Showing papers in "Biomass & Bioenergy in 2008"

Jatropha bio-diesel production and use

Abstract: The interest in using Jatropha curcas L. (JCL) as a feedstock for the production of bio-diesel is rapidly growing. The properties of the crop and its oil have persuaded investors, policy makers and clean development mechanism (CDM) project developers to consider JCL as a substitute for fossil fuels to reduce greenhouse gas emissions. However, JCL is still a wild plant of which basic agronomic properties are not thoroughly understood and the environmental effects have not been investigated yet. Gray literature reports are very optimistic on simultaneous wasteland reclamation capability and oil yields, further fueling the Jatropha bio-diesel hype. In this paper, we give an overview of the currently available information on the different process steps of the production process of bio-diesel from JCL, being cultivation and production of seeds, extraction of the oil, conversion to and the use of the bio-diesel and the by-products. Based on this collection of data and information the best available practice, the shortcomings and the potential environmental risks and benefits are discussed for each production step. The review concludes with a call for general precaution and for science to be applied. (C) 2008 Elsevier Ltd. All rights reserved.

Green house gases emissions in the production and use of ethanol from sugarcane in Brazil: the 2005/2006 averages and a prediction for 2020.

Abstract: This work presents the evaluation of energy balance and GHG emissions in the production and use of fuel ethanol from cane in Brazil for 2005/2006 (for a sample of mills processing up to 100 million tons of sugarcane per year), and for a conservative scenario proposed for 2020. Fossil energy ratio was 9.3 for 2005/2006 and may reach 11.6 in 2020 with technologies already commercial. For anhydrous ethanol production the total GHG emission was 436 kg CO 2 eq m −3 ethanol for 2005/2006, decreasing to 345 kg CO 2 eq m −3 in the 2020 scenario. Avoided emissions depend on the final use: for E100 use in Brazil they were (in 2005/2006) 2181 kg CO 2 eq m −3 ethanol, and for E25 they were 2323 kg CO 2 eq m −3 ethanol (anhydrous). Both values would increase about 26% for the conditions assumed for 2020 mostly due to the large increase in sales of electricity surpluses. A sensitivity analysis has been performed (with 2005/2006 values) to investigate the impacts of the huge variation of some important parameters throughout Brazilian mills on the energy and emissions balance. The results have shown the high impact of cane productivity and ethanol yield variation on these balances (and the impacts of average cane transportation distances, level of soil cultivation, and some others) and of bagasse and electricity surpluses on GHG emissions avoidance.

Simulation of biomass gasification in fluidized bed reactor using ASPEN PLUS.

Abstract: A comprehensive process model is developed for biomass gasification in an atmospheric fluidized bed gasifier using the ASPEN PLUS simulator. The proposed model addresses both hydrodynamic parameters and reaction kinetic modeling. Governing hydrodynamic equations for a bubbling bed and kinetic expressions for the char combustion are adopted from the literature. Four ASPEN PLUS reactor models and external FORTRAN subroutines for hydrodynamics and kinetics nested in ASPEN PLUS simulate the gasification process. Different sets of operating conditions for a lab-scale pine gasifier are used to demonstrate validation of the model. Temperature increases the production of hydrogen and enhances carbon conversion efficiency. Equivalence ratio is directly proportional to carbon dioxide production and carbon conversion efficiency. Increasing steam-to-biomass ratio increases hydrogen and carbon monoxide production and decreases carbon dioxide and carbon conversion efficiency. Particle average size in the range of 0.25–0.75 mm does not seem to contribute significantly to the composition of product gases.

Contemporary issues in thermal gasification of biomass and its application to electricity and fuel production.

Abstract: Gasification technology has been investigated to effectively and economically convert low-value and highly distributed solid biomass to a uniform gaseous mixture mainly including hydrogen (H 2 ), carbon monoxide (CO), methane (CH 4 ) and carbon dioxide (CO 2 ). This gaseous mixture can be further used as an industrial feedstock for heat and power generation, H 2 production and synthesis of liquid fuels. Significant advances have been made in the technology of biomass gasification and syngas utilization. This review was conducted to introduce the recent advances in biomass gasification and syngas utilization. The critical technical issues and perspectives of biomass gasification were discussed.

