Fabián Robles-Martínez

The overuse of chemical fertilizers highlights the need for sustainable alternatives, such as plant-growth-promoting bacteria (PGPB). However, bacterial inoculant performance may vary with plant species and growth conditions. This study evaluated the effects of microbial consortia combining Azospirillum brasilense, Pseudomonas putida, Bacillus sp., and Mycobacterium sp. on blue maize, broccoli, and tomato grown in commercial substrate and greenhouse soil. Consortium effects on early plant growth varied according to bacterial combination, plant species and substrate conditions. Pseudomonas putida + Bacillus sp. increased blue maize main root length by 28.45% in greenhouse soil and stem length by 44.70% in commercial substrate, while increasing tomato shoot dry weight by over 500% in greenhouse soil. Azospirillum brasilense + Bacillus sp. increased shoot dry weight by 154.06% in broccoli and 274.87% in tomato, both in commercial substrate. Results obtained with consortia containing Mycobacterium sp. provide exploratory evidence strictly under laboratory conditions. Due to the potential health risk associated with opportunistic and pathogenic species within this genus, these strains cannot be considered for agricultural applications or biofertilizer development, serving exclusively as a model for studies. Overall, these findings emphasize that PGPB consortium performance was context-dependent, emphasizing the importance of plant species, substrate conditions, and microbial composition when evaluating bacterial inoculants.

The increasing demand for food production has intensified the use of chemical fertilizers, raising concerns about their environmental impact. Plant Growth-Promoting Bacteria (PGPB) have emerged as a sustainable alternative; however, many studies are conducted under highly controlled conditions which do not accurately represent real agricultural systems. This study evaluated the effect of microbial consortia comprising of Azospirillum brasilense, Pseudomonas putida, Bacillus sp., and Mycobacterium sp. on plant growth under contrasting substrate conditions (commercial substrate and greenhouse soil). Their biostimulant potential was assessed in Zea mays (blue maize), Brassica oleracea (broccoli), and Solanum lycopersicum (tomato). The assessment included measurements of root and shoot elongation as well as dry biomass. The results demonstrated that microbial consortia significantly (p=0.01) improved plant growth compared to the control across all species. Among the treatments, the consortium Pseudomonas putida + Bacillus sp. had the best results by presenting significantly (p=0.01) higher values in root length, stem growth, and dry weight in both substrate types. Additionally, consortia containing Mycobacterium sp. demonstrated enhanced performance in greenhouse soil, particularly in biomass accumulation for Zea mays and Brassica oleracea. These results highlight the importance of selecting appropriate microbial combinations and validating their performance in environments that reflect practical agricultural conditions.

Agricultural and agro-industrial waste can be valorized through biodrying, a process that uses microbial activity to accelerate water loss to obtain a biodried material (BM) with high calorific value and potential use as a biofuel. This material has the advantage of being easily transported, stored, and preserved until later use. However, its high organic matter content allows it to be used for other purposes. In this study, the use of BM (made from orange peel, grass, mulch, pruning waste, and compost), either alone or mixed with fresh organic waste (FOW) as feed for Eisenia foetida in a vermicomposting system, was evaluated over a period of 49 days. The proportions of BM used were 100%, 75%, 50%, 25%, and 0%, with the remainder completed with FOW. During the bioprocess, temperature, moisture, and pH were monitored, and at the end of the experiment, the survival and reproduction of E. foetida as well as the quality of the humus obtained were analyzed. In the treatments containing 100% and 75% BM, worm survival was reduced by 28.5% and 7.7%, respectively, although the highest number of cocoons (28 and 24 cocoons kg_humus⁻¹) was observed in these treatments compared with all others. The humus obtained from all treatments complied with the NMX-FF-109-SCFI-2008 standard, which designates quality grades as extra, first, and second. The treatment with 100% BM produced first-quality humus, but the treatments with mixtures of BM and FOW produced extra-quality humus. The results support the diversification of BM uses and its incorporation into sustainable bioprocesses such as vermicomposting and the production of new value-added products.

