Potential biomass supply for agro-pellet production from agricultural crop residue in Nepal

Nepal, a country rich in biomass, still does not have any commercial pellet production plants and is wasting large amounts of agricultural crop residue. The current study showed that about 5.61 million tonnes (Mt) of biomass in the form of pellets are potentially available from agricultural crop residues. The brick and cement industries could use these agro-pellets. Co-firing of pellets in such industries could play an important role in reducing the import volume of coal and minimize the related environmental loadings.     

Using a decision support system to optimize production of agricultural crop residue Biofeedstock

For several years the Idaho National Laboratory (INL) has been developing a Decision Support System for Agriculture (DSS4Ag) which determines the economically optimum recipe of various fertilizers to apply at each site in a field to produce a crop, based on the existing soil fertility at each site, as well as historic production information and current prices of fertilizers and the forecast market price of the crop at harvest. In support of the growing interest in agricultural crop residues as a bioenergy feedstock, we have extended the capability of the DSS4Ag to develop a variable-rate fertilizer recipe for the simultaneous economically optimum production of both grain and straw. In this paper we report the results of 2 yr of field research testing and enhancing the DSS4Ag's ability to economically optimize the fertilization for the simultaneous production of both grain and its straw, where the straw is an agricultural crop residue that can be used as a biofeedstock. For both years, the DSS4Ag reduced the cost and amount of fertilizers used and increased grower profit, while reducing the biomass produced. The DSS4Ag results show that when a biorefinery infrastructure is in place and growers have a strong market for their straw it is not economically advantageous to increase fertilization in order to try to produce more straw. This suggests that other solutions, such as single-pass selective harvest, must be implemented to meet national goals for the amount of biomass that will be available for collection and use for bioenergy.     

Methane production from lignocellulosic agricultural crop wastes: A review in context to second generation of biofuel production

The aim of this paper is to present a comprehensive review on renewable methane fuel production through the biological route of biomethanation process from major lignocellulosic agricultural crop waste biomass (maize, wheat, rice and sugarcane). Global annual approximate production of major agriculture based lignocellulosic biomass has been explored. Fundamental requirements of biomethanation process have been discussed in details for optimum production of methane. The essential properties of biomass (proximate, ultimate and compositional) conscientious for quality of derived fuel have also been presented along with the pretreatment requirements for lignocellulosic biomass. Methane generation potential of the major lignocellulosic agricultural crop biomass has been explored and presented. Furthermore, the methane production potential and its energetic analysis have also been compared with the bio-ethanol productions. The overall parametric analysis involved in anaerobic digestion and alcoholic fermentation explore that methane generation from lignocellulosic agricultural crop waste biomass is more economical and environmentally beneficial way of biomass utilization in a sustainable way of energy production.     

Biomass supply from alternative cellulosic crops and crop residues: A spatially explicit bioeconomic modeling approach

This paper introduces a spatially-explicit bioeconomic model for the study of potential cellulosic biomass supply. For biomass crops to begin to replace current crops, farmers must earn more from them than from current crops. Using weather, topographic and soil data, the terrestrial ecosystem model, EPIC, dynamically simulates multiple cropping systems that vary by crop rotation, tillage, fertilization and residue removal rate. EPIC generates predicted crop yield and environmental outcomes over multiple watersheds. These EPIC results are used to parameterize a regional profit-maximization mathematical programming model that identifies profitable cropping system choices. The bioeconomic model is calibrated to 2007-09 crop production in a 9-county region of southwest Michigan. A simulation of biomass supply in response to rising biomass prices shows that cellulosic residues from corn stover and wheat straw begin to be supplied at minimum delivered biomass:corn grain price ratios of 0.15 and 0.18, respectively. At the mean corn price of $162.6/Mg ($4.13 per bushel) at commercial moisture content during 2007-2009, these ratios correspond to stover and straw prices of $24 and $29 per dry Mg. Perennial bioenergy crops begin to be supplied at price levels 2-3 times higher. Average biomass transport costs to the biorefinery plant range from $6 to $20/Mg compared to conventional crop production practices in the area, biomass supply from annual crop residues increased greenhouse gas emissions and reduced water quality through increased nutrient loss. By contrast, perennial cellulosic biomass crop production reduced greenhouse gas emissions and improved water quality.     

