Another word for rendering could be evaporation. For every pound of viscera that comes off a kill floor, there is 25 percent meat and bone meal, and 25 percent fat. The remaining 50 percent is water.
Processors want to render the fat and protein, but water must be effectively evaporated if a rendering operation is to be successful.
"What we are doing is driving off the water," says the president of a rendering manufacturer. "Then the packer has the necessary material to make a rendering operation successful."
Many processors have installed their own rendering facilities in the past five years and have found it adds to their bottom line. The trend has been to produce a high-quality product and find a niche for it.
For example, nearly 300 new pet food products were introduced in 1993 (the latest figures available), 17 percent more than in 1992. Many of the new products came from rendered beef and pork by-products.
In addition, rendering by-products into soaps, chemicals and lubricants has also increased, as has edible feed for hogs and poultry, a rendering manufacturer points out.
The challenge for processors is to determine whether rendering can add to their bottom line.
It is a simple equation: Look at what is left over on the kill floor, look at current market values for those potential by-products, estimate the operating cost of a rendering facility, determine how long the payback period should be, and measure the financial figure against the profit margin.
It is no surprise that the evaporator (or cooker) determines the size and cost of a rendering system. From there, all rendering machines are sized. Installing a rendering operation could run processors as much as $10 million.
"The rendering system must be sized to be capable of removing the maximum amount of water," says the president of another rendering manufacturing company. "The system must also be sized to convey, grind, press and store raw and finished materials."
But there are different yields for all classes of material.
The hardest part for processors is to get an accurate figure on yields for each raw material, according to rendering manufacturers.
Another manufacturer points out: "The need for rendering systems for every processor is different. Because of this, an evaluation needs to be made for every processor in order to determine what type of approach would be best for that specific plant."
Another aspect is landfill capacity. Since many landfills no longer accept items such as hog hair and gel bones, processors need to find other avenues in which to use them.
Hair and gel bones are being rendered into digestible proteins that can be added to animal feed.
"In the past, the emphasis was on running a certain amount of material through the rendering system each day," a manufacturer says. "Processors would open the steam valves, turn everything on and render as much of the material as possible because whatever they render, they could sell.
"Today, there is a lot more competition in the fats, oils and proteins markets," he adds. "Processors are looking for quality rendered products. It has become a tough economic analysis for processors."
One easy way to spoil the by-product quality is allowing too much sludge to enter into the rendering process. It is an issue that becomes more problematical because many local environmental ordinances and laws prevent the dumping of sludge in streams, creeks and other waterways.
So when sludge is processed through a plant's wastewater treatment facility, processors need to find some use for the final product.
"Processors have to make a choice," a manufacturer cautions. "If they process the sludge with inedible materials, they will downgrade the quality of the finished product. If they process the sludge separate, they need to install a separate rendering system for low-quality products. Because more processors are required to process the effluent sludge, the construction material for rendering equipment needs to change."
Another manufacturer warns that if sludge is added to the rendering system, it must be done at a constant rate.
"If sludge is added inconsistently, it will be hard to control the discharge temperature of material from the cooker," he says. "If too much sludge is added, it will be impossible to press the fat level in the crax down to an acceptable level."
Here is a checklist for processors who are debating whether to begin their own rendering operations:
3 Prepare a list of raw materials to be processed on a daily basis.
3 Determine whether the products will be rendered into edible or non-edible. This effects the yield in rendering.
3 Determine how many hours and shifts each day a processor wants to run a rendering operation.
3 Determine what grade of finished product would be most advantageous to produce. If there is a good market for high-quality, finished products, processors might consider installing a rendering system for standard, high-quality raw material and a separate facility for low-grade materials, such as sludge.
3 Balance the economics of a rendering system. Processors should determine how many tons of product they make, what the worth of that product is, and how much they want to spend on a system, including utility costs. Rendering is an extremely energy-intensive process.