Showing papers in "Biomass & Bioenergy in 2012"

Review of fast pyrolysis of biomass and product upgrading

Abstract: This paper provides an updated review on fast pyrolysis of biomass for production of a liquid usually referred to as bio-oil. The technology of fast pyrolysis is described including the major reaction systems. The primary liquid product is characterised by reference to the many properties that impact on its use. These properties have caused increasingly extensive research to be undertaken to address properties that need modification and this area is reviewed in terms of physical, catalytic and chemical upgrading. Of particular note is the increasing diversity of methods and catalysts and particularly the complexity and sophistication of multi-functional catalyst systems. It is also important to see more companies involved in this technology area and increased take-up of evolving upgrading processes. © 2011 Elsevier Ltd.

Chemical characterization of rice straw-derived biochar for soil amendment

Abstract: Pyrolysis of rice straw to create biochar for soil amendment appears to be a promising method to address concerns with regard to improving soil fertility, increasing Carbon storage and decreasing Green House Gas emissions. However, the ability of rice straw-derived biochar to affect these factors might vary depending on its characteristics. It is therefore essential to investigate the properties before large-scale application of rice straw-derived biochar. In this study, rice straw-derived biochars produced at different temperatures (300, 400, 500, 600 & 700 °C) and residence time (1, 2, 3 & 5 h) were characterized using a suite of analytical techniques. Results showed that pyrolysis temperature had a greater influence than residence time on the chemical composition and structure of rice straw-derived biochar produced at low heating rate. The rice straw-derived biochars especially produced at 400 °C had high alkalinity and cation exchange capacity, and high levels of available phosphorus and extractable cations. These properties indicate potential application of rice straw-derived biochar as a fertilizer and soil amendment. Fourier transform infrared spectra showed that higher pyrolysis temperatures promote condensation reactions. Rice straw-derived biochars contained turbostratic crystallites at 400 °C, and displayed a high level of aromatization at 500 °C. Increasing charring temperature will increase the aromaticity of biochar, and might include its recalcitrance.

Hydrologic properties of biochars produced at different temperatures

Abstract: Adding charcoal to soil (biochar soil amendment) can sequester carbon and improve soil performance, although the extent and exact mechanisms of soil improvement are not clear. Additionally, biochar properties can vary significantly with production conditions. Here we characterize the impact of pyrolysis temperature on two important soil hydrologic properties: field capacity and hydrophobicity. We show that pure biochar exhibits a wide range in both properties depending on feedstock and pyrolysis conditions. We find that both properties can be controlled by choice of pyrolysis temperature; 400 °C–600 °C produced biochars with the most desirable hydrological properties (peak field capacity and minimum hydrophobicity). Further, we show that hydrophobicity is strongly correlated ( R 2 = 0.87; p

Assessment of the fertiliser potential of digestates from farm and agroindustrial residues

Abstract: The sustainability of biogas production systems depends greatly on the appropriate disposal of the digestates produced. The main agrochemical characteristics of 12 digestates from the anaerobic co-digestion of farm and agroindustrial residues were determined and compared with quality standards to assess their potential use as fertilisers. The digestates have a high fertilising potential, associated mainly with their contents of NH4-N; however, their recycling in agriculture might be restricted by their Cu and Zn contents, salinity, biodegradability, phytotoxicity and hygiene characteristics, which must be addressed to obtain the maximum benefits. Such characteristics determine the need for applying pre- or post-treatments to increase digestate quality until acceptable levels. Therefore, digestate quality must be taken into account when managing the co-digestion process, including substrate selection, in order to use digestates as fertilisers without the additional cost of post-digestion conditioning treatments.

Pretreatment: The key to efficient utilization of lignocellulosic materials

Abstract: Second-generation ethanol production from various lignocellulosic materials based on enzymatic hydrolysis of cellulose has moved from research in lab scale to pilot- and demo scale but has not yet reached commercial scale. One of the crucial process steps is the pretreatment of the biomass, which has as primary aim to make the biomass accessible to enzymatic attack, as it has a large impact on all the other steps in the process. Several pretreatment methods have been developed, comprising methods working at low pH, i.e., acid based, at medium pH (without addition of catalysts), or at high pH, i.e., with a base as catalyst. Many methods result in high sugar yields, above 90% of theoretical for agricultural residues while more recalcitrant materials like hardwood, and especially softwood, require dilute-acid pretreatment to reach high sugar yields. However, most studies on pretreatment have been assessed by enzymatic hydrolysis at low solids content and high enzyme dosages. The various pretreatment methods need in the future to be reassessed at more industrial-like conditions considering the whole integrated process taking into consideration the influence on all process steps. In this review, various pretreatment methods are discussed and how assessment should be performed to reach optimal conditions.

