Analysis and control of a carbon dioxide removal model

Lakshmi Narayan Sridhar — 2025-12-31

Carbon dioxide removal from the atmosphere has emerged as one of the most critical strategies in responding to the accelerating climate crisis. It is important to develop rigorous and beneficial strategies and take steps to remove carbon dioxide from the atmosphere. In this study, bifurcation analysis and multi-objective nonlinear model predictive control are performed on a carbon dioxide removal model. Bifurcation analysis is a powerful mathematical tool used to address the nonlinear dynamics of various processes. Several factors must be considered, and multiple objectives must be met simultaneously. The MATLAB program MATCONT was used to perform the bifurcation analysis. The MNLMPC calculations were conducted using the optimization language PYOMO in conjunction with state-of-the-art global optimization solvers IPOPT and BARON. The bifurcation analysis revealed the existence of limit points. The MNLMPC converged to the Utopia solution. The limit points, which cause multiple steady-state solutions from a singular point, are highly beneficial because they enable the multi-objective nonlinear model predictive control calculations to converge to the Utopia point, representing the best possible solution in the model.

Enhanced bio-oil production and fatty acid extraction from pyrolyzed spent coffee ground using Box-Behnken design optimization

Tasya Muhamad Yasser — 2025-12-31

The disposal of spent coffee grounds (SCG), a biomass waste generated from coffee brewing, poses a significant environmental concern due to its high organic content and large volume. To address this issue, a valorization approach was undertaken that involved the production of bio-oil from SCG through pyrolysis and the subsequent extraction of oleic acid, the most abundant fatty acid in SCG. A Box-Behnken experimental design was employed to optimize pyrolysis yields using three process parameters: SCG particle size (<0.25, 0.25 – 0.70, 0.70 – 1.70 mm), pyrolysis temperature (500 – 600 °C), and nitrogen flow rate (0.5 – 1.5 L/min). Pyrolysis was conducted in a fixed-bed reactor, and the resulting bio-oil was characterized using gas chromatography. Statistical analysis indicated that all three parameters significantly influenced the bio-oil yield, with temperature and spent coffee grounds (SCG) particle size being the primary factors affecting fatty acid concentration. The optimal conditions identified included an SCG particle size of less than 0.25 mm, a temperature of 550°C, and a nitrogen flow rate of 0.5 L/min, which yielded a bio-oil production of 34.13%. Oleic acid was successfully extracted from the pyrolyzed bio-oil through liquid-liquid extraction using hexane, demonstrating its potential for further chemical processing. These findings illustrate a dual valorization pathway for SCG, enabling the production of both renewable bio-oil and oleic acid as platform bio-based chemicals.

International Journal of Chemical and Process Engineering Research

Analysis and control of a carbon dioxide removal model

Enhanced bio-oil production and fatty acid extraction from pyrolyzed spent coffee ground using Box-Behnken design optimization