Guang Hui Xie

Cassava stems: a new resource to increase food and fuel production

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.

Alkali-based pretreatments distinctively extract lignin and pectin for enhancing biomass saccharification by altering cellulose features in sugar-rich Jerusalem artichoke stem.

Jerusalem artichoke (JA) has been known as a potential nonfood feedstock for biofuels. Based on systems analysis of total 59 accessions, both soluble sugar and ash could positively affect biomass digestibility after dilute sodium hydroxide pretreatment (A). In this study, one representative accession (HEN-3) was used to illustrate its enzymatic digestibility with pretreatments of ultrasonic-assisted dilute sodium hydroxide (B), alkaline peroxide (C), and ultrasonic-assisted alkaline peroxide (D). Pretreatment D exhibited the highest hexose release rate (79.4%) and total sugar yield (10.4 g/L), which were 2.4 and 2.6 times higher, respectively, than those of the control. The analysis of cellulose crystalline index (CrI), cellulose degree of polymerization (DP), thermal behavior and SEM suggested that alkali-based pretreatments could distinctively extract lignin and pectin polymers, leading to significant alterations of cellulose CrI and DP for high biomass saccharification. Additionally, hydrogen peroxide (H2O2) could significant reduce the generation of fermentation inhibitors during alkali-based pretreatments.

Genetic Variation and Yield Performance of Jerusalem Artichoke Germplasm Collected in China

Abstract Jerusalem artichoke ( Helianthus tuberosus L.) is a perennial tuberous plant rich in inulin and is a potential energy crop. This study was conducted in a semiarid region of the Loess Plateau to investigate variations in morphological and agronomic characteristics and yield performance of 59 Jerusalem artichoke clones collected from 24 provinces in China. The germplasm we collected exhibited variations either in qualitative or in quantitative traits. Substantial genetic variations (genotype coefficient of variation >20%) in the main stem diameter, main stem number per plant, branch number per main stem, tuber number per plant, tuber size, tuber yield, and top yield (i.e., aboveground biomass) were found as well. Seven clones had a tuber yield ranging between 9.1–10.6 t ha −1 , 7 clones had a top yield ranging between 18.1–31.3 t ha −1 , and 15 clones had a total biomass yield (i.e., tuber and top weight) between 25.0–35.0 t ha −1 on an oven-dried weight basis under the drought soil and climatic condition in the semiarid region. The 59 Jerusalem artichoke clones were clustered into 8 groups based on 17 quantitative traits, and indicated that the most prevalent clones planted by farmers exhibited relatively low variation. Correlation analysis was conducted on the morphology and agronomy of the clones. This investigation suggests possible genetic improvement of Jerusalem artichoke for a higher tuber yield or a top biomass yield, and as a promising application for inulin or bioenergy in semiarid regions.

Nitrogen and Carbon Dynamics under the Canopy of Sand Dune Shrubs in a Desert Ecosystem

ABSTRACT Organic matter and nitrogen, crucial in terrestrial ecosystems, are limited in deserts due to the most obvious characteristics of scarcity of plant cover and low productivity. Little attention has been given to nutrient availability and ecological processes in desert sand dunes. We investigated the temporal and seasonal dynamics of carbon and nitrogen under two representative perennial shrubs of the Negev Desert inland sand dunes, Retama raetam and Artemisia monosperma. Having investigated total organic carbon, dissolved organic carbon, total soluble nitrogen, and mineralizable nitrogen in the soils at 0–10 cm depth, we conclude that in the Negev sandy soil ecosystem: (1) the concentration of carbon and nitrogen in the soil under the canopy of R. raetam was higher than in that under A. monosperma; (2) more available nitrogen appeared during the wet season compared to the other seasons, mainly due to regulation of soil water content; (3) the amounts of total organic carbon, total soluble nitrogen and mineralizable nitrogen were greatest in winter, and (4) nutrient heterogeneity is controlled mainly by plant cover rather than by the species forming the cover.

An economic analysis of sweet sorghum cultivation for ethanol production in North China

Sweet sorghum [Sorghum bicolor (L.) Moench] is a promising non‐food energy crop. The objective of this study was to determine the economic costs and input sensitivity of sweet sorghum compared to cotton, maize, and sunflower, at two saline‐alkali sites in Shandong (Wudi County) and Inner Mongolia (Wuyuan County) provinces of China. The data were collected quantitatively based on a face‐to‐face interview with 100 and 67 sweet sorghum growers at the two sites, respectively. The sweet sorghum grown at Wudi had lower external input (5469 CNY ha−1), higher net return (7305 CNY ha−1) and benefit‐cost ratio (2.36) than its reference crop, cotton (18 454 CNY ha−1; 3615 CNY ha−1; 1.24). At Wuyuan, the sweet sorghum showed contrasting economic performance (19 541 CNY ha−1; −3438 CNY ha−1; 0.91), which was largely because of the higher labor costs compared to sunflower (10 896 CNY ha−1; 15 133 CNY ha−1; 2.49); and maize (9108 CNY ha−1; 14 760 CNY ha−1; 2.76). The productivity of sweet sorghum per unit of external input costs (kg CNY−1) was 13.12 for Wudi and only 3.26 for Wuyuan. Based on the Cobb‐Douglas production function, the external inputs of diesel and seed had a significantly positive impact on the profitability of sweet sorghum at Wudi but not at Wuyuan. However, the costs of irrigation and film cover were significantly negative. The energy crop, sweet sorghum, showed a better return to scale on investment than cotton and sunflower.

