Evaluation the efficacy of extrusion pretreatment via enzymatic digestibility and simultaneous saccharification & fermentation with rapeseed straw

The efficacy of extrusion pretreatment was evaluated by enzymatic hydrolysis and simultaneous saccharification and fermentation (SSF) with straw of rapeseed, Brassica napus, an agricultural residue. An acceptable pretreatment result was obtained at a barrel temperature of 165 °C, acid concentration of 20 g L⁻¹, liquid feeding rate of 13.4 cm³ min⁻¹, solid feeding rate of 1.0 g min⁻¹, screw rotation speed of 6.3 rad s⁻¹, and residence time of 10.2 min, with a yield of xmg, representing the sum of the corresponding hydrolyzed sugars; xylose, mannose and galactose, of 794.3 g kg⁻¹ and a glucose release of 21.0 g kg⁻¹. These were calculated to be 963.0 g kg⁻¹ and 910.3 g kg⁻¹ based on cellulose and hemicellulose recoveries,respectively. The highest enzymatic digestibility of 781.0 g kg⁻¹was higher than that obtained from the batch pretreatment with dilute acid by 1.4-fold. The SSF process afforded an ethanol concentration of 16.0 g L⁻¹, corresponding to an ethanol yield of 790 g kg⁻¹ based on the total available cellulose in the pretreated rapeseed straw.     

ABE fermentation from enzymatic hydrolysate of NaOH-pretreated corncobs

Acetone butanol ethanol (ABE) was produced from enzymatic-hydrolyzed corncobs by Clostridium saccharobutylicum DSM 13864. Pretreatment of corncobs was carried out with 0.5 mol L⁻¹ NaOH followed by enzymatic hydrolysis. The yield of total reducing sugars was 917 g kg⁻¹ pretreated (de-lignified) and washed corncobs. The hydrolysate was used without sediments removal for ABE fermentation. A solvent production of 19.44 g L⁻¹ with 12.27 g L⁻¹ butanol was obtained from 55.22 g L⁻¹ sugars, resulting in an ABE yield of 350 g kg⁻¹ and a production rate of 0.54 g L⁻¹ h⁻¹. A control experiment using 55.3 g L⁻¹ mixed sugars resulted in an ABE production of 16.81 g L⁻¹ with 10.26 g L⁻¹ butanol, corresponding to an ABE yield of 300 g kg⁻¹ and a production rate of 0.47 g L⁻¹ h⁻¹, indicating that the enzymatic hydrolysates may contain stimulating compounds that can improve the ABE fermentation.     

Ethanol production from halophyte Juncus maritimus using freezing and thawing biomass pretreatment

Juncus maritimus contains (41.5 ± 0.3)% cellulose and (31.34 ± 0.2)% hemicellulose on dry solid (DS) basis and has the potential to serve as a low cost feedstock for ethanol production. Dilute acid or freezing/thawing pretreatments and enzymatic saccharification were evaluated for conversion of halophyte plant from J. maritimus cellulose and hemicelluloses to monomeric sugars. The maximum concentration of released glucose from J. maritimus (53.78 ± 3.24) g L⁻¹) by Freezing/thawing pretreatment and enzymatic saccharification (55 °C, pH 5.0 and 48 h) using CellicCTec2 from Novozymes and (49.14 ± 5.24) g L⁻¹ obtained by dilute acid pretreatment. The maximum yield of ethanol from acid pretreated enzyme saccharified J. maritimus hydrolyzate by Saccharomyces cerevisiae strain was (84.28 ± 5.11)% of the theoretical yield with a productivity of (0.88 ± 0.16)g L⁻¹ h⁻¹. It was (90.87 ± 1.94)% of the theoretical yield with a productivity of (1.04 ± 0.10) g L⁻¹h⁻¹ for freezing/thawing pretreated plant and enzymatic hydrolysis by CellicCTec2.     

