The New Alchemy
- By Robert Rubin, Ph.D., Edward W. Miles
- Mar 01, 2007
No one really likes brown grease. It is collected in grease interceptors and traps -- not because anyone wants it – but to prevent it from entering wastewater collection systems. Waste haulers remove the brown grease from traps and interceptors and take it to wastewater treatment plants for processing. Most solid matter is removed and, in most cases, taken to a landfill for final disposal.
Across much of the country, land applications are being eliminated, especially for untreated sludge because of lasting effects to groundwater contamination and other environmental concerns. Because of the increasing costs of separating and treating brown grease, many wastewater treatment plants are shutting their doors to this hauled nuisance altogether. The raw, untreated waste can wreak havoc in clarifiers and the overall processing of wastewater.
Because treatment plants increasingly are refusing to accept brown grease, haulers are forced to transport the waste farther from their service areas, and associated costs are causing an economic collapse of their bottom lines. Consequently, wastewater officials are seeing an increase in illegal dumping to stormwater drains, estuaries, competitors’ traps, and open spaces.
Ralph Rogers, president and founder of EcoPlus Inc., sees value in brown grease.
“I saw a problem brewing in the wastewater collection industry and through conversations with my colleagues across the country, I knew this was a national issue,” he said. “The rational solution to legal disposal lies with a cost-effective process that can not only be located in the haulers’ service areas but also allow the wastewater treatment authorities the opportunity to build a revenue stream, and reduce the cost of conventional processing,” Rogers explained.
Garbage to 21st-Century Gold
From 1999 to 2002, Rogers served on a North Carolina study committee dedicated to brown grease issues, where he saw a future full of problems. Subsequently, he not only created a regional interceptor servicing company but also developed the EcoPlus technology and built a plant using it to handle his company’s hauled grease. The patent-pending technology converts sticky fats, oils, and grease along with incorporated food matter, into a granular material. This material may be used as a soil amendment in agricultural applications or as an alternative-energy feedstock.
EcoPlus has been in commercial operation since February 2002 at a fully permitted plant near Charlotte-Douglas International Airport in Charlotte, N.C. The facility processes brown grease from more than 1,800 grease producers in the Southeast.
At the EcoSolve plant, trucks discharge their contents into a concrete offload pit. The grate over the pit scalps off larger trash items, such as straws and tableware. Undersized, high-density debris falls to the tank bottom and is removed periodically. Pumps transfer the balance of the brown grease material from the discharge pit to a mix tank. At this point, a dose of lime slurry is added into the tank until it reaches a pH of 7. This pH is required to activate the primary reagents.
The pumps move approximately 5,000 gallons of brown grease mixture into each of four reactor boxes.
Concurrent with the transfer of the slurry to the boxes, an operator adds reagents to the mixture. The reaction takes place over four hours. Operators dump the process solids into 20-cubic-yard “roll-off” containers or into other transfer equipment.
The process removes waste from brown grease to produce an easily disposed of aqueous solution that is low in total suspended solids; fats, oils, and grease; and biochemical oxygen demand. This liquid goes to the sanitary sewer system under an industrial discharge permit. The discharge can be adjusted easily to meet virtually any permit requirements.
Five thousand gallons of brown grease yield approximately five tons of solids at 55 percent moisture. The resultant solids are virtually odor free and resemble damp beach sand. They continue to flash off remaining water as they air dry, aided by the processing reaction, which is mildly exothermic. The aqueous discharge easily can be adjusted to meet virtually any permit requirements.
Final Product Characteristics
The final products are called EcoFuel and EcoSoil. They meet 40 Code of Federal Regulations 503.33 standards for vector-attraction reduction. EcoFuel contains lime to aid emissions control and has a green fuel value with BTU values matching those of coal (6,000 to 12,000+ BTUs per pound, depending on adjustments to contained moisture). The fuel product has had positive results in a large-scale burn at a regional power-generating plant, showing virtually no impacts on conveying, grinding, burn characteristics, or ash chemistry.
