Net Energy Analysis and Techno-Economic Assessment of Co-Production of Bioethanol and Biogas from Cellulosic Biomass

Co-production is a process based on the biorefinery concept that maximizes the benefit of biomass by reusing residue from the production of one product to produce others. In this regard, biogas is one of the most researched second products for the production of ethanol from cellulosic biomass. However, operating this scheme requires additional investment in biogas processing equipment. This review compiles data from research studies on the co-production of bioethanol and biogas from lignocellulosic biomass to determine which is more worthwhile: leaving the residue or investing more to benefit from the second product. According to previous research, ethanol stillage can be converted to biogas via anaerobic digestion, increasing energy output by 2–3 fold. Techno-economic studies demonstrated that the co-production process reduces the minimum ethanol selling price to a level close to the market price of ethanol, implying the possibility of industrializing cellulosic ethanol production through this scheme.

Cost and Environmental Benefits of Using Pelleted Corn Stover for Bioethanol Production

While the production costs and logistical benefits of biomass pelleting have been widely discussed in the literature, the downstream economic and environmental benefits of processing pelleted biomass have been largely neglected. To investigate those benefits, we performed a comparative techno-economic analysis and life cycle assessment of producing ethanol using loose and pelleted forms of biomass. Analyses of a 2000 metric tons (dry)/d biorefinery showed that using pelleted biomass is more economical than using loose or baled biomass. The lowest minimum ethanol selling price (MESP) for pelleted biomass was USD 0.58/gal less than the lowest MESP for loose biomass. Among all processing conditions analyzed, MESP for ethanol produced with pelleted biomass was always lower than when produced with loose biomass. Shorter pretreatment and hydrolysis times, higher pretreatment solids loadings, lower ammonia requirements, and reduced enzyme loadings were the primary factors contributing to lower MESP with pelleted biomass. Similarly, pelleted biomass also demonstrated a 50% lower life cycle greenhouse gas emission compared to loose biomass. Emissions from higher pelleting energy were offset by downstream advantage in lower chemical needs.

Is Sugarcane a Convenient Feedstock to Provide Ethanol to Oxygenate Gasolines in Mexico? A Process Simulation and Techno-Economic-Based Analysis

Sugarcane is a major crop produced in many tropical countries including Mexico and has been the basis of a well-established agroindustry. However, the variation in market prices and health concerns over the consumption of sugar are challenging the economics and sustainability of sugarcane growers and mills. This paper presents a techno-economic assessment of using existing production capacity of sugarcane in Mexico and the correspondent Mexican sugarcane mills for producing ethanol as gasoline oxygenate, in comparison to the export of excess sugar production. Using the most recent statistics, we found out that the bioethanol potential is of 849,260,499 L/year which can cover for 100% of the premium and magna gasoline demand in metropolitan area (MA) and 48% of premium gasoline in rest of the country areas (RoCAs) at 5.8% w/v blending (2.7% O2 w/v). This can be done by diverting the 20% sugar production excess to ethanol with the benefit of a higher gross netback of 308.3 USD/ton of sugarcane in comparison to 222.5 USD/ton of sugarcane when it is exported. Furthermore, a minimum ethanol-selling price (MESP) of 0.5211 USD/L was estimated, showing that ethanol might be competitive against methyl tert-butyl ether (0.50 USD/L FOB Gulf price) as gasoline oxygenate agent. Decarbonizing gasoline in Mexico through the use of ethanol might allow the abatement of 5,766.8 kg CO2/day when 20% sugar is used. Concerning the underconstruction Dos Bocas refinery in Tabasco State, southern Mexico, ethanol blend at 5.8% in gasolines might but also contribute to the abatement of 6.1% of CO2 emissions and the required sugarcane was estimated at 1 million tons per year. All these indicate that sugarcane has a great potential as a feedstock to produce first-generation ethanol as a gasoline oxygenate agent in Mexico.

Techno-Economic Evaluation of Food Waste Fermentation for Value-Added Products

Food waste (FW) is one of the most critical problems in the world. Most FW will be sent to landfills, generally accompanying some significant disadvantages to the surrounding environment. Fermentation is considered as another disposal method to deal with FW. In this study, using a techno-economic analysis (TEA) method, an evaluation of the economic impact of three different scenarios of FW fermentation is carried out. A SuperPro Designer V9.0 simulation was used to model a commercial scale processing plant for each scenario, namely, a FW fermentation process producing hydrolysis enzymes and featuring a 2-step distillation system, a FW fermentation process without enzymes, using a 2-step distillation system, and a FW fermentation process without enzymes, using a 1-step distillation system. Discounted cash flow analysis is used to estimate the minimum ethanol selling price (MESP), where the lowest MESP result of $2.41/gal ($0.64/L) of ethanol is found for the second aforementioned scenario, showing that, even without enzymes in FW fermentation, the product cost can be competitive when compared to the other scenarios considered in this study. This project thus reflects a significant positive economic impact while minimizing the environmental footprint of a commercial production facility.

Technoeconomic Assessment of Hybrid Organosolv–Steam Explosion Pretreatment of Woody Biomass

This study investigates technoeconomic performance of standalone biorefinery concepts that utilize hybrid organic solvent and steam explosion pretreatment technique. The assessments were made based on a mathematical process model developed in UniSim Design software using inhouse experimental data. The work was motivated by successful experimental applications of the hybrid pretreatment technique on lignocellulosic feedstocks that demonstrated high fractionation efficiency into a cellulose-rich, a hemicellulose-rich and lignin streams. For the biorefinery concepts studied here, the targeted final products were ethanol, organosolv lignin and hemicellulose syrup. Minimum ethanol selling price (MESP) and Internal rate of return (IRR) were evaluated as economic indicators of the investigated biorefinery concepts. Depending on the configuration, and allocating all costs to ethanol, MESP in the range 0.53–0.95 €/L were required for the biorefinery concepts to break even. Under the assumed ethanol reference price of 0.55 €/L, the corresponding IRR were found to be in the range −1.75–10.7%. Hemicellulose degradation and high steam demand identified as major sources of inefficiencies for the process and economic performance, respectively. Sensitivity of MESP and IRR towards the most influential technical, economic and market parameters performed.

Economic Analysis of Cellulosic Ethanol Production from Sugarcane Bagasse Using a Sequential Deacetylation, Hot Water and Disk-Refining Pretreatment

A new process for conversion of sugarcane bagasse to ethanol was analyzed for production costs and energy consumption using experimental results. The process includes a sequential three-stage deacetylation, hot water, and disk-refining pretreatment and a commercial glucose-xylose fermenting S. cerevisiae strain. The simultaneous saccharification and co-fermentation (SScF) step used was investigated at two solids loadings: 10% and 16% w/w. Additionally, a sensitivity analysis was conducted for the major operating parameters. The minimum ethanol selling price (MESP) varied between $4.91and $4.52/gal ethanol. The higher SScF solids loading (16%) reduced the total operating, utilities, and production costs by 9.5%, 15.6%, and 5.6%, respectively. Other important factors in determining selling price were costs for fermentation medium and enzymes (e.g. cellulases). Hence, these findings support operating at high solids and producing enzymes onsite as strategies to minimize MESP.