Nilo M. Robles Carrillo

The valorization of the organic fraction of municipal solid waste (OFMSW), an underexplored lignocellulosic waste, represents a sustainable strategy for the production of adsorbents aimed at wastewater remediation, particularly against hexavalent chromium Cr(VI) from tannery effluents, a persistent environmental hazard in regions such as Tungurahua, Ecuador, where concentrations widely exceed regulatory limits. This study investigates the valorization of OFMSW pyrolyzed at 575 °C and subsequently activated by physical treatment with CO₂ to produce an activated biochar (BCA-OFMSW) for remediating aqueous solutions containing Cr(VI). The structural, ultimate, and textural properties were characterized before and after activation, and batch adsorption experiments evaluated the effects of pH, adsorbent dosage, initial concentration, and contact time, followed by equilibrium and kinetic modeling. Activation increased the surface area by more than two orders of magnitude (NLDFT = 1159.58 m² g⁻¹). Maximum removal occurred at pH 2, consistent with the alkaline point of zero charge of the material (pH_PZC = 11.47). The Freundlich model (R² = 0.9590) fitted the equilibrium data better than the Langmuir model (R² = 0.8453; qm = 58.86 mg g⁻¹), and the Elovich model gave the highest R² among the kinetic models tested (0.9654). Adsorption increased with temperature (ΔH° = +9.08 kJ mol⁻¹, an approximate estimate derived from the Freundlich constant). The pH dependence suggests a contribution of electrostatic attraction; post-adsorption XRD and EDS show chromium at the surface but do not identify its oxidation state, so Cr(VI) reduction could not be assessed. These results indicate that OFMSW-derived activated biochar is a promising adsorbent for Cr(VI)-contaminated effluents.

Population growth and societal development have significantly increased waste generation, whose accumulation in landfills causes environmental impacts and health risks for nearby populations. In this study, samples of the organic fraction of municipal solid waste (FORSU) were collected in five markets in different cantons of the province of Manabí, considering different time periods. Subsequently, physicochemical characterization was performed through proximal analysis and determination of the gross calorific value, complemented by statistical analysis to evaluate the influence of seasonality and geographical location on its properties. The results obtained allow criteria to be established to define the possible uses of FORSU and its potential for energy recovery through thermochemical conversion processes.

Pineapple biomass represents an abundant renewable source of carbon and a promising feedstock with considerable potential for the production of sustainable fuels. In the present study, the influence of liquid hot water (LHW) pretreatment on the pineapple mother plant was investigated at different controlled severities, then characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Results show that LHW pretreatment causes structural changes, leading to lignin and hemicellulose depolymerization up to a severity factor of 2.36–3.55, whereas at severity factors in the range of 4.13–5.90, cellulose, hemicellulose, and lignin appear to repolymerize. This pretreatment resulted in a higher hydrolysis efficiency (94.92 ± 0.04%) at 50 °C for 72 h. Compared with the untreated sample, the hydrolysis rate under these conditions increased by a factor of 2.16. SEM imaging revealed significant disruption of the PMP microstructure following LHW treatment, while XRD data confirmed an increase in the crystallinity index. FTIR analysis further indicated modifications in functional group profiles, supporting the structural and compositional changes induced by pretreatment. Overall, this study demonstrates the effectiveness of LHW pretreatment in enhancing the enzymatic digestibility and modifying the physicochemical properties of PMP biomass, providing a foundation for its valorization into high value bioproducts.

Bioenergy underpins a wide variety of technologies to transform biomass into fuels, chemicals, and biomaterials through sustainable routes. Significant advances in biomass valorization towards understanding their potential for energy production have occurred over the last decades. However, the complexity gap to utilize the entire lignocellulosic biomass (LCB) simultaneously remains overwhelming largely, which severely impedes the development of a bioresources-based economy. The exploration of complex characteristics of LCB fractions, including both chemical and structural aspects, is imperative. In the present study, 17 Ecuadorian LCB were prepared and extensively characterized to understand their compositional and structural characteristics through analytical approaches such as carbon–hydrogen–nitrogen–sulfur analysis, bomb calorimetry, X-ray diffraction, thermogravimetric analysis, and Fourier transform infrared spectroscopy. Regarding volatile matter content, all biomass sources presented remarkable levels ranging from 65.01 to 86.13%. Ash content was found in a range of 5.67 to 17.53%. Results show that the banana pseudostem displayed the highest cellulose content (59.56%). The lowest cellulose content was recorded in oil palm kernel shell (9.55%). The largest calorific value was found in sugarcane bagasse (22.62 MJ kg−1), while the minimum (12.50 MJ kg−1) was found in banana rachis. The highest crystallinity index was observed in rice husk followed by rice straw and plantain pseudostem. These results provide scientific guidance on the potential of collected biomasses as promising candidates for bioenergy production and related industrial applications.

Nostoc sp. is a cyanobacterium identified in several localities of Ecuador, and it exhibits significant potential in the pharmaceutical, food, and environmental sectors, which urges the exploration of its possible applications in the country. Macrocolonies of Nostoc sp. were collected at different seasons, and the content of metals, sulfur, and biochemical composition was analyzed according to altitude and geographic position. The results showed that the average carbohydrate content corresponds to 30.34% dry biomass, 27.38% ash, 25.33% protein, 7.66% crude fiber, and 0.71% fat. Regarding the content of metals and elements, it was found that Aluminum presented the highest value of 2049.23 mg/kg, followed by 1786.74 mg/kg, 1364.08 mg/kg, and 443.12 mg/kg of Fe, Mg, and S, respectively, and with the lowest for Cu, Ni, Pb, and Cd of 7.34 mg/kg, 5.62 mg/kg, 3.99 mg/kg and 0.74 mg/kg; respectively; with the following descending order: Al>Fe>Mg>S>Cu>Ni>Pb>Cd at all sites sampled and regardless of altitude and period of rain or drought. Consequently, its potential to adsorb these elements from the environment is preliminarily demonstrated, showing that it could be used in applications for bioremediation of contaminated soils and waters or be an essential bioindicator of environmental pollution.