Coupling fish waste anaerobic digestion, ammonia extraction and microbial protein production

This study investigates coupled fish waste anaerobic digestion (AD), electrochemical ammonia extraction, and microbial protein production using hydrogen-oxidizing bacteria (HOB). AD of fish waste after protein extraction was performed in a lab-scale continuously stirred-tank reactor (CSTR) reaching a maximum methane yield on volatile solids (VS) of 404 mL·g^-1. Online electrochemical ammonium extraction achieved 14 mg·L⁻¹·d⁻¹ extraction rate. Extracated ammonium served as a nitrogen source for HOB cultures, which exhibited growth rate: 0.97 d^-1; cell dry weight (CDW) yield on H₂: 2.1 g g^-1; protein content on CDW: 28.01 g g^-1. Flue gas impurities (CO, NO₂, SO₂) had overall minimal effects on HOB growth and yields. Ongoing efforts focus on process optimization by modifying electrochemical cell configuration and on investigation of continuous HOB cultivation.