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we select, design, build and commission composting process, mainly, but not limited to:
i. Windrow Composting
ii. Aerated Static Piles
iii. In Vessel Composting
1. Rotating Drums
2. Static Composting
3. Agitated Beds
i. Windrow composting:
Windrow composting is one form of composting which biodegrades organic material in long narrow piles. Windrow composting can be used to process yard trimmings, food scraps, paper products, and biosolids. Heat production eliminates pathogens, creating a compost product for use as a mulch, soil conditioner, or topsoil additive. With moisture control and mechanical agitation to re-establish porosity, the organic material can slowly decompose outdoors.
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ii. Aerated Static Pile:
Aerated static pile composting takes place in a windrow placed over a perforated piping system. Air is forced through the piping system. This forced aeration reduces the need for mechanical turning which is required frequently in windrow composting to maintain porosity. Low-volume, batch composting takes place under ideal conditions in smaller static or aerated bins. Compostable materials are loaded in the bin, and the material is generally turned with a custom designed turner or mechanically aerated.
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iii. In-vessel Composting:
This kind of composting aerobically biodegrades organic material, generating enough heat to destroy pathogens. Like other forms of composting, the end product of this compost process can be sold as a mulch, soil conditioner, or topsoil additive. In-vessel systems can compost yard trimmings, food scraps, sewage sludge, mixed wastes, and paper products. These materials degrade in a vessel under ideal conditions. This kind of composting demands exact oxygen and temperature regulation. Carbon to nitrogen ratios and moisture content must be considered as well.
Compostable materials are chipped, pulverized, or shredded into similar-sized pieces to promote rapid decomposition. In addition, oxygen and temperature in the compost should be sustained for ideal conditions for the decomposition organisms. The temperature must be elevated in order to kill pathogens and weeds, but low enough to keep the decomposition organisms alive. Generally, air is produced by blowers, flowing up through the compost pile. Air can be provided by piping systems or damper configurations set below the compost pile. Temperature is regulated by cyclic aeration. Odor control can be accomplished by collection and treatment of the process and building air.
1- Composting Batch Drums
Hammer milled previously segregated compostables are introduced into stainless steel batch drums with small capacities (from 2 to 3.6 m³). Small aeration louvers are located on the side of the drums. Drums rotate at a low speed to allow a good material mix as well as a complete aeration of the entire mixture. After 3-5 days in the drums, the goods are taken out and dried in windrow and/or aerated static piles for 3 to 4 weeks to allow complete maturation of the compost. Advantages of the system:
a- Increased process control (retention time, temperature...)
b- On a smaller scale machines, maintenance is reduced and easier to perform.
c- In case of failure of one drum, the facility can still operate with the
remaining drums.
d- In case the capacity of the facility needs to be increased, all that is
needed is the further addition of drums at low cost.
2- Continuous Feed Drums:
Hammer milled previously segregated compostables are continuously (daily) introduced from one end into a steel drum with a total capacity of 23 m³. Drums rotate at a low speed to allow a good material mix as well as a complete aeration of the entire mixture. Warmed air (through blowers) is introduced into the drum to warrant an aerobic condition for proper digestion. After 3-5 days in the drums, the goods are taken out from the other end of the drum, and dried in windrow and/or aerated static piles for 3 to 4 weeks to allow complete maturation of the compost
3- Static Composting
Hammer milled previously segregated compostables are fed by batches into either especially converted containers, tunnels, or simply concrete bunkers. All are equipped with a perforated floor, removable, self cleaning, made of coated perforated steel sheets.
Static composting features an automated control and monitoring system designed to optimize process conditions, keep the operator informed, and collect data required for regulatory compliance. The primary components of this system are the operator interface PC software (optional), the field control nodes, the blower control variable frequency drives (VFDs), and the temperature and pressure sensors.
Once the container, tunnel or bunker is filled, temperature probes are inserted into the compost bed. During primary composting, the control system constantly monitors temperatures using the probes located near the top and bottom of the composting material. Recorded temperatures are logged and provide feedback for the control of both the volume and the direction of aeration. By moderating and reversing airflow, the system automatically maintains uniform operator selected temperatures through out the composting media. This process control minimizes odor generation and guides each batch through control regimes to achieve EPA 503 requirements for Processes to Further Reduce Pathogens (PFRP) and Vector Attraction Reduction (VAR).
4- Agitated Beds
The composting system consists of concrete channels. Each channel is 2-3 meter wide, 1.83-2.13-2.44 meters high with a variable length. Raw organic materials are placed in one end of the channel. Over a period of two to four weeks, the materials are mechanically moved with a turner from one end of the channel to the other end. The compost turner mixes and moves composting material in 2-3 meter wide, 1.83-2.13-2.44 meters high with a variable length. It rides along the top of the concrete walls and is powered by a 25-50 or 100 hp electrical motor. An elevating drum and conveyor reaches down to the bottom of the channel. This conveyor consists of spikes mounted on independent the drum. These spikes lift, mix and move the composting material along the channel.
Temperature and ventilation controls maintain aerobic conditions and optimum temperatures during the composting process. A series of blowers are controlled by an automatic feedback system in addition to a timing sequence, to provide positive, forced aeration. Thermocouples permanently mounted in the bay walls interface with a PLC that activates blowers when temperature set points are exceeded.
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