Insights into the economic viability of cellulases recycling on bioethanol production from recycled paper sludge.

The economics of Recycled Paper Sludge conversion into ethanol was here assessed with emphasis on integrating a cellulase recycling system. Without cellulases recycling this process presented positive economic outputs (payback period of 7.85 years; 10.90 Million US$ of accumulated NPV) despite the modest ethanol titers. Recycling both free and solid-bound enzymes allowed considerable savings of enzyme but also an increase on annual costs (0.88%), resulting on a superior economic output: payback period decreased to 7.25 years; accumulated NPV increased to 14.44 Million US$. Recycling exclusively the liquid fraction enabled a clear costs reduction, however, also total ethanol decreased, attenuating the abovementioned benefits. Targeting higher ethanol concentrations, superior solids consistencies were also evaluated. Despite a costs reduction, total ethanol decreased due to a higher ethanol retention on the solid. A sensitivity analysis further revealed that the cost of enzymes and ultrafiltration membrane may be critical on enzyme recycling economic feasibility.

Energetic and environmental assessment of thermochemical and biochemical ways for producing energy from agricultural solid residues: Coffee Cut-Stems case.

Forest residues are an important source of biomass. Among these, Coffee Cut-Stems (CCS) are an abundant wood waste in Colombia obtained from coffee crops renovation. However, only low quantities of these residues are used directly in combustion processes for heating and cooking in coffee farms where their energy efficiency is very low. In the present work, an energy and environmental assessment of two bioenergy production processes (ethanol fermentation and gasification) using CCS as raw material was performed. Biomass gasification seems to be the most promising thermochemical method for bioenergy production whereas, ethanol fermentation is a widely studied biochemical method to produce biofuels. Experimental runs of the CCS gasification were carried out and the synthesis gas composition was monitored. Prior to the fermentation process, a treatment of the CCS is required from which sugar content was determined and then, in the fermentation process, the ethanol yield was calculated. Both processes were simulated in order to obtain the mass and energy balance that are used to assess the energy efficiency and the potential environmental impact (PEI). Moderate high energy efficiency and low environmental impacts were obtained from the CCS gasification. In contrast, high environmental impacts in different categories and low energy efficiencies were calculated from the ethanolic fermentation. Biomass gasification seems to be the most promising technology for the use of Coffee Cut-Stems with high energy yields and low environmental issues.

A biorefinery for efficient processing and utilization of spent pulp of Colombian Andes Berry (Rubus glaucus Benth.): Experimental, techno-economic and environmental assessment.

This work investigated a model biorefinery for producing phenolic compounds extract, ethanol and xylitol from spent blackberry pulp (SBP). The biorefinery was investigated according to four potential scenarios including mass and heat integrations as well as cogeneration system for supplying part of the energy requirements in the biorefinery. The investigated SBP had 61.54% holocellulose; its total phenolic compounds was equivalent to 2700mg of gallic acid/100g SBP, its anthocyanins content was 126.41mg/kg of SBP and its total antioxidant activity was 174.8µmol TE/g of SBP. The economic analysis revealed that the level of integration in the biorefinery significantly affected the total production cost. The sale-to-total-production-cost ratio indicated that both, mass and heat integrations are of importance relevance. The cost of supplies (enzymes and reagents) had the most significant impact on the total production cost and accounted between 46.72 and 58.95% of the total cost of the biorefinery.

Comparison of lignin extraction processes: Economic and environmental assessment.

This paper presents the technical-economic and environmental assessment of four lignin extraction processes from two different raw materials (sugarcane bagasse and rice husks). The processes are divided into two categories, the first processes evaluates lignin extraction with prior acid hydrolysis step, while in the second case the extraction processes are evaluated standalone for a total analysis of 16 scenarios. Profitability indicators as the net present value (NPV) and environmental indicators as the potential environmental impact (PEI) are used through a process engineering approach to understand and select the best lignin extraction process. The results show that both economically and environmentally process with sulfites and soda from rice husk presents the best results; however the quality of lignin obtained with sulfites is not suitable for high value-added products. Then, the soda is an interesting option for the extraction of lignin if high quality lignin is required for high value-added products at low costs.

Economic and environmental assessment of syrup production. Colombian case.

This work presents a techno-economic and environmental assessment of the glucose syrups production from sugarcane bagasse, plantain husk, cassava husk, mango peel, rice husk and corncobs. According to the economic analysis, the corncob had both, the lowest production cost (2.48USD/kg syrup) and the highest yield (0.61kgofsugars/kg of wet agroindustrial waste) due to its high content in cellulose and hemicellulose. This analysis also revealed that a heat integration strategy is necessary since the utilities consumption represent an important factor in the production cost. According to the results, the pretreatment section requires more energy in the syrup production in comparison with the requirements of other sections such as production and sugar concentration. The environmental assessment revealed that the solid wastes such as furfural and hydroxymethylfurfural affected the environmental development of the process for all the agroindustrial wastes, being the rice husk the residue with the lowest environmental impact.