Effects of soil texture on germination and survival of non-toxic Jatropha curcas seeds

Toxic oil seeds of Jatropha curcas have been widely propagated in tropical and subtropical regions for biofuel production. However, very little is known about the non-toxic seeds of J. curcas and their germination. This paper describes the germination and survival of non-toxic J. curcas seeds over two consecutive years. Non-toxic seeds native from southeastern Mexico (600–800 mg weight) were sown in three soils with different texture (sandy; sandy-loam and clay-loam) in order to assess germination, speed of germination and survival rates of the emerged seedlings. Sandy soil had the lowest organic matter (OM) content with 1.68 g-kg⁻¹ of dry soil, followed by sandy-loam soil (39 g-kg⁻¹) and clay-loam soil with the highest OM (72.63 g-kg⁻¹). The highest germination rate was obtained in sandy-loam (76%), followed by sandy (75%) and clay-loam soil (24%). The highest survival rates were obtained in sandy (99%) and sandy-loam (99%) soils followed by clay-loam soil (87%). The highest average speed of germination index was recorded in sandy (155), followed by sandy-loam (125) and clay-loam soil (23). It can be concluded that sandy and sandy-loam soil textures, with bigger pore size and low organic matter content, were the more suitable substrates to germinate non-toxic J. curcas seeds; clay loam as substrate was not suitable for non-toxic J. curcas seeds due to the low germination rate and speed.     

Response surface design to study the influence of inoculum,particle size and inoculum to substrate ratio on the methane production from Ulex sp.

Ulex europaeus is one of the world worst invaders vegetal species and its suitability for biogas production is significant. The effect of three factors affecting the Biochemical Methane Potential (BMP, expressed as volume of CH₄ per mass of volatile solids of waste) and the biodegradability rate (k, expressed in volume of CH₄ per mass of VS and time) of U. europaeus was assessed by a Central Composite Face Centred Design. The BMP varied from 153 L kg⁻¹ to 308 L kg⁻¹. Inoculum to substrate ratio (ISR) and the type of inoculum had high influence on the final results. k varied from 14 L kg⁻¹ d⁻¹ to 49 L kg⁻¹ d⁻¹. The conditions that simultaneously maximized the BMP and k were an inoculum consisting in 55% (v) of granular sludge and 45 % (v) of suspended sludge from a sludge digester, an ISR of 4 g g⁻¹, and a particle size of 1.9 mm. Considering the average biomass production in shrub land areas, the potential energy production from U. europaeus is estimated in (36.9 ± 19.3) GJ ha⁻¹ yr⁻¹. For example, in Europe, a maximum energy supply of 7 EJ yr⁻¹ could be achieved from potentially harvestable shrub land areas.     

A biorefinery approach to microbial oil production from glycerol by Rhodotorula glutinis

The use of biodiesel-derived glycerol as a carbon source for microbial oil production is a biorefinery engineering strategy that aims to reduce the glycerol surplus and make the microbial oil process more cost-effective. In this work, glycerol was used as the sole carbon source for the cultivation of the oleaginous yeast Rhodotorula glutinis along with only yeast extract as a nutrient supply and without pH control. Shake-flask cultivations showed that the specific growth rate and glycerol consumption of Rhodotorula glutinis were higher at lower glycerol concentrations (≤40 g L⁻¹), while higher C/N atom ratios enhanced oil content. The present study extends the knowledge on the influence of the aeration rate and oxygen supply in cellular growth rate and microbial oil production, providing a wiser use of glycerol as an attempt to further reduce process costs. Cultivations at different air flow rates were performed in a 2 L bioreactor and showed that a low aeration rate of 0.5 L min⁻¹ gave the best glycerol and nitrogen uptake rates, resulting in the highest growth (5.3 g L⁻¹) and oil mass fraction (33% of the dry cell weight). A further 68% increase in cellular growth (16.8 g L⁻¹) and a 34% oil mass fraction of the dry cell weight was achieved after applying a feeding strategy targeting combined growth and oil production.     

