Abstract

Every day, enormous quantities of nutritious food are wasted in landfills across the globe. Agriculture and food production use intensive amounts of water, chemicals, and land, rendering food waste as a major environmental and economic concern. New York State is currently considering legislation that would ban landfill disposal of food waste produced by large institutional generators, such as universities, hospitals, sports venues, restaurants, grocery stores, etc. Institutions have concentrated populations which generate predictable volumes of food waste and waste cooking oil. At the same time, these populations need heat, electricity, vehicle fuel, and soap. Developing a biorefinery system offers great potential to institutions and provides viable and sustainable utilization of various waste streams to generate energy via anaerobic digestion and biodiesel production process while simultaneously solving a waste disposal issue. However, the implementation of biorefinery systems at institutional food waste generators is just beginning, and data required to design the system and relevant case studies are very limited. Recognizing the urgent need to find alternatives for the diversion of food waste from landfills, this dissertation has provided the technical and economic viability of decentralized, onsite biorefinery systems at institutional generators with a specific focus on large institutions generating, on average, more than 1.8 metric tons of food waste per week (~91 t/year, equivalent to 100 short tons/year). The challenges and opportunities of these alternatives have also been considered in this dissertation.

First, development of sustainable food waste management requires an integrated, interdisciplinary management structure which includes a good understanding of regional variations in food waste resources, waste treatment facilities and processing capacity in a specific geographic region. Currently, poor quality and unreliable data on food waste prohibits proceeding to efficient waste management. These scarcities of data have led to a call for further research. To identify the research gaps, Chapter 2 begins with an assessment of reliable data on the quantity and types of food waste produced, transport of waste to treatment facilities, location of existing waste treatment facilities, and the amount of wastes that could potentially be treated at these facilities. Regions 3 and 8, as defined by the New York State Department of Environmental Conservation (DEC), were chosen as case studies to the underlying challenges and potential opportunities. The information provided in this chapter can be an important resource for implementing future waste diversion strategies, and further indicate which policy attributes should be considered.

In Chapter 3, an assessment was conducted of the technical challenges, economic feasibility and policy opportunities to adopt low-volume anaerobic digester (LVAD) systems, designated for deployment at the scale of an individual food waste generation site. Food waste generators often have much lower volumes of organic material available for conversion than dairy farms or public-owned treatment works (POTW). Small anaerobic digestion systems are not a new technology but have historically been implemented primarily in treating animal waste in developing countries. In the U.S., anaerobic digestion of food waste is usually achieved by co-digestion with dairy manure in centralized facilities, while food waste-only anaerobic digestion is still emerging and public data or case studies necessary to establish this as a potential food waste management pathway are lacking. Rochester Institute of Technology (RIT) was chosen as a case study to assess the viability of implementing an LVAD system utilizing campus organic waste. It was demonstrated that the LVAD approach is economically feasible only if several conditions are met: biogas is utilized directly for thermal energy applications, thereby eliminating the capital/operation/maintenance costs associated with electricity production; system capital cost is reduced to $500,000 or less; and available feedstock is increased to at least 900 t/year by importing food waste from neighboring generators and collecting associated tipping fees.

Chapter 4 documents an investigation of various solution pathways available to utilize another important institutional food waste material: waste cooking oil (WCO). Institutions such as universities usually generate large amounts of waste cooking oil that can be suitable for production of biodiesel via the process of transesterification. The free fatty acid (FFA) content of waste cooking oil from institutional cafeterias is often lower than many other establishments (i.e., fast food restaurants), and thus has a greater value as a biodiesel feedstock, because the cooking oil replacement rate is often higher. The development of a closed-loop biodiesel production system, including utilization of crude glycerol as an ingredient for soap production, is compelling especially in a constrained system because the locations of WCO feedstock supply and biodiesel demand are in close proximity and controlled by a single entity. Biodiesel can be utilized by the RIT community in vehicles and other applications. Crude glycerol can be refined and used to produce soap of varying quality and has potential as a value-added product. Potentially, the soap could be used in cafeterias and bathrooms across campus and dining services. This study indicated that using waste cooking oil for biodiesel production at the institutional scale could only be viable by generating the revenue from the sale of biodiesel and offsetting the cost of high quality liquid soap at retail price.

In Chapter 5, it was demonstrated that black soldier fly larvae (BSFL) could potentially reduce the amount of food waste needing to be landfilled in areas of concentrated generation, such as urban areas and institutions like universities and hospitals. BSFL have previously been used by home gardeners and large agricultural enterprises to transform food wastes and animal manures into feed for chickens or fish, while significantly reducing waste volumes. Bioconversion of food waste biomass with BSFL results in useful products such as protein rich insect biomass. This study demonstrated that bio-methane potentials (BMP) of BSFL were higher than the potential of food waste and manures and 1.5 to 2 times higher than other representative feedstocks, including energy crops and algae. In addition, the yield of biomass per hectare of land used is much higher. BSFL could therefore be a viable feedstock for biogas production or as part of an integrated biorefinery system, and as an effective bioresource solution for the global problem of food waste management.

Finally, it is uncertain that an on-site low volume anaerobic digestion system at institutional generators is most economically and environmentally beneficial. Therefore, a model was developed to compare different potential food waste treatment scenarios: centralized anaerobic digestors (AD) at large confined animal feeding operations (CAFOs), centralized AD at landfills, centralized AD at waste water treatments plants, and low volume anaerobic digesters (LVADs) at individual food waste generation sites. Chapter 6 presents an assessment of the optimal food waste conversion options for particular spatial distributions of food waste materials in two geographical regions of New York State. The assessment was based on three economic indicators, including net present value (NPV), internal rate of return (IRR), and payback period (PP), to enable food system stakeholders to determine the most cost-effective food waste utilization strategy. The decision process considered was based on the availability of existing facilities (e.g., stand-alone AD, wastewater treatment plants with AD, and composting), available capacity of selected facilities, and available quantity of animal waste in each region. This assessment demonstrated that capital cost plays a significant role in achieving economic viability, and tipping fees are often the major sources of revenues for these treatment facilities. Without offset of the capital investment from government entities in the form of grants, the economic viability of new facilities is challenging. Therefore, diverting food waste to WWTPs with excess capacity was identified as an important option that showed the most profitable scenario without considering environmental incentives and renewable energy credits.

This dissertation focused on economic implications of alternative food waste conversion options for institutional generators, through the integration of conversion technologies using different waste feedstocks in a decentralized, on-site biorefinery architecture. In this sense, the biorefinery model was presented as a potential alternative to centralized large scale-systems that utilize wastes from multiple sources, often including transport of waste over large distances. This concept aimed at maximizing the utilization of food waste in a manner that enables institutional generators to benefit from organic material they generate during normal operation. The findings from this dissertation provide valuable information to small-scale food processors and institutions that currently send their solid waste to landfills or incinerators, paying disposal charges or sending it to anaerobic digestion, usually involving transport costs and tipping fees. The method developed in this dissertation can be readily adapted by other institutions, and the information provided would assist entrepreneurs in achieving successful commercialization of small-scale food waste utilization systems.

Publication Date

5-2019

Document Type

Dissertation

Student Type

Graduate

Degree Name

Sustainability (Ph.D.)

Department, Program, or Center

Sustainability (GIS)

Advisor

Thomas Trabold

Advisor/Committee Member

Nabil Z. Nasr

Campus

RIT – Main Campus

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