Production of phosphate biofertilizers as a booster for the techno-economic and environmental performance of a first-generation sugarcane ethanol and sugar biorefinery.

A B S T R A C T The intensive use of fertilizers and pesticides in agriculture has a significant economic and environmental impact worldwide. Biofertilizers (aka microbial inoculants) could be a potential alternative to decrease costs and the environmental footprint linked to the use of fertilizers while boosting productivity through biological processes. This work aimed to perform a techno-economic-environmental assessment of an industrial biofertilizer production facility integrated with a sugarcane ethanol biorefinery. To this end, systems engineering tools were employed concurrently with techno-economic-environmental analyses to assess the integration of the different processes and their feasibility. Three processes for biofertilizer production are proposed varying in terms of downstream processing and the use of single or double microorganisms. Our findings indicate that the integration of biofertilizer production can enhance the biorefinery’s NPV by as much as 137% in the most favorable scenario and by a minimum of 69% in the most unfavorable scenario. Regarding environmental consequences, in general, all scenarios demonstrate an improvement over the base scenario. Global sensitivity analysis showed that the solid-state fermentation and composite formulation steps of the biofertilizer process have the most substantial influence on both economic and environmental outcomes. The uncertainty analysis further unveils that the scenarios without fungus separation exhibited greater resilience in the face of market volatility. The retro-techno-economic study defined the economically viable region. Ultimately, this study demonstrates that the integration of biofertilizers into an ethanol and sugar biorefinery is a more sustainable alternative than the isolated biorefinery regarding the environmental and techno-economic aspects of sustainability

A plant wide aqueous phase chemistry model describing pH variations and ion speciation/pairing in wastewater treatment process models

There is a growing interest within the Wastewater Treatment Plant (WWTP) modelling community to correctly describe physico–chemical processes after many years of mainly focusing on biokinetics. Indeed, future modelling needs, such as a plant-wide phosphorus (P) description, require a major, but unavoidable, additional degree of complexity when representing cationic/anionic behaviour in Activated Sludge (AS)/Anaerobic Digestion (AD) systems. In this paper, a plant-wide aqueous phase chemistry module describing pH variations plus ion speciation/pairing is presented and interfaced with industry standard models. The module accounts for extensive consideration of non-ideality, including ion activities instead of molar concentrations and complex ion pairing. The general equilibria are formulated as a set of Differential Algebraic Equations (DAEs) instead of Ordinary Differential Equations (ODEs) in order to reduce the overall stiffness of the system, thereby enhancing simulation speed. Additionally, a multi-dimensional version of the Newton–Raphson algorithm is applied to handle the existing multiple algebraic inter-dependencies. The latter is reinforced with the Simulated Annealing method to increase the robustness of the solver making the system not so dependant of the initial conditions. Simulation results show pH predictions when describing Biological Nutrient Removal (BNR) by the activated sludge models (ASM) 1, 2d and 3 comparing the performance of a nitrogen removal (WWTP1) and a combined nitrogen and phosphorus removal (WWTP2) treatment plant configuration under different anaerobic/anoxic/aerobic conditions. The same framework is implemented in the Benchmark Simulation Model No. 2 (BSM2) version of the Anaerobic Digestion Model No. 1 (ADM1) (WWTP3) as well, predicting pH values at different cationic/anionic loads. In this way, the general applicability/flexibility of the proposed approach is demonstrated, by implementing the aqueous phase chemistry module in some of the most frequently used WWTP process simulation models. Finally, it is shown how traditional wastewater modelling studies can be complemented with a rigorous description of aqueous phase and ion chemistry (pH, speciation, complexation)