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 eCourseware@AIKTC Teaching Aids Service by KRRC Information Section

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

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 = 0.453 592 37 kilogram

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.

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

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

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.

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 30-50 :1 Sources of N & P - Organic wastes, manures, sludges, etc. Sources of C – wood wastes, woodchips, sawdust

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 563 : 1 Telephone books 772 : 1 Mixing components needed to optimize C/N ratio

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%

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

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

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

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

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. 25-30o c, promote mesophilic microbes for rapid decomposition )

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.

Indore method Size of the pit: In this method layers of vegetable waste and night soil are alternatively piled in depth of about 7.5-10cm each to a total depth of about 1.5 m in a trench, or above the ground to form a mound called a windrow.

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

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

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.

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.

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.

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 1.5-2.0 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.

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

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

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

Vermicompost

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.

Concept 2. Vermicomposting

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.

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 .

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.

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

Common varieties used are-

Pre digested or decomposed organic waste

Source of water Buckets and water sprayer

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

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 20-30 cm. This helps in initiating microbial activity. 4th layer - pre-digested material about 50 cm Inoculate earthworm @ 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.

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

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.

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)

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.

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.

Vermiculture Training Centre Vermicuture Research Station, D.S.College (Dr.BRA University),Aligarh-202001