Optimization of biochar production from Rumex abyssinicus using response surface methodology and its application in amending degraded soil.

Abstract

Soil degradation is a major constraint to agricultural productivity in Ethiopia, particularly in highland regions where erosion, acidity, and nutrient depletion are widespread. Although biochar has shown promise in restoring soil health, its effectiveness depends heavily on feedstock type and production conditions. Rumex abyssinicus, a culturally significant and abundant Ethiopian plant, has been studied for activated carbon but not for biochar synthesis or soil rehabilitation using stem biomass. This study addresses that gap by optimizing biochar production from Rumex. abyssinicus stems using response surface methodology (RSM), and evaluating its impact on degraded soil. Pyrolysis parameters: temperature, time, heating rate, and particle size, were optimized to maximize yield, achieving 31.98% under ideal conditions. The resulting biochar exhibited high fixed carbon (78.8%), large surface area (455.1 m²/g), and favorable properties including pHpzc (9.2), WHC (5.56 g/g), and CEC (15 meq/100 g). A 100-day pot experiment using soil from Wolayta showed significant improvements in bulk density (- 49.24%), porosity (+ 81.47%), pH (+ 24.57%), and organic matter (+ 531.33%). Statistical analysis confirmed treatment effects across key parameters. These findings demonstrate that Rumex abyssinicus biochar is a viable, locally sourced amendment for degraded soils. Its use is recommended for sustainable land restoration and climate-resilient agriculture in Ethiopia.