Article

Miscanthus clones for cellulosic bioethanol production: Relationships between biomass production, biomass production components, and biomass chemical composition

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Abstract

The perennial miscanthus crop is a promising feedstock for cellulosic ethanol production due to its high yield, low input and low environmental impacts. To be suitable for cellulosic ethanol production, cultivated Miscanthus clones need to present not only high aboveground biomass production, but also high cellulose and hemicellulose contents and low lignin, soluble, and ash contents. By testing M. × giganteus, M. sacchariflorus, and M. sinensis clones, we investigated the relationships between biomass production and biomass composition traits at two harvest dates over 3 years. High aboveground biomass production was associated with high canopy height, high stem diameter, late flowering, and high cellulose and lignin contents but low hemicellulose, soluble, and ash contents. The aboveground biomass production was positively correlated with the potential yields of cellulose, hemicelluloses, and lignins. These relationships were consistent throughout the years and the harvest dates. The most productive Miscanthus clones displayed high cellulose contents and low soluble and ash contents; however, they displayed low hemicellulose contents and high lignin contents. The total aboveground biomass composition was closer to the stem composition than to the leaf composition. Nevertheless, the leaves were interesting because of their high hemicellulose and low lignin contents. Lastly, all of the studied factors were significant, but the biomass production traits were mainly affected by the year of cultivation or clone, while the biomass composition traits were mainly affected by the harvest date. All of the traits showed low interaction effects. These results will guide the breeding of Miscanthus clones that are tailored for biofuel production.

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... For these traits, genotype × year interactions have been highlighted in a period covering at least 3 years after implantation. Genotype × location interactions have been evidenced as well: breeding efficiency has been shown to potentially increase if miscanthus genotypes are evaluated in different locations, as some genotypes reached a better biomass yield in one location compared to others [23,[28][29][30][31][32]. Other studies have observed genotype × year and genotype × location interactions while evaluating biomass composition traits, from at least the first to the third year after establishment [31,[33][34][35][36]. ...
... Genotype × location interactions have been evidenced as well: breeding efficiency has been shown to potentially increase if miscanthus genotypes are evaluated in different locations, as some genotypes reached a better biomass yield in one location compared to others [23,[28][29][30][31][32]. Other studies have observed genotype × year and genotype × location interactions while evaluating biomass composition traits, from at least the first to the third year after establishment [31,[33][34][35][36]. ...
... These two parents were purchased in a French nursery for a previous study [24] and their initial provenance was identified to be from central and southern Japan [21,22]. They were then evaluated in the field within a set of 21 miscanthus clones [24,31]. They were selected for their highly contrasted plant stem numbers, and then reciprocally crossed in isolated greenhouses during the fall of 2007, at the INRAE BioEco-Agro research center of Estrées-Mons in Northern France. ...
Article
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Traits for biomass production and composition make Miscanthus a promising bioenergy crop for different bioconversion routes. They need to be considered in miscanthus breeding programs as they are subjected to genetic and genetic × environment factors. The objective was to estimate the genetic parameters of an M. sinensis population grown during 4 years in two French locations. In each location, the experiment was established according to a staggered-start design in order to decompose the year effect into age and climate effects. Linear mixed models were used to estimate genetic variance, genotype × age, genotype × climate interaction variances, and residual variances. Individual plant broad-sense heritability means ranged from 0.42 to 0.62 for biomass production traits and were more heritable than biomass composition traits with means ranging from 0.26 to 0.47. Heritability increased through age for most of the biomass production and composition traits. Low genetic variance along with large genotype × age and genotype × climate interaction variances tended to decrease the heritability of biomass production traits for young plant ages. Most of the production traits showed large interaction variances for age and climate in both locations, while biomass composition traits highlighted large interaction variances due to climate in Orléans. The genetic and phenotypic correlations between biomass production and composition traits were positive, while hemicelluloses were negatively correlated with all traits. Selection is difficult on young plants as the heritability is too low. The joint improvement of biomass production and composition traits would help provide a better response of miscanthus to selection.
... However, cellulose conversion is affected by many factors, mainly the degree of its crystallinity, the content and composition of hemicellulose and lignin, as well as cross-linking between cell wall components (Carpita, 1996;Ralph, 2010;Li et al., 2013;De Souza et al., 2015;Lee and Kuan, 2015). Biomass composition and thus suitability for bioethanol production is a combined effect of genotype, plant age and physiological condition, climate and environment as well as cultivation management (Le Ngoc Huyen et al., 2010;Brosse et al., 2012;Arnoult et al., 2015b;De Souza et al., 2015;Lee and Kuan, 2015;Boakye-Boaten et al., 2016;Belmokhtar et al., 2017;Dubis et al., 2017;van der Weijde et al., 2017). ...
... The yield-building phase of Miscanthus growth is considered to take three years, after which biomass supply is maintained relatively constantly for up to 20 years (Lewandowski et al., 2000;Clifton-Brown et al., 2008;Jeżowski, 2008;Jeżowski et al., 2011;Robson et al., 2013;Arnoult et al., 2015a;McCalmont et al., 2017;Nazli et al., 2018). Established plantations provide feedstock for pelleting, but increasingly they are being examined for biofuel production potential (Le Ngoc Huyen et al., 2010;Han et al., 2011;Brosse et al., 2012;Arnoult et al., 2015b). Our hypothesis was that the three-year yield-building phase was sufficient also for stabilisation of biomass composition and initiation of bioethanol production. ...
... In this study six genotypes of three Miscanthus species were investigated in three-year plot trials as a model for newly established plantations producing biomass as bioethanol feedstock. Although most of the analysed traits varied specifically with genotype, the year played a more significant role and for the larger number of tested traits, similarly to previous reports (Jeżowski et al., 2011;Arnoult et al., 2015b;Belmokhtar et al., 2017). In the aspect of initiation of bioethanol production, the minimal three-year period of cultivation appeared adequate for establishing most biometric, physiological and biochemical characteristics of Miscanthus plants. ...
Article
Production of bioethanol from Miscanthus biomass has been studied for years, yet many important aspects still remain to be evaluated and optimised. It may be assumed that the three-year yield-building phase of Miscanthus growth would be sufficient for stabilisation of biomass composition to provide suitable biomass as a bioethanol feedstock. Such early biomass harvesting could be important for the economics of newly established plantations. This study shows the gradual stabilisation of biomass production by genotypes of M. × giganteus, M. sinensis and M. sacchariflorus within the first three years of cultivation on moderately fertile soil, under the climatic conditions of west-central Poland. Photosynthesis, plant growth, biomass yield, and biochemical and elemental composition, simultaneously stabilised. The tested genotypes differed in their photosynthesis intensity and yield traits. There was little variation in the biochemical composition among genotypes; in comparison to Miscanthus cultivated in a more oceanic climate there was lower cellulose content, but higher lignin content. Aside from basal elements, the tested genotypes varied considerably in their accumulation of most macro- and especially microelements. The three-year old, winter-harvested technical biomass was used for pilot-scale bioethanol production including alkaline delignification and SSF technology. The particular biochemical components and elements in the biomass differently impacted the production process, yet for most genotypes the bioethanol produced was highly correlated with the cellulose:lignin ratio. The highest yield (g/kg DM) and efficiency (%) of raw bioethanol production were recorded for genotypes of M. sinensis (234–253 g/kg DM, 83–86%), followed by M. sacchariflorus (207–237 g/kg DM, 76–81%) and M. × giganteus (185–222 g/kg DM, 62–76%). However, biomass yield had a substantial effect on the estimated bioethanol production. The study pointed to the high potential for raw bioethanol production (4,400-5,600 L/ha) exploiting 3-year Miscanthus plantations, comparably for M. × giganteus and M. sinensis cultivated in a temperate transitional climate.
... Biomass production and cell wall composition have been shown to be highly variable among Miscanthus genotypes (Allison et al., 2011;Arnoult and Brancourt-Hulmel, 2015;Arnoult et al., 2015a;Costa et al., 2016). Moreover, the miscanthus biomass production and composition may be impacted by the environment, particularly by climatic conditions that can differ with harvesting date and year (Le Ngoc Huyen et al., 2010;Arnoult et al., 2015a,b). ...
... Twenty-one Miscanthus genotypes were planted in 2007 in a randomized complete block experimental design with three blocks (for details, see Arnoult et al., 2015a). Among these 21 genotypes, the following five genotypes were studied: two genotypes were identified as M. sinensis (ROT and SIL), and three genotypes were identified as M. × giganteus (FLO, GIB, and H8). ...
... Using Amplified Fragment Length Polymorphism (AFLP) markers, the genotype named "FLO" belonged to the M. × giganteus species (Rambaud, personal communication). These five genotypes were chosen among the 21 previously studied genotypes (Arnoult et al., 2015a) due to (i) their relatively high biomass production per hectare and (ii) their contrasted biomass composition, particularly for cellulose and lignin contents. ...
Article
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HIGHLIGHTSBiomass production and cell wall composition are differentially impacted by harvesting year and genotypes, influencing then cellulose conversion in miniaturized assay. Using a high-throughput miniaturized and semi-automated method for performing the pretreatment and saccharification steps at laboratory scale allows for the assessment of these factors on the biomass potential for producing bioethanol before moving to the industrial scale. The large genetic diversity of the perennial grass miscanthus makes it suitable for producing cellulosic ethanol in biorefineries. The saccharification potential and year variability of five genotypes belonging to Miscanthus × giganteus and Miscanthus sinensis were explored using a miniaturized and semi-automated method, allowing the application of a hot water treatment followed by an enzymatic hydrolysis. The studied genotypes highlighted distinct cellulose conversion yields due to their distinct cell wall compositions. An inter-year comparison revealed significant variations in the biomass productivity and cell wall compositions. Compared to the recalcitrant genotypes, more digestible genotypes contained higher amounts of hemicellulosic carbohydrates and lower amounts of cellulose and lignin. In contrast to hemicellulosic carbohydrates, the relationships analysis between the biomass traits and cellulose conversion clearly showed the same negative effect of cellulose and lignin on cellulose digestion. The miniaturized and semi-automated method we developed was usable at the laboratory scale and was reliable for mimicking the saccharification at the pilot scale using a steam explosion pretreatment and enzymatic hydrolysis. Therefore, this miniaturized method will allow the reliable screening of many genotypes for saccharification potential. These findings provide valuable information and tools for breeders to create genotypes combining high yield, suitable biomass composition, and high saccharification yields.
... The lignocellulosic biomass is being further explored as a main substrate in biorefinery domain [1]. Among the lignocellulosic substrates, miscanthus and sorghum (two C4 fast growing monocots) are interesting options as M. × giganteus can produce high level of aboveground biomass with a low environmental impact [2]. As for sorghum, it has a high biomass yield potential (even under limited water supplies) and it is easy to cultivate and widely adapts to high temperatures, low water supplies, and poor soils [3]. ...
... Positive impacts of alkali pretreatments on anaerobic digestion of various lignocellulosic substrates have been reported. applied alkali at 4 g 100 g TS −1 dose for 24 h at 55 °C to sunflower stalks; the methane potential increased by 26 and 35% with Ca(OH) 2 and NaOH, respectively [20]. Sambusti et al. (2013) applied NaOH pretreatment at 10 g 100 g TS −1 on five sorghum genotypes; the impact on the methane yields ranged from 0 to 7% of increase [25]. ...