Techno-economic analysis for brewer's spent grains use on a biorefinery concept: the Brazilian case.

A techno-economic analysis for use of brewer's spent grains (BSG) on a biorefinery concept for the Brazilian case is presented. Four scenarios based on different levels of heat and mass integration for the production of xylitol, lactic acid, activated carbon and phenolic acids are shown. A simulation procedure using the software Aspen Plus and experimental yields was used. Such procedure served as basis for the techno-economic and environmental assessment according to the Brazilian conditions. Full mass integration on water and full energy integration was the configuration with the best economic and environmental performance. For this case, the obtained economic margin was 62.25%, the potential environmental impact was 0.012 PEI/kg products, and the carbon footprint of the processing stage represented 0.96 kg CO2-e/kg of BSG. This result served as basis to draw recommendations on the technological, economic and environmental feasibility for implementation of such type of biorefinery in Brazil.

Techno-economic analysis of bioethanol production from lignocellulosic residues in Colombia: a process simulation approach.

In this study a techno-economic analysis of the production of bioethanol from four lignocellusic (Sugarcane bagasse, Coffee cut-stems, Rice Husk, and Empty Fruit Bunches) residues is presented for the Colombian case. The ethanol production was evaluated using Aspen Plus and Aspen Process Economic Analyzer carrying out the simulation and the economic evaluation, respectively. Simulations included the composition of lignocellulosic residues, which was determined experimentally. It was found that empty fruit bunches presents the highest ethanol yield from a dry basis point of view (313.83 L/t), while rice husk produced less ethanol (250.56 L/t). The ethanol production cost was assessed for the standalone ethanol plant and the ethanol plant coupled with a cogeneration system. Moreover, ethanol production cost using EFB was the lowest with (0.49 US$/L) and without (0.58 US$/L) cogeneration scheme.

Techno-economic analysis for a sugarcane biorefinery: Colombian case.

In this paper a techno-economic analysis for a sugarcane biorefinery is presented for the Colombian case. It is shown two scenarios for different conversion pathways as function of feedstock distribution and technologies for sugar, fuel ethanol, PHB, anthocyanins and electricity production. These scenarios are compared with the Colombian base case which simultaneously produce sugar, fuel ethanol and electricity. A simulation procedure was used in order to evaluate biorefinery schemes for all the scenarios, using Aspen Plus software, that include productivity analysis, energy calculations and economic evaluation for each process configuration. The results showed that the configuration with the best economic, environmental and social performance is the one that considers fuel ethanol and PHB production from combined cane bagasse and molasses. This result served as the basis to draw recommendations on technological and economic feasibility as well as social aspects for the implementation of such type of biorefinery in Colombia.

Conceptual design of cost-effective and environmentally-friendly configurations for fuel ethanol production from sugarcane by knowledge-based process synthesis.

In this work, the hierarchical decomposition methodology was used to conceptually design the production of fuel ethanol from sugarcane. The decomposition of the process into six levels of analysis was carried out. Several options of technological configurations were assessed in each level considering economic and environmental criteria. The most promising alternatives were chosen rejecting the ones with a least favorable performance. Aspen Plus was employed for simulation of each one of the technological configurations studied. Aspen Icarus was used for economic evaluation of each configuration, and WAR algorithm was utilized for calculation of the environmental criterion. The results obtained showed that the most suitable synthesized flowsheet involves the continuous cultivation of Zymomonas mobilis with cane juice as substrate and including cell recycling and the ethanol dehydration by molecular sieves. The proposed strategy demonstrated to be a powerful tool for conceptual design of biotechnological processes considering both techno-economic and environmental indicators.

Analysis of the production process of optically pure D-lactic acid from raw glycerol using engineered Escherichia coli strains.

Glycerol has become an ideal feedstock for producing fuels and chemicals. Here, five technological schemes for optically pure D: -lactic acid production from raw glycerol were designed, simulated, and economically assessed based on five fermentative scenarios using engineered Escherichia coli strains. Fermentative scenarios considered different qualities of glycerol (pure, 98 wt.%, and crude, 85 wt.%) with concentrations ranging from 20 to 60 g/l in the fermentation media, and two fermentation stages were also analyzed. Raw glycerol (60 wt.%) was considered as the feedstock feeding the production process in all cases; then a purification process of raw glycerol up to the required quality was required. Simulation processes were carried out using Aspen Plus, while economic assessments were performed using Aspen Icarus Process Evaluator. D: -Lactic acid recovery and purification processes were based on reactive extraction with tri-n-octylamine using dichloromethane as active extractant agent. The use of raw glycerol represents only between 2.4% and 7.8% of the total production costs. Also, the total production costs obtained of D: -lactic acid in all cases were lower than its sale price indicating that these processes are potentially profitable. Thus, the best configuration process requires the use of crude glycerol diluted at 40 g/l with total glycerol consumption and with D: -lactic acid recovering by reactive extraction. The lowest obtained total production cost was 1.015 US$/kg with a sale price/production cost ratio of 1.53.