Investigation of Combined Treatment Methods on Biogas Slurry (BGS) Concentration and Nutrient Recovery
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Date
2023-12
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Addis Ababa University
Abstract
Biogas slurry (BGS) is generated as byproduct during biogas production and can be used as organic fertilizer. However, Biogas slurry (BGS) application is limited due to its bulkiness and nutrient volatilization in the form of ammonia.
Hybrid treatment methods which include chemical treatment, physical separator and evaporation process were used to concentrate bulky biogas slurry. Principal nutrients (P, and NH4-N) distribution in solid and liquid fraction of BGS was examined after chemically treated with the addition of coagulant and flocculant and physical separations by using vibrating screen. The result showed that significant portion of readily available soluble ammonium (NH4-N) was presented in liquid fraction with distribution share of 91% and a significant amount of phosphorous, P (68.2%) found in solid fraction.
The influences of heating time (30, 45, and 60 minutes), heating temperature (65, 75 and 85 0C) and pH (7.76, 7 and 6) on water removal (WR) efficiency during evaporation of BGS liquid fraction was investigated. The highest WR efficiency (55%) was obtained at 75 oC, 45 minute and pH of 7. The effectiveness of NH4-N recovery was examined at different pH (6, 7 and 7.76) and maximum NH4-N (95.1% ) recovery were achieved at heating time of 45 min., temperature of 75 oC and pH of 6.
The final concentrate biogas slurry (CBGS) had a higher nutritional concentration and was less bulky than the raw biogas slurry. This effort helps to prevent the challenge faced associated with transporting of bulky BGS from biogas digester to application sites, reduce imported chemical fertilizer dependency and promote sustainable farming.
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Keywords
Biogas slurry, Energy security, Nutrient recovery, Agricultural productivity