Composting Standards

Recycling is one of the better solutions to curbing the amount of waste left in landfills, since it allows for the reuse of the artificial materials that would otherwise remain intact and unchanged for thousands of years. However, it alone cannot solve the issue of waste management. According to the EPA, more than half of all municipal solid waste is made up of compostable materials. Composting is a process that acts as organic recycling, and the Earth has technically performed it for billions of years by controlling the decomposition of materials that nourish new organic matter. This greatly reduces the problems generated by landfills, and provides us with a much-needed resource.

There are several primary chemical requirements for the process of composting. Carbon, as the building block of life, is the most important of these and makes up about 50 percent of the mass of microbial cells that break down matter. Nitrogen is also an essential component of this process, providing the organic compounds needed for cell growth and function. To manage these elements properly, it is recommended that anyone working with compost use a carbon-to-nitrogen (C/N) ratio for each of the compost ingredients, with an ideal C/N of 30:1. This amount encourages the growth of microbial populations, but also maintains a high level of carbon once the majority of it is lost through carbon dioxide emissions.

Oxygen gas is a requirement for any kind of aerobic composting.  Without sufficient oxygen to assist in the oxidation of carbon for energy, the process will produce undesirable odors. ASTM D5975-17: Standard Test Method for Determining the Stability of Compost by Measuring Oxygen Consumption measures the amount of oxygen used and produced by a compost sample to determine how well it maintains stability under particular aerobic conditions. Having a clear understanding of the oxygen content of compost is essential to understand if the organic material can be used for its intended purpose in fertilization.

Almost all organic materials can be composted, but there are some that are more ideal than others for the process, especially if they have a higher C/N ratio. Aside from this waste, some kinds of material surprisingly have the potential to become compost. For example, there are some compostable plastics, which are addressed in ISO 17088:2021: Specifications for compostable plastics. These kinds of plastics, just like other compostable materials, should have a large concentration of carbon. This standard addresses a test used to determine the ultimate level of aerobic biodegradation of the test material, the degree of disintegration obtained, any negative effects on the finished compost, and the maximum concentration of regulated metals in the compost. According to the standard, 90% of the carbon in the plastic material should be converted into carbon dioxide by the end of the testing period. This, along with some other specifications, determines the compostability of plastic material.

The different compostable materials are composted in many different methods, of which there are several general categories. Vermicomposting is a basic composting method that uses worms in addition to microbes and bacteria to turn organic waste into a nutrient-rich fertilizer. This process involves placing these worms in a bin with a bedding of shredded paper and food scraps, which the worms eat to create compost. This method creates compost that is very high in nutrients, and is suitable for smaller-scale composting operations, such as in home use.

Either red earthworms (pictured) or red wigglers are ideal for vermicomposting

The other two general types of composting, which can be used on a larger scale, are aerobic and anaerobic composting. The oxygen-rich atmosphere during the aerobic process, microorganisms break down the material to make carbon dioxide (CO2), ammonia, water, heat and humus, the relatively stable organic end product. In the anaerobic process, the dominating microorganisms create methane, organic acids, hydrogen sulfide, and other substances. While anaerobic composting takes much longer than aerobic composting and emits an aggressive odor, it does possess the advantages of needing little maintenance and maintaining greater nutrients overall.

One of the primary benefits of composting is lowering the amount of waste that we introduce into landfills every year. One-third of all food worldwide is wasted, making approximately 18% of the waste stream consist only of uneaten meals. Unlike most of the waste in landfills, which simply sit there for a long period of time, food waste in landfills is broken down by bacteria to produce methane, a greenhouse gas 21 times more potent than carbon dioxide. Making use of this food waste as a composting resource also provides nutrients that allow vegetation to grow, which will offset the carbon dioxide that is emitted during the composting process and the amount that is already in the atmosphere from energy generation.

The use of compost also reduces the need for chemical fertilizer to be used for crop growth. One of the key anthropogenic, ocean-based environmental issues is that of eutrophication, which occurs when an excessive amount of nutrients, particularly nitrogen and phosphorus, are introduced into the maritime ecosystem. This leads to the additional issues of hypoxia, in which the dissolved oxygen levels in water become too low to support most aquatic life, and algal blooms, which also prevents the growth of marine life. Nutrient run-off from farmlands is a major contributor to this issue. Since compost lacks phosphorus in its chemical composition and has a much lower amount of nitrogen than artificial fertilizers, it contributes very little to this problem.

Composting is a logical solution to many of the world’s environmental problems. It can reduce terrestrial, atmospheric, and oceanic damage while providing a steady source of nutrients for growing and harvesting food. However, it is not necessarily something that is in the minds of the public and policymakers. While the availability to compost does appear in certain places, it is still a rarity.

Large-scale composting methods for refuse are not as common as they are for trash and recycling, and it will be a challenge to make them widespread in the near future. In terms of standardization, the primary focus of composting seems to be utilization on a very small scale, such as for a single organization or household, and not for an entire city. Widening this view is necessary to understanding the logistics of managing a larger composting procedure that can successfully manage appropriate wastes.