Techno-Economic Evaluation of Bioethanol Production from Three Different Lignocellulosic Materials

Abstract: The lignocellulosic materials spruce (softwood), Salix (hardwood) and corn stover (agricultural residue) are all potential feedstock for ethanol production. In this study the utilization of these materials for bioethanol production was compared in terms of production cost and energy demand using a process concept based on SO2-catalysed steam pretreatment followed by simultaneous saccharification and fermentation (SSF). A model including all major process steps was implemented in the commercial flowsheeting program Aspen Plus, and the model input was based on data recently obtained on lab scale or in a process development unit. The main focus of the study was on the pretreatment and the SSF steps. Sensitivity analyses of important process parameters showed their relative effects on the production cost and on the potential for cost reduction for each raw material. The study clearly demonstrates the importance of a high ethanol yield and the necessity of utilizing the pentose fraction for ethanol production to obtain good process economy, especially when using Salix or corn stover. Furthermore, a less energy-demanding process, here mainly achieved by increasing the dry matter content in SSF, reduces the capital cost and results in higher co-product credit, and therefore has a significant effect on the overall process economy. (Less)

Costs of producing miscanthus and switchgrass for bioenergy in Illinois

Abstract: There is growing interest in using perennial grasses as renewable fuels for generating electricity and for producing bio-ethanol. This paper examines the costs of producing two bioenergy crops, switchgrass and miscanthus, in Illinois for co-firing with coal to generate electricity. A crop-productivity model, MISCANMOD, is used together with a GIS to estimate yields of miscanthus across counties in Illinois. Spatially variable yields, together with county-specific opportunity costs of land, are used to determine the spatial variability in the breakeven farm-gate price of miscanthus. Costs of transporting bioenergy crops to the nearest existing power plant are incorporated to obtain delivered costs of bioenergy. The breakeven delivered cost of miscanthus for an average yield of 35.76 t ha−1 in Illinois is found to be less than two-thirds of the breakeven price of switchgrass with an average yield of 9.4 t ha−1. There is considerable spatial variability in the breakeven farm-gate price of miscanthus, which ranges between 41 and 58 $ t−1 across the various counties in Illinois. This together with differences in the distances miscanthus has to be shipped to the nearest power plant causes variability in the costs of using bioenergy to produce electricity. The breakeven cost of bioenergy for electricity generation ranges from 44 to 80 $ t−1 DM and is considerably higher than the coal energy-equivalent biomass price of 20.22 $ t−1 DM that power plants in Illinois might be willing to pay. These findings imply a need for policies that will provide incentives for producing and using bioenergy crops based on their environmental benefits in addition to their energy content.

Production of biodiesel from high free fatty acid Karanja (Pongamia pinnata) oil

Abstract: Non-edible oil contains several unsaponifiable and toxic components, which make them unsuitable for human consumption. Karanja ( Pongamia pinnata ) is an underutilized plant which is grown in many parts of India. Sometimes the oil is contaminated with high free fatty acids (FFAs) depending upon the moisture content in the seed during collection as well as oil expression. The present study deals with production of biodiesel from high FFA Karanja oil because the conventional alkali-catalyzed route is not the feasible route. This paper discusses the mechanism of a dual process adopted for the production of biodiesel from Karanja oil containing FFA up to 20%. The first step is acid-catalyzed esterification by using 0.5% H 2 SO 4 , alcohol 6:1 molar ratio with respect to the high FFA Karanja oil to produce methyl ester by lowering the acid value, and the next step is alkali-catalyzed transesterification. The yield of biodiesel from high FFA Karanja oil by dual step process has been observed to be 96.6–97%.

Biotechnological valorisation of raw glycerol discharged after bio-diesel (fatty acid methyl esters) manufacturing process: Production of 1,3-propanediol, citric acid and single cell oil

