Effective environmental governance is deemed essential in advancing the Sustainable Development Goals. However, environmental dimensions have no specific reference across the SDG 16 targets and indicators. In achieving SDG 16—the realization of peace, justice, and strong institution, polycentric environmental governance involving multiple actors across scales deserves thoughtful consideration. This study illustrates the potential of a polycentric approach to environmental governance in achieving SDG 16, using case studies of forest, watershed, and transboundary bushland and seascape management in Southeast Asia and Eastern Africa, namely Vietnam, Indonesia, and the Kenya–Somalia cross-border. By highlighting four key elements of polycentric governance namely, political will, legal framework, support from higher-level governance and capacity building, the case studies demonstrate that polycentric governance play a significant role in achieving three environment-relevant SDG 16 targets, yet these targets are silent about environmental governance dimensions. Since many conflicts arise from the environment and natural resources sector, we suggest that (i) polycentric environmental governance be strongly pursued to achieve SDG 16, and (ii) SDG 16 includes indicators specifically directed on polycentric environment and natural resource governance.

Ammonia and propionate are known inhibitors of anaerobic methanogenesis at higher concentrations, and are likely to coexist in digesters treating high-strength wastewater. Therefore, this study was conducted to assess the effects of ammonia and propionate on acetate-utilizing methanogenesis when they coexist. Response surface analysis with face-centered central composite design was used to explore the total ammonia nitrogen (TAN) level of 2–5 g/L and the propionate level of 2–8 g/L in acetate-fed batch incubation. Two models were successfully derived to estimate the lag period and the methane yield in response to the concentrations of the two chemicals. The lag period was affected by both inhibitors, with clues obtained of a synergistic effect at a higher concentration rage ([TAN] > 3.5 g/L and [propionate] > 5 g/L). The methane yield was also affected by the two inhibitors; between the two, it was more significantly dependent on the TAN concentration than on the propionate concentration. Real-time PCR showed that Methanosarcinaceae was the major methanogen group in this system. The results of this study improve our understanding of the inhibition of biogas reactors.