Article

Cassava stem wastes as potential feedstock for fuel ethanol production: A basic parameter study

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Abstract

The cassava stem is found to be one of few crop residues containing starch (up to 42% of dry mass) that may be converted to fuel ethanol. The current study was to evaluate the influence of parameters genotype, growth location and harvest time on cassava stem starch contents and yields as well as consequences in ethanol production (non-cellulosic process), based on 180 samples from a full factorial design experiment (3 varieties × 3 locations × 5 harvest times) in Guangxi, China. The potential utilization of stem starch and soluble sugar that varied 14–42% and 3–12.1% of dry mass, respectively, can correspond to an increase of 26% in ethanol production compared to that produced by roots only. The cassava stem starch content was significantly affected by all three studied parameters and location had the largest effect followed by variety and harvest time, while the stem starch yield was significantly affected by location only. The starch and soluble sugar content were significantly correlated with soil properties, e.g., soil pH and organic carbon, S and P contents. A general and positive correlation was also found between the stem and root starch, suggesting a promising potential of using stem starch without reducing root starch production.

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... Cassava products are heavily consumed in Nigeria thus food security entails that the wastes constitute the major theme of cassava bio-energy potential. The cassava stems constitute a major agricultural residue of high bio-energy content; cassava stems have up to 30% starch content of dry mass [18] or even up to 42% according to a more recent study [19]. Rural dwellers have been seen using dry cassava stems as firewood (a rather inefficient method of utilization) while the leftover is abandoned in the wild. ...
... Some rural dwellers use dry cassava stems as firewood while the left over is abandoned in the wild in both rainy and dry seasons. Studies on bio-energy production from cassava stems, which include [19,48,49,51], are scanty. The works [19,51] studied simultaneous production of bio-ethanol from the starchy and lignocellulosic components of cassava stems. ...
... Studies on bio-energy production from cassava stems, which include [19,48,49,51], are scanty. The works [19,51] studied simultaneous production of bio-ethanol from the starchy and lignocellulosic components of cassava stems. The work [49] studied the separate biogas potentials of the starchy stem waste water and the lignocellulosic stem residue and reported a global potential of about 1.0×10 Nm (≡36PJ) 9 3 and 3.2×10 Nm (≡113PJ) 9 3 of biogas (97% methane) for the former and later, respectively. ...
... [14]. After harvesting, the roots from the cassava plant have become an essential food resource for as many as one billion people in rural areas of Africa, Asia and Latin America, but the Cassava stalk is currently being wasted and not utilized properly [15]. The stems are removed as waste that is usually wasted or incinerated; only 10 to 20 percent is used for fertilizer application, cultivation development, or mushroom substrates [15]. ...
... After harvesting, the roots from the cassava plant have become an essential food resource for as many as one billion people in rural areas of Africa, Asia and Latin America, but the Cassava stalk is currently being wasted and not utilized properly [15]. The stems are removed as waste that is usually wasted or incinerated; only 10 to 20 percent is used for fertilizer application, cultivation development, or mushroom substrates [15]. Internationally, on the basis of a stem/root weight ratios of 42-50 percent [16,17] and estimated cassava root production in 2009-2013 [15], the number of cassava stems can be estimated to be about 32-38 Teragram dry mass. ...
... The stems are removed as waste that is usually wasted or incinerated; only 10 to 20 percent is used for fertilizer application, cultivation development, or mushroom substrates [15]. Internationally, on the basis of a stem/root weight ratios of 42-50 percent [16,17] and estimated cassava root production in 2009-2013 [15], the number of cassava stems can be estimated to be about 32-38 Teragram dry mass. The lack of understanding and consistency variance of the cassava stalk renders the feedstock an insignificant asset to date. ...
Article
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Many researchers focussed on the implementation of renewable energy sources with appropriate energy conversion technologies to replace conventional systems and overcome environmental issues. Among the various technologies used for producing thermal energy from biomasses without serious environmental impact, the thermochemical conversion process is considered as the viable one. Cassava is an important crop that is cultivated in the open region and also as an intercrop annually. A minor portion of the stalk is used as a source for the next cultivation and the major portion is dried and used for household cooking. Hence, in this paper, an experimental study is to be carried out on a cassava stalk and the gasification potential has been investigated. The composition, gas yield, higher heating value, temperature profile, and the efficiency of the gasifier has been studied. The result shows that the HHV and gas composition are 5.83 MJ/Nm ³ , and compositions of CO, H 2 , CH 4 , and CO 2 are 20-23%, 10-14%, 2.0-2.7%, and 15-18% respectively. All the observed results are better when the gasifier is operated with equivalence ratio (ER) 0.3. Moreover, the average producer gas yield, CO 2 /CO ratio, and conversion efficiency are observed as 1.7 Nm ³ /kg, 0.65, and 78.73% respectively.
... Only 10-20% of CS are used for propagation [7]. Cassava stem may be converted to biochar for sorption of MG. ...
... Thirty milliliters of MG solution (50 mg/L) was agitated with 0.050g CSB at 100 rpm for 10 minutes, using a Multi-Function Rotator at various initial pH of the MG solutions (i.e., 3,4,5,6,7,8,9). The solution pH was adjusted using 0.1 M sulfuric acid (H 2 SO 4 ) and 0.1 sodium hydroxide (NaOH). ...
Article
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Cassava stem biochar (CSB) was produced by pyrolyzing CS at 500°C for 2 hours at nitrogen environment. Proximate and ultimate analyses were conducted on CS and CSB. Batch sorption experiment on synthetic MG wastewater was optimized for the sorbent dosage, MG solution pH and contact time. Sorption data was analysedwith linearized sorption kinetic and linearized isotherm models. Pyrolysis of CS produced carbon-rich and stable CSB with a yield of 11.94%. The optimum sorption sorbent dosage, MG solution pH and contact time are 1.67 g/L, > pH 7.4 and 10 minutes respectively. The sorption of MG by CSB was best described by the pseudo-second-order kinetic model and the Langmuir isotherm model. The Langmuir sorption capacity of CSB was 40.5 mg/g. Monolayer of MG molecules formed chemical bonds on the homogenous surface of CSB.
... Pattiya (2011) characterized the cassava wastes used as fuel in Thailand and classified the stalks and seed stem as residues, characterizing them physically and chemically. Wei et al. (2015) discussed the possibility of extracting starch from cassava branches for producing ethanol and also evaluated aspects such as the production origin region. Veiga et al. (2016) sought to quantify and characterize cassava harvest residues by thermogravimetric analysis in oxidizing and inert atmospheres for studying the residues behavior as biofuel. ...
... Wang et al. (2012) used wet explosion pretreatment for enhancing methane production from energy crops, such as cassava and other agricultural residues. The results showed an increase in the sugars release after pretreatment, but not implying at higher methane yield (Wei et al., 2015). ...
Article
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Bioenergy production from biomass and agricultural wastes has gained significant interest due to rising fossil fuel prices and their decrease in air pollutant emissions. This review paper evaluates the state-of-art for the several applications from cassava harvest residues and their use in bioenergy industry, using different thermochemical and biochemical processes. Regarding the great available literature for this biomass, several pretreatment techniques, including mechanical, chemical, biological, thermal, ultrasonic and wet explosion were observed. The use of cassava harvest residues for the biochemical pretreatments, for example, hydrolysis, fermentation and thermochemical processes, such as direct combustion, gasification, pyrolysis, fast pyrolysis and oxy-fuel combustion was also discussed. Therefore, studies are necessary in order to understand that the use of cassava residues in thermal processes can increase the viability of this feedstock for biofuels production and/or in power co-firing units. After extensive study, it was observed that informations are still lacking about the use of cassava harvest residues in other conversion processes, thus, new studies to discover more on the use of this biomass, in order to extend their application in the bioenergy market is encouraged.
... The CB has a high concentration of fibers and starch (approximately 70% of the total composition, with starch content between 40-60%) and small amounts of other components, such as ash, proteins and lipids [1,5]. Due to this high concentration of starch, several researchers have studied the bioconversion of CB into biofuels [6,7], polysaccharides [8,9], organic acids, pigments, among others [10]. In most of the cases, the studies aim to transform or degrade the starch, resulting on the development of new products. ...
... U mg -1 ) were tested for CD production in a reactor of 50 mL and the best reaction condition was assessed. 6 The concentration of 0.05% (v/v) enzyme and reaction time of 12 h were selected. ...
Article
Cassava bagasse (CB) is an agroindustry residue usually discarded by starch industries. In this study, CB was used as a substrate to produce cyclodextrins (CDs), due to the high carbohydrate content (62%). The influence of CB concentration (2‐4%) and temperature (60‐70°C) on the production of α, β and γ‐CD was verified by means of the CGTase Toruzyme® enzyme. Higher CD production (8.61 mM) was observed for 4% CB at 70°C. The CB performed similar or better in the CD production and conversion rates when compared to cassava dextrin (CM), the mainly substrate used for CD production. The addition of 10% ethanol to the reaction medium containing CB doubled the conversion rate to 48.5%. Therefore, CD production with CB can solve the problem of discarding this residue, allowing the production of CDs with lower costs, and can generate additional income for cassava starch industry.
