Gasification Route Research Articles

Comparative techno-economic assessment of methanol production via directly and indirectly electrified biomass gasification routes

The sustainable production of chemicals and fuels is a major challenge in order to reduce greenhouse gas emissions and reduce the usage of fossil resources. Biomass gasification with a subsequent conversion of the syngas to methanol is an established route. The direct (electrical resistance heating) or indirect (H2 production via water electrolysis and addition to process) electrification of this route with utilization of renewably produced electricity can improve the effective utilization of biomass which is a scarce resource. Starting with a base case (Biomass-to-MeOH), 10 scenarios with different types and points of electrification are modelled in Aspen Plus to generate mass and energy balances. Based on the generated data, the processes are compared in terms of efficiency, economics, and CO2 emissions.The electrification ratios range from 0.12 for the Biomass-to-MeOH process to 1.31. Electrification can increase the carbon efficiency from 43 % for the Biomass-to-MeOH process to up to 95 % while the energy efficiency ranges from 54.6 % to 60.3 % with 54.7 % for the Biomass-to-MeOH process. The levelized cost of methanol ranges from 642 to 795 €/t. Lowest LCOM are reached for direct electrification of the gasifier or reformer. A flexible operation of the electrified process shows a higher sensitivity on the levelized cost for scenarios with high degree of electrification. The marginal emission factor for the used electricity ranges from 1761 to 352 g CO2/kWh to reach equal emissions than the fossil equivalent. Sustainable methanol can be produced with the electrified processes. Especially direct electrification can improve the efficiency and lower cost in comparison to indirect electrification. A combination of both types of electrification is advised if a high product yield and carbon efficiency are desired.

Multi-factor optimization of bio-methanol production through gasification process via statistical methodology coupled with genetic algorithm

This work innovatively explores the bio-methanol production process, conducts comprehensive analyses, develops statistical models, and optimizes operational conditions, contributing valuable insights to the field of sustainable energy production from biomass. Accordingly, bio-methanol production from biomass through gasification route was investigated and simulated using Aspen Plus software. The effects of operational parameters on energy duty of gasification reactor and the methanol production rate in syngas to methanol reactor were investigated. The parameters affecting the process performance including temperature, pressure, and steam/feed ratio were examined using the response surface methodology (RSM) by central composite design (CCD) technique. Analysis of variance (ANOVA) was performed, and two quadratic models were derived. The predicted R2 values of these models for methanol mass flowrate and energy duty were 0.9394 and 0.9363, respectively. The optimal operational conditions were identified using genetic algorithm (GA). The optimum values of temperature, pressure, and steam/feed ratio in gasification reactor were 900 °C, 4 bar, and 0.675, respectively. This condition leads to methanol mass flowrate and energy duty of 4.254 kg/s and 40736.355 kw, respectively. In addition, sensitivity analysis was performed on syngas to methanol reactor performance.

Comparative Exergy and Environmental Assessment of the Residual Biomass Gasification Routes for Hydrogen and Ammonia Production.

The need to reduce the dependency of chemicals on fossil fuels has recently motivated the adoption of renewable energies in those sectors. In addition, due to a growing population, the treatment and disposition of residual biomass from agricultural processes, such as sugar cane and orange bagasse, or even from human waste, such as sewage sludge, will be a challenge for the next generation. These residual biomasses can be an attractive alternative for the production of environmentally friendly fuels and make the economy more circular and efficient. However, these raw materials have been hitherto widely used as fuel for boilers or disposed of in sanitary landfills, losing their capacity to generate other by-products in addition to contributing to the emissions of gases that promote global warming. For this reason, this work analyzes and optimizes the biomass-based routes of biochemical production (namely, hydrogen and ammonia) using the gasification of residual biomasses. Moreover, the capture of biogenic CO2 aims to reduce the environmental burden, leading to negative emissions in the overall energy system. In this context, the chemical plants were designed, modeled, and simulated using Aspen plus™ software. The energy integration and optimization were performed using the OSMOSE Lua Platform. The exergy destruction, exergy efficiency, and general balance of the CO2 emissions were evaluated. As a result, the irreversibility generated by the gasification unit has a relevant influence on the exergy efficiency of the entire plant. On the other hand, an overall negative emission balance of -5.95 kgCO2/kgH2 in the hydrogen production route and -1.615 kgCO2/kgNH3 in the ammonia production route can be achieved, thus removing from the atmosphere 0.901 tCO2/tbiomass and 1.096 tCO2/tbiomass, respectively.

