1. Dr. Prabha Joshi, Asst. Professor Department: B.E. Civil Engineering
Composting
Dr. Prabha Joshi, Asst. Professor
Department: B.E. Civil Engineering
Subject: Environmental Engineering - I
Semester: VI
Teaching Aids Service by KRRC Information Section

2. Principles of Composting
What Is Compost?
The product resulting from the controlled biological decomposition of organic materials
Sanitized through the generation of heat
Stabilized to the point where it is beneficial to plant growth
Provides humus, nutrients, and trace elements to soils
Organic Materials
Landfilled wastes (food, wood, textiles, sludges, etc.)
Agricultural wastes (plant or animal)
Industrial manufacturing byproducts
Yard trimmings
In short, anything that can be biodegraded

3. Why Compost? > 75% of solid waste is organic
Agricultural wastes  potential for nutrient pollution
Yard wastes – banned from landfills in some countries.
Compost benefits to soil – 11kg N, 6kgP (as P2O5), and 3kg K (as K2O) per ton of compost
Environmental sustainability
1 pound = kilogram

4. The Composting Process
Biological decomposition in aerobic environment
Decomposition & mineralization by microbes
Bacteria, actinomycetes, fungi, protozoans, nematodes
During the early active decomposition phase the thermophilic bacteria (mainly Bacillus, Clostridium and Pseudomones) act as the principal decomposers.
Fungi such as Mucor , Penicillium and Aspergillus are more active during the curing stage.

5. The Composting Process
Food source – Nitrogen (biodegradable organic matter)
Energy source – Carbon
Outputs
Heat
Water Vapor
Carbon Dioxide
Nutrients and minerals (compost)
Process occurs naturally, but can be accelerated by controlling essential elements

6. Composting Essential Elements
Nutrients
Carbon/Nitrogen (C/N) – 30:1 to 50:1
Carbon/Phosphorus (C/P) – 100:1 to 150:1
Moisture Content – 50% to 60%
Particle Size – ¼” to ¾” optimum
Porosity – 35% to 50%
pH – 6.5 to 8.0
Oxygen concentration - >5%
MTemperature – 55C. to 65o C.
Time – one to four months

7. Nutrient Balance in Composting
Optimum C/N ratio –is 30:1to 50:1
It is an imp factor for the bacterial activity to continue, the carbon should be 30 to 50 times more than the nitrogen.
C/N higher than optimum: nitrogen will be used up and carbon leftover, thereby leaving the digestion of organic matter incomplete.

8. C/N lower than optimum means when there is too much of nitrogen then the carbon will soon get exhausted and fermentation stops leaving nitrogen in the digestor which will combine with hydrogen to form amonia. This can kill or inhibit the growth of bacteria, especially the methane producers.
Thus the anaerobic digestion will hence require an optimum C/N ratio of about :1
Sources of N & P - Organic wastes, manures, sludges, etc.
Sources of C – wood wastes, woodchips, sawdust

9. Nutrient Balance in Composting
Example C/N Ratios:
Food waste 14 – 16 : 1
Refuse/trash 34 –80 : 1
Sewage sludge 5 –16 : 1
Corrugated cardboard : 1
Telephone books : 1
Mixing components needed to optimize C/N ratio

10. Moisture Content
Source of nutrients for microbial protein synthesis and growth
Optimum water content – 50% to 60% (wet weight basis)
< 50% - composting slows due to microbial desiccation
>60% - compaction, development of anaerobic conditions, putrefaction/fermentation (odors)
Water may be needed during mixing, composting
Yard wastes – 40 to 60 gallons per cubic yard
Typical moisture contents
Food wastes 70%
Manures and sludges 72% - 84%
Sawdust 19% - 65%
Corrugated cardboard 8%
Newsprint 3% - 8%

11. Particle Size & Distribution
Critical for balancing:
Surface area for growth of microbes (biofilm)
Adequate porosity for aeration (35% - 50%)
Larger particles (> 1”)
Lower surface area to mass ratio
Particle interior doesn’t compost – lack of oxygen
Smaller particles (< 1/8”)
Tend to pack and compact
Inhibit air flow through pile
Optimum size very material specific

