The IFAD Regional Cassava Processing and Marketing Initiative    THE USE  OF CASSAVA WASTES TO PRODUCE BIO-ENERGY:  OUTCO...
INTRODUCTION
The question Can cassava wastes and other available biowastes be profitably converted into bio-energy by utilizing existin...
Why this study? Local availability of bio-masses : In Ghana >11 million/MT/year of cassava roots are produced (2008, FA...
CASSAVA PEELS AND WASTEWATERS POLLUTE THE ENVIRONMENT
Gasification Blend of biomasses ↓ Blend of gases (“producer gas”) ↓ Electricity (mainly)   +  Heat (hot/cold air) AVAILABL...
THE GASIFICATION PROCESS (THE GASIFIER )
   Several biomasses are being successfully utilized as feedstock for  gasification:  wood chips; coconut shell; bamboo; ...
GASIFICATION: BLEND OF DRIED CASSAVA AND  WOOD WASTES/OTHER BIOMASSES (2) Blend of wood shaving (70%) +saw dust (30%) (1) ...
SCHEME OF A GASIFIER/REACTOR  Gasifier:  a reactor where physical and chemical processes take place
Main assumptions Installed capacity :  120   Kw  (though on market they are available from  5  to  2200 kW ) Working hours...
BIO-METHANATION/BIOGAS PLANT: FLOW DIAGRAM
THE METHANIZATION PROCESS  (BIO-GAS PLANT)
BIOGAS: ANAEROBIC FERMENTATION/BIO-DIGESTION PROCESS Main features digestor Installed capacity  available on market for  d...
BIO-METHANATION/BIOGAS PLANT: FLOW DIAGRAM
THE FINANCIAL ANALYSES
Energy production/planned use  based on a  gasifier  with an installed capacity of  120 kWe/h ************ Option 1 (Gener...
Estimated quantity of wastewaters generated during cassava processing (to produce: gari, flour, agbelima): 1 liter water r...
Heat required for drying  target bio-masses ( peels/barks and wood wastes ): Kcal/d 3,388,000 Heat required for drying 4.5...
GASIFIER: PRODUCTION AND USE OF ENERGY
GASIFICATION AND BIOGAS MARKETABLE PRODUCTION: HEAT BALANCE  AND EQUIVALENCE PER DAY OF 22 WORKING HOURS
ECONOMIC AND FINANCIAL ANALYSES:  KEY ASSUMPTIONS Project’s life: 10 years Plants working 22h/d for 330 d/y Costs Financin...
THE CASH FLOW ANALYSIS:  THE GASIFIER
THE CASH FLOW ANALYSIS The biogas plant The gasifier plant in the Asueyi municipality
ENVIRONMENTAL ASPECTS Water resulting from bio-gas plant Air resulting from gasifier Wood is saved and forests are less at...
ENVIRONMENTAL ASPECTS
Thank you
Session 5.1 Potential use of Cassava Wastes to Produce Energy: Outcomes of a Feasibility Study in Ghana by Serpagli, IFAD
Session 5.1 Potential use of Cassava Wastes to Produce Energy: Outcomes of a Feasibility Study in Ghana by Serpagli, IFAD
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Session 5.1 Potential use of Cassava Wastes to Produce Energy: Outcomes of a Feasibility Study in Ghana by Serpagli, IFAD

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Session 5.1 Potential use of Cassava Wastes to Produce Energy: Outcomes of a Feasibility Study in Ghana by Serpagli, IFAD

  1. 1. The IFAD Regional Cassava Processing and Marketing Initiative  THE USE OF CASSAVA WASTES TO PRODUCE BIO-ENERGY: OUTCOMES OF A FEASIBILITY STUDY IMPLEMENTED IN GHANA 18-19 October 2010 IFAD - RTIMP, Ghana What has been done and what can be done
  2. 2. INTRODUCTION
  3. 3. The question Can cassava wastes and other available biowastes be profitably converted into bio-energy by utilizing existing technology? THE USE OF CASSAVA WASTES TO PRODUCE ENERGY: OUTCOMES OF A FEASIBILITY STUDY IMPLEMENTED IN GHANA