... Miscanthus × giganteus Floridulus was grown in the INRA experimental unit located in Estrées-Mons in the North of France (49°53 N, 3°00 E) and harvested in 2018 in its 12th year at the end of winter at over-maturity [2]. Sorghum bicolor L. Moench Biomass 140 hybrid was grown in CIRAD of Montpellier (43°39 N, 3°52 E) located in South of France and harvested in the summer of 2015 at the dough grain stage [28]. ...
Article
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Lignocellulosic biomass is hardly degraded during anaerobic digestion. Among a large panel of pretreatments used to improve the biodegradability of this substrate, alkaline pretreatments are recognized as the most efficient to remove lignin and therefore improve the methane production of these substrates. This article uses different histological stains (FASGA, phloroglucinol, Mäule reagent, Congo red), immunolocalization, and histological quantification on pretreated internode stem tissue section in order to decipher the mechanism of alkaline pretreatment action (CaO and NaOH) in the anatomical and lignocellulosic matrix scale of Sorghum Biomass 140 hybrid and of Miscanthus × giganteus Floridulus. A significant delignification of all tissues was observed (sclerenchyma, parenchyma, and xylem) except in the epidermis and in the internal part of the perivascular sclerenchyma. The degradation of lignin under the effect of alkaline pretreatment is accompanied by a massive unmasking of cellulose and a reduction of crystalline cellulose. This induced an increase of anaerobic digestion kinetics for both biomass and of methane yield for miscanthus. Miscanthus is rich in G-type lignins located mainly at the level of the perivascular sclerenchyma of the external internode zone which was more degraded by alkalies than the S-type lignin; this may explain the improvement of miscanthus methane potential.
... The first one is breeding strategy to develop miscanthus genotypes suited to anaerobic digestion and leading to high methane potential [1]. A first step of this approach is the investigation of various genotypes considering their biochemical composition and methane potential [12,13]. Indeed, in our previous study, the impact of the genotype on methane potential of sorghum was evaluated at 36% of the phenotypic variability [14]. ...
... They selectively remove or degrade lignin without degrading cellulose and increase porosity and surface area, thereby enhancing enzymatic hydrolysis [21]. Soda pretreatment is the most studied, classical parameters are alkali dose 1-10% (g NaOH g TS −1 ), temperature is around 40-60°C, duration is from 0.5 to few days and solid loading is from 30 to 100 g L −1 [4,12,22,23]. However, sodium presence can be detrimental for both anaerobic microorganisms or for soil quality if digestate is used as fertiliser. ...
... Eight miscanthus genotypes were grown at INRA of Estrées-Mons in North of France (49°53 N, 3°00 E), each one in three blocks [12]: three genotypes belonged to M. × giganteus species (FLO, GID and H8), four belonged to M. sinensis species (GOL, MAL, AUG and H6) and one belonged to M. sacchariflorus [32] (H5) ( Table 1). They were harvested in the eighth year of cultivation in winter (February 2015). ...
Article
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In the context of increasing needs of lignocellulosic biomass for emerging biorefinery, miscanthus is expected to represent a resource for energy production. Regarding biogas production, its potential may be improved either by genotype selection or pretreatment. Eight different miscanthus genotypes belonging to Miscanthus × giganteus (FLO, GID and H8), M. sacchariflorus (GOL, MAL, AUG, H6) and M. sinensis (H5) species were first compared for biomass composition and potential methane. In a second time, alkali pretreatments (NaOH 10 g 100 gTS⁻¹, CaO 10 g 100 gTS⁻¹) were applied at ambient temperature and high solid content, in different conditions of duration and particle size on the genotype FLO presenting the lowest methane potential. The methane potential varied between miscanthus genotypes with values ranging from 166 ± 10 to 202 ± 7 NmLCH4 gVS⁻¹. All of the studied pretreatments increased the methane production up to 55% and reduced Klason lignin and holocellulose contents up to 37%. From this study, NaOH was more efficient than CaO with an increase of the methane production between 24 and 55% and between 19 and 30%, respectively.
... These promising methods make breeding and the best selection of less recalcitrant feedstocks for cellulosic ethanol possible. Biomass production and cell wall composition have been shown to be highly variable among Miscanthus genotypes (Allison et al., 2011;Arnoult and Brancourt-Hulmel, 2015;Arnoult et al., 2015a;Costa et al., 2016). Moreover, the miscanthus biomass production and composition may be impacted by the environment, particularly by climatic conditions that can differ with harvesting date and year (Le NgocHuyen et al., 2010;Arnoult et al., 2015a,b). ...
... Twenty-one Miscanthus genotypes were planted in 2007 in a randomized complete block experimental design with three blocks (for details, seeArnoult et al., 2015a). Among these 21 genotypes, the following five genotypes were studied: two genotypes were identified as M. sinensis (ROT and SIL), and three genotypes were identified as M. × giganteus (FLO, GIB, and H8). ...
... Using Amplified Fragment Length Polymorphism (AFLP) markers, the genotype named " FLO " belonged to the M. × giganteus species (Rambaud, personal communication). These five genotypes were chosen among the 21 previously studied genotypes (Arnoult et al., 2015a) due to (i) their relatively high biomass production per hectare and (ii) their contrasted biomass composition, particularly for cellulose and lignin contents. ...
Conference Paper
Miscanthus giganteus is perennial rhizomatous and herbaceous energy crop that gives rise to great biomass yields. However, efficient enzymatic saccharification of cellulose is hindered by many physicochemical, structural, and compositional features. Grass cell walls are characterized by the presence of hydroxycinnamic acids that play a significant role in cross-linking wall polymers into a cohesive network. Notably, ferulic acid is reported to cross-link hemicellulose and lignin whereas p-coumaric acid mostly esterifies lignin. Generally speaking lignin and phenolic acids are known to hamper bioconversion of polysaccharides. Pretreatments are thus required to overcome the recalcitrance of this lignocellulosic network. In the scope of a better identification of the main limiting factors to saccharification we have compared the effect of dilute acid and ammonium hydroxide pretreatments on the efficiency of a cellulase cocktail produced by Trichoderma reesei on small fragments isolated from miscanthus. To this end, the cell wall phenolic component was addressed at the cell level. Following a 144h enzyme incubation of untreated plant specimen, no alteration of the tissues was evidenced in contrast to acid or alkali pretreated samples. Detailed investigation of lignin and phenolic acids distribution in individual secondary cell walls of epidermic and vascular sclerenchyma, vessels and parenchyma was assessed using UV micro spectrophotometry.UV absorbance spectra of untreated substrates shows distinct distribution of phenolics components which are reduced after pretreatment. The heterogeneity of phenolic composition according to the cell types may impacts on the efficiency of pretreatments aiming at improving lignocellulose saccharification.
... Due to the tolerance of varying ecological conditions, Miscanthus has been getting also popular in colder European climates (Monti et al., 2015;Parajuli et al., 2015). Today, Miscanthus is a widely used energy crop (Ameline et al., 2015), and a resource for fine chemicals (Arnoult et al., 2015;Kim et al., 2015). With a cultivation area in Europe of 38,300 ha (Iqbal and Lewandowski, 2016), the thickstemmed nodal woody Miscanthus (Xue et al., 2015), with a dry mass yield of up to 40 t/ha (Lewandowski et al., 2003;Monti et al., 2015), could be a highly attractive resource in particleboard production. ...
... Hemicellulose, lignin and cellulose contents need to be considered with respect to seasonal fluctuations taking place in Miscanthus. Arnoult et al. (2015) found higher amount of cellulose, hemicellulose and lignin in Miscanthus harvested in winter season, compared to those harvested in autumn. The practical meaning is that particleboards produced from winter-harvested Miscanthus may show different mechanical properties. ...
Article
Miscanthus x giganteus stalks were studied as a possible replacement for wood in particleboards. Produced particles from Miscanthus contained 38% of cellulose, and 17% of lignin, while spruce had 45% cellulose, and 28% lignin. The amount of hemicelluloses was the same for both, spruce and Miscanthus (21%). Miscanthus-made particleboards were produced at two levels of methylene diphenyl diioscyanate resination, i.e. 4% and 6%. Modulus of rupture (MOR), modulus of elasticity (MOE), internal bonding strength (IB), thickness swelling and water absorption were measured. Mechanical properties of the Miscanthus-made particleboards were overall reduced: compared to spruce, MOR and MOE were down by 30%, while IB was lowered by 60%. Microscopic analysis of fracture surfaces of the Miscanthus-made particleboards after IB testing showed collapsed cells regions in the soft parenchyma, with no obvious adhesive failures. In contrast, spruce-made particleboards revealed much smoother fracture surfaces with structural failures running through cell walls and possibly also through gluelines. The collapsed parenchyma cell regions suggest a direct link to the reduced mechanical properties. Further, compared to spruce the Miscanthus-made particleboards have shown higher thickness swelling, but lower water absorption. For Miscanthus, no effects of higher MDI adhesive dosages on MOE, MOR and IB were observed. To further improve properties of Miscanthus-made particleboards, at sorting-out of parenchyma tissue components to the highest degree possible is recommended, prior to hot-pressing.
... In particular, substances soluble in cold and hot water, were much more abundant, but the contents of other extractives were also significantly higher in switchgrass. Our results are comparable with data from previous reports, mostly regarding miscanthus and switchgrass coming from the transitional or continental climate [19,32,34,36,38,40]. ...
... [18,35]. However, most authors reported higher ash contents, showing a considerable effect of growing conditions, including year of cultivation, location, type of soil or fertilization [18,33,35,[37][38][39][40][42][43][44]. In this study, the biomass of M. sacchariflorus and switchgrass contained significantly lower amounts of ash than the other miscanthus species. ...
Article
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Lignocellulosic biomass, including that of energy crops, can be an alternative source to produce activated carbons (ACs). Miscanthus and switchgrass straw were used to produce ACs in a two-step process. Crushed plant material was carbonized at 600 °C and then obtained carbon was activated using NaOH or KOH at 750 °C. The content of surface oxygen groups was determined using Boehm’s method. The porosity of ACs was assayed using the nitrogen adsorption/desorption technique, while their thermal resistance using the thermogravimetric method. The ACs derived from miscanthus and switchgrass were characterized by surfaces rich in chemical groups and a highly developed porous structure. The highest specific surface areas, over 1600 m2/g, were obtained after carbon treatment with NaOH. High values of iodine number, 1200–1240 mg/g, indicate an extensive system of micropores and their good adsorption properties. The type of activator affected the contents of oxygen functional groups and some porosity parameters as well as thermal stability ranges of the ACs. Among obtained carbons, the highest quality was found for these derived from M. sacchariflorus followed by switchgrass, after activation with NaOH. Hence, while these crop species are not as effective biomass sources as other energy grasses, they can become valuable feedstocks for ACs.
... This low methane potential is most certainly linked to the high lignin content of the Floridulus clone [27]. Alkaline pretreatment may therefore be relevant for improving methane production from this clone. ...
... Miscanthus. x giganteus Floridulus was grown in the North of France (49 • 53 N, 3 • 00 E) [27] at the INRA experimental unit of Estrées-Mons and harvested in winter 2015 during its eighth year. The soil is a deep loam soil (Orthic Luvisol, Roma, Italia, FAO classification). ...
