Most people in rural sub-Saharan Africa lack access to electricity and rely on traditional, inefficient, and polluting cooking solutions that have adverse impacts on both human health and the environment. Here, we propose a novel integrated agroforestry-bioenergy system that combines sustainable biomass production in sequential agroforestry systems with biomass-based cleaner cooking solutions and rural electricity production in small-scale combined heat and power plants and estimate the biophysical system outcomes. Despite conservative assumptions, we demonstrate that on-farm biomass production can cover the household’s fuelwood demand for cooking and still generate a surplus of woody biomass for electricity production via gasification. Agroforestry and biochar soil amendments should increase agricultural productivity and food security. In addition to enhanced energy security, the proposed system should also contribute to improving cooking conditions and health, enhancing soil fertility and food security, climate change mitigation, gender equality, and rural poverty reduction.

Biochar (B) has low nutrient content and is recalcitrant to biodegradation. Supplementing B with a fast-releasing nutrient source may improve soil fertility and physical conditions and increase crop productivity. A three-season field study was conducted on sandy loam and sandy clay loam textured soils to investigate the effect of B mixed with livestock manure (LM) on soil properties (pH, organic carbon (OC), cation exchange capacity (CEC), total Nitrogen (TN), available Phosphorus (Avail P)), and French bean yield (Phaseolus vulgaris L.) in Rwanda. The study used a factorial randomized block design with four replications. Treatments comprised three levels of B (0, 1, and 3 t/ha) and three levels of LM (0, 1, and 3 t/ha). Biochar was used from S. sesban, G. sepium, A. angustissima, Eucalyptus, and Grevillea sp., prepared using a drum kiln, while LM was prepared using the pit method. The Analysis of Variance (ANOVA), Tukey (HSD) function at p < 0.05, and linear mixed-effects model were performed in R software version 4.3.3 (R Core Team, 2024). The analysis showed that the treated plots significantly increased French bean yield compared to the control plots, with the highest value found in plots treated with 3 t/ha. The combined plots showed an increased yield compared to sole Biochar or manure. The seasonal increase has been observed, with percentage increases recorded as follows: 16%, 33.56%, 173.06% in sole B plots; 40.28%, 14.43%, and 11.76% in sole LM plots and 125%, 156%, and 209.8% in B + LM plots for season 1, 2, and 3, respectively. Furthermore, the results indicated that the application of B alone or combined with LM significantly enhanced soil pH, OC, TN, avail P, and CEC with the pH ranging from 6.77 to 5.43 for B alone, 6.7–5.35 for LM alone, 8.53–6.06 for B-LM plots, and 4.34–3.78 for control plots. Applying Biochar, either alone or in combination with LM, at a low rate demonstrated positive effects on French bean yield and soil nutrients in smallholder farmers. This study encourages using natural materials such as B and LM to improve soil fertility and increase vegetable production while reducing chemical fertilizers that can cause pollution and damage the environment.

Biochar (B) in combination with organic manure could improve the biochar efficacity in improving soil functions related to hydrophysical properties. Short-term field experiments were conducted with three levels of B and livestock manure (LM) (0, 1, and 3 tons/hectare (t/ha)) to assess its effect on physical properties of soils such as bulk density (BD), soil porosity (SP) and aggregate stability (AS), along with soil hydro properties, including field capacity, permanent wilting point (PWP), Plant available water (PAW), and hydraulic conductivity (Ksat). Each treatment was replicated four times in a factorial randomised block design (RBD) using French beans as a test crop in sandy soils and sandy clay loam-textured soils in Rwanda. The data were analysed using analysis of variance (ANOVA) together with the Duncan test at P < 0.05 using R Studio. The findings demonstrated that the co-application of B and LM at varying application rates significantly (P < 0.05) reduced soil bulk density (BD), with the lowest BD observed at the highest application rate (3t/ha). Additionally, the results indicated that the combined application of B and LM at lower rates significantly affected soil water retention characteristics, including permanent wilting point (PWP), field capacity (FC), and saturated hydraulic conductivity (Ksat). The improvements in these properties became more pronounced with increasing B rates when mixed with LM. These results contribute to a better understanding of soil water dynamics following B and LM applications and suggest a promising approach to mitigating water loss, especially in sandy soils.