Co-designing sustainable biochar business models with sub-Saharan African communities for inclusive socio-economic transformation.

Smallholder farmers in sub-Saharan Africa (SSA) encounter multiple livelihood challenges. Embracing circular bioeconomy principles, particularly considering agricultural and food processing residues, could enable inclusive, locally led, sustainable development pathways within rural communities. Biochar products are one such example of a bio-based material that can be generated using circular principles and deployed for sustainable community development, including among smallholder farmers. This research leverages empirical evidence from four SSA regions to explore the potential of inclusive and sustainable biochar business models, namely: (i) Northern Region, Ghana, (ii) Yamoussoukro, Côte d'Ivoire, (iii) Casamance, Senegal, and (iv) Western Region, Uganda. Co-creation workshops using the Triple-Layered Business Model Canvas framework were carried out in each region with local stakeholders to evaluate the social, ecological, and economic implications of four locally relevant biochar applications: water filtration, biogas purification, soil amendment, and cooking fuel briquettes. Data was analysed at an aggregate level for all regions and applications. The study describes this consolidated biochar business model and examines the implications for SSA communities. The resulting sustainable bio-based business model can guide value chain actors and policymakers in SSA communities towards rural sustainable development with a better understanding of the needs, opportunities, challenges, and impacts of biochar-based value chain development.

Adoption of novel climate-smart farming systems for enhanced carbon stock and carbon dioxide equivalent emission reduction in cattle corridor areas of Uganda.

Climate change remains the single major threat to the realization of increased livestock production because of its impact on the quantity and quality of feed crops and forages, water availability, animal reproduction, and biodiversity. To minimize the negative impacts of climate change on livestock, an agroforestry project was implemented in the cattle corridor areas of Uganda. Predominant agroforestry tree species and improved grass were planted. At the age of 1.5 years, the aboveground biomass, aboveground carbon stock, and carbon dioxide equivalent emissions sequestrated by each sapling species strand and grass species were determined. From the results, the aboveground biomass (F = 92.21, p = 0.020), aboveground carbon stock (F = 101.01, p = 0.035), and the carbon dioxide equivalent emissions sequestrated (F = 71.02, p = 0.0401) varied significantly among the studied species. Among the agroforestry saplings, Calliandra callothyrus (10.0 ± 0.7 ton/acre) had the highest aboveground biomass, while Markhamia lutea (4.3 ± 0.3 tons/acre) and Albizia chinense (4.1 ± 0.2 tons/acre) had the lowest aboveground biomass. Similarly, the aboveground carbon stock was the highest in Calliandra callothyrus strand (4.70 ± 0.1 tons/acre) and lowest in the Albizia chinense strand (1.94 ± 0.2 tons/acre). At a strand level, Calliandra callothyrus (17 ± 0.4 ton/acre) sequestrated the highest quantities of carbon dioxide equivalent emissions, followed by Maesopsis eminii (10 ± 0.2 ton/acre) and Grevillea robusta (9 ± 0.5 ton/acre) species strands. Markhamia lutea (7 ± 0.2 ton/acre) and Albizia Chinense (7 ± 0.1 ton/acre) strands sequestrated the lowest quantities of carbon dioxide equivalent emissions. At the age of 1.5 years, the grass species were fully grown but only stored 0.51 ± 0.0 and 0.47 ± 0.0 tons/acre of Aboveground carbon for Chloris gayana and Centrosema pubescens, respectively. The carbon dioxide equivalent emissions sequestrated by the grass: Chloris gayana (1.9 ± 0.0 ton/acre) and Centrosema pubescens (1.7 ± 0.0 ton/acre) were also less than that of the agroforestry saplings. From this study, the agroforestry species with higher wood biomass and fast growth rate are recommended for carbon dioxide emission sequestration.

Water use efficiency, grain yield, and economic benefits of common beans (Phaseolus vulgaris L.) under four soil tillage systems in Mukono District, Uganda.