Article
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In Europe, the agricultural biogas sector is currently undergoing fast developments, and cattle manure constitutes an important feedstock. Batch dry digester processes with leachate recirculation prove to be particularly interesting for small-scale plants. However, their startup being relatively slow, the process could be facilitated by co-digestion with energy crops. In this study, Miscanthus xgiganteus was chosen for its high biomass yields and low input requirements. The carbohydrate accessibility of this lignocellulosic biomass is limited but may be improved with alkali pretreatment. The efficiency of lime (CaO) pretreatment with low water addition on the biochemical methane potential (BMP) of miscanthus was investigated through two experimental designs (CaO concentrations ranged between 2.5 and 17.5% and pretreatment lasted 1, 3, or 5 days). The pretreated miscanthus was then co-digested with cattle manure in dry leach bed reactors. CaO pretreatments led to a 14–37% improvement of miscanthus BMP, and a 67–227% increase in the first-order kinetics constant; a high contact time was shown to favor methane production. According to these results and to industrial requirements, miscanthus was pretreated with 5 and 10% CaO for 5 days, then co-digested with manure in dry leach bed reactors. Nevertheless, the promising results of the BMP tests were not validated. This could be related to the high water absorption capacity of miscanthus.
... The dried samples were then ground in a Wiley mill to a fine Y. Wang, et al. Industrial Crops & Products xxx (xxxx) xxxx powder to pass through a 0.4-mm screen, as recommended for subsequent biomass composition analysis by Arnoult et al. (2015). The cellulose, hemicellulose, and lignin contents of each dried powder sample were performed as previously described by Li et al. (2018). ...
Article
Sweet sorghum (Sorghum bicolor (L.) Moench) is globally evaluated as a key feedstock for bioethanol production due to its high biomass yield. In the present study, the stem biomass characteristics of the sweet sorghum Yajin 1 were revealed and compared with the grain sorghum Aikang 8 at different growth stages. Dynamic analysis of lignocellulosic composition in stems of Yajin 1 and Aikang 8 showed that cellulose content increased and lignin content decreased in the sweet sorghum over development and thus led to a higher saccharification efficiency, which was opposite in the grain sorghum. These varied biomass-associated traits were suggested to be related to changes of bioactive gibberellins GA1 and GA4 levels in young leaves and stems at different growth stages. To investigate the role of gibberellin (GA) metabolism involved in the regulation of stem biomass accumulation and composition in sorghums, a large scale spatio-temporal expression analysis was carried out on the 9 sorghum gibberellin oxidase (SbGAox) genes that encode three classes of key enzymes in the GA biosynthesis. Most of the SbGAox displayed cultivar-, organ-, or stage-preferential expression patterns. Among them, SbGA20ox1 was more specifically expressed in the stem of the sweet sorghum, which was positively related to the stem biomass accumulation and composition, and bioactive GA levels. SbGA2ox1 was more specifically expressed in the grain sorghum than in the sweet sorghum, which was negatively related to the stem biomass accumulation and composition, and bioactive GA levels. As such, these two SbGAox genes may play opposite regulating roles in sorghum stem biomass accumulation and composition by controlling the bioactive GA levels. This study provides a comprehensive understanding of the SbGAox gene family in sorghums, offering a valuable resource to develop strategies for genetic improvement of sorghum biomass traits.
... The mineral content can be 2-to 4-fold higher in leaves than that in stems depending on the maturity [64,80]. As leaves count for about one third of the above ground biomass [79], the loss of leaves during winter will shift the composition of the total aboveground biomass [81]. ...
... Giganteus was thus higher yielding compared to Goliath in Flanders, which is consistent with the findings of Larsen et al. (2013) for Denmark. The higher chilling tolerance of Giganteus is unlikely to be the only factor of its higher yield, as the genotypes also differ in their morphology: Giganteus has taller and thicker stems, which is another factor correlated with the high yield in Miscanthus (Zub et al. 2012a, Robson et al. 2013a, Arnoult et al. 2015. Moreover, the end of Goliath's growing season occurred earlier because it flowered earlier than Giganteus, which had not even flowered every year under Flemish growth conditions. ...
Article
A long growing season, mediated by the ability to grow at low temperatures early in the season, can result in higher yields in the biomass crop Miscanthus. In this paper, the chilling tolerance of two highly productive Miscanthus genotypes, the widely planted Miscanthus × giganteus and the Miscanthus sinensis genotype “Goliath”, was studied. Measurements in the field as well as under controlled conditions were combined with the main purpose to create basic comparison tools to investigate chilling tolerance in Miscanthus in relation to field performance. Under field conditions, M. × giganteus was higher yielding and had a faster growth rate early in the growing season. Correspondingly, M. × giganteus displayed a less drastic reduction of the leaf elongation rate and of net photosynthesis under continuous chilling stress conditions in the growth chamber. This was accompanied by higher photochemical quenching and lower nonphotochemical quenching in M. × giganteus than that in M. sinensis “Goliath” when exposed to chilling temperatures. No evidence of impairment of stomatal conduction or increased use of alternative electron sinks was observed under chilling stress. Soluble sugar content markedly increased in both genotypes when grown at 12°C compared to 20°C. The concentration of raffinose showed the largest relative increase at 12°C, possibly serving as a protection against chilling stress. Overall both genotypes showed high chilling tolerance for C4 plants, but M. × giganteus performed better than M. sinensis “Goliath”. This was not due to its capacity to resume growth earlier in the season but rather due to a higher growth rate and higher photosynthetic efficiency at low temperatures.
... Perennial grasses have been evaluated for cellulosic ethanol production (Arnoult et al., 2015;Digman et al., 2010;Menegol et al., 2016). Among the thermochemical technologies, pyrolysis has been widely used for converting biomass into combustible gas, bio-oil and char. ...
Article
The influence of process conditions (rotary speed/temperature) on the performance of a rotary kiln reactor for non-catalytic pyrolysis of a perennial grass (elephant grass) was investigated. The product yields, the production of non-condensable gases as well as the biochar properties were evaluated. The maximum H2 yield was close to that observed for catalytic pyrolysis processes, while the bio-oil yield was higher than reported for pyrolysis of other biomass in rotary kiln reactors. A H2/CO ratio suitable for Fischer-Tropsch synthesis (FTS) was obtained. The biochars presented an alkaline pH (above 10) and interesting contents of nutrients, as well as low electrical conductivity, indicating a high potential as soil amendment.
... IL10 was thus higher yielding compared to IL11 at our location, which is consistent with the findings of Larsen et al. (2013) for Denmark. The higher chilling tolerance of IL10 is unlikely to be the only factor of its higher yield, as the genotypes also differ in their morphology: IL10 has taller and thicker stems, which is another factor correlated with the high yield in Miscanthus (Zub et al. 2012a, Robson et al. 2013a, Arnoult et al. 2015. Moreover, the end of IL11's growing season occurred earlier because it flowered earlier than IL10, which had not even flowered every year under Flemish growth conditions. ...
Chapter
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Miscanthus is a perennial grass used as a low input biomass crop. Yield limitations are caused mainly by abiotic stresses such as cold, drought, and salinity. This review summarizes the current knowledge of the cold tolerance of miscanthus. Miscanthus has a relatively high cold tolerance compared to related C4 crops such as maize, sorghum, or sugarcane. M. × giganteus, the most commonly planted clone, has a high chilling tolerance compared to most other miscanthus genotypes tested thus far. A small number of recently reported genotypes with an even higher cold tolerance allow for further breeding improvements. The high rates of photosynthesis at low temperatures of M. × giganteus are not an effect of special protective mechanisms but rather of increased production of photosynthetic enzymes. M. × giganteus is relatively susceptible to frost damage in its rhizomes as well as its aboveground parts. Developing improved miscanthus varieties with increased cold tolerance could result in earlier canopy formation and a longer growing season resulting in larger biomass accumulation over the year and higher yields. Increased cold tolerance would allow to expand the miscanthus growing area and to reduce the risk of winter mortality.
... IL10 was thus higher yielding compared to IL11 at our location, which is consistent with the findings of Larsen et al. (2013) for Denmark. The higher chilling tolerance of IL10 is unlikely to be the only factor of its higher yield, as the genotypes also differ in their morphology: IL10 has taller and thicker stems, which is another factor correlated with the high yield in Miscanthus (Zub et al. 2012a, Robson et al. 2013a, Arnoult et al. 2015. Moreover, the end of IL11's growing season occurred earlier because it flowered earlier than IL10, which had not even flowered every year under Flemish growth conditions. ...
