Pretreatment Technologies

 

definition

Pretreatment technologies are systems that liquefy or size-reduce food waste, often using enzymes or microbes and heat. 

project, phase 1

Phase 1 of our work in pretreatment technologies culminated in a workshop on equipment fundamentals for the New York Department of Sanitation's NYC Food Waste Fair. The presentation walks through the role of pretreatment equipment in food waste diversion, as well as technical considerations and the due diligence questions users should be asking vendors.

Project, phase 2

Coming Soon: Guide to Pretreatment Strategies and Technologies

 

What is a pretreatment system?

 

Pretreatment technology is the umbrella category for a range of systems, that as mentioned above, generally process food waste by grinding and shredding material, applying heat, and/or using enzymes or microbes. Encompassing biodigesters, liquefiers, dehydrators, and accelerated composting systems, these technologies can play an important role in food waste diversion programs, particularly in dense urban areas.

Biodigesters and liquefiers are 'down-the-drain' systems that convert food waste into wastewater effluent, which is then directed into sewer systems for further treatment at waste water treatment facilities.

Effluent from food waste often has high levels of total suspended solids (TSS) and biochemical oxygen demand (BOD), so it is critical to ensure third party verification demonstrates that a given technology complies with municipal or city TSS and BOD limits. Certain localities charge substantial permits for increased sewage discharge due to increased processing demands on wastewater treatment facilities.

Dehydrators and accelerated composting systems rely on heat and often use microbes or enzymes to significantly volume-reduce food waste to produce a substance that may be suitable as a soil amendment, with water as a byproduct. Once dehydrated, food waste typically makes up 10-20% of the initial volume, which can be a significant benefit to dense urban generators by simplifying storage and collection for off-site composting and lowering labor costs.

The end product that dehydrators and accelerated composting systems produce may be biologically active and vendors should supply third-party verification showing no trace measurements of Salmonella or Fecal Coliform. Similarly, to directly apply a technology's end product to soil, it is critical to not only verify commonly measured attributes like pH and organic matter content, but important to examine the maturity and stability of the end product to ensure the product will not be damaging to plant life. Maturity and stability are assessed through carbon dioxide and free ammonia testing by requesting Solvita or US Composting Council Seal of Testing Assurance results.

For an authoritative guide on technical considerations of systems that are on the market, read the Center for EcoTechnology's On-Site Systems for Managing Food Waste.

 
 

Need-to-Read Articles

 
Pretreatment systems can play an important role in food waste diversion, but you want to approach them thoughtfully.
— James Ewell, Senior Director of Sustainable Materials, GreenBlue