Disruption of microalgal cells for the extraction of lipids for biofuels: Processes and specific energy requirements

Abstract: Some species of microalgae have high lipid yields; however, all species of microalgae, with the only known exception of Botryococcus braunii, have their lipids located inside the cells. The toughness of cell walls and cell membranes of microalgae makes the lipids not readily available for extraction and means that cell disruption an energy intensive process. The cell disruption energy required may become a critical consideration in the production of low valued commodities such as biofuels. This study provides an overview of microalgal cell disruption processes which are potentially suitable for large scale lipid extractions. The energy requirements of these processes were calculated and then compared with estimates of the theoretical minimum energy required for disruption. The results show that the mechanical disruption methods considered were highly energy inefficient when conducted under laboratory conditions and required a specific energy consumption of at least 33 MJ kg −1 of dry biomass. Thus the specific energy consumption is greater than the energy recoverable from the microalgae and is also a factor of 10 5 greater than that the estimated minimum theoretical energy consumption. This result clearly shows that further research and innovation is required for the sustainable cell disruption and lipid extraction from microalgae.

Temperature dependence of density and viscosity of vegetable oils

Abstract: The straight use of vegetable oils as fuel in diesel engines entails adjusting several physical properties such as density and viscosity. By adequately heating the vegetable oil before entering the injection system, its physical parameters can reach values very close to that of diesel fuel. Consequently, by properly adjusting the temperature of vegetable oils used as fuel, it is possible to improve their combustion performance, thus avoiding premature engine aging due to incomplete burning. In this study the density and viscosity of several vegetable oils are studied within a wide variety of temperatures. The optimal range of temperatures at which each vegetable oil should operate in order to adjust its properties to those of automotive diesel and biodiesel is then found. Additionally an empirical relationship between the dependence of viscosity with density is presented. Thus, by means of the above-described relationship, through measuring the density of a given oil, its viscosity can be directly deduced.

Review of pretreatment processes for lignocellulosic ethanol production, and development of an innovative method

Abstract: Biomass pretreatment aims at separating and providing easier access to the main biomass components (cellulose, hemicellulose and lignin), eventually removing lignin, preserving the hemicellulose, reducing the cellulose crystallinity and increasing the porosity of the material. Pretreatment is an essential step towards the development and industrialization of efficient 2nd generation lignocellulosic ethanol processes. The present work reviewed the main options available in pretreatment. Autohydrolysis and steam explosion were then selected for further investigation. Experimental work was carried out on batch scale reactors, using Miscanthus as biomass feedstock: the effects on sugar solubilization and degradation products generation have been examined for each of these two pretreatment systems. A new process using only water and steam as reacting media was then developed, experimentally tested, and results compared to those achieved by the autohydrolysis and steam explosion processes. Products obtained with the new pretreatment contained a lower amount of usual fermentation inhibitor compounds compared to that typically obtained in steam explosion. This result was achieved under operating conditions that at the same time allowed a good xylan yield, preventing degradation of hemicelluloses. The new pretreatment process was also able to act as an equalization step, as the solid material from the pretreatment phase had a similar composition even under different operating conditions. As regards the effect of pretreatment on enzymatic hydrolysis, the new process achieved yields similar to steam explosion on glucans: however, this was obtained reducing the formation of degradation products from sugars, mainly from C5 sugars. These results made the proposed pretreatment system suitable for further development and industrialization on pilot and industrial scale.