Abstract: Raw glycerol, byproduct from bio-diesel production process, is used as carbon substrate in several biotechnological applications. Using Clostridium butyricum F2b, 47.1 g L−1 of 1,3-propanediol was produced in batch anaerobic cultures while substrate uptake rate (rS, expressed in g L−1 h−1) increased with increase in glycerol concentration in the medium. In continuous cultures, microbial behaviour was studied in transitory states after addition of 1,3-propanediol in the chemostat vessel. Microbial growth was not affected by the high 1,3-propanediol (which was added in the chemostat vessel) concentration, while butyric and acetic acids concentrations were increased. In a two-stage continuous culture, 43.5 g L−1 of 1,3-propanediol was produced with a total volumetric productivity of 1.33 g L−1 h−1. Yarrowia lipolytica ACA-DC 50109 was grown in nitrogen-limited aerobic cultures on raw glycerol and it exhibited remarkable biomass production even at high glycerol concentration media, while rS decreased with increase in glycerol concentration. Citric acid was produced after nitrogen depletion in the medium, with the highest quantity of 62.5 g L−1, and yield on glycerol consumed was 0.56 g g−1. Fatty acid analysis of total cellular lipids showed that glycerol concentration increase in the growth medium somehow increased the cellular unsaturated fatty acids content of lipids. Mortierella isabellina ATHUM 2935 exhibited satisfactory growth in nitrogen-limited aerobic cultures with raw glycerol used as sole substrate. When high initial glycerol quantities were employed (e.g. 100 g L−1), 4.4 g L−1 of lipid were accumulated corresponding to around 51% (wt/wt) of lipid in dry weight. rS constantly decreased with increase in glycerol concentration in the medium, and in all cases notable glycerol quantities remained unconsumed in the medium.

Mineral composition and ash content of six major energy crops.

Abstract: The chemical composition of biofuels has not received adequate attention given that it is an important aspect in the introduction of energy crops In this study, the ash content and mineral composition (C, N, Al, Ca, Cl, Fe, K, Mg, Na, P, S, Si) of stems, leaves and reproductive organs of some promising energy crops were determined and compared with the respective recommended thresholds reported in literature Overall, cynara exhibited the highest ash and mineral contents, which indicate high slagging, fouling and corrosion tendencies However, cynara also showed the lowest Si content, both in leaves (43 g kg −1 ) and in stems (09 g kg −1 ) Sweet sorghum and giant reed exhibited the highest N content (up to 16 g kg −1 ), which greatly exceeded the recommended limits in leaves Importantly, Cl always exceeded the recommended limits (up to 18 mg kg −1 in cynara), both in stems and in leaves, thus resulting in a major stumbling block for all crops Several significant correlations among elements were found at a single plant part; conversely these correlations were generally very weak considering different plant components, with the exception of K ( r =091**), P ( r =094**) and ashes ( r =064**) Generally, leaves resulted in a significant deterioration of biofuel quality when compared with stems and flower heads Therefore, agricultural strategies aimed at reducing the leaf component (eg by delaying the harvest) may considerably improve the suitability of biofuels for current combustion plants

Esterification of free fatty acids using sulfuric acid as catalyst in the presence of triglycerides

Abstract: Biodiesel is one of the new possible substitutes of regular fuel for engines and is produced from different vegetable oils or animal fats. The main reaction involved is the transesterification of triglycerides into esters. When an acid oil, such as spent or waste oil, is used, the amount of free fatty acids range from 3% to 40%, and another reaction takes place simultaneously with the transesterification, the direct esterification of the free fatty acid. In this work, the direct esterification reaction of triglycerides to biodiesel was studied and the effects of the main variables involved in the process, reaction temperature, amount of catalyst, initial amount of free fatty acid and the molar ratio alcohol/oil, were analyzed. For this investigation, we employed a model acid oil produced by mixing pure oleic acid with refined sunflower oil. Ethanol was used in the experiments instead of methanol since it is less toxic and safer to handle. Sulfuric acid was employed as catalyst because of its advantages compared with conventional homogeneous catalysts (NaOH). It was found that ethanol and sulfuric acid were suitable to perform not only the transesterification reaction but also the direct esterification reaction to increase biodiesel production of the process.

Butanol production from wheat straw by simultaneous saccharification and fermentation using Clostridium beijerinckii: Part II—Fed-batch fermentation

Abstract: In these studies, Clostridium beijerinckii P260 was used to produce butanol (acetone–butanol–ethanol, or ABE) from wheat straw (WS) hydrolysate in a fed-batch reactor It has been demonstrated that simultaneous hydrolysis of WS to achieve 100% hydrolysis to simple sugars (to the extent achievable under present conditions) and fermentation to butanol is possible In addition to WS, the reactor was fed with a sugar solution containing glucose, xylose, arabinose, galactose, and mannose The culture utilized all of the above sugars It was noticed that near the end of fermentation (286–533 h), the culture had difficulties utilizing xylose As a result of supplemental sugar feed to the reactor, ABE productivity was improved by 16% as compared with previous studies In our previous experiment on simultaneous saccharification of WS and fermentation to butanol, a productivity of 031 g L −1 h −1 was observed, while in the present studies a productivity of 036 g L −1 h −1 was observed It should be noted that a productivity of 077 g L −1 h −1 was observed when the culture was highly active The fed-batch fermentation was operated for 533 h It should be noted that C beijerinckii P260 can be used to produce butanol from WS in integrated fermentations

