A non-linear programming model was developed to maximize the economic profit from an anaerobic co-digester. The model consists of a combination of technical and economic equations, linked through the biogas production variable. Five scenarios were simulated. These differed with regard to substrate inlet mass flow rate, organic loading rate and hydraulic retention time. The impact on biogas production was investigated and an economic analysis was undertaken based on the concepts of profitability and Net Present Value. The model results indicate that varying the substrate inlet mass flow rate and organic loading rate could have a positive impact on the profitability of co-digesters in Flanders. This can be achieved either by increasing the interval time between feedstock input, or by feeding individual streams of feedstock separately into the system, while at the same time reducing the hydraulic retention. time

This paper introduces a theoretical market framework (TMF) for conceptualizing and designing electricity markets, integrating transmission system operator and distribution system operator (TSO–DSO) coordination mechanisms. The TMF represents a comprehensive tool that formalizes new, innovative market concepts and their impact on existing markets, and outlines fundamental categories and decisions essential to market design. This paper, through the TMF, addresses the integration challenges posed by new mechanisms for system services. Utilizing the TMF, the study maps 13 European demonstrators’ TSO–DSO coordination solutions, identifying real-world challenges in designing and implementing novel system services markets. Drawing on these real-world insights, the paper offers market design and policy recommendations to address and overcome the specific challenges in market-based TSO–DSO coordination.