Assessment of electrified ethylene production via biomass gasification and electrochemical CO reduction

The chemical industry needs new methods for sourcing carbon-containing feedstocks from renewable sources to decrease CO2 emissions and reduce reliance on fossil fuels. Ethylene, a crucial base chemical used for making polymers and ethylene oxide, is primarily produced through steam cracking of fossil feedstocks. However, an evolving technology is the electrochemical reduction of CO2 or CO to produce ethylene. The study assesses the environmental, economic and energetic performance of a new biomass-based process that produces ethylene based on the electrochemical reduction of CO. The results are based on mass and energy balances from process simulation. The CO is produced by either gasification of biomass or combustion of biomass with CO2 capture and CO2 electrolysis. Besides ethylene, the process produces acetic acid, ethanol, oxygen and hydrogen as by-products which are purified and sold. The annual output varies between 36 and 68 kt ethylene with a biomass input of 157 kt. The levelized cost of ethylene ranges from 3,920 to 7,163 €/t with the gasification routes being the most cost-effective. The ethylene price is heavily dependent on electricity price, current density, operating voltage, and by-product prices. The carbon efficiency of the gasification-based routes is lower (64%) than the combustion-based routes (85%–86%). However, the energy efficiency is higher for the gasification-based routes (42%) compared to the combustion-based routes (28%). Conversion of ethanol to ethylene increases the ethylene yield with minimal impacts on the ethylene price. In terms of CO2 emissions, the gasification-based routes show lower emissions. Scenarios using wind power show a significant emission reduction potential compared to fossil products.

Gasification integrated with steam co-reforming of agricultural waste biomass over its derived CO2/O2/steam-mediated porous biochar for boosting H2-rich syngas production

This study proposed a novel concept of producing H2-rich syngas and eliminating tar formation via biomass gasification integrated with inline steam co-reforming (BGSCR). Initially, direct gasification of wheat straw in diverse gasifying agents was conducted to produce CO2/O2/steam-mediated porous biochar materials (PBMs), which were innovatively used as catalytic reforming agents and co-reactants for BGSCR process. With the aid of gasifying agents, the surface structures of PBMs were apparently fabricated with more micropores. Particularly, C[steam] achieved the highest surface area (502 m2/g) and total pore volume (0.297 cm3/g). Further, catalytic reforming temperature and type of PBMs were examined in relation to gas formation behaviors during BGSCR process. The maximum gas yield (58.53 mmol/g), H2 yield (28.29 mmol/g), and syngas yield (45.96 mmol/g) were achieved in the presence of C[10%O2]. Simply put, this study presents a promising gasification route to directly integrate H2-enriched syngas generation and in-situ tar abatement with biochar reutilization.

Systematic comparison of natural and engineering methods of capturing CO2 from the air and its utilization

The rising CO2 concentration in the atmosphere calls for not only the decarbonization of our lifestyle but also the removal of CO2 to meet the sustainable development goals. In this work, a comprehensive techno-economic comparison based on systematic process design of CO2 capture technologies from the air is performed. Biomass and direct air capture (DAC) are considered as well as the further utilization of CO2. A common final product, methanol, is selected for easier comparison. Six different biomasses are considered, including energy crops, forests, and agriculture. Four biomass gasification routes are evaluated to produce methanol. Two direct air capture technologies are followed by CO2 hydrogenation. Hydrogen is produced by splitting water using solar and/or wind energy. The current status of the technologies gives biomass an advantage as carbon capture technology with production and investment costs ten times lower, due to the high price of the renewable energy collection for the operation of the fans. However, the area required for growing biomass, except in the case of residues, and the total amount of water consumed, favors the engineered alternative, DAC. The investment and production costs depend on the location and the technology development.

