At least once a year we are approached by entrepreneurs who have conceived a system for converting garbage into animal feed. The garbage in question is frequently restaurant waste, although it may be institutional or even residential waste.

Invariably these projects collapse under a number of harsh realities.

The demand is frequently made for a screw press that will dewater the waste to some unrealistically low percent moisture, like 60%. In reality, garbage is 85% to 95% moisture, and, after pressing, the press cake always will have over 80% moisture content. Wishing for a press that will remove more moisture does not mean that one can be built.

In order to prevent spoilage, the moisture content must be reduced to a range of 10% to 15%. This dehydration must be done in a rotary drum dryer, and the fuel costs generally exceed the value of the dry garbage. That is, to produce a ton of 12% moisture material from press cake with 80% moisture, the dryer will require over one hundred therms of energy. That is more than $40 worth of fuel to produce one ton of animal feed.

Pressing garbage to remove the moisture creates an impossible disposal problem. The press liquor from pressing garbage is like a thick milk shake of suspended solids. The BOD loading of this liquid would overwhelm any wastewater treatment system.

The labor costs to remove contaminants are major. Restaurant waste typically has plastics (shrink wrap and Styrofoam), metal (silverware and change coins), string and cord, not to mention broken chinaware, glass and pop cans. Farmers are reluctant to buy feed that might contain these items, even at discounted prices.

None of this seems to faze our would-be garbage millionaires. What generally brings them to earth are two facts: (1) the opportunity they see has been obvious in America for at least a century, and no one has made a go of it, and (2) nobody has made a go of this business potential in third world countries where labor is cheaper, farmers are less picky, feed is more expensive, and businesses are less encumbered by environmental regulations.

Despite requests to dewater