A critical review of pretreatment technologies to enhance anaerobic digestion and energy recovery

A critical analysis of the impacts of COVID-19 on the global economy and ecosystems and opportunities for circular economy strategies

“…The organic content of soil reflects its healthiness and propensity to produce nutritious crops. The adoption of regenerative agriculture can facilitate the preservation of soil health through returning organic matter to the soil in the form of food waste or composted by-products or digestates from treatment plants ( Sherwood and Uphoff, 2000 ); (ii) value recovery from organic nutrients through the adoption of anaerobic digestion facilities ( De Gioannis et al., 2017 ; Huang et al., 2017 ), which is related to controlled biogas production for onward injection into natural gas network or conversion to electrical energy ( Atelge et al., 2020 ; Monlau et al., 2015 ). This has the potential to transform ensuing methane from food waste into carbon-neutral energy; and (iii) the embrace of urban and peri-urban agriculture ( Ayambire et al., 2019 ; Lwasa et al., 2014 ; Opitz et al., 2016 ; Thebo et al., 2014 ), which entails the “ cultivation of crops and rearing of animals for food and other uses within and surrounding the boundaries of cities, including fisheries and forestry ”( EPRS, 2014 ).…”

Synergistic Co-Digestion of Microalgae and Primary Sludge to Enhance Methane Yield from Temperature-Phased Anaerobic Digestion

“…Mono-digestion of microalgae has shown a limited impact on methane yield performance owing to their containing recalcitrant substances resistant to biodegradation. Therefore, pretreatment and co-digestion have been one of the most commonly suggested solutions to efficiently extract and enhance the methane yield from the microalgae [11,18]. In this section, the potential effect of co-digestion on increasing methane yields in trials of mono-digestion of microalgae between substrates was studied.…”

“…Among various methods proposed to enhance the performance of anaerobic digestion, pre-treatment has been most widely used to improve biodegradability and the hydrolysis rate [10]. There are many pretreatment technologies, including physical, chemical, biological and hybrid technologies that have been applied to microalgae [11]. Biological pretreatments refer to bio-degradation incorporating enzymes and enzymatic cocktails [12] or using different microbial communities (bacteria, fungi, archaea) in direct contact with microalgae to disrupt their cell walls [11].…”

“…There are many pretreatment technologies, including physical, chemical, biological and hybrid technologies that have been applied to microalgae [11]. Biological pretreatments refer to bio-degradation incorporating enzymes and enzymatic cocktails [12] or using different microbial communities (bacteria, fungi, archaea) in direct contact with microalgae to disrupt their cell walls [11]. Among existing biological pretreatment techniques, the use of carbohydrolases has been the most studied and applied to microalgae.…”

“…Because of limited applications and lack of information, biological pretreatment processes for microalgae have been only marginally investigated. Some of the previously carried out studies on different substrates have also reported drops in methane yields and deterioration in efficiency from biological pretreatments during co-digestion [11,15]. There are various complex interactions in the digester linked to the simultaneous application of biological pretreatment and co-digestion.…”