Inhibiting the Laydown of Polymeric Carbon and Simultaneously Promoting Its Facile Burn-Off during the Industrial-Scale Production of Hydrogen with Nickel-Based Catalysts: Insights from Ab Initio Calculations.

This paper presents a computational study of the mechanistic models for the laydown of carbon species on nickel surface facets and the burn-off models for their gasification mechanism in methane steam reforming based on density functional theory. Insights into catalyst design strategies for achieving the simultaneous inhibition of the laydown of polymeric carbon and the promotion of its burn-off are obtained by investigating the influence of single atom dopants on nickel surfaces. The effects of single atom dopants on adsorption energies are determined at both low and high carbon coverages on nickel and used to introduce appropriate thermodynamic descriptors of the associated surface reactions. It is found that the critical size of the nucleating polymeric carbon adatom contains three atoms, i.e., C3. The results show that the burn-off reaction of a polymeric carbon species is thermodynamically limited and hard to promote when the deposited carbon cluster grows beyond a critical size, C4. The introduction of single atom dopants into nickel surfaces is found to modify the structural stability and adsorption energies of carbon adatom species, as well as the free energy profiles of surface reactions for the burn-off reactions when CH4, H2O, H2, and CO species react to form hydrogen. The results reveal that materials development strategies that modify the sub-surface of the catalyst with potassium, strontium, or barium will inhibit carbon nucleation and promote burn-off, while surface doping with niobium, tungsten, or molybdenum will promote the laydown of polymeric carbon. This study provides underpinning insights into the reaction mechanisms for the coking of a nickel catalyst and the gasification routes that are possible for the recovery of a nickel catalyst during the steam reforming of methane for large-scale production of hydrogen.

High-Ash Low-Rank Coal Gasification: Process Modeling and Multiobjective Optimization

The diversification of coal for its sustainable utilization in producing liquid transportation fuel is inevitable in countries with huge coal reserves. Gasification has been contemplated as one of the most promising thermochemical routes to convert coal into high-quality syngas, which can be utilized to produce liquid hydrocarbons through catalytic Fischer–Tropsch (F-T) synthesis. Liquid transportation fuel production through coal gasification could help deal with environmental challenges and renewable energy development. The present study aims to develop an equilibrium model of a downdraft fixed-bed gasifier using Aspen Plus simulator to predict the syngas compositions obtained from the gasification of high-ash low-rank coal at different operating conditions. Air is used as a gasifying agent in the present study. The model validation is done using published experimental and simulation results from previous investigations. The sensitivity analysis is done to observe the influence of the major operating parameters, such as equivalence ratio (ER), gasification temperature, and moisture content (MC), on the performance of the CL-RMC concerning syngas generation. The gasification performance of CL-RMC is analyzed by defining various performance parameters such as syngas composition, hydrogen-to-carbon monoxide (H2/CO), molar ratio, syngas yield (YSyngas), the lower heating value of syngas (LHVSyngas), cold gas efficiency (CGE), and carbon conversion efficiency (CCE). The combined effects of the major operating parameters are studied through the response surface methodology (RSM) using the design of experiments. The optimized condition of the major operational parameters is determined for a target value of a H2/CO molar ratio of 1 and the maximum CGE and CCE using the multiobjective optimization approach. The high-degree accurate regression model equations were generated for the H2/CO molar ratio, CGE, and CCE using the variance analysis (ANOVA) tool. The optimal conditions of the major operating parameters, i.e., ER, gasification temperature, MC for the H2/CO molar ratio of 1, and the maximum CGE and CCE, are found to be 0.5, 655 °C, and 16.36 wt %, respectively. The corresponding optimal values of CGE and CCE are obtained as 22 and 16.36%, respectively, with a cumulative composite desirability value of 0.7348. The findings of the present investigation can be decisive for future developmental projects in countries concerning the utilization of high-ash low-rank coal in liquid fuel production through the gasification route.

