Compost is the stable, humus-like product resulting from the biological decomposition of organic matter such as grass clippings, leaves, manure, sawdust and hedge trimmings under controlled conditions. In simple terms, compost is decomposed organic matter that can be used to help grow plants and keep soil healthy. Compost is a valuable soil amendment to add nutrients and goodness that is needed by plants for good growth and development.
It is time to get serious about composting organic waste. It is essential to come up with alternative methods for recovering waste that are renewable and sustainable. An important way to start is by bringing composting to more cities, businesses and schools. With support from people who are already in favor of composting, we can educate others and begin building a long-lasting system.
Different Types of Compost
Compost can be classified into several types in accordance with its main raw materials:
▽ Manure Compost
Composting manure is an excellent manure management technique, useful for both backyard or small farm owners, and larger composting facilities. Via composting, the organic nitrogen contained within the initial fresh manure is converted to ammonium nitrogen by various microorganisms. Manure compost is usually used as nutrient sources for fruit, crops and vegetables.
The most common sources of manure are cows, horses, sheep, pigs, goats, and poultry. (Other animal waste is generally not recommended as manure or fertilizer today.) Composting methods vary with the usage of finished compost and composting scales. Whatever technology one adopts, the C:N ratio need to be noticed: as manure is nitrogen-rich materials, when composting, it should be mixed with a certain amount of carbon-rich organic materials (such as pine shavings from bedding, straw and hay from the animal barns etc.) to keep the C:N ratio=25:1/30:1.
▽ Food Waste Compost
Food waste is becoming serious economic and environmental issue in the world, taking the United States for example, up to 40% of food goes uneaten according to the Natural Resources Defense Council. The New York City made new rules stipulating that large businesses’ leftover food will no longer be destined for landfills. This further pushes the development of food waste compost fertilizer.
food scrap compost facility at street level in New York City
Food scrap compost has several benefits that includes improving water holding capacity helping to reduce water loss and leaching in sandy soils, increases infiltration and permeability of heavy soils reducing erosion and runoff, improving soil structure, porosity and density thus creating a better plant root environment.
▽ Municipal Solid Waste Compost
Municipal solid waste is suitable for composting because of the presence of high percentage of biodegradable organic matter, acceptable moisture content and C/N ratio in the waste. Composting could turn large volumes of MSW into material to be used as fertilizer, organic soil additive and crop substrate. It is tested that municipal solid waste compost, as an organic soil additive, can be used in agricultural production. It supplies soil with considerable amount of essential nutrients. With such benefits, MSW compost are frequently used in agriculture to meet crop N requirements and for the addition of organic matter.
Compared with effectively management of organic waste, it is also essential to emphasize on producing better quality MSW compost. This requires facilities to make modifications during their operation, particularly in the type of feedstock, front-end process, and municipal solid waste composting process.
▽ Palm Oil Waste Compost
The palm oil industry generates large amount of biomass waste such as oil palm empty fruit bunch (EFB) and palm oil mill effluent (POME). Bio-composting the biomass with other organic materials not only offers oil palm plantations a cost-effective and environmentally-friendly solution to dispose of their waste, but also provides another product with saleable value. Composting is an effective and fast treatment method to recycle palm oil waste and to produce EFB compost-a valuable agricultural input. The value of EFB compost as a fertilizer has been proven repeatedly, and it’s one of the best in the market, meaning that the by-products of the palm oil industry can also be sold; leading to even lower costs and helping mills maintain a competitive edge.
▽ Mushroom Compost
Mushroom Compost is the growing medium that results from the mushroom growing process. It is also a great organic amendment for enriching the soil used to grow fruits, vegetables, and even flowers.
Raw materials to make mushroom compost usually are agricultural materials, for example cottonseed meal, cocoa shells, gypsum, poultry litter, hay, straw, horse bedding etc.. Additional materials like gypsum, peat moss, lime, soybean meal, and various other organic items may be added to the compost as well.
What can be Composted? What not?
Actually we have posted an article “Compostable Materials around us – What to Compost” to list what materials can be composted and how to classify nitrogen-rich materials and carbon-rich ones.
Here we would like to list more valuable organic materials that can be composted in both home composting and commercial composting, and what cannot be composted.
