This fee is designed to make it economically feasible for the plant to install equipment to remove the entrained materials and dispose of them elsewhere. In other words, they make it worth the cost of equipment to remove the meat trimmings. Over 99% of the systems in place use a technique know as Dissolved Air Flotation (DAF) to do this. Basically, you take compressed air, force it into water under pressure to create a solution similar to carbonated water, and then release that air-saturated water into the bottom of a tank of contaminated water. The air escapes from solution just like a soda pop fizzing, and the rising bubbles lift the contaminates to form a layer of sludge floating on the water surface. This sludge is then skimmed off into a receiving tank. The processed water, now clean relatively speaking, is discharged to the municipal system.

     Originally the DAF sludge, usually just called DAF, was simply buried in a landfill; however there are regulatory restrictions on that now as well. Some plants pay a fee for land application, while others have resorted to paying a rendering plant to haul away the DAF. These rendering plants are the same rendering plants that collect and process restaurant grease traps. The DAF sludge can go into the mix, however the rendering plant suffers a final product quality loss from the DAF sludge, so they pass that cost on to the slaughter house as a disposal fee. Therefore, the plant is still absorbing the disposal costs by either paying the land disposal fees or by paying the rendering company to remove the DAF.

     We integrated the original DAF reduction unit for a customer that wanted to eliminate the cost of disposal. Much of the research to make the system work was available from studies done in the late 1980s. We accepted the job to coordinate all of the equipment into a coherent system, and after this system was in place we did the design for the self contained micro-rendering plant described here.

     The DAF Reduction unit is a self-contained miniature rendering plant that cooks the DAF, extracts the oil and protein from it, and discharges water. This water is not quite clear, so another water processing module is required for a complete system. But the technology which should be used to process the discharged water needs to be determined on a case by case basis, therefore we did not include it in this unit’s design. We designed this to be a completely self contained system that could be delivered as a single unit. We also have an evaporator system design which can be used to process the water, or a simple belt press can be purchased from any of many manufacturers and plumbed into place to process the water. Which choice is appropriate depends on the plant chemistry, and should be decided on a case by case basis.

     The system produces two commercially viable by-products; a protein powder suitable for use in animal feed, and brown oil suitable for use as livestock food additive, boiler fuel to provide power for the system or as a bio-diesel feed stock.

     Currently the cost savings for the system is in reduction of DAF disposal costs, not profit margin on the by-products. The system allows the plant to move from paying for disposal to getting paid for the by-products. Obviously rate of return is dependent on what their current costs are for DAF sludge disposal.

     The small but perceptible groundswell of bio-diesel cooperatives that are forming are beginning to work on pilot production facilities and that is only going to increase. In addition, several large scale production facilities are coming on line. The price of petroleum is unlikely to fall precipitously, which keeps bio-diesel viable. Obviously, these production efforts require oil feedstock. While some feedstock will come from farm production targeted at bio-diesel, like soybean oil, the potential to extract useful oil feedstock from a current waste stream is a double benefit for everyone.