An anaerobic digestion process performed in two stages has the advantages of the production of hydrogen in addition to methane, and of further degradation of the substrate over the conventional process. The effectiveness of the implementation of this system for the treatment of lignocellulosic waste has been demonstrated. In 2020, more than 180 million tons of organic waste were generated worldwide from tomato crop production, posing a serious environmental risk. In the present investigation, methane production was compared in a two-stage system versus one-stage system from non-pretreated tomato plant residues. For this, different temperature (37 and 55 °C) and initial pH (5.5 and 6.5) conditions were evaluated during hydrogenesis and a constant temperature (37 °C, without pH adjustment) during methanogenesis. At the same time, a one-stage treatment (37 °C, without pH adjustment) was run for comparison purposes. The two-stage treatment in which the highest production of hydrogen, 12.4 mL/g VS, and methane, 252.3 mL/g VS, was observed occurred under the conditions of pH 6.5 and at 37 °C. However, this energy production was statistically similar (p < 0.5) to the one-stage treatment (365.4 mL CH₄/g VS). Furthermore, there were also no significant differences in the removal of volatile solids between the different treatments.

Tomato plant waste (TPW) is a significant agricultural byproduct that has been often underutilized. Recent studies have shown that its use to obtain methane in an anaerobic digestion (AD) process is viable. However, there is not much information available on studies to improve methane production from this substrate using statistical methods for optimization processes such as central composite design (CCD). For this investigation, CCD was adopted to analyze the effect of S/I ratio (substrate/inoculum ratio) (0.32–1.12), temperature (27–43 °C), and inoculum concentration (10.35–20.95 g VS/L) on methane generation and volatile solids (VS) removal in a batch AD system mono-digestion of TPW. The highest average value of methane yield was found to be 210.8 mL CH₄/g VS (S/I ratio 0.48, 40 °C, and 18.80 g VS/L), and the highest average value of VS removal was found to be 36.9% (S/I ratio 1.12, 35 °C, and 15.65 g VS/L). We obtain a model with a better fit for the VS removal (R² = 0.9587) than for the methane production (R² = 0.9156). Temperature and S/I ratio were the factors most important for methane production and VS removal, respectively.

The pollution of water bodies has deteriorated the quality of freshwater and the health of the natural ecosystem. In the present study, the water quality index (WQI) was used to evaluate the spatial and temporal contamination levels in Lake Yuriria, Guanajuato, Mexico. Water quality was monitored at 27 different locations (monitoring points) in the dry season (April) and after the rainy season (November), measuring 21 physicochemical water parameters, 2 biological parameters, and 19 metal concentrations. The data analysis revealed that Yuriria Lake is a eutrophic water body. Six monitoring points exhibited a poor WQI (25–50) in April, and seven monitoring sites were classified as having poor water quality in November. The remaining monitoring points showed a WQI categorized as fair (51–70) in both periods. The present study analyzes an extensive distribution of monitoring points over the lake’s surface in two periods, showing a significant spatial and temporal representation of water quality. In addition, the major pollution sources identified include agricultural runoff and effluents from a nearby waterway and freshwater river. Finally, the key physicochemical parameters that determined the water quality were identified. BOD₅, NH₄⁺, P, orthophosphates, DO, conductivity, TSS, and color were linked to anthropogenic pollution sources, and Li, Ni, Zn, Cd, Ba, and Pb concentrations were linked to natural contamination sources. This study demonstrates the utility and versatility of these methodologies in water quality research, and it is the first spatial and temporal WQI analysis of Yuriria Lake.

This review explores the application of metallic nanoparticles (MNPs) to enhance biogas production through anaerobic digestion (AD), from conventional and lignocellulosic substrates. MNPs have proven to increase methane yields, improve biogas quality, and accelerate microbial activity. However, the effectiveness of MNPs depends on factors such as dosage, type, and capping/functionalization. To address the challenges of digesting lignocellulosic biomass, strategies such as combining MNPs with traditional pretreatments, functionalizing nanoparticles (NPs) with acids, or immobilizing ligninolytic enzymes on magnetic NPs are discussed. These strategies improve hydrolysis and enhance methane production from recalcitrant substrates. Also, this review highlights sustainable techniques for MNPs application, including green synthesis of NPs using plant or microorganism extracts, recycling NPs and reusing digestates as biofertilizers.

Hydrogen (H2) is recognized as a promising energy carrier among the alternatives for obtaining clean energy, since it has a high energy efficiency (122 kJ / g) and can be obtained from lignocellulosic waste through a biological process. In the state of Guanajuato, high amounts of plant waste derived from tomato cultivation are generated because this is the crop mostly produced through protected agriculture. So, the objective of the present study was to consider tomato plant residues for the generation of hydrogen through the anaerobic digestion process. Two sources of inoculum, native microflora of the tomato plant and anaerobic sludge pretreated at 100 ° C for 24 h; and four mineral media at an initial pH of 6.5 ± 0.2 in batch experiments, were evaluated. The highest yield was 37.4 mLH2 / g SV using native microflora and mineral media with yeast extract. Hydrogen production was found like those reported in the literature for other type of waste, highlighting the no-need to pretreat the substrate or inoculum. Therefore, the methodology propose is efficient to the hydrogen production from tomato plant residues.

El biogás es una fuente de energía renovable que se obtiene a partir de la descomposición de sustratos orgánicos en ausencia de oxígeno, esto en un proceso conocido como digestión anaerobia. Dentro de los distintos tipos de sustratos aprovechables, los residuos agrícolas representan una opción destacada. En el estado de Guanajuato, durante el año 2024 se generaron aproximadamente 51,648 toneladas de residuos derivados del cultivo de frijol, los cuales en su mayoría no cuentan con un manejo adecuado para su disposición final. Este estudio evaluó el potencial de producción de biogás a partir de paja de frijol (PF) sin pretratar mediante digestión anaerobia, considerando tres variables clave: la relación sustrato/inóculo (S/I) (0.5, 1.0, 2.0 y 4.0), la concentración del inóculo (250 y 500 g/L) y el tamaño de partícula de la paja (mallas #12 y #20). Los experimentos se realizaron en condiciones en lote durante 36 días a temperatura ambiente. Se observó que la mayor producción acumulada de biogás (582.1 mL/g SV) se obtuvo con la relación S/I de 0.5, concentración de inóculo de 500 g/L y malla #20. La producción disminuyó significativamente con relaciones S/I de 2.0 y 4.0, probablemente debido a la acumulación de ácidos grasos volátiles que inhiben la metanogénesis, reflejada en una caída del pH por debajo de 5.0. El análisis estadístico reveló que solo la relación S/I tuvo un efecto significativo en la producción de biogás (p < 0.001), mientras que la concentración de inóculo y el tamaño de partícula no mostraron diferencias estadísticas relevantes. Sin embargo, el uso de partículas más pequeñas resultó en una ligera mejora en la producción, aunque no significativa, por lo que se sugiere utilizar tamaños mayores en futuros estudios para reducir costos de molienda. Además, se concluyó que el aumento en sólidos totales por mayor concentración de inóculo no causó aglomeración del sustrato ni afectó negativamente el rendimiento, lo que permite utilizar cualquiera de las dos concentraciones sin comprometer la eficiencia del proceso, siempre que se mantenga una relación S/I baja (0.5 o 1.0). Los rendimientos obtenidos fueron similares o superiores a lo reportado en estudios previos para otros sustratos lignocelulósicos que fueron sometidos a pretratamientos. Estos hallazgos refuerzan la viabilidad de la PF como fuente sostenible para la generación de biogás.