Hydrothermal liquefaction of Nannochloropsis sp.: Systematic study of process variables and analysis of the product fractions

Abstract: We investigated hydrothermal liquefaction of Nannochloropsis sp. at different temperatures (250–400 °C), times (10–90 min), water densities (0.3–0.5 g/mL), and biomass loadings (5–35 wt %). Liquefaction produced a biocrude with light and heavy fractions, along with gaseous, aqueous, and solid by-product fractions. The gravimetric yields of the product fractions from experiments at 250 °C summed to an average of 100 ± 4 wt %, showing mass balance closure at 250 °C. The gravimetric yields of the product fractions are independent of water density at 400 °C. Increasing the biomass loading increases the biocrude yield from 36 to 46 wt %. The yields of light and heavy biocrude depend on reaction time and temperature, but their combined yield depends primarily on temperature. Regardless of reaction time and temperature, the yield of products distributed to the aqueous phase is 51 ± 5 wt % and the light biocrude is 75 ± 1 wt % C. Two-thirds of the N in the alga is immediately distributed to the aqueous phase and up to 84% can be partitioned there. Up to 85% of the P is distributed to the aqueous phase in the form of free phosphate. Thus, N and P can be recovered in the aqueous phase for nutrient recycling. Up to 80% of the chemical energy in the alga is retained within the biocrude. The quantitative results reported herein provide the basis for a reaction network for algae liquefaction.

Lignocellulosic ethanol: from science to industry.

Abstract: Lignocellulosic raw materials, not competing with food production, can provide environmental, economic, and strategic benefits for the production of biofuels. The cost of biomass-based biotechnical ethanol production has been recently reduced significantly, mainly due to advances in the conversion techniques; i.e. by improved enzymes and new yeast strains. Conversion of the cellulosic components into fermentable sugars is, however, still the major technological and economical bottleneck in the production of fuels or other high-volume commodity products from cellulosic biomass. Especially, the enzymatic hydrolysis still forms a major cost factor. The targets for reducing the costs of biotechnical conversion processes of lignocelluloses to ethanol can be divided into three categories: the costs of enzymes, the costs of produced sugars and the costs of ethanol production. The efficiencies of individual enzymes can be improved by designing enzymes with optimal domain structures and binding properties, and with higher specific activity, lower end-product inhibition and higher thermal stability, as well as by optimizing the production processes. The cost of the enzymatic hydrolysis is dependent on the efficiency, yield and costs of the pretreatment, synergistic action of cellulases and accessory enzymes, as well as on the needed amount of externally added enzymes. The costs of ethanol production are further affected by the yield, concentration and production rate of ethanol. This work reviews the major bottlenecks in the conversion process, as well as highlights recent approaches to overcome these problems.

Methane production from solid-state anaerobic digestion of lignocellulosic biomass.

Abstract: Four lignocellulosic biomass feedstocks including corn stover, wheat straw, yard waste and leaves were evaluated for methane production via solid-state anaerobic digestion (SS-AD). Results showed that the highest methane yield was attained for corn stover (81.2 L kg−1 volatile solids (VS)), followed by wheat straw (66.9 L kg−1 VS), leaves (55.4 L kg−1 VS) and yard waste (40.8 L kg−1 VS) at a substrate to inoculum (S/I) ratio of 2. The methane production during SS-AD of tested lignocellulosic biomass followed the first-order kinetics model with correlation coefficients (r2) of 0.91–0.98. The main contributor to methane production during SS-AD of corn stover and wheat straw was the degradation of cellulose and hemicellulose while the degradation of extractives was more predominant in yard waste and leaves. An inverse linear relationship was obtained between the methane yield and the lignin content and a positive linear relationship was found between the methane yield and the enzymatic digestibility of the lignocellulosic biomass.

