The Effect of pH Variation in Biogas Production: Impact of Cocoa Pods and Empty Palmyra Palm Bunches.

The main purpose of this work was to assess the influence of pH variation in biogas production and to study the effect of certain substrates (other than chemical products) on stabilizing production. Two substrates were used in production: banana peels (BP) and rumen scraps (RS). Five different mixing ratios were studied at a mesophilic temperature (35±2 °C): 25% RS+75% BP; 100% RS; 100% BP; 50% RS+50% BP and lastly 75% RS+25% BP. Substrate characterization parameters such as dry matter content, volatile dry matter content, pH, nitrogen-carbon ratio, biogas production and methane content were determined. A comparative study of the pH stabilization was then conducted using the mixtures (co-digestion) that obtained the best production results. Stabilizers included in particular potassium hydroxide (KOH), cocoa pods and empty Palmyra palm bunches. Biogas production varies with pH fluctuation. Indeed, it decreases whenever the pH value tends towards acidity. The best production was obtained at a pH of between 7.1 and 7.5. The use of cocoa pods as a pH stabilizer instead of KOH (chemical product) improved production by 24.48% and 0.11%, respectively, for the mixtures of 50% RS+50% BP and 25% RS+75% BP. Compared to KOH, empty Palmyra palm bunches had no positive impact. The findings showed that cocoa pods made it possible to stabilize the pH fluctuation and thus improve production performance. This improvement showed that cocoa pods could be used as a new stabilizer in anaerobic digestion systems. [ABSTRACT FROM AUTHOR]