Potential of fungi as category I Consolidated BioProcessing organisms for cellulosic ethanol production

Consolidated BioProcessing (CBP) can provide an important contribution to reducing ethanol production costs and moving from cellulosic feedstock to fuel ethanol tanks. Several efforts have so far been focused mainly on CBP category II engineering an ethanologen yeast or bacterium to be cellulolytic, but the limited ability of the category II CBP system for producing enzymes for lignocellulose degradation remains a challenge. As an alternative, category I CBP, aimed at engineering a cellulase producer to be ethanologenic, could be pursued, but it is still in its infancy. Some cellulolytic thermophilic bacteria have been described as potential candidates for category I CBP. However, only fungi naturally produce the needed titers of cellulases required for the complete saccharification of pretreated lignocellulose. In this review, potential of cellulolytic fungi as candidates for category I CBP is discussed.     

植物纤维原料发酵生产燃料乙醇研究进展

综述了以植物纤维素为原料生产燃料乙醇的4种不同工艺,包括:分段水解与发酵(SHF)、同步糖化和发酵(SSF)、同步糖化共发酵(SSCF)和联合生物加工工艺(CBP),并比较了它们的成熟程度以及优缺点。简述了纤维乙醇在国内外的发展现状,同时提出了我国今后一段时间内发展纤维乙醇的策略。     

新型纤维素乙醇原料保障体系及经济分析

为解决北方某纤维素乙醇生产企业的原料收储问题,文中基于该地区特点提出以农业剩余物固体成型为核心的新型原料收储路线,并初步设计整个原料保障体系运作方式;同时根据建立的收储经济评价模型,对新旧原料收储路线下纤维素乙醇原料的收储运及生产过程进行经济分析,探讨了燃料乙醇规模扩张时的盈利情况以及影响因素。分析结果表明,新型收储路线大幅度简化了原料收储方式,具有运输半径合理、存储条件要求低、潜在效益较佳等优势,适宜于保障规模化燃料乙醇的生产。     

Estimating national costs, benefits, and potential for cellulosic ethanol production from forest thinnings

Since 2004, wildfires have been responsible for the destruction of 3.5 million hectares of forestland per year. Fuel reduction activities such as prescribed fires, cutting and burning in situ, and biomass removal (thinning) have been shown to reduce wildfire severity, but with mounting costs of fighting wildfires and a tightening budget, public agencies such as the USDA Forest Service may find it difficult to continue funding these preventative treatments. By using thinned biomass as a cellulosic ethanol feedstock, these agencies may be able to generate funds for these treatments. Here, we estimate costs of producing cellulosic ethanol from forest thinnings based on forest thinning supply curves. Nationally, 27 to 34 million Mg of biomass could be removed from overcrowded forests per year at collection costs of $55 to $110 per dry Mg. Given a mature cellulosic ethanol industry, ethanol produced from these thinnings could generate revenue at gasoline prices of $0.5 to $0.8 per liter. By using thinned biomass as an ethanol feedstock, it may be possible to generate significant funds for socially beneficial thinning treatments.     

Integrated energy,environmental and financial analysis of ethanol production from cellulosic switchgrass

Ethanol production from cellulosic sources such as switchgrass (Panicum virgatum L.) requires the use of natural resources, fossil fuels, electricity, and human-derived goods and services. We used emergy accounting to integrate the ultimate amount of environmental, fossil fuel, and human-derived energy required to produce ethanol from switchgrass. Emergy is the total amount of energy of one form required directly and indirectly to make another form of energy. Forty-four percent of required emergy came from the environment either directly or embodied in purchased goods, 30% came from fossil fuels either directly or embodied in purchased goods, and 25% came from human-derived services indirectly. Ethanol production per petroleum use (emergy/emergy) was 4.0-to-1 under our Baseline Scenario, but dropped to 0.5-to-1 under a scenario that assumed higher input prices, lower conversion efficiencies and less waste recycling. At least 75% of total emergy was from non-renewable sources. Energy ‘hidden’ in indirect paths such as goods and services was 65% of the total. Cellulosic-ethanol is not a primary fuel source that substitutes for petroleum because its production relies heavily on non-renewable energy and purchased inputs. It is a means for converting natural resources to liquid fuel.     