Some of the other physical and chemical characteristics are shown below.
> 400 degrees F
|Ash, weight percentage
|Heat of combustion, BTU/lb
6,617 (~55% moisture)
|Heat of combustion, BTU/lb
11,000+ (~25% moisture)
0.5 percent or 10 lb/ton
0.1% or 2 lb/ton
0.1% or 2 lb/ton
90% calcium carbon equivalent
In 2006, Rogers transferred commercialization of the technology to EcoPlus Inc., a publicly traded company. “This step provides us with access to capital for expansion and a socially responsible investment opportunity in the areas of energy and waste management,” he said. The company markets the technology to municipalities, counties, and wastewater authorities as well as private entities.
Benefit to Wastewater Treatment Systems
An EcoPlus final treatment facility can be set up at a wastewater treatment plant with virtually no impact on existing processes. Supernatant water from the process can discharge to the city sewer and still meet discharge requirements.
“In many cases, offsets and savings from reduced maintenance, avoided costs and repairs of the plant and the collection system, along with reductions of many collateral costs, can be combined with plant-use fees -- such as user and tipping fees -- to provide for the acquisition of a plant free of any additional appropriation from general funds,” Rogers said.
In larger cities, where the distance traveled by a grease pumper to an acceptable disposal location can be more than 60 miles, an EcoPlus preprocessing center can collect fats, oils, grease, and food solids and discharge a relatively high-quality water back into the sewer system. The grease concentrate then can be shipped for processing at an EcoPlus final treatment facility.
A wastewater treatment plant having a 20,000-gallon-per-day capacity could receive between $0.15 and $0.25 per gallon, or on the high side, up to $5,000 from using this technology and selling the final product. Plant maintenance costs could be reduced as much as $0.2 per gallon.
A Balanced Equation
The EcoPlus solution is positioned to answer both parts of the waste-to-energy equation. “We have not solved the entire problem of brown grease, but by providing a good ‘back end’ solution for disposal, we make it easier for wastewater treatment plants to comply with the rules and regulations for final discharge and sewer overflows,” Rogers said.
Grease, Sanitary Sewer Overflows, and Public Health
Across the country, cities and towns are implementing new programs and regulations to deal with interceptor grease from foodservice establishments and food processors. These actions are in response to federal mandates to prevent combined and sanitary sewer overflows under the National Pollutant Discharge Elimination System.
According to the 2004 U.S. EPA “Report to Congress,” more than 40 percent of sanitary sewer and combined sewer overflows are caused by the accumulation of waste grease. Typically, it coagulates into a matrix of grease and trash and causes blockages that lead to overflows.
The environmental agency report also says that there are from 23,000 to 75,000 sanitary sewer overflows per year discharging between 3 billion gallons and 10 billion gallons of untreated water per year into our streets, oceans, lakes, estuaries, rivers, and groundwater.
That untreated water is a big problem. Disclosures from the “Raw Sewage Overflow Community Right-to-Know Act” (a bill introduced in the House of Representatives in 2005) are startling:
- The Centers for Disease Control estimates that between 1.8 million and 3.5 million Americans become sick every year from swimming in waters contaminated by overflows.
- Economic losses due to swimming-related illnesses are estimated at $28 billion annually.
- There are an estimated 7.1 million cases of mild-to-moderate and 560,000 cases of moderate-to-severe infectious waterborne diseases in the United States each year.
Clearly, untreated water contains illness-causing bacteria, viruses, and parasites, which, from a health standpoint, justify the need for rules and regulations for the proper disposal of interceptor grease.
This article first appeared in the March/April issue of Water and Wastewater Products
This article originally appeared in the 03/01/2007 issue of Environmental Protection.
Robert Rubin, Ph.D., is an emeritus professor in the Biological and Agricultural Engineering Department at North Carolina State University. He has more than 30 years experience in water and waste management.
Edward W. Miles is vice president of sales and marketing for EcoPlus Inc. He has over 20 years of sales and marketing experience in the wastewater, telecommunications, and computer software industries.