... That result was attributed to the possible presence of easilyhydrolysable glucans. In line with that, it was recently reported that cassava stems have a high starch content, for some varieties up to 42% of the dry weight, which can vary with both biotic and abiotic parameters such as genotype (variety), and growth environment (Wei et al., 2015). The high content of starch and woody nature of cassava stems distinguish this material from other raw materials for producing ethanol through either the conventional starch-based route (i.e., 1G ethanol) or emerging lignocellulose-based technologies (2G ethanol). ...
... The glucan content was above 50% for all five samples, and it surpassed 60% in two of them. The high glucan content was due to a high starch contribution, especially in the variety SC205, which is in good agreement with previous results (Wei et al., 2015; Zhu et al., 2015). Starch represented 18.5–42.4% of the dry weight of the stems and 35.2–67.0% of the quantified glucan. ...
Article
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Chemical characterization of cassava stems from different origin revealed that glucans accounted for 54–63% of the dry weight, whereas 35–67% of these glucans consisted of starch. The cassava stems were subjected to a saccharification study including starch hydrolysis, pretreatment with either sulfuric acid or 1-ethyl-3-methylimidazolium acetate ([Emim]OAc), and enzymatic hydrolysis of cellulose. Starch hydrolysis prior to pretreatment decreased sugar degradation, improved enzymatic convertibility of cellulose, and increased overall glucan conversion. Glucan recovery after pretreatment of starch-free cassava stems (SFCS) was around 85%, but below 52% when the stems were pretreated under the same conditions without preparatory starch hydrolysis. The total amount of hydrolyzed glucan after cellulose hydrolysis was two-fold higher for pretreated SFCS than for directly pretreated stems. Pretreatment with [Emim]OAc resulted in 20% higher glucan conversion than pretreatment with acid. Pyrolysis-GC/MS, X-ray diffraction, CP/MAS ¹³C NMR and FTIR analyses revealed major differences between H2SO4- and [Emim]OAc-pretreated material.
... Several publications examined the utilization of cassava stem (CS) for ethanol and biogas production [9][10][11][12], however, none of these reports focused on acetone-butanol-ethanol production. This is the first report to directly employ CS hydrolysate for Clostridium sp. for acetone-butanol-ethanol fermentation. ...
... Considering that CS contained 15%-34% hemicellulose and 35%-42% cellulose depending on variety and plantation area [18], the result implied that abundant glucan was absent. There was current report regarding high starch substance up to 42% of dry CS weight [10]. To hydrolyse starch, NaOH pretreatment was neglected and amylase enzymes (Termamyl ® 120 and AMG 300L TM ) were added to examine the glucan hydrolysis process. ...
Article
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This research focused on the hydrolysis of cassava stems (CS) and subsequent utilization as a carbon source for the cultivation of isolated Clostridium sp. To yield the highest amount of reducing sugars (RS), the studies on the pretreatment with sodium hydroxide (NaOH) and the hydrolysis with cellulases, amylases, and mixed enzymes were carried out. Afterwards, the hydrolysate was utilized for the cultivation of isolated Clostridium sp. Experimental results revealed that CS after 1.0 M NaOH pretreatment at 121 °C for 15 min and cellulase hydrolysis (Accellerase® 1500, 2500 CMC U/g CS) obtained 10.94 ± 0.29 g/L RS concentration. Hydrolysis of CS with amylases (Termamyl® 120, 1.2 U/g CS and AMG 300L™ 3.5 U/g CS) provided 34.85 ± 0.75 g/L RS and the maximum RS amount of 47.90 ± 0.39 g/L was obtained from the hydrolysis with mixed enzymes (Termamyl® 120, 1.2 U/g CS, AMG 300L™ 3.5 U/g CS followed by Accellerase® 1500, 2500 CMC U/g CS). From the cultivation of Clostridium sp. G10 using CS hydrolysate, the highest dry cell weight concentration of 1.28 ± 0.07 g/L was obtained with 11.68 ± 0.31 g/L butanol. It could be concluded that CS hydrolysate was comparable with glucose for utilization as a carbon source for butanol production.
... A detailed phytochemistry report and a case study on above ground carbon stocks of cassava were found elsewhere in the world. Previous studies reported that non-edible parts of cassava especially stem can be feasibly utilized for fermentable sugars and bioethanol production [7,8]. ...
Article
Cassava stem is one of the prominent lignocellulosic wastes and has potential as a feedstock for fermentable sugar production. In this study, response surface methodology (RSM) with Box-Behnken design (BBD) was employed to investigate optimum conditions for microwave assisted alkaline pretreatment of cassava stem. Effect of four variables such as reaction time (60–120 s), NaOH concentration (2–4% w/v), solid to liquid ratio (1:25–1:75 g/ml), and microwave frequency (360–720 Hz) were evaluated to improve the sugar recovery. The quadratic model indicated that, reaction time of 116.4 s, NaOH concentration of 3.21% (w/v), substrate to liquid ratio of 1:62.07 g/ml and microwave frequency of 719.86 Hz was found to be optimum and obtained a maximum yield of 43.60 μg/ml of reducing sugar and 91.71 μg/ml of xylose. Under this condition, the cellulose content of cassava stem was increased from 33.27% to 52.34%, while the hemicellulose and lignin content was decreased from 32.30% to 27.15% and 27.15% 14.59%, respectively. Moreover, to evaluate the effectiveness of the pretreatment, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis were employed on the untreated and pretreated cassava stem. These results suggest that the microwave assisted alkaline NaOH pretreatment (MAASHP) influences the fermentable sugar production significantly and further it can be utilized effectively for bioethanol production.
... Other similar residues obtained from starchy raw materials as cassava and plantain have been used for similar purposes. Different authors report the use of these residues for starch production, as dietary fiber, ethanol production, as energy source for thermochemical processes, as organic substrate for biogas production, among others (Veiga et al. 2016;Wei et al. 2015;Agama-Acevedo et al. 2016;Ilori et al. 2007;Itelima et al. 2013;Hernández-Carmona et al. 2017;Daza Serna et al. 2016). These researches corroborate the uses proposed for cocoyam in this work and increase the possible products to other options as bioenergy and biogas. ...
Article
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During last decades, there has been a growing interest of decreasing the environmental impact generated by humans. This situation has been approached from different perspectives being the integral use of raw materials as one of the best alternatives. It was estimated that 3.7 × 10⁹ tonnes of agricultural residues are produced annually worldwide. Then, the integral use of feedstocks has been studied through the biorefinery concept. A biorefinery can be a promissory option for processing feedstocks in rural zones aiming to boost the techno-economic and social growth. However, many plants produced at small scale in rural zones without high industrial use contribute with residues usually not studied as raw materials for other processes. Cocoyam (Xanthosoma sagittifolium) is a plant grown extensively in tropical regions. Nigeria, China, and Ghana are the main producers with 1.3, 1.18, and 0.9 million tonnes/year, respectively. In Colombia, there are no technified crops, but it is used where it is grown mainly as animal feed. This plant consists of leaves, stem, and a tuber but the use is generally limited to the leaves, discarding the other parts. These discarded parts have great potential (lignocellulose and starch). This work proposes different processing schemes using the parts of the plant to obtain value-added products, and their techno-economic and environmental assessment. The simulation was performed with Aspen Plus and the economic package was used for the economic assessment. For the environmental assessment, Waste Algorithm Reduction of the U.S. EPA was implemented. The obtained results showed that the integral use of plants under a biorefinery scheme allows obtaining better techno-economic and environmental performance and that small-scale biorefineries can be a promissory option for boosting rural zones.
... For example, Pattiya (2011) characterized physically and chemically the cassava (stem and stalk) residues for use as biofuel in Thailand. Wei et al. (2015) discussed the possibility of extracting the starch from the cassava branches to produce ethanol, evaluating aspects such as the production region. Veiga et al. (2016) sought to quantify and characterize the cassava residues by thermogravimetric analysis under oxidizing and inert atmospheres to study the behavior of these wastes as biofuels. ...
... The highest bioethanol concentration of 6.15 g/L was achieved for stem by direct fermentation with Rhizopus spp. The feasibility of ethanol production was studied from the three varieties of cassava stem based on three locations in China at five different harvesting times (Wei et al. 2015). The rich content of starch and soluble sugars in stem made it suitable for bioethanol production. ...
Article
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Cassava is the third significant source of calories after rice and maize in tropical countries. The annual production of cassava crop is approximately 550 million metric tons (MMT) which generates about 350 MMT of cassava solid residues, including peel, bagasse, stem, rhizome, and leaves. Cassava peel, bagasse, stem, and rhizome can be exploited for solid, liquid and gaseous biofuels production. Biofuels production from cassava starch started in the 1970s and researchers are now extensively studying cassava residues like peel, bagasse, stem, rhizome, and leaves to unravel their applications in biofuels production. However, there are technical and economic challenges to overcome the problems existing in the production of biofuels from cassava-based residues. This review provides a comprehensive summary of the techniques used for biofuels production from various cassava-based residues.