Different palm oil production systems for energy purposes and their greenhouse gas implications

Abstract: This study analyses the greenhouse gas (GHG) emissions of crude palm oil (CPO) and palm fatty acid distillate (PFAD) production in northern Borneo (Malaysia), their transport to the Netherlands and their co-firing with natural gas for electricity production. In the case of CPO, conversion to biodiesel and the associated GHG emissions are also studied. This study follows the methodology suggested by the Dutch Commission on Sustainable Biomass (Cramer Commission). The results demonstrate that land use change is the most decisive factor in overall GHG emissions and that palm oil energy chains based on land that was previously natural rainforest or peatland have such large emissions that they cannot meet the 50–70% GHG emission reduction target set by the Cramer Commission. However, if CPO production takes place on degraded land, management of CPO production is improved, or if the by-product PFAD is used for electricity production, the emission reduction criteria can be met, and palm-oil-based electricity can be considered sustainable from a GHG emission point of view. Even though the biodiesel base case on logged-over forest meets the Cramer Commission's emission reduction target for biofuels of 30%, other cases, such as oil palm plantations on degraded land and improved management, can achieve emissions reductions of more than 150%, turning oil palm plantations into carbon sinks. In order for bioenergy to be sustainably produced from palm oil and its derivatives, degraded land should be used for palm oil production and management should be improved.

Thermogravimetric characterization of corn stover as gasification and pyrolysis feedstock

Abstract: Interest in generating energy from biomass has grown tremendously in recent years. Corn stover is an agricultural by-product, which is abundant in quantity. Gasification and pyrolysis are efficient methods of harnessing energy efficiently from corn stover. The performances of mathematical models to predict the product gas quality rely on characterization of feed materials and the reaction kinetics of their thermal degradation. The objective of this research was to determine selected physical and chemical properties of corn stover related to thermochemical conversion. Thermogravimetric analyses were performed at heating rates of 10, 30, and 50 °C min−1 in nitrogen (inert) and air (oxidizing) atmospheres. The parameters of the reaction kinetics were obtained and compared with other biomass. The weight losses of corn stover in both inert and oxidizing atmospheres were found to occur in three stages.

Evaluation of marine algae as a source of biogas in a two-stage anaerobic reactor system.

Abstract: The marine algae are considered an important biomass source; however, their utilization as energy source is still low around the world. The technical feasibility of marine algae utilization as a source of renewable energy was studied to laboratory scale. The anaerobic digestion of Macrocystis pyrifera, Durvillea antarctica and their blend 1:1 (w/w) was evaluated in a two-phase anaerobic digestion system, which consisted of an anaerobic sequencing batch reactor (ASBR) and an upflow anaerobic filter (UAF). The results show that 70% of the total biogas produced in the system was generated in the UAF, and both algae species have similar biogas productions of 180.4(±1.5) mL g−1 dry algae d−1, with a methane concentration around 65%. The same methane content was observed in biogas yield of algae blend; however, a lower biogas yield was obtained. In conclusion, either algae species or their blend can be utilized to produce methane gas in a two-phase digestion system.

Prospects and risks of the use of castor oil as a fuel

Abstract: Castor oil is more than just a raw material in great demand by the pharmaceutical and chemical industries. In several southern countries its use as a fuel is also being discussed in connection with social and ecological aspects. A few properties, in particular the extremely high viscosity and high water content, complicate the use of straight castor oil as a fuel for internal combustion engines. A better perspective may be possible by transesterification and the addition of this biodiesel to fossil diesel fuel. This, however, calls for considerably lower castor oil prices than are at present being paid on the world market.

