Technoeconomic Analysis & Life Cycle Assessment of Hydrogen Production Via Biomass Gasification

Abstract

Biomass gasification is a promising thermochemical process for converting organic waste into hydrogen-rich syngas, offering a sustainable alternative to fossil fuel-based energy production. This thesis presents a comprehensive techno-economic and environmental assessment of hydrogen production from food waste biomass. A steady-state equilibrium model was developed using Aspen Plus V14 based on the Gibbs free energy minimization principle. The model was validated against experimental data, achieving a root mean square error (RMSE) of 0.24, confirming its reliability for predicting syngas composition under various operating conditions.

A multi-parameter sensitivity analysis evaluated the impact of gasification temperature (600 - 950 °C), equivalence ratio (ER, 0.2 - 0.6), and steam-to-biomass ratio (S/B, 0.2-1.0) on syngas quality. Results indicate that increasing temperature and S/B ratio significantly enhances hydrogen yield; multi-objective optimization identified an optimal operating point at 793 °C, an ER of 0.2, and an S/B ratio of 0.586 to achieve a critical H_2/CO molar ratio of 2:1.

An economic evaluation was conducted to explore the industrial feasibility of the waste-to-hydrogen route. Hinging on the levelized cost of hydrogen (LCOH) the economic study evaluates a range of biomass feed rates (100 tons per day – 500 tons per day) and the feasibility was justified by the economy of scale.

In order to quantify the environmental impact of the process and confirm the sustainability claim, a life cycle assessment (LCA) was implemented on OpenLCA software with cradle-to-gate boundary. The results indicate that the overall global warming potential of the system amounts to 0.37 kg CO₂-eq per kg H₂, reflecting the combined effect of positive emissions from energy and utility consumption and negative emissions associated with avoided biomass landfilling

To evaluate the broader utility of the produced syngas, a Multi-Criteria Decision Analysis (MCDA) was performed to rank three downstream pathways: Methanol (MeOH) production, Fischer-Tropsch (FT) Syncrude synthesis, and Power Generation. While power generation offers the lowest technical complexity, methanol synthesis presented a superior environmental profile. However, the inclusion of a Social Life Cycle Assessment (S-LCA) utilizing the PSILCA method and SOCA database within a European Union (RER) context revealed a distinct trade-off between chemical complexity and social responsibility. This integrated TEA, LCA, and S-LCA approach demonstrates that while fuel synthesis offers high-value outputs, it incurs a higher "social cost”. The findings provide a strategic framework for stakeholders to balance technical viability and decarbonization targets with regional social sustainability priorities.