The integral use of aromatic plants: prefeasibility comparison of stand-alone and biorefinery processes using thyme (Thymus vulgaris) as base case

Abstract

The use of lignocellulosic biomass to produce commercial high-value products has taken force in recent years. Aromatic plants are key raw materials to obtain bioactive compounds with high added value, such as phenolic compounds, but its extraction produces a high amount of wastes. In this sense, the present work aimed to evaluate experimentally the extraction of phenolic compounds from thyme and subsequently, the production of biogas from the remaining of the extraction. To evaluate the prefeasibility of the processes, the simulations of the stand-alone (conventional extraction), as well as the biorefinery (phenolic compounds extraction, biogas production, and a cogeneration system), were carried out and evaluated according to technical, economic, and environmental approaches. The bioactive compound extraction yield was 11.95% (w/w) and the methane yield was 114 ml/g volatile solids. In the present work, it was suggested that the stand-alone process becomes to be profitable from a small scale (23 T/day) in comparison with the biorefinery approach, which needs to be worked on a major scale (61 T/day) to be economically feasible. The comparison of the environmental impact generated by each scheme shows the major impact for the biorefinery case.