... If the yield of extractable starch of cassava stems would be comparable with the average yield of other starchy feedstocks (92.7%, Patzek, 2006), and if the hydrolysis yields would be assumed to be 90% for starch and 75% for cellulose, each ton DM (dry-matter) of cassava stem would give rise to 530 kg of glucose, which could be converted to up to 320 liters of ethanol using Saccharomyces cerevisiae as the fermenting microorganism. Wei et al. (2015) estimated that utilization of the starch from the stem could result in a 26% increase of the ethanol production compared to the volume produced using only the starch from the root. ...
... Its quantity varies according to the degree of milling, generally 5-35% starch content could be detected in rice bran (Friedman 2013;Saunders 1985). Comparatively, cassava contains starch content up to 32-42% (Ozoegwu et al. 2017;Wei et al. 2015). Soluble starch had the highest starch content (78.89%) followed by cassava (40.05%) and rice bran (36.21%). ...
Article
Lactic acid is an intermediate-volume specialty chemical, used in the production of biodegradable polymers and other chemicals. Although lactic acid production process is well established, however, the cost of production is very high. Therefore, in this study; starchy biomass (cassava) was hydrolyzed with in-house enzyme cocktail prepared from Aspergillus foetidus MTCC508 and Bacillus subtilis RA10. Process optimization using Taguchi experimental design helped to optimize the most effective ratio of fungal and bacterial amylase for effective saccharification of cassava. A higher sugar yield of 379.63 mg/gds was obtained under optimized conditions, using 30 U/gds of bacterial enzyme and 90 U/gds of the fungal enzyme at pH 4 within 48 h of saccharification. Among 11 lactic acid bacteria isolated, Lactobacillus fermentum S1A and Lactobacillus farraginis SS3A produced the highest amount of lactic acid 0.81 g/g and 0.77 g/g, respectively, from the cassava hydrolysate. The study proved the potential renewable source of cassava biomass as a source for fermentable sugars that can be fermented to lactic acid with high yield. In future, this cost-effective and environmental-friendly bioprocess can be upscaled for industrial lactic acid production.
... t (Yuan, Thompson, & Boyer, 1993). u (Wei, Zhu, Xie, Lestander, & Xiong, 2015). v (Bemiller & Whistler, 1996). ...
Article
Noodle products are widely consumed worldwide. The acceptance and preference of these functional products by consumers can be promoted through the exploration of new knowledge to enhance their formulation and quality. Starch and its modified forms are important auxiliary materials or additives for modern food processing. They are considered safe processing auxiliary materials or efficient quality improvers widely used in noodle products. In this review, the physicochemical properties and structural characteristics of native starch and its modified forms used in noodle products are introduced. The applications of native starch, chemically, physically, and enzymatically modified starches in noodle products are reviewed. The application prospects and challenges in starch and its modified forms in noodle products are presented.
... Pattiya [45] characterized cassava waste to provide information to support its use as fuel in Thailand, the author classified the stalks and seed stem (called rhizome by Pattiya) as waste and characterized them physically and chemically. Wei et al. [61] discuss the possibility to extract starch from the branches to produce ethanol, evaluating aspects as the region of production, varieties and time of harvest to find the better results. ...
Article
This study sought to quantify and characterize cassava waste as fuel. The wastes from three cultivars were collected to study and were divided into three distinct parts of the cassava plant: seed stem, thick stalks, and thin stalks. Physical and chemical analyzes were carried out to determine the elemental composition of the waste: volatile matter; fixed carbon; ash; moisture; lignin; cellulose; hemicellulose; ash composition and higher heating value were determined. We conducted a thermogravimetric analysis in oxidizing and inert atmospheres to study the behavior of the waste as fuel. The root productivity obtained ranged from 7.7 to 13.0 t ha−1 yr−1 on a dry basis (db), and the ratio between waste and roots varied from 0.36 to 0.91. The physical and chemical properties of cassava waste are analogous to those of woody biomass regarding the elemental composition, the higher heating value, and thermogravimetric analysis. Ash content varied from 2.5% to 3.5%, reaching around 6.0% in samples unwashed. Approximately 60% of the ashes are alkali oxides, especially P2O5, K2O, and CaO, which have low melting points. The alkali index calculated suggests that there is a strong tendency that the combustion process leads to ash fouling and the formation of ash deposits.
... The main energy component in cassava is starch, found mostly in the root (86-91% dry basis) (Saengchan et al., 2009). However, cassava stem and peels can also present up to 42% (Wei et al., 2015) and 60% (Souto et al., 2017;Wheatley et al., 2003) starch content (dry basis), respectively. ...
Article
The enzymatic hydrolysis of native starch lacks efficiency because starch is mostly confined in semi-crystalline granules. To address the challenges associated with gelatinization and render native cassava starch (CS) amenable to enzymatic hydrolysis (enzyme cocktail from Aspergillus awamori and Trichoderma reesei), dry-extrusion pretreatment of CS mixed with sugarcane bagasse (SB) was studied. Results showed that among the CS:SB mass ratios studied (1:1; 1:0.5 and 1:0.25), extruded CS:SB (1:0.25) gave the highest 3-hour glucose yield (71.5%) after enzymatic hydrolysis. Extrusion reduced CS:SB (1:0.25) crystallinity by 78% and increased the intensity of all major FTIR absorption bands by 67–202%. The optimum 3-hour glucose yield from extruded CS:SB (1:0.25) hydrolysis was 74.1%, which was 330% higher than from untreated CS. The water absorption and solubility indices of the treated biomass increased by 145% and 12,640%, respectively under the optimum conditions, aiding the hydrolysis process. The dry extrudates were easy to manipulate and store.
... Our observation of contiguous connection of the root and stem secondary xylem, previously only reported in swollen SR (Chaweewan & Taylor, 2015), is consistent with a distinct rhizogenesis of PSR, possibly involving a direct extension of the secondary xylem tissue of the stem, which itself accumulates starch (up to 42% of dry mass, Wei et al., 2015). Therefore, the presence of stemderived secondary xylem in PSR and not in PFR could explain why the former root type is preset to immediately activate tissue differentiation and ultimately starch accumulation. ...
Article
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Despite the importance of storage root (SR) organs for cassava and the other root crops yield, their developmental origin is poorly understood. Here we use multiple approaches to shed light on the initial stages of root development demonstrating that SR and fibrous roots (FR) follow different rhizogenic processes. Transcriptome analysis carried out on roots collected before, during, and after root bulking, highlighted early and specific activation of a number of functions essential for root swelling and identified root‐specific genes able to effectively discriminate emerging FR and SR. Starch and sugars start to accumulate at higher rate in SR before they swell but only after parenchyma tissue has been produced. Finally, using non‐destructive computed tomography measurements, we show that SR (but not FR) contain, since their emergence from the stem, an inner channel structure in continuity with the stem secondary xylem, indicating that SR derive from a distinct rhizogenic process compared with FR. This article is protected by copyright. All rights reserved.
... Despite this possibility, the non-food use of cassava root tubers in the producing belt is minimal due to their dedication to food. The utilization of cassava residues with high levels of fermentable but inaccessible sugars is a promising strategy for second-generation bioenergy production (Wei et al., 2015). This approach ensures that tubers are dedicated for food, and the stems (remaining after planting) together with the leaves (normally left to rot in the field) are used for bioethanol. ...
Article
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Cassava (Manihot esculenta. Crantz) is a starch‐rich, woody tuberous, root crop important for food, with little being done to investigate its potential as a bioenergy crop despite its enormous potential. The major bottleneck in the crop being able to serve this dual role is the competition of its storage roots for both purposes. The major cassava production regions primarily use the tuberous roots for food, and this has resulted in its neglect as a bioenergy crop. The use of non‐food cassava parts as a feedstock in cellulosic biofuel production is a promising strategy that can overcome this challenge. However, in non‐tuber parts, most of the sugars are highly sequestered in lignin complexes making them inaccessible to bacterial bioconversion. Additionally, cassava production in these major growing areas is not optimal owing to several production constraints. The challenges affecting cassava production as a food and bioenergy crop are interconnected and therefore need to be addressed together. Cassava improvement against biotic and abiotic stresses can enhance productivity and cater for the high demand of the roots for food and bioenergy production. Furthermore, increased production will enhance the usability of non‐food parts for bioenergy as the bigger goal. This review addresses efforts in cassava improvement against stresses that reduce its productivity as well as strategies that enhance biomass production, both important for food and bioenergy. Additionally, prospective strategies that could ease bioconversion of cassava for enhanced bioenergy production are explored. Cassava is very important as a food crop and has enormous potential for use in bioenergy. Majority of cassava growing regions cultivate it for food. This reviews analyses approaches that can improve cassava and make it serve a dual role of food and bioenergy.
