The most important contribution of my research is that I identified several leading indicators of souring. In all cases of souring, the accumulation of soluble chemical oxygen demand (SCOD) was an early and easily quantified indicator. A shift in effluent FA concentrations from shorter to longer species also portended souring. A reduction in the yield of methane (CH4) per mass of volatile suspended solids removed (VSSR) also identified souring conditions, but its variability prevented the methane yield from providing advanced warning to allow intervention. For the rapidly soured reactors, reduced bicarbonate alkalinity was the most useful warning sign, and an increasing ratio of SCOD to bicarbonate alkalinity was the clearest sign of souring. Because I buffered the slow-souring reactors with calcium carbonate (CaCO3), I could not rely on bicarbonate alkalinity as an indicator, which put a premium on SCOD as the early warning. I implemented two buffering regimes and demonstrated that early and consistent buffering could lead to reactor recovery.
The American food system creates a significant amount of waste and relies on significant energy, land, and freshwater inputs, accounting for a large amount of the United States GHG emissions (US EPA, 2009). Across the supply chain, a total of 40-50% of all food is not consumed. Reducing food waste is a way to decrease the impacts of the food system across the supply chain. At present, restaurants do not know of options available to them to mitigate their food waste and decrease their impact on climate change. For this project I partnered with Local First Arizona to use food recovery, or donating unused food to organizations that serve food insecure people, as an attempt to close the loop between the food that is being wasted and those who struggle to meet their caloric needs. The restaurants at Devour Culinary Classic, a weekend long food festival in Phoenix, AZ, received information about food donation and were prompted to donate at the end of the event. In total, 24 restaurants donated food, diverting 500 pounds of food, or 7% of all diverted waste, from the event’s waste stream. Donations were given to refugees recently released from ICE custody through a partnership with Arizona Jews for Justice. Following the event, recommendations on how to improve the project in future years were given to Local First Arizona in the categories of organization & logistics, marketing, communication, financial, and sustainability. A diffusion of innovation framework was used to identify the barriers faced by restaurants and analyzed how food festivals are a way to overcome those barriers.