Economic Feasibility of Dimethyl Ether from Oil Palm Empty Fruit Bunch as a Substitute for LPG in Indonesia

Oil palm empty fruit bunch (OPEFB) can be utilized as a feedstock for dimethyl ether (DME) production through the gasification route. DME has similar characteristics to liquefied petroleum gas (LPG). Therefore, it can be used as a substitute for LPG. Some research has been conducted on DME as a substitute for LPG from various aspects. However, little research was focused on the economic study of OPEFB-based DME as an LPG substitute and its contribution towards saving the LPG import budget. This study aims to find DME plant feasibility, and to assess its contribution to the LPG import budget reduction, especially in the Kalimantan region. The DME price at the depot is calculated based on the ex-factory price of DME, transportation cost, and depot fee. The OPEFB-based DME plant capacity is 994 t day-1 OPEFB, which produces 192 t day-1 DME. From an economic perspective, the net present value (NPV), internal rate of return (IRR), and payback period (PP) are USD 93.1 million, 17%, and 10 years, respectively, based on 30 years of plant life and USD 185.4 million investment. Only 57% of the DME-LPG mix can be distributed to fulfill Kalimantan region demand per year, while the savings on the import budget is USD 5.81 million y-1. The OPEFB-based DME plant capacity and capital expenditure (CAPEX) are the most sensitive to perturbance, whereas OPEFB feed price is the least sensitive.

Concept design, technical performance, and GHG emissions analysis of petroleum coke direct chemical looping hydrogen highly integrated with gasification for methanol production process

Petroleum coke gasification for methanol production process has excellent application prospects for the clean utilization of high‑sulfur coke while limiting pollutant emissions from coke combustion. However, the process still suffers from high-energy use and a large CO2 generation caused by composition adjustment. This study proposes a novel petroleum coke chemical looping hydrogen-assisted gasification process for methanol production. Mass-energy coupling is realized by replacing the water gas shift unit with the chemical looping hydrogen unit, and the high temperature gasified gas heats the fuel reactor and in turn the feedstock. Two chemical looping hydrogen scenarios with an operating pressure of 3.0 and 0.1 MPa are considered. The methanol exergy can be increased from 484 to 1030 and 1028 MW by doubling the petroleum coke consumption through the chemical looping integration. The exergy efficiency of the new process is correspondingly increased from 51.6 to 57.1 and 55.2 % with 63.02 and 63.71 % reductions in direct CO2 emissions, as compared to the only gasification route. The calculated life cycle energy consumption and greenhouse gases emissions of the new processes are 40.02/43.84 GJ/t and 693/1055 kg CO2 eq/t, 15.14/7.05 % and 49.09/22.45 % lower than that of the benchmark process. The integration of high-pressure chemical looping technology can introduce significant technical and environmental benefits for methanol production from the petroleum coke.

From municipal solid waste (MSW) to hydrogen: Performance optimization of a fixed bed gasifier using Box-Benkhen method

Management of solid waste, generated from the municipal/urban sectors has always been troublesome to the governing authorities, especially of the developing and wide populated nations. Traditionally, the municipal solid waste (MSW) is dumped in low land areas for land-filling purpose or burnt in improper way which causes environmental pollution in short term as well as in long term basis. It is experienced that production from green fuel like hydrogen (H2) from MSW through gasification route will not only mitigate the MSW management issues but also reduce the dependency on fossil fuels. In this study, model development of a fixed bed gasifier considering steam gasification method is carried out for production of H2 rich syngas from MSW. Additionally, optimization study by employing Box-Benkhen method of Response Surface Methodology (RSM) is performed to find out the best values output parameters viz., H2 yield, lower heating value (LHV) of syngas and cold gas efficiency (CGE). It is noted that modelled gas data matches well with the experimental gas data. It is also imparted from the optimization analysis that the model offers H2 yield of about 64% with LHV of the syngas of about 11 MJ/kg and cold gas efficiency of about 92%, respectively. Desirability of the model predicted results are computed to be ‘0.79’ which signifies that results are substantially accurate and well acceptable.