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This review includes works published in the general scientific literature during 2015 on the production of bioenergy and biofuel from waste residues generated during bioethanol and biodiesel production with a brief overview of current and emerging feedstocks. A section of this review summarizes literature on culturing algae for biofuels including bioreactors and open pond cultivation systems with the utilization of inorganic and organic sources of nutrients. New methods applicable to the mass culture of algae are highlighted. Algal cell harvesting and oil extraction techniques tested and developed for algae discussed alongwith policies and economics are also provided.
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Cassava produces about 10 times more carbohydrates than most cereals per unit area, and are ideal for production in marginal and drought prone areas. Cassava, which originated from tropical South America, is a perennial woody shrub with an edible root, which today is grown in tropical and subtropical regions of the world where it provides energy food and serves as a veritable source of food and income for over a billion people. This handbook provides new research on the production, consumption and potential uses of cassava.
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Global warming and increasing concentration of atmospheric greenhouse gas (GHG) have prompted considerable interest in the potential role of energy plant biomass. Cassava-based fuel ethanol is one of the most important bioenergy and has attracted much attention in both developed and developing countries. However, the development of cassava-based fuel ethanol is still faced with many uncertainties, including raw material supply, net energy potential, and carbon emission mitigation potential. Thus, an accurate estimation of these issues is urgently needed. This study provides an approach to estimate energy saving and carbon emission mitigation potentials of cassava-based fuel ethanol through LCA (life cycle assessment) coupled with a biogeochemical process model—GEPIC (GIS-based environmental policy integrated climate) model. The results indicate that the total potential of cassava yield on marginal land in China is 52.51 million t; the energy ratio value varies from 0.07 to 1.44, and the net energy surplus of cassava-based fuel ethanol in China is 92,920.58 million MJ. The total carbon emission mitigation from cassava-based fuel ethanol in China is 4593.89 million kgC. Guangxi, Guangdong, and Fujian are identified as target regions for large-scale development of cassava-based fuel ethanol industry. These results can provide an operational approach and fundamental data for scientific research and energy planning.
Technical Report
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UNCTAD’s first report on the state of biofuel technologies in 2007 highlighted a sector with great potential, but at the time that was a long way off from markets. In 2015, countries made commitments toward a more environmentally balanced future through the Sustainable Development Goals (SDGs), and now seek to expand policies for low-carbon development after the agreement reached in Paris at COP21. The year also marked a milestone in the bioeconomy, as the point in time when the production of second-generation biofuels (2G) finally took off at commercial scale. Developing countries now face a new set of market opportunities and policy dilemmas to enhance their usage of biomass, which can now be transformed into more valuable products. This report focuses on how these market opportunities can be capitalized on and how to promote technology transfer for developing countries interested in engaging in advanced biofuel markets for the attainment of the SDGs, and as an instrument to meet their commitments under COP21. By carrying out a non-exhaustive mapping of cellulosic ethanol projects and recent policy lessons around the globe, this report seeks to provide public and private practitioners with a macro-picture of the advanced biofuels sector, with a specific focus on cellulosic ethanol as of 2015-2016. Second-generation biofuels can be classified either by: process type, estimated Greenhouse Gas (GHG) emissions reductions compared to the fossil-fuel equivalent, or feedstock type. This report primarily looks at feedstock choice, which concerns fuels made from non-edible feedstocks, partially in reaction to the food versus fuel debate. Nevertheless, process improvements have been a key factor in decreasing costs for the industry and allowing market expansion. Historically, the United States of America (US) has had the largest installed capacity for cellulosic ethanol production of deployed second-generation biofuel facilities, followed by China, Canada, European Union (EU) and Brazil, respectively. Projects in these countries vary significantly in their technological approaches and feedstocks used for fuel production, including the use of corn stover, sugarcane bagasse, municipal solid waste, and forestry residues, among others. One common trait is that companies that possess technology and knowledge in the EU and the US engage in partnerships to deploy advanced ethanol facilities abroad, for example, the Fuyiang project, which is a cooperation between Italy-based Beta Renewables and Guozhen Group in China. While the African continent and the entire Latin-American region (excluding Brazil) have no cellulosic ethanol projects as of 2015, progress has been made in bagasse-fired electricity cogeneration and biomass cook stoves in these regions. The policy instrument that has provided the greatest traction to advanced biofuels has been the market- segmentation strategy in conventional / advanced / cellulosic biofuels used in the US market, albeit by granting price premiums for the production of cellulosic ethanol. Low interest rates and a venture capital culture have also been tooted for advancing the deployment of second-generation biofuels in US market forward. Furthermore, the rapid growth of China in the advanced cellulosic ethanol industry, as well as strong support to the sector by the National Development Bank in Brazil, all illustrate the multiple supply and demand pull mechanisms, which have given traction to the industry globally. While installed capacities have been scaled-up over the past three years, interviews carried out during the preparation of this report suggest that actual production is much smaller than nominal capacities. This could be explained by several factors including feedstock costs, process costs, a lack of domestic regulatory frameworks favourable to advanced biofuels, risk avoidance, and blend walls in major markets. While this report has mapped production capacities, the availability of actual production data is limited as such information is treated confidentially by the industry. In the case of the US, the expected utilization of cellulosic fuels in the market Renewable Volume Obligations (RVOs) for 2015 corresponds to 400 million litres, or about 80 percent of the installed US capacity as of 2015 as surveyed in this report. Based on the limited data available, actual production data in 2014 corresponded to a utilization rate of 25 percent of the US installed capacity for cellulosic fuel. Indicating an optimistic stance, the US Environmental Protection Agency (EPA) has issued obligations that nearly double the cellulosic ethanol requirements for the US market in 2016, calling for imports to meet the likely shortfall in domestic capacity. Trade opportunities might exist in advanced biofuel markets, particularly as recent limits on conventional biofuels in Europe, together with the EU’s growing self-sufficiency in conventional biofuels, suggest that imports of advanced biofuels will most likely be made if domestic producers fail to deliver their expected output. The US is also likely to begin cellulosic ethanol imports in the years ahead, as its own official statistics suggest. Depending on future rules on advanced biofuels in important markets, potential World Trade Organization (WTO) outcomes could be similar to those raised for first-generation biofuels, which led to special sustainability requirements for biomass, and may work as indirect barriers to trade. The report concludes with five suggestions for the responsible development of the second-generation biofuels industry: • Create regulatory frameworks for advanced bioenergy tailored to national circumstances, which do not necessarily focus on the type of supply but instead on the existing local demands. The fulfilment of such regulation is most likely to meet domestic development strategies in line with the SDGs. • Promote cooperation between domestic organizations and foreign companies for joint ventures by means of investment agreements in order to facilitate technology transfer. This is important to avoid the emergence of a large technological gap between first-generation, land-intensive feedstocks and second-generation, capital-intensive biofuels in developed and developing countries. • Consider the broader aspects of bioeconomy sectors, including biomaterials, in ways that avoid locking industrial development paths into specific sectors or technologies. This would provide flexibility for market players that operate biorefineries as they could target multiple markets, including materials, feed, food, and energy - both domestic and internationally. • Incorporate lessons from sustainability criteria applied for first-generation biofuels into near and mid- term sustainability provisions or labels for advanced biofuels. • Continuously promote technical dialogue among different production regions of advanced fuels in order to ensure compatible standards for feedstock and promote trade in advanced biofuels. Advanced biofuels are an important tool to be considered in national policy in the coming decades. They are a renewable energy option with great potential help decarbonize transportation and other systems in developing countries. Advanced biofuels consequently relate to numerous SDGs and national commitments to limit climate change to tolerable levels. Their responsible development in the coming years should take into account lessons from first-generation biofuels (and other renewable energy technologies), which have received intense scrutiny in recent years. In particular, rules on trade and the sustainability aspects of advanced biofuels should be applied coherently with other regulations, both domestically and internationally.
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Process integration approaches in biorefinery are crucial for sustainable development. Research related to the sustainable production of biodegradable plastics especially polylactic acid is gaining momentum worldwide. The stereospecific nature and economic viability of the lactic acid monomer are crucial for poly (lactic acid). These surge the concepts of “green monomers” from biorefineries especially d-Lactic acid (DLA). Globally, the utilization of sustainable feedstock has been preferred as a cost-effective and eco-efficient strategy for value-added product synthesis. The underutilized agri-food industries are facing economical threats from their stakeholders, especially cassava-based industries. The development of an effective techno-economic strategy through enzyme-based greener process integration approaches will boost the economy. The enantiomeric purity of DLA is a crucial factor for its industrial applications, and the greatest demand exists for the optically pure isomers which can be achieved only by scalable enzymatic technology. DLA production could be a potential strategy for value addition for the generated cassava fibrous waste (CFW) at different stages. The objective of this case study is to address the scalability aspects of the uncherished resource potential of CFW towards enhanced DLA production by imparting enzymatic process intensification at different stages of integrated cassava biorefinery, especially in terms of hydrolysis, fermentation, and purification.