Thesis
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Miscanthus is a genus of perennial C4 grasses originating in East Asia. M. x giganteus, a sterile triploid hybrid between M. sinensis and M. sacchariflorus, is increasingly used as a biomass crop. In this thesis the species is referred to as `Miscanthus`, while the crop is referred to as `miscanthus`. The biomass produced by miscanthus can be used for numerous purposes, for example as burning fuel for heating, feedstock for second generation bio-ethanol, mulch, bedding in stables or in construction materials. M. x giganteus is able to produce high biomass yields in comparison to other biomass crops and this for only limited inputs of fertilizers, pesticides and labor. It is a robust crop, ideally suited for marginal lands. It can be easily harvested using widely available harvest machinery and generally does not need drying after harvest. However, due to the sterility of M. x giganteus it has to be propagated vegetatively, either using rhizome cuttings or in vitro propagated plantlets. Both methods are expensive and put a limit on the uptake of the crop by farmers. Currently, breeders are developing new, seed based varieties of miscanthus that will bring down establishment costs drastically and will allow farmers to choose varieties better suited to local conditions. Ideally, these new varieties will be as high or even higher yielding than M. x giganteus. The main limits to miscanthus biomass yield are abiotic stresses such as low temperatures (frost and chilling), drought or salinity. This thesis focuses on the tolerance of miscanthus to frost and chilling stress. These stresses limit miscanthus yield in different ways. Frost damage, for example, has been reported to be the main cause of winter mortality in M. x giganteus in the first year after planting. Developing varieties that can withstand lower temperatures in winter would allow expanding the potential miscanthus growing area to colder regions, for example Eastern and Northern Europe, regions were more marginal land is available. Frost damage can also kill above ground plant parts in early spring, causing the death of young plants or decreased biomass yield in older plantations. Tolerance to chilling stress is essential in developing early emerging varieties with a strong early-season growth and an early canopy formation. Varieties that are able to grow faster at low temperatures and develop a canopy earlier in the growing season would be able to intercept more solar radiation throughout the year and could theoretically produce more biomass than M. x giganteus. The general aims of the research in this thesis were to study the variation in frost tolerance, chilling tolerance and early-season growth in miscanthus, to determine the underlying physiological and biochemical mechanisms and to establish the relationship between early-season growth and final biomass yield. Compared to related C4 crops, such as maize, sugarcane or sorghum, miscanthus tends to be relatively cold tolerant and has been subject of several studies, most of which compared M. x giganteus with maize. These studies have shown that, while maize has higher maximum photosynthetic rate, M. x giganteus is able to photosynthesize at lower temperatures, and this, combined with a longer growing season results in higher yields of M. x giganteus compared to maize. While maize under chilling stress displays a reduction in the activity of photosynthetic enzymes, M. x giganteus has been reported to show an increase in the activity and RNA expression of photosynthetic enzymes when exposed to chilling stress. It is thought that this higher expression counteracts the lower enzyme kinetics at lower temperatures, allowing M. x giganteus to maintain its higher photosynthetic rates. Although a couple of studies have compared different miscanthus genotypes under chilling stress in growth chamber experiments, to date little is known about the underlying mechanisms that distinguish genotypes differing in chilling tolerance and about the variation in chilling tolerance and early-season growth under field conditions. We obtained, through the OPTIMISC EUFP7 project, a collection of over 100 miscanthus genotypes, comprising of M. sinensis, M. sacchariflorus, M. sinensis x sacchariflorus and M. x giganteus accessions. These genotypes were evaluated and compared in growth chamber experiments and in field trials. Additional data was obtained from trials already established at ILVO before the start of the project and from other trials in the OPTIMISC project. In order to screen the variation in rhizome frost tolerance available in the germplasm collection, we determined the temperature at which 50% of the rhizomes were killed (LT50) in 95 miscanthus genotypes. The LT50 in the collection ranged between −0.4 and −5.9°C, while the average LT50 for M. x giganteus was −2.6 ± 0.3°C. On average LT50 was −3.5 ± 0.1°C in M. sinensis, −2.6 ± 0.3°C in M. sacchariflorus and −3.9 ± 0.2°C in the M. sinensis x sacchariflorus hybrids. Rhizome frost tolerance was correlated to the timing of flowering and senescence but not to rhizome moisture content. Wide variation in shoot damage was observed in field-grown plants after a cold spell in early spring. Determination of apex height indicated that the shoot apex was probably still below ground when the frost event occurred, explaining the rapid recovery of damaged shoots later on. This study was the largest screening of rhizome and shoot frost tolerance in miscanthus reported to date and demonstrated the availability of frost tolerant genotypes in the miscanthus breeding material, potentially supporting the development of new frost tolerant varieties. To investigate the variation available for chilling tolerance, we first investigated two highly productive miscanthus genotypes, M. x giganteus and the M. sinensis ‘Goliath’. Measurements in the field as well as under controlled conditions were combined to create basic comparison tools in order to investigate chilling tolerance in miscanthus in relation to its field performance. Under field conditions, M. x giganteus was higher yielding and had a faster growth rate early in the growing season. Correspondingly, M. x giganteus displayed a less drastic reduction of the leaf elongation rate and of net photosynthesis under continuous chilling stress conditions in the growth chamber. This was accompanied by higher photochemical quenching and lower non-photochemical quenching in M. x giganteus than that in M. sinensis ‘Goliath’ when exposed to chilling temperatures. Soluble sugar content markedly increased in both genotypes when grown at 12°C compared to 20°C. The results showed that while growth chamber screening might be useful to distinguish chilling tolerance, validation in field trials is necessary because of the variable conditions in the field. Using the variation in early-season growth in the germplasm collection using a common garden experiment in Belgium during two seasons, and compared these results to those obtained under controlled conditions at low temperature and to observations of early-season growth in the OPTIMISC multi-location field trial in six locations across Europe and Turkey. A large variation in early-season growth was observed among the genotypes in both seasons, with strong between-year correlation for most parameters investigated. Several genotypes, both M. sinensis, M. sacchariflorus as well as M. sinensis x sacchariflorus hybrids displayed stronger early-season growth than M. x giganteus. The observations in the multi-location trial showed a strong genotype by environment interaction indicating that locally adapted genotypes are necessary in order to maximally take advantage of an extended growing season. The substantial variation in early-season growth parameters indicates that selecting for early emergence and chilling tolerance should be possible. Shoot length based traits evaluated in a field trial were most consistent between years and appear well suited to screen large germplasm collections for early-season growth. The chilling tolerance of M. x giganteus has been predominantly studied under controlled conditions and our understanding of the underlying mechanisms contributing to chilling tolerance in the field and their variation in different miscanthus genotypes remains largely unexplored. To address these questions, we selected five miscanthus genotypes which varied chilling sensitivity and scored a comprehensive set of physiological traits throughout the spring season. Chlorophyll fluorescence was measured as indication of photosynthesis and leaf samples were analyzed for biochemical traits related to photosynthetic activity (chlorophyll content and PPDK activity), redox homeostasis (malondialdehyde, glutathione and ascorbate contents, and catalase activity) and water soluble carbohydrates content. The overall physiological response of chilling tolerant genotypes was distinguishable from that of chilling sensitive genotypes, while M. x giganteus was intermediate between both groups. Chilling tolerant genotypes were characterized by higher levels of malondialdehyde, raffinose, sucrose and higher catalase activity while the chilling sensitive genotypes were characterized by higher concentrations of glucose, fructose and higher pyruvate-Pi-dikinase activity later in the growing season. M. x giganteus responses were similar to the tolerant genotypes early in the growing season, but more similar to the chilling sensitive genotypes, which also combined a high biomass yield, later on. Early emergence and early canopy formation theoretically allow plants to intercept more radiation in the long days in spring which would in turn allow them to produce more biomass. Reports in literature are contrasting however and therefore we also studied the relationship between early-season growth and biomass production. We combined the early-season growth measurements with further growth measurements performed throughout the rest of the growing season in order to find the growing season traits that are most strongly related to biomass production. We found that all growing season traits were highly correlated between years. Overall, early-season growth was indeed correlated with higher biomass yield. Breeding new varieties requires a screening of the germplasm for yield potential and other agronomic traits. We therefore investigated the yield potential of our germplasm collection on a miniplots level and report the variation in emergence, flowering and senescence among the genotypes in the trial. We did not observe a relationship between early-season growth and biomass yield in this trial due to the later harvest, which canceled out most differences in early-season growth among the genotypes. We observed a large variation in flowering and senescence in our field trial but no relation between flowering and biomass production was found. Senescence also varied widely among the genotypes. only in the M. sacchariflorus genotypes a relation between later senescence and biomass yield was found. In conclusion we found a large variation in chilling and frost tolerance in the miscanthus germplasm. Genotypes with higher chilling and frost tolerance than M. x giganteus were identified in both M. sinensis and M. sacchariflorus. This large variation and the high heritability of these traits may allow successful breeding for more cold tolerant varieties that will allow the production of miscanthus in areas that are currently too cold for the crop.
... It was also found that higher dosage of lacustrine chalk gave lower growth of plants. Some researchers reported that biomass production traits are mainly influenced by year of cultivation (Arnoult et al., 2015). ...
Chapter
The main aim of this study was to assess the modification in soil organic carbon (SOC) content in different fertilization strategies and changes in its chemical structure using ¹³ C nuclear magnetic resonance spectroscopy technique. The field study was conducted using biosolids: compost from municipal sewage sludge, sewage sludge, lacustrine chalk, and two plants species-pine (Pinus sylvestris L.) for wood biomass and giant miscanthus (Miscanthus giganteus) for green biomass as energy crops. For miscanthus, the biomass production was improved when the abovementioned amendments were used. The biomass yield was much higher on plots with all applied amendments after 1 year growth. For energetic plants with very fast increase in biomass, soil treatments using amendments are reasonable. It was assumed that modification in SOC resulting from different fertilization strategies provides the SOC chemical structure changes. The cultivation of miscanthus for biomass production on degraded soils with the application of wastes and by-products can provide an example of rational management of available resources.
... Yields with up to three times higher than forests are obtained with Giant Miscanthus (Miscanthus x giganteus), demonstrating a biomass production at 44 t·ha -1 ·year -1 (Pyter et al. 2007). Miscanthus is becoming more and more popular in the colder, northern European climates (Monti et al. 2015;Parajuli et al. 2015) as a bioenergy crop (Ameline et al. 2015), or is used as a resource in chemical production (Arnoult et al. 2015;Kim et al. 2015). Higher yields than wood are also demonstrated by cup-plants (Silphium perfolatium L.), reaching 40 t·ha -1 ·year -1 . ...
Conference Paper
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This contribution is a state-of-the-art review and synthesis on alternative materials used for bio-based composites, in particular for particleboards. Basic economical and ecological aspects of wood replacements for particleboards are discussed, and effects of on various mechanical properties are compiled. Synthesis and Ashby plots provide information useful for the optimization of composite materials. Is is shown that alternative materials are available at sufficient volumes, at potentially lower prices, and with benefits such as termite resistance, or reduced swelling rates. However, mechanical properties are mostly lower, when compared to wood-based particleboards. It can be stated, that biobased composites, i.e. particleboards, made from alternative materials, widely show a satisfying overall performance at lower prices.
... It was also found that higher dosage of lacustrine chalk gave lower growth of plants. Some researchers reported that biomass production traits are mainly influenced by year of cultivation (Arnoult et al., 2015). ...
... The plant is productive and frost-resistant. Its biomass is a promising cellulose-containing raw material to be converted to cellulose, biofuels, and bioproducts (Arnoult et al. 2015;Danielewicz et al. 2018;Velásquez et al. 2003). The crop can be used for sewage sludge restoration and soil remediation contaminated with trace elements (Pidlisnyuk et al. 2014). ...
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The organochlorine pesticides (OCPs) have raised concerns about being persistent and toxic to the environment. Phytoremediation techniques show promise for the revitalization of polluted soils. The current study focused on optimizing the phytoremediation potential of Miscanthus sinensis And. (M. sinensis), second-generation energy crop, by exploring two soil amendments: Tween 20 and activated carbon (AC). The results showed that when M. sinensis grew in OCP-polluted soil without amendments to it, the wide range of compounds, i.e., α-HCH, β-HCH, γ-HCH, 2.4-DDD, 4.4-DDE, 4.4-DDD, 4.4-DDT, aldrin, dieldrin, and endrin, was accumulated by the plant. The introduction of soil amendments improved the growth parameters of M. sinensis. The adding of Tween 20 enhanced the absorption and transmigration to aboveground biomass for some OCPs; i.e., for γ-HCH, the increase was by 1.2, for 4.4-DDE by 8.7 times; this effect was due to the reduction of the hydrophobicity which made pesticides more bioavailable for the plant. The adding of AC reduced OCPs absorption by plants, consequently, for γ-HCH by 2.1 times, 4.4-DDD by 20.5 times, 4.4-DDE by 1.4 times, 4.4-DDT by 8 times, α-HCH was not adsorbed at all, and decreased the translocation to the aboveground biomass: for 4.4-DDD by 31 times, 4.4-DDE by 2.8 times, and γ-HCH by 2 times; this effect was due to the decrease in the bioavailability of pesticides. Overall, the amendment of OCP-polluted soil by Tween 20 speeds the remediation process, and incorporation of AC permitted to produce the relatively clean biomass for energy.
... In recent decades, the perception of the necessity to protect the environment has extensively grown, resulting in the development of recyclable and/or biodegradable products from renewable natural resources [1,2]. In this way, lignocellulosic materials are one of the most important natural sources for the production of high added value materials or biopolymers, which are attractive because of their biodegradability, low density and excellent mechanical properties [3,4]. ...
Article
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... sacchariflorus), so-called elephant grass (M. sinesis), as well as Miscanthus M. floridulus and M. lutarioriparius (Iglesias et al. 1996;Arnoult et al. 2015;Qin et al. 2012;Brosse et al. 2012). The agritechnical conditions for the cultivation of Miscanthus 9 giganteus and biomass harvest logistics have been investigated by many authors. ...
