Abstract

In recent years many countries and several regions in the United States have passed legislation on banning landfilling of organic waste. It is a well-known fact that organic wastes, including food scraps, generate methane under anaerobic landfill environments and contribute significantly to global warming. As more regions are mandated to follow the landfill ban, there is an increasing demand for alternative technologies for the disposal, treatment and upcycling of food wastes. Disposal and treatment may not result in any value-added products and hence are not the most efficient ways to manage food waste. As food waste has a high energy value due to the presence of organic nutrients, it can be a suitable resource to generate energy, fuels, chemicals, and materials through ‘valorization’ technologies. Therefore, to proactively address food waste management issues in the future, this dissertation evaluated three alternative food waste valorization options for institutional (food scraps) and industrial food wastes.

First, the food scraps and industrial food wastes were characterized for their chemical composition such as organic and inorganic nutrients. The objectives of this study were to (a) provide a detailed database on chemical characteristics of food scraps and industrial food wastes based on in-house laboratory measurements, third-party analysis, and literature data; (b) analyze the data obtained to understand the variability in characteristics between different sources of food waste. The outcomes of this chapter resulted in a comprehensive data collection and statistical analysis for food scraps from various sources and 10 different industrial food waste streams. The developed data inventory is useful to anyone who does not have resources to carry out food waste characterization and researchers who work on food waste modeling studies.

Second, the process issues related to anaerobic digestion of food scraps were address using an experimental study. Process instability is a major issue in food scrap digestion at higher organic loading rates, and often leads to digester failure. The objectives of this study were to (a) study the effect of increasing organic loading rate on the stability of the process by monitoring several process parameters, and (b) offer a solution to the instability issues using an unconventional co-digestion approach. The experiments were carried out in semi-continuous mode with a daily feeding cycle to mimic the real-world conditions as closely as possible. Process parameters such as pH, volatile fatty acids, alkalinity, ammonia, biogas production, methane and hydrogen sulfide content of biogas were monitored on a regular basis. Results of this experiment provided useful information for digester operation on the threshold levels of various process parameters to that would help avoid a digester failure. Co-digestion of food scraps with other food sector wastes such as acid whey, wasted bread and soiled paper napkins were proven to significantly improve process stability and helped achieve high organic loading rate during the digestion of food scraps. These results are useful in the operation of non-farm digesters where conventional co-substrates (such as animal manure) are not available or not practical to haul.

Third, the use of fermentation technology in food waste management was evaluated for its technological feasibility. While anaerobic digestion is a well-developed technology for organic waste management with a few processes issues related to food scrap digestion, the use of fermentation in food waste management is not well documented. Food waste fermentation to produce value-added fuels and chemicals is taking shape only in recent years. The objective of this work was to provide ‘state-of-the-art’ knowledge on fermentation of food wastes in the production of products, specifically ethanol, 1-butanol, iso-butanol, and organic acids using experimental and published data. With a combination of experimentally obtained and previously published studies, a matrix was developed that maps the suitability of producing either alcohols or organic acids from various food wastes. The outcomes of this study provided a contemporary knowledge on the research status related to food waste fermentation. Also, the types of food wastes that can be potential feedstocks for fermentation to produce ethanol, butanol, lactic acid and succinic acid were suggested through the developed matrix. The outcomes from this work provide useful qualitative information to the growing number of businesses in the waste management world looking for newer and more efficient options for food waste valorization.

Finally, the potential of thermochemical conversion as a food waste management strategy was explored using an exergy analysis and life cycle thinking approach. Use of thermochemical processing to produce a soil amendment called biochar is a circular economy inspired approach and needs evaluation as there is a limited number of research studies in this area. The objectives of this study were to (a) produce biochar using a small-scale commercial thermochemical processing unit and characterize the biochar for elemental composition, (b) estimate the exergy efficiency of various scenarios, and (c) estimate the global warming potential (GWP) by expanding the system boundary to use biochar as a soil amendment. Based on these results, the most practical options for management of food waste were recommended to produce biochar or thermal energy. The exergy analysis combined with GWP potential estimations can assist operators of thermochemical conversion systems to decide upon the practical operating conditions, and policy makers to consider and regulate newer technologies for food waste management.

Publication Date

12-2018

Document Type

Dissertation

Student Type

Graduate

Degree Name

Sustainability (Ph.D.)

Department, Program, or Center

Sustainability (GIS)

Advisor

A. Christy Tyler

Advisor/Committee Member

Thomas Trabold

Advisor/Committee Member

Callie Babbitt

Campus

RIT – Main Campus

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