Haulin’ Gas: Evaluating and Optimizing Santa Rosa’s Organics-to-Energy Program

Trucked waste programs provide an opportunity for water resource recovery facilities (WRRFs) to turn organic "waste" into a valuable resource and reduce greenhouse gas emissions through energy production. Implementing a trucked waste program maximizes the economic and societal value of feedstocks once considered environmental risks, but requires oversight and maintenance to be successful. As more WRRFs plan for codigestion programs with SB-1383 adoption, it is important for utilities to evaluate costs versus benefits, and to understand the required operational, maintenance, monitoring, and compliance requirements associated with a new program.

The City of Santa Rosa has accepted installed a high strength waste (HSW) receiving station in 2017. The program accepts HSW such as fats, oils, and grease (FOG), brewery waste, and dairy waste while collecting revenue from tipping fees, generating energy, and recovering heat for plant processes. While the program operates at a net positive revenue, the City sought to further refine the program by taking a closer look at the impact from individual trucked wastes to their treatment processes. The City also wanted to identify opportunities to optimize the program administration.

Brown and Caldwell and the City collaborated on a detailed study to complete the following:
1. Summarize historical contributions of HSW to biogas and biosolids
2. Identify opportunities to optimize or refine the program
3. Provide tipping fee recommendations based on an economic analysis

This presentation will introduce fundamental requirements and considerations for a trucked waste program, including design criteria, operations, maintenance, permitting, monitoring, and billing. The evaluation could be a valuable case study for utilities or consultants evaluating start-up or optimization of a similar program for codigestion.

Diversion of organics from landfills provides a pathway for WRRFs to receive food waste and generate additional biogas for beneficial use. As these opportunities are considered, utilities should be aware of the requirements associated with implementing and operating a codigestion program. The lessons learned and recommendations from this study present ways to improve plant performance and minimize risks and costs associated with the operation and management of a trucked waste program.