  4. 4. Why this study? Local availability of bio-masses : In Ghana >11 million/MT/year of cassava roots are produced (2008, FAO). Out of them, 2,2 million MT are either peels (13%) or roots unfit for processing (6-7%). Other bio-masses (from wood) also easily available in large quantities (wood shavings/saw dust) Cassava wastes (peels, barks, effluents): Have no market value ; It is a financial cost to dispose them off; Serious environmental hazard : pollute soils, table waters, air; Health hazard for this industry’s workers ( social cost ) HOW TO TURN A COST INTO A PROFIT
  5. 5. CASSAVA PEELS AND WASTEWATERS POLLUTE THE ENVIRONMENT
  6. 6. Gasification Blend of biomasses ↓ Blend of gases (“producer gas”) ↓ Electricity (mainly) + Heat (hot/cold air) AVAILABLE TECHNOLOGIES: PRODUCTION OF BIO-ENERGY FROM WASTES Bio-methanation (biogas) Wastewaters ↓ Methane ↓ Heat (mainly)
  7. 7. THE GASIFICATION PROCESS (THE GASIFIER )
  8. 8.  Several biomasses are being successfully utilized as feedstock for gasification: wood chips; coconut shell; bamboo; maize stalks; cotton stalks; rice husk; bagasse; groundnut shells; tea and coffee wastes; corn cobs; cashew nut shell, etc.  Lack of data on suitability of cassava wastes and wood wastes required implementation of proximate laboratory analyses          BIOMASS SUITABLE FOR GASIFICATION Outcomes of laboratory analyses Cassava peels/barks: ash content (<5%) ash fusion temperature is above 1200°C bulk density remains above 250 even after drying it flows easily and burns well moisture content (66%) to be reduced up to 20% Wood shavings and sawdust: ash content (<5%) ash fusion temperature above 1200°C bulk density is low and it does not flow easily but burns well moisture content (30%) to be reduced up to 20% A blend of cassava and wood wastes (mixed in a 1:1 proportion) showed to be suitable for gasification.
  9. 9. GASIFICATION: BLEND OF DRIED CASSAVA AND WOOD WASTES/OTHER BIOMASSES (2) Blend of wood shaving (70%) +saw dust (30%) (1) Dried cassava peels/barks Gasifier uses a blend of + (2) mixed in a 1:1 proportion
  10. 10. SCHEME OF A GASIFIER/REACTOR Gasifier: a reactor where physical and chemical processes take place
  11. 11. Main assumptions Installed capacity : 120 Kw (though on market they are available from 5 to 2200 kW ) Working hours: 330 days/year * 22 hours/day Main outputs: c.1 Electricity (mostly): to be sold as such or used to operate equipments, dry food cassava derivatives, lightening etc c.2 Heat: to dry biomasses (20% moisture content) as feedstock for the gasifier and to dry food cassava derivatives MAIN FEATURES OF THE GASIFIER CONSIDERED IN THE STUDY Intakes d.1 Intake (MT/year) of raw cassava peels/ barks (66% moisture content): 1706 MT/year (equal to 8280 MT/year cassava roots) d.2 Intake (MT/year) of raw wood shaves and sawdust (30% moisture content): 835 MT/year d.3 Intake (MT/year) of dried (20% moisture content) biomasses (1:1 proportion): MT 1452 , of which: Dried cassava peels/barks: MT 726 Wood shaves and sawdust: MT 726
  12. 12. BIO-METHANATION/BIOGAS PLANT: FLOW DIAGRAM
  13. 13. THE METHANIZATION PROCESS (BIO-GAS PLANT)
  14. 14. BIOGAS: ANAEROBIC FERMENTATION/BIO-DIGESTION PROCESS Main features digestor Installed capacity available on market for digestors : designed according to users’ needs Main product: biogas (methane, mainly) from wastewaters through an anaerobic fermentation. Digestion time: ~ 16 – 120 hours Wastewaters solids contents: Dissolved solids ~ 1-10% Suspended solids: < 3% Output: 1 lt/wastewaters = 2 to 3.5 lt of biogas (according to organic load of wastewaters) Laboratory Analyses of cassava processing wastewaters Total solids : 4,000 – 6,600 mg/L Total suspended solids : 1,450 mg/L Total volatile solids : 2,000 mg/L pH : 5.14 BOD : 3,400 – 6,018 mg/L COD : 3,870 – 6,680 mg/L Free Sugars: 640 – 2,075 mg/L Nitrogen : 65 – 74 mg/L
