A comparative study on pine needle-based energy generation: Perspectives on techno-economics and sustainability

A comprehensive techno-economic analysis (TEA) was conducted for a hypothetically scaled up system (1.5 ton per day) to compare these three pathways based on energy input, biofuel yield, and economic viability. The energy input for a 1.5 ton per day (TPD) biogas plant with physicochemical pretreatment and co-digestion was 2369 kW h/ton, generating 586 m³ of methane (CH₄) daily. The 1.5 TPD pyrolysis plant working at 577 °C yields 405 kg bio-oil and 585 kg biochar with a total energy input of 7846 kW h per ton of feedstock. The 1.5 TPD torrefaction plant, at 350 °C for 60 min, generates 829 kg of briquettes requiring input energy of 8814 kW h per ton of biomass. Economic analysis indicates that anaerobic digestion achieved a profit of INR 115.28 lakh per annum with a production cost of INR 30/m³, and a payback period of 1.29 years, while pyrolysis and torrefaction exhibited profits of INR 51.64 lakh and INR 26.83 lakh yearly, with a production cost of INR 62.56/kg and INR 13.33/kg having corresponding payback in 1.45 and 2.92 years, respectively. Profitability metrics and cost distribution highlight that feedstock cost, energy consumption, and product market prices significantly influence profitability. Among the three pathways, anaerobic digestion is the most economically viable option, with a Return on Investment (ROI) of 68.56 %. This study emphasizes the need of TEA for commercial scalability based on the data of lab scale and bench scale.