Integrating strategies for sustainable conversion of waste biomass into dark-fermentative hydrogen and value-added products

Abstract

Inefficient waste management and associated environmental pollution are exhausting societies' precious renewable resources. Moreover, their effects on human health adversely affect the global economic scenario. These adverse effects are a constant cause of concern for environmental and health management. This review presents alternatives to uneconomical and non-eco-friendly methods for waste management and treatment. The multistep microbial anaerobic digestion (AD) process has the potential to metabolize up to 95% of organic matter to energy-rich methane (CH4) and carbon dioxide. The intermediates of AD can be transformed into value-added products, such as hydrogen (H2), polyhydroxyalkanoates (PHAs), and CH4. The unique feature of these valueadded products is their eco-friendly nature (non-polluting and biodegradable). The use of biowaste as feed makes the process economical. A few limiting factors that must be circumvented include (i) the slow metabolic rates of methanogens, (ii) high susceptibility to oxygen concentrations, and (iii) the complexity of biowaste. Here, we focus on using biowaste as a feed for integrating dark-fermentative H2 production processes with those of i) photo-fermentative H2, ii) PHAs, and (iii) CH4. This strategy could encourage a transition to an economy based on sustainable waste management and energy generation.