Factors affecting ethanol fermentation using Saccharomyces cerevisiae BY4742

Abstract: Fermentation of sugar by Saccharomyces cerevisiae BY4742, for production of ethanol in a batch experiment was conducted to improve the performance of the fermentation process. The thermotolerant ability of S. cerevisiae to grow and ferment glucose at elevated temperatures similar to the optima for saccharification was investigated. The influences of temperature, substrate concentration and pH on ethanol fermentation were observed. The yield for ethanol production and changes in the fermentation pathway were compared under different conditions. When the temperature was increased to 45 °C, the system still showed high cell growth and ethanol production rates, while it was inhibited at 50 °C. The maximum specific growth rate and the maximum specific ethanol production rate were observed between 30 and 45 °C with different initial glucose concentrations. The maximum sugar conversion at 30 °C after 72 h incubation was 48.0%, 59.9%, 28.3%, 13.7% and 3.7% for 20, 40, 80, 160 and 300 kg m⁻³ of glucose concentrations respectively. Increased substrate supply did not improve the specific ethanol production rate when the pH value was not controlled. pH 4.0–5.0 was the optimal range for the ethanol production process. The highest specific ethanol production rate for all the batch experiments was achieved at pH5.0 which is 410 g kg⁻¹ h⁻¹ of suspended solids (SS) which gave an ethanol conversion efficiency of 61.93%. The highest specific ethanol production rate at 4.0 was 310 g kg⁻¹ h⁻¹ of SS. A change in the main fermentation pathway was observed with various pH ranges. Formation of acetic acid was increased when the pH was below 4.0, while butyric acid was produced when the pH was higher than 5.0. In the presence of oxygen, the ethanol could be utilized by the yeast as the carbon source after other nutrients became depleted, this could not occur however under anaerobic conditions.

Inbicon makes lignocellulosic ethanol a commercial reality

Abstract: Based on the IBUS process, Inbicon has built an advanced biorefinery at the port of Kalundborg in Denmark. In this biorefinery Danish wheat straw is converted to second generation (2G) ethanol, lignin pellets and C5 molasses. It is a demonstration plant working 24 h 7 days a week. In this way it is working as a commercial plant, but the size of the plant is not large enough to carry out a feasible production. It is possible to run as a commercial plant as the Danish Energy Agency has granted the design and construction phase and the European Commission's 7th Framework Programme for Energy Research (FP7) has granted the commissioning and first three years of operation. By the end of 2010 the demonstration plant has been totally commissioned and has gone into production phase. The first 2G ethanol has been sold to Statoil and is now distributed in 100 filling stations all over Denmark as Bio95 2G petrol. Lignin pellets are sold to DONG Energy and used as a high-quality solid biofuel in power plants. The C5 molasses is sold as biogas booster in local biogas plants. The demonstration plant has proved continuous operation from straw bales to fermentation and the expected yield of 2G ethanol (>198 L t −1 dry straw). The process is developed, the products are on the market, lignocellulosic ethanol is reality - but in the same way as for almost any other new energy technologies, further policy and market incentives are still needed before investors will construct the first full scale commercial plants.

Pore characteristics of activated carbons from the phosphoric acid chemical activation of cotton stalks

Abstract: Activated carbons were prepared by phosphoric acid activation of cotton stalks in a nitrogen atmosphere at various temperatures in the 500–800 °C range and at different H 3 PO 4 acid to cotton stalk impregnation ratios (0.3–3). In addition pyrolysis was undertaken in a thermogravimetric analyser in the presence of different ratios of phosphoric acid in order to establish the nature of the biomass to carbon transformations involved. It was established that the total activation process of H 3 PO 4 -impregnated cotton stalks occurred in four stages with the main degradation at 740 °C, compared with 330 °C for raw cotton stalks. The effects of impregnation ratio and activation temperature on the yield and adsorption capacities of activated carbon were evaluated. The chemical composition of the carbons was investigated by elemental analysis and infrared spectroscopy. The impregnation ratio and activation temperature show a strong influence on the yields and the porous texture of the resultant activated carbons. It was demonstrated that increasing impregnation ratio favours the development of mesopores especially at high activation temperature. The activated carbons showed BET surface areas ranging from 330 to 1720 m 2 g −1 , total pore volumes of 0.15–1.23 cm 3 g −1 with mesopore volumes between 0 and 0.61 cm 3 g −1 . Results suggest the practical feasibility of phosphoric acid activation of cotton stalks, which produces high quality activated carbons with high fractions of micropores and mesopores.

