Bioethanol Plant Research Articles

Life-Cycle GHG Emissions of Cassava-Based Bioethanol Production

This study aims to assess the life-cycle greenhouse gas (GHG) emissions of cassava ethanol production system focusing on utilization of biomass and biogas as energy sources in the steam production process. Scope of life cycle assessment is “cradle to gate” and the functional unit of this study is 1 liter of anhydrous ethanol produced. The use of biogas from wastewater treatment system for steam production greatly affects the GHG reduction. The GHG emissions of bioethanol plant that uses biogas from wastewater for steam production is 0.548 kg-CO2-eq/L-ethanol, while the bioethanol plant without biogas utilization is 1.031 kg-CO2-eq/L-ethanol. From the result, the utilization of biogas in steam production insignificantly reduce the GHG emission, if primary fuel in steam production is biomass. In contrast, using biomass such as wood chip and rice husk substitutes for fossil fuel as primary fuel in steam production greatly affects to GHG emission reduction (approximately 96% reduction compared to literature).

Techno-economic evaluations for feasibility of sago-based biorefinery, Part 2: Integrated bioethanol production and energy systems

To reduce reliance on fossil fuel and environmental issues, alternative energy sources such as biomass are vital to be recovered and converted into value-added products. In sago industry, a huge amount of sago biomass (i.e., sago barks and fibres) is generated and discharged to the environment during sago starch extraction process (SSEP). In order to reduce environmental pollutants, the biomass can be utilised as feedstocks for energy, and bioethanol production. Therefore, Part 1 of these articles in series presents a techno-economic analysis to examine the feasibility of sago biomass-based combined heat and power (CHP) system (Wan et al., 2015a); and Part 2 is to examine the feasibility of integrated bioethanol production and energy systems. In this part, a conceptual integrated sago-based biorefinery (SBB) is envisioned and analysed based on the bioethanol plant study conducted by the National Renewable Energy Laboratory (NREL). Besides, techno-economic performance as well as environmental performance of this integrated SBB is evaluated via Aspen Plus software and a spreadsheet based yield prediction model. For the performance evaluation, various feedstocks such as sago fibres, barks and combined biomass (fibres and barks) are considered. In addition, techno-economic and environmental performance of the integrated SBB with on-site and off-site enzyme production as well as the impacts of labour cost on the economic performance of the integrated SBB is also evaluated. Based on the evaluation and analysis, the integrated SBB with combined biomass (fibres and barks) has the highest technical, economic and environmental performance amongst the sago biomass. A total of 4.75t/d of bioethanol and 252kW/d of electricity are expected to be produced; and reduction of 16.32 tCO2equivalent/d of carbon dioxide emission is expected. In addition, the payback period of the integrated SBB with on-site enzyme production and using current available labour from SSEP is estimated as 6.6 years. Based on the analysis, it is noted that enzyme and labour costs are critical cost contributors to the new development of the integrated SBB and hence, a sensitivity analysis on such parameters is performed.

Conceptual Design of an Operator Training Simulator for a Bio-Ethanol Plant

Conceptual design methodology for the configuration and procedural training with an operating training simulator (OTS) in a large-scale plant for commercial bio-ethanol production is described. The aim of the study is to show how the methodology provides a powerful way for finding the best configuration and training structure of the OTS before constructing and implementing the software of the OTS. The OTS principle, i.e., to use a computer-based virtual representation of the real process plant intended for efficient training of process operators, has long since been applied in aviation and process industries for more efficient and flawless operations. By using the conceptual design methodology (sometimes referred to as bio-mechatronics) a variety of OTS configurations with this capacity was generated. The systematic approach of for targeting the users’ (i.e., the plant management and process operators) needs resulted in better understanding and efficiency in training of hands-on skills in operating the plant. The training included general standard operating procedures for running the plant under normal operation conditions with different starch materials, handling of typical frequent disturbances as well as acting in situations not described in the standard operation procedures and applying trouble-shooting.