Techno-economic and environmental analysis of methanol and dimethyl ether production from syngas in a kraft pulp process

The conventional configuration of a pulp mill, in which black liquor is concentrated and burnt, is compared to the upgrading gasification routes for methanol (MeOH) or dimethyl ether (DME) co-production. To this end, various exergy-based and environmental impact indicators are assessed in the light of different utility supply scenarios. The combined exergy and energy integration analysis are used to identify potential improvements related to the decarbonization and mitigation of the process irreversibility. As a result, the exergy efficiencies of the conventional scenario and the integrated plants average 40% and 45%, respectively, whereas the overall CO2 emission balances vary from 1.97 to -0.07 tCO2/tPulp, respectively. Additionally, an incremental economic analysis that envisages future carbon taxation scenarios suggests that only MeOH or DME co-production routes with partial electricity import may economically outperform the conventional kraft pulp mill for moderate carbon taxations. These results highlight the relevance of the electricity import from the Brazilian mix for pushing upwards the share of renewable energy resources in the production of traditionally fossil-based fuels and chemicals.

Syngas generation for methanol synthesis: oxy-steam gasification route using agro-residue as fuel

Syngas generation for methanol synthesis: oxy-steam gasification route using agro-residue as fuel

Techno‐economic assessment of bio‐refinery model based on co‐pyrolysis of cotton boll crop‐residue and plastic waste

AbstractThis study evaluated the techno‐economic aspects of empty cotton boll valorization to liquid fuel (moisture free bio‐oil), potash fertilizer, and activated carbon. Three different plant capacities, in terms of feedstock handling capacities were considered: 50, 100, and 200 t day−1. For each plant capacity, three plant variants were considered: only fuel, fuel + potash fertilizer, and fuel + potash fertilizer + activated carbon. The net present value ranged from 7.73 M$ for a 50 t day−1 plant to 47.38 M$ for a 200 t day−1 plant, producing liquid fuel along with fertilizer and activated carbon. The overall profitability of the plant was improved by higher plant capacity. For a 200 t day−1 plant, equipment purchase cost related to the synthesis of fuel, potash fertilizer and activated carbon contributed 32.87, 25.77, and 41.36%, respectively to the total purchase equipment cost of the entire plant. Among the three products, activated carbon contributed 81.03% to the total revenue generated by the entire plant. The sensitivity of plant economics towards feedstock price, selling price of activated carbon, potassium hydroxide recovery, annual interest rates, and total capital investment was examined. The economic competitiveness for this kind of thermo‐chemical conversion was assessed in comparison with the solar gasification route. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Aspects of chemical recycling of complex plastic waste via the gasification route

Oxygen blown high-temperature gasification constitutes an opportunity for chemical recycling of plastic wastes. This article summarizes the results from comparative tests of combustion and gasification of two complex plastic wastes: a plastic reject (PR) from processing recycled paper and an automotive shredder residue (ASR). Calculated gasification efficiencies corresponded to about 80% and 60%, respectively. Gasification resulted in lower yields of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) compared to direct combustion. A two-stage process, including gasification followed by syngas combustion, reduced the emissions of HCl and PCDD/F in the flue gas to <1.4% and <0.2%, respectively, compared to the levels from direct combustion of the PR feedstock. Most of the PCDD/F (>99%) was captured along with particulate matter (soot) during gasification. The contribution to the toxic concentration of PCDD/F was mainly from the PCDF congeners. Fly ash particulate matter from ASR combustion contained a significant proportion of zinc, which thus constitutes a great potential for use in zinc recycling.

