed to test the biochemical potential methane (BMP) assay. The better combination of pretreatments was mechanical level 1 (M1 = 0.5–0.8 mm), chemical level 2 (pH2 = 8.5), thermal level 1 (T1 = 30 °C), and concentration level 2 (C1 = 30 gCODL−1) resulted in the most significant increase of CH4 in the biogas with a production of 755.31 NmLCH4. The results show that the combined pretreatments in the OFI waste increased by 160% the methane production with a yield of 201.04 NmLCH4gVS−1 higher than the waste OFI without pretreatment (21.77 NmLCH4gVS−1). The equivalent energy potential of the waste was 5.96 GJton−1 and 33.98 GJ ha−1 yr−1 OFI waste. The combined pretreatments in the OFI waste improve the quality of the biogas and solve the environmental problem that is the inadequate management of the waste. [ABSTRACT FROM AUTHOR]

Water hyacinth (WH) is an invasive plant that generates adverse effects in water bodies, which, when removed, becomes a lignocellulosic residue that would use for methane production. The present investigation aimed to assess the increase in methane production when are applied and combined the pretreatments: grinding, chemical (pH adjust), thermal (temperature control), and concentration control, in anaerobic digestion (AD) through the biochemical methane potential (BMP) test, developed and based on a Taguchi L8 orthogonal arrangement. The results obtained from this study revealed that combined pretreatment has a positive effect on increasing methane production, concerning test control of WH chopped unpretreated, and achieving an increase of 260% to the better conditions (concentration of 30 g CODL−1, pH of 8.5, grinding with a disc mill, and a temperature of 40 °C, for 30 min). The degradation kinetic constant for the best combination of pretreatments as a function of volatile solids (VS) consumption and time was 0.0032 day−1, and the methane production kinetic constant was 0.17 day−1, with a yield of 111 NmL CH4 g VS−1 (equivalent to 0.02856 kg CH4 kg WH−1), and generation potential of 5712 kg of CH4 ha−1 year−1. [ABSTRACT FROM AUTHOR]

The waste generated by the mezcal and seafood restaurant industries has significant negative environmental impacts on soils, water, and air. However, these waste materials offer the potential for methane production through anaerobic digestion. This research focuses on evaluating a methodological strategy that involves using an enriched inoculum, co-digesting waste materials, and applying specific pretreatment (chemical, thermal, and adjusting the volumetric ratio of residues) to produce biogas with a high methane content, as assessed through the Biochemical Methane Potential (BMP) test. The results demonstrate that the enriched inoculum used in the test exhibited a pH of 8.18, an Alkalinity of 31 g CaCO3/L, and an alpha (α) ratio of 0.75. The BMP test was conducted over 29 days. In the most successful test, which involved pretreatment at a temperature of 50 °C, a residue ratio of 1 VSW (Volume of Seafood Waste)/2 VMV (Volume of Mezcal Vinasses), and a pH of 6.5, we achieved a methane production of 1420.51 ± 0.038 N mL CH4, with a biogas containing 81.5% methane. This process also yielded 175.37 N mL CH4 per gram of Volatile Solids (VS) and a degradation kinetic constant of 0.14 1/d. Through the methodological strategy used with the combination of an enriched and stabilized inoculum, the co-digestion of the waste for nutrient complementation, and the application of pretreatments, it was achieved that the different stages that constitute the anaerobic process allowed for the establishment of optimal conditions for the generation of biogas with a high methane content.Graphical Abstract: The waste generated by the mezcal and seafood restaurant industries has significant negative environmental impacts on soils, water, and air. However, these waste materials offer the potential for methane production through anaerobic digestion. This research focuses on evaluating a methodological strategy that involves using an enriched inoculum, co-digesting waste materials, and applying specific pretreatment (chemical, thermal, and adjusting the volumetric ratio of residues) to produce biogas with a high methane content, as assessed through the Biochemical Methane Potential (BMP) test. The results demonstrate that the enriched inoculum used in the test exhibited a pH of 8.18, an Alkalinity of 31 g CaCO3/L, and an alpha (α) ratio of 0.75. The BMP test was conducted over 29 days. In the most successful test, which involved pretreatment at a temperature of 50 °C, a residue ratio of 1 VSW (Volume of Seafood Waste)/2 VMV (Volume of Mezcal Vinasses), and a pH of 6.5, we achieved a methane production of 1420.51 ± 0.038 N mL CH4, with a biogas containing 81.5% methane. This process also yielded 175.37 N mL CH4 per gram of Volatile Solids (VS) and a degradation kinetic constant of 0.14 1/d. Through the methodological strategy used with the combination of an enriched and stabilized inoculum, the co-digestion of the waste for nutrient complementation, and the application of pretreatments, it was achieved that the different stages that constitute the anaerobic process allowed for the establishment of optimal conditions for the generation of biogas with a high methane content. [ABSTRACT FROM AUTHOR]

Highlights: [•] Complex DO diel curve was found by high frequency data records. [•] Night profile comprises sag and quasi stable sections previously undescribed. [•] P av , R and k a were estimated and DO modeled in a robust basis. [•] Temperature and particular stream characteristics influenced DO dynamics. [•] Useful insights for dissolved oxygen dynamics in shallow streams are provided. [Copyright &y& Elsevier]