Nutrient requirements of Miscanthus x giganteus: Conclusions from a review of published studies

Abstract: Miscanthus x giganteus is a perennial biomass crop particularly suited to substituting fossil fuel resources in bioenergy production, in order to reduce greenhouse gas (GHG) emissions. The area of miscanthus grown in the EU is likely to increase in the future. However, the exact nutrient and fertiliser requirements of the crop are still under debate, which leads to uncertainties when making global assessments of GHG reductions and economics. The aim of our study was to review and analyse published data, in order to determine a consensus view on the nutrient requirements of the crop, and to identify where further research is needed. The findings of this study highlight the nutrient requirements of miscanthus are low compared to other crops. This is due to: i) high nutrient absorption efficiency through extensive rooting, ii) high absorbed nutrient use efficiency, iii) significant nutrient cycling between the rhizome and aerial biomass, iv) nutrient recycling before harvest through leaf fall, and v) possible contribution of N fixation by bacteria. Due to the low yield in the establishment phase of the crop, it is not recommended to apply any fertiliser during the two first years after planting, unless planted on poor soils. From the third year, typically 4.9, 0.45 and 7.0, grams per kilogram of dry matter, of N, P and K respectively are removed at harvest, and this should be a maximum to be replaced by fertilisers. Uncertainties in the exact requirements are due i) to a lack of data, in the different studies, on the nitrogen provided by soils, ii) to a lack of knowledge on the actual contribution of the rhizome to the plant nutrition, and iii) to the inexistence of tools for the diagnosis of the plant N status.

Thermal pretreatment to improve methane production of Scenedesmus biomass

Abstract: Research into the development of renewable and sustainable fuels has been a major concern during last decades. Microalgae, as a potential resource, have gained great attention for energy purposes. In this context, anaerobic digestion seems to be the most direct energy generation process. Nevertheless, the efficiency of this process is hampered due to the hard cell wall of some microalgae. In order to enhance its anaerobic biodegradability, the present research investigated the effect of thermal pretreatment at two temperatures (70 and 90 °C) applied to Scenedesmus biomass. No differences were detected in terms of organic matter or ammonium release upon the two tested temperatures. Nevertheless, a different fact was observed for their anaerobic biodegradability. While raw and pretreated at 70 °C microalgae attained 22–24% anaerobic biodegradability, microalgae pretreated at 90 °C achieved anaerobic biodegradability of 48%. Even though similar profiles were obtained for both temperatures along the pretreatment period, the damage caused in the cell wall at 90 °C seemed to be greater and rendered this substrate readily degradable for anaerobic digestion.

Are we ready to cultivate sweet sorghum as a bioenergy feedstock? A review on field management practices

Abstract: This review discusses the potential production for energy purposes of sweet sorghum (Sorghum bicolor L.), a C4 crop native to tropical areas with juicy stalks rich in sugars from which ethanol could be produced at lower costs than from starchy crops like maize. The growing interest in bioenergy and particularly in bioethanol is a great challenge for this relatively new crop that could be used for both thermo-electrical energy and biofuel. Nonetheless, the quantitative and qualitative production of sweet sorghum strongly depends on the use of appropriate and improved agronomic management techniques which is, in some aspects, still largely unknown. This review attempts to gather the sparse information on best agricultural practices for sweet sorghum, still very much a wild species in many aspects, while identifying the weak points that need to be deepened in further researches, especially under temperate climates. Sweet sorghum is a row crop and therefore the agronomic management and other well known cultural methods used for conventional row crops such as maize can be adapted. In general, low input requirements, low production costs, drought resistance, versatility, and high yields gives to sweet sorghum a better energy balance compared to other competing energy crops, especially if bagasse is also processed to energy. In non-traditional potential growing areas (such as in temperate climates of Europe) where productivity/adaptation improvements through genetically modified crops is not allowed, appropriate and sustainable agricultural practices constitute the most immediate option to improve yields. Based on scientific reports, research efforts seem particularly needed for harvesting techniques, and handling and storing.

Influence of nutrient deprivations on lipid accumulation in a dominant indigenous microalga Chlorella sp., BUM11008: evaluation for biodiesel production.

