On-site biodigesters may look like high-tech kitchen equipment, but at heart, they are simply a sealed vessel for natural processes. As a result, it may be tempting to think of biodigesters as being similar to processes such as composting, with similar material being disposed into these machines that are usually installed in the kitchen. The truth is, however, that a biodigester provides organizations with large food preparation areas far more flexibility than composting and other options for the disposal of food waste. Below we describe what can and cannot go into a biodigester. 

How a biodigester works

On-site biodigesters are designed to accelerate the decomposition process that happens in nature. The process begins by introducing suitable organic waste and naturally occurring microorganisms in an oxygen-rich process. 

These biodigesters run continuously to avoid any accumulation of waste. This allows some biodigesters to completely digest food waste within as little as 24 hours. Equipment ranges in size, being able to consume from 9 to 6,000 kg (20 to 13,200 lb) of food waste in a day, making it a solution that works for organizations of all sizes that prepare food. 

This rapid process is one of the chief advantages biodigesters offer over other environmentally friendly organic waste disposal methods. Composting, for example, takes anywhere from four weeks to 12 months to fully break organic matter down into usable fertilizer, depending on the type of input and time spent attending the compost. This lengthy timeline is one reason that ample space is needed for composting, as compared to a compact on-site biodigester.

What you can put in a biodigester

Biodigester can digest anything that a human stomach can. While certain items may take somewhat longer to digest, in general the items listed below can be put broken down by an on-site aerobic biodigester:

  • Fruit and vegetables, including more fibrous items such as cabbages, broccoli, and onions.
  • Bread and dairy products; this is an added advantage over methods such as composting, as bread and dairy will attract pests to outdoor compost areas. Fully sealed on-site biodigesters actually eliminate the likelihood of attracting pests.
  • Small nuts, such as almonds
  • Meat and small fish bones; this is another item that is usually never composted due to the likelihood of attracting pests
  • Grease and fat

Needed microorganisms to add to your biodigester 

There is one more critical ingredient that must go into your biodigester, and that is the naturally occurring microorganisms that speed the decomposition process. Power Knot supplies these microbes in the form of Powerzyme, a formula that contains the appropriate balance of bacteria, fungi, and enzymes. For LFC biodigesters, these microbes are typically added once each year. Other brands of biodigesters may require more frequent addition of helpful microbes to effectively break down food waste.  

These naturally occurring, non-pathogenic microorganisms are carefully formulated in a laboratory to ensure the materials pass stringent quality control tests to prevent the presence of salmonella, shigella, or coliform bacteria. They pose no danger to piping or wastewater treatment plant equipment. Within kitchen operations, Powerzyme microbes can be wiped up and washed off with soap and water if needed. Moreover, these microbes play a critical role in eliminating potential odors.

What you should not put in a biodigester

While a biodigester will significantly cut down on the amount of food waste that goes into the garbage, there are certain items that cannot be broken down by this equipment. A brief list of items that cannot be digested includes: 

  • Shells, such as oyster or mussels
  • The large seeds from certain fruit and vegetables, such as peach or avocado pits
  • The hard husks of certain fruit and vegetables, such as coconut husks
  • Plastics, such as plastic bags 
  • Papers, such as napkins or other nonorganic waste
  • Ice or boiling water; the addition of frozen or boiling water can kill or severely degrade the operation of the microbes within the equipment

What a biodigester produces

All of the food waste input is broken down by a biodigester into wastewater that can safely be disposed of down the drain into the sewage system. As an alternative, some organizations find that this gray water can be used for irrigation, providing an extra layer of sustainability to their operations. There is no further residue that staff needs to remove or clean from the equipment. 

What does this mean?

A biodigester will not eliminate all need for waste disposal, but it does provide many organizations that have large food preparation areas a sustainable solution for breaking down food waste. It not only provides more flexibility in terms of input when compared to traditional disposal alternatives such as composting, but it also provides benefits using a simple process change that better supports staff. 

To learn more, contact Power Knot.