Article
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The weight share of the pith, nodes and internodes in the stalks of Miscanthus, as well as the types of cells in these anatomical parts, were examined. Studies have shown that the pith contains mainly parenchyma cells, nodes—short fibres and palisade parenchyma cells, while internodes contains mainly fibres, which are accompanied by a certain amount of vessels and parenchyma cells. Then the whole stalks of Miscanthus were subjected to pulping using the kraft and soda pulping methods. These studies have shown that hard, regular, soft and very soft kraft pulps can be obtained using a lower amount of active alkali, with comparable or higher screened yield of pulp than is the case of pulping of birch. Furthermore, it was found that the content of knots and shives was lower in the digester hard and regular kraft pulps from Miscanthus compared to birch kraft pulp. Of the two pulping methods studied, kraft pulping gives better results than soda pulping concerning the considerably higher yield of pulp. Graphical abstract Open image in new window
... The six quality traits above were used to evaluate FEP. Cellulosic ethanol production requires biomass with high cellulose and hemicellulose contents, but low lignin and ash contents (Arnoult et al., 2015). A high leaf/stem ratio is characterized by the miscanthus germplasm optimal for bioethanol production because the leaves generally display high hemicellulose content and low lignin content (Hodgson et al., 2010b). ...
Article
Biomass is the bioenergy carrier and can be converted to solid, liquid and gaseous fuels. Miscanthus, a plant type with high biomass yield potential, is a promising feedstock source for bioenergy production. However, the current expansion of miscanthus (Miscanthus spp.) production is constrained by a shortage of commercial varieties , especially those suitable for different energy usages and cultivation under adverse environmental conditions. Therefore, breeding or selecting high-biomass-yielding, high quality and stress tolerant miscanthus varieties is essential for the extension of miscanthus for bioenergy production. To effectively select elite germplasms and breed new varieties of miscanthus, it is necessary to establish a scientific evaluation method for analysing their energy potential. In this study, a multi-criteria decision making (MCDM) model was designed to evaluate the potential of miscanthus germplasms as feedstock in four energy usages including combustion for power generation (CPG), pyrolysis for bio-oil production (PBP), fermentation for ethanol production (FEP) and fermentation for biogas production (FBP). The MCDM model was constructed based on 11 sub-criteria indices, which were grouped into agronomic-related and quality-related criteria indices. The agronomic-related criteria indices include dry matter yield, canopy height, stem diameter, tiller number and base diameter/canopy diameter ratio. The quality-related criteria indices include the leaf/stem ratio, moisture content, ash content, cellulose content, hemicellulose content and lignin content. Thirty-eight representative germplasms of miscanthus were evaluated. The MCDM analysis results showed that Miscanthus lutarioriparius (especially the XiangNanDi no. 1 variety) and Miscanthus floridulus (especially A0521) are the best species for CPG/PBP and FEP/FBP, respectively. These results are superior to those calculated by the traditional energy potential assessment method, which showed that Miscanthus floridulus was the most suitable species for CPG, FEP and FBP, especially A0521 and D0624. Moreover, the analysis also indicated that D0505 (M. floridulus) can be used as a suitable parent together with XiangNanDi no. 1 to breed new varieties for CPG and PBP; XiangNanDi no. 1 can be used as an alternative parent for breeding to improve A0521 for use in FEP and FBP.
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Traits for biomass production and composition make Miscanthus a promising bioenergy crop for different bioconversion routes. They need to be considered in miscanthus breeding programs as they are subjected to genetic and genetic x environment factors. The objective was to estimate the genetic parameters of an M. sinensis population grown during four years in two French locations. In each location, the experiment was established according to a staggered-start design in order to decompose the year effect into age and climate effects. Linear Mixed Models were used to estimate genetic variance, genotype x age, genotype x climate interaction variances and residual variances. Individual plant broad-sense heritability means ranged from 0.42 to 0.62 for biomass production traits, and were more heritable than biomass composition traits with means ranging from 0.26 to 0.47. Heritability increased through time for most of the biomass production and composition traits. Low genetic variance along with large genotype x age and genotype x climate interaction variances tended to decrease the heritability of biomass production traits for young plant ages. Most of the production traits showed large interaction variances for age and climate in both locations, while biomass composition traits highlighted large interaction variances due to climate in Orléans. The genetic and phenotypic correlations between biomass production and composition traits were moderate and positive, while hemicelluloses were negatively correlated with all traits. Efficient genetic progress is achievable for miscanthus breeding when plants get older. The joint improvement of biomass production and composition traits would help provide a better response of miscanthus to selection.
Thesis
Dans le contexte du réchauffement climatique et de la diminution des réserves de combustibles fossiles, la biomasse lignocellulosique peut fournir une source renouvelable d'énergie, de matériaux et de produits chimiques. En particulier, la production de biogaz par méthanisation est en plein essor. C’est dans ce contexte de bioraffinerie environnementale que se situe ce projet de thèse. Il porte sur deux biomasses lignocellulosiques différentes : le sorgho et le miscanthus ayant l'avantage de combiner un fort potentiel de production de biomasse avec un impact minimal sur l'environnement. Pour ce type de biomasse, il est bien connu que la lignine joue un rôle de barrière à l’accessibilité des composés. Cette thèse a pour objectif de d’étudier l’impact des pré-traitements alcalins, connus pour délignifier la biomasse de manière efficace et ainsi améliorer son bioaccessibilité et donc sa dégradation par digestion anaérobie. L’étude de l’impact de ces pré-traitements sur la composition biochimique des biomasses et leur production méthane a montré que ces impacts diffèrent en fonction de la biomasse et des conditions opératoires des pré-traitements appliqués (réactif, durée, température, teneur en eau). Dans un objectif d’application de co-digestion en méthanisation agricole, l’impact de certains des prétraitements de ces deux biomasses a été étudié lors d’essais en réacteurs batch à recirculation. Le sorgho s’est révélé être un co-substrat adéquat du fumier. Enfin, l’étude originale des mécanismes d’action de ces pré-traitements à l’échelle de la structure anatomique de la biomasse a montré que les pré-traitements agissent différemment suivant la localisation et le type de lignine. Ces travaux de thèse permettent donc une meilleure compréhension de l’impact des pré-traitements sur différentes biomasses lignocellulosiques.
Article
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The lignocellulosic C4 perennial crop miscanthus and, more particularly, one of its species, Miscanthus × giganteus, are especially interesting for bioenergy production because they combine high biomass production with a low environmental impact. However, few varieties are available, which is risky due to disease susceptibility. Gathering worldwide references, this review shows a high genotypic and environmental variability for traits of interest related to miscanthus biomass production and composition, which may be useful in breeding programs for enhancing the availability of suitable clones for bioenergy production. The M. × giganteus species and certain clones in the Miscanthus sinensis species seem particularly interesting due to high biomass production per hectare. Although the industrial requirements for biomass composition have not been fully defined for the different bioenergy conversion processes, the M. × giganteus and Miscanthus sacchariflorus species, which show high lignin contents, appear more suitable for thermochemical conversion processes. In contrast, the M. sinensis species and certain M. × giganteus clones with low lignin contents were interesting for biochemical conversion processes. The M. sacchariflorus species is also interesting as a progenitor for breeding programs, due to its low ash content, which is suitable for the different bioenergy conversion processes. Moreover, mature miscanthus crops harvested in winter seem preferred by industry to enhance efficiency and reduce the expense of the processes. This investigation on miscanthus can be extrapolated to other monocotyledons and perennial crops, which may be proposed as feedstocks in addition to miscanthus.
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Biomass from dedicated crops is expected to contribute significantly to the replacement of fossil resources. However, sustainable bioenergy cropping systems must provide high biomass production and low environmental impacts. This study aimed at quantifying biomass production, nutrient removal, expected ethanol production, and greenhouse gas (GHG) balance of six bioenergy crops: Miscanthus × giganteus, switchgrass, fescue, alfalfa, triticale, and fiber sorghum. Biomass production and N, P, K balances (input-output) were measured during 4 years in a long-term experiment, which included two nitrogen fertilization treatments. These results were used to calculate a posteriori ‘optimized’ fertilization practices, which would ensure a sustainable production with a nil balance of nutrients. A modified version of the cost/benefit approach proposed by Crutzen et al. (2008), comparing the GHG emissions resulting from N-P-K fertilization of bioenergy crops and the GHG emissions saved by replacing fossil fuel, was applied to these ‘optimized’ situations. Biomass production varied among crops between 10.0 (fescue) and 26.9 t DM ha−1 yr−1 (miscanthus harvested early) and the expected ethanol production between 1.3 (alfalfa) and 6.1 t ha−1 yr−1 (miscanthus harvested early). The cost/benefit ratio ranged from 0.10 (miscanthus harvested late) to 0.71 (fescue); it was closely correlated with the N/C ratio of the harvested biomass, except for alfalfa. The amount of saved CO2 emissions varied from 1.0 (fescue) to 8.6 t CO2eq ha−1 yr−1 (miscanthus harvested early or late). Due to its high biomass production, miscanthus was able to combine a high production of ethanol and a large saving of CO2 emissions. Miscanthus and switchgrass harvested late gave the best compromise between low N-P-K requirements, high GHG saving per unit of biomass, and high productivity per hectare.
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Miscanthus spp. are high-yielding perennial C4 grasses, native to Asia, that are being investigated in Europe as potential biofuels. Production of economically viable solid biofuel must combine high biomass yields with good combustion qualities. Good biomass combustion quality depends on minimizing moisture, ash, K, chloride, N, and S. To this end, field trials at five sites in Europe from Sweden to Portugal were planted with 15 different genotypes including M. x giganteus, M. sacchariflorus, M. sinensis, and newly bred M. sinensis hybrids. Yield and combustion quality at an autumn and a late winter/early spring harvest were determined in the third year after planting when the stands had reached maturity. As expected, delaying the harvest by three to four months improved the combustion quality of all genotypes by reducing ash (from 40 to 25 g kg-1 dry matter), K (from 9 to 4 g kg-1 dry matter), chloride (from 4 to 1 g kg-1 dry matter), N (from 5 to 4 g kg-1 dry matter), and moisture (from 564 to 291 g kg-1 fresh matter). However, the delayed harvest also decreased mean biomass yields from 17 to 14 t ha-1. There is a strong interaction among yield, quality, and site growing conditions. Results show that in northern regions of Europe, M. sinensis hybrids can be recommended for high yields (yielding up to 25 t ha-1), but M. sinensis (nonhybrid) genotypes have higher combustion qualities. In mid- and south Europe, M. x giganteus (yielding up to 38 t ha-1) or specific high-yielding M. sinensis hybrids (yielding up to 41 t ha-1) are more suitable for biofuel production.