Techno-economic analysis (TEA) of low-moisture anhydrous ammonia (LMAA) pretreatment method for corn stover

Techno-economic analysis (TEA) plays an important role in assessing economic performance and potential market acceptance for new technologies. Previous work has shown that the construction and operation of a cellulosic bioethanol plant can be very expensive. One of the largest cost categories is pretreatment processing. The purpose of this study was to conduct a detailed cost analysis to assess low moisture anhydrous ammonia (LMAA) pretreatment process at the commercial-scale, and to estimate the breakeven point in large-scale production. In this study, capital expenses, including annualized purchase and installation fees, and annual operating costs associated with each unit operation were determined. The lowest unit cost obtained from this study was $3.86/gal, but it was still high compared with current gasoline price.

Development of Biofuels in China: Progress, Government Policies and Future Prospects

China is the largest energy consumer in the world, but has limited energy resources. Energy security is thus a primary concern for China. Over reliance on the consumption of fossil energy has resulted in severe environmental pollution, which puts pressure on the government to adjust its energy mix. To strengthen its energy supply and prevent further environmental degradation, China has been committed to developing renewable energies, such as biofuels.
 This article provides a comprehensive assessment of the development of biofuels, rural household biogas, and bioethanol, in particular. It also examines related government policies and the future prospects of the biofuel sector. The analysis shows that remarkable achievements have been made in the development of biogas in rural areas and in bioethanol at the industrial level. This progress is largely credited to government's strong support for the biofuel sectors. Nonetheless, although ongoing energy insecurity and environmental pollution continues to motivate the central government to support the development of biofuels, widening domestic food supply and demand gap, changes in rural life and agricultural industrialization constrain the further expansion of rural household biogas and cereal-based bioethanol. This article suggests that while China urgently needs to find alternative feedstock for the existing rural household biogas digesters and bioethanol plants, centralized biogas and non-cereal-based bioethanol projects should be prioritized for future development.

Stochastic optimization of sustainable industrial symbiosis based hybrid generation bioethanol supply chains

Bioethanol has been considered as an important type of renewable energy that can help reduce energy crisis and environmental degradation. Under economic, technology, and sustainability consideration, food based 1st generation bioethanol and lignocellulosic-based 2nd generation bioethanol have to exist simultaneously. Therefore, it is necessary to design a hybrid generation bioethanol supply chain (HGBSC) to sustainably meet the ever-increasing energy demand and different government-mandated sustainability standards related to green sustainability such as greenhouse gas (GHG) emissions, irrigation land and water usage, and energy efficiency. This paper is the first to examine different type of bioethanol plant configurations including industrial symbiosis strategy in order to meet high sustainability standards and design robust and sustainable industrial symbiosis based hybrid generation bioethanol supply chains (ISHGBSC). A novel stochastic mixed integer linear programming (SMILP) model is proposed to design the optimal ISHGBSC under different sustainability standards. A case study of North Dakota (ND) in USA has been studied as an application of the proposed model. The results show that some sustainability standards are stronger than others in terms of the number of green sustainability requirements met. When stronger sustainability standards are applied, the economic performance of the ISHGBSC is sacrificed. The results provide a guideline for policymakers to determine the appropriate standard to use under different sustainable concerns, and for policymakers and investors the best ISHGSBC structure under each standard. In addition, the results provide investors a guideline to invest in different technologies under different sustainability standards. Sensitivity analyses is also conducted to provide deep understanding of the proposed ISHGBSC and to identify the factors that might impact the stability of the ISHGBSC under different standards.

An Opinion Poll for the Establishment of a Bioethanol Plant Utilizing Local Resources and a Fuzzy Inference System

An Opinion Poll for the Establishment of a Bioethanol Plant Utilizing Local Resources and a Fuzzy Inference System

Is the pipeline hydro‐transport of wheat straw and corn stover to a biorefinery realistic?

