INTRODUCTION: COMPOSTING
The Sanitary landfill sites are fast disappearing. Dumping Waste into Landfill sites in not the solution of Municipal Solid Waste Management. Composting provides a way out not only to reduce the amount of waste that needs to be disposed off but also converts garbage into a product that is useful for gardening, landscaping or house plants.
What can be Composted: Good things you can compost are vegetable peelings, fruit waste, tea bags , plant prunings, grass cuttings etc.
What cant be used: Certain things should never be placed in your bin. Keep away COOKED vegetables, Meat, Dairy Products, Diseased Plants,. Ideally wet garbage should not be put into the bin.
THE FIRST STEP:TWO BINS AT HOMES: Segregate the garbage before handing it to the sweepers who come to your homes. DRY & WET waste need to be separated at the household level. Two storage bin of different color should be provided at homes for the purpose.
Segregation at Source:
- Encouraging residents / producers to segregate
- Separation of Bio-degradable and non-biodegradable at source.
- Involve Rag pickers in segregation at source.
- Involve Self-help Groups in segregation, if required.
- Introduction of TWO BIN system.
THE SECOND STEP: The sweeper store the kitchen waste like food leftovers, vegetables, meat refuse, egg shells at the compost making site. He take the dry waste away for recycle and landfill.
Third Step: COMPOST MAKING: A fresh stock of compost is ready every three weeks in compost plants.
Fourth Step: Marketing and selling of compost. This will not create a problem if it is sold as organic manure. All the tea gardens will be happy to take it. Also all health conscious people will stop using chemical fertilizers in their kitchen garden.
ANNEXURE-I NORMS FOR GENERATION OF GARBAGE
| Category of garbage | Quantity generated |
| Domestic household (1) Population range upto 1 lakh (2) Population range 1 to 5 lakh (3) Population range 5 to 10 lakh (4) Population range 10 to 20 lakh |
0.21 Kg per person per day 0.25 Kg per person per day 0.27 Kg per person per day |
| Street sweepings and drain silt | 0.10 Kg per person per day |
| Slaughter House: (1) Small slaughter house (2) Medium slaughter house (3) Large slaughter house |
2 to 6 ton per day 6 to 7 ton per day |
| Domestic waste from Hospitals / Clinics etc. | 1.1 Kg per bed per day |
METHOD OF WINDROW COMPOSTING
:The aerobic composting process involves placing the waste into windrows. Windrows are long trapezoidal shaped heaps of waste placed on concrete or hard clay base with drains. The surface water from the windrows impervious base goes to the Effluent Treatment Plant. All uncovered windrow areas should be provided with an impermeable base.Such a base may be made of concrete or of compacted clay, 50 centimetres thick, having permeability less than 10 centimetres/second. The base must be provided with 1 to 2 percent slope and must be encircled by lined drains for collection of leachate/surface water runoff. All lined drains should beconnected to a lined settling pond, where tests for quality of waste-water are to be performed on a weekly basis. A treatment unit will be provided to ensure that the waste-water is discharged to open drains only after it meets the regulatory standards.
A land area of 100m x 90 mtr is required for processing 50 tonnes of waste per day. In this method, refuse is delivered on a paved/unpaved open space but levelled and well drained land in about 20 windrows with each windrow 3m long x 2m wide x 1.5m high, with a total volume not exceeding 9.0 cu.m.Each windrow would be turned on 6th& 11thdays outside to the centre by front end loaders or manually to destroy insects larvae and to provide aeration. On 16thday, windrow would be broken down and passed through manually operated rotary screens of about 25mm square mesh to remove the oversize contrary material. The material retained in 25 mm sieve is rejected and sent to land fill site. The material passing 10mm sieve and retained on 4 mm sieve is grade II compost. The material that passes 4 mm sieve is grade I compost.The screened compost is stored for about 30 days in heaps about 2m wide x 1.5m high and up to 20m long to ensure stabilization before sale.For this a maturity yard of area 600 sq mtr for storing 30 days compost is to be developed.
Equipment Required:
- Front end loader
- Conveyer
- Manual Rotary
LAYOUT OF A WINDROW COMPOST PLANT
THE FINAL COMPOST CHARACTERISTICS:
The compost prepared from MSW should be black brown or at least black in colour. It should be crumbly in nature with an earthy odour. The pH should be neutral though slightly acidic or alkaline pH within the range of 6.5 to 7.5 can be tolerated.The compost should neither be completely dry nor it be lumpy and water should not come out of the mass when squeezed.
