Optimizing biogas use in wastewater treatment plants for demand flexibility

Document Type

Article

Publication Date

9-2025

Department

Department of Electrical and Computer Engineering

Abstract

Wastewater treatment plants are energy-intensive loads with operational flexibility, which has motivated interest in how these plants can support power grid operation through demand flexibility. Since electricity is often the largest single operating cost for wastewater treatment plants, leveraging demand flexibility could offer significant financial benefits. One approach to reduce and shift the wastewater treatment plant's demand is through the use of biogas, a by-product of anaerobic digestion within the wastewater treatment process. Biogas (composed primarily of methane and carbon dioxide) is a renewable fuel that can be used to produce electricity to offset the plant's demand from the grid. However, many wastewater treatment plants currently flare biogas. The goal of this paper is to determine the optimal use of an on-site biogas storage tank and generator to minimize the costs of a wastewater treatment plant participating in the frequency regulation market. To do this, we formulate the wastewater treatment plant optimization problem subject to biogas and frequency regulation constraints while managing biogas production uncertainty. We solve for the biogas generator schedule and frequency regulation capacity to minimize operational costs. In a case study using data from a California wastewater treatment plant, we demonstrate how our approach can exploit electricity rate structures to reduce electricity costs and effectively participate in the frequency regulation market.

Publication Title

Sustainable Energy Grids and Networks

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