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

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Presentation on theme: "Waste management: Appropriate technologies for developing countries (Ethiopia’s case) 1AAiT/AAU."— Presentation transcript:

1 Waste management: Appropriate technologies for developing countries (Ethiopia’s case) 1AAiT/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 2 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 3AAiT/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 4AAiT/AAU

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

6 6 Waste generated in the country

7 Urban waste 7AAiT/AAU

8 Composition AAiT/AAU8  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

9 At disposal site 9AAiT/AAU

10 Common waste agricultural residues/biomass  Coffee residues AAiT/AAU10

11  Cotton residues AAiT/AAU11

12  Residues from the bio-fuel sector –Jatropha seed production Pulp husk –Caster seed  Weed plants & bamboo – Prosopis Juliflora AAiT/AAU12

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 = x NCV x W –Conversion Efficiency = 25% –Net power generation potential (kW) = x NCV x W –If NCV = 1200 k-cal/kg., then –Net power generation potential (kW) = 14.4 x W AAiT/AAU13

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 = 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/AAU14

15 Traditional uses of waste biomass  For fuel in its low density form  For soil nutrient recycling  Excess slow biodegradable AAiT/AAU15 burns in the field or agro- processing sites Dumped into the streams

16 AAiT/AAU16 Highlight on available waste managements practices

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19 AAiT/AAU19 Example

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21 Applied appropriate waste-to-energy technologies  Anaerobic digestion to biogas production  Briquette c charcoal production AAiT/AAU21

22 Anaerobic digestion to biogas production  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/AAU22  The status of Biogas technology in Ethiopia

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 m 3 ) have been built for households, communities and institutions by nine different GOs &NGOs Today, 40% of the constructed biogas plants are non- operational. AAiT/AAU23

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/AAU24

25  Commonly used in rural areas with livestock manure as major feedstock;  There is national level project to erect biogas plants in rural Ethiopia  In urban areas, there are some biogas plant –human waste – institutions –Cow dung and vegetable wastes AAiT/AAU25

26 Process-Input-Product AAiT/AAU26

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30 AAiT/AAU30 Use of bio-gas manure  Benefits

31 AAiT/AAU31 NPK value of FYM and biogas ma nure

32 AAiT/AAU32 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, m 3 /hr) –Required biogas amount (Gt) –Hydraulic retention time or sludge age (HRT or  )

33 AAiT/AAU33 Figure 4.1. General biogas plant drawing for the Sinidu model GGC 2047

34 AAiT/AAU34 Gas production rate

35 AAiT/AAU35

36 AAiT/AAU36 Empirical relation  Volume  Geometric

37 AAiT/AAU37  Cost of production

38 AAiT/AAU38 Installation costs

39 AAiT/AAU39 Comparison with conventional fuel

40 AAiT/AAU40

41 Briquette charcoal production AAiT/AAU41  Carbonization process has two stages: –Evaporation –Pyrolysis 520 o F (270 o C)

42 AAiT/AAU42

43 AAiT/AAU43 Batch carbonization time –Time to drive the water content of the biomass (estimated from graph) –Heating to the pyrolysis starting temperature (270 o C) –Time require to complete pyrolysis process (590 o C)

44 AAiT/AAU44

45 AAiT/AAU45  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

46 AAiT/AAU46  Traditional charcoal making

47  Improved carbonizer used AAiT/AAU47

48 AAiT/AAU48 Binders  The binder materials –Molasses –Starch –Tar –Special mud (Merere cheka) –1.5 kg:30 kg

49 AAiT/AAU49 Mixing –carbonized charcoal material is coated with binder. –enhance charcoal adhesion and produce identical briquettes.

50 AAiT/AAU50 Briquetting  Screw press briquetting

51 AAiT/AAU51 –Designed to make a small size of 20mm diameter and produce six briquette charcoal at a time. –made from sheet metals and angle iron –the extruder fly wheel is made of concrete –a screw type press made of a sheet metal which is welded on a solid steel shaft, designed to produce high density briquette

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56 AAiT/AAU56  Beehive Briquette 1. Lever operated hand press (produces 8 briquettes at a time) 2. Single unit (Produces 1 briquette at a time)

57 AAiT/AAU57  Agglomerator A rotating drum glueing powder particles together using binder Agglomerated charcoal briquettes are spherical and have a diameters of 20 to 30 mm Production capacity kg/hr

58 AAiT/AAU58 Proximate analysis result of Prosopis charcoal in comparision with other biomass charcoal Type of charcoal Moisture(%) Volatile matter (%) Ash content (%) Fixed carbon (%) Calorific value (cal/gm) Acacia Spp. Charcoal Prosopis charcoal Bamboo charcoal Cotton stalk charcoal briquette Chat stalk charcoal briquette

59 AAiT/AAU59 Table 2: Proximate analysis results of agglobriquettes conducted at EREDPC laboratory Type of charcoalMoisture content (%) Volatile matter (%) Ash content (%) Fixed carbon (%) Calorific value (cal/gm) Agglobriquette (cotton stalk) Chat agglobriquette Bamboo agglobriquette 6123 Bamboo charcoal Prosopis charcoal Wood charcoal (Girrar) Source: EREDPC laboratory

60 AAiT/AAU60 Future waste to resource technologies Industrial uses

61 AAiT/AAU61 Fuel energy consumption  Example cement industry

62 –Substituting finance oil or heavy fuel –Planned up to 20 % substitute –Target industry – cement industry –Reduced imported fuel –Reduce greenhouse gas emissions AAiT/AAU62

63  Improving energy density and Transportation cost AAiT/AAU63 ─ Density 50 to 80 kg/m3 ─Moisture Up 20 % –Densifying > 600 kg/m3 –Pelletizing Increasing surface are for combustion –Torrifying or roasting Further increasing the energy density

64 Summary  Biogas and carbonization/briquetting organic waste  reduce the volume of waste generated  Generate clean energy  Produce very good bio-fertilizer  Appropriate waste management technologies  convert waste into resources for different economic activities;  help the generators to add value to their waste and generate income;  Reduce dependence on fossil fuel and greenhouse gas emission; 64AAiT/AAU


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