Simulation of hydrogen production from biomass gasification in interconnected fluidized beds

Abstract: Hydrogen production from biomass gasification in interconnected fluidized beds is proposed in this paper. It resembles a circulating fluidized bed with the extra bubbling fluidized bed after the cyclone. The circulating fluidized bed is designed for combustion fed with air, the bubbling fluidized bed for biomass gasification fed with steam. Direct contact between the gasification and combustion processes is avoided; the gasification-required heat is achieved by means of the circulation of bed particles. Hydrogen-rich gas is produced free of N2 dilution. The paper intends to provide some process fundamentals about hydrogen production from biomass gasification in interconnected fluidized beds. Simulation of the processes, including chemical reactions and heat/mass balance, is carried out with Aspen Plus software. The effects of gasifier temperature and steam/biomass ratio on the composition of fuel gas, hydrogen yield, carbon conversion of biomass, recirculation of bed particles, etc., are discussed. Some useful results are achieved. The results indicate that both a high hydrogen content and a relatively great hydrogen yield are obtained from biomass gasification in interconnected fluidized beds. The favorable temperature of the gasifier should be between 750 and 800 °C, the combustor temperature should be 920 °C, and the ratio of the steam/biomass should be between 0.6 and 0.7. The increment of hydrogen yield is distinct with the increase of steam/biomass ratio at the lower gasifier temperatures (below 750 °C). The steam/biomass ratio corresponding to maximal hydrogen yield declines with the increase of gasifier temperature. To maintain the gasifier temperature, the recirculation of bed particles increased exponentially with an increase in the gasifier temperature.

Production of sunflower oil methyl esters by optimized alkali-catalyzed methanolysis.

Abstract: We report the optimization of sunflower oil methyl esters (SOME/biodiesel) production via alkaline catalyzed transesterification of crude sunflower oil and subsequent physical and chemical characterization. The optimum conditions elucidated for the methanolysis of sunflower oil were found to be: methanol/sunflower oil molar ratio, 6:1; reaction temperature, 60 °C; and NaOH catalyst concentration, 1.00% (w/w). An optimum SOME yield of 97.1% was achieved. SOME were analyzed by gas–liquid chromatography (GLC). A number of fuel properties of SOME as measured according to accepted methods were found to satisfy nearly all prescribed ASTM D 6751 specifications, where applicable. The results of the present study indicated that SOME could be a potential alternative to other common biodiesels and petrodiesel.

Overview of recent developments in sustainable biomass certification

Abstract: The objective of this paper is to give a comprehensive review of initiatives on biomass certification from different viewpoints of stakeholders, including national governments (such as The Netherlands, the UK, Belgium and Germany), the EC, NGOs, companies, and international bodies up until October 2007. Furthermore, opportunities and restrictions in the development of biomass certification are described, including international trade law limitations, lack of adequate methodologies, stakeholder involvement requirements and certification costs. Next, five different approaches for the implementation of a biomass certification system are compared and discussed. Main differences are the voluntary or mandatory character and the geographical extent of the proposed strategies in terms of biomass end-use. It is concluded that criteria to ensure the sustainable production of biomass are needed urgently. To some extent criteria categories can be covered using existing systems, but others (such as GHG and energy balances, changing land-use) require the development of new methodologies. A gradual development of certification systems with learning (through pilot studies and research) and expansion over time, linked to the development of advanced methodologies can provide valuable experience, and further improve the feasibility and reliability of biomass certification systems. However, better international coordination between initiatives is required to improve coherence and efficiency in the development of sustainable biomass certification systems, to avoid the proliferation of standards and to provide a clearer direction in the approach to be taken. Finally, next to certification, alternative policy tools should be considered as well to ensure sustainable biomass production.

The sustainability of Brazilian ethanol - an assessment of the possibilities of certified production

Abstract: In this article the environmental and socio-economical impacts of the production of ethanol from sugarcane in the state of Sao Paulo (Brazil) are evaluated. Subsequently, an attempt is made to determine to what extent these impacts are a bottleneck for a sustainable and certified ethanol production. Seventeen environmental and socio-economic areas of concern are analysed. Four parameters are used to evaluate if an area of concern is a bottleneck: (1) the importance of the area of concern, based on the severity of the impact and the frequency of which an aspect is mentioned in the literature as an area of concern, (2) the availability of indicators and criteria, (3) the necessity of improvement strategies to reach compliance with Brazilian and/or (inter) national legislation, standards, guidelines and sustainability criteria, and (4) the impact of these improvement strategies on the costs and potential of ethanol production. Fourteen areas of concern are classified as a minor or medium bottleneck. For 7 areas of concern the additional costs to avoid or reduce undesirable effects have been calculated at ⩽+10% for each area of concern. Due to higher yields and overlapping costs the total additional production costs of compliance with various environmental and socio-economic criteria are about +36%. This study also shows that the energy input to output ratio can be increased and the greenhouse gas emissions reduced by increasing the ethanol production per tonne cane and by increasing the use of sugarcane waste for electricity production. A major bottleneck for a sustainable and certified production is the increase in cane production and the possible impacts on biodiversity and the competition with food production. Genetically modified cane is presently being developed, but is at this moment not (yet) applied. Both a ban on and the allowance of the use of genetically modified cane could become a major bottleneck considering the potentially large benefits and disadvantages, that are both highly uncertain at this moment. The approach demonstrated in this report provides a useful framework for the development of a practically applicable certification system, but further monitoring and research is required to reduce gaps in knowledge in combination with stakeholder consultation (particularly with respect to the three bottlenecks identified in this article).

