A comprehensive analysis of bioethanol and ethyl lactate joint production in second-generation biorefinery: Simulation, techno-economic, and profitability assessments.

Second-generation biorefineries (2GBR) represent an innovative application of bioresources technologies to produce bioenergy and valuable products. This paper aims to introduce and analyze the joint production of bioethanol and ethyl lactate in a 2GBR. Techno-economic and profitability perspectives are considered in the analysis which is conducted via simulation considering corn stover as raw material. A key aspect in the analysis is a joint production parameter named α, whose values can dictate either the sole production of bioethanol (α = 0), joint production (0 < α < 1), or the unique production of ethyl lactate (α = 1). In other words, the proposed joint production scheme provides versatility in production. Simulations show that the lowest Total Capital Investment, Unit Production Cost, and Operating Cost values were associated with low values of α. Furthermore, when α ≥ 0.4, the 2GBR under study can achieve internal rates of return above 30%, which implies that the project offers a potentially high profitability.

Parameter Estimation of Dynamic Beer Fermentation Models.

In this study, two dynamic models of beer fermentation are proposed, and their parameters are estimated using experimental data collected during several batch experiments initiated with different sugar concentrations. Biomass, sugar, ethanol, and vicinal diketone concentrations are measured off-line with an analytical system while two on-line immersed probes deliver temperature, ethanol concentration, and carbon dioxide exhaust rate measurements. Before proceeding to the estimation of the unknown model parameters, a structural identifiability analysis is carried out to investigate the measurement configuration and the kinetic model structure. The model predictive capability is investigated in cross-validation, in view of opening up new perspectives for monitoring and control purposes. For instance, the dynamic model could be used as a predictor in receding-horizon observers and controllers.

Enhancement of alkaline-oxidative delignification of wheat straw by semi-batch operation in a stirred tank reactor.

This paper compares a semi-batch operation and a conventional one of an alkaline oxidative pretreatment of wheat straw carried out in a stirred tank reactor. For the pretreatment, different concentrations of biomass (6% up to 12% w/v) and two different particle sizes (mesh #40-60 and #>60) were experimented. The performance of processes was evaluated through the analysis of lignocellulosic composition of the biomass, and the enzymatic hydrolysis of pretreated biomass using the Cellic® CTec2 enzyme complex by Novozymes®. The process time of semi-batch operation is significantly lower than the batch one and enables a higher load of biomass, showing a delignification yield between 55 and 60%. In the first 5 h of reaction time, the enzymatic hydrolysis experiments reached their maximum yields of 72 and 66% according to reducing sugars conversion when using the mesh #>60 mesh and #40-60, respectively.

Biogas purification via optimal microalgae growth: A literature review.

In this review, we compare works from the current decade that address the CO2 -removal from biogas by means of microalgae. The microalgae culture process acts as a biochemical absorption process; it is potentially competitive with respect to classical and commercial absorption methods due to its additional benefits such as availing CO2 for the production of valuable microalgae biomass and being an environmentally friendly technique. Nevertheless, the low yield of biogas purification translates into the need to use optimal operation strategies that render the whole biogas production process economically feasible. A class of these strategies requires models capable of reproducing key traits of the dynamical behavior of microalgae growth. Thus, without overlooking the classical physico-chemical methods for biogas purification, our literature review addresses: (i) biogas purification via microalgae and different microalgae growth conditions, (ii) approaches that maximize microalgae growth, in order to increase CO2 -consumption, and (iii) different models that describe the representative characteristics of microalgae growth. This investigation traces a pathway to future considerations on optimal biogas purification alternatives by microalgae culture processes. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:1513-1532, 2018.