As governments, large companies, and other organizations become increasingly aware of the importance of sustainable practices, aerobic and anaerobic digestion have come to the forefront as two potential solutions for food waste management. While both aerobic and anaerobic digestion are types of methods to deal with food waste, they involve different processes, produce different byproducts, and ultimately have different challenges and benefits.
This guide will explain exactly what these processes are and how they can improve your food waste practices and compare the benefits of each. Aerobic and anaerobic digestion offer numerous advantages beyond waste reduction; by understanding the process, you can work towards making your business operations more efficient, cost-effective, and environmentally friendly all at once.
Aerobic and Anaerobic Digestion Methods
When we think of ways to deal with food waste we usually think of composting, a process in which organic matter, like food scrap, is broken down and turned into a fertilizer that can enrich soil and plants. Like traditional composting, both aerobic digestion and anaerobic digestion work to decompose food waste. However, each process results in a byproduct besides fertilizer – gray water for aerobic digestion, and biogas for anaerobic digestion. Keep reading to learn about how each process works.
What Is Aerobic Digestion?
Aerobic digestion is a process that breaks down organic waste in aerobic environments – environments where oxygen is present. Because aerobic digestion happens in the presence of oxygen, it’s a more efficient process than anaerobic digestion, and it happens much faster.
Like composting, aerobic digestion begins with food waste or other organic matter. This food waste is introduced to aerobic microorganisms (ones that survive in environments with oxygen), which break down the food waste over time. Aerobic digestion results in byproducts of water and a small amount of carbon dioxide.
While aerobic digestion happens in nature in a variety of environments, such as wetlands, technological advancements have found a way to speed up the digestion process. Machines called aerobic digesters accelerate this natural process, breaking down food in just 24 hours! To use an aerobic digester, food waste is added to the reaction chamber, along with microorganisms and enzymes that digest waste in the presence of oxygen. Air and water are added to the machine, and the decomposition process takes place. The only byproduct? Gray water that can be discharged into municipal sewage systems.
Aerobic digester machines help reduce the impacts of food waste on climate change, as they help divert food that would otherwise release methane in landfills. This accomplished by processing food waste through an aerobic digester instead of sending it to landfills, instead the food is broken down without releasing large amounts of potent greenhouse gas. Installing an aerobic digester on site also helps reduce waste-disposal costs.
What Is Anaerobic Digestion?
Anaerobic digestion is the process of breaking down organic materials without oxygen. It occurs in an oxygen-free environment, where anaerobic microorganisms digest food sources like animal manure, human sewage, and, of course, food waste. In the process, these microorganisms also release methane gas and carbon dioxide.
Anaerobic digestion occurs naturally in landfills, where waste is buried and not exposed to air. This means that landfills are a primary source of methane emissions that result from anaerobic digestion. While anaerobic digestion in landfills contributes to climate change, new technologies allow us to harness the process to create renewable energy from these gas emissions instead. This valuable renewable energy or “biogas” created through anaerobic digestion of food waste can then be used as an alternative fuel source. Aerobic digestion sometimes also results in the production of fertilizer.
Anaerobic digestion for the production of biogas takes place in an anaerobic digester, a sealed reactor that contains microbes that can break down food waste and produce biogas. The process usually takes place in a dedicated anaerobic digestion facility.
Which Is Better, Aerobic or Anaerobic Digestion?
There are benefits to each process, and ultimately, it’s best to manage your food waste in the way that best meets your needs. Here’s a comparison of the main benefits and challenges of aerobic and anaerobic digestion.
Aerobic digestion is popular because it is faster, and it doesn’t release the methane like that anaerobic digestion does. As a result, it lacks the powerful smell that is frequently associated with anaerobic digestion plants. The byproduct of aerobic digesters, gray water, is also easier to manage because you can simply discharge it into your local sewage system (whereas anaerobic digestion requires a complex process to harness methane emissions)
Anaerobic digestion is popular because it has a valuable output, biogas, which can be captured and used for heating, electricity generation, and even car fuel. That said, most businesses that send their food waste to an anaerobic digestion facility don’t see the financial gains themselves. Aerobic digestion does not produce a useful product. Both processes avoid the negative byproducts of conventional disposal methods such as dumping or burning.
While both approaches work to address waste management, many organizations that produce large amounts of food waste are turning to aerobic digester machines because they are easy to implement. These machines offer a cleaner, faster, and more convenient method of dealing with food waste at the source, as they can be installed on-site. This not only makes it easier to deal with food waste before it begins to smell, but also can reduce the costs associated with transporting waste off-site (like you would to transport food waste to an anaerobic digestion facility).