AbstractPipeline hydro‐transport is an alternative to truck delivery of agricultural residue (lignocellulosic) biomass. Pipeline hydro‐transport benefits from economies of scale, reduces total delivery costs, and enables bio‐based energy facilities to achieve higher capacities. In this study, the empirical correlation based on experimentally developed data for pipeline transport of agricultural residue‐water mixtures (slurry) was used to develop a data‐intensive techno‐economic model to estimate the cost of pipeline hydro‐transport of wheat straw and corn stover to a bioethanol refinery. The total cost of pipeline hydro‐transport was found to be lowest at 8.8% dry matter slurry solid mass content and 2.5 m s−1 slurry velocity. At this biomass slurry solid mass content and velocity, the pipeline hydro‐transport of biomass was found to be economically more viable than truck delivery at capacities of 0.45 M dry t yr−1 or more for a one‐way pipeline and 1.4 M dry t yr−1 or more for a two‐way pipeline (with the return of the carrier liquid). The ability to economically hydro‐transport agricultural residue biomass in pipes offers the opportunity to develop large‐scale bioethanol plants. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd

Evaluating CO2 sources for power-to-gas applications – A case study for Austria

The intermittent nature of wind and solar power requires long-term energy storage options such as power-to-gas. This technology utilizes (surplus) electricity from renewable power sources to produce hydrogen in an electrolyzer. The produced hydrogen can be either directly utilized as an energy carrier or combined with CO2 and further converted to methane. This article evaluates different CO2 sources concerning their potential utilization within the power-to-gas energy storage technology with regard to capture costs, specific energy requirement and CO2 penalties. The results of a case study for Austria indicate that there is enough CO2 available from point sources to store all of the electricity produced from fluctuating renewable power sources (wind power plants and photovoltaics) via power-to-gas. Due to low capture costs, low CO2 penalties, biogenic origins, and short distances to wind power plants, biogas upgrading facilities and a bioethanol plant were determined to be the CO2 sources best suited for utilization in novel power-to-gas plants. However, as the total amount of CO2 produced from these facilities is relatively low in Austria, other CO2 sources would also be required. With moderate capture costs and CO2 penalties, power plants and an existing refinery could also provide CO2 for power-to-gas. Although large amounts of CO2 are available from iron, steel, and cement production facilities, these sources are not recommended for CO2 utilization in power-to-gas, as the CO2 penalty is relatively high and the facilities are rarely located near wind power plants in Austria.

Hierarchical economic potential approach for techno-economic evaluation of bioethanol production from palm empty fruit bunches

A hierarchical four-level approach to determine economic potential (4-level EP) is proposed for preliminary techno-economic analysis of new processes. The 4-level EP includes input/output structure, process flow structure, heat integration (HI), and economic feasibility. Two case studies on a 30.2t/d (or 12.7million l/yr) bioethanol plant with and without jet fuel production from palm empty fruit bunches (EFB) were investigated by applying the 4-level EP. The plant flowsheet was established based on experiments in a 0.1t/d pilot plant, including sequential dilute acid and alkali pretreatment, and separate hydrolysis and fermentation (SHF). EP approached a more reliable value through the hierarchical 4-level EP. The heating energy was reduced considerably by HI. The product value was estimated at $0.8–$1.3/kg of equivalent bioethanol. It was suggested through sensitivity analysis that a large plant size, enhanced production yields, and capital cost reduction were necessary for the lignocellulosic bioethanol production to be profitable.

