Food waste management: an overview of aerobic digestion

April 29, 2024

4 minutes, 47 seconds read

Food waste management: an overview of aerobic digestion

Aerobic digesters have emerged as a popular solution for responsibly disposing of organic waste. By understanding how an aerobic digester works, organizations can more effectively determine if this solution is right for them. 

Below, we will provide an overview of: 

  • How an aerobic digester works, including how long the digestion process takes.
  • The important distinction between aerobic and anaerobic digestion. 
  • The types of materials an aerobic digester can effectively break down. 
  • An aerobic digester’s impact on the environment. 

What does an aerobic digester do?

An aerobic process is one that requires oxygen. An aerobic digester is a piece of equipment that introduces oxygen into the process of breaking down organic waste. 

This decomposition process happens when natural microorganisms are introduced into the equipment. These microorganisms – typically a blend of fungi, bacteria, and enzymes – replicate the decomposition process that occurs in nature. It is because of these naturally occurring microorganisms that aerobic digesters are referred to as biodigesters.

Aerobic digesters are usually installed directly in a commercial food preparation area to simplify the sustainable disposal of food waste. To operate, the equipment requires electricity and a drain connection.

Steps of operation for an aerobic digester

Operating an aerobic digester is fairly simple. Steps of the process include: 

  1. Food waste, water, and additives are placed to the aerobic digester. (While the equipment is sealed to reduce noise and odors, waste can be added at any time.) 
  2. Arms inside the aerobic digester turn the organic waste, ensuring the even distribution of oxygen. To allow microbes to eat, and minimize energy use, these arms only turn for a quarter of the operation time. 
  3. Microorganisms eat the organic waste, creating two byproducts: carbon dioxide and wastewater that is sent to the sewage system through the drain connection. 

The length of time to complete this assisted decomposition process will vary based on the materials being digested. Depending on its size and capacity, an aerobic digester may be able to fully break down a load of organic waste in as little as 24 hours. Equipment sizes vary, ranging from the capacity to consume 10 kg (20 lb) to as much as 6,000 kg (13,200 lb) of organic waste each day. 

What is the difference between anaerobic and aerobic digestion?

The emphasis on oxygen in the organic waste digestion process is significant. When oxygen is removed from the decomposition equation, methane-producing bacteria take on the task of breaking down organic waste. This process is known as anaerobic digestion. 

While carbon dioxide may be better known as a greenhouse gas, methane emissions have proven to be more problematic. To begin with, methane has a global warming potential that is 84 to 87 times greater than carbon dioxide over a 20-year period. In addition, attempts to capture methane emissions are limited. In landfills, which are among the leading sources of methane emissions, some operators trap the gasses to convert them into electricity or a liquified natural gas. However, it remains common to burn excess amounts of methane, sending pollutants into the atmosphere. 

What can you put in an aerobic digester?

Aerobic digesters provide versatility in the type of organic waste they can handle. A good rule of thumb is that a biodigester can break down anything that a human stomach can digest. Like a human stomach, some items may take longer to digest than others. 

In general, an aerobic digester is able to break down the following types of organic waste

  • fruit and vegetables
  • bread and dairy products
  • small nuts, such as almonds
  • meat and small fish bones
  • grease and fat

More fibrous fruits and vegetables, such as broccoli, cabbage, and carrots, may take longer to break down. Shells, hard bones, fruit pits, and vegetable husks should not be placed in an aerobic digester. 

Are aerobic digesters good for the environment?

There are numerous reasons to invest in an on-site aerobic digester, including the cost savings that come from reducing the amount of waste being sent to the landfill. However, many organizations make the decision to install an aerobic digester for its environmental benefits. 

Due to the landfill’s methane problem, organizations, as well as state and local governments, are pushing to reduce the amount of organic waste sent to the landfill. As noted above, methane has a greater impact on climate change than carbon dioxide. But methane’s shorter lifespan also means that its impact on the climate is more immediately reversible than is the case with carbon dioxide emissions. 

Breaking down organic waste on-site also reduces the emissions generated when transporting waste to landfills. While many regulations have pushed consumers and businesses to consider composting their organic waste, on-site composting is not always feasible. As a result, organizations may still be transporting organic waste off-site, and generating fossil fuel emissions in the process. 

Another benefit of aerobic digesters is that this equipment can be used to advance conversations around the impact of food waste on the environment. Some aerobic digesters, like Power Knot’s LFC biodigester, are able to track the types and amount of waste broken down. This data can guide purchasing decisions and menu changes. It can also be used to communicate the scale of a food waste problem to customers and stakeholders. 

Decide if an aerobic digester might be right for you

Organizations looking for a more sustainable way of managing and disposing of their food waste may find an aerobic digester to be an excellent addition to their kitchen. That’s because, in addition to its environmental characteristics, aerobic digesters can be cost-effective and easy to operate. To learn more about the advantages of an LFC biodigester, contact Power Knot with questions.