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Cassava stems are an abundant feedstock that is becoming attractive for biochemical conversion to fuels and chemicals. Since cassava stems are rich in both cellulose and starch, carefully designed pretreatment and digestion procedures are required for achieving high glucan recovery. In this study, partially de-starched cassava stems resulting from a water extraction stage were hydrolyzed with amylases, and the resulting starch-depleted material was pretreated with dilute sulfuric acid, and submitted to enzymatic hydrolysis of cellulose. The effects of acid pretreatment on glucan recovery, enzymatic convertibility, and by-product formation were investigated using a Box-Behnken experimental design with temperature (165–195 °C), time (5–35 min), and acid concentration (0.2–1.0%) as independent variables. In further experimental series, the time period was extended up to 110 min while maintaining temperature at 195 °C and sulfuric acid concentration at 0.6%. Using those conditions, pretreatment for 50 min gave the best results (83.8% enzymatic convertibility of pretreated cellulose, and ˜72% overall glucan-to-glucose conversion).
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This study aims to understand starch properties of cassava stems, currently a discarded crop residue, which contain up to 40% starch by dry mass. Granule sizes and size distribution of cassava stem starch, and their variations with genotype, growing location, and position along the stem were investigated using SEM images. Amylose contents, crystallinity, and pasting characteristics of stem and root starch were also compared. The mean of granule sizes ranged from 5.65 to 7.64 μm, depending on the environment and position along stems, but not on genotype. Stem starch has a similar granule shape, X-ray diffraction pattern, and amylose content (20.8% of starch basis) to root starch, but a significantly smaller granule size with narrower distribution range and higher pasting temperature (72.1 °C). Cassava stem has a woody nature; a development of efficient starch isolation method shall be included in future studies.
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The deep eutectic solvent of [choline chloride (ChCl)] [ethylene glycol (EG)] was demonstrated to be an effective non‐destructive solvent for starch processing. The pre‐gelatinized starch samples were prepared by its gelatinization, treatment, and re‐crystallization in this deep eutectic solvent and characterized by differential scanning calorimetry (DSC), gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (H‐NMR), X‐ray diffraction analyses (XRD), and scanning electron microscopy (SEM) tests. A simple dissolution‐recovery method was used to screen the non‐derivatizing solvent from eight candidate deep eutectic solvents. The gelatinization temperature of starch in the deep eutectic solvent of [choline chloride] [ethylene glycol] was measured using a DSC method. Compared to the native starch sample, slight increases in molecular weights and decreases in molecular weight distribution of the recovered starch samples were observed. The similar FTIR and H‐NMR spectra of the native starch and recovered starch samples suggested no reaction and variation in chemical structure during the processing. The XRD and DSC tests showed that the strong micro‐granular crystalline structure of the native corn starch was destroyed during the gelatinization and treatment in the DES while new weak crystalline structure was formed during the re‐crystallization. From the SEM pictures, the bowel‐like particles were found in the recovered starch samples and the thickness of the wall was decreased with depth of temperature quench. This article is protected by copyright. All rights reserved
Article
The subcritical liquid hot water (SLHW) pretreatment could be strengthened by its byproduct-organic acids, such as acetic acid (AA), lactic acid (LA) and formic acid (FA). The effects of these three acids on the pretreatment were investigated by the yield of fermentable sugars. The results showed that the addition of acids could effectively catalyze the hydrolysis of hemicellulose to C5 sugars and contribute to the subsequent enzymatic hydrolysis of cellulose. It was found that all three organic acids promote xylose production, and the copresence of AA + LA could limit the content of the fermentation inhibitor. The optimum proportion of three organic acids were 0.33 wt%AA + 0.45 wt%LA + 0.20 wt%FA, and the yield of C5 sugars after pretreatment and C6 sugar after enzymatic hydrolysis were 89.06% and 78.56%, respectively. The kinetic studies proved that byproduct-organic acids could promote xylose production and inhibit its further degradation and explained that xylose would accumulate at lower temperatures.
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In recent years, the production of value-added products from lignocellulosic biomass has gained significant interest due to economic and environmental reasons (Limayem and Ricke 2012). Bioethanol is generally produced by fermenting the sugar components of biomass such as rice straw (Wang et al. 2015; de Assis Castro et al. 2017), wheat straw (Moreno et al. 2016, Nielsen et al. 2017), sugarcane bagasse (Soares et al. 2016; Antunes et al. 2017), sugarcane tops (Sindhu et al. 2014), sugarcane juice (Zabed et al. 2014), cotton stalk (Singh et al. 2017), cotton gin waste (Chandrasekaran and Sivamani 2018), bamboo (Yang et al. 2014; Xin et al. 2015), and lignocellulosic, and other waste biomass as carbon sources (Gupta and Verma 2015; Al Azkawietal. 2018). Among them, cassava-based materials are a cheaply available lignocellulosic waste in huge quantities in developing countries.
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Plant food waste is an important biomass source that can be used for bioenergy production. Its physical and chemical properties vary widely depending on the type of plant, and collection and conditioning methods. The food wastes include field residues, food processing wastes, and food leftovers from homes and food preparation and service businesses. In this chapter, the characteristics of different plant food wastes are presented. Various methods and technologies for food waste collection and storage are introduced. The operational concepts and the performance of different processes applied for the bioenergy production are described. The processes include anaerobic digestion for biogas production; fermentation processes for alcohol production, physicochemical processes for biodiesel production; and thermochemical and hydrothermal processes for the production of biooil, syngas, and biochar.
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Thermal energy generation from biomass fuels usually leads to dense slag accumulation, causing combustion system problems. This study tested a type of local clay as a slag soothing additive on two biomass fuels: Acacia mangium (kratin-tree) and Manihot esculenta (cassava). Physical characteristics of the slags were studied. In addition, a laboratory method for determination of ash sintering was modified to assay the dense and loose slag accumulation. Compositions of the clay and biomasses were determined. While the clay contains high relative contents of Si (42.3%) and Al (24.5%), the cassava rhizome and kratin-wood contain high relative contents of K (46.8% and 47.2%) and Cl (10.8% and 7.54%), respectively. Gas phase transition of residual ashes was revealed as a result of slag inducing combustion treatments. Addition of the clay (0–5%) decreased the total slag accumulation, and the maximum effect was revealed at 3–5% clay. The modified method in this study requires a small amount of ash sample which is practical and convenient for laboratory testing of slag behavior.
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Integrated processes of whole plant cassava bioethanol production using full components including cellulosic C5 sugar are proposed. The impacts of different utilization patterns of cellulosic C5 sugar on bioethanol production are investigated by life cycle assessment. Results show that for cassava straw bioethanol, process using cellulosic C5 sugar performs better, and the NER, renewability and GWP (global warming potential) are 0.94, 1.09 and 2929 kg CO2 eq. The integrated process WPC-2 that the cellulosic C5 sugar mash is fermented together with the cassava starch, is a better cellulosic C5 sugar utilization pattern with NER 1.49, renewability 2.20 and GWP 1579 kg CO2 eq. The process WPC-2 shows the potential to approach cassava bioethanol in terms of energy and environmental emissions. The downstream products are investigated and the E85 fuel from WPC-2 has higher application potential.
Article
As a by-product of cassava roots, cassava stems contain up to 40% starch (by dry mass) and are currently discarded as agricultural waste. The current study aims to further understand the physicochemical traits of both the cassava stem and root starches and provide data that are necessary for investigating trends in industrial cassava applications. In total, 11 traits of both cassava stem and root starches of 15 genotypes were investigated. The results showed that all the examined traits of cassava root and stem starches varied by genotype. The amylose contents of root and stem starches were in the range of 19.0%–33.0% and 18.44%–34.51%, respectively. The RS of root and stem starches were in the range of 1.72%–17.72% and 4.42%–13.37%, respectively. A paired t-test indicated that only the starch content, solubility, and swelling power of root starches were significantly higher than those of stem starches among 15 genotypes (df = 14, P < 0.05). The root starch gel was more stable than the stem starch gel after the fourth and fifth freeze-thaw cycles. Furthermore, principal component analysis calculated based on starch and amylose contents, degree of swelling, digestibility, and freeze-thaw stability were conducted. The results demonstrate that five genotypes GW46, GW88, S1, E26, and GC49 gained higher scores than the control varieties South China 12 and South China 205, which are the most favourable ones by farmers in China because of good root yields.. This article is protected by copyright. All rights reserved
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Cassava anthracnose disease (CAD), caused by Colletotrichum gloeosporioides f. sp. manihotis infection, is a major disease of cassava (Manihot esculenta Crantz). The objective of this study was to identify proteins differentially regulated in resistant (‘Huaybong 60’) and susceptible (‘Hanatee’) cultivars in response to C. gloeosporioides f. sp. manihotis infection. Total proteins were extracted and resolved via 2-dimensional gel electrophoresis. Fourteen differentially expressed proteins were identified in ‘Huaybong 60’, of which eight were up-regulated and seven down-regulated. In ‘Hanatee’, seven proteins were identified, of which one was up-regulated and six were down-regulated. Proteins associated with carbohydrate metabolism were down-regulated, whereas reactive oxygen species-generating and cyanogenic pathways were up-regulated in the resistant cultivar. This study provided new insights into the mechanisms underlying pathogen resistance in cassava and suggested that pathogen resistance might arise from an integrated mechanism that arises from only a few initiating events.
