Insights from a New Potential Obtainable Products from the End-cycle of an Industrial Agroforestry-plantation of MRF Poplar and Fiber-sorghum

The transition toward a circular bioeconomy requires innovative cropping systems that maximize biomass production without competing with food crops for prime agricultural land [1-3]. Short-rotation and medium-rotation forestry (MRF) plantations, popular in the 1990s and 2000s, have faced declining adoption due to market challenges and lower profitability compared to traditional crops. This study evaluates an innovative agroforestry model designed by CREA-IT to repurpose mature MRF poplar (Populus spp.) plantations at the end of their lifecycle [4]. By removing alternate rows, the original 3x1 m tree spacing was converted into a 6x1 m layout, enabling the inter-row cultivation of fiber sorghum (Sorghum bicolor L.) [5]. Field trials assessed biomass yields, biophysical crop compatibility, and post-harvest blending scenarios. Results demonstrated that while inter-row sorghum yields were lower (1.2 Mg ha.¹) than marginal monocultures (1.9 Mg ha.¹), the poplar trees exhibited enhanced growth, with total woody biomass increasing from 5000 kg to 6400 kg between 2023 and 2024 due to reduced inter-plant competition. End-cycle simultaneous harvesting (SH) simulations generated a naturally blended biomass stream containing approximately 16% sorghum. Biomass quality analysis revealed that increasing the proportion of sorghum significantly lowered the overall moisture content (from 50% in 100% poplar to 36% in 100% sorghum), optimizing drying rates and material stability during covered storage [1-14]. This multi-functional agroforestry framework provides a sustainable pathway for high-efficiency biomass production on marginal lands.