The optimal size for biogas plants

Abstract: The costs of biogas and electricity production from maize silage in relation to plant size are investigated in this paper. A survey of manufacturers’ engineering data was conducted to derive a reliable relationship between the capacity of a combined heat and power (CHP) unit and its electrical efficiency. Then a model was developed to derive cost curves for the unit costs of biogas and electricity production and for the transport costs for maize silage and biogas slurry. The least-cost plant capacity depends to a great extent on the local availability of silage maize, and ranges in the model calculations from 575 to 1150 kW el . Finally, the paper deals with the optimum operating plant size due to the investment support available and the graduated tariff for green electricity in Austria.

GIS-based approach for defining bioenergy facilities location: A case study in Northern Spain based on marginal delivery costs and resources competition between facilities

Abstract: This paper presents a GIS-based decision support system for selecting least-cost bioenergy locations when there is a significant variability in biomass farmgate price and when more than one bioenergy plant with a fixed capacity has to be placed in the region. The methodology tackles the resources competition problem between energy facilities through a location-allocation model based on least-cost biomass quantities. Whole system least delivery cost including intermediate bioenergy products is estimated. The methodology is based on a case study where forest wood residues (FWR) from final cuttings (FCs) are used to produce torrefied wood (TW) in two torrefaction plants (TUs) that supply a gasification unit (GU) in order to produce electricity. The provinces of Navarra, Bizkaia, Gipuzkoa, Alava, La Rioja, Cantabria and Burgos are assessed in order to find the best locations for settling down the TUs and the GU according to biomass availability, FWR and TW marginal delivery costs.

The greenhouse gas and energy impacts of using wood instead of alternatives in residential construction in the United States

Abstract: Data developed by the Consortium for Research on Renewable Industrial Materials were used to estimate savings of greenhouse gas emissions and energy consumption associated with use of wood-based building materials in residential construction in the United States. Results indicate that houses with wood-based wall systems require 15–16% less total energy for non-heating/cooling purposes than thermally comparable houses employing alternative steel- or concrete-based building systems. Results for non-renewable energy consumption are essentially the same as those for total energy, reflecting the fact that most of the displaced energy is in fossil fuels. Over a 100-year period, net greenhouse gas emissions associated with wood-based houses are 20–50% lower than emissions associated with thermally comparable houses employing steel- or concrete-based building systems. Assuming 1.5 million single-family housing starts per year, the difference between wood and non-wood building systems represents about 9.6 Mt of CO 2 equivalents per year. The corresponding energy benefit associated with wood-based building materials is approximately 132 PJ year −1 . These estimates represent about 22% of embodied energy and 27% of embodied greenhouse gas emissions in the residential sector of the US economy. The results of the analysis are very sensitive to assumptions and uncertainties regarding the fate of forestland that is taken out of wood production due to reduced demand for wood, the continued production of co-products where demand for wood products is reduced, and the rate at which carbon accumulates in forests.

An environmental life cycle assessment comparing Australian sugarcane with US corn and UK sugar beet as producers of sugars for fermentation.

Abstract: Sugarcane is a highly suitable substrate for the production of bio-products. As well as producing high yields of sugar, much of the plant's fibre is also recovered and used as a source of renewable energy. A life cycle assessment (LCA) of sugarcane production and processing in Australia was performed to develop an environmental profile of sugarcane as a source of bio-products. The application examined was fermentation products from sugar. The sugarcane results were compared with results for other sugar producing crops—US corn and UK sugar beet—to gauge its relative environmental performance. The results show sugarcane to have an advantage in respect of energy input, greenhouse gas emissions and possibly acidification potential due to its high saccharide yield and the displacement of fossil fuels with surplus renewable energy from cane fibre (bagasse). However Australian sugarcane can exhibit high nitrous oxide emissions, which would reduce greenhouse gas advantages in some regions. For eutrophication, sugar beet provides advantages due to the avoided production of other agricultural crops displaced by the use of beet pulp as an animal feed. The three factors found to have the most influence on the environmental impacts of these agro-industrial systems were the commodities displaced by by-products, agricultural yields, and nitrogen use efficiency.

