From technical feasibility to systemic viability: valorising semi-natural grassland biomass in a conservation-driven bioeconomy.

Semi-natural grasslands (SNGs) are biodiversity-rich cultural landscapes maintained through conservation-driven mowing and grazing, generating recurrent streams of heterogeneous lignocellulosic biomass. Although this biomass represents a potential resource within a circular bioeconomy, its late harvest timing, elevated ash and mineral contents, high botanical variability and dispersed spatial distribution fundamentally differentiate it from woody biomass and intensively managed energy crops. Here we provide a critical synthesis of ecological constraints, technological valorisation pathways and techno-economic evidence for SNG biomass utilisation across Europe. By integrating technology readiness level (TRL) analysis with techno-economic assessment (TEA), we show that technical maturity alone is an insufficient indicator of practical suitability. Generic TRL classifications frequently overestimate applicability because they do not account for feedstock-specific constraints inherent to conservation-derived biomass. Across the reviewed literature, economic feasibility consistently emerges only for integrated, low-complexity energy pathways-most notably co-digestion in existing anaerobic digestion systems and fractionation-based concepts such as IFBB-where infrastructural integration, mineral reduction and multi-output recovery mitigate feedstock heterogeneity. In contrast, stand-alone bioenergy facilities and advanced biorefinery routes remain economically marginal or insufficiently assessed. We argue that feedstock-sensitive systems analysis, regional aggregation and coherent policy alignment between biodiversity conservation and bioeconomy strategies are essential to transform SNG biomass from a management by-product into a structurally viable component of a multifunctional bioeconomy.