Second-generation biomass is a renewable resource that can address the increasing global energy demand and help to partially substitute the use of and dependence on fossil fuels, since it can be transformed into gas, liquid and/or solid fuels by physical, thermal, thermochemical and/or biological processes. However, its potential is not fully exploited because the process to extract the phytochemicals present in such organic byproducts has been largely omitted. Natural compounds are of interest to high value-added industries such as cosmetics and pharmaceutics. Therefore, this work proposes to thoroughly use such residual biomass in a biorefinery by a simultaneous, efficient and sustainable integration and operation of extraction processes to obtain phytochemicals and functional extracts. A thermochemical process known as gasification is implemented to produce syngas, which can be turned into fuels, chemicals, and energy such as methanol and synthetic gasoline. Furthermore, this review article describes the state of the art of each process and the concept of biorefinery.