Abstract: Microalgae are a potential source of biodiesel The urgent need for an alternative and sustainable energy has created renewed interest to analyze the microalgae for biodiesel production In this study, a dominant indigenous freshwater unicellular microalgal strain Chlorella sp, BUM11008 , was examined for its efficiency towards biodiesel production The organism was evaluated for ability to yield high of biomass and lipid productivity under normal and various nutrient-deprived conditions (nitrogen, phosphate-potassium, iron, and all three combined) Under normal conditions, after 20 days of cultivation in Chu10 medium, the organism yielded a biomass of 258 ± 007 g/L, with lipid content of 31216 ± 238 mg/g In a two-phase culturing system upon nutrition deprivation, the organism was able to respond with different levels of lipid accumulation Among the various post-harvest treatments, nitrogen deprivation yielded the highest lipid productivity of 5396 ± 063 mg/L d, followed by the combined deprivation condition (4916 ± 136 mg/L d) FAME profiles of the isolate were found to meet the requirements of international standards for biodiesel The study leads to the conclusion that the two-phase culturing system with nitrogen starvation as post-harvest treatment would be suitable for gaining maximum biomass productivity, and lipid content of high quality fatty acids Thus, it is proposed that Chlorella sp, BUM11008 , would be a promising candidate for sustainable biodiesel production

Large-scale biodiesel production using microalgae biomass of Nannochloropsis.

Abstract: The aim of this study is to investigate the large-scale algae production using Nannochloropsis sp. in indoor open ponds. One of the key factors in open pond productivity is the uniformity of distribution of nutrients and CO2. Therefore, the effects of paddlewheel speeds (1.4, 2.1 and 2.8 rad s � 1 ) on the productivity were also evaluated. The culture system

Evaluation of slagging and fouling tendency during biomass co-firing with coal in a fluidized bed

Abstract: Over the last decades, several indices based on ash chemistry and ash fusibility have been used to predict the ash behaviour during coal combustion, namely, its tendency for slagging and fouling. However, due to the physical–chemical differences between coals and biomass, in this work only the applicability of an ash fusibility index (AFI) to the combustion and co-combustion of three types of biomass (straw pellets, olive cake and wood pellets) with coals was evaluated. The AFI values were compared with the behaviour of ash during combustion in a pilot fluidized bed and a close agreement was observed between them. For a better understanding of the mechanisms associated with bed ash sintering, they were evaluated by SEM/EDS and the elements present on the melted ash were identified. Evidences of different sintering mechanisms were found out for the fruit biomass and herbaceous biomass tested, depending on the relative proportions of problematic elements. The particles deposited on a fouling probe inserted in the FBC were analyzed by XRD and the differences between the compounds identified allowed concluding that the studied biomasses present different tendencies for fouling. Identification of KCl and K 2 SO 4 in the deposits confirmed the higher tendency for fouling of fruit biomass tested rather than wood pellets.

Immobilized lipase on magnetic chitosan microspheres for transesterification of soybean oil

Abstract: Biodiesel fuel, produced by transesterification of vegetable oils or animal fats with methanol, is a promising alternative diesel fuel due to the limited resources of fossil fuels and the environmental concerns. An environmentally benign process for the transesterification reaction using immobilized lipase has attracted considerable attention for biodiesel production. In the work, magnetic chitosan microspheres were prepared by the chemical co-precipitation approach using glutaraldehyde as cross-linking reagent for lipase immobilization. The immobilization of lipase onto the magnetic particles was confirmed by magnetic measurements, transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectra. Using the immobilized lipase, the conversion of soybean oil to fatty acid methyl esters reached 87% under the optimized conditions of methanol/oil amount-of-substance ratio 4:1 with the three-step addition of methanol, reaction temperature 35 °C, and reaction duration 30 h. Moreover, the immobilized lipase could be used for four times without significant decrease of the activity.

Effect of injection pressure and injection timing on DI diesel engine fuelled with biodiesel from waste cooking oil

Abstract: Due to the depleting amount of petroleum reserves and the increasing awareness on environmental concerns, biodiesel has become one of the most demanding and promising substitutes for the petroleum based fossil fuels. In this study, the biodiesel derived from waste cooking oil through the transesterification process was optimized using Response Surface Methodology. The biodiesel derived under optimum conditions was used for investigating the effect of injection pressure and timing on performance, emission and the combustion characteristics of single cylinder, four-stroke direct injection diesel engine at a constant speed of 1500 rpm. On varying the injection pressure and timing, it was found that the combined effect of higher injection pressure of 280 bar and an advanced injection timing of 25.5°bTDC had significant improvement in the brake thermal efficiency, cylinder gas pressure and heat release rate. Reduction in nitric oxide (NO) and smoke emission was also observed.