Agricultural and agro-industrial waste can be valorized through biodrying, a process that uses microbial activity to accelerate water loss to obtain a biodried material (BM) with high calorific value and potential use as a biofuel. This material has the advantage of being easily transported, stored, and preserved until later use. However, its high organic matter content allows it to be used for other purposes. In this study, the use of BM (made from orange peel, grass, mulch, pruning waste, and compost), either alone or mixed with fresh organic waste (FOW) as feed for Eisenia foetida in a vermicomposting system was evaluated over a period of 49 days. The proportions of BM used were: 100%, 75%, 50%, 25%, and 0%, with the remainder completed with FOW. During the bioprocess, temperature, humidity, and pH were monitored, and at the end of the experiment, the survival and reproduction of E. foetida as well as the quality of the humus obtained were analyzed. In the treatments containing 100% and 75% BM, the worm population decreased by 28.5% and 7.7%, respectively, although the highest number of cocoons (28 and 24 cocoons kghumus-1) was observed in these treatments compared with all others. The humus obtained from all treatments complied with the NMX-FF-109-SCFI-2008 standard, which designates quality grades as Extra, First, and Second. The treatment with 100% BM produced First quality humus, but the treatments with mixtures of BM and FOW produced Extra quality humus. The results support the diversification of BM uses and its incorporation into sustainable bioprocesses such as vermicomposting and the production of new value-added products.

En el presente trabajo se contempla el tratamiento térmico por incineración de una “Mezcla Óptima” de residuos peligrosos y de manejo especial, como una opción viable desde el punto de vista ambiental y socioeconómico. Para determinar la “Mezcla Óptima” de residuos a incinerar se consideró en primera instancia que los residuos estuvieran libres de metales pesados y de compuestos organoclorados; en segunda instancia, el volumen de generación, la similitud en las características de los materiales que los componen, el porcentaje de humedad y su poder calorífico (solos o impregnados-mezclados con otros residuos o sustancias presentes en los mismos). En laboratorio se determinó el poder calorífico de los residuos peligrosos y de manejo especial a incinerar bajo el concepto “Mezcla Óptima”. Se determinó que la “mezcla óptima” a incinerar de residuos peligrosos y de manejo especial, es la compuesta por: un 80% de RPBI’S, un 15% RME’S (residuos de las operaciones de transporte) y un 5% de RP’S (fármacos caducos); mezcla que proporciona 485,468.6 kcal en 100 kg de residuos. Los resultados obtenidos de los muestreos y análisis efectuados (por un laboratorio acreditado) en la chimenea de salida del incinerador, estuvieron por debajo de los límites máximos permisibles de emisiones de contaminantes a la atmósfera, y el resultado del análisis CRETIB caracterizó a las cenizas como “No Peligrosas”. Datos que permiten comprobar la eficiencia de la mezcla propuesta y del sistema de incineración utilizado.

Biodrying and composting are aerobic processes to treat and stabilize organic solid waste, but biodrying involves a shorter process time and does not require the addition of water. The resulting biodried material (BM) is mainly used as an energy source in cement production or in municipal solid waste incineration with energy recovery, but when obtained from agricultural or agroindustrial organic waste, it could also be used as a soil amendment, such as compost (CO). In this study, the phytotoxicity of BM compared to CO, both made from organic wastes (orange peel, mulch and grass), was evaluated on seed germination and growth (for 90 days) of lettuce (Lactuca sativa L.) seedlings on treatments prepared from mixtures of BM and soil, soil (100%) and a mixture of CO and soil. The germination index (GI%) was higher for BM extracts (200 g/L) than for CO extracts (68% vs. 53%, respectively). According to their dry weight, lettuce grew more on the CO mixture (16.5 g) than on the BM (5.4–7.4 g), but both materials far exceeded the soil values (0.15 g). The absence of phytotoxicity suggests that BM acts as a soil amendment, improving soil structure and providing nutrients to the soil. Therefore, biodrying is a quick and low-cost bioprocess to obtain a soil improver.

