Sustainable Energy Crop Production: A Case Study for Sugarcane and Cassava Production in Yunnan, China

The possibility of using biomass as a source of energy in reducing the greenhouse-effect imposed by carbon dioxide emission and relieving energy crisis is a matter of great interest, such as bioethanol production. Nevertheless, the cultivation of dedicated energy crops dose meet with some criticisms (conflict with food security and environmental degradation, for example). Nowadays sugarcane and cassava are regarded as the potential energy crops for bioethanol production. Endowed with natural resources and favorable weather condition, Yunnan province, China, is the major sugarcane and cassava production area in China. This paper presents production structures of these two crops in Yunnan and compares the sustainable production between the usages of sugarcane and cassava as bioethanol feedstock. Firstly, we estimated the technical efficiency for sugarcane and cassava production by adopting the production function and stochastic frontier production function. Field surveys from 61 sugarcane farmers and 50 cassava farmers were collected in June and September, 2008. Secondly, the sustainability of each crop production was evaluated. Since there is no generally accepted definition of sustainable production, a set of criteria was defined including 2 concerns (employment and food supply) from socio-economic area and 3 concerns (conversion rate to ethanol, water requirement, and fertilizer pollution) from environmental area. Empirical results demonstrated that the average production function was located below the frontier production function, 5% for sugarcane production and 7% for cassava production. These findings reflect the existence of technical inefficiency not only in the sugarcane production but also in the cassava production as well. But after considering sustainable production, cassava, which requires low agro-chemical, should be recommended as a prior energy crop in Yunnan with higher rates in ethanol conversion and dry matter.International Development, Production Economics, Energy crop, stochastic frontier production, Sustainable production, Yunnan province, Bioethanol,

Edge chirality determination of graphene by Raman spectroscopy

Raman