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Most prior studies have found that substituting biofuels for gasoline will reduce greenhouse gases because biofuels sequester carbon through the growth of the feedstock. These analyses have failed to count the carbon emissions that occur as farmers worldwide respond to higher prices and convert forest and grassland to new cropland to replace the grain (or cropland) diverted to biofuels. By using a worldwide agricultural model to estimate emissions from land-use change, we found that corn-based ethanol, instead of producing a 20% savings, nearly doubles greenhouse emissions over 30 years and increases greenhouse gases for 167 years. Biofuels from switchgrass, if grown on U.S. corn lands, increase emissions by 50%. This result raises concerns about large biofuel mandates and highlights the value of using waste products.
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Cassava (Manihot esculenta Crantz) is the second most important staple food crop in sub-Saharan Africa, providing upto 285 calories per person per day. Cassava starch is a potentially important industrial material in Malawi. Industries hesitate to use cassava starch because the powder sold by some suppliers has been grossly inadequate. This study was conducted to evaluate native cassava starch qualities for different Malawi cassava genotypes, determine the appropriate stability parameter to deal with GxE for starch quality traits, and potential for use of cassava starch by the main industries in Malawi. Trials were conducted in Malawi to examine starch quality parameters, root dry mater and starch extraction. Based on the results, the moisture and ash content were much lower than the recommended allowable maximum. The pH for cassava starch was within the recommended range. Additive main effects and multiplicative interaction (AMMI) were strongly correlated with other stability parameters such as Wi-ecovalence and stability variance–no covariate. From the results, genotype has a greater influence on root dry matter than the environment. Native cassava starch can be used in the pharmaceutical, battery and packaging material making and textile industries in Malawi.
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Given the growing global population, mankind must find new ways to lower competition for land between food and fuel production. Our findings for cassava suggest that this important crop can substantially increase the combined production of both food and fuel. Cassava stems have previously been overlooked in starch and energy production. These food-crop residues contain about 30% starch (dry mass) mostly in the xylem rather than phloem tissue. Up to 15% starch of the stem dry mass can be extracted using simple water-based techniques, potentially leading to an 87% increase in global cassava starch production. The integration of biofuel production, using residues and wastewater from starch extraction, may bring added value. The cassava roots on which biofuels and other products are based can be replaced by cassava stems without land use expansion, making root starch available as food for additional 30 million people today.
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In contrast to a few years ago, when cellulosic ethanol via enzymatic hydrolysis was the only widely recognized technology for commercially producing cellulosic biofuels, a diversity of approaches are currently under commercial development. While no commercial-scale (≥20 million gallons per year) cellulosic biofuel facilities are operating at present, at least ten biorefinery projects employing six different pathways are expected to begin operations by 2014. These biorefineries will employ the following pathways: (i) catalytic pyrolysis and hydrotreating to hydrocarbons; (ii) gasification and Fischer-Tropsch synthesis to hydrocarbons; (iii) gasification and methanol-to-gasoline synthesis; (iv) dilute acid hydrolysis, fermentation to acetic acid, and chemical synthesis to ethanol; (v) enzymatic hydrolysis to ethanol; and (vi) consolidated bioprocessing (single-step enzyme production, hydrolysis, and fermentation) to ethanol. This review provides an overview of the six pathway technologies, comprehensive descriptions of each of the ten biorefinery projects, and a discussion of the current direction of cellulosic biofuel commercialization efforts and its implications for the revised Renewable Fuel Standard.
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The influence of age on tuber yield, dry matter content, cooking quality and flour, gari and starch yield were studied on 4 cassava accessions (DMA-002, WCH-037, NKZ-009 and NKZ-015) at six selected locations in the Forest and the Transition ecozones of Ghana in 2004/2005. The aim was to determine the effect of age, variety and location on agronomic and processing characteristics of cassava genotypes at the Forest and the Transition ecozones of Ghana. Data were collected for the tuber yield, dry matter content, cooking quality, flour, gari and starch yields. Planting was done at 1x1 m with each genotype occupying half of an acre to facilitate continuous harvesting and for large tuber samples of 25 kg to be processed into flour, gari and starch. Harvesting which began at 12 months after planting was continued monthly until 15 months of age. Tuber yield of the genotypes was generally higher in the Transition than the Forest. In addition, DMA-002 and WCH-037 produced the higher tuber yield than the NKZ-lines in the Transition belt but not in the Forest ecozone. Genotypes did not only vary in dry matter content at the two ecozones but also the age at harvest. Cooking quality of the DMA-002 and WCH-037 was better than the NKZ-lines. Obtained results revealed that the optimum age for root tuber yield did not coincide with that of the flour, gari and starch. Similar observation was made between the starch flour and gari.
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The U.S. Department of Energy (DOE) and the U.S. Department of Agriculture (USDA) are both strongly committed to expanding the role of biomass as an energy source. In particular, they support biomass fuels and products as a way to reduce the need for oil and gas imports; to support the growth of agriculture, forestry, and rural economies; and to foster major new domestic industries-- biorefineries--making a variety of fuels, chemicals, and other products. As part of this effort, the Biomass R&D Technical Advisory Committee, a panel established by the Congress to guide the future direction of federally funded biomass R&D, envisioned a 30 percent replacement of the current U.S. petroleum consumption with biofuels by 2030. Biomass--all plant and plant-derived materials including animal manure, not just starch, sugar, oil crops already used for food and energy--has great potential to provide renewable energy for America s future. Biomass recently surpassed hydropower as the largest domestic source of renewable energy and currently provides over 3 percent of the total energy consumption in the United States. In addition to the many benefits common to renewable energy, biomass is particularly attractive because it is the only current renewable source of liquid transportation fuel. This, of course, makes it invaluable in reducing oil imports--one of our most pressing energy needs. A key question, however, is how large a role could biomass play in responding to the nation's energy demands. Assuming that economic and financial policies and advances in conversion technologies make biomass fuels and products more economically viable, could the biorefinery industry be large enough to have a significant impact on energy supply and oil imports? Any and all contributions are certainly needed, but would the biomass potential be sufficiently large to justify the necessary capital replacements in the fuels and automobile sectors?
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Global climate issues and a looming energy crisis put agriculture under pressure in Sub-Saharan Africa. Climate adaptation measures must entail sustainable development benefits, and growing crops for food as well as energy may be a solution, removing people from hunger and poverty without compromising the environment. The present study investigated the feasibility of using non-food parts of cassava for energy production and the promising results revealed that at least 28% of peels and stems comprise dry matter, and 10 g feedstock yields >8.5 g sugar, which in turn produced >60% ethanol, with pH ≈ 2.85, 74-84% light transmittance and a conductivity of 368 mV, indicating a potential use of cassava feedstock for ethanol production. Thus, harnessing cassava for food as well as ethanol production is deemed feasible. Such a system would, however, require supportive policies to acquire a balance between food security and fuel.
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The potential of dilute-acid prehydrolysis as a pretreatment method for sugarcane bagasse, rice hulls, peanut shells, and cassava stalks was investigated. The prehydrolysis was performed at 122 degrees C during 20, 40, or 60 min using 2% H(2)SO(4) at a solid-to-liquid ratio of 1:10. Sugar formation increased with increasing reaction time. Xylose, glucose, arabinose, and galactose were detected in all of the prehydrolysates, whereas mannose was found only in the prehydrolysates of peanut shells and cassava stalks. The hemicelluloses of bagasse were hydrolyzed to a high-extent yielding concentrations of xylose and arabinose of 19.1 and 2.2 g/L, respectively, and a xylan conversion of more than 80%. High-glucose concentrations (26-33.5 g/L) were found in the prehydrolysates of rice hulls, probably because of hydrolysis of starch of grain remains in the hulls. Peanut shells and cassava stalks rendered low amounts of sugars on prehydrolysis, indicating that the conditions were not severe enough to hydrolyze the hemicelluloses in these materials quantitatively. All prehydrolysates were readily fermentable by Saccharomyces cerevisiae. The dilute-acid prehydrolysis resulted in a 2.7- to 3.7-fold increase of the enzymatic convertibility of bagasse, but was not efficient for improving the enzymatic hydrolysis of peanut shells, cassava stalks, or rice hulls.
