The aim of this study is to evaluate the applicability of the catalytic activity (CA) of the Fe₃O₄ magnetic system in the adsorption/degradation of methylene blue and esterification. The thermal decomposition method allowed the preparation of Fe₃O₄ nanoparticles. The crystallites of the Fe₃O₄ structural phase present an acicular form confirmed by X-ray diffraction. Transmission electron microscopy results identified the acicular shape and agglomeration of the nanoparticles. Mössbauer spectroscopy showed that the spectrum is composed of five components at room temperature, a hyperfine magnetic field distribution (HMFD), two sextets, a doublet, and a singlet. The presence of the HMFD means that a particle size distribution is present. Fluorescence spectroscopy studied the CA of the nanoparticles with methylene blue and found adsorption/degradation properties of the dye. The catalytic activity of the nanoparticles was evaluated in the esterification reaction by comparing the results in the presence and absence of catalyst for the reaction with isobutanol and octanol, where it is observed that the selectivity for the products MIBP and MNOP is favored in the first three hours of reaction.

In Colombia, most commercial drying processes are frequently performed through the burning of wood and fossil fuels with high costs and environmental damage. Nevertheless, solar drying is a technique that could also be used to reduce many of the problems present in traditional drying techniques. Finding low-cost technology to install a solar dryer in a vulnerable community of women is an appropriate alternative; the transfer of knowledge on this technique could lead to greater empowerment of women and prevent gender inequality. This study evaluated the color and water activity of the mango (Mangifera indica L.) after a drying process in a greenhouse dryer. Furthermore, this study showed the relevance of implementing this technique in a community of women affected by the military conflict in Colombia. Results showed that a solar dryer achieved drying times of around 23–26 h, reaching water activity values below the 0.5 threshold which, according to international standards, has been considered as a food safety value. In addition, the color of the dry mango is slightly affected through this drying technique, providing a more acceptable consumer product. The application of the solar dryer has proven to be an easy-to-use and environmentally friendly method. On the other hand, it is also an opportunity to improve, with a low-cost investment, the living conditions of vulnerable communities.

Coffee is one of the most representative agricultural products in Colombia; several factors related to how it is produced, processed and marketed make it particularly important in post-conflict situations. The cultivation of coffee has acquired a very important role in the post-conflict stage that Colombia is experiencing. The rural areas hit hardest by violence are now seeing how improving agricultural conditions can help promote sustainable development and build peace in their regions. In coffee processing, women play an important role, with between 20% and 30% of coffee farms around the world being female-operated and up to 70% of labor in coffee production being provided by women. Women not only contribute to coffee processing, but they are also responsible for family activities such as cooking, and those activities are often made in wood stoves, thereby increasing their health risk. Against this background, this study presents the design and implementation of a biodigester fed by waste produced at Coffee Production Units (CPUs) located in the rural area of Tolima department in Colombia (an important scene of the armed conflict) in order to produce biogas for domestic cooking activities. Results show that implemented biodigester can produce between 1362 and 1597 kg/day (1.1704 and 1.3604 Nm³/day), which is enough energy for domestic activities for a family of four. Furthermore, it demonstrates benefits in the economic, social and environmental context of CPUs. Additionally, due to the importance of women in coffee production, this paper also evaluates the impact of the implementation of biodigesters in farms, which has shown that biodigester implementation positively impacts the production activities and activities performed by women, thereby increasing their life quality.

Cocoa production has emerged as an effective agricultural strategy to reduce conflict in Colombia, transitioning from coca to cocoa cultivation. While this shift has provided economic benefits, it has also resulted in the generation of substantial cocoa by-products. Although there are various alternative methods of utilizing these by-products, many farmers are unaware of them, and others lack the necessary tools to determine which alternative is the best to pursue. This study sought to explore sustainable options for cocoa waste utilization through the application of the Analytic Hierarchy Process (AHP). By employing technological surveillance, viable options for reusing cocoa residues were identified. The AHP results indicate that pellet production is a promising alternative for rural communities. It is also a potential source of energy that could address the community’s need for alternative energy sources. Initially, other energy production alternatives were not explored. However, in response to the AHP findings, this study also explored the use of cocoa waste combined with animal manure for energy generation through anaerobic digestion.