Steam pretreatment of dilute H2SO4-impregnated wheat straw and SSF with low yeast and enzyme loadings for bioethanol production.

Abstract: Conversion of lignocellulosic material to monomeric sugars and finally ethanol must be performed at low cost, i.e, with limited consumption of chemicals, yeast and enzymes while still reaching high yields, if it is to compete with other fuel conversion processes. The objective of this study was thus to investigate ethanol production from steam-pretreated wheat straw by simultaneous saccharification and fermentation (SSF). The concentration of sulphuric acid in the impregnation liquid prior to pretreatment was kept low, 0.2%, and SSF was performed at low enzyme loadings, 3-14 FPU g(-1) water-insoluble solids (WIS), and a low yeast concentration, 2 g L-1. The pretreatment conditions were optimised to give the highest overall glucose and xylose recovery after enzymatic hydrolysis of the residual WIS. The highest recovery of glucose (102%) and xylose (96%) was obtained after pretreatment at 190 degrees C for 10 min. Achieving high yields of glucose and xylose with the same pretreatment conditions is unusual and makes wheat straw a highly suitable raw material for bioethanol production. SSF was performed on whole slurry from straw pretreated under the optimal conditions. A high overall ethanol yield, 67% of the theoretical based on glucose in the raw material, was obtained. (Less)

Energy production from agricultural residues: High methane yields in pilot-scale two-stage anaerobic digestion

Abstract: There is a large, unutilised energy potential in agricultural waste fractions. In this pilot-scale study, the efficiency of a simple two-stage anaerobic digestion process was investigated for stabilisation and biomethanation of solid potato waste and sugar beet leaves, both separately and in co-digestion. A good phase separation between hydrolysis/acidification and methanogenesis was achieved, as indicated by the high carbon dioxide production, high volatile fatty acid concentration and low pH in the acidogenic reactors. Digestion of the individual substrates gave gross energy yields of 2.1–3.4 kWh/kg VS in the form of methane. Co-digestion, however, gave up to 60% higher methane yield, indicating that co-digestion resulted in improved methane production due to the positive synergism established in the digestion liquor. The integrity of the methane filters (MFs) was maintained throughout the period of operation, producing biogas with 60–78% methane content. A stable effluent pH showed that the methanogenic reactors had good ability to withstand the variations in load and volatile fatty acid concentrations that occurred in the two-stage process. The results of this pilot-scale study show that the two-stage anaerobic digestion system is suitable for effective conversion of semi-solid agricultural residues as potato waste and sugar beet leaves.

Lime pretreatment, enzymatic saccharification and fermentation of rice hulls to ethanol

Abstract: Rice hulls used in this study contained 35.6±0.1% cellulose and 12.0±0.7% hemicellulose. The maximum yield of monomeric sugars from rice hulls (15.0%, w/v) by lime pretreatment (100 mg g−1 hulls, 121 °C, 1 h) and enzymatic saccharification (45 °C, pH 5.0, 72 h) using a cocktail of three commercial enzyme preparations (cellulase, β-glucosidase and hemicellulase) at the dose level of 0.15 ml of each enzyme preparation g−1 hulls was 154±1 mg g−1 (32% yield). The lime pretreatment did not generate any detectable furfural and hydroxymethyl furfural in the hydrolyzate. The concentration of ethanol from lime-pretreated enzyme-saccharified rice hull (138 g) hydrolyzate by recombinant Escherichia coli strain FBR5 at pH 6.5 and 35 °C in 19 h was 9.8±0.5 g l−1 with a yield of 0.49 g g−1 available sugars. The ethanol concentration was 11.0±1.0 g l−1 in the case of simultaneous saccharification and fermentation by the E. coli strain at pH 6.0 and 35 °C in 53 h.

