Lec # 03- Typology of biogas production process- Environment and Operating parameters.pptx

This lecture presents the various typologies of biogas production

1. REET3101: Biogas and Technology Systems Prof Asoh D. A Department of Renewable Energy HTTTC Dr. Jerome Ndam MUNGWE Department of Renewable Energy HTTTC REET3101: Biogas and Technology systems Prof Asoh D A/ Dr J.N. Mungwe 2024/2025

2. Typology of biogas production Environmental condition in the digester Digester operating parameters Performance parameters REET3101: Biogas and Technology systems Prof Asoh D A/ Dr J.N. Mungwe 2024/2025

3. Typology of biogas production Environmental condition in the digester REET3101: Biogas and Technology systems Prof Asoh D A/ Dr J.N. Mungwe 2024/2025

4. Typology of biogas production: Environmental condition in the digester REET3101: Biogas and Technology systems Prof Asoh D A/ Dr J.N. Mungwe 2024/2025 Oxygen Methanogenic archaea: killed by small quantities of O 2 Some known as facultative anaerobic bacteria coexist with O 2 consuming bacteria Temperature Rate of biological decomposition and process increases partially with increase in ambient temperatures Different microorganisms have different optimum temperature Temperature below/above optimum relevant microorganisms may be inhibited or may suffer irrevocable damage Psycrophilic ( below 20°C) Mesophilic ( 20 -40°C) Thermophilic ( 45 – 70°C) pH Value Microorganisms involve in the various stages require different pH value for optimum growth Hydrolytic/Acidogenic bateria: 5.2 <pH<6.3 ( acid medium) Acetogenic/Methanogenic bacteria: 6.5<pH< 8.0 (neutral)- absolutely essential In single stage digesters neutral pH range must be maintained pH value is of only limited use for digester control, however, b/c of its importance should be always measures

5. Typology of biogas production: Environmental condition in the digester REET3101: Biogas and Technology systems Prof Asoh D A/ Dr J.N. Mungwe 2024/2025 Nutrients supply species-specific needs in terms of macronutrients, micronutrients and vitamins Rate of growth and activity of various population affected by nutrient supply Optimum nutrients must be ensured for optimal methane production. Methane production depends on proportions of proteins, fats and carbohydrates Balance of macronutrients/micronutrients required for process stable. High C: inadequate metabolism i.e. Less C is converted High N: formation of NH3, inhibit growth of bacteria or complete collapse of bateria population. C:N ratio of the substrate is crucial optimal range 10 -30:1 Phosphorus and Sulphur also require C:N:P:S ratio should be 600:15:5:3 Micronutrients required: cobalt (Co), nickel (Ni), Selenium (Se), molybdenum (Mo)- needed in co-factors for essential reactions Magnessium (Mg) Iron (Fe), Maganese (Mn)- electron transport and function of some enzymes Concentration of micronutrients in a digester is a crucial reference variable

6. Typology of biogas production: Environmental condition in the digester REET3101: Biogas and Technology systems Prof Asoh D A/ Dr J.N. Mungwe 2024/2025 Recommended micronutrients concentration

7. Typology of biogas production: Environmental condition in the digester REET3101: Biogas and Technology systems Prof Asoh D A/ Dr J.N. Mungwe 2024/2025 Inhibitors Substances which under certain circumstances can lower the process rate or in toxic concentration bring process to a stop! May be present in digester in two pathways: Feed of the digester Antibiotics, disinfectants, solvent, herbicides, salts, heavy metals (e.g. Copper) Intermediate products from individual stage of the process Free ammonia (NH 3 NH 4 + + OH - ) [ pH value & Temperature] Hydrogen Sulphide (H 2 S)- undissociate, dessolve form [increase /decrease pH] Volatile Fatty Acids (VFA) Oxygen (O 2 )

8. Typology of biogas production: Environmental condition in the digester REET3101: Biogas and Technology systems Prof Asoh D A/ Dr J.N. Mungwe 2024/2025

9. Typology of biogas production : Digester operating parameters REET3101: Biogas and Technology systems Prof Asoh D A/ Dr J.N. Mungwe 2024/2025

10. Typology of biogas production : Digester operating parameters REET3101: Biogas and Technology systems Prof Asoh D A/ Dr J.N. Mungwe 2024/2025 Organic Loading Rates (OLR) &Hydraulic Retention Time (HRT) Economic consideration are often the basis for the design & construction of digesters Focus NOT on maximum gas yield or complete decomposition of Organic Matter (OM) Aim: to obtain optimum degradation performance at acceptable economic cost OLR Kg volatile solids (OM) fed into the digester per m 3 of working volume per unit of time [kgVS/(m 3 .d)] OLR = dm/dt . C/V d .100 [kgVSm -3 d -1 ] dm/dt = amount of substrate added per unit time [kg/d] C = concentration of OM (VS) [%VS] V d = digester Volume [m 3 ] HRT = V d /(dV/dt) [d] V d = digester Volume [m 3 ] dV/dt = volume of substrate added daily [m 3 /d] HRT must be chosen so that constant replacement of digester content does not flush out more microorganisms than can be replenished during that time. E.g methanogenic archaea: 10days

11. Typology of biogas production : Digester operating parameters REET3101: Biogas and Technology systems Prof Asoh D A/ Dr J.N. Mungwe 2024/2025

12. Typology of biogas production : Digester operating parameters REET3101: Biogas and Technology systems Prof Asoh D A/ Dr J.N. Mungwe 2024/2025 Mixing (Agitation of digester content) Density difference: layer formation Bulk of bacterial mass collects at in lower layer Substrate in upper layer Floating of solids to form a scum Provide intensive contact between bacteria and substrate/feedstock Release of biogas Achieved in several ways Mechnical: propellers, scrapers etc Component configuration

13. Typology of biogas production : Digester operating parameters REET3101: Biogas and Technology systems Prof Asoh D A/ Dr J.N. Mungwe 2024/2025 Temperature operating range Psychropilic (0 -20°C) Mesophilic (20-45°C) Thermophilic (40 -60°C)

14. Typology of biogas production Performance Parameters REET3101: Biogas and Technology systems Prof Asoh D A/ Dr J.N. Mungwe 2024/2025

15. Typology of biogas production : Performance Parameters REET3101: Biogas and Technology systems Prof Asoh D A/ Dr J.N. Mungwe 2024/2025 Biogas Production (P) m 3 of biogas [methane] produce per unit of time Nm 3 /day Biogas Productivity Biogas produced per unit of time per unit digester volume Specific Biogas Productivity [ Yield] Biogas produce per unit of time ÷ amount of OM added per unit of time Denotes the effieciency of biogas production from loaded substrate Little informative value as individual parameters b/c do not include effective loading of the digester Coupled with OLR to make more sense

16. Typology of biogas production : Performance Parameters REET3101: Biogas and Technology systems Prof Asoh D A/ Dr J.N. Mungwe 2024/2025 Degree of Degradation ( η VS ) Provides information about the efficiency with which the substrate is converted May be determine on the basis of VS or Chemical Oxygen Demand (COD) On basis of VS is advised

17. REET3101: Biogas and Technology systems Prof Asoh D A/ Dr J.N. Mungwe 2024/2025 END