Thermodynamic comparison of pyrolysis and gasification of waste tyres

Waste tyres are a particularly problematic pollutant; persistent, highly toxic, flammable, and difficult to process or store. However, waste tyres need not be viewed solely as a waste material, as they also offer promising properties as an energy material. Waste tyres have a higher energy density than coal, as well as lower ash content and favourable quantities of carbon and hydrogen. Extensive experimental research has demonstrated that thermochemical valorisation pathways including pyrolysis and gasification are viable for producing valuable chemical products from waste tyre. Despite this, there is as yet no established technology for waste tyre conversion. In this paper, fundamental thermodynamic and economic analysis is used to evaluate a range of process pathways to determine their economic favourability and environmental impact. The process performance targets derived in this way can serve as a basis for preliminary process design and provide estimates for the commodity value of waste tyre, informing long-range planning in both corporate and legislative settings. A range of pyrolysis and gasification pathways have been evaluated in terms of the fundamental thermodynamic metrics of carbon efficiency, atom economy, e-factor and chemical potential efficiency, and also their market-related revenue potential. It was found that pyrolysis pathways perform better in terms of thermodynamic efficiency and carbon footprint than gasification processes, which lose about 45% of the carbon feed to carbon dioxide. However, the gasification routes offer higher potential revenue, yielding as much as $625 per ton of waste tyre as compared to $205 from the pyrolysis route.

Optimised production of tailored syngas from municipal solid waste (MSW) by sorption-enhanced gasification

Sorption-enhanced gasification (SEG) is a promising indirect gasification route for the production of synthetic fuels since it allows the H2, CO and CO2 content of the resulting syngas to be adjusted. This SEG process has been successfully demonstrated at pilot scale for lignocellulosic biomass and other agricultural and forest waste products, mainly focusing on H2-rich gas production. Within this work, the potential application of the SEG process to a material derived from municipal solid waste (MSW) as feedstock is experimentally demonstrated in a 30 kWth bubbling fluidised-bed (BFB) gasifier. The influence of the sorbent-to-biomass ratio, steam excess and gasification temperature has been carefully analysed in order to understand their effect on SEG performance. Moreover, main conditions able to affect the resulting syngas composition, specifically in terms of H2, CO and CO2 content, have been indicated. Gasification temperature turned out to be the variable that most influenced syngas composition due to the limiting mechanisms associated with the carbonation of the CaO used as bed material. This operating variable also determined biomass conversion, together with solids residence time in the gasifier, resulting in a wide variation of fixed carbon conversion under the studied conditions. Finally, tar yield and composition were evaluated as a function of temperature and the sorbent-to-biomass ratio used, resulting in tar contents as low as 7 g/Nm3 (dry gas), consisting mainly of 1-ring aromatic compounds.

How to maximise the value of residual biomass resources: The case of straw in Denmark

The long-lived dependence on fossil fuels has led to a slow pace in the transition to renewable energy sources in the heavy-duty sectors of the energy system. While bioenergy might represent a possible alternative, biomass is a limited resource, whose use is restricted by potential technical, environmental and social impliations. Because residual biomass inherently minimises these negative impacts, when its sustainable use is ensured, it could lend itself to multiple options, including production of back-up power, heating and alternative transport fuels. This study investigates different pathways for the optimal use of the most abundant residual biomass in Denmark, i.e. straw, from a technical, economic and environmental perspective. We harness the strengths of two bottom-up model typologies by means of soft-linkage to reveal insights from both perspectives: the multi-sectoral model, TIMES-DK, provides a system assessment of the whole energy sector, while the geographically detailed optimization model, Balmorel-OptiFlow, supports the analysis of biorefinery plant size, location and area-specific recovery of excess heat. Modelling results of carbon- and resource-constrained energy scenarios reveal the increased value of straw in a future decarbonised energy system and the attractiveness of the gasification route with Fischer-Tropsch synthesis for the production of biofuels to supply the heavy segments of the transport sector. Moreover, relying on current domestic biomass resources would not attain the energy self-sufficiency targets in a carbon-constrained case.