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The influence of growth location, variety, and harvest time on ash composition and calorific value of cassava stems was evaluated using 180 samples from a full factorial-designed experiment (three locations x three varieties x five harvest times) in Guangxi, China. The calorific value of cassava stems showed only small variations (<3%). However, the ash content and ash-forming elements, such as P, Cl, S, K, Ca, and Mg, varied significantly with location, variety, and harvest time. A ternary diagram analysis of major elements indicated cassava stems had rather high ash-fusion temperatures (>1500 degrees C), which was consistent with our published results(18,19) and suggested limited sintering during combustion, if any. K and Cl contents varied the most and did so significantly between locations (growth environments), which was attributed to differences in soil composition. On the basis of theoretical and empirical indices of molar ratios, cassava stems across all treatments generally exhibited a risk of particle emissions when combusted but stems from one location (Heng) could have much better combustion behavior than those from others in terms of slagging and corrosive Cl-rich deposit tendencies indicated by the indices K/(Ca + Mg) and combinations of S/Cl and Cl/(K + Na), respectively. Stems from Wuming showed a higher risk for the induction of particle emission, according to the index (K + Na + Ca + Mg)/(P + Si), while biomass from Longan and the variety Xinxuan048 tended to show risk of forming corrosive Cl-rich deposits.
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Cassava South China genotype cultivars were released by Chinese Academy of Tropical Agricultural Sciences and their physicochemical traits had been described. However, the physicochemical traits of these cultivars affected by environmental factors were poorly understood. This study aimed to investigate the effects of interrelationship between genotypes and environments (G and E) on physicochemical traits of cassava roots and starches. Fourteen quantitative characteristics were assessed in seven genotypes grown in eight locations in China. The influences due to G and E upon the physicochemical traits of cassava roots and starches were evaluated using the general linear models procedure. The results indicated that the examined traits could be significantly affected by the factors of G and E, and the different contribution of G and E to total variation was evidenced. A most important economic trait dry matter content, ranging from 18.3 to 31.9% during seven genotypes, was negatively correlated to rainfall in cassava growing environments, but insignificantly correlated to temperature. Average starch granule sizes ranged between 9.5 and 12.7 µm. Granules were mainly truncated in shape and similar across all cultivars, and were insignificantly affected by rainfall and temperature. Significant correlations were observed among starch properties including paste clarity and viscosity, which was positively correlated to granule surface area. Principal component analysis demonstrated that SC8 is the best genotype suited for industrial applications and all cassava genotypes responded differently in various environmental climate conditions for the examined traits.
Article
New biofuel raw materials for energy pellet production are now being studied as potential energy sources for the heating market. Because of the complexity of the chemical and physical properties of novel fuels, such as some agricultural residues and energy crops, the study of their ash-related aspects is crucial for the sustainable development of this potential energy sector. Ash fractions formed during fixed-bed combustion of different pelletized novel crops; i.e., two Mediterranean crops (one herbaceous, brassica, and one woody species, poplar) and three Chinese cassava stems (cassava species from three different Chinese regions), and three Chinese cassava stems (cassava species from three different Chinese regions), were characterized, and their formation paths assessed in this study. Special emphasis was placed on elucidating the role of major ash-forming elements in the fractionation and transformation behavior, leading to the formation of bottom ash, deposits, and particulate emissions (fine and coarse ash particle fractions) on the basis of experimental data. In the Mediterranean fuels, the predominant ash fraction obtained was bottom ash, mainly characterized by silicates. Phosphates were found to be the main crystalline phases in the Chinese fuels. The slagging tendency was low for all of the fuels, although more significant for the cassava species under the studied conditions. Further, combustion of the studied Chinese energy crops resulted in a considerably finer particle fraction compared to the Mediterranean fuels. Deposits and particulate matter were dominated by K-sulfates as well as K-chloride in all fuels (except poplar), with the occurrence of K-phosphates for cassava pellets. Overall, this study showed fundamental differences in ash transformation behavior during combustion of P-rich fuels (i.e., cassava mixtures) compared to Si-rich fuels (i.e., poplar and brassica mixtures). Of major importance is the experimental verification of the higher thermodynamic stability of phosphates in relation to silicates. Furthermore, in P-rich fuels at high (K + Na)/(Ca + Mg) ratios, a significant degree of alkali metal volatilization occurs, which forms larger amounts of particulate matter, whereas this ratio has no/low effect in Si-rich fuels at high alkali metal ratios.
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Knowledge of biomass properties and/or fuel characteristics is the basis for bioenergy or chemical conversion processes. Biomass properties are variable and associated with plant species and assortments, therefore, identifying the associations will be important for understanding mechanisms behind the variations and for improvements in predicting biofuel characteristics and management of sustainable feedstock production. A data synthesis was carried out based on data of energy properties including contents of carbon (C), hydrogen (H), oxygen (O), nitrogen (N), sulfur (S) and ash (A) (CHONSA) in variable biomass species and assortments. Data were collected from 260 peer-reviewed literatures and composed of 742 data objects of more than 144 species.
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A study was carried out based on ash composition data (relative proportion of SiO2, K2O, CaO, MgO, Na2O, P2O5, Al2O3, Fe2O3 and SO2 in ash) in a large number of biomass species and assortments. The data were collected from 109 peer-reviewed publications and consisted of 367 objects for ash composition analysis. Principal component analysis (PCA) was used to analyze the data. The analyses were performed at five levels of plant classifications respectively: level 1–3 for life-forms/species groups, level 4 for assortments and level 5 for species.
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The major carbohydrates of rice straw samples were determined in order to evaluate the potential of using rice straw as a feedstock for ethanol production in Japan. Straw samples were harvested by cutting the plants at ground level when the grain was mature and immediately heating or chilling the samples. In all cases, significant amounts (62–303 g kg−1) of soft carbohydrates defined as consisting of glucose, fructose, sucrose, starch and β-1,3-1,4-glucan were detected, in addition to structural carbohydrates (cellulose and xylan). These results indicate that rice straw is a rich source of fermentable sugars from both soft carbohydrates and lignocellulosic portions of the cell wall.
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Development of biofuels from renewable resources is critical to the sustainability of the world's economy and to slow down the global climate change. Currently, a significant amount of bioethanol and biodiesel are produced as biofuels to partially replace gasoline and diesel, respectively, in the transportation sector worldwide. However, these biofuels represent a tiny portion (<4%) of the total fuels consumed. Furthermore, bioethanol is produced predominantly from sugarcane and corn, and biodiesel from crop and plant oils. Production of these raw materials is competing for the limited arable land against food and feed production. It is not feasible to tremendously increase biofuel production using the current technologies. Therefore, it is critical to investigate advanced or 2nd generation biofuel production technologies. This article is trying to summarize the current status of the 2nd generation biofuel technologies including bioethanol from lignocellulosic materials and biodiesel from microalgae. The summary includes the descriptions of the technologies, their advantages and challenges, feedstocks for the 2nd generation biofuels, the key barriers to their commercial applications, and future perspectives of the advanced technologies.
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A rapid near-infrared (NIR) spectroscopy method was established to predict the lignin and starch contents and enzymatic saccharification efficiency of transgenic rice (Oryza sativa cv. Nipponbare) straw wherein expression of genes encoding lignin synthetic enzymes are regulated. Strong correlations were obtained between laboratory wet chemistry values and the NIR-predicted values. This method is useful to develop transgenic rice where cell-wall formation is engineered. © 2012 The Japanese Society for Plant Cell and Molecular Biology.
Article
The nutritional content of cassava (Manihot esculenta Crantz) stems changed with different levels of soil fertility. These changes affected the quality of stakes (planting material) obtained from these stems, which, in turn, affected yields of subsequent crops. According to the five levels of fertilization used, mother plants had different heights and vigor, and stems produced stakes of different weights. Both the concentration and content of N, P, and K in the stems varied with fertilization treatment, being least with no nutrients applied to the soil. Sprouting rate was strongly influenced by the N, P, and K contents in the stakes. The lowest sprouting rate occurred with stakes that received no K, but moderate levels of N and P. Sprouting potential was not affected by planting stakes in fertilized or unfertilized soils, however, indicating that nutritional reserves contained in the stakes was more important. Stakes from plots with moderate level of N, P, and K application resulted in plants that had the greatest leaf area, foliage and stems suited as propagation material. Plants produced from these stakes also had the highest total root yield and highest production of commercial roots in both fertilized and unfertilized soils. The increase in yield in the subsequent crop attributed to stake quality was more than the increase due to fertilization.
Article
Impact of environmental conditions on cassava starch variability was examined by studying four commercially important cultivars, Rayong 1, Rayong 60, Rayong 90, and Kasetsart 50 (KU 50). Age of the root and environmental conditions at harvest influenced granule structure and hydration properties. All cultivars were grown under identical field conditions, and harvested at different times. Starches extracted from cassava roots harvested at different times were characterised by unique starch granule structure and function. Apparent amylose size of starches from all cultivars did not change significantly during the trial period. However, apparent amylose content of starches changed, decreasing in the older roots. Granule size distribution was affected by age of the root, gradually changing from normal to bimodal distribution when harvested very late during the trial. The integrity and crystalline structure of starch granules also depended on the environmental conditions, evidenced as a change in peak profile obtained by thermal analysis. This can result in the difference in water uptake of starches, and their consequent swelling power and gelatinization. Pasting temperature of all starches increased during the dry period, and was lowered during the wet period. Peak and final viscosity of starch decreased from early to mid-harvest time when environmental conditions became drier, and increased close to or greater than the original value when conditions became wet again. Breakdown and setback also followed a similar trend to viscosity. This study suggests an impact of time and conditions of harvest on the structural and functional properties of all cassava cultivars, and based on this study, it is recommended that starch should be extracted from either early or very late harvested roots.