Catalytic conversion of Helianthus tuberosus L. to sugars, 5-hydroxymethylfurfural and levulinic acid using hydrothermal reaction

In this study, the efficient conversion of Helianthus tuberosus L. (Jerusalem artichoke) to sugar, 5-hydroxymethylfurfural (5-HMF), and levulinic acid (LA) were investigated using a Brønsted acid-catalyzed hydrothermal reaction. From this approach, the optimal amounts and reaction conditions for total reducing sugar (TRS), 5-HMF, and LA were as follows: 444 g kg⁻¹ of TRS yield (150.4 °C, 14.6 kg m⁻³ sulfuric acid, and 9.8 min), 193 g kg⁻¹ of 5-HMF yield (166.0 °C, 4.6 kg m⁻³, 30.8 min), and 323 g kg⁻¹ of LA yield (185 °C, 30.8 kg m⁻³, 33.7 min). In terms of combined severity, the TRS and 5-HMF concentrations decreased linearly with increasing combined severity, whereas, the LA concentration was increased at a high combined severity factor. The H. tuberosus L. may be useful as a significant feedstock for the production of platform chemicals such as 5-HMF and LA.     

Vegetable oil production potential from Jatropha curcas, Croton megalocarpus, Aleurites moluccana, Moringa oleifera and Pachira glabra: Assessment of renewable energy resources for bio-energy production in Africa

Research on vegetable oil for biofuels in Africa and Asia has focused mainly on Jatropha curcas while other potential oil bearing plants have received little attention. Vegetable oil production potential for five oil bearing plant species namely: Aleurites moluccana, Croton megalocarpus, Jatropha curcas, Moringa oleifera and Pachira glabra were investigated. Nuts and seeds of the plants were collected from the wild and their potential for vegetable oil production assessed in terms of seed/nut acreage yield, seed/nut oil content, harvesting requirement, and upstream processing before vegetable oil recovery. All five varieties were found to contain acceptable but different oil content ranging from 20 to 33% w/w, and seed/nut acreage yield of 3 t ha⁻¹ y⁻¹ to 12.5 t ha⁻¹ y⁻¹. Upstream processing was needed for A. moluccana to break open nuts to release the kernel, and dehulling for both C. megalocarpus and J. curcas to release the seeds, before extracting the vegetable oil, while the seeds of both M. oleifera and P. glabra did not need upstream processing. The Multi-criteria Decision Analysis ranked C. megalocarpus as the plant with the highest vegetable oil production potential of 1.8 t ha⁻¹ y⁻¹ followed by M. oleifera, J. curcas (1 t ha⁻¹ y⁻¹), A. moluccana, and P. glabra. The analysis underlines the need for more studies on C. megalocarpus and M. oleifera for biofuel production in Africa and other regions.     

Effect of salt and sodium concentration on the anaerobic methanisation of the halophyte Tripolium pannonicum

The halophyte species Sea Aster (Tripolium pannonicum) was grown with different concentrations of artificial seawater. In a second experiment, T. pannonicum was cultivated with a nutrient solution containing different concentrations of NaCl. This halophyte biomass was used to determine the biogas production potential. According to the findings, it is possible to produce high yields of methane using biomass from halophytes cultivated in the presence of salt. Biogas and methane yield are influenced by the salt content of the plant tissue, however, high concentrations of salt in the anaerobic reactors itself inhibit the biogas and methane production. The highest methane yield is obtained using plant substrates grown at 22.5 g L⁻¹ sea-salt with a value of 313 cm³ g⁻¹ of VS. When treating T. pannonicum with different concentrations of NaCl, biogas and methane yields are highest when using plant substrates grown at 30 g L⁻¹ to produce values of 554 cm³ g⁻¹ of VS and 447 cm³ g⁻¹ of VS, respectively. Other research was carried out to study the effect of sodium on the biogas and methane yields using substrate from T. pannonicum cultured under non-saline conditions and adding different amounts of NaCl to the anaerobic reactors. Adding NaCl to the reactors decreases the biogas and methane production but using a salt-adapted inoculum increases the biogas yield in comparison to the non-adapted inoculum.     