Effect of precipitating agents on centrifugation and ultrafiltration performance of thin stillage digestate

The EU Renewable Energy Directive 2009/28/EC demands bioethanol plants to reduce their greenhouse gas emissions. This can be achieved by integrating a biogas plant in the bioethanol process and consequently by using the bioethanol by-products (e.g. thin stillage) as feedstock for anaerobic digestion. Due to the large amounts of thin stillage and consequently of digestate an efficient digestate treatment is essential. For this purpose centrifugation and ultrafiltration of thin stillage digestate with and without addition of precipitating agents were carried out. Prior to centrifugation, which was carried out with a disc-stack centrifuge at pilot scale, precipitating agents (iron(III)chloride and carbonated lime) were added. The produced supernatant fractions were then used for ultrafiltration experiments, which were carried out with a αAl2O3-membrane (pore size: 50nm). Cross flow velocity and trans membrane pressure were adjusted to 6ms−1 and to 0.8∗105Pa. The addition of precipitating agents increased the separation efficiency of the suspended solids from 46% to 75%. Furthermore the flux during ultrafiltration increased from 45–50Lm−2h−1 to 79Lm−2h−1. In addition, phosphorous could be practically entirely removed from the supernatant with the precipitating agents. For a large-scale bioethanol plant it was proposed to reutilise the digestate fractions as process water. However, depending on its influence on the process and on animal feed quality, different digestate treatment processes should be applied.

Activated Carbon from Lignin-based Black Liquor Coagulated by Polyaluminium Chloride

Black liquor obtained from the pretreatment process in bioethanol plant was coagulated by Polyaluminium Chloride (PACl). The optimum sludge was evaluated by varying PACl dosage. Further, the sludge from coagulation process was prepared for activated carbon with the physical activation process. The preparation was carried out with two different methods: single step activation and two-step activation. In single step activation, dried sludge of black liquor were activated directly using the furnace at 575̊C for 3 h. In two-step activation, dried sludge was carbonized at 575̊C for 3 h and subsequently activated with raised temperature at 725̊C for 1 h. Investigated properties of lignin PACl-based activated carbon in single (LPACl-based AC 1) and two-step activation (LPACl-based AC 2) in the present study included its surface area and peak component analysis. It was found that PACl 1% (w/v) dosage addition to black liquor in constant speed 200 rpm for 10 minutes followed by slow stirring process 50 rpm for 2 hours and 24 hours settlement served optimum coagulation behaviour to deliver precipitation. Surface area (SBET) of LPACl-based AC 1 was found higher than LPACl-based AC 2. This preliminary study was conducted to evaluate influence process variable for the further study of activated carbon production as utilization of black liquor to establish sustainable recycling process, consequently supported the environmental and practical value.

廃木材を原料としたバイオエタノール製造プラントの蒸留・精留プロセスにおけるpH制御による製品品質の改善と有機不純物の挙動

廃木材を原料としたバイオエタノール製造プラントの蒸留・精留プロセスにおけるpH制御による製品品質の改善と有機不純物の挙動

Sustainability and Economic Analysis of Propylene Carbonate and Polypropylene Carbonate Production Processes Using CO2 and Propylene Oxide

Currently, the industrially important polycarbonates are synthesized from bisphenol A and diphenyl carbonate, which are highly toxic and hence other feasible alternatives are preferable. Following the considerable advances on the catalyst for the synthesis of carbonates from CO2 and propylene oxide (PO), industrial scale processes for the productions of propylene carbonate (PC) and polypropylene carbonate (PPC) have been designed and simulated with sustainability and economic analyses. The CO2 is supplied by a nearby bioethanol plant, while the PO from a petrochemical process. The first part of the study is for the production of 200 million lb/year cyclic PC by using 9990 lb/ hr of CO2. Ionic liquid-1-n-ethyl-3-methylimidazolium chloride is used as a catalyst. The net CO2 emission reduction is around −0.318 lb CO2/lb PC, while the net cost of duty (heating+cooling) is around $1.92×10−3/lb PC. The second part is for the production of 261 million lb/year PPC by using 14523.2 lb/hr CO2. The process uses (salen) CrIIICl complex as catalyst. The net CO2 emission reduction is around −0.342 lb CO2/lb PPC, while the net cost of duty/lb PPC is around $7.978×10−3/lb PPC. Economic analyses show that the feasibility of the both production plants depends on the selling price of PC and PPC. Both the production plants for PC and PPC are sustainable as they use CO2 and avoid toxic feedstock. Beside the engineering economics, a focused sustainability analysis should also be considered in the feasibility evaluation of chemical process technologies.

