Composting
Compost is a collection of organic materials such as leaves, twigs, soil, and food scraps among other materials that is turned into fertilizer. Compost has to go through a composting process before it can be useful. This process requires organic material, water, bacteria, and sometimes oxygen[1] Composting is final once the material is completely broken-down with the help of microorganisms. There are two forms of composting: anaerobic and aerobic.
The Importance of Composting
When organic material is sent to landfills, that could otherwise be composted, it contributes to methane emissions in the atmosphere and takes up land space[2] Food waste is a major issue and 30-40% of the United States' food supply ends up as waste[3]Although reducing waste from the start is crucial, compost can be used as a means to combat this issue.
Anaerobic Composting
Anaerobic composting does not require any oxygen. This process is comparable to the breakdown of waste in landfills, however this process emits much less greenhouse gases[2]. Anaerobic composting is also known as cold composting. Cold composting doesn't generate the heat that aerobic composting does[4].This type of composting can be expensive because of the machinery that is needed to compost correctly. Cold composting needs a closed system so that any methane that is released can be trapped, stored, and later used for energy. This closed container is known as a digester. Although cold composting is more expensive, it requires less maintenance since it does not need to be churned [2]. Cold composting, in return, can take up to 2 years to fully breakdown and decompose. Most municipal waste compost facilities utilize this method of composting[5],[6]. Pathogens can still be left in cold compost since it does not reach high enough temperatures to rid the organic material of pathogens[4] Pathogens can occur from fungi or bacteria, and common pathogens in compost include Aspergillosis, farmer's lung, tetanus, and E. coli. Aspergillosis is a fungus that can affect the lungs and is found in rotting plants. It is typically not life threatening, but can be if an abundant amount of spores are inhaled. Farmer's lung can occur from bacteria or fungus and has similar symptoms to pneumonia. Tetanus is common in soil bacteria and can affect the central nervous system[7] E. coli is a bacteria and affects the intestines[8] To avoid contracting these pathogens, it is important to wear protective gear such as gloves and masks when spinning or working with compost. You should also always wash your hands after working with compost[7].
Aerobic Composting
Aerobic composting works at a much faster rate and is considered hot compost because of the high temperatures it can reach[4]. This type of composting requires oxygen, and therefore must be spun every few weeks or when new organic material is added. Aerobic composting is much more common for household-use because it is fairly in-expensive. Compost bins can be easily created at home or purchased[2]. With hot composting, it is important that moisture and oxygen level are kept balanced. Hot composting will not easily spread pathogens because they are killed off from the heat. By spinning the mixture and balancing the oxygen and water intake, microbial activity will increase and reach, at minimum, 60° C(140° F)[9].
Making Compost
Compost is very versatile as it can be made with many different organic waste materials, such as food, green, and manure waste. Food waste is most common for at-home-compost and consists of food scraps. Green waste comes from plants and manure-based compost as it’s gathered from animal fecal matter. The carbon to nitrogen ratio is important in making compost. Therefore, it is necessary to alternate between the "browns" and "greens" layers. The browns include dead leaves, soil, and twigs. This layer supplies the carbon needed and the greens layer supplies nitrogen. The greens layer can consist of plant material and food scraps. The layers should be 1:1 to produce the best compost. Increasing the surface area of the organic material, by chopping up or breaking into small pieces, speeds up the decomposition process[1]. Aerobic compost needs to be turned every few weeks or when new material is added as it supplies oxygen. Moisture is also key to a good compost mixture. Moisture creates a livable environment for microorganisms to thrive as water transports material around in the mixture so that it is accessible to microorganisms. If a mixture is too dry, water can be added manually or with rainfall[9] If the mixture is too wet, spinning or adding more browns can improve it[1]. Meat scraps and animal feces should not be added to at-home compost since it creates pathogens that can not be dealt with by the generated heat and it can also attracts pests[4]
Types of Compost
| Benefits | Disadvantages |
|---|---|
| Easy to accomplish | Only ideal for small scale waste |
| Requires a great deal of time |
Onsite Composting
Onsite composting requires little effort and should only be used for small amounts of yard or food waste. It is a longer process than most other types of composting, and it can take a few years to fully decompose. Most onsite composting is anaerobic, but can be aerobic if it is spun[6]
Vermicomposting
| Benefits | Disadvantages |
|---|---|
| No spinning required | Worms require maintenance |
| Only ideal for small-scale waste |
Vermicomposting uses worms to break down simple food scraps like food and vegetable scraps, coffee grounds, and tea leaves and tea bags. Food waste that is thick or high in fats and oils is not good for vermicomposting. The composting bin should not be made out of metal because it can get too hot for the worms. Red wiggler worms thrive on this type of compost-soil and are great for vermicomposting[10] Using a pound of worms can create castings or quality compost when they break down the material. These castings can be used as potting soil or plant fertilizer.
Aerated Windrow Composting
| Benefits | Disadvantages |
|---|---|
| Great for large scale waste | Requires a large amount of land |
| Animal byproducts can be composted | Requires spinning |
This type of composting is typically used by large organizations or local governments because it requires a lot of land space where windrows or rows of organic waste can be turned and aerated. Windrows should be large enough to create enough heat but small enough for oxygen flow (about 4-8 ft. high and 14-16 ft. tall). This is one of the few methods of composting where animal byproducts can be used along with grease[9]
Aerated Static Composting
| Benefits | Disadvantages |
|---|---|
| Great for large scale waste | Requires expensive equipment |
| Does not require spinning |
Aerated static composting is when organic material, excluding animal byproducts and grease, is piled and layered using bulking agents. Bulking agents such as wood chips and newspaper clippings can help with aeration. More expensive forms of aerated static composting use air blowers or fans for aeration[9].