Estimation of the production cost of fast pyrolysis bio-oil

Abstract: A number of papers and reports covering the techno-economic analysis of bio-oil production has been published. These have had different scopes, use different feedstocks and reflected national cost structures. This paper reviews and compares their cost estimates and the experimental results that underpin them. A comprehensive cost and performance model was produced based on consensus data from the previous studies or stated scenarios where data is not available that reflected UK costs. The model takes account sales of bio-char that is a co-product of pyrolysis and the electricity consumption of the pyrolysis plant and biomass pre-processing plants. It was concluded that it should be able to produce bio-oil in the UK from energy crops for a similar cost as distillate fuel oil. It was also found that there was little difference in the processing cost for woodchips and baled miscanthus.

Extraction and characterization of cellulose microfibrils from agricultural residue – Cocos nucifera L.

Abstract: The aim of this study was to extract cellulose microfibrils from the agricultural residue of coconut palm leaf sheath using chlorination and alkaline extraction process. Chemical characterization of the cellulose microfibrils confirmed that the α-cellulose mass fraction increased from 0.373 kg kg−1 to 0.896 kg kg−1 after application of several treatments including dewaxing, chlorite delignification and alkaline extraction of hemicelluloses. Similarly, the crystallinity index obtained from X-ray diffraction for leaf sheath and extracted cellulose microfibrils was found to be 42.3 and 47.7 respectively. The morphology of the cellulose microfibrils was investigated by scanning electron microscopy. The cellulose microfibrils had diameters in the range of 10–15 μm. Fourier transform infrared and Nuclear magnetic resonance spectroscopy showed that the chemical treatments removed most of the hemicellulose and lignin from the leaf sheath fibers. The thermal stability of the fibers was analyzed using thermogravimetric analysis, which demonstrated that this thermal stability was enhanced noticeably for cellulose microfibrils. This work provides a new approach for more effective utilization of coconut palm leaf sheaths to examine their potential use as pulp and paper and reinforcement fibers in biocomposite applications.

Hydrothermal conversion of lignin compounds. A detailed study of fragmentation and condensation reaction pathways

Abstract: The hydrothermal conversion takes advantage of the singular physico-properties of the hot and compressed water which can be considered as a green solvent. The hydrothermal conversions of an alkali lignin and of phenolic model compounds (vanillin, monobenzone, 2,2′-biphenol) have been studied at 370 and 390 °C, at 25 MPa between 5 and 40 min. Polydispersity of products in term of both chemical structures and molecular weights has been characterized through a new analytical approach combining chromatographic (GC) and spectrometric techniques (Fourier transform ion cyclotron mass spectrometry FT-ICR/MS, NMR). From our experiments, it is clear that lignin conversion occurs via a complex reaction pathway where competitive fragmentation and condensation reactions occur. An original reaction pathway has been suggested from the main emphasized reactions.

Co-composting of the solid fraction of anaerobic digestates, to obtain added-value materials for use in agriculture

Abstract: This work focuses on the viability of composting for the recycling of digestates, to obtain added-value organic materials with potential use in agriculture. Mixtures made from the solid fraction of a digestate (obtained from the anaerobic co-digestion of cattle slurry and silage), with or without vine shoot prunings as bulking agent, were composted by the Rutgers composting system. During composting, the temperature of the composting piles was monitored, as were physico-chemical, chemical, and maturity parameters. Potential added-value properties of the final composts, such as their physical characteristics and in vitro suppression of Fusarium oxysporum f. sp. melonis , were determined. The bulking agent had a positive effect, reducing the electrical conductivity and the N losses during composting and also diluting the heavy metal contents of the end-products. The composts obtained showed adequate degrees of stability and maturity, suitable physical properties for use as growing media, and suppression of F. oxysporum f. sp. melonis .