El glifosato es un herbicida ampliamente utilizado, pero su uso excesivo ha generado preocupaciones por sus posibles efectos negativos en la salud humana y al ambiente debido a su persistencia en el suelo. La fitorremediación es el uso de la capacidad de las plantas para absorber, acumular y metabolizar contaminantes, se presenta como una alternativa viable y económica para remediar suelos contaminados con glifosato. Por tal motivo, el objetivo principal de la presente investigación es evaluar la capacidad remediadora de Chlorophytum comosum (mala madre) en suelos agrícolas contaminados con glifosato. Se realizó un experimento en un invernadero, contaminando intencionalmente un suelo agrícola con glifosato a una concentración de 1.2 ml kg-1 del ingrediente activo glifosato. Se establecieron tres tratamientos: suelo contaminado sin planta (TSx), suelo no contaminado + planta (TM) y suelo contaminado + planta (TMx). Se midieron variables biométricas de las plantas y se determinaron las concentraciones de glifosato y ácido aminometilfosfónico (AMPA) en suelo y tejidos vegetales a diferentes tiempos. Chlorophytum comosum cultivada en suelo contaminado (TMx) mostró un mayor desarrollo en altura de la planta y número de hojas, así como mayor biomasa en comparación con las plantas cultivadas en suelo no contaminado (TM). El tratamiento TMx presentó una reducción significativa en las concentraciones de glifosato y AMPA en el suelo a los 180 días, alcanzando una remoción del 100% del glifosato. Se detectó la presencia de AMPA en las raíces de las plantas de TMx. C. comosum demostró una notable capacidad de adaptación y tolerancia a suelos contaminados con glifosato y AMPA, aprovechando los compuestos derivados del glifosato como fuente de nutrientes y contribuyendo a su degradación en el suelo. Estos resultados sugieren que C. comosum representa una alternativa prometedora para la fitorremediación de suelos contaminados con glifosato.

The correct management of high-moisture organic waste (HMOW) is crucial to minimize its environmental impact and take advantage of its potential as a valuable resource, thus linking it to the circular economy, sustainable production and recycling. Processes such as anaerobic digestion, composting and, more recently, biodrying have been applied to support the sustainable management of HMOW. However, the latter has not yet been well characterized, so this study focuses on elucidating the behavior of microbial populations and their relationship with physical and chemical conditions during biodrying. In a greenhouse, a semi-static pile with an initial water content of 88%, composed of orange peel waste (80%), sugarcane bagasse (16.5%) and mulch (3.5%) was biodried for 50 days. Biodrying went through three stages: (1) the mesophilic stage, when different microbial populations decompose some organic matter, causing a temperature increase from 25 to 40 °C; (2) the thermophilic stage, in which the highest microbial counts were found, most of which corresponded to the highest temperatures reached and maintained between 40 and 62 °C, and, consequently, to the greatest decrease in water content (from 78 to 41%); and (3) the cooling phase, when the temperature dropped to 23–25 °C. The aeration and mainly the microbial activity were responsible for most of the water evaporation. Microbial activity in biodrying of HMOW ended on day 32, when the humidity was lower than 30% and the water activity (aw) was below 0.8. After that, moisture loss was carried out only by convection and radiation. Obtained biodried organic waste (10% water-content) could be used as an alternative fuel in many industries.