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to have exceptionally vigorous growth (Linde-Laursen, 1993). In the late 1980s, interest in C4 perennial rhizoma- Miscanthus is a genus of high-yielding perennial rhizomatous tous grasses, such as Miscanthus spp. (Nielsen, 1987), grasses with C4 photosynthesis. Extensive field trials of Miscanthus spp. biomass production in Europe during the past decade have shown switchgrass (Panicum virgatum L.) (Christian, 1994), several limitations of the most widely planted clone, M. giganteus Cyperus spp., and Spartina spp. (Potter et al., 1995), for Greef et Deu. A 3-yr study was conducted at five sites in Europe biofuel production increased due to their high yield (Sweden, Denmark, England, Germany, and Portugal) to evaluate potential and rising energy prices. Since 1983, extensive adaptation and biomass production potential of four acquisitions of field trials of M. giganteus have been carried out in M. giganteus (No. 1-4) and 11 other genotypes, including M. sac- northern Europe, showing the capacity of this genotype chariflorus (Maxim.) Benth. (No. 5), M. sinensis Andersson (No. for yields 20 t dry matter ha
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In the first side-by-side large-scale trials of these two C(4) crops in the U.S. Corn Belt, Miscanthus (Miscanthus x giganteus) was 59% more productive than grain maize (Zea mays). Total productivity is the product of the total solar radiation incident per unit land area and the efficiencies of light interception (epsilon(i)) and its conversion into aboveground biomass (epsilon(ca)). Averaged over two growing seasons, epsilon(ca) did not differ, but epsilon(i) was 61% higher for Miscanthus, which developed a leaf canopy earlier and maintained it later. The diurnal course of photosynthesis was measured on sunlit and shaded leaves of each species on 26 dates. The daily integral of leaf-level photosynthetic CO(2) uptake differed slightly when integrated across two growing seasons but was up to 60% higher in maize in mid-summer. The average leaf area of Miscanthus was double that of maize, with the result that calculated canopy photosynthesis was 44% higher in Miscanthus, corresponding closely to the biomass differences. To determine the basis of differences in mid-season leaf photosynthesis, light and CO(2) responses were analyzed to determine in vivo biochemical limitations. Maize had a higher maximum velocity of phosphoenolpyruvate carboxylation, velocity of phosphoenolpyruvate regeneration, light saturated rate of photosynthesis, and higher maximum quantum efficiency of CO(2) assimilation. These biochemical differences, however, were more than offset by the larger leaf area and its longer duration in Miscanthus. The results indicate that the full potential of C(4) photosynthetic productivity is not achieved by modern temperate maize cultivars.
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DNA sequences were used to assess the monophyly and inter-relationships of Miscanthus, Saccharum and related genera in the Saccharum complex. Three DNA regions were sequenced, including the trnL intron and the trnL-F intergenic spacer of the plastid genome and the ITS region of nuclear ribosomal DNA (nrDNA). Because it was more variable, the ITS region proved most suitable for phylogenetic reconstruction at this level, and the results indicate that Miscanthus s.l. and Saccharum s.l. are polyphyletic. A set of species from Saccharum section Ripidium (clade a) do not group closely with any members of Saccharum s.l.. A number of Miscanthus species from eastern or south-eastern Asia represent a monophyletic group with a basic chromosome number of 19 (clade b), but the other species from Africa and the Himalayas are clearly excluded. There is support for a monophyletic Saccharum s.s. clade including S. officinarum and S. spontaneum that is sister to Miscanthus s.s (clade c). There is no evidence to support the division of some Saccharum s.l. into the genera currently known as Erianthus and Narenga. Saccharum contortum (=Erianthus contortus), S. narenga (=Narenga porphyrocoma) and Erianthus rockii, group more closely with Miscanthus fuscus, a species from the Himalayas and also with the African Miscanthus s.l. species (=Miscanthidium, clade d).
A rapid procedure for determining cellwall constituents of plants consists of the determination of the fiber insoluble in neutral detergent and is applicable to all feedstuffs. The standardization of the method is based on a nutritional concept which defines fiber as insoluble vegetable matter which is indigestible by proteolytic and diastatic enzymes and which cannot be utilized except by microbial fermentation in the digestive tracts of animals.
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Long-term yield studies in perennial crops like miscanthus are important to determine mean annual energy yield and the farmer’s economy. In two Danish field trials, annual yield of two miscanthus genotypes was followed over a 20-year period. The trials were established in 1993 on loamy sand in Foulum and on coarse sand in Jyndevad. Effects of genotype, row distance and fertilization were investigated. In both trials, yield development over time was characterized by an increase during the first years, optimum yields after 7–8 years and a decrease to a lower level which remained relatively constant from year 11 to 20. Spring harvest reduced the yield by 34–42 % compared to autumn harvest. In Foulum annual fertilization with 75 kg ha−1 N increased the yield of the genotype Goliath (Miscanthus sinensis) by 26 %. Additional N fertilization only increased the yield of Goliath little, and the genotype Giganteus (Miscanthus × giganteus) did not respond to fertilization at all. The highest mean yield in Foulum for the period 1997–2012 was obtained with the shortest row distance (∼18,000 rather than ∼12,000 plants ha−1) and harvested in late autumn, namely 13.1 and 12.0 Mg ha−1 DM annually for Giganteus and Goliath, respectively. In Jyndevad, where only Goliath was studied, the highest yield during 1995–2001 was obtained by short row distance, autumn harvest and annual fertilization with 75 kg ha−1 N, with yield increasing up to 116 % in response to fertilization. A mean yield of 14.4 Mg ha−1 DM was achieved over the period 1995–2012.
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Switchgrass (Panicum virgatum L.) is a C4 grass with high biomass yield potential and is now a model species for the Bioenergy Feedstock Development Program. Two distinct ecotypes (e.g., upland and lowland) and a range of plant morphotypes (e.g., leafy and stemmy) have been observed in switchgrass. The objective of this study was to determine the influence of ecotype and morphotype on biomass feedstock quality. Leaf and stem tissues of leafy and stemmy morphotypes from both lowland and upland ecotypes were analyzed for key feedstock traits. The leaf : stem ratio of leafy morphotype was more than 40% higher than the stemmy morphotype in both upland and lowland ecotypes. Therefore, the stemmy morphotype has significant advantages over leafy morphotype during harvesting, storage, transportation and finally the feedstock quality. Remarkable differences in feedstock quality and mineral composition were observed in switchgrass genotypes with distinct ecotypic origins and variable plant morphotypes. Lignin, hemicelluloses and cellulose concentrations were higher in stems than in the leaves, while ash content was notably high in leaves. A higher concentration of potassium was found in the stems compared to the leaves. In contrast, calcium was higher and magnesium was generally higher in the leaves compared to stems. The upland genotypes demonstrated considerably higher lignin (14.4%) compared with lowland genotypes (12.4%), while hemicellulose was higher in lowland compared with upland. The stemmy type demonstrated slightly higher lignin compared with leafy types (P < 0.1). Differences between the ecotypes and morphotypes for key quality traits demonstrated the potential for improving feedstock composition of switchgrass through selection in breeding programs.
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To develop the perennial grass Miscanthus x giganteus as a highly productive crop for biomass production, new varieties need to be bred, and more knowledge about its growth behaviour has to be collected. Our aim was to identify an efficient function for assessing and comparing emergence date and canopy height growth (rate, duration, and final maximal height) of 21 clones of Miscanthus in Northern France. Flow cytometry made it possible to classify the clones into three clusters corresponding to 2x, 3x, and 4x ploidy levels. Three functions, 3- and 4-parameter logistic functions and Gompertz function, were tested to best describe the dynamics of crop emergence and of plant growth. The best functions were used to estimate emergence dynamics (Gompertz function), and growth dynamics (4-parameter logistic). All these traits showed a significant year, clone, and corresponding interaction effects (but not for harvest date). Species and ploidy level explained the clone and clone × year interaction effects. M. x giganteus and M. floridulus clones were among the latest to emerge, and the tallest. M. sinensis clones showed the lowest height and growth rates. Higher final canopy height was correlated to late emergence and high growth rate. These findings could help early selection of interesting clones within M. sinensis populations, in order to breed new inter-species hybrids of giganteus type.
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Miscanthus sinensis, a C4 perennial grass, is widely distributed in most parts of China. M. sinensis has been selected as a candidate for bioenergy resources, owing to its high biomass potential and good adaptability on marginal lands. In this study, we detected the genetic diversity in wild populations of M. sinensis in southwest China. The results showed the percentage of polymorphic bands is 93.2%, the average Nei's gene diversity in population was 0.3870 and mean Shannon index was 0.5589. The mean of total gene diversity (HT) was 0.3831 ± 0.0216, while the allelic diversity within populations (HS) and among populations (DST) was 0.3127 ± 0.0161 and 0.0704, respectively. The genetic differentiation coefficient (GST) was 0.1838, and the gene flow (Nm) was 1.110. The wild populations of M. sinensis have high genetic diversity within each population than among populations. As M. sinensis has a large phenotypic variation in many traits that are important for biomass yield, the best yielding genotypes could be bred into hybrids with low input and high output bioenergy crops.
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Miscanthus x giganteus is one of the energy crops being considered to help contribute to sustainable biomass for energy production. In combustion, many biomass are characterised by low ash melting behaviour leading to slagging and fouling problems. In this study, a sub-set of samples from a larger Miscanthus agronomy trial have been assessed and studied for their ash melting behaviours using the standard ash fusion test (AFT). The samples selected are from Miscanthus grown under three different fertiliser application regimes and sampled at different times between September–March. Where feasible, leaves have been separated from stems so that the two components can be studied separately. Results are presented concerning ash content and metal analysis, and ash fusion temperatures. Some Miscanthus ash produced rapid evolution of gases during the ash fusion test resulting in swelling of the test pieces. A limited number of ash samples are also investigated further for decomposition and ash melting by simultaneous thermal analysis – mass spectrometry (STA–MS). A number of ash behaviour indices are tested, including the alkali index (a fouling indicator), the base-to-acid ratio and the base percentage, and correlations are examined between some of these and the ash melting temperatures. Miscanthus harvest time has a significant affect on the ash melting behaviour of the crop. Fusion temperatures in Miscanthus leaves are increased as the crop dries and senesces over September to March. While there is some scatter on the data, and the number of samples is small in this study, the general trend is that fusion temperature in Miscanthus stems/whole crop decreases during the period September to March. Although no single index can describe ash behaviour for all ash samples, for Miscanthus ash, it seems that wt% K2O in the ash has very good (non-linear, parabolic) correlation with melting temperature, compared with indices such as base to acid ratio and base percentage. Phosphorous content cannot be ignored in Miscanthus ash analysis, as it seems to lower the ash melting temperature and improve correlations when included in the base to acid ratio. The interpretation of melting behaviour from the STA test is more complex, although these results suggest that the endotherm minimum temperature can be a good estimate of the hemisphere temperature measured in the ash fusion test, to within approximately 25 °C. Further work is required to extend this study to additional biomass types.
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To grow the bioenergy crop Miscanthus x giganteus on wider climate range requires enlarged genetic variability. Our objective was to identify key traits favouring the production of above-ground yield in a cropping environment of Miscanthus at two harvest dates. Canopy height, panicle height, shoot number, stem diameter and above-ground yield of twenty-one clones were studied and compared with emergence earliness and growth traits at autumn and winter harvests in Northern France, during the second and third crop years.Crop age, clone, harvest date, and corresponding double interactions were significant for all traits. Species and ploidy explained clone sum of square effects (92%, 78%, 80% and 89% for canopy height, panicle height, shoot diameter and yield, respectively) and clone×age and clone×harvest date interactions for yield (94% and 77%, respectively). Plant height and shoot number were higher in the third year than in the second, whatever the harvest date. The above-ground development between the two years was higher in winter harvest than in autumn, mostly for M. sinensis. Higher above-ground development and yields were observed for M. x giganteus and M. floridulus than M. sinensis and M. sacchariflorus as well as for triploid and tetraploid M. sinensis and M. sacchariflorus than diploids. Plant height, stem diameter, lateness at panicle emergence or flowering and growth rate were the main traits positively related to yield, in contrast to shoots number and growth duration. This would help to early identify high-yielding clones and breed new inter-specific hybrids.
