Production of volatile fatty acids by anaerobic digestion of biowastes: Techno-economic and life cycle assessments.

Production of volatile fatty acids from food waste and lignocellulosic materials has potential to avoid emissions from their production from petrochemicals and provide valuable feedstocks. Techno-economic and life cycle assessments of using food waste and grass to produce volatile fatty acids through anaerobic digestion have been conducted. Uncertainty and sensitivity analysis for both assessments were done to enable a robust forecast of key-aspects of the technology deployment at industrial scale. Results show low environmental impact of volatile fatty acid with food wastes being the most beneficial feedstock with global warming potential varying from -0.21 to 0.01 CO2 eq./kg of product. Food wastes had the greatest economic benefit with a breakeven selling price of 1.11-1.94 GBP/kg (1.22-2.33 USD) of volatile fatty acids in the product solution determined through sensitivity analysis. Anaerobic digestion of wastes is therefore a promising alternative to traditional volatile fatty acid production routes, providing economic and environmental benefits.

Fast spectroscopic monitoring of inhibitors in the 2G ethanol process.

One of the main challenges of second generation (2G) ethanol production is the high quantities of phenolic compounds and furan derivatives generated in the pretreatment of the lignocellulosic biomass, which inhibit the enzymatic hydrolysis and fermentation steps. Fast monitoring of these inhibitory compounds could provide better control of the pretreatment, hydrolysis, and fermentation processes by enabling the implementation of strategic process control actions. We investigated the feasibility of monitoring these inhibitory compounds by ultraviolet-visible (UV-Vis) spectroscopy associated with partial least squares (PLS) regression. Hydroxymethylfurfural, furfural, vanillin, and ferulic and p-coumaric acids generated during different severities of liquid hot water pretreatment of sugarcane bagasse were quantified with highly accuracy. In cross-validation (leave-one-out), the PLS-UV-Vis method presented root mean square error of prediction (RMSECV) of around only 5.0%. The results demonstrated that the monitoring performance achieved with PLS-UV-Vis could support future studies of optimization and control protocols for application in industrial processes.

Monitoring of the cellulosic ethanol fermentation process by near-infrared spectroscopy.

Rapid, efficient, and low-cost technologies for monitoring the fermentation process during second generation (2G) or cellulosic ethanol production are essential for the successful implementation of this process at the commercial scale. Here, the use of near-infrared (NIR) spectroscopy associated with partial least squares (PLS) regression was investigated as a tool for monitoring the production of 2G ethanol from lignocellulosic sugarcane residues including bagasse, straw, and tops. The spectral data was based on a set of 103 alcoholic fermentation samples. Models based on different pre-processing techniques were evaluated. The best root mean square error of prediction (RMSEP) values obtained in the external validation were around 3.02 g/L for ethanol and 6.60 g/L for glucose. The findings showed that the PLS-NIR methodology was efficient in accurately predicting the glucose and ethanol concentrations during the production of 2G ethanol, demonstrating potential for use in monitoring and control of large-scale industrial processes.