12. pH Optimum range 6.5 – 8.0 Below pH = 6.5 Above pH – 8.0
Bacterial activity dominates
Below pH = 6.5
Fungi dominate over bacteria
Composting can be inhibited
Above pH – 8.0
Ammonia gas can be generated
Microbial populations decline

13. Porosity and Aeration Optimum porosity 35% - 50%
> 50% - energy lost is greater than heat produced lower temperatures in compost pile
< 35% - anaerobic conditions (odors)
Aeration – controls temperatures, removes moisture and CO2 and provides oxygen
Airflow needs directly proportional to biological activity
O2 concentration < 5% - anaerobic conditions

14. Time and Temperature
Temperature is key process control factor – monitor closely
Optimum temperatures: 55 –65o C.
Temperatures above 55o C will kill pathogens, fecal coliform & parasites
Optimum temps achieved by regulating airflow (turning) and/or pile size

15. Mechanism of Composting
Composting is a biochemical process in which aerobic and anaerobic microorganism decomposes organic matter into valuable manure called as compost.
Release heat
(Thermophilic state, which helps to destroy pathogens)
Organic matter
Organic matter
compost
Temp 55-60o c
(Mesophilic state ,Temp o c, promote mesophilic microbes for rapid decomposition )

16. Methods of Preparation of Compost
Indore Method
Bangalore Method
This method was developed by A. Howard and Y. D. Wad at the Institute of Plant industry, Indore, India
This method was worked out by L. N. Acharya at Indian Institute of Science, Bangalore.

17. Indore method
Size of the pit: In this method layers of vegetable waste and night soil are alternatively piled in depth of about cm each to a total depth of about 1.5 m in a trench, or above the ground to form a mound called a windrow.

18. Windrow: a windrow is a long mound or stack of the organic MSW (mixed with cattle dung and human excreta) dumped on the land in a height of about 1.5, 2m, usually about 2.5 to 3m wide

19. Indore method
Raw Material: Mix plant residues, weeds, sugarcane leaves, grass, wood ashes, bran etc.
Animal dung
Wood ashes
Water

20. Indore method First turning : Second turning : Third turning : Turning
The material is turned three times for proper aeration and moisture.
First turning :
10-15 days after filling the pits.
Second turning :
15 days after first turning.
Third turning :
After 2 month of second turning
During the process of turning the readily biodegradable organics are consumed . The waste Is allowed to cure for another 2-8 weeks without turning. The entire composting process thus Takes 3-4 months time after which the compost become ready to use as manure or sale.

21. Bangalore method
This method involves anaerobic decomposition and does not involve any turning to the waste and is hence cleaner than the Indore method. This method saves labour cost because there is no need of turning and regular sprinkling of water. The refuse and the night soil in this method are piled up in layers in an underground earthen trench (about 10mx1.5mx1.5m). This mass is covered at its top by a layer of earth of about 15cm depth and is finally left for decomposition.
 After the initial aerobic composting (about eight to ten days), the material undergoes anaerobic decomposition at a very slow rate. It takes about six to eight months to obtain the finished product.

22. Within 2-3 days intensive biological action starts.
Considerable heat generated in the process raising the temp. to about 75C.
The heat prevents the breeding of flies by destroying the larvae.
After about 4-5 months (depending upon season) the refuse get fully stabilized and changes in to humus.
This humus is removed from the trenches, sieved on 12.5mm sieve to remove stone, broken glass etc and then sold out in market as manure.
The empty trenches can again be used for receiving further batches of refuse.

23. Method of Filling the Composting Pits
Bangalore method
Method of Filling the Composting Pits
Spread the moist farm refuse at the bottom of the pit up to one inch.
Then, spread two inch of cattle dung followed by 1 or 2 inch layer of soil
This heap is made up to feet above the ground level following above process.
Finally the heap is covered with 1 inch thick mud.
After 8-9 months all material decomposes and compost becomes ready for the application.

