Production of Moringa Biochar and Association with Vermicompost: A Sustainable Alternative for Soil Fertility, Soil Carbon Accumulation, and Elephant Grass Production for Bioenergy in the Semiarid Region

Purpose: This study evaluated the effects of Moringa (Moringa oleifera Lam.) biochar, applied alone or in combination with vermicompost and chemical fertilization, on soil fertility, soil organic carbon and its fractions, and the morphophysiological performance of elephant grass grown in sandy soil under semiarid conditions. Methods: Ten treatments with different proportions of chemical fertilizer, biochar, and vermicompost were tested in a completely randomized design with four replicates. Chemical analyses of the soil, quantification of soil carbon (SOC), labile carbon (LC), and particulate organic carbon (POC), evaluation of the plant's above-ground and root biomass, determination of photosynthetic pigments, and structural properties of the cell wall were conducted. Results: The biochar had a high carbon content (66.6%), an intermediate degree of aromaticity (H/C ratio = 0.66), moderate hydrophilicity (O/C ratio = 0.31), and a porous structure containing oxygenated functional groups identified by FTIR analysis. Treatments with biochar promoted increases in SOC content, labile fractions, as well as carbon management index (CMI) based on LC and POC, in addition to improving soil fertility. Significant gains were also observed in the biomass of the aerial and root parts of elephant grass, productivity, and lignin and cellulose contents, reinforcing its bioenergy potential. Conclusions: For practitioners in semiarid sandy soils, we recommend applying moringa biochar at the full tested rate (26.4 t ha-1) to maximize soil carbon accumulation, fertility, and elephant grass biomass yield. Alternatively, a blend of 75% biochar with 25% vermicompost provides comparable agronomic and environmental benefits, offering a cost-effective strategy to enhance soil resilience and reduce the land area required for CO₂ offset in degraded agricultural systems. Moringa biochar and mixtures were analyzed and their effect on elephant grass, carbon, and soil fertility was assessed. Biochar and vermicompost intensify chlorophyll, cellulose, and lignin, increasing physiological vigor. Systems with biochar increased soil fertility and soil carbon accumulation. Mixtures with biochar achieved higher yields of elephant grass aerial parts. Biochar reduces the amount of planted area needed to offset CO2 emissions.