Juan Martín Delgado Naranjo

For over five decades, Colombia's armed conflict has constrained rural development, especially in the Territories Most Affected by the Armed Conflict (ZOMAC). Nonetheless, the agro-industrial sector offers significant potential for energy generation from non-conventional renewable sources, particularly biomass, estimated at over 500,000 TJ per year. This study assesses the economic feasibility of valorizing swine manure through anaerobic digestion in ZOMAC territories, promoting circular economy and sustainable development. Four operational and economic scenarios of biogas plants using upflow anaerobic sludge blanket reactors were evaluated through Net Present Value (NPV) and Discounted Payback Time (DPBT). Profitability was found to depend mainly on fiscal incentives and plant scale. Scenario 3, involving biogas upgrading to biomethane, achieved a positive NPV (0.03 million USD) and an Internal Rate of Return (IRR) of 12.7% under Colombian tax incentives (Laws 1715/2014 and 1819/2016), with a DPBT of 7.4 years. Doubling the processing capacity improved profitability (IRR = 26.8%, NPV = 1.1 million USD, DPBT = 4.2 years) and made electricity generation (Scenario 4) viable (IRR = 13.8%, NPV = 0.16 million USD). These findings highlight that fiscal incentives and scaling-up are decisive for achieving economic feasibility, environmental sustainability, and inclusive rural development in post-conflict Colombia.

Biofertilizers offer a sustainable alternative to chemical fertilizers, notorious for their harmful impact on the environment and human health. Sources of biofertilizers include cyanobacteria, such as those from the genus Arthrospira, which contain bioactive compounds that enhance plant growth directly and indirectly. To promote widespread biofertilizer adoption, experimental trials are essential to compare their efficacy against chemical fertilizers and different biofertilizer varieties. Some biofertilizers rely on ultrasonication for cell rupture, but since A. maxima undergoes sun‐drying to obtain the biomass powder, which also ruptures cells, ultrasonication may be unnecessary. We assessed the biofertilizer capabilities of Arthrospira maxima (Setchell & N.L. Gardner) Geitler biomass on three cash crops, banana (Musa acuminata Colla), cowpea (Vigna unguiculata L. Walp.), and eggplant (Solanum melongena Mill. Dunal). We compared sonicated and non‐sonicated biomass (both 20 g L⁻¹) against a commercially available, brown algae Ascophyllum nodosum (L.) biofertilizer (4 mL L⁻¹ OptiMar), a commercially available chemical fertilizer (1.5 mL L⁻¹ Triple15), and a negative control of tap water. Few differences were observed among A. maxima treatments, suggesting sonication might be unnecessary. OptiMar, Triple15, and the negative control did not yield the highest biometric values of any trait in any crop. If commercially available fertilizers and biofertilizers do not outperform the negative control, it raises crucial questions regarding their effectiveness and the appropriate concentrations at which they should be applied. Non‐sonicated biomass often outperformed OptiMar, Triple15, and the negative control, demonstrating the potential Arthrospira maxima has for stimulating plant growth without ultrasonication.

To meet Colombia’s energy needs by 2050, a total installed capacity of 42 MW across its power generation infrastructure is required. To achieve this, transitioning to cleaner energy sources, such as biomass—a non-conventional renewable energy—is necessary. Biomass is a promising renewable source for thermal and electrical energy production. This study researched the production of biogas from swine manure using a UASB reactor to valorize this waste. Swine manure was collected every 20 days from a pig farm with a capacity of 200 sows, located in Santa Rosa de Osos, Antioquia. The flow rate was increased three times (1.30 L d⁻¹, 1.62 L d⁻¹, and 2.08 L d⁻¹) to reduce the hydraulic retention time (HRT) and enhance biogas production. The volatile and total solids, chemical oxygen demand (COD), alkalinity, and biogas composition were measured over one year. The proposed system achieved 87.40% COD remotion from the feed stream and generated a yield of 507 mLCH₄ g_VS⁻¹, with an HRT of 19 days and an OLR of 4.27 gCOD L⁻¹ d⁻¹. The reactor produced biogas with a CH₄ content of 67.7%, CO₂ content of 18.1%, and H₂S content of 1413 ppm. This study highlights the effectiveness of the UASB reactor for biogas production using swine manure as a substrate.

The continued increase in human populations and use of chemical fertilizers remain a threat to the health and stability of human–ecological systems worldwide. To ameliorate this problem and achieve long-term food security, a variety of ecofriendly technologies have been developed, including the production of cyanobacteria-based biofertilizers. This technology can be optimized through experiments that assess how plant growth is enhanced under different biofertilizer concentrations (g L⁻¹). In this study, the biofertilizer capabilities of various concentrations of sonicated biomass (0, 2.5, 5, 10, 20, and 40 g L⁻¹) derived from the cyanobacteria Arthrospira maxima on the growth of basil (Ocimum basilicum, Lamiaceae) were assessed, comparing their effectiveness with that of a positive control, a commercial biofertilizer (OptiMar Algas Marinas^®) administered at 4 mL L⁻¹. Generally, increased concentrations led to enhanced growth parameters; however, discernible differences from the negative control (0 g L⁻¹) were often observed only when concentrations exceeded 5 g L⁻¹. Surprisingly, the negative and positive controls often yielded similar results. A chemical composition analysis of A. maxima revealed high concentrations of the phytohormones, macronutrients, and essential amino acids that likely explain how our A. maxima sample enhanced growth in basil. Further research is required to determine how other crop plants respond to different concentrations of A. maxima. Additionally, assessing the feasibility of creating an economically accessible product with a higher concentration of A. maxima is crucial for practical applications.

Cyanobacteria and microalgae represent promising sources for sustainable production of biofertilizers and biostimulants, which can improve crop yield and quality and contribute to food security. However, despite their potential, their exploration remains incomplete, hindered by technical and economic challenges that arise when attempting to scale up production. The primary focus of this review is to delve into the active chemical compounds responsible for the biofertilizing and biostimulating roles of cyanobacteria and microalgae. In addition, it explores the essential unit operations involved in transforming their biomass into potential bioproducts. Moreover, this review highlights studies that have employed cyanobacteria and microalgae as sources of biofertilizer in various crops, describing their mode of action and application. By integrating cyanobacteria and microalgae processing with other advanced biotechnological, the viability of these products for sustainable agriculture can be significantly enhanced.

Increasing energy demands around the globe require alternative sources of energy. Considering the large amount of agro-industrial and agriculture-related activities in Colombia, energy generation from biomass waste is a promising option to meet the energy needs of the country. Anaerobic digestion (AD) is a good alternative to use these wastes. In this study, several potential substrates for biogas generation using AD systems were identified through a literature review. Vinasses, palm oil industry residues, swine manure, coffee industry residues, and municipal solid wastes were found as potential substrates for AD. Considering factors such as composition, the amount of waste production, availability, and their relationship with important Colombian economic activities, three substrates were selected to perform biochemical methane potential (BMP) experiments. The selected substrates were swine manure (SM), palm oil mill effluent (POME), and coffee residues (CR). The obtained BMP values were 240, 465, and 314 NmLCH4/g VS, respectively. An analysis of kinetic parameters analysis was conducted for the BMP experiments, based on the logistic and Gompertz models. It was seen that the AD of SM starts faster than in the other evaluated substrates. Nevertheless, the overall methane production rate was the highest for POME, followed by CR. SM had the lowest methane production yield. The obtained values of BMP, kinetic parameters, and those collected during the literature review can be useful for the design and implementation of AD systems in Colombia. Moreover, attention should be paid to substrates such as POME, which have a high energy production potential.