Article
The geographic variations in corn stover fuel and soil characteristics from 22 sites in the Kerchin region (43.8–45.0°N, 122.7–125.1°E), north-east China, were examined in both 2006 and 2007. The correlations between fuel characteristics and soil parameters were analysed using principal component analysis (PCA) and partial least squares regression (PLS). The main emphasis was on the feasibility of using corn stovers as feedstock in direct combustion for heat and power generation. The examined corn stovers from Kerchin generally have similar characteristics to energy grasses grown in Europe and may be used as biofuels. However, large variations, up to several orders of magnitude, in the fuel characteristics existed among the samples. With PCA, the studied soils showed a clear distinction between soluble and less soluble elements, with a trend for higher insoluble element (such as Si) concentrations in south-western soils and a higher pH in the more northern soils. The component for fuel characteristics showed a distinct trend with latitude that can be explained by the above-mentioned soil component pattern. PLS regression models suggested some important relationships that may be used to predict corn stover fuel characteristics using soil and environment properties; for example, latitude, soil pH and Si are the most important predictors for Ca content in corn stovers, but not for K that is best predicted by soil K. Although limited by numbers of samples and sites, this study indicated that this approach can be used to predict biofuel quality.
Article
The current ethanol production processes using crops such as corn and sugar cane are well established. However, the utilization of cheaper biomasses such as lignocellulose could make bioethanol more competitive with fossil fuels, without the ethical concerns associated with the use of potential food resources. A cassava stem, a lignocellulosic biomass, was pretreated using dilute acid to produce bioethanol. The pretreatment conditions were evaluated using response surface methodology (RSM). As a result, the optimal conditions were 177 °C, 10 min and 0.14 M for the temperature, reaction time and acid concentration, respectively. The enzymatic digestibility of the pretreated cassava stem was examined at various enzyme loadings (10–40 FPU/g cellulose of cellulase and 30 CbU/g of β-glucosidase). With respect to economic feasibility, 20 FPU/g cellulose of cellulase and 30 CbU/g of β-glucosidase were selected for the test concentration and led to a saccharification yield of 70%. The fermentation of the hydrolyzed cassava stem using Saccharomyces cerevisiae resulted in an ethanol concentration of 7.55 g/L and a theoretical fermentation yield of 89.6%. This study made a significant contribution to the production of bioethanol from a cassava stem. Although the maximum ethanol concentration was low, an economically efficient overall process was carried out to convert a lignocellulosic biomass to bioethanol. Key wordsBioethanol–Response Surface Methodology (RSM)–Cassava Stem–Enzymatic Hydrolysis–Fermentation
Article
Ginger, cassava, maize, wheat, french bean and tomato were grown for periods up to six weeks in continuously flowing nutrient solutions at seven constant pH values ranging from 3.3 to 8.5. All species achieved maximum or near-maximum growth in the pH range 5.5 to 6.5. However, there were substantial differences in the ability of species to grow outside this range. Ginger and cassava were the most tolerant species to low solution pH, while ginger and tomato were the only species to show no yield depression at the highest solution pH. Roots of all species at pH 3.3 and some species at pH 4.0 exhibited symptoms of hydrogen ion injury. In addition, the concentrations of magnesium in the tops of all six species, of nitrogen in the tops of tomato and cassava, and of manganese in the tops of maize at these pH values were inadequate for optimal growth. Growth depression at high solution pH was associated with iron deficiency in maize and wheat and with nitrogen and/or copper deficiency in cassava. The relevance of the present results to crop growth under field conditions is discussed. The complex interplay of plant and soil characteristics militates against precise definition of an optimum pH range for the growth of a particular crop unless the soil is also specified.
Article
When cassava is harvested too early, it often leads to reduction in yield, while delayed harvest leads to development of woody and fibrous tuberous roots, and reduction in starch content. The optimum harvest time is not known. The objectives of this study were to determine the effect of genotype, location and season on starch extraction in order to find an optimum harvest regime for cassava, and to find the best parameter for monitoring starch levels in cassava tuberous roots. Results showed that genotypic effect was large for starch weight, starch extraction rate on fresh weight basis, and root dry matter content. This suggested that high starch weights could be realised by selection of suitable varieties for starch extraction. It was found that cassava harvesting and starch extractions should be done between October and November since the highest starch extraction rates were achieved during that period, and drying of the extracted starch using the open air method was fast and convenient. The results also suggested that starch levels can efficiently be monitored using starch extraction rate on fresh root weight basis. Starch content on fresh root basis and root dry matter content can also be used to determine the optimum time to harvest cassava for starch extraction but were inferior to starch extraction on fresh root weight basis.
Article
How to harvest and process corn stover to maximize its quality as a fuel or industrial feedstock and minimize material losses are compelling issues in the industrial utilization of corn stover. The objectives of this investigation were to evaluate the variation in the chemical composition and energy content of aboveground components of the corn plant over time and to evaluate how composition changes after grain physiological maturity is reached and the plants are weathered while undergoing further field drying. Above ground biomass distribution and composition of two almost identical corn cultivars (Pioneer 32K61 and 32K64 Bt) were studied from an estimated 2 weeks before corn kernel physiological maturity until 4 weeks after the grain had already reached a moisture content suitable for combine harvesting. Compositional analysis of corn stover fractions gathered over the course of maturation, senescence, and weathering using NIR spectroscopy showed (1) a rapid drop in soluble glucan, (2) increase in lignin, and (3) increase in xylan. By day 151 after planting, about when grain from surrounding non-test plots was harvested at about 15.5% moisture, composition of the different fractions remained fairly constant. Since product yield in fermentation-based biomass conversion processes is proportional to the structural carbohydrate content of the feedstock, timing of stover collection and the proportion of anatomical fractions collected affect the quality of corn stover as fermentation feedstock. Since the energy content of corn stover anatomical fractions is shown to remain fairly constant over time and from one plant to another (16.7–20.9 kJ g−1), insofar as combustion processes are concerned, it apparently makes little difference which part of the plant is used, or at what time the material is harvested.
Article
Each perennial woody plant is a highly integrated system of competing carbohydrate sinks (utilization sites). Internal competition for carbohydrates is shown by changes in rates of carbohydrate movement from sources to sinks and reversals in direction of carbohydrate transport as the relative sink strengths of various organs change. Most carbohydrates are produced in foliage leaves but some are synthesized in cotyledons, hypocotyls, buds, twigs, stems, flowers, fruits, and strobili. Although the bulk of the carbohydrate pool moves to sinks through the phloem, some carbohydrates are obtained by sinks from the xylem sap. Sugars are actively accumulated in the phloem and move passively to sinks along a concentration gradient. The dry weight of a mature woody plant represents only a small proportion of the photosynthate it produced. This discrepancy results not only from consumption of plant tissues by herbivores and shedding of plant parts, but also from depletion of carbohydrates by respiration, leaching, exudation, secretion, translocation to other plants through root grafts and mycorrhizae and losses to parasites. Large spatial and temporal variations occur in the use of reserve- and currently produced carbohydrates in metabolism and growth of shoots, stems, roots, and reproductive structures. A portion of the carbohydrate pool is diverted for production of chemicals involved in defense against fungi, herbivores, and competing plants. Woody plants accumulate carbohydrates during periods of excess production and deplete carbohydrates when the rate of utilization exceeds the rate of production. Stored carbohydrates play an important role in metabolism, growth, defense, cold hardiness, and postponement or prevention of plant mortality.
Article
Increasing energy use, climate change, and carbon dioxide (CO2) emissions from fossil fuels make switching to low-carbon fuels a high priority. Biofuels are a potential low-carbon energy source, but whether biofuels offer carbon savings depends on how they are produced. Converting rainforests, peatlands, savannas, or grasslands to produce food crop–based biofuels in Brazil, Southeast Asia, and the United States creates a “biofuel carbon debt” by releasing 17 to 420 times more CO2 than the annual greenhouse gas (GHG) reductions that these biofuels would provide by displacing fossil fuels. In contrast, biofuels made from waste biomass or from biomass grown on degraded and abandoned agricultural lands planted with perennials incur little or no carbon debt and can offer immediate and sustained GHG advantages.
Save and Grow: Cassava
  • R H Howeler
  • N Lutaladio
  • G Thomas
R.H. Howeler, N. Lutaladio, G. Thomas, Save and Grow: Cassava, 2013. http:// www.fao.org/ag/save-and-grow/cassava/ (accessed 09.08.13).
The Cassava Handbook e a Reference Manual Based on the Asian Regional Cassava Training Course, International Centre for Tropical Agriculture
  • R H Howeler
R.H. Howeler, The Cassava Handbook e a Reference Manual Based on the Asian Regional Cassava Training Course, International Centre for Tropical Agriculture, Cali, Colombia, 2012.
  • M Wei
M. Wei et al. / Renewable Energy 83 (2015) 970e978