There is still a need to develop scenarios and models aimed at substituting fuelwood and reducing the use of fossil fuels such as liquefied petroleum gas (LPG), on which low-income rural households in the Global South often depend. The use of these fuels for cooking and heating in domestic and productive activities poses significant health and environmental risks. This study validated, in three different phases, the sustainability of a model for the production and use of biogas from the treatment of swine-rearing wastewater (WWs) on a community farm: (i) A Multi-Criteria Analysis (MCA), incorporating environmental, social/health, technical, and economic criteria, identified the main weighted criterion to C8 (use of small-scale technologies and low-cost access), with a score of 0.44 points, as well as the Tubular biodigester (Tb) as the most suitable option for the study area, scoring 8.1 points. (ii) Monitoring of the Tb over 90 days showed an average biogas production of 2.6 m³ d⁻¹, with average correlation 0.21 m³ Biogas kg Biomass⁻¹. Using the experimental biogas production rate (k = 0.0512 d⁻¹), the process was simulated with the BgMod model, achieving an average deviation of only 10.4% during the final production phase. (iii) The quantification of benefits demonstrated significant reductions in firewood use: in Scenario S1 (kitchen energy needs), biogas replaced 83.1% of firewood, while in Scenario S2 (citronella essential oil production), the substitution rate was 24.1%. In both cases, the avoided emissions amounted to 0.52 tons of CO_2eq per month. Finally, this study proposes a synthesised, community-based rural biogas framework designed for replication in regions with similar socio-environmental, technical, and economic conditions.

The estimation of biophysical variables, such as the Leaf Area Index (LAI), using remote sensing techniques, is still the subject of numerous studies, since these variables allow obtaining valuable information on the vegetation status. In this work, we estimate LAI from multiangular PROBA/CHRIS images, by analyzing the reflectance measured in its 5 observation angles, for the bands centered in 665 and 705 nm. These wavelengths correspond to the chlorophyll absorption band and the Red-Edge region, respectively. The Normalized Difference Index (NDI) calculated from this wavelengths, shows good correlation with LAI and allows its remote sensing estimation and its applicability to the recently launched ESA Sentinel 2, thanks to its new bands in the Red-Edge. This research analyzed the influence on the acquisition geometry in the NDI, calibrating the relationship between this index and the LAI for each of the five observation angles in the PROBA / CHRIS images. As a result, we have obtained a relationship capable of providing LAI from the viewing angle and the NDI index.

The use of non-conventional systems for domestic wastewater management has gained attention in rural areas of the Global South, where centralised infrastructure is often limited. This study presents the design, construction, and pilot-scale evaluation of a solar still unit operated under passive and photovoltaic-assisted active modes as a separation and polishing component for domestic wastewater from a rural site in Barrancabermeja, Colombia. Performance was assessed through physicochemical and microbiological characterisation of influent wastewater and treated condensate, together with hourly monitoring of distillate production, water temperature, glass-cover temperature, and ambient conditions. Under passive operation, a theoretical distillation model was applied, empirically adjusted, and evaluated using MAE, RMSE, MAPE, and R². Under the tested conditions, indicative within-mode reductions reached 80.9% and 89.3% for chemical oxygen demand (COD), 95.6% and 93.8% for biochemical oxygen demand (BOD₅), and 94.0% and 94.4% for total suspended solids (TSS) under passive and active modes, respectively. Microbial indicators showed minimum estimated reductions above 99.9%, with faecal coliforms reduced to very low levels in passive mode and not detected in the analysed active-mode condensate sample. Maximum daily condensate production reached 1.445 L m⁻² day⁻¹ in passive mode and 2.262 L m⁻² day⁻¹ in active mode, confirming the low-flow nature of the unit. Approximately 50% of daily production occurred between 12:00 and 15:00 h. The model reproduced the main diurnal production pattern, although empirical correction was required. Overall, the unit may improve condensate quality under pilot-scale conditions and shows potential as a polishing component within decentralised, low-flow treatment trains.