Pretreatment and hydrolysis of cellulosic agricultural wastes with a cellulase-producing Streptomyces for bioethanol production

Production of reducing sugar by hydrolysis of corncob material with Streptomyces sp. cellulase and ethanol fermentation of cellulosic hydrolysate was investigated. Cultures of Streptomyces sp. T3-1 improved reducing sugar yields with the production of CMCase, Avicelase and ??-glucosidase activity of 3.8, 3.9 and 3.8 IU/ml, respectively. CMCase, Avicelase, and ??-glucosidase produced by the Streptomyces sp. T3-1 favored the conversion of cellulose to glucose. It was recognized that the synergistic interaction of endoglucanase, exoglucanase and ??-glucosidase resulted in efficient hydrolysis of cellulosic substrate. After 5 d of incubation, the overall reducing sugar yield reached 53.1 g/100 g dried substrate. Further fermentation of cellulosic hydrolysate containing 40.5 g/l glucose was performed using Saccharomyces cerevisiae BCRC 21812, 14.6 g/l biomass and 24.6 g/l ethanol was obtained within 3 d. The results have significant implications and future applications regarding to production of fuel ethanol from agricultural cellulosic waste.     

Microwave-assisted ethanol decomposition over pyrolysis residue of sewage sludge for hydrogen-rich gas production

Microwave-assisted ethanol decomposition over pyrolysis residue of sewage sludge (PRSS) was investigated in a multi-mode microwave (MW) oven, and was compared with ethanol decomposition over a commercial activated carbon (AC). The results indicated that PRSS showed higher MW heating performance than AC. Under the same microwave power (MP), the temperature of catalyst bed, hydrogen produc0oij9tion and ethanol conversion over PRSS were higher than that over AC. Both hydrogen production (per unit volume of ethanol) and ethanol conversion increased with the increase of MP, whereas decreased with the increase of the volumetric hourly space velocity of ethanol (VHSV_eth). Additionally, comparison between ethanol decomposition by MW and conventional heating was also conducted. Results indicated that MW heating was much more beneficial for hydrogen production than conventional heating, and the energy efficiency of hydrogen production under MW heating was much higher than conventional heating. Finally, carbon nanofilaments formation over PRSS and AC were observed under MW heating. The size and structures of carbon nanofilaments over PRSS and AC were significantly different with each other, which may be strongly correlated with the formation of micro-plasmas during MW heating.     

Studies on ethanol production from water hyacinth—A review

With industrial development growing rapidly, there is a need for environmentally sustainable energy sources. Ethanol from biomass, bioethanol, is an attractive, sustainable energy fuel source for transportation. Based on the premise that fuel bioethanol can contribute to a cleaner environment and with the implementation of environmental protection laws in many countries, demand for this fuel is increasing. Efficient ethanol production is based on optimized processes where utilization of cheap substrates is highly demanding. Utilization of different types of lignocellulosic materials can be considered for production of ethanol. Among various types of lignocellulosic substances water hyacinth (Eichhornia crassipes) is a potential resource available in many tropical regions of the world. It is a noxious aquatic weed which grows fast. A considerable amount of research work is in progress for its bioconversion into ethanol using two-sequential steps of hydrolysis and fermentation. This paper reviews the bioconversion of water hyacinth to ethanol.     

A review on biomass‐based hydrogen production for renewable energy supply

This article gives an overview of the state‐of‐the‐art biomass‐based hydrogen production technologies. Various biological and thermochemical processes of biomass are taken into consideration to find the most economical method of hydrogen production. Biohydrogen generated by biophotolysis method, photo‐fermentation and dark fermentation is studied with respect to various feedstocks in Malaysia. The fermentation approaches of biohydrogen production have shown great potential to be a future substitute of fossil fuels. Dark fermentation method is a simple biological hydrogen production method that uses a variety of substrate and does not require any light as a source of energy. A promising future for biohydrogen production is anticipated by this process both industrially and commercially. Feasibility of hydrogen production from pyrolysis and water gasification of various biomass feedstock confirm that supercritical water gasification (SCWG) of biomass is the most cost‐effective thermochemical process. Highly moisturized biomass could be employed directly in SCWG without any high‐cost drying process. Indeed, a small amount of energy is required to pressurize hydrogen in the storage tank because of highly pressurized SCWG process. The cost of hydrogen produced by SCWG of biomass is about US$3/GJ (US$0.35/kg), which is extremely lower than biomass pyrolysis method (in the range of US$8.86/GJ to US$15.52/GJ) and wind‐electrolysis systems and PV‐electrolysis systems (US$20.2/GJ and US$41.8/GJ, respectively). The best feedstock for biomass‐based hydrogen production is identified based on the availability, location of the sources, processes required for the preparation of the feedstock and the total cost of acquiring the feedstock. The cheapest and most abundantly available biomass source in Malaysia is the waste of palm industry. Hydrogen production from palm oil mill effluent and palm solid residue could play a crucial role in the energy mix of Malaysia. Malaysia has this great capability to supply about 40% of its annual energy demand by hydrogen production from SCWG of palm solid waste. Copyright © 2015 John Wiley & Sons, Ltd.     