Use of treated effluent water in ethanol production from cellulose

The bioethanol industry exerts a significant demand on water supplies. Current water consumption rate in corn dry grind ethanol plants is (11–15) dm³ m⁻³ of ethanol produced and (23–38) dm³ m⁻³ for cellulosic ethanol plants. The main goal of this study was to examine the feasibility of use of treated wastewater effluent in place of potable freshwater for cellulosic ethanol production. The effects of using two different types of filtered treated effluent; Bloomington- Normal, IL (Residential type) and Decatur, IL (Industrial/Residential Mix type); on the rate of fermentation and final ethanol yield from a pure cellulosic substrate were evaluated. Characterization analysis of both effluent water samples indicated low concentration of toxic elements. Final ethanol concentrations obtained with Bloomington- Normal and Decatur effluent and with a control treatment using de-ionized water were similar, resulting in 360 g kg⁻¹ (0.36 g g⁻¹), 370 g kg⁻¹ (0.37 g g⁻¹) and 360 g kg⁻¹ (0.36 g g⁻¹), respectively. These findings suggest that with proper characterization studies and under appropriate conditions, the use of treated effluent water in cellulosic ethanol production is feasible.     

Biomass production and nutrient cycling in Eucalyptus short rotation energy forests in New Zealand: II. Litter fall and nutrient return

Litter fall and nutrient return via the litter fall were measured during the first 3-yr rotation of three Eucalyptus short rotation forest species (E. botryoides, E. globulus and E. ovata) irrigated with meatworks effluent compared with no irrigation. Up to 13.4 oven dry t/ha/yr of annual litter fall was recorded with nutrient returns of up to 159 kg N/ha/yr, 9 kg P/ha/yr, 28 kg K/ha/yr, 125 kg Ca/ha/yr, 22 kg Mg/ha/yr, and 32 kg Mn/ha/yr. Effluent irrigation increased the litter fall and the return of some nutrients. More litter fall with higher nutrient return was found under E. globulus than under the other two species. However, the amounts of litter fall and nutrient return were highly dependent on the degree of biomass production and nutrient uptake. During the 3-yr period, up to 20% of the total above ground biomass produced was in the form of litter, and via the litter fall, up to 24% of the total N uptake was returned to the soil surface.     

Isochrysis sp. IOAC724S,a newly isolated,lipid-enriched,marine microalga for lipid production,and optimized cultivation conditions

An oleaginous, unicellular, marine microalga termed IOAC724S was isolated from the South China Sea. Morphology and genetic analyses indicated it belongs to the genus Isochrysis. Gas chromatography (GC) results showed that more than 10 types of fatty acids existed in Isochrysis sp. IOAC724S and that 90% of them were suitable for lipid production. The culture conditions suitable for cell growth were progressively optimized through photosynthetic and respiratory analyses. The optimal culture conditions were: photon flux 200–500 μmol m⁻² s⁻¹, temperature 35 °C during daytime and 24 °C at night, pH value between 7 and 8, NaNO₃ 160 g m⁻³ and NaH₂PO₄·2H₂O 80 g m⁻³ for starting culture. When microalgal cultures were exposed to these optimal conditions, the specific growth rate reached to 0.26 d⁻¹ on average and 1.0 d⁻¹ in MAX. Lipid production was optimized through nutrient starvation processes, including nitrate or phosphate deprivation and simultaneous nitrate and phosphate deprivation. The highest lipid mass fraction of dry cell weight (about 55.6%) was obtained after the stationary phase algal culture was transferred into phosphate-free medium for 3 days. GC data demonstrated that the enhancement of lipid accumulation in algal cells maintained under nutrient starvation came mainly from an increase of C16:0 and C18:1 fatty acids; however, the lipids with a chain length appropriate for fuel use (C14 to C18) were unchanged at 90% mass fraction of the dry cell weight. Based on these good characteristics, Isochrysis sp. IOAC724S appeared to be a strong candidate for lipid production.     

