The process of natural decomposition is very important to one type of waste disposal. Composting is a form of waste disposal where organic waste decomposes naturally under oxygen-rich conditions. Although all waste will eventually decompose, only certain waste items are considered compostable and should be added to compost containers. Food waste, such as banana peels, coffee grinds, and eggshells, are great items to compost. Adding meat products to compost should be avoided because as it decomposes, it will attract large animals and will smell very badly.
Types of Composting
- Onsite Composting
- Aerated Composting
- Aerated Static Pile Composting
- In-vessel Composting
Organizations that are going to compost small amounts of wasted food can compost onsite. Composting can significantly reduce the amount of wasted food that is thrown away. Yard trimmings and small quantities of food scraps can be composted onsite. Animal products and large quantities of food scraps are not appropriate for onsite composting.
Things to Think About
- The climate and seasons changes will not have a big effect on onsite composting. Small adjustments can be made when changes happen such as when the rainy season approaches.
- Food scraps need to be handled properly so they don’t cause odors or attract unwanted insects or animals.
- Onsite composting takes very little time or equipment. Education is the key. Local communities might hold composting demonstrations and seminars to encourage homeowners or businesses to compost on their own properties.
- Creating compost can take up to two years, but manual turning can speed up the process to between three to six months.
- Compost, however, should not be used as potting soil for houseplants because of the presence of weed and grass seeds.
- You can leave grass clippings on the lawn-known as “grass cycling.” These cuttings will decompose naturally and return some nutrients back to the soil, similar to composting.
- You can put leaves aside and use them as mulch around trees and scrubs to retain moisture.
Red worms in bins feed on food scraps, yard trimmings, and other organic matter to create compost. The worms break down this material into high quality compost called castings. Worm bins are easy to construct and are also available for purchase. One pound of mature worms (approximately 800-1,000 worms) can eat up to half a pound of organic material per day. The bins can be sized to match the volume of food scraps that will be turned into castings.
It typically takes three to four months to produce usable castings. The castings can be used as potting soil. The other by-product of vermicomposting known as “worm tea” is used as a high-quality liquid fertilizer for houseplants or gardens.
Night-crawlers and field worms found in gardens are not appropriate for vermiculture.
What Can Be Composted – Vermiculture?
- Food scraps
- Yard trimmings such as grass and plants
Things to Think About
- Ideal for apartment dwellers or small offices.
- Schools can use vermiculture to teach children conservation and recycling.
- It is important to keep the worms alive and healthy by providing the proper conditions and sufficient food.
- Prepare bedding, bury garbage, and separate worms from their castings.
- Worms are sensitive to changes in climate.
- Extreme temperatures and direct sunlight are not healthy for the worms.
- The best temperatures for vermicomposting range from 55° F to 77° F.
- In hot, arid areas, the bin should be placed under the shade.
- Vermicomposting indoors can avoid many of these problems.
Aerated (Turned) Windrow Composting
Aerated or turned windrow composting is suited for large volumes such as that generated by entire communities and collected by local governments, and high-volume food-processing businesses (e.g., restaurants, cafeterias, packing plants). It will yield significant amounts of compost, which might require assistance to market the end-product. Local governments may want to make the compost available to residents for a low or no cost.
This type of composting involves forming organic waste into rows of long piles called “windrows” and aerating them periodically by either manually or mechanically turning the piles. The ideal pile height is between four and eight feet with a width of 14 to 16 feet. This size pile is large enough to generate enough heat and maintain temperatures. It is small enough to allow oxygen flow to the windrow’s core.
Large volumes of diverse wastes such as yard trimmings, grease, liquids, and animal by-products (such as fish and poultry wastes) can be composted through this method.
Things to Think About
- Windrow composting often requires large tracts of land, sturdy equipment, a continual supply of labor to maintain and operate the facility, and patience to experiment with various materials mixtures and turning frequencies.
- In a warm, arid climate, windows are sometimes covered or placed under a shelter to prevent water from evaporating.
- In rainy seasons, the shapes of the pile can be adjusted so that water runs off the top of the pile rather than being absorbed into the pile.
- Windrow composting can work in cold climates. Often the outside of the pile might freeze, but in its core, a windrow can reach 140° F.
- Leachate is liquid released during the composting process. This can contaminate local groundwater and surface-water supplies. It should be collected and treated.
- Windrow composting is a large-scale operation and might be subject to regulatory enforcement, zoning, and siting requirements. Compost should be tested in a laboratory for bacterial and heavy metal content.
- Odors also need to be controlled. The public should be informed of the operation and have a method to address any complaints about animals or bad odors.
Aerated Static Pile Composting
Aerated static pile composting produces compost relatively quickly (within three to six months). It is suitable for a relatively homogenous mix of organic waste and work well for larger quantity generators of yard trimmings and compostable municipal solid waste (e.g., food scraps, paper products), such as local governments, landscapers, or farms. This method, however, does not work well for composting animal by-products or grease from food processing industries.
In aerated static pile composting, organic waste mixed in a large pile. To aerate the pile, layers of loosely piled bulking agents (e.g., wood chips, shredded newspaper) are added so that air can pass from the bottom to the top of the pile. The piles also can be placed over a network of pipes that deliver air into or draw air out of the pile. Air blowers might be activated by a timer or a temperature sensor.
Things to Think about
- In a warm, arid climate, it may be necessary to cover the pile or place it under a shelter to prevent water from evaporating.
- In the cold, the core of the pile will retain its warm temperature. Aeration might be more difficult because passive air flowing is used rather than active turning. Placing the aerated static piles indoors with proper ventilation is also sometimes an option.
- Since there is no physical turning, this method requires careful monitoring to ensure that the outside of the pile heats up as much as the core.
- Applying a thick layer of finished compost over the pile may help alleviate any odors. If the air blower draws air out of the pile, filtering the air through a biofilter made from finished compost will also reduce any of the odors.
- This method may require significant cost and technical assistance to purchase, install, and maintain equipment such as blowers, pipes, sensors, and fans.
- Having a controlled supply of air allows construction of large piles, which require less land than the windrow method.
In-vessel composting can process large amounts of waste without taking up as much space as the windrow method and it can accommodate virtually any type of organic waste (e.g., meat, animal manure, biosolids, food scraps). This method involves feeding organic materials into a drum, silo, concrete-lined trench, or similar equipment. This allows good control of the environmental conditions such as temperature, moisture, and airflow. The material is mechanically turned or mixed to make sure the material is aerated. The size of the vessel can vary in size and capacity.
This method produces compost in just a few weeks. It takes a few more weeks or months until it is ready to use because the microbial activity needs to balance and the pile needs to cool.
Things to Think About
- Some are small enough to fit in a school or restaurant kitchen.
- Some are very large, similar to the size of the school bus. Large food processing plants often use these.
- Careful control, often electronically, of the climate allows year-round use of this method.
- Use in extremely cold weather is possible with insulation or indoor use.
- Very little odor or leachate is produced.
- This method is expensive and may require technical expertise to operate it properly.
- It uses much less land and manual labor than windrow composting.
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