A review of hydrogen production and supply chain modeling and optimization

This paper reviews recent optimization models for hydrogen supply chains and production. Optimization is a central component of systematic methodologies to support hydrogen expansion. Hydrogen production is expected to evolve in the coming years to help replace fossil fuels; these high expectations arise from the potential to produce low-carbon hydrogen via electrolysis using electricity generated by renewable sources. However, hydrogen is currently mainly used in refinery and industrial operations; therefore, physical infrastructures for transmission, distribution, integration with other energy systems, and efficient hydrogen production processes are lacking. Given the potential of hydrogen, the greenfield state of infrastructures, and the variability of renewable sources, systematic methodologies are needed to reach competitive hydrogen prices, and design hydrogen supply chains. Future research topics are identified: 1) improved hydrogen demand projections, 2) integrated sector modeling, 3) improving temporal and spatial resolutions, 4) accounting for climate change, 5) new methods to address sophisticated models.     

Hydrogen production from agricultural waste by dark fermentation: A review

The degradation of the natural environment and the energy crisis are two vital issues for sustainable development worldwide. Hydrogen is considered as one of the most promising candidates as a substitute for fossil fuels. In this context, biological processes are considered as the most environmentally friendly alternatives for satisfying future hydrogen demands. In particular, biohydrogen production from agricultural waste is very advantageous since agri-wastes are abundant, cheap, renewable and highly biodegradable. Considering that such wastes are complex substrates and can be degraded biologically by complex microbial ecosystems, the present paper focuses on dark fermentation as a key technology for producing hydrogen from crop residues, livestock waste and food waste. In this review, recent findings on biohydrogen production from agricultural wastes by dark fermentation are reported. Key operational parameters such as pH, partial pressure, temperature and microbial actors are discussed to facilitate further research in this domain.     

Potential of bio-hydrogen production from dark fermentation of crop residues: A review

This study provided an estimate of the potential of bio-hydrogen production from dark fermentation of crop residues on a worldwide scale. The different crop residues reviewed included sugarcane tops, leaves and bagasse, corn straw, corn cob and corn stover, wheat straw, rice straw and husk, soybean straw, oil palm trunk and empty fruit bunch, sugar beet pulp, cassava residue, barley straw and sweet sorghum bagasse. Among these crop residues, wheat and rice straws are produced in the highest amount although sugarcane dominates crop production on a worldwide scale. Based on the bio-hydrogen yields reported in literature, estimated worldwide bio-hydrogen potential is highest for untreated rice straw at 58,002 Mm³/year followed by untreated wheat straw at 34,680 Mm³/year. This corresponds to a bio-energy potential of 623 PJ/year and 373 PJ/year for raw rice straw and wheat straw respectively while pre-treatment of the crop residues significantly increases the bio-hydrogen and bio-energy potential. While dark fermentation of crop residues offers a huge bio-energy potential, the process suffers from several constraints that hinder its implementation. As such, coupling of the dark fermentation process with the anaerobic digestion process as a two-stage process seems the most economically viable option for large-scale implementation.     

