(Caroline Bork, Jan Cloutier, Andrew Stewart, 1998)
The Dallas Zoo has, for as long as we know, had their animal waste picked up on zoo grounds by an outside contractor to dispose of it at a local landfill. This practice has become outdated and desperately needs renovation. We have been given the task of reporting all available feasible options, so that the Zoo can more easily make a decision on how to change their ways. These alternative programs should in some manner incorporate the animal waste into some sort of composting program.
There are 3 possible recommendations that we have found suite the needs of the Zoo. The 3 models range from a financial one, to a ecological one, and to finally a full composting program, which is not really feasible to start out with immediately. The first and second alternatives both involve a small composting program on-site, which would use minimal waste and allow for a gradual progression into a full composting program. The difference between the two cases is what happens to the rest of the waste. In the first scenario, the excess waste continues to be transferred to the city dump. This system allows for some cost savings and makes a good first step into an environmentally sound zoo. In the second case, the rest of the waste is going to be loaded into a 30 cu. yd. roll-off dumpster and taken to a commercial composting facility such as Living Earth Technology. This would allow for all of the waste to be composted, just not all in the same site. The main drawback, however, is that this case involves a significant increase in transportation costs and therefore makes it cost ineffective. Finally in the last case, we proposed a full composting program on-site which is going to incur a large initial cost, but has been proven by other zoos to have a short payback period.
We analyzed these various programs through a financial model comparing the costs and saving of each. We also calculated a payback period and a net present value for each. The NPV of the first one was $-13,800.59 which means that given the $19,536.96 initial cost we can save $5,736.37 each year while having a payback period of 2.45 years. For the second case, the NPV is $-37,519.11 and having a savings of $-12,482.15 which also means that it can not have a payback period and is actually losing money throughout the years. Finally, the last alternative had an NPV of $21,955.38 and a savings of $11,606.58 for which there is a payback period of only 2.08 years.
All of these alternatives are possible at any time for a zoo to implement, just some are better than other for different reasons. We chose to evaluate all options to give a better understanding of the possibilities. The last case, however, is not a strong recommendation for the simple fact that composting is a learned technique and requires a stepping process to get to the end result. We still wanted to include it to show the direction that we would be headed if a composting program was initiated and we went along with the planned progression.