Electricity Generation Potential Through Solar-Rice Husk Hybrid Power Plant in Nepal and Its Major Paddy Producing Districts

Nepal is an agricultural based country having huge potential of rice husk. Out of total electrical energy consumption in Nepal, 22%, 34.76% and 36.58% were imported from India in the years 2016, 2017 and 2018 respectively. Such import can be minimized by generating electricity from solar-rice husk hybrid system. Solar plants have drawbacks of intermittency in day/night cycle and reduced irradiation in winter and cloudy days. Biomass plants have problem associated with continuous supply of seasonal fuel. Those problems can be solved using hybrid system by maximizing the energy potential of these resources, increasing process efficiency, providing greater security of supply and reducing overall cost. The objective of this paper is to estimate electricity generation potential through solar- rice husk hybrid power plant in Nepal and its major paddy producing districts through existing data and forecasting the same for future potential. From existing data, the rice husk growth rate in Nepal was found to be 2.92% and on the basis of that growth rate, future potentials were forecasted. The 20 major paddy producing districts were taken into consideration as 71.15% of total paddy production of Nepal was found to be shared by those districts. The quantity of rice husk was found assuming 20% of paddy converted into rice husk in the mills. The rice husk consumption for cattle feeding was assumed 10% of total rice husk. The electric power from rice husk was calculated assuming 1.3 kg consumption of rice husk for per kWh generation of electricity through steam route and 1.86 kg of rice husk consumption for per kWh electricity generation through gasification route. The average increase rate of land for paddy production and the average increase rate of rice husk production were found to be 0.39% and 2.92% respectively. The electrical energy potentials of Nepal for the years 2015 and 2030 with solar-rice husk hybrid power plant through steam route were found as 100.67 MW and 155.02 MW respectively and through gasification route 70.36 MW and 108.35 MW respectively. The electrical potential for Jhapa district was found the highest values of 7.10 MW and 10.94 MW through steam route and 4.96 MW and 7.64 MW through gasification route for the years 2015 and 2030 respectively. Thus, through solar-rice husk hybrid power plant system, large amount of electricity can be generated locally in Nepal, which in turn can reduce energy import and enhance the better life of the people.

Utilising biomass for renewable energy production: optimal profitability evaluation from different processing routes

Utilisation of biomass such as wheat straws for the renewable energy production is an attractive option for agricultural diversifications and sustainability targets. One of the possible energy products from wheat straws is bioethanol. Since bioethanol could be produced from different ways, the issue arises on how to select the most economical one. In this paper, four processing routes to convert the wheat straws into bioethanol were screened; i) pelletisation and gasification, ii) torrefied pelletisation and gasification, iii) dilute acidic hydrolysis and fermentation, and iv) concentrated acidic hydrolysis and fermentation. The objective was to develop optimisation models to evaluate these routes as find the one that would produce the highest annual profitability by considering the whole supply chain. A mathematical model for optimisation, classified as linear programming, was then formulated to consider the biomass blending requirements and profitability equation. Optimisation results showed that the conversion of wheat straws into bioethanol could be potentially exploited via the torrefied pelletisation and gasification route as they gave the highest profitability of $489,330 per year, in the view of the whole supply chain. This was followed by concentrate acidic hydrolysis and fermentation route of $ 472,500 per year, dilute acidic hydrolysis and fermentation route of $402,750 per year, and pelletisation with gasification route of $388,530 per year. The developed optimisation models have been successfully screened and selected the best processing route to produce bioethanol from the evaluated profitability. Since this was at the conceptual stage, further refinement of the model parameters will be needed to provide a more practical basis for comparison.