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Miscanthus species are highly productive with low inputs and are excellent candidates for bioenergy feedstock production. A field experiment was conducted to characterize phenotypic differences in selected clones generated from interspecific hybrids of Miscanthus sinensis×Miscanthus sacchariflorus and intraspecific hybrids within M. sinensis. The field experiment was planted in plots of 20m2 at a density of 1plantm−2 in three randomized blocks. The trial was monitored for 3 years for traits important to biomass production including plant height, tiller density, tuft diameter and shoot diameter. ANOVA showed significant genotypic variation in these traits once the stand was 2 years old. This study shows that tillering and tuft diameter in years 1 and 2 are the most important traits influencing biomass yield, but over 3 years when the highest yielding potential is reached, tillering and tuft diameter have the highest correlation with biomass yield. These results identifying high-yielding Miscanthus clones will be utilized in our plant improvement program.
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Summary Xylose, the predominant sugar in red oak prehydrolysate, is fermented to ethanol byPichia stipitis CBS 5776. Toxic model compounds derived from red oak hemicelluloses, lignin, and extractives inhibited the fermentation. Treatment of the prehydrolysate with molecular sieve and mixed bed ion resins facilitated the ethanol fermentation giving about 10 g/l ethanol from 32 g/l initial xylose. Fermentation inhibitors derived from red oak lignin and extractives were identified.
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Miscanthus plants were sampled from several plantations in Ireland over the harvest window (October-April). These were separated into their anatomical components and the loss of leaves monitored. Three distinct phases were apparent: there was minimal loss in the "Early" (October to early December) and "Late" (March and April) phases, and rapid leaf loss in the interim period. Samples were analysed for constituents relevant to biorefining. Changes in whole-plant composition included increases in glucose and Klason lignin contents and decreases in ash and arabinose contents. These changes arose mostly from the loss of leaves, but there were some changes over time within the harvestable plant components. Although leaves yield less biofuel than stems, the added biomass provided by an early harvest (31.9-38.4%) meant that per hectare biofuel yields were significantly greater (up to 29.3%) than in a late harvest. These yields greatly exceed those from first generation feedstocks.
Article
AbstractA field experiment with 15 Miscanthus genotypes including M. × giganteus, M. sacchariflorus, M. sinensis and M. sinensis hybrids was conducted for 14 years at the experimental Ihinger Hof station of the University of Hohenheim in southwest Germany to evaluate interannual yield performance stability over 14 years of harvests of the different genotypes. In this article, a simple formula is presented which could be used to forecast late winter yields using morphological traits in autumn. The data obtained indicated a shorter establishment period to reach a yield plateau of M. × giganteus and M. sacchariflorus than M. sinensis hybrids and M. sinensis genotypes. The best performing genotype was M. × giganteus (Gig‐2, No. 16.21) with a mean spring harvestable yield of 14.1 t DM ha−1 year−1. A correlation analysis with climatic parameters revealed precipitation during the growing period as the key factor for high yields at this site. Likewise, but to a lesser degree, heat sum during the growing period was positively correlated with yields. It could be shown that precipitation/snow during the winter correlated with yield losses, until the harvest date in February/March. Phenological measurements indicated that a high yield potential of the tested genotypes is associated with either an absence of flowering or late flowering. Also, height of the plants and shoot diameter were indicators for high yield potential. Shoot density and plant height at senescence were found to be solid parameters to estimate harvestable biomass in late winter. Yield approximations with a mean accuracy of 80.9% for M.× giganteus genotypes were obtained using the newly developed equation. Yields of M. sinensis hybrid (Sin‐H7) were projected most accurately with this simple formula, resulting in a mean accuracy of 84.5%.
Article
We report on a replicated spaced-plant trial in Wales of 244 diverse Miscanthus accessions grouped by classical taxonomy into M. sinensis, M. sacchariflorus and M. x giganteus. Large differences in cell wall composition were detected between taxonomic groups. Significantly higher concentrations of NDF (88.19, 85.59 and 85.03 %DW; S.E.D. of 0.300; P < 0.001); ADL (11.76, 10.15 and 9.07 %DW; S.E.D. of 0.087; P < 0.001) and cellulose (47.09, 42.94 and 42.50 %DW; S.E.D. of 0.255; P < 0.001); and significantly lower concentrations of hemicellulose (29.43, 32.50 and 33.46 %DW; S.E.D. of 0.130; P < 0.001) were present in the samples from M. x giganteus compared to the other groups. Growth year and the interaction between taxonomic group and growth year had smaller significant effects. Strong correlations were found between ADL and cellulose (R = 0.72), and hemicellulose (R = −0.76) in the M. x giganteus samples but correlations were weaker for M. sacchariflorus (R = 0.66 and −0.59) and M. sinensis (R = 0.46 and −0.40). Eleven genotypes had been assessed previously in the U.K. during the European Miscanthus Improvement (EMI) programme. These generally had higher concentrations of ADL and hemicellulose, and lower concentrations of cellulose than were reported for the U.K. site during the EMI study. These results suggest that cell wall composition and ADL concentration in particular, is highly stable between growth years but is affected by site location. Furthermore, there are differences in cell wall composition between Miscanthus taxonomic groups that may prove valuable for breeding new varieties that are compositionally matched to conversion process.
Article
Background: An optimal valorization of plant biomasses to produce biofuels requires a good knowledge of the available contents and molecular composition of the main chemical components, which changes with the harvesting date. Therefore, we assessed the influence of harvesting date on the chemical characteristics of various energy crops in the context of their conversion to biofuels. Results: We showed that the biomass chemical composition, enzymatic digestible organic matter, bioethanol and thermal energy production potential for each species are impacted by the harvesting date. The proportion of enzymatically digestible organic matter decreases as the harvesting date is delayed. This is related to the increase in cellulose and lignin contents. The suitability of the biomasses for bioethanol production increases with harvest stage, as the total carbohydrates content increases. The suitability of the biomasses as a source of thermal energy increases according to the harvesting date as the proportion of organic matter increases and the content of mineral compounds decreases. For all investigated energy conversions, the best harvesting period is autumn, because the significantly higher crop dry matter yield largely compensates for the sometimes slightly less favorable chemical characteristics. Conclusion: While the biomass composition of energy crops changes with harvest stage, the dry biomass yield per unit area is the main factor that controls the total amount of chemical components, digestible organic matter, bioethanol and thermal energy that can be expected to be harvested per unit area. The biomass compositions presented in this paper are essential to investigate their suitability for bioenergy conversion.
Article
The aim of this experiment was to measure the chemical composition and morphological and mechanical properties, and to determine the contribution of different tissue components and chemical constituents to the modulus of elasticity of Miscanthus. Randomly selected stems of Miscanthus‘Giganteus’, 10 numbered clones and 6 named cultivars of M. sinensis were harvested in February 1999. Determination of morphological characteristics included counting the number of internodes, measurement of the length of stems and internodes, and size of outer and inner diameter. Culm wall thickness, cross sectional stem area and moment of inertia were calculated, and modulus of elasticity was measured using a three point method. Chemical analysis included determination of the concentration of dry matter, cellulose, lignin, and ashes. Studies of anatomy encompassed determination of number of vascular bundles, area of parenchyma vascular bundles, and outer heavily lignified ring (outer ring). Substantial variations and significant differences between genotypes were found for all morphological and anatomical characteristics and for concentrations of chemical constituents except dry matter. A stepwise regression analysis was carried out on the relationship between modulus of elasticity as the dependent variable, and the morphological characteristics, anatomical characteristics, and the concentration of chemical constituents as independent variables. Modulus of elasticity depended significantly of the area parenchyma vascular bundles and outer heavily lignified tissue (outer ring) and of the concentration of lignin and cellulose. Based on the measured characteristics it was hypothesized that the cultivar ‘Purpurescens’ may have the highest lodging resistance followed by ‘Braunschweigh’ and ‘Giganteus’.
Article
Poplar wood was treated with peracetic acid, KOH, and ball milling to produce 147 modellignocelluloses with a broad spectrum of lignin contents, acetyl contents, and crystallinity indices (CrIs), respectively. An empirical model was identified that describes the roles of these three properties in enzymatic hydrolysis. Lignin content and CrI have the greatest impact on biomass digestibility, whereas acetyl content has a minor impact. The digestibility of several lime-treated biomass samples agreed with the empirical model. Lime treatment removesallacetyl groups and a moderate amount of lignin and increases CrIslightly; lignin removal is the dominant benefit from lime treatment.
Article
Renewable bioenergy could be supplied by high yielding grass crops, such as switchgrass (Panicum virgatum L.). Successful development of a bioenergy industry will depend on identifying cultivars with high yield potential and acceptable biofuel quality. The objective of this study was to evaluate 20 switchgrass populations in a field study planted in May 1997 in southern Iowa, USA. The populations included released cultivars and experimental germplasm of both upland and lowland ecotypes. Yield, plant height, stand, lodging, leaf:stem ratio, cell wall fiber, total plant nitrogen, and ash were determined on all entries between 1998 and 2001. Ultimate and proximate analyses together with chlorine and major oxide determinations were made on three cultivars in 2000 and 2001. Biomass yield was determined from a single autumn harvest each year. The lowland cultivars ‘Alamo’ and ‘Kanlow’ produced the most biomass, exceeding the production of the widely recommended upland cultivar ‘Cave-In-Rock’. Other traits differed among the cultivars, although the range was less than that for yield. The differences among years were substantially greater for the ultimate, proximate, and major oxide analyses than differences among cultivars. The highest yielding cultivars had low ash, slightly lower fiber concentrations, and moderate levels of important minerals, suggesting that excellent germplasm is available for biofuel production. The persistence of the lowland cultivars in southern Iowa may need more research because the winters during the experiment were mild.
Article
The quantities and use efficiencies of nitrogen (N) fertilizer and energy input are seen as important indicators for the environmental impact of the production of energy crops. On the other hand, the high targets set in Europe for the production of biofuels will require high energy yields and efficient use of available agricultural land. The aim of this study is to describe the N, energy and land use efficiencies in relation to the N supply, for the energy crops triticale (Triticosecale Wittmack) – harvested as whole crop – reed canary grass (Phalaris arundinacea L.) and miscanthus (Miscanthus × giganteus). Field trials in Southwest Germany (48–49°N latitude) were performed to measure the biomass and bioenergy yields at different N fertilizer levels. The nitrogen use efficiency (NUE), defined as the ratio of biomass yield to N supply (sum of soil NO3−–N and N fertilized) and the energy use efficiency (EUE) (net energy yield/energy input), were derived from data on biomass and bioenergy yields by the boundary line approach. For all three crops, NUE and EUE decreased with increasing N fertilizer rates. NUE and EUE were at all N and energy inputs highest for miscanthus and lowest for reed canary grass. At an N supply of 100 kg ha−1 a−1, the NUEs of miscanthus, triticale and reed canary grass were 0.35, 0.14 and 0.11 t dry biomass/kg N, respectively. At an energy input of 10 GJ ha−1, the EUEs for miscanthus, triticale and reed canary grass were 54, 26 and 13 GJ bioenergy per GJ energy input, respectively. The highest net energy yields (here used as indicator for the land use efficiency) of triticale and reed canary grass were harvested at the highest N fertilizer level of 140 kg N, with maximum values of 281 and 129 GJ ha−1 a−1, respectively. These results show that for triticale and reed canary grass, the maximization of NUE, EUE and land use efficiency are conflicting. Only for miscanthus, the N, energy and land use efficiencies were simultaneously highest at the lowest N supply level. A maximum net energy yield of 590 GJ ha−1 a−1 was harvested from miscanthus. It was concluded that the best way to maximize resource use efficiency in biomass production is to choose for the production of the perennial C4 crop miscanthus, at those locations that are suitable for miscanthus production.
