Grantee Research Project Results
Final Report: Feasibility and Life Cycle Assessment of Anaerobic Co-Digestion of Campus Food Waste and Swine Manure
EPA Grant Number: SU835694Title: Feasibility and Life Cycle Assessment of Anaerobic Co-Digestion of Campus Food Waste and Swine Manure
Investigators: Costello, Christine , Prescott, Amanda , Davis, Austin , Davis, Jeremy , Tellatin, Samantha
Institution: University of Missouri - Columbia
EPA Project Officer: Hahn, Intaek
Phase: I
Project Period: August 15, 2014 through August 14, 2015
Project Amount: $14,874
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2014) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Air Quality , P3 Awards , Sustainable and Healthy Communities
Objective:
The overall purpose of the Phase I activities was to evaluate the environmental, economic and engineering feasibility of anaerobically digesting (AD) food waste with a differentiation between observed food waste (a mixture of edible and inedible portions of food waste) as well as the inedible fraction of food waste only. Many institutions and municipalities are looking to divert food waste from landfills; however, selection of a treatment option is not a clear or easy task, necessitating additional research. AD has generally been considered a low viability option for food waste given the heterogeneous nature and potential for acidity to disrupt digestion. Specific objectives in pursuit of our purpose included: (1) conducting bench-scale AD trials using food waste; (2) applying engineering principles to design a full-scale system for treating the daily amount of food waste generated at four dining halls at the University of Missouri; (3) providing a cost estimate for the full-scale system; (4) comparing the life cycle energy and GHG costs of the AD system to other common options for food waste disposal, i.e., composting and landfill disposal; and (5) estimating the biogas and energy generation potential based on biomass availability in Boone County, Missouri. The specific scope of the project was four dining facilities at the University of Missouri and with regard to objective 5 Boone County, Missouri. However, the findings are generally valuable to all municipalities in search of solutions for the organic fraction of their waste streams.
Summary/Accomplishments (Outputs/Outcomes):
Preliminary results indicate that anaerobic digestion is technically feasible and environmentally preferable to landfilling and depending on the specific site conditions may result in less greenhouse gas emissions than aerobic composting as well. A unique aspect of our project is that we evaluated both the current mixture of edible and inedible food waste produced from cafeterias at the University of Missouri as well as the inedible fraction only. The purpose of this differentiation was to examine both the current mass flow (termed “unsorted food waste”) as well as the least possible food waste flow, i.e., the inedible fraction generated during normal food preparation and consumption.
The bench-scale experiment consisted of two trials: unsorted food waste and the inedible fraction of food waste only, both fed at an organic loading rate of 2g VS/L/day. Initial results of the bench-scale AD experiment demonstrate that both unsorted and inedible food waste produced between 40% and 50% methane by volume of produced biogas. Eighteen days into the experiment, with a hydraulic retention time of 22 days, the pH has not dropped below 6.8 in either trial and gas production is relatively constant.
The team designed and estimated the cost for installing an AD system that could treat all of the 775 kg of food waste generated daily from four cafeterias at the University of Missouri. The recommended system is estimated to produce between 40 and 71 m3methane/day, enough to continuously operate a 15 kW-hr generator to power the system. Chemical composition analysis enabled by the P3 funds was critical to both of these outcomes. The system is estimated to cost $295,000. Life cycle assessment components of the study are still underway. The initial literature review indicates that AD has been found favorable to landfilling (even with electricity generation) and aerobic composting. Finally, the team has collected information about additional biomass sources within Boone County, Missouri and will utilize the Anaerobic Digester Design Iterative Tool (ADDIT) developed by Michigan State University to estimate total biogas and electricity generation potential from these additional waste streams. Based only on recoverable manure production in Boone County application of AD could produce 224,000 kW-hour (kWh)/year, enough to supply approximately 20 households for a year.
In addition to generating new data for evaluating the feasibility of anaerobically digesting food waste, this project has been a beneficial learning experience for the students, PI, and other faculty advising the work, namely Drs. Misha Kwasniewski and Ellen (Caixia) Wan. The student team was selected from seniors enrolled in their Senior Design Capstone course at the University of Missouri in the Department of Bioengineering during Fall 2014. All four students elected to enroll for additional course credit in Spring 2015 to continue working on the project. As much as possible this project has been executed as a research project at the graduate level or at a consulting company in order to provide the students with experience that will benefit their nascent careers.
Conclusions:
AD as a treatment for food waste is a viable option both for current composition of food waste (edible and inedible) and for the inedible fraction only. Additional work to increase biogas production is needed.
Proposed Phase II Objectives and Strategies: The proposed work for Phase II of this competition will build on the momentum gained over the past year’s experience through two AD experiments: (1) the Team will optimize food waste feeding rates for biogas production and (2) explore the possibility of using AD to degrade bioplastics. Over the course of this past year Dr. Costello has worked with Mizzou’s Athletics Department to inventory their food waste stream in pursuit of “zero waste” stadium events and engaged in meetings with City of Columbia officials to discuss the results of this and other related projects as well as hurdles the City faces with regard to expanding their food waste collection and aerobic composting efforts. One of the biggest challenges in pursuit of both of these goals is contamination of the food waste stream with packaging and other non-organic materials. The issue is further complicated by the fact that bioplastics, the typical solution for food service packaging and utensils, do not degrade in aerobic composting operations as rapidly as food causing a build up of these materials. Due to this limitation presented by bioplastics, the City will only accept pure food waste streams and Athletics is stalled in pursuit of “zero waste” efforts. Demonstration of the potential for AD to pretreat bioplastics would open up management options for both.
Journal Articles:
No journal articles submitted with this report: View all 1 publications for this projectSupplemental Keywords:
anaerobic digestion, renewable energy, food wasteThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.