The Nitrogen, Phosphorous and Potassium (NPK) contents should be more than one percent each. The Nitrogen should be in the form of Nitrates for proper utilisation by the plants. The C/N ratio should be between 15 to 20.In order to ensure safe application of compost,
As the compost plantoperates at a constant rate, a balancing storage has to be provided to absorb the fluctuations in the waste input to the plant. This is provided in a storage hopper of 8 to 24 hours storage capacity, the exact value depending upon the schedule of incoming trucks, the number of shifts and the number of days the plant and solid waste collection system works.
. These windrows are turned every 5 days to ensure aerobic decomposition. Various types of equipment such as front end loaders/windrows reshifters are used for turning of windrows.At the end of the 3 to 4 weeks period, the material is known as green or fresh compost wherein the cellulose has not been fully stabilised. It is hence stored in large sized windrows for 1-2 months either at the plant or the farms. At the end of the storage period, it is known as ripe compost.
POINTS TO BE NOTED:
However, the composting mass should have a certain minimum moisture content in it for the organisms to survive. The optimum moisture content is known to be between 50 to 60 % . Higher moisture content may be required while composting straw and strong fibrous material which soften the fibre and fills the large pore spaces.
The C/N ratio considers the available carbon as well as the available nitrogenwhile the available carbon and nitrogen in the MSW may vary from sample to sample. Whenever the C/N ratio is less than the optimum, carbon source such as straw, sawdust, paper are added while if the ratio is too high, the sewage sludge, slaughter house waste, blood etc. are added as a source of nitrogen.
During the decomposition, the oxygen gets depleted and has to be continuously replenished. This can be achieved by turning of windrows . During the turning, it is necessary to bring inner mass to the outer surface and to transfer the outer waste to the inner portion.Studies at NEERI have shown that the optimum turning interval which will reduce the cost and simultaneously maintain aerobic conditions is 5 days.
The windrows should be located over impervious surface so that the surface water from the windrows can go to the Effluent Treatment Plant.
:-• Large storage hoppers are not needed.
• Covering of windrow area is not required as the plants are normally shut down during monsoon for annual repairs.
• Artificial aeration under Indian conditions is not required
• It is preferable to first stabilise the raw material and then subject it to picking and size reduction. This will require same windrow area, and improve efficiency of picking and size reduction
• Composting should not be considered as a commercial venture but should be treated as a processing method to reduce the MSW content to be dumped at landfill sites..
• On such days when the waste cannot be accepted at the compost plant or if shutdown occurs for extended period due to rains/cold climate/major breakdown or annual maintenance, the waste should be diverted to a properly designed and operated MSW landfill.
•. The height of stockpiled waste should not exceed 3 metres and the storage area must have provision for odour control, litter control, fire control and birds control.
The areas where compost is to be supplied should be near the site and should be easily accessible. A site for disposal of non compostables should be available near the compost plant site.Trees planted along the periphery of the site will serve partly as a barrier against the noise and odour from the plant and also help in litter control byreducing the wind speed . The trees will also protect the plant from dust and pollutants due to the highway.
In the North East Indian states, to protect the windrows from heavy rainfall, the windrow area will have to be covered.
GO FOR A PILOT PLANT STUDY FIRST:
The design and construction of a full scale compost plant needs at least 1.5 to 2 years. Before the plant becomes operational, pilot scale studies be carried out using a small quantity of the raw waste that will be used in the final plant. The raw waste as well as finished compost should also be analysed for heavy metal content. The output of the plant should be widely advertised to the consumers. The pilot studies will help determine the proportion of non-compostables that need disposal, the compost output per tonne of input and its nutrient contents.
QUOTATION FOR A 22 MT WINDROWS COMPOSTING PROJECT
1. Key Personnel details
| S No | Category of personnel | Name | Qualification | Present designation | Experience in relevant field | Remarks |
| 1 | Team Leader (Solid waste Engineer with 10 Years experience) | |||||
| 2 | Municipal Engineering Specialist | |||||
| 3 | Medical and Health Specialist | |||||
| 4 | Finance Specialist | |||||
| 5 | Management specialist |
