Organic wastes are a suitable feedstock for the production of value-added products that have been insufficiently exploited due to their complexity, which challenges their transformation by conventional procedures. Gasification and pyrolysis of organic wastes can reduce this complexity by producing syngas (CO plus H-2 and other C1 gases), which can be used as a valuable commodity by catalytic conversion into chemicals. However, the high cost and susceptibility to poisoning of chemical catalysts have encouraged research on biocatalysts that convert C1 components of syngas into different multi-carbon compounds. Nowadays, research on syngas fermentation is receiving much attention in order to enhance the productivity of microorganisms by remodeling their metabolism and by optimizing the bioreactor operational conditions. This review highlights the new technical achievements of pyrolysis as well as the new biotechnological uses of syngas for the production of bulk chemicals and biopolymers, discussing the major bottlenecks that challenge syngas fermentation. (c) 2015 Society of Chemical Industry