Sickle bush (Dichrostachys cinerea L.) field performance and physical–chemical property assessment for energy purposes

The sickle bush (Dichrostachys cinerea (L.) Wight & Arn.) comprises a woody legume shrub which is widely distributed throughout of the tropical areas of Africa, Asia and Oceania, being found as well in Cuba where it represents a difficult to control invasive plant. It holds great silvopasture and energy crop potentials. In southwestern Spain a two year field trial was conducted contemplating also another six hardwood taxa commonly used as energy crops. The sickle bush above ground dry biomass fraction was 60.4%; sickle bush displayed a high transpiration rate during hot days (3.02 kg m⁻² d⁻¹ to 6.82 kg m⁻² d⁻¹); cold winter temperatures (<−2 °C) together with hot and dry summer air (<20% relative humidity) committed survival and growth. The physical-chemical wood properties and the pellets thereof derived were analyzed and compared to those of the other energy crop taxa. The within other woody species normal chemical composition range coupled to a high wood density and energetic use properties (19.2 MJ kg⁻¹ higher heating value, 29 g kg⁻¹ ash content) all allow for an industrial use. Pellets evidenced also good physical and mechanical properties (690 kg m⁻³ bulk density, 42 g kg⁻¹ moisture content). However, the mechanical durability (93.9%) was slightly less than that required by the non-industrial use standards, therefore further improvements should be studied. All of the above could encourage scrubland cuts in Cuba as a mechanical control method, in addition to the expansion of plantations within of their tropical climate based natural habitats.     

Production of xylose and glucose from rapeseed straw in subcritical water – Use of Doehlert design for optimizing the reaction conditions

The hydrothermal depolymerization of the hemicellulosic and cellulosic fractions of rapeseed straw was carried out in a batch reactor in subcritical water. The experimental design methodology (Doehlert matrix) was used to model the hydrothermal process and to optimize operational parameters reaction temperature and holding time for highest yields of saccharides: xylose and glucose, obtained in experimental series 1 and 2, respectively. In good agreement with experimental results, the model predicts an optimal yield of xylose (60.4 g kg⁻¹ ± 2.1 g kg⁻¹) at a temperature and a holding time of about 203 °C and 13 min. The optimal yield of glucose (180.7 g kg⁻¹ ± 2.8 g kg⁻¹) required higher temperatures but shorter times and was obtained at a temperature 255 °C and a holding time of 9 min. A further increase of both reaction parameters would lead to the undesirable transformation of the saccharides: their dehydration, retro-aldol condensation, isomerization and tautomerization. The obtained results confirm that the hydrothermal treatment of rapeseed straw in optimal reaction conditions might be an alternative route for the production of xylose and glucose.     

Relationships among Jatropha curcas seed yield and vegetative plant components under different management and cropping systems in Indonesia

An understanding of how Jatropha curcas seed yield relates to vegetative plant components under different management regimes is lacking. Such information is necessary to predict yields and design management strategies. This study investigated yield and vegetative plant component interactions, and the effects of management practices in monoculture, intercropping, and hedge cropping systems in Indonesia. Monoculture and intercropping experiments in Gunungkidul Regency used jatropha IP-1M material; hedge experiments in Sumbawa Regency used the Sumbawa provenance. In two-year-old monoculture, pruning significantly decreased yield from 109 kg ha⁻¹ to 28 kg ha⁻¹ due to a 40% decrease in canopy volume and LAI. In four-year-old jatropha intercropping, root barriers reduced yields 80% by limiting jatropha root access to soil moisture and nutrients in the maize plantings. Intercropping without root barrier and with leaf mulch produced the largest yields of 25 kg ha⁻¹. In hedge plantings, plant height influenced yield. Single rows of one-year-old monoculture produced 0.97 g m⁻¹ at 10 cm spacing, 1.69 g m⁻¹ at 30 cm, and 0.14 g m⁻¹ for 20 cm of mixed jatropha–gliricidia. Pruning significantly decreased LAI with 20 cm spacing indicating a higher proportion of above-ground biomass allocated for wood growth. Results indicate that seed yield across the three cropping systems can be determined by plant height and numbers of productive twig/branch, although number of inflorescences cluster per productive twig may be more important. Future research should focus on the transition of branches to reproductive phases, and on increasing numbers of productive twigs/branches and inflorescence clusters.     

