The concept of synthesizing carbon, hydrogen, and oxygen (C-H-O) SYmbiosis Networks (CHOSYNs) for the design of eco-industrial parks is introduced. Within a CHOSYN, compounds containing C-H-O are exchanged, converted, separated, mixed, and allocated. The use of C-H-O as the basis for integration creates numerous opportunities for synergism because C, H, and O are the primary building blocks for many industrial compounds that can be exchanged and integrated. A particularly attractive feature of the CHOSYN framework is its ability to use atomic-based targets to establish benchmarks for the design of macroscopic systems involving multiple processes. Several structural representations, benchmarking, and optimization formulations are developed to embed potential CHOSYN configurations of interest and to synthesize cost-effective networks. A case study with several scenarios is solved to demonstrate the new concept and tools. (C) 2015 American Institute of Chemical Engineers