  15. 15. BIO-METHANATION/BIOGAS PLANT: FLOW DIAGRAM
  16. 16. THE FINANCIAL ANALYSES
  17. 17. Energy production/planned use based on a gasifier with an installed capacity of 120 kWe/h ************ Option 1 (General case) 1.a) Output: electricity ( as main output) + hot air; 1.b) Planned use: 88 Kw/h of electricity (to be sold on open market) + hot air (to dry target biomasses up to a 20% moisture content) ************* Option 2 (Application – Asueyi pilot) 2.a) Output: electricity + hot air; 2.b) Planned use: 74 Kw/h of electricity (to operate equipments etc) + hot air (to dry target biomasses up to a 20% moisture content and 4.5 tons/22h of cassava food products up to a 8-10% moisture content-from initial 40%) GASIFICATION: ENERGY OUTPUT AND ITS PLANNED USE
  18. 18. Estimated quantity of wastewaters generated during cassava processing (to produce: gari, flour, agbelima): 1 liter water required to process 1 kg of peeled cassava roots Estimated wastewater: 18,000 liters/day (from 25 T/d of roots) Wastewater organic load: 3400-6000 mg/liter as BOD Biogas potential: in 24-72 hours about 37-56 m³/h of biogas are produced digesting ~80% of BOD in wastewaters Methane concentration in biogas: 65-70% Calorific value methane: 5800-7200 kcal/m 3 Estimated energy production: Gross output 334,425 Kcal/d Net output 301,513 Kcal/d BIOGAS PLANT: ESTIMATED ENERGY PRODUCTION
  19. 19. Heat required for drying target bio-masses ( peels/barks and wood wastes ): Kcal/d 3,388,000 Heat required for drying 4.5 tons/day of cassava derivatives ( flour, starch, agbelima ) from initial 40%-45% to final 8%-10% moisture content: Kcal/d 2,156,000 HEAT REQUIREMENT TO DRY BIOMASS AND PRODUCTS IN A DAY OF 22 WORKING HOURS
  20. 20. GASIFIER: PRODUCTION AND USE OF ENERGY
  21. 21. GASIFICATION AND BIOGAS MARKETABLE PRODUCTION: HEAT BALANCE AND EQUIVALENCE PER DAY OF 22 WORKING HOURS
  22. 22. ECONOMIC AND FINANCIAL ANALYSES: KEY ASSUMPTIONS Project’s life: 10 years Plants working 22h/d for 330 d/y Costs Financing of the investment: 100% loan (22% interest rate), including 4 months working capital Repayment of loan: yearly equal installments for 7 years Transport Costs: $10/MT for local biomasses Bio-diesel fuel used to operate biogas & gasifier plants Revenues Incomes: total energy (electricity plus heat) generated by the gasifier and the biogas plants - expressed into Kwh and Kcal- converted into liters of diesel (0.8$/lt) and tons of firewood (15 $/Mt) . Discount factor of annual cash flows: 22%
  23. 23. THE CASH FLOW ANALYSIS: THE GASIFIER
  24. 24. THE CASH FLOW ANALYSIS The biogas plant The gasifier plant in the Asueyi municipality
  25. 25. ENVIRONMENTAL ASPECTS Water resulting from bio-gas plant Air resulting from gasifier Wood is saved and forests are less at risk Used in re-circulation mode with zero discharge. Occasional ph adjustment and simple treatment may be needed. Gasifier releases negligible amounts of gases into the atmosphere. Combustion is much cleaner as compared to the one for liquid fuels. Heat produced by the gasifier replace heat generated by firewood
  26. 26. ENVIRONMENTAL ASPECTS
  27. 27. Thank you

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