Productivity and biochemical composition of Phaeodactylum tricornutum (Bacillariophyceae) cultures grown outdoors in tubular photobioreactors and open ponds

In this study we compared the biomass productivity and the chemical composition of the diatom Phaeodactylum tricornutum grown outdoors at different biomass concentrations, in open ponds and photobioreactors (PBRs). Optimal biomass concentration of 0.6 g L⁻¹ and 1.0 g L⁻¹ was found in open ponds and in PBRs, respectively. During summer the mean net areal biomass yield was 11.7 g m⁻² day⁻¹ and 13.1 g m⁻² day⁻¹ in open ponds and in PBRs, respectively. Night biomass loss was comparable (17.4% and 21.4% of the daylight productivity, in open ponds, and PBRs, respectively). Lipid content ranged between 25% and 27.5% of dry weight, and increased up to 34.7% of biomass grown in dense cultures (>0.6 g L⁻¹ in ponds; >1.0 g L⁻¹ in PBRs). In the evening they ranged between 21% and 31%, while a reduced amount was found in the morning – between 14.5% and 24%. An induction of the diadino–diatoxanthin cycle was observed in the cultures when they were grown at lower biomass concentrations, particularly in cultures grown in photobioreactors, indicating down-regulation of the photosynthetic apparatus due to high irradiance, which was confirmed by a sizeable reduction in the F_v/F_m ratio in the middle of day. It was found that the productivity of cultures was higher in photobioreactors compared to that in open ponds most likely as a result of a better light–dark regime experienced by the cells in short light-path tubular PBRs, which may have allowed a more efficient use of light.     

Sweet and sour potential of yeast from the Yarrowia clade

The food industry is witnessing a growing demand for food additives. Microbial fermentation is an attractive way to produce them using microorganisms, including the yeast Yarrowia lipolytica. Twelve species of the Yarrowia clade were screened for erythritol, mannitol and citric acid production from pure glycerol, glucose or fructose in four different media. During shake-flask cultures, only Y. lipolytica was able to secrete citric acid. Glycerol was found to be the best substrate for erythritol and mannitol biosynthesis by all the species. The six best candidate species for sweetener biosynthesis were cultivated in bioreactors. Up to 69.8 g dm⁻³ of total polyols with a yield of 0.59 g g⁻¹ was obtained for Candida oslonensis, the best sweetener producer. It secreted 44.6 g dm⁻³ of erythritol (Q_Ery = 1.16 g dm⁻³ h⁻¹ and Y_Ery/S = 0.4 g g⁻¹) and 34 g dm⁻³ of mannitol (0.29 g g⁻¹). Additionally, Candida hollandica and Yarrowia divulgata represent promising species for which media composition and culture parameters still have to be optimized.     

Lignocellulosic ethanol production employing immobilized Saccharomyces cerevisiae in packed bed reactor

Most of ethanol production processes are limited by lower ethanol production rate and recyclability problem of ethanologenic organism. In the present study, immobilized co-fermenting Saccharomyces cerevisiae GSE1618 was employed for ethanol fermentation using rice straw enzymatic hydrolysate in a packed bed reactor (PBR). The immobilization of S. cerevisiae was performed by entrapment in Ca-alginate for optimization of ethanol production by varying alginic acid concentration, bead size, glucose concentration, temperature and hardening time. Remarkably, extra hardened beads (EHB) immobilized with S. cerevisiae could be used up to repeated 40 fermentation batches. In continuous PBR, maximum 81.82 g L⁻¹ ethanol was obtained with 29.95 g L⁻¹ h⁻¹ productivity with initial glucose concentration of 180 g L⁻¹ in feed at dilution rate of 0.37 h⁻¹. However, maximum ethanol concentration of 40.33 g L⁻¹ (99% yield) with 24.61 g L⁻¹ h⁻¹ productivity was attained at 0.61 h⁻¹ dilution rate in fermentation of un-detoxified rice straw enzymatic hydrolysate (REH). At commercial scale, EHB has great potential for continuous ethanol production with high productivity using lignocellulosic hydrolysate in PBR.     

