Eucalyptus plantations as bio-photovoltaic systems: An integrated energy conversion analysis

The transition toward low-carbon energy systems has intensified the search for analytical approaches linking renewable energy sources to stable and transportable energy carriers. This study proposes a systems-based analytical framework for evaluating eucalyptus plantations as bio-photovoltaic systems, in which solar radiation is captured, transformed, and stored through coupled biological and thermochemical processes. The methodology integrates solar energy input, biomass production, and charcoal conversion into a unified analytical structure to quantify energy flows and performance indicators. Results indicate a solar-to-biomass conversion efficiency of approximately 0.55% and a biomass-to-charcoal efficiency of 63%, resulting in a global energy conversion efficiency of 0.35%. Despite this relatively low conversion efficiency, the system exhibited a high operational Energy Return on Investment (EROI ≈ 17.89) within the defined system boundary, indicating a strong energy return relative to the external operational energy input considered. This apparent contrast demonstrates the importance of jointly evaluating conversion efficiency and energy return when assessing renewable energy systems. Scenario and sensitivity analyses showed that biomass productivity and carbonization efficiency primarily influence solar-energy conversion and storage, whereas operational energy inputs primarily affect operational energy return. These findings indicate that improvements in silvicultural practices and thermochemical processes are key to enhancing system performance. Overall, the proposed framework provides a consistent approach for evaluating forest-based bioenergy systems and supports the conceptualization of eucalyptus plantations as bio-photovoltaic systems capable of capturing, converting, and storing solar energy through coupled biological and thermochemical processes, while offering a basis for comparative assessment of forest-derived renewable energy pathways under defined operational conditions.