COMPOST BIN MANUFACTURING Introduction In Sri Lanka, home composting is promoted in many municipalities as a simple and low-cost solution to emerging waste disposal problems in the present day society. In this process, valuable compost is produced using the organic components of household waste that we dispose of as being spent, useless, worthless, or in excess to our needs. Different types of home composting units/bins are available in the market, which are manufactured from plastic, metal or concrete rings. Concrete bins have been identified as the most cost-effective and environmentally friendly solution, when compared to other designs. Production of concrete bins has been limited to a few fabricators in the capital city Colombo but there is a huge gap in the dissemination of this knowledge to the other small-scale fabricators in other parts of Sri Lanka. Therefore, this technical brief is intended to disseminate the technology of concrete composting bin fabrication. Main component of 3-ring concrete compost bin Top lid Top ring Middle ring Bottom ring Compost removal doors Base Plate-01. Credit: Practical Action South Asia Moulds for the manufacturing process During the bin fabricating process, each component of the bin is moulded separately in concrete. Moulds can be prepared using metal sheets or, preferably, fibreglass. Separate moulds are required for: Basement Bottom ring Middle ring Top ring Top cover Covering lid Compost removing doors Practical Action, The Schumacher Centre, Bourton on Dunsmore, Rugby, Warwickshire, CV23 9QZ, UK T +44 (0)1926 634400 | F +44 (0)1926 634401 | E infoserv@practicalaction.org.uk | W www.practicalaction.org ______________________________________________________________________________________________ Practical Action is a registered charity and company limited by guarantee. Company Reg. No. 871954, England | Reg. Charity No.247257 | VAT No. 880 9924 76 | Patron HRH The Prince of Wales, KG, KT, GCB Compost bin manufacture Practical Action Material required and cost for fabrica ting one concrete bin Description Cement (rapid hardening cement) Iron (1/4” rods) Metals(3/4”) Sand Paints Labour Cost for mould Total Amount /rate (Cost -18000.00/mould) 30.0 Kg 1.25 Kg 1.5 cu ft 1.25 cu ft 3 bins/person/day Assuming 100 bins are produced from 1 mould Cost (Rs) as prices on 1/06/2005 300.00 112.50 60.00 50.00 60.00 275.00 180.00 1037.50 Fabricating process A) Preparation of the concrete mixture Material Sand Metal Cement Ratios 4 pans (screened through ½” mesh) 3 pans (size ¾”) 30 kg The materials above should be well mixed and then gradually add water to have a free-flowing concrete mixture. A good finish can be expected by adding 1 pan of quarry dust. B) Bottom pad Steps 1. Get the bottom pad mould (1” width iron ring that is bolted by one side) and place it on a polythene sheet laid on levelled ground (Plate-02). 2. Pour concrete mixture into the mould (half –fill). 20” 26” 25” 14” Plate-02 Credit: Practical Action South Asia Plate-03 3. Place iron rings (¼”) as in diagram (three rings) Plate-03. 4. Fill the mould with concrete mixture covering the iron rings completely. 5. Level the surface using a straight pole and remove the excess concrete from the mould (maintain thickness 1”). 6. Locate 4-5 PVC pipe pieces (½ ” diameter and 2” long each) to make the pad porous (Plate 04). 2 Compost bin manufacture Practical Action Plate-04. Credit: Practical Action South Asia C) Bottom, middle and top rings (depend on the design) 1. Get three separate moulds for top middle and bottom rings (correctly fix all components of each mould using bolt and nuts). Before fixing the ring parts of the mould, some burnt oil (oil from petrol vehicles is preferable) can be applied to the inner side of the mould. It makes it easier to remove the blocks form the mould. 2. Locate the moulds on levelled ground (Plate 05 and 06). 23” 21” 14” Plate-05 Credit: Practical Action South Asia Plate -06 3. Get the concrete mixture and pour it in to the moulds to fill 1-1.5” from the bottom (Plate 07). 4. Insert first iron ring between inner and outer moulds – should not touch the walls of the moulds 5. Fixed the plugs for aeration holes in all bins (Plate-09) 6. Add concrete mixture gradually and spread it uniformly with a stick (P late -08) Plate- 07 3 Plate -08 Credit: Practical Action South Asia Compost bin manufacture Practical Action 2” 3” Plate -09 Credit: Practical Action South Asia For middle and top rings 7. Once the mould is filled up to 1-1.5” from the top level-place 2nd iron ring as first ring (Plate10). 8. Fill the concrete mixture up to the top level of the moulds and levelled using a trowel 9. After 30 minutes, fix the strip to the mould and add some mortar to make the inner interlocking grove (only for middle ring) and levelled (Plate-11). 11” Plate -10 Credit: Practical Action South Asia Plate -11 For bottom ring 7. Stop the filling the mould once the level of the concrete is close to 4” form the top. 8. Insert the 2nd iron ring and add 1” thick concrete layer on it. 9. Insert 3 sockets with equal spacing to leave the space for compost removing doors (Plate-12). 10. Fill the space between the sockets and insert iron rods from the sides of each door (6 rods 15” long and ¼” diameter) (Plate-13). 11. Cover the iron rods level the surface. Plate -12 Credit: Practical Action South Asia Plate -13 4 Compost bin manufacture Practical Action c) Top cover 1. Place the mould on levelled ground. 2. Apply some oil inside the mould (Plate -14) 26” 12” 9” Plate – 14 Credit: Practical Action South Asia Plate - 15 3. Fill the mould with concrete (¾ ” from bottom). 4. Place two iron rings (¼”) (Plate-15). 5. Fill with concrete up to the top level of the mould (1.5”) leaving the space for the door (Plate 16). 10.5” 5” Plate- 16. Credit: Practical Action South Asia d) Top lid and compost removing doors 1. Place the mould on levelled ground. 2. Apply some used oil in side the mould (Plate-17). 3. Fill the mould with concrete (half). 10” 7.5” 3.5” 11.5” Plate -17 Credit: Practical Action South Asia Plate-18 4. Place iron rods as shown in the diagrams (Plate-18). 5. Fill with concrete up to the top level of the mould and levelled well. 5
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