24. Composting helps slow Climate Change
Climate Change is caused by greenhouse gases in our atmosphere.
Greenhouse Gases:
Carbon Dioxide
Methane
Nitrous Oxide

25. The Climate Change Connection
When food waste (and paper) decay in a landfill, methane is released.
Methane is a greenhouse gas 23 times more powerful than carbon dioxide.
The Climate Change Connection
Methane pipe at a landfill

26. Compost bins made from reused pallets
Composting doesn’t release methane because oxygen is part of the composting process.
There is no oxygen in a landfill.
Compost bins made from reused pallets

27. Vermicompost

28. Vermicomposting
Composting worms eat decaying organic matter and turn it into worm castings (worm feces). The result is vermicompost, a mixture of worm castings and composted material such as the bedding in bin.

29. Concept
2. Vermicomposting

30. Introduction
Vermicomposting is a technology of composting various forms of biodegradable wastes with the help of earthworms.
This compost is perfectly balanced and good in plants nutrients.

31. Benefits of vermicompost
Vermicompost is a nutrient rich compost which:
helps better plant growth and crop yield
improves physical structure of soil.
enriches soil with micro-organisms
attracts deep-burrowing earthworms already present in the soil which, indirectly improves fertility of soil.
increase water holding capacity of soil.
enhances germination, plant growth, and crop yield.
improves root growth of plants.
enriches soil with plant hormones such as auxins and gibberellic acid.
it is helpful in elimination of biowastes .

32. Nutrient profile of vermicompost
Vermicompost contains :
1.6% Nitrogen;
0.7% Phosphorus;
0.8% Potash;
0.5% Calcium;
0.2% Magnesium;
175 ppm Iron;
96.5 ppm Manganese;
24.5 ppm Zinc
15.5 C:N ratio.

33. Requirements Endogeic Anecic Soil dwelling or upper soil surface
( ‘within the earth’)
Deep burrowing
species
(‘out of earth’)
Ex. Eisenia foetida Ex. Octochaetona thrustoni Ex. Lampito mauritii

34. Common varieties used are-

35. Pre digested or decomposed organic waste

36. Source of water
Buckets and water sprayer

37. Method of Production Vermin compost can be produced by two methods :
Windrows Method
Pit Method

38. Pit method
Pit method is commonly used for small scale production of vermin compost. These steps can be followed :
Construct a pit of 3 x 2 x 1 m size (L x W xD) over ground surface using bricks. Size of pit may vary as per availability of raw materials
Fill the pit with following four layers:
1st layer – sand or sandy soil of 5-6 cm. This layer helps to drain excess water from the pit.
2nd layer - paddy straw or other crop residue of 30 cm above 1st layer which will be used for providing aeration to the pit.
3rd layer - 15 to 30 days old dung over paddy straw layer at a thickness of cm. This helps in initiating microbial activity.
4th layer - pre-digested material about 50 cm
Inoculate 1000 worms per square meter area or 10 kg earthworm in 100 kg of organic matter.
Spray water on the bed and gunny bag. Maintain 50-60% moisture of the pit by periodical water spraying.

39. Worms, worms Worms become mature at 10 weeks
Will produce 2 to 3 cocoons a week
Each cocoon holds 2-5 babies
Cocoons take 3 weeks to hatch

40. And more worms
In 6 months, 8 worms will multiply into 1500 if conditions are right
They will stop breeding if there is not enough food or space.

41. Mrs. Shakuntala Devi, Distt. Aligarh (UP)
Training at D.S.College Aligarh UP
Women Farmers Unit
Vermicompost production unit at vill. Hassain, Distt. Hathras (UP)

42. Precautions
Only plant-based materials such as grass, leaves or vegetable peelings should be used for preparing vermin compost.
Materials of animal origin such as egg-shells, meal, bone, chicken droppings etc., are not suitable for preparing vermin compost.
Tobacco leaves are not suitable for rearing earthworms.
The earthworms should be protected against birds, termites, ants and rats.
Adequate moisture should be maintained during the process. Either stagnant water or lack of moisture could kill the earthworms.
The vermin compost should be removed from the bed at a regular interval and replaced by fresh waste materials.

43. LET US SUM UP
Vermicomposting is a technology of composting various forms of biodegradable wastes with the help of earthworms.
The earthworms eat the organic residues, digest it and excrete in the form of pellets. The earthworm excreta called worm cast.

44. Vermiculture Training Centre
Vermicuture Research Station, D.S.College (Dr.BRA University),Aligarh