Results
Testing
pH
The pH testing followed TMECC 4.11A 1:5 SLURRY pH method. 40 grams of dry weight equivalent of normal compost was added to an Erlenmeyer flask. Deionized water was then added to achieve 200 mL to create a 1:5 solids to liquid ratio. The mixture was placed on a shaker table for 20 min at 180 rpm. Once the mixture became a slurry, the pH was recorded with a digital pH sensor with a glass differential electrode (PEEK).
Ash Content
The percent ash test followed TMECC 3.02A Unmilled Material Ignited at 550℃ Without Inerts Removal. 50cm3 of compost was dried at 70℃ for 24 hours before placing into a muffle furnace at 550℃ for 2 hours. The compost weight was recorded before and after the furnace. Ash content is recorded as a percentage from initial dried weight.
Heavey Metal
The heavy metals were tested using a subcontractor within NAU. The subcontractor tested the samples with a Portable XRF Thermo Fisher Niton XRL3 utilizing the EPA Method 6200. The samples were dried and sieved through a #60 sieve and packed into small testing cups. Four sub-samples were tested per pile. The cups were placed into the portable XRF then tested for 90 seconds. The heavy metal results are tabulated below in Table 5.3 Heavy Metal Results.
Nitrate
The nitrites/nitrates were tested utilizing TMECC 4.02-B to create the slurry. The slurry was filtered once using a glass membrane filter, and once using a gridded coliform filter. Then, HACH method 8039 was followed to test the nitrates/nitrites with calorimetry using cadmium as a reagent. The test had to be modified due to the lab not having an Ion Chromatograph Dionex DXI20.
E.Coli
E. Coli was initially supposed to be tested under TMECC 7.01-A utilizing a stomacher. A stomacher is a sterile food pulverizer with no blades. However, the ENE Lab, does not have a stomacher. Therefore, the test was modified using HACH Method 8001 with 5 grams of compost added into the testing tubes. 10 ml of DI Peptone Water was added with 5 grams of ground compost. The slurry is added to Lauryl Tryptose broth and the sample incubated for two days at 35˚C inside an incubator (Hach portable, 12 VDC) in the dark. A drop of the broth was then added to EC (E. Coli) Medium with MUG (4-methylumbelliferyl-beta-D-glucuronide) broth tube.
Temperature
The compost sample piles have been analyzed to be mature by the external lab due to the sample being within state and federal limits for Salmonella and E. Coli [8]. The results indicate a temperature plateau between 113-128°F. Mature compost will typically cool off to less than 90°F. This is due to the organic decomposition in the compost pile being completed. Compost should maintain a temperature of 104°F for five days to kill off pathogens. This is found to be above the common range for mature finished compost. The compost piles temperatures measured were determined to be safe as long as the temperatures had previously plateaued within the compost piles.
Ammonia
If the compost is above 550 ppm, the compost is considered immature. If the compost is between 100ppm and 550 ppm, this indicates the compost is mature. If the ammonia is lower than 100 ppm, this indicates the compost is very mature [2] [8]. The tests that would have been used for testing are TMECC 4.02-C. Ammonia could not be tested within the EnE Lab due to the lab not being equipped with a working Ion-Selective Electrode.
Salmonella
Salmonella could not be tested at the EnE Lab at NAU because the lab does not have a stomacher and stomacher bags. Stomacher bags are used to keep each sample completely sterilized when placed inside the stomacher for pulverizing. The procedure that would have been followed is TMECC 7.02.
C:N Ratio
The C:N Ratio depicts the rate of decomposition of compost mixtures. C:N Ratios also accurately depict when ripeness has been reached within the compost [2] [8]. The C:N Ratio needs to be below 14 for the compost to be considered mature. The tests that would have been used are TMECC 4.02-A for Total Nitrogen and TMECC 4.01-A. The C:N Ratio could not be tested within the EnE Lab at NAU because the lab does not have an aluminum heating block for 500˚C and an 832 Series Sulfur/Carbon Determinator.
Impacts
Social Impacts
The social impacts from NAU’s composting operation are positive. NAU’s composting project receives bulking agent donations from small and large businesses. These donations provide businesses with a free alternative to dumping their waste at the Cinder Lake Landfill. This relationship creates positive bonds between NAU and businesses looking to dispose of bulking agent waste. NAU’s composting project produces compost that people will be able to purchase for local gardening needs and creates a greater sense of community. The production of compost by NAU improves the relationship between residents and the state school NAU, in that NAU is seen as trying to positively impact the environment
Environmental Impacts
The environmental impact of the project is positive because instead of dumping the food scraps into a landfill, it is being reused as compost that helps the local gardeners. Compost decomposed the organic materials that are throw out in the compost from different sources, and it also helps the soil to hold the carbon dioxide which mean that emissions will be reduced. It is also an Eco-friendly safe product and will save more space in the landfill.
Economic Impacts
Northern Arizona University (NAU) can save more money over 20-year period if they use an external lab instead of in-house testing. Also, NAU can provide more funding by selling the compost for more projects in NAU facilities. Finally, all local companies will be able to avoid tipping fees for throwing out the waste because as mentioned in the operation part that every waste is being disposed in NAU Compost Facility for free.
Conclusion
SAS Engineering has concluded that the NAU Compost Facility Analysis project should not do in-house compost testing at NAU. If compost were to be tested at NAU, there would be a loss money. Equipment and materials would need to be bought in order to sustain testing. The HACH modifications for testing did not work as well as TMECC, which must be followed for testing.