Green biorefinery (GBR) scenarios for a two-cut silage system: Investigating the impacts of sward botanical composition, N fertilisation rate and biomass availability on GBR profitability and price offered to farmers

In Ireland, grass is a readily available bioresource. It has previously been established that Green biorefinery (GBR) could become a potential use of Irish grasslands, and a blueprint for a sustainable GBR industry in Ireland has been developed. The objective of this paper is to use scenario analysis to investigate the sensitivity of the profitability of the GBR blueprint to variations in grass quantity and quality as a function of botanical composition, fertiliser application, and biomass availability. As an outcome of these scenario analyses, the price the GBR can offer to farmers above their production costs (€ t⁻¹ dry matter) was calculated. Results of the scenario analyses determined that GBR systems located in a catchment area of permanent pasture (Lolium perenne > 60%) with annual grass yields in the range of 9-12 t dry matter (DM) ha⁻¹, and supplied with grass biomass with a fibre content of 500-555 g kg⁻¹ DM and a protein content of 110-130 g kg⁻¹ DM, were viable. The most profitable scenarios were generated when nitrogen fertiliser application was greater than 90 kg ha⁻¹ a⁻¹. Biomass availability of less than 30% resulted in reduced profitability and for some scenarios resulted in a loss for both the GBR and farmer due to increased transport costs. Within the scenario assumptions of this study, grass feedstock was valued at €4-€56 t⁻¹ dry matter above production costs. However, this value depended on the yields and biomass availability of the GBR catchment area.