◆ Carbon rich – This includes materials such as Alfalfa meal and hay, Buckwheat straw or hulls, Cardboard, Cocoa hulls, Cornstalks, corn cobs, Dryer lint, Grape pomace (winery waste), Dried Grass clippings, Hedge Clippings, Hops (brewery waste), Sawdust and wood shavings, Nut shells, Oak leaves, Oat straw, Paper, Peanut hulls, Peat moss, Pine needles and cones, Tea leaves, Vetch, Weeds, Wheat straw
◆ Nitrogen rich – This includes materials such as Algae, seaweed and lake moss, Apple pomace (cider press waste), Banana peels, Clover, Coffee grounds (and filters), Cotton Bur, Cowpeas, Feathers, Flowers, Fruit peels (not limes), Green Grass clippings, Hay, Leather (leather waste), Manure from herbivores (cow, horse, pig, sheep, chicken, rabbit), Vegetable peels and scraps
◆ Neutral – Ashes (wood, not coal), Beverages, kitchen rinse water, Egg shells,
Black walnut tree leaves or twigs;
Coal or charcoal ash;
Dairy products (e.g., butter, milk, sour cream, yogurt) and eggs;
Diseased or insect-ridden plants;
Fats, grease, lard, or oils;
Meat or fish bones and scraps;
Pet wastes (e.g., dog or cat feces, soiled cat litter);
Yard trimmings treated with chemical pesticides.
Home Composting & Commercial Composting
Home Composting: due to lower volumes of waste collected from household, home composting may lead to reduced waste management fees, and it produces compost for private gardening use. However, not all household waste suit for home composting. It is recommended to separately collect organic household waste with a dedicated waste collection system and subsequent treatment in industrial composting or AD plants to produce quality compost.
|Compostable items in home composting||Items not suitable for home-composting|
|shredded paper, fresh green plant trimmings, rabbit food (alfalfa), leaves, vegetable and fruit scraps, coffee, egg shells, flowers, vacuum dust, cardboard||meat and fish, grease, herbicide or pesticide treated plants, magnolia leaves and pine needles (very slow), coal ash (wood ash is OK), diseased plants, invasive weeds, grass clippings, dairy products, pet droppings, synthetic chemicals, metals, plastic and glass|
Commercial Composting: Many organic wastes, like meat or bio-plastics (including compostable foodservice products), can only be composted under ideal composting conditions. Therefore, the composting of above-mentioned non-compostable materials in household scale, such as meat, fish, pine needles, can be taken place in commercial composting plants, where controlled conditions (e.g. temperature, aeration, humidity) are given. Home-composting should only be considered as an additional option for the treatment of organic waste, especially for garden waste. Commercial compost facilities mainly process organic material from homes, apartments, condominiums and businesses.
Commercial composting methods include in-vessel composting, turned windrow composting, aerated static pile composting.
a process in which compostable material is enclosed in a drum, silo, bin, tunnel, reactor or other container for the purpose of producing compost.
High capital investment, usually municipal or governmental systems. Short compost cycle.
Raw materials: Municipal Solid Waste, Biosolids, Manure, Agricultural Crops and Food Wastes, Industrial Waste etc.
The turned windrow composting is the fastest way to make compost on a large scale. Organic solid wastes are dumped on open land in windrows, and turned 2-3 times per week to break up organic materials, re-establish porosity and re-wet the compost. The complete process may take 4 weeks.
Lower capital investment, lends itself to custom blends, lower capacity restraints.
—Aerated static pile composting:
This composting method provides adequate oxygen and control of pile temperature by adjusting the amount and direction of airflow. 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.
High capital investment, low labor requirements, questionable results
We can conclude the benefits of compost as:
★ improving soil structure, root grow, soil water-holding capacities.
★ holding its nutrients in organic or slow release form.
★ aiding in necessary microbial activity in the soil etc.
★ Compost helps to recycle animal manure, agricultural waste, food waste, municipal solid waste, and reduces landfill waste, to a great extent, composting prevents organic waste from releasing methane in the landfill.
★ Compost delivers essential nutrients over an extended period of time for optimal plant growth. There are so many beneficial microorganisms in compost, which helps prevent plant disease and breaks down organic matter.