Above-ground biomass production and nutrient accumulation in young stands of silver birch on abandoned agricultural land

During the last decade, more than 400 000 ha of agricultural land was abandoned in Estonia. Such areas are often characterized by rapid natural afforestation with silver birch, which has led to an increase both in the woodland area and in the area of silver birch stands. However, many bioenergetic aspects related to birch stands growing on arable land are still poorly understood. The main aim of the present study was to investigate the above-ground biomass production, nutrient (NPK) accumulation, and foliar characteristics of young silver birch stands on abandoned agricultural land. Five 8-year-old stands of silver birch growing on different soil types were included in the study.The density of the studied stands varied from 3060 to 36 200 trees per ha and their above-ground biomass varied from 6.0 to 22.9 t DM ha⁻¹. The largest share in the above-ground biomass of the birches (59–80%) was from the stems. The mean stem mass of the birches ranged from 0.29 to 1.79 kg, and the mean total above-ground biomass ranged from 0.36 to 3.03 kg. The leaf area index for the studied stands varied from 1.21 to 4.64 m² m⁻², being the highest for the stand of medium density. Mean single leaf area varied from 9.4±0.2 to 15.4±0.3 cm², leaf weight per area varied from 61.1±0.4 to 77.5±0.5 g m², and specific leaf area varied from 13.2±0.1 to 16.8±0.1 m² kg⁻¹. However, no significant differences were found between stand density and the foliar characteristics. There was a strong positive correlation between soil nitrogen concentration and leaf nitrogen concentration (R=0.92); regarding phosphorus concentration, the corresponding correlation was weak (R=0.52) and regarding potassium concentration, no significant correlation was found. The amount of nitrogen accumulated in the above-ground part of the silver birch stands varied between 42.4 and 145.8 kg ha⁻¹, the amount of phosphorus, between 5.9 and 27.9 kg ha⁻¹, and the amount of potassium, between 7.2 and 78.6 kg ha⁻¹. The N:P:K ratios for the foliage were comparable. It is evident that the proportion of nitrogen and phosphorus are close to optimum, while the N:K ratio was lower than optimum value in all cases.     

High dry matter whole-plant corn as a biomass feedstock

This research investigated the harvest, ambient pre-treatment, and storage of whole-plant corn as an alternative to conventional systems where corn grain and stover are fractionated at harvest. Harvesting the whole-plant, both grain and most of the above ground stover, after physiological maturity can reduce the intense logistics challenges typically associated with corn harvest and expand the harvest window. To determine the feasibility of the proposed system, corn was harvested at 350–840 g kg⁻¹ whole-plant dry matter (DM) using a forage harvester and then ensiled in pilot-scale silos. Ambient pretreatment during storage was investigated using both dilute acid and lime. Both pretreated and control whole-plant silages were very well conserved during anaerobic storage with DM losses generally less than 40 g kg⁻¹. Hydrodynamic separation of the grain and stover fractions after storage was found to be more effective at fractionating starch and fiber than conventional dry grain harvest, and both fractions had desirable composition. The effects of pretreatment on the silage were very pronounced at 30 and 100 g (kg DM)⁻¹ sulfuric acid loading with less than 100 g (kg DM)⁻¹ of the hemicellulose still bound in the cell wall at DM contents greater than 500 g kg⁻¹. The whole-plant harvest and storage system was shown to be a viable alternative to conventional corn grain and stover systems for producing feedstocks for biochemical conversion.