Industrial-scale bioethanol production from brown algae: Effects of pretreatment processes on plant economics

Brown algae, considered as the third generation biomass, offer several advantages over lignocellulosic biomass. However, the current high cost of seaweed cultivation hampers the industrialization of macroalgae-based biofuel production. The aim of this study is to determine the maximum dry seaweed price (MDSP) as an upper limit for purchasing price of brown algae at bioethanol plant gates. In addition, a minimum ethanol-selling price (MESP) was calculated by considering the state-of-the-art bioethanol production technology and current brown algae-cultivation costs. A new simple pretreatment process was economically validated and compared with the traditional acid thermal hydrolysis known as combined pretreatment. The processes were simulated at the scales of 80,000 and 400,000ton/year of dry brown algae using the Aspen Plus v.8.4 software, and techno-economic models were developed based on mass and energy balance. MDSP for the simple and combined processes was calculated as 64.6 and 26$/ton (80,000ton/year) and 91.3 and 71.5$/ton (400,000ton/year), respectively. In addition, MESP for the simple and combined processes was determined as 2.39 and 2.85$/gal (80,000ton/year) and 2.08 and 2.33$/gal (400,000ton/year), respectively. These results indicate that the simple pretreatment is economically superior to the combined pretreatment. A comprehensive sensitivity analysis showed that seaweed price had the highest impact on MESP, thereby confirming that the cost-effective large-scale seaweed cultivation is the key to the success of macroalgae-based biofuel production.

Environmental Comparison of Straw Applications Based on a Life Cycle Assessment Model and Emergy Evaluation

Straw is considered to be a renewable resource for bioenergy and biomaterial. However, about 70% of straw is burned in fields, which causes serious air pollution in China. In this study, a life cycle assessment (LCA) model, together with emergy evaluation, was built to compare four straw applications after harvest vs. direct burning, including bioethanol (BE), combined heat and power plant (CHP), corrugated base paper (CP), and medium-density fiberboard (MDF). The results showed that BE and MDF would avoid greenhouse gas (GHG) emissions by 82% and 36%, respectively, while CHP and CP would emit 57% and 152% more GHG , respectively, compared with direct straw burning. Bioethanol had the highest renewability indicator (RI) of 47.7%, and MDF obtained the greatest profit of 657 Yuan•bale-1. The applications CHP and CP had low RI (< 10.3%) and profit (< 180 Yuan•bale-1). Due to water recycling and electrical power as a coproduct, BE had the lowest value (3 × 1011 sej•Yuan-1) of EmPM (emergy per unit money profit); the EmPM value of CP was 18.6 times higher than that of BE. The four straw applications would also greatly reduce particles emission (57 to 98%) to air. BE was judged to be the most environmentally friendly application among the four straw applications. Imposing a carbon tax would encourage investment in BE, but discourage the applications CHP and CP.

Heat integration of combined 1st and 2nd generation ethanol production from wheat kernels and wheat straw

Reducing the energy used in an ethanol plant is an important step towards reducing both the cost and environmental impact of the process. Pinch technology was used to analyze the energy utilization and to investigate possible energy savings in stand-alone and combined 1st and 2nd generation ethanol production plant designs. Different heat sources and sinks in the plant were identified to improve energy integration. Four different scenarios were evaluated using Aspen Plus, with heat exchanger networks generated in the simulation program Aspen Energy Analyzer. The total direct cost of the heat exchanger networks was calculated using Aspen Process Economic Analyzer. It was shown that heating costs could be reduced by 40-47% and cooling costs by 42-54% by heat integration. The sum of the discounted total direct cost for heat exchangers and annual cost of utilities was also lower in the heat integrated cases than in the corresponding non-heat integrated cases for all the configurations investigated. Heat integration showed that the heating and cooling energy demands could be reduced to a great extent in stand-alone as well as combined 1st and 2nd generation bioethanol plants. The cost for heating and cooling of the process can be decreased with heat integration. The main cost for providing the processes with heat can be attributed to the cost of hot utilities.