Trench Composting
| Benefits | Disadvantages |
|---|---|
| Easy to do | Requires a lot of land space to dig trenches |
| Does not attract pests | |
| Animal byproducts can be composted | |
| Helps plants' roots |
Trench composting is easy to maintain and involves burying organic waste deep in the ground. This form of compost is odorless and doesn't attract pests since it is buried belowground. Meat products can also be included in this compost. Trench compost helps plant roots conserve water. This method isn't practical to be used often because a lot of land space is needed to constantly dig up holes[4]
In-vessel Composting
| Benefits | Disadvantages |
|---|---|
| Great for large scale waste | Requires expensive machinery |
| Requires knowledge of operating machinery | |
| Requires spinning |
In-vessel composting involves a large silo or drum where organic waste is added. It can store a lot more waste than other methods, but does require expensive machinery. The machinery also requires knowledge on operation of the equipment. This process is usually used in food processing plants and must be turned as well[9].
Uses for Compost
Compost is used as fertilizer or potting soils in gardens. It also provides a solution to limiting landfill use and turns waste into a valuable product. Composting has been more recently used to remediate soils that have been contaminated by hazardous waste or heavy metals[11] Due to the microorganisms involved in compost and their decomposition abilities, compost is a useful remediation tool for degrading toxins[12]Compost has shown to remediate heavy metals the best when in combination with another remediation method. For example, Kohler et. al (2015) found that when seedlings were grown in soils contaminated from mine tailings, they were inoculated with Arbuscular Mycorrhizal Fungi and when combined with compost, plant biomass increased by 64% compared to separate treatments or without any treatment at all[13].
Community Gardens
Community gardens are a great way to increase food security by providing a healthy food source. Compost is often used in these gardens to fertilize plants and remediate soils that may contain heavy metals since community gardens are often utilized in city spaces where soils can be heavily contaminated. It is important to wear gloves and masks when handling contaminated soils.
- ↑ 1.0 1.1 1.2 Misra, R. V., et al. On-Farm Composting Methods On-Farm Composting Methods. Food and Agriculture Organization of the United Nations, 2003.
- ↑ 2.0 2.1 2.2 2.3 Gotaas, Harold. “Composting: Sanitary Disposal and Reclamation of Organic Wastes.” World Health Organization Monograph Series, no. 31, Oct. 1956, pp. 57–59, https://doi.org/10.1016/s0033-3506(56)80025-5.
- ↑ Diakubama, Plamedi. Food Waste in American Households. Sept. 2021, pp. 1–12, scholarworks.seattleu.edu/cgi/viewcontent.cgi?article=1030&context=alfie-conferences. Accessed 2022.
- ↑ 4.0 4.1 4.2 4.3 4.4 Lin, Long, et al. “Improving the Sustainability of Organic Waste Management Practices in the Food-Energy-Water Nexus: A Comparative Review of Anaerobic Digestion and Composting.” Renewable and Sustainable Energy Reviews, vol. 89, June 2018, pp. 151–167, https://doi.org/10.1016/j.rser.2018.03.025.
- ↑ US EPA. “Types of Composting and Understanding the Process | US EPA.” US EPA, 30 Apr. 2019, www.epa.gov/sustainable-management-food/types-composting-and-understanding-process.
- ↑ 6.0 6.1 Salah El Haggar. Sustainable Industrial Design and Waste Management : Cradle-To-Cradle for Sustainable Development. Burlington, Elsevier Science, 2010.
- ↑ 7.0 7.1 Pleasant, Barbara, and Deborah L Martin. The Complete Compost Gardening Guide. Storey Publishing, 1 Jan. 2008.
- ↑ Hess, Thomas F., et al. “Heat Inactivation OfE. ColiDuring Manure Composting.” Compost Science & Utilization, vol. 12, no. 4, Sept. 2004, pp. 314–322, https://doi.org/10.1080/1065657x.2004.10702200. Accessed 11 May 2020.
- ↑ 9.0 9.1 9.2 9.3 9.4 Bernal, M.P., et al. “Composting of Animal Manures and Chemical Criteria for Compost Maturity Assessment. A Review.” Bioresource Technology, vol. 100, no. 22, Nov. 2009, pp. 5444–5453, https://doi.org/10.1016/j.biortech.2008.11.027. Accessed 18 Dec. 2019.
- ↑ Kumar, Anil, et al. “Potential of Vermicompost for Sustainable Crop Production and Soil Health Improvement in Different Cropping Systems.” International Journal of Current Microbiology and Applied Sciences, vol. 7, no. 10, 10 Oct. 2018, pp. 1042–1055, https://doi.org/10.20546/ijcmas.2018.710.116. Accessed 8 Apr. 2022.
- ↑ Farrell, Mark, and Davey L. Jones. “Use of Composts in the Remediation of Heavy Metal Contaminated Soil.” Journal of Hazardous Materials, vol. 175, no. 1-3, Mar. 2010, pp. 575–582, https://doi.org/10.1016/j.jhazmat.2009.10.044. Accessed 9 Dec. 2019.
- ↑ Kumar, Vineet, et al. “Bioremediation: An Eco-Sustainable Approach for Restoration of Contaminated Sites.” Microbial Bioprospecting for Sustainable Development, 2018, pp. 115–136, https://doi.org/10.1007/978-981-13-0053-0_6.
- ↑ Kohler, A., Kuo, A., Nagy, L. et al. Convergent losses of decay mechanisms and rapid turnover of symbiosis genes in mycorrhizal mutualists. Nat Genet 47, 410–415 (2015). https://doi.org/10.1038/ng.3223