To my knowledge, technologies for biogas or bio-methane production from various bio-substrates through anaerobic digestion or their co-digestion are available in the literature. But very little literature is available on the optimum conditions for anaerobic digestion and/or their co-digestion. Therefore, a total of six studies are mentioned in this document to address this issue. Among of these a baseline survey and 5 lab based experiments were carried out (i) to investigate the potentials, status, problems, barriers and future needs for implementation and dissemination of biogas plants in Bangladesh and (ii) to find out the optimal conditions for maximal biogas and bio-methane production, respectively. The survey results revealed that poultry and dairy industry is an increasingly growing and a promising sector and the total poultry and dairy wastes have the theoretical biogas potential is 39 TJ per annum which can solve a big portion of deficit energy. The smart use of poultry and dairy wastes (biogas production and or electricity generation with organic fertilizer through anaerobic digestion) can be a sustainable energy solution for Bangladesh.