Impacts of retrofitting analysis on first generation ethanol production: process design and techno-economics.

More than half of the bioethanol plants in operation today use corn or grains as raw materials. The downstream processing of mash after fermentation to produce ethanol and distiller grains is an energy-demanding process, which needs retrofitting for optimization. In addition, the fluctuation in the ethanol and grain prices affects the overall profitability of the plant. For this purpose, a process simulation was performed in Aspen Plus(®) based on an existing industrial plant located in Sweden. The simulations were compared using different scenarios including different concentrations of ethanol, using the stillage for biogas production to produce steam instead of distiller grains as a by-product, and altering the purity of the ethanol produced. Using stillage for biogas production, as well as utilizing the steam, reduced the overall energy consumption by 40% compared to the plant in operation. The fluctuations in grain prices had a high impact on the net present value (NPV), where grain prices greater than 349 USD/ton reached a zero NPV. After 20 years, the plant in operation producing 41,600 tons ethanol/year can generate a profit of 78 million USD. Compared to the base case, the less purified ethanol resulted in a lower NPV of 30 million USD.

Resource Efficiency Studies using a New Operator Training Simulator for a Bioethanol Plant

Biofuel production plants are expected to significantly contribute to an environmentally sustainable future. However, a prerequisite for this goal is the resource conserving and energy efficient operation of these plants. Complex process dynamics are supposed to have an important influence on resource and energy efficiency of biofuel plants. This leads to strong demands on plant operators and automation systems. In this contribution a newly developed operator training simulator (OTS) is used to demonstrate the influence of process control and automation strategies on the sustainable operation of a bioethanol plant. The OTS presented here is based on mechanistic and dynamic process models describing the unit operations and some additional equipment such as valves, pumps, etc.. The models were verified using pilot plant data and have been implemented in the control system and simulation software WinErs. Automation sequences for the full plant have been developed using GRAFCET. Simulation experiments with the operator training simulator of the bioethanol production plant clearly indicate the strong influence of operational strategies and conditions on the resource efficiency and bioethanol yield of the process. The operational strategies and conditions for the bioethanol fermentation unit, the cross flow unit as well as the rectification unit and the overall process may lead to a variation of the energy demands for ethanol production of 48 %.

Reducing the cost, environmental impact and energy consumption of biofuel processes through heat integration

This study proposes a process design methodology based on the combined use of process simulation in Super Pro Designer with economic, environmental and energetic balances implemented in Matlab and heat integration using Aspen Energy Analyzer. We model a 2.4MMgal/year alkali-catalyzed biodiesel process using vegetable oil and a 40MMgal/year dry-grind corn based bioethanol production plant. Then, we analyse the cost, the environmental impact, and the energy required to produce one gallon of the desired biofuel. Finally, we determine the optimal heat integration strategy of the plant in order to reduce the cost, environmental impact and energy consumption associated to the biofuel production. In the case of biodiesel the cost is reduced from 2.27$/gal to 2.19$/gal, the environmental impact from 4.52kgCO2eq/gallon to 4.26kgCO2eq/gallon and the energy from 8274BTU/gal to 8410BTU/gal. Reductions are also obtained in the bioethanol plant in which the cost is reduced from 1.79$/gal to 1.75$/gal, the environmental impact from 4.97kgCO2eq/gal to 4.77kgCO2eq/gal and the energy from 24,681BTU/gal to 23,168BTU/gal.