Biogas production from anaerobic digestion of food waste and relevant air quality implications

ABSTRACT

Biopower can diversify energy supply and improve energy resiliency. Increases in biopower production from sustainable biomass can provide many economic and environmental benefits. For example, increasing biogas production through anaerobic digestion of food waste would increase the use of renewable fuels throughout California and add to its renewables portfolio. Although a biopower project will produce renewable energy, the process of producing bioenergy should harmonize with the goal of protecting public health. Meeting air emission requirements is paramount to the successful implementation of any biopower project. A case study was conducted by collecting field data from a wastewater treatment plant that employs anaerobic codigestion of fats, oils, and grease (FOG), food waste, and wastewater sludge, and also uses an internal combustion (IC) engine to generate biopower using the biogas. This research project generated scientific information on (a) quality and quantity of biogas from anaerobic codigestion of food waste and municipal wastewater sludge, (b) levels of contaminants in raw biogas that may affect beneficial uses of the biogas, (c) removal of the contaminants by the biogas conditioning systems, (d) emissions of NO_x, SO₂, CO, CO₂, and methane, and (e) types and levels of air toxics present in the exhausts of the IC engine fueled by the biogas. The information is valuable to those who consider similar operations (i.e., co-digestion of food waste with municipal wastewater sludge and power generation using the produced biogas) and to support rulemaking decisions with regards to air quality issues for such applications.

Implications: Full-scale operation of anaerobic codigestion of food waste with municipal sludge is viable, but it is still new. There is a lack of readily available scientific information on the quality of raw biogas, as well as on potential emissions from power generation using this biogas. This research developed scientific information with regard to quality and quantity of biogas from anaerobic co-digestion of food waste and municipal wastewater sludge, as well as impacts on air quality from biopower generation using this biogas. The need and performance of conditioning/pretreatment systems for biopower generation were also assessed.

Acknowledgment

The research team expresses its gratitude toward the commission contract managers, Marla Mueller and Simone Brant, and Guido Franco and Yu Hou of the California Energy Commission (CEC), as well as Robert Dole (recently retired) and many other staff members of the CMSA for providing great guidance and assisting the team in many ways. The research team also expresses gratitude toward the Technical Advisory Committee (TAC) members for providing valuable technical input and suggestions for this project. The TAC members are (in alphabetical order) Rizaldo Aldas (CEC), Chris Berch (Inland Empire Utility Agency), Ryann Bonner (Environ Strategy), Robert Cole (CMSA), Jason Dow (CMSA), Steven Fan (City of Los Angles), Jacques Franco (CalRecyle), Robert Gilles (San Joaquin Valley APCD), Ken Kumar (Energy Environmental Solutions), Tung Le (CARB), Angus MacPherson (CARB), Gary O’Neill (CEC), Lisa Van de Water (San Joaquin Valley APCD), and Robert Williams (UC Davis).

Funding

This project was funded by the California Energy Commission under the Public Interest Energy Research (PIER) Program (Agreement Number 500-11-030).

Additional information

Funding

This project was funded by the California Energy Commission under the Public Interest Energy Research (PIER) Program (Agreement Number 500-11-030).

Notes on contributors

Jeff Kuo

Jeff Kuo is a professor at the Department of Civil and Environmental Engineering, California State University, Fullerton (CSUF).

Jason Dow

Jason Dow is the General Manager of Central Marin Sanitation Agency (CMSA), San Rafael, CA.