With all that has been written about grease interceptors in recent years, one might assume that manufacturers would be active in promoting the positive environmental value and impact of these devices.
   Unfortunately many plumbing contractors, wholesalers, and restaurant owners don’t view grease interceptors in a positive light. In new commercial kitchen construction, the owner is told he needs to get one because the plumbing inspector claims, “It’s in the building/plumbing code.” In existing kitchens, maintaining the unit is typically seen as a hassle and a needless business expense. Eventually the local pretreatment coordinator discovers your failing unit and tells you to replace it or risk fines because “It’s in the pretreatment regulations.”
   To date, the use of grease interceptors has been so code-driven that quite often the foundational reasoning behind the codes and regulations is forgotten. As a result, the true value of a grease control device is often overshadowed by the necessity to simply comply with the code.

The True Value
Putting the code-driven aspects aside, what is the true value of grease traps and interceptors? Without quibbling over which technology works better, every commercially available device, when operated and maintained properly, removes some portion of fats, oil, and grease from the kitchen effluent. How they accomplish this and their efficiency of pollutant removal are often vigorous topics of debate within the industry, but they all do, in fact, work. 
   By keeping FOG out of the sanitary sewer system, the opportunity for grease-related blockages and resulting sanitary sewer overflows can be minimized. This is critically important, as raw sewage spewing from sewer overflows poisons the watershed, has dire implications to public and wildlife health, and also has well-documented negative impact on water-related industries such as tourism and fishing. 
   The environment, people’s health, their livelihood, and quality of life are all positively impacted when restaurants properly utilize their grease interceptors.

From ‘Green’ to ‘Greener’
Even though grease interceptors didn’t start out as pollution abatement devices in the early development years of our modern society, they clearly fill that role today. By the very nature of what they accomplish for society, FOG interceptors have always been a “green” technology. Recent trends in product development show a significant portion of product advancements relate to attaining even higher levels of environmental stewardship and sustainability. 
   In the early 1990s, restaurants chose between two types of grease control devices: large capacity, underground, pre-cast concrete interceptors (now called “Gravity Interceptors”); and in-kitchen, PDI-type grease traps (now called “Hydro Mechanical Interceptors”).
   These two options still dominate the market today due in large part to their effectiveness in the targeted application and their familiarity within plumbing, construction, and regulatory circles. 
   From a regulatory standpoint, the large capacity gravity interceptors are the preferred technology for grease capture throughout the majority of the U.S. If there isn’t enough space outside to install a gravity separator, or if the restaurant serves pre-prepared or pre-packaged food, the regulator may then permit the option of an in-kitchen hydro mechanical interceptor. 
   Several manufacturers have enhanced these basic designs that, while evolutionary for the most part, still represent significant improvements over the basic design and functionality of the older style units.

New Materials and Design
Gravity separators’ capacities most commonly fall somewhere between 500- and 3,000 gallons. These are usually installed outside and underground and occasionally indoor or above ground. 
   Advancements in gravity interceptor design centers on achieving long service life by employing specialized construction materials, highly efficient grease removal through optimal flow dynamics, maximum FOG and solids storage capacity and design consistency. Interceptors incorporating these attributes are more commonly known as a subset of gravity interceptors called “Engineered Gravity Interceptors.”
   While concrete and mild steel have long been the standard materials of choice for grease interceptors, today’s polymers and plastics can provide a longer service life in many applications because the FOG, water, and solids inside an interceptor create a highly acidic, corrosive cocktail. If the interceptor’s tank fails, the interceptor’s contents may leach out into the ground or groundwater could infiltrate the tank. Both situations are trouble for the local regulators.
   Many of today’s manufacturers of newer and greener engineered gravity interceptors are beginning to use more robust materials such as polymers and composites, either for the construction of the whole unit or as an interior and exterior coating, all with an eye toward improving service life because these materials are impervious to the corrosive environment. 
   Steps have also been taken to optimize the performance as well. The configuration of an engineered gravity interceptor has quite often been designed, tested, and tweaked to provide optimal separation at maximum rated flow and full capacity rating and maximum storage of FOG and solids inside the unit. Some units devote more than 50 percent of total capacity for storage. Fewer service calls means a smaller carbon footprint for that activity.
   From a consistency standpoint, all of this is set at the factory so the plumber on the job receives a system that is properly configured to provide optimal FOG and solids separation.

Increased Capacity and Recycling 
The Plumbing and Drainage Institute prescribes the configuration and performance of hydro mechanical interceptors (grease traps). Green advancements go beyond newer materials and include increased grease storage capacity and the ability to recycle brown grease.
   Some manufacturers have taken the functionality of a PDI trap and super-sized the FOG storage capacity beyond the minimum requirements of PDI. The result is a unit that can be operated with longer periods between servicing. This has become a viable option for restaurants that have more space than what is typically available for trap installation. Here again, fewer service calls can reduce the overall carbon footprint around the unit.
   Over the past several years the use of automatic grease removal devices has been on the rise. These units are active rather than passive—they use electricity to run a heating element and a moving, skimming mechanism that removes grease from a kitchen wastewater stream. Here again, this is a viable alternative when more than a standard hydro mechanical interceptor is required but space is severely limited. High removal efficiency and the ability to capture and recycle brown grease are touted. The brown grease is being used increasingly to make biodiesel fuel and as a nutrient source in other energy-producing processes.

Putting it all Together
Grease interceptor manufacturers are continuing to improve and enhance the functionality, performance, and “greenness” of interception devices. This has been borne of necessity, because municipalities must protect their already overloaded sanitary sewer systems. 
   Of equal importance is the realization by the food service industry that grease interceptors must be serviced regularly and do their part—from a kitchen best management practices standpoint—to keep FOG and food solids away from the drains. 
   Together, we share the responsibility of doing our part to protect the local watershed.