Dynamics of the Nitrogen-Efficient Guild and Its Relationship to Nitrogen and Carbon Patterns in Two Desert Soil Ecosystems

Nitrogen fixation is generally considered to play a major role in nitrogen assimilation in desert soils, and the Nitrogen-Efficient Guild (NEG) is a useful index of the free-living nitrogen fixer population. Nitrogen-Efficient Guild dynamics in macrophytic patches in the Negev Desert probably contribute to the understanding of nitrogen processes in desert ecosystems. It is also important to determine the relationship between the Nitrogen-Efficient Guild numbers and nutrient availability on a tempospatial dynamic basis. This study was conducted in the Negev Desert during a period of one year. During this time, the Nitrogen-Efficient Guild number fluctuated between 3.9 - 0.7 2 10 6 and 28.5 - 5.3 2 10 6 colony forming units (CFU) g -1 in a loessial soil site, and 0.7 - 0.2 2 10 6 and 10.7 - 1.8 2 10 6 in a sandy soil site, with significant peak values (P < 0.05) during the winter season. The results demonstrate that significantly larger populations of free-living nitrogen fixers exist in soils under shrub canopies, suggesting considerable nitrogen fixation ability. It was also concluded that the nitrogen-fixing populations and communities vary with seasons in the desert, since they are mainly controlled by soil moisture. Furthermore, the Nitrogen-Efficient Guild numbers exhibit a significant correlation with total organic carbon and total soluble nitrogen, but not with dissolved organic carbon.

A quantitative assessment of crop residue feedstocks for biofuel in North and Northeast China

Crop residue resources may affect soil quality, global carbon balance, and stability of crop production, but also contribute to future energy security. This study was performed to evaluate the spatial and temporal variation in residue quantities of field crops in five provinces of North China (NC) and three provinces of Northeast China (NEC). The availability of biomass resources was derived from statistical data on crop yields for all crops on the provincial and even county level.

Multivariate modelling on biomass properties of cassava stems based on an experimental design

Based on a factorial experimental design (three locations × three cultivars × five harvest times × four replicates) conducted with the objective of investigating variations in fuel characteristics of cassava stem, a multivariate data matrix was formed which was composed of 180 samples and 10 biomass properties for each sample. The properties included as responses were two different calorific values and ash, N, S, Cl, P, K, Ca, and Mg content. Overall principal component analysis (PCA) revealed a strong clustering for the growing locations, but overlapping clusters for the cultivar types and almost no useful information about harvest times. PCA using a partitioned data set (60 × 10) for each location revealed a clustering of cultivars. This was confirmed by soft independent modelling of class analogy (SIMCA) and partial-least-squares discriminant analysis (PLS-DA), and indicated that the locations gave meaningful information about the differences in cultivar, whereas harvest time was not found to be a differentiating factor. Using the PLS technique, it was revealed that ash, K, and Cl content were the most important responses for PLS-DA models. Furthermore, using PLS regression of fuel and soil variables it was also revealed that fuel K and ash content were correlated with the soil P, Si, Ca, and K content, whereas fuel Cl content was correlated with soil pH and content of organic carbon, N, S, and Mg in the soil. Thus, the multivariate modelling used in this study reveals the possibility of performing rigorous analysis of a complex data set when an analysis of variance may not be successful.

Effects of salt stress on biomass and ash composition of switchgrass (Panicum virgatum)

This study was to evaluate the effects of salt stress on the biomass production and fuel characteristics of energy crop switchgrass in Northern China. A greenhouse-pot experiment was conducted to investigate the salt tolerance of the Blackwell, Cave-in-rock and Sunburst cultivars, using the dominant native grass Leymus chinensis as a reference. All three switchgrasses yielded a greater aboveground biomass per plant than Leymus under low-salt conditions (≤2 g NaCl kg−1). However, their biomass production declined significantly at higher salt concentrations. The most salt-tolerant cultivar with respect to biomass production was Cave-in-rock, followed by Blackwell and Sunburst. Among the biomass fuel characteristic studied, ash composition was more significantly affected by salt stress than calorific values. High salt concentrations in the soil increased the content of Ca, Cl and Na in the biomass ash but reduced that of K. The impact of salt stress on ash transformation during combustion was estimated by considering three molar ratios of mineral elements. Growth in high-salt soils reduced the slagging tendency of the fuel, as indicated by the K/(Ca + Mg) ratio. The added Na is unlikely to cause eutectic formation during switchgrass combustion because the Na/(K + Na) ratio was generally below 0.2. However, the addition of NaCl increased the risk of forming chlorine-rich deposits (probably from the fly ash), as indicated by the Cl/(K + Na) ratio.

Dynamics of Soil Nitrogen along a Topoclimatic Gradient in the Judean Desert

Nitrogen is considered to be one of the major deficient nutrient elements in desert soils, where levels of nitrogen and its fractions undergo rapid tempospatial and chemical changes with the changes in season, according to water availability. A better understanding of this knowledge would be useful for describing the nitrogen state and changes in arid to semiarid systems. The present study investigated mineral nitrogen content in soils sampled from four sites in the Judean Desert along a topoclimatic gradient ranging from Mediterranean to arid conditions, over a period of two years. It was concluded that, along the Judean Desert topoclimatic gradient, temporal dynamics in total soluble nitrogen (TSN) (0.4-80.0 mg kg -1 dry soil), mainly consisting of NH 4 + -N (0.03-28.1 mg kg -1 dry soil) and NO 3 - -N (0-57.2 mg kg -1 dry soil), are closely related to the soil moisture pattern. However, the effect of soil moisture on long-term TSN spatial dynamics is not so pronounced, due to leaching and denitrification. Significantly higher NH 4 + -N than NO 3 - -N levels exist in soils during dry periods, whereas an opposite pattern was observed during the wet seasons. Ammonia may be volatilized, preventing ammonium from accumulating with a decrease in soil clay content. More NO 2 - -N accumulated in a drier site than in moister sites, probably due to aridity having a different impact on different nitrification processes.