<P>A microbial electrosynthesis cell comprising two biological cathode chambers sharing the same anode compartment is used to promote the production of C2-C4 carboxylic acids and alcohols from carbon dioxide. Each cathode chamber provides ideal pH conditions to favor acetogenesis/carbon chain elongation (pH = 6.9), and solventogenesis (pH = 4.9), respectively, without the requirement of external acid/base dosing.</P><P>Graphic Abstract</P><P>A microbial electrosynthesis cell comprising two biological cathode chambers sharing the same anode compartment is used to promote the production of C2-C4 carboxylic acids and alcohols from carbon dioxide.<BR/><IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c9cc00208a'/><BR/></P>