<P><B>Abstract</B></P> <P>The stable H<SUB>2</SUB> production is the important link in the anaerobic biohythane fermentation. In order to address the key parameters for the stable H<SUB>2</SUB> production in the recirculated temperature-phased anaerobic digestion (R-TPAD) system, a critical strategy was proposed to adjust the recirculation ratio (<I>R</I>). The adjusting strategy was examined on a lab-scale R-TPAD system. The R-TPAD system was started up and operated with <I>R</I> = 1. Another system without recirculation (<I>R</I> = 0) was also operated as the control system. By narrowing the probable range from 0 < <I>R</I> < 1, the value of <I>R</I> = 0.4 was obtained for stable biohythane production from R-TPAD system. The harvested R-TPAD process achieved the volatile solids removal of 84.8% and the biohythane yield of 475 L/kg-VS<SUB>fed</SUB> with the H<SUB>2</SUB> content of 10.5%, where the H<SUB>2</SUB> yield efficiency was 248.0 mL-H<SUB>2</SUB>/COD<SUB>removed</SUB>. The success of operating R-TPAD was attributed to the proposed strategy, which used the tendency of existing CH<SUB>4</SUB> and the pH above 4.0 as the critical indicators for the stable H<SUB>2</SUB> production.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A critical strategy was proposed to adjust recirculation for biohythane production. </LI> <LI> Methanogenesis and lactic acid fermentation were inhibited for stable H<SUB>2</SUB> production. </LI> <LI> The CH<SUB>4</SUB> content and pH decrease were used as the indicators of H<SUB>2</SUB>-producing failure. </LI> <LI> The appropriate recirculation ratio was found by narrowing its probable range. </LI> <LI> The R-TPAD process removed 85% of VS and yielded 475 NL-hythane/kg-VS<SUB>fed</SUB> (H<SUB>2</SUB> = 10.5%). </LI> </UL> </P>