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Waste management: Appropriate technologies for developing countries

Waste management: Appropriate technologies for developing countries. (Ethiopia’s case). Objective of the lecture Introduction to the nature of the waste in cities and rural areas in the developing countries; Highlight on available waste managements practices;

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Waste management: Appropriate technologies for developing countries

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  1. Waste management: Appropriate technologies for developing countries (Ethiopia’s case) AAiT/AAU

  2. Objective of the lecture • Introduction to the nature of the waste in cities and rural areas in the developing countries; • Highlight on available waste managements practices; • Two appropriate technologies practiced for waste valorization in Ethiopia • Future waste to resource technologies AAiT/AAU

  3. Introduction Solid wastes • all the wastes arising from human and animal activities that are normally solid • discarded as useless or unwanted • encompasses the heterogeneous mass of throwaways Socio-economic problem • Aesthetic • Land-use • Health, water pollution, air pollution • Economic considerations AAiT/AAU

  4. Solid Waste Management • Selection and application of suitable techniques, technologies, and management programs to achieve specific waste management objectives and goals • Respond to the regulations developed to implement the various regulatory laws • The elements of solid waste management • Sources • Characteristics • Quantities and composition of solid waste • Storage and handling • Solid waste collection • Transfer and transport AAiT/AAU

  5. Integrated SWM • Deploys four basic management options (strategies) • Source reduction • Reuse/Recycling • Composting • Waste-to-energy • Landfill/disposal AAiT/AAU

  6. Waste generated in the country AAiT/AAU

  7. Urban waste AAiT/AAU

  8. Composition • Estimated bio-organic waste generated in cities and towns • About 4600 tons/day = 1.7 M tons/year • Does not night soil • Does not include industrial, commercial and institutional wastes AAiT/AAU

  9. At disposal site AAiT/AAU

  10. Common waste agricultural residues/biomass • Coffee residues AAiT/AAU

  11. Cotton residues AAiT/AAU

  12. Residues from the bio-fuel sector • Jatropha seed production • Pulp • husk • Caster seed • Weed plants & bamboo • Prosopis Juliflora AAiT/AAU

  13. Assessment of Energy Recovery Potential of SW • Thermo-chemical conversion • Total waste quantity : W tonnes • Net Calorific Value : NCV k-cal/kg. • Energy recovery potential (kWh) = NCV x W x 1000/860 = 1.16 x NCV x W • Power generation potential (kW) = 1.16 x NCV x W/ 24 = 0.048 x NCV x W • Conversion Efficiency = 25% • Net power generation potential (kW) = 0.012 x NCV x W • If NCV = 1200 k-cal/kg., then • Net power generation potential (kW) = 14.4 x W AAiT/AAU

  14. Bio-chemical conversion • Total waste quantity: W (tonnes) • Total Organic / Volatile Solids: VS = 50 %, say • Organic bio-degradable fraction : approx. 66% of VS = 0.33 x W • Typical digestion efficiency = 60 % • Typical bio-gas yield: B (m3 ) = 0.80 m3 / kg. of VS destroyed = 0.80 x 0.60 x 0.33 x W x1000 = 158.4 x W • Calorific Value of bio-gas = 5000 kcal/m3 (typical) • Energy recovery potential (kWh) = B x 5000 / 860 = 921 x W • Power generation potential (kW) = 921 x W/ 24 = 38.4 x W • Typical Conversion Efficiency = 30% • Net power generation potential (kW) = 11.5 x W AAiT/AAU

  15. Traditional uses of waste biomass • For fuel in its low density form • For soil nutrient recycling • Excess slow biodegradable • burns in the field or agro- • processing sites • Dumped into the streams AAiT/AAU

  16. Highlight on available waste managements practices AAiT/AAU

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  19. Example AAiT/AAU

  20. AAiT/AAU

  21. Applied appropriate waste-to-energy technologies • Anaerobic digestion to biogas production • Briquette c charcoal production AAiT/AAU

  22. Anaerobic digestion to biogas production • The status of Biogas technology in Ethiopia • The Ministry of Energy and Water has two departments work on biogas and energy related activities: • the Alternative Energy Technical Dissemination and Promotion Directorate covering the household energy efficiency; • the Alternative Energy Design and Development Directorate (AEDDD) AAiT/AAU

  23. In 1957/58, the first was introduced into Ambo Agricultural College Ethiopia • In 1970s, two pilot biogas units as a project with FAO promote biogas • one with a farmer near Debre Zeit that is still functioning, • another with a school near Kobo in Wollo were build • In the past two and half decades • around 1000 plants (size ranging 2.5 – 200 m3) have been built for households, communities and institutions by nine different GOs &NGOs • Today, 40% of the constructed biogas plants are non-operational. AAiT/AAU

  24. The National Biogas Program for Ethiopia • a standardized design, participatory planning to produce a commercially viable system • aims to create local jobs, • uses proven technology • build capacity in technical ability. • 14,000 plants are planned to be installed over five years (2009 – 2013) • 50% of the plants are expected to include a toilet attachment. AAiT/AAU

  25. Commonly used in rural areas with livestock manure as major feedstock; • There is national level project to erect 14000 biogas plants in rural Ethiopia • In urban areas, there are some biogas plant • human waste – institutions • Cow dung and vegetable wastes AAiT/AAU

  26. Process-Input-Product AAiT/AAU

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  30. Use of bio-gas manure • Benefits AAiT/AAU

  31. NPK value of FYM and biogas manure AAiT/AAU

  32. Designing the bio-digester • Design parameters: • Selection/characterization feed materials • Biodegradability • C/N ratio • Biomass (availability) feed rate (Q, kg/day) • Gas production rate (G, m3/hr) • Required biogas amount (Gt) • Hydraulic retention time or sludge age (HRT or ) AAiT/AAU

  33. AAiT/AAU Figure 4.1. General biogas plant drawing for the Sinidu model GGC 2047

  34. Gas production rate AAiT/AAU

  35. AAiT/AAU

  36. Empirical relation • Volume • Geometric AAiT/AAU

  37. Cost of • production AAiT/AAU

  38. Installation costs AAiT/AAU

  39. Comparison with conventional fuel AAiT/AAU

  40. AAiT/AAU

  41. Briquette charcoal production • Carbonization process • has two stages: • Evaporation • Pyrolysis • 520oF (270oC) AAiT/AAU

  42. AAiT/AAU

  43. Batch carbonization time • Time to drive the water content of the biomass (estimated from graph) • Heating to the pyrolysis starting temperature (270oC) • Time require to complete pyrolysis process (590oC) AAiT/AAU

  44. AAiT/AAU

  45. Rate of drying the biomass • h is the heat transfer coefficient kJ/s/m2.K • T = temperature difference between the head air and the temperature of the wood, K • w = latent heat of water, kJ/kg AAiT/AAU

  46. Traditional charcoal making AAiT/AAU

  47. Drum carbonizer • Improved carbonizer used AAiT/AAU

  48. Binders • The binder materials • Molasses • Starch • Tar • Special mud (Merere cheka) • 1.5 kg:30 kg AAiT/AAU

  49. Mixing • carbonized charcoal material is • coated with binder. • enhance charcoal adhesion and produce identical briquettes. AAiT/AAU

  50. Briquetting • Screw press briquetting AAiT/AAU

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