Article
Field experiments to test the biomass production from the C4 perennial grass Miscanthus have concentrated on one triploid genotype, namely M.×giganteus. Several limitations to production from M.×giganteus including insufficient winter rhizome cold tolerance demonstrated the need to broaden the genetic base. This paper presents results from a field trial in Southern Germany planted with 15 Miscanthus genotypes including M.×giganteus, M. sacchariflorus, wild M. sinensis and bred M. sinensis hybrids over 3 years. Under field conditions, establishment from micro-propagation was high and all genotypes survived the first winter (losses<6%). Genotype growth characteristics were determined by measurements of height, shoot density, stem diameter, flowering time and autumn senescence rate. Increasing plant age was associated with higher yields (2, 6, and 17 t dry matter ha−1 in autumn of years one to three, respectively) and better biomass qualities for combustion. Delaying harvest time from autumn until spring in the second and third years reduced harvestable yields but increased combustion quality by lowering moisture, ash, Cl and N contents for all genotypes. Yields were highest for the M.×giganteus and some newly bred M. sinensis hybrids, but biomass qualities were best in the pure M. sinensis genotypes. These trials showed that new hybrids between M. sacchariflorus and M. sinensis should be developed that have many growth characteristics similar to M.×giganteus but with improved rhizome freeze tolerance in winter. As the biomass yield and quality of a particular genotype after 1 year of growth does not always relate to that measured in subsequent years, identification of the most suitable genotypes requires at least 2 years.
Article
Fifteen Miscanthus genotypes grown in five locations across Europe were analysed to investigate the influence of genetic and environmental factors on cell wall composition. Chemometric techniques combining near infrared reflectance spectroscopy (NIRS) and conventional chemical analyses were used to construct calibration models for determination of acid detergent lignin (ADL), acid detergent fibre (ADF), and neutral detergent fibre (NDF) from sample spectra. Results generated were subsequently converted to lignin, cellulose and hemicellulose content and used to assess the genetic and environmental variation in cell wall composition of Miscanthus and to identify genotypes which display quality traits suitable for exploitation in a range of energy conversion systems. The NIRS calibration models developed were found to predict concentrations with a good degree of accuracy based on the coefficient of determination (R2), standard error of calibration (SEC), and standard error of cross-validation (SECV) values. Across all sites mean lignin, cellulose and hemicellulose values in the winter harvest ranged from 76–115 g kg−1, 412–529 g kg−1, and 235–338 g kg−1 respectively. Overall, of the 15 genotypes Miscanthus x giganteus and Miscanthus sacchariflorus contained higher lignin and cellulose concentrations in the winter harvest. The degree of observed genotypic variation in cell wall composition indicates good potential for plant breeding and matching feedstocks to be optimised to different energy conversion processes.
Article
A catalogue is set up describing the quality characteristics relevant for the combustion of biomass to be used as solid fuel. The practical relevance of these characteristics is discussed. The main characteristics are water concentration, the concentration of chloride and ash, the heating value and the concentration of volatiles and remaining coke. Further quality criteria are the concentrations of nitrogen, sulphur, potassium and calcium.In multifactorial field trials at three locations, the influence of location, fertilizer application and harvest date on the quality of Miscanthus biomass from 3- and 4-year-old plantations was tested. The concentrations of water, minerals and ash, all three of which should be as low as possible, were higher in biomass from the cool and humid than in biomass from the warm location. The application of potassium fertilizer led to increases in the ash and potassium concentrations. Harvesting Miscanthus in February instead of December led to an improved biomass quality because the concentrations of ash, minerals and especially of water had declined.Compared to other lignocellulose plants Miscanthus biomass has a very good combustion quality. In February the stems of Miscanthus had a water concentration of only 16–33%. The mineral concentrations were also low, with 0.3–2.1 g kg−1 for chloride, 0.9–3.4 g kg−1 for nitrogen and 3.7–11.2 g kg−1 for potassium. © 1997 Elsevier Science B.V.
Article
The chemical composition of the whole aerial biomass and isolated organs of Miscanthus x giganteus was examined for saccharification into fermentable sugars at early and late harvesting dates. Delayed harvest was mainly related to increased amounts of cell wall and ester-linked phenolic acids. Addition of an enzyme cocktail (cellulases, beta-glucosidase and xylanase) resulted in similar enzyme digestibilities at the two harvesting dates, ranging from 11-13% and 8-9% of the cellulose and arabinoxylan, respectively. However, the internodes, leaves and sheaths varied in cell wall content and composition and gave rise to different saccharification yields with internodes being the most recalcitrant organs. Non-cell wall fraction was estimated as the amount of material extracted by neutral detergent solution, and accounted for 23% of the whole aerial biomass harvested at an early date. However, saccharification yields from the miscanthus biomass did not change after soluble fraction removal. An ammonia pretreatment improved enzyme efficiency on early-harvested miscanthus, to a greater extent than on late-harvested biomass. This trend was confirmed for two different years of harvesting.
Article
Field trials throughout Europe over the past 15 years have confirmed the potential for high biomass production from Miscanthus, a giant perennial rhizomatous grass with C4 photosynthesis. However, policies to promote the utilization of biomass crops require yield estimates that can be scaled up to regional, national and continental areas. The only way in which this information can be reliably provided is through the use of productivity models. Here, we describe MISCANMOD, a productivity model, which was used in conjunction with a GIS to plot potential, non-water-limited yields across Europe. Modelled rainfed yields were also calculated using a water balance approach based on FAO estimates of plant available water in the soil. The observed yields were consistent with modelled yields at 20 trial sites across Europe. We estimate that if Miscanthus was grown on 10% of suitable land area in the European Union (EU15), 231 TWh yr−1 of electricity could be generated, which is 9% of the gross electricity production in 2000. Using the same scenario, the total carbon mitigation could be 76 Mt C yr−1, which is about 9% of the EU total C emissions for the 1990 Kyoto Protocol baseline levels.
Article
C(4) perennial grasses are being considered for bioenergy because of their high productivity and low inputs. In side-by-side replicated trials, Miscanthus (Miscanthus x giganteus) has previously been found more than twice as productive as switchgrass (Panicum virgatum). The hypothesis that this difference is attributable to higher leaf photosynthetic rates was tested on established plots of switchgrass and Miscanthus in central Illinois with >3300 individual measurements on 20 dates across the 2005 and 2006 growing seasons. Seasonally integrated leaf-level photosynthesis was 33% higher in Miscanthus than switchgrass (P < 0.0001). This increase in carbon assimilation comes at the expense of additional transpiration since stomatal conductance was on average 25% higher in Miscanthus (P < 0.0001). Whole-chain electron transport rate, measured simultaneously by modulated chlorophyll fluorescence, was similarly 23% higher in Miscanthus (P < 0.0001). Efficiencies of light energy transduction into whole chain photosynthetic electron transport, leaf nitrogen use and leaf water use were all significantly higher in Miscanthus. These may all contribute to its higher photosynthetic rates, and in turn, productivity. Systematic measurement of photosynthesis over two complete growing seasons in the field provides a unique dataset explaining why the productivity of these two species differs and for validating mechanistic production models for these emerging bioenergy crops.
Article
Mixed linear models were developed by animal breeders to evaluate genetic potential of bulls. Application of mixed models has recently spread to all areas of research, spurred by availability of advanced computer software. Previously, mixed model analyses were implemented by adapting fixed-effect methods to models with random effects. This imposed limitations on applicability because the covariance structure was not modeled. This is the case with PROC GLM in the SAS System. Recent versions of the SAS System include PROC MIXED. This procedure implements random effects in the statistical model and permits modeling the covariance structure of the data. Thereby, PROC MIXED can compute efficient estimates of fixed effects and valid standard errors of the estimates. Modeling the covariance structure is especially important for analysis of repeated measures data because measurements taken close in time are potentially more highly correlated than those taken far apart in time.
Article
The term ‘repeated measures’ refers to data with multiple observations on the same sampling unit. In most cases, the multiple observations are taken over time, but they could be over space. It is usually plausible to assume that observations on the same unit are correlated. Hence, statistical analysis of repeated measures data must address the issue of covariation between measures on the same unit. Until recently, analysis techniques available in computer software only offered the user limited and inadequate choices. One choice was to ignore covariance structure and make invalid assumptions. Another was to avoid the covariance structure issue by analysing transformed data or making adjustments to otherwise inadequate analyses. Ignoring covariance structure may result in erroneous inference, and avoiding it may result in inefficient inference. Recently available mixed model methodology permits the covariance structure to be incorporated into the statistical model. The MIXED procedure of the SAS® System provides a rich selection of covariance structures through the RANDOM and REPEATED statements. Modelling the covariance structure is a major hurdle in the use of PROC MIXED. However, once the covariance structure is modelled, inference about fixed effects proceeds essentially as when using PROC GLM. An example from the pharmaceutical industry is used to illustrate how to choose a covariance structure. The example also illustrates the effects of choice of covariance structure on tests and estimates of fixed effects. In many situations, estimates of linear combinations are invariant with respect to covariance structure, yet standard errors of the estimates may still depend on the covariance structure. Copyright © 2000 John Wiley & Sons, Ltd.
Article
An overview of the different inhibitors formed by pre-treatment of lignocellulosic materials and their inhibition of ethanol production in yeast and bacteria is given. Different high temperature physical pre-treatment methods are available to render the carbohydrates in lignocellulose accessible for ethanol fermentation. The resulting hydrolyzsates contain substances inhibitory to fermentation-depending on both the raw material (biomass) and the pre-treatment applied. An overview of the inhibitory effect on ethanol production by yeast and bacteria is presented. Apart from furans formed by sugar degradation, phenol monomers from lignin degradation are important co-factors in hydrolysate inhibition, and inhibitory effects of these aromatic compounds on different ethanol producing microorganisms is reviewed. The furans and phenols generally inhibited growth and ethanol production rate (Q(EtOH)) but not the ethanol yields (Y(EtOH)) in Saccharomyces cerevisiae. Within the same phenol functional group (aldehyde, ketone, and acid) the inhibition of volumetric ethanol productivity was found to depend on the amount of methoxyl substituents and hence hydrophobicity (log P). Many pentose-utilizing strains Escherichia coli, Pichia stipititis, and Zymomonas mobilis produce ethanol in concentrated hemicellulose liquors but detoxification by overliming is needed. Thermoanaerobacter mathranii A3M3 can grow on pentoses and produce ethanol in hydrolysate without any need for detoxification.
Article
Currently, most ethanol produced in the United States is derived from maize kernel, at levels in excess of four billion gallons per year. Plant lignocellulosic biomass is renewable, cheap and globally available at 10-50 billion tons per year. At present, plant biomass is converted to fermentable sugars for the production of biofuels using pretreatment processes that disrupt the lignocellulose and remove the lignin, thus allowing the access of microbial enzymes for cellulose deconstruction. Both the pretreatments and the production of enzymes in microbial tanks are expensive. Recent advances in plant genetic engineering could reduce biomass conversion costs by developing crop varieties with less lignin, crops that self-produce cellulase enzymes for cellulose degradation and ligninase enzymes for lignin degradation, or plants that have increased cellulose or an overall biomass yield.