With the increasing climate change impacts and variabilities, water is becoming a limiting factor for rainfed crop production in Uganda. Conservation tillage practices could improve soil and water conservation in croplands. Field experiments were conducted for three consecutive seasons from April 2019 to June 2020. The experiments evaluated the effect of soil tillage treatments on soil water storage, water use efficiency, grain yield, and economic benefits of the common beans (Phaseolus vulgaris L.) in two sub-counties of Mukono District, central Uganda. The soil tillage treatments were: no-tillage, stubble-mulching, deep tillage, and conventional tillage. The no-tillage and stubble-mulching improved soil water storage by 46 and 45%, respectively, compared with the conventional tillage in the 0-100 cm soil depth over the 14 months. Soil tillage treatments significantly (p < 0.05) affected the water use efficiency, with water use efficiency values generally higher under no-tillage and stubble-mulching than under deep tillage and conventional tillage treatments. The grain yield was highest under no-tillage and stubble-mulching than deep tillage and conventional tillage treatments, with over 5, 38, and 43% higher grain yield under no-tillage than under stubble-mulching, deep tillage, and conventional tillage treatments, respectively. Although no-tillage and stubble-mulching improved soil water storage and grain yield, seasonal precipitation distribution had a greater influence on the final grain yield, soil water storage, and water use efficiency. The net profit was 3 and 5 times higher under no-tillage than under conventional tillage and deep tillage treatments, respectively. The overall results showed that no-tillage and stubble-mulching were the optimum tillage treatments for increasing soil water storage and common bean yield, enhancing water use efficiency, and improving economic returns in central Uganda.

Effect of tillage systems and tillage direction on soil hydrological properties and soil suspended particle concentration in arable land in Uganda.

The 2030 Agenda for Sustainable Development addressing the issues of environmental degradation has been challenged by human developments and activities. Crop production systems and technologies (e.g. soil tillage) are among the leading factors causing environmental degradation. In this study, the effect of soil tillage systems (i.e. no-tillage (NT); stubble-mulching (SM); deep tillage (DT); and conventional tillage (CT)) on surface runoff volume (SRV), suspended sediment concentration (SSC), infiltration rate (IR), and soil moisture content (SMC) in the common bean (Phaseolus vulgaris L.) farms, Mukono District, Uganda was evaluated. The effect of soil tillage direction on SRV was also assessed. The SRV, SSC, IR, and SMC were monitored under Complete Randomized Block Design (CRBD) experiments with four soil tillage systems in Goma and Kimenyedde experimental sites during two wet seasons. The results showed that SRV, SSC, IR, and SMC were significantly (p < 0.05) influenced by the soil tillage system, season, and site. The highest total SRV was observed during the first season in Goma experimental site under CT with soil tillage along the slope (1071.3 mm). The lowest SRV was observed during the second season in Kimenyedde experimental site under NT (165.0 mm). The highest and lowest mean SSC was observed in the CT (2.41 ± 0.3 g L-1) in Goma experimental site during the first season and NT (0.43 ± 0.1 g L-1) in Kimenyedde experimental site during the second season, respectively. The SSL was highest under CT in both Goma (147.17 kg ha-1season-1) and Kimenyedde (114.93 kg ha-1season-1), and lowest under NT with the means of 11.25 and 9.19 kg ha-1season-1 in Goma and Kimenyedde experimental sites, respectively. Both SRV and SSC increased linearly with both rainfall amount (RF) and rainfall intensity at 10 min (RI10). The highest and lowest IR and SMC were observed in the NT and CT treatments, respectively. No significant (p > 0.05) variations were observed in the SMC under the NT and SM treatments. Overall, soil tillage systems, soil type, and rainfall characteristics are among the key factors influencing the magnitudes of SRV and SSC in both time and space. This particular study suggests that NT and SM would help reduce the magnitudes of SRV and SSC, in agricultural fields.