The transformation of agricultural waste into activated carbon represents an attractive approach as new and alternative source, but also as a reduction of pollution associated to the degradation of precursors. The organic residues sugarcane (Saccharum officinarum) bagasse-shell, orange (Citrus sinensis) peel-bagasse, and eucalyptus (Eucalyptus globulus) leaves, obtained from a biodrying process were transformed into activated carbons using phosphoric acid as activating agent. The resulting materials were physicochemically characterized and after that, carbonaceous electrodes were prepared to test the feasibility of using them in a discoloration electro-Fenton wastewater treatment process. Orange peel-bagasse biodried precursor transformed into activated carbon showed the highest efficiency when used as the modifier in a carbon paste electrode due to its highest porosity, electroactive area (24.9x10-2 cm2), and roughness (1.21 a.u.), also to its chemical affinity for anionic molecules. These properties, in addition to the capability of electro-sorb iron ions on the surface during the Fenton reaction, allowed a 44 % methyl orange discoloration efficiency. Sugarcane bagasse-peel and eucalyptus leaves biodried residues were also evaluated with efficiencies under 30 %, mainly attributed to intrinsic composition of the precursor materials. Resumen. La transformación de los residuos agrícolas en carbón activado representa un enfoque atractivo y novedoso, además de que representa una alternativa a la reducción de la contaminación asociada a la degradación de residuos orgánicos. Los residuos orgánicos de bagazo de caña de azúcar (Saccharum officinarum), bagazo y cáscara de naranja (Citrus sinensis), y hojas de eucalipto (Eucalyptus globulus), que fueron obtenidos de un proceso de biosecado, se transformaron en carbón activado utilizando ácido fosfórico como agente activante. Los materiales resultantes se caracterizaron fisicoquímicamente y después de eso, se prepararon electrodos de pasta de carbón modificados con estos materiales, para estudiar la viabilidad de utilizarlos en un proceso de tratamiento de aguas residuales mediante electro-Fenton. El precursor biosecado de bagazo y cáscara de naranja transformado en carbón activado mostró la mayor eficiencia cuando se usó como modificador en un electrodo de pasta de carbón, debido a su mayor porosidad, área electroactiva (24.9x10-2 cm2) y rugosidad (1.21), también debido a su mayor afinidad química por moléculas aniónicas. Estas propiedades, aunadas a la capacidad de electro-sorber iones de hierro en la superficie durante la reacción de Fenton, permitieron una eficiencia de decoloración del naranja de metilo del 44 %. También se evaluaron residuos biosecados de bagazo de caña de azúcar y hojas de eucalipto, con eficiencias inferiores al 30 %, atribuidas principalmente a la composición intrínseca de los materiales precursores.

Biodrying is a complex process that is very useful in the treatment of solid waste, where variables, such as temperature, thermal conductivity and the moisture content of organic matter, oxygen concentration in the pore space of the waste mass, microbial heat generation, microbial biomass, among others, are involved. Given this complexity, the development of mathematical models that help us to understand this bioprocess is fundamental. In the present work, a mathematical model, based on the finite difference method, was developed to predict the temperature profile at nine recording points, in an organic solid waste pile, during the biodrying process. The bioprocess was carried out under natural convection and solar radiation conditions, inside a greenhouse-type structure. A network of 5³ nodes, distributed in the x, y and z directions, on a rectangular prism, was developed. From this network, 27 base nodes were taken and the energy balance was developed for each node, and with this, the equation was obtained, in explicit form, to calculate the temperature. In these base equations, the microbial heat generation was considered, at between 2 and 140 W/m³; the convective coefficient was between 1 and 5 W/m² °C; and the daily records were taken inside the greenhouse for the solar radiation (0 to 450 W/m²), temperature (15 to 50 °C) and RH% (70 to 30). The modeled temperature profiles of the center (C) and the midpoints of the pile were, on average, 91% close to the experimental values, during the period from 0 to 20 days of biodrying; 70% close, during the period from day 21 to 35, the period when the modeled values were lower, due to the turning of the pile; and 94% close to the experimental values from day 36 to 50, when the modeled values were higher, also due to turning. The modeled temperature profiles of the left, right, upper and lower surfaces were, on average 92% close to the experimental profiles over the 0–35 day period, and the modeled and experimental values were practically identical from day 36 to 50 of the biodrying process.