03 Jun Picking a Food Waste Processing System: Part Two
This blog is part 2 of a two part blog. To find part one, click here.
While the food waste problem in America is a rather complex and difficult one to solve, perhaps it is a small mercy that there are only a few basic categories of food waste disposal systems on the market today. Three, in fact: non-biological (mechanical) systems, in-vessel dry composters, and biological (wet) systems.
This blog post will attempt to briefly outline each of the three categories and provide popular examples of each. For a more in-depth exploration of the topic, check out this 54-page document commissioned by the government of Massachusetts which delves much deeper into the nitty-gritty details.
As you embark on your journey into the world of on-site food processing systems, it’s advisable to examine each of the systems while actively assessing the following variables:
- Calculate return on investment based on current waste hauling costs and the electricity, water and sewer use of the particular system.
- Calculate physical space and utility requirements of the system.
- Conduct a waste audit to help your business understand your waste profile and develop systems to ensure that “pure” food waste is available for the on-site system. Many recycling centers will provide a free waste audit upon request.
- Consider likely points of failure of an on-site system and develop contingency plans.
- Decide how the end product of on-site systems will be managed with an eye to prepare it for beneficial reuse.
Non-biological or Mechanical Systems
The first category of system is the non-biological (or mechanical) system. This type of system uses mechanical processes and heat to reduce the weight of food waste by removing the water content. This category can be broken down into two basic types: pulpers/shredders and dehydrators.
A pulper or shredder system starts by pulverizing food waste, after which it will remove the water content (and therefore most of the weight). A pulper will reduce the waste to a slurry before removing the water, whereas a shredder simply grinds the waste and then presses it. Each type of system generally reduces the weight by around 80-90%, and is typically found in or near either the food processing or dishwashing area.
One major benefit of having a pulper or shredder system is that generally they can accept non-organic products in addition to the organic materials, thereby eliminating the need for food workers to more painstakingly sort the two away from each other.
A downside of this type of system in isolation is that the resulting reduction has to either be refrigerated or picked up frequently due to the unpleasant odor that tends to attract pests.
Dehydration systems use heat in order to render organic material into a sterile, odorless material. Oftentimes this system will be used in conjunction with a pulper or shredder in order to maximize the space available within the dehydrator, and thereby reducing the resultant waste even more efficiently.
The resulting product from a mechanical process is not suitable for compost, however, and requires further treatment before it can be used as a fertilizer.
In-Vessel Dry Composting
The second category of on-site food processing systems is in-vessel dry composting. This uses a biological process in order to heat and break down organic material into a nutrient-rich product that can be used as fertilizer.
At their most basic, composters are simply enclosed containers which allow for natural processes to take place in a limited area; but, as the size increases, different levels of technology are necessary to control them with a regulated consistency.
To begin the process, clean and separated organic materials are loaded into the enclosed container, after which controlled air is moved through the chamber in order to increase oxygenation. If the material is too wet to allow an air flow, the addition of “brown material” such as wood chips, paper, or sawdust must be added. Heat and microorganisms are then introduced, in conjunction with automated rotation and aeration, in order to catalyze the process into performing much more quickly than would occur under natural conditions. The material is then cooled and cured, yielding a product that is (once tested, and treated if necessary) usable as fertilizer.
The major benefit of composting is that it produces a “zero waste” or “full circle” product, which, if utilized, will result in the entirety of the waste being recycled back into the food production system.
Some downsides of a composter include the additional effort of sorting food waste in order to make sure they everything included is compostable, proprietary microorganism formulas, as well as the relatively larger size of the container (since the waste isn’t compacted so much as converted). Additionally, if a business or institution does not have a way to utilize the resulting compost, there remains the issue of disposal fees.
The third and final category is a wet system, or anaerobic biodigester, which maintains internal temperatures, oxygen levels and integrates fresh tap water in order to break down food wastes into a fully-filtered effluent, or “gray water,” which is then deposited into the municipal sewer system. By introducing proprietary blends of enzymes, microorganisms, nutrient blends, or a mixture thereof, a biodigester functions much like a metal stomach by moving the food waste around a water mixture until it fully breaks down. This continuous process varies a bit among manufacturers, and can exist either within the food processing facility or outside of it.
Along with composters, biodigesters end up with a “zero waste” product, and is considered to be “biogenic” (part of the natural cycle in which carbon returns to the system that originally produced it).
The primary advantages of wet systems include the decrease in plastic bags for disposal, the avoidance of additional chemicals for pest control, the increase in the ability to more closely measure the effectiveness of the system, as well as the elimination of any odor that might accompany many of the other systems.
The drawbacks of wet systems include the significant investment up front, as many wet systems require a more customized approach to full integration. Additionally, some models of biodigesters have been criticized for being inconsistent with the amount of unacceptable contaminants present in the final effluent, which run contrary to the claims of the companies in question and can even run higher than the maximum municipal limits.
Although the categories of on-site food processing systems are relatively limited, there are many considerations when making a final decision as to which of the systems would be most effective for your specific situation.