Microalgae biorefineries offer a route to sustainable fuels, yet most techno-economic analyses (TEAs) and life cycle assessments (LCAs) address narrow product portfolios within cradle-to-gate boundaries. This study presents the first cradle-to-grave TEA and LCA of a commercial-scale, continuous-mode, wastewater-fed photobioreactor (PBR) biorefinery producing 1,000,000 gal/yr biodiesel while treating ≈8.9 million m3/yr of tertiary wastewater through five-tier cascading valorization of Chlorella vulgaris biomass. Three scenarios were modeled in SuperPro Designer and SimaPro: a biodiesel-plus-fertilizer baseline (S1); added pigment extraction and enzymatic protein hydrolysis (S2); and a full cascade adding two-stage biohythane recovery via dark fermentation and co-digestion (S3). Cascading valorization raised co-product revenue by ∼600%, cutting the minimum fuel selling price (MFSP) from $198.22 to $158.06/gal (−20.3%); S3 yielded a statistically indistinguishable $159.99/gal, and Monte Carlo simulation confirmed robust separation of S2/S3 from S1. The LCA (ReCiPe Midpoint) showed that PBR cultivation electricity (345 kWh/gal; 90.4% of process-electricity demand) dominated 17 of 18 impact categories, making grid decarbonization the primary improvement lever. Absolute impacts are specific to the fossil-dominated GCC grid, whereas the cultivation-electricity hotspot and the relative effects of cascading valorization generalize across electricity mixes. Valorization deepened land-use credits 3.2-fold via soy-protein displacement but shifted burdens toward water consumption and terrestrial ecotoxicity. Pigment price and electricity cost dominated the sensitivity analysis; under moderate co-product pricing ($7/kg protein, $300/kg pigments), MFSP fell to $16.92–18.73/gal (∼89% reduction). Economic allocation per ISO 14044 reduced the biodiesel-attributed GWP to ≈13.5–13.8 kg CO2-eq/gal, approaching fossil-diesel parity as co-products absorb most of the burden.
Recently, CO2 emissions have been identified as the primary contributor to climate change; therefore, there is an urgent need to remove excess CO2 from the atmosphere. CO2 capture is the most promising approach to address this problem and is considered one of the best potential solutions. The synthesis of mesoporous MgO nano-particles modified with carbon as effective, high-capacity CO2 adsorbents was carried out using various surfactants, including CTAB, F127, P123, Triton X-100, and SDBS, which served as both carbon sources and structure-directing agents. The resulting powder was calcined at 800 degrees C in N2 to produce MgO-N2-CTAB, MgO-N2-F127, MgO-N2-SDBS, MgO-N2-P123, and MgO-N2-X100. Another portion of powder was calcined directly at 450 degrees C in air, yielding MgO-O2-CTAB, MgO-O2-F127, MgO-O2-SDBS, MgO-O2-P123, and MgO-O2-X100. Results showed that the CO2 adsorption capacity of MgO-O2-SDBS (1.781 mmol/g) was 4.68 times greater than that of unmodified MgO nanoparticles (0.38 mmol/g). The highest CO2 capture capacity, approximately 3.755 mmol/g, was achieved with the MgO-N2-SDBS adsorbent at 273 K and 760 mmHg. Interestingly, the CO2 adsorption capacity of MgO-N2-SDBS (3.755 mmol/g) was 2.11 times higher than that of MgO-O2-SDBS prepared in oxygen (1.781 mmol/g). This difference is attributed to the increased presence of C1s (1.33% atomic percentage) in the MgO lattice, as confirmed by XPS analysis. Additionally, S 2p signals were detected for MgO-O2-SDBS, corresponding only to the oxidized state of sulfur (SOx), since SDBS contains sulfur. The presence of accessible pores, combined with the sufficient Lewis basicity of MgO, played a crucial role in enhancing CO2 adsorption over MgO-O2-SDBS. The MgO-N2-SDBS sample exhibited the highest adsorbent capacity among all synthesized samples according to the results of Henry's law constants and isosteric heats of adsorption, indicating its strong ability to interact with CO2 molecules. The prepared sorbents maintained only slight reductions in capacity over ten consecutive CO2 sorption-desorption cycles, demonstrating good recyclability and stability.
A subgraph of the square lattice with all of its inner faces being 4-cycles is called a square-cell configuration. Prior work has provided explicit expressions for the total and average distances between vertex pairs in symmetric square-cell configurations, including well-structured families such as hexagonal square-cell configurations H(n), trapezium square-cell configurations T(n,k), and bitrapezium square-cell configurations BT(n,k_1,k_2). In this article, we further extend the square-cell configuration from regular boundaries to irregular boundaries, which do not exhibit complete regularity or symmetry in their structure. We find the generalized expressions for the Wiener index and average distance of such irregular configurations, incorporating combinatorial and structural variations. Our results demonstrate how irregularity affects the growth and distribution of pairwise distances and provide a unifying framework that includes both symmetric and asymmetric square-cell graphs as exceptional cases. This generalization provides novel insights into the structural behaviour of square-cell frameworks characterized by complex or perturbed geometries.
This paper introduces a Bezier-based function for suppressing oscillatory behavior in mechanical systems with nonzero initial conditions. A rigorous mathematical framework is developed to model system dynamics and generate feasible excitation profiles that eliminate residual oscillations while meeting prescribed final conditions. A formulated Bezier function is introduced into the system’s governing equation, a second order ordinary differential equation, and solved analytically. Numerical simulations across a range of operating cases validate the effectiveness of the proposed method, while critical scenarios are examined to reveal its limitations. The results confirm that the approach successfully reduces oscillations and guarantees precise attainment of target states. Furthermore, analysis of system kinematics demonstrates the capability of the method to achieve smooth and reliable motion. Overall, the study establishes a flexible and robust strategy for enhancing the safety and performance of mechanical systems under diverse operating environments.
PurposeWhen are organizations more or less likely to acquire external knowledge through purchasing management consulting services? The author argues that the difficulty of the decision problem and the complexity of the solution landscape increase the necessity and value of external management knowledge acquisition. The purpose of this study is to examine determinants of cross-country differences in management consulting spending. The author draws from the organizational search literature, the knowledge-based theory of the firm and transaction cost economics to develop the research hypotheses.Design/methodology/approachThe author empirically investigates the effect of a country's economic complexity, knowledge economy and transaction costs on management consulting using cross-country panel data of 24 European countries between 2004 and 2011 as well as hybrid random effects generalized least squares regressions.FindingsThe author documents that organizations are more likely to buy management consulting services when they navigate a complex economic landscape or compete in a knowledge-based economy. Furthermore, the author finds support for the negative effect of transaction costs in an economy on a country's management consulting expenditures.Originality/valueThe results of this study provide contributions to the literature on business knowledge purchasing and management consulting research.