纤维素燃料乙醇预处理技术研究进展

木质纤维素类生物质可经过预处理-酶水解-发酵等过程转化为纤维素燃料乙醇,其不仅是粮食乙醇的有益补充,还是未来生物燃料发展的主要方向。预处理是制备纤维素燃料乙醇的关键步骤,预处理可以破坏木质纤维素原料的致密结构,提高底物与纤维素酶之间的可及性,从而提高后续的酶解和发酵效率。目前,预处理技术主要包括物理法、生物法、化学法和物理化学法。文章主要对碱法、酸法等重要的化学预处理方法进行了论述,对近年来新开发的有机溶剂和离子液体溶剂体系预处理的研究进行了重点分析,其中有机溶剂体系具有对设备腐蚀较小的优点,离子液体溶剂体系具有热稳定性和化学稳定性高的优点。目前,二者是生物质预处理技术的研究热点。     

An oil palm-based biorefinery concept for cellulosic ethanol and phytochemicals production: Sustainability evaluation using exergetic life cycle assessment

In this study, thermo-environmental sustainability of an oil palm-based biorefinery concept for the co-production of cellulosic ethanol and phytochemicals from oil palm fronds (OPFs) was evaluated based on exergetic life cycle assessment (ExLCA). For the production of 1 tonne bioethanol, the exergy content of oil palm seeds was upgraded from 236 MJ to 77,999 MJ during the farming process for OPFs production. Again, the high exergy content of the OPFs was degraded by about 62.02% and 98.36% when they were converted into cellulosic ethanol and phenolic compounds respectively. With a total exergy destruction of about 958,606 MJ (internal) and 120,491 MJ (external or exergy of wastes), the biorefinery recorded an overall exergy efficiency and thermodynamic sustainability index (TSI) of about 59.05% and 2.44 per tonne of OPFs' bioethanol respectively. Due to the use of fossil fuels, pesticides, fertilizers and other toxic chemicals during the production, the global warming potential (GWP = 2265.69 kg CO₂ eq.), acidification potential (AP = 355.34 kg SO₂ eq.) and human toxicity potential (HTP = 142.79 kg DCB eq.) were the most significant environmental impact categories for a tonne of bioethanol produced in the biorefinery. The simultaneous saccharification and fermentation (SSF) unit emerged as the most exergetically efficient (89.66%), thermodynamically sustainable (TSI = 9.67) and environmentally friendly (6.59% of total GWP) production system.     

Anaerobic fermentation technology increases biomass energy use efficiency in crop residue utilization and biogas production

A biomass energy utilization project (Corn stalk→Cattle→Cattle dung→Biogas digester→Biogas/Digester residues→Soil) was conducted in a typical temperate agro-village of China from 2005 to 2010. The present study focused on two key approaches of the ecological loop: (1) increasing corn stalk use efficiency by improving anaerobic fermentation technology; and (2) enhancing biogas productivity by optimizing fermentation conditions. Our results showed that crude protein and fat of corn stalks significantly increased, while crude fiber content and pH decreased considerably during anaerobic fermentation. The cattle digestion rate, forage consumption and increases in cattle weight were higher in cattle fed fermented corn stalks than in those fed non-fermented corn stalks. The rate of biogas production was higher (78.4%) by using cattle dung as a substrate than using crop residues. Heat preservation measures effectively enhanced the biogas production rate (12.3%). In 2005, only two cattle were fed in this village, with only 1.1% corn stalk utilized as forage. No more than three biogas digesters existed, and the proportion of biogas energy used in total household fuel was only 1.7%. At the end of the 5-year experiment, the number of cattle capita reached 169 with 78.9% corn stalk used as forage. Biogas digesters increased to 130, and the proportion of biogas energy used in total household fuel was up to 42.3%. A significant positive correlation was noted between the increasing rate of farmers’ incomes and the proportion of corn stalks used as forage. Available nutrients were higher in fermented cattle dung than in fresh cattle dung. Our findings clearly suggest that anaerobic fermentation technology is important in enhancing crop residue use efficiency, biogas productivity and soil fertility. Fermentation technology may help reduce the use of fossil fuels and improve the environment in rural areas.     

Screening of thermotolerant yeast by low-energy ion implantation for cellulosic ethanol fermentation

One thermotolerant mutant, ST-1559, was selected after mutagenizing with ion beam implantation. The results showed that ST-1559 could grow well under 45°C,and its ethanol yield reached 109.46 g/L when the glucose content was 250 g/L in the fermentation medium. When corn straw which was pretreated by NaOH was used as substrate in fermentation experiment under 45°C, it produced 13.48 g/L ethanol, and 82.17% of the cellulose was achieved. These results suggest that ST-1559 had advantage in simultaneous saccharification and fermentation.