Enzymatic production of biodiesel from canola oil using immobilized lipase

Abstract: In the present work, a novel method for immobilization of lipase within hydrophilic polyurethane foams using polyglutaraldehyde was developed for the immobilization of Thermomyces lanuginosus lipase to produce biodiesel with canola oil and methanol. The enzyme optimum conditions were not affected by immobilization and the optimum pH for free and immobilized enzyme were 6, resulting in 80% immobilization yield. Using the immobilized lipase T. lanuginosus, the effects of enzyme loading, oil/alcohol molar ratio, water concentration, and temperature in the transesterification reaction were investigated. The optimal conditions for processing 20 g of refined canola oil were: 430 μg lipase, 1:6 oil/methanol molar ratio, 0.1 g water and 40 °C for the reactions with methanol. Maximum methyl esters yield was 90% of which enzymatic activity remained after 10 batches, when tert-butanol was adopted to remove by-product glycerol during repeated use of the lipase. The immobilized lipase proved to be stable and lost little activity when was subjected to repeated uses.

Effects of Nitrogen Fertilization on Biomass Yield and Quality in Large Fields of Established Switchgrass in Southern Iowa, USA

Abstract: Switchgrass ( Panicum virgatum L.) is a potential biofuel crop in the midwestern United States. The objective of this experiment was to test the effect of nitrogen application on biomass dry matter yield and fiber and mineral concentrations in large field plots in Lucas and Wayne counties in southern Iowa. Two established switchgrass fields with a previous history of limited management were evaluated from 1998 through 2002. Nitrogen was applied in the spring at rates of 0, 56, 112, and 224 kg N ha −1 , and a single biomass harvest was made in autumn. Biomass production averaged across locations and N levels increased by 3.6 mg ha −1 between 1998 and 2002 to 6.5 mg ha −1 . Nitrogen improved yields, with the response declining as N levels increased. The highest yield throughout the experiment was 8.5 mg ha −1 at the Lucas location in 2002. Changes in fiber and mineral concentrations did not follow any trend over years but were likely due to differences in harvest date among years. Nitrogen fertilization had no meaningful effect on the quality of the biofuel produced. This study clearly shows that nitrogen application and proper agronomic management can substantially increase the yield of established switchgrass fields over time without affecting the quality of the feedstock. As this experiment was conducted in large plots using commercial farm machinery, the results should be broadly applicable to real world situations.

Comparison of corn and switchgrass on marginal soils for bioenergy

Abstract: Crop residues such as corn (Zea mays L.) stover are viewed as an abundant and inexpensive source of biomass that can be removed from fields to produce bioenergy. Assumptions include that with minimum or no-tillage farming methods, there will be no deleterious production or environmental effects. A long-term field study was established in eastern Nebraska, USA, to compare the switchgrass managed as a biomass energy crop versus no-till corn on a non-irrigated site, marginal for row-crop production, in the western Corn Belt. Our objective in this paper is to report on corn stover removal effects on corn grain yields and potential ethanol production in both cropping systems. Corn, under no-till management, and switchgrass were grown at three N fertilizer levels. In the first 5 years (2001-2005), removal of half the available stover significantly reduced corn yields. During that same time period, the potential ethanol yield for switchgrass was equal to or greater than the potential total ethanol yield of corn grain and harvested stover fertilized at the same optimum N rate. The effect of crop residue removal on crop productivity needs to be investigated in other agro-ecosystems and the potential use of dedicated perennial biomass energy crops should remain a viable renewable energy option on non-irrigated marginal croplands.

The economics of harvesting and transporting corn stover for conversion to fuel ethanol: A case study for Minnesota

Abstract: Corn-stover feedstock costs were estimated for a proposed biomass-to-ethanol conversion facility in southern Minnesota, USA, accounting for county-specific yields and transportation distances, erosion constraints, machinery specifications, and transportation, storage, and densification costs. Monte Carlo simulation was used to estimate the probability distribution of costs under alternative assumptions on key parameters whose values vary widely in the literature. For a facility producing 0.189 hm 3 y −1 of ethanol, marginal feedstock cost was estimated at $60 Mg −1 ($200 m −3 ethanol) for the more-intensive harvest method and $72 Mg −1 ($210 m −3 ) for the less-intensive method. Costs were greater than $68 Mg −1 ($240 m −3 ) for a facility producing > 0.757 hm 3 y −1 ethanol under the more-intensive method, and greater than $93 Mg −1 ($320 m −3 ) for the less-intensive method. Monte Carlo simulation estimated a mean marginal cost of $57 Mg −1 ($69 Mg −3 under the less-intensive harvest method) for 0.189 hm 3 ethanol output, with a $12 ($10) standard deviation. Costs were found to be at or below $68 Mg −1 90 percent of the time ($78 Mg −1 for the less-intensive method). A $12 Mg −1 standard deviation in stover cost would result in a $40 m −3 swing in ethanol cost.