Innovative gas capture technologies with the objective to mitigate CO2 and CH4 emissions are discussed in this review. Emphasis is given on the use of nanoparticles (NP) as sorbents of CO2 and CH4, which are the two most important global warming gases. The existing NP sorption processes must overcome certain challenges before their implementation to the industrial scale. These are: i) the utilization of the concentrated gas stream generated by the capture and gas purification technologies, ii) the reduction of the effects of impurities on the operating system, iii) the scale up of the relevant materials, and iv) the retrofitting of technologies in existing facilities. Thus, an innovative design of adsorbents could possibly address those issues. Biogas purification and CH4 storage would become a new motivation for the development of new sorbent materials, such as nanomaterials. This review discusses the current state of the art on the use of novel nanomaterials as adsorbents for CO2 and CH4. The review shows that materials based on porous supports that are modified with amine or metals are currently providing the most promising results. The Fe3O4-graphene and the MOF-117 based NPs show the greatest CO2 sorption capacities, due to their high thermal stability and high porosity. Conclusively, one of the main challenges would be to decrease the cost of capture and to scale-up the technologies to minimize large-scale power plant CO2 emissions.

Solid-state fermentation (SSF) is part of the pathway to consolidate waste as a relevant alternative for the valorization of organic waste. The objective of SSF is to produce one or several bioproducts of added value from solid substrates. Solid-state fermentation can use a wide variety of organic waste as substrates thus, it is an excellent candidate in the framework of the circular bioeconomy to change the status of waste from feedstock. The development of SSF was boosted in the previous decade by scientific efforts devoted to the production of hydrolytic enzymes. Nowadays, SSF has expanded to other valuable products: biosurfactants, biopesticides, aromas, pigments, and bio-flocculants, among others. This review explores the conditions to obtain the main emerging SSF products and highlight and discuss the challenges related to the scale-up of these processes and the bioproducts downstream, which hamper their further commercialization.