Changes of chemical and mechanical behavior of torrefied wheat straw

Abstract: The purpose of the study was to investigate the influence of torrefaction on the grindability of wheat straw. Straw samples were torrefied at temperatures between 200 °C and 300 °C and with residence times between 0.5 and 3 h. Spectroscopic information obtained from ATR-FTIR indicated that below 200 °C there was no obvious structural change of the wheat straw. At 200–250 °C hemicelluloses started to decompose and were totally degraded when torrefied at 300 °C for 2 h, while cellulose and lignin began to decompose at about 270–300 °C. Tensile failure strength and strain energy of oven dried wheat straw and torrefied wheat straw showed a clear reduction with increasing torrefaction temperature. In addition, Hardgrove Grindability Index (HGI) of wheat straw torrefied at different conditions was determined on a standard Hardgrove grinder. Both results showed an improvement of grindability in the torrefaction temperature range 250–300 °C, which can be well explained by the findings from FTIR analysis. At a torrefaction temperature of 260 °C and with a residence time of 2 h, wheat straw samples produced similar HGI values as coal (RUKUZN) with 0% moisture content. Under this condition, the Anhydrous Weight Loss (AWL%) of the wheat straw sample was 30% on dry and ash free basis (daf), and the higher heating value of the torrefied wheat straw was 24.2 MJ kg−1 (daf). The energy loss compared to the original material was 15% (daf).

Preparation and characterisation of activated carbon from waste tea using K2CO3

Abstract: Biomasses and their wastes have been used to produce various materials including activated carbons (ACs). The properties of the ACs mostly depend on the production method and the type of the raw material. Waste tea that is a biomass as a precursor was employed to prepare activated carbon (AC) in accordance with the conventional method using potassium carbonate (K2CO3). The effects of various process parameters such as carbonisation temperature and period, impregnation ratio and period on the characteristics of the final product were determined. The ACs were characterised in terms of the BET surface area, the true density, the pore volumes, chemical structure and surface morphology. The maximum surface area of the AC was 1722 m2/g produced at 900 °C and impregnation ratio of 1.0. The pore volumes of the samples were found out according to the Non Local Density Functional Theory (NLDFT) method. To produce the AC with high micropore volume fraction, 800 °C is the best convenient temperature for the experiments performed at impregnation ratios of 1.0, 1.5 and 2.0. The BET surface area and the mesopore volume fractions of the AC were substantially increased at 900 °C. The results showed that both the carbonisation temperature and impregnation ratio noticeably affected the micro and mesopore volumes as well as the BET surface area.

Isolation and purification of lignin and silica from the black liquor generated during the production of bioethanol from rice straw

Abstract: Bioethanol production from lignocellulosic agricultural residues is an attractive future biofuel option from the standpoints of food security and environment friendliness. The safe disposal of the black liquor produced during the process of lignocellulosic ethanol production however remains a challenge. In this study, a method has been developed for the efficient recovery of lignin and silica from black liquor. Rice straw was pre-treated in two different steps, with dilute acid hydrolysis followed by alkaline peroxide delignification. Lignin and silica were isolated from the black liquor by precipitation method using dilute sulphuric acid for reducing the pH of the black liquor. The pH values required for the recovery of lignin and silica were optimised separately. Two different precipitation and separation methods were followed for product recovery from black liquor. Chemical characterisation of isolated lignin was done by FTIR and compared with commercial lignin to evaluate its potential industrial applications. The quality of the filtrate after precipitate separation was also monitored in each step by COD and TDS analyses. Two-stage treatment of black liquor, which involves isolation of silica and lignin separately, was found to provide superior quality products and cleaner effluent than the direct precipitation of lignin without the separation of silica from black liquor.

Availability of protein-derived amino acids as feedstock for the production of bio-based chemicals

Abstract: This review describes different potential sources for amino acids that could be used for the production of bulk chemicals in a biorefinery, such as agricultural byproduct streams. Volumes at which these sources and the amino acids therein are available were determined, and the most interesting amino acids in terms of their potential available quantity were identified. The investigated sources are maize and wheat DDGS, sugarcane vinasse and its leaves, sugar beet vinasse and its leaves, cassava leaves, press cakes of rapeseed, sunflower, soybean, palm oil and Jatropha, animal slaughter waste, microalgae, macroalgae, grass and alfalfa. It can be concluded that there are enough sources available to produce bio-based chemicals such as N-methylpyrrolidone with a market sizes around 100 kt per year from amino acids. Bulk chemicals such as acrylonitrile can partly be replaced in the future by their bio-based equivalent, depending on the amounts of biofuels that will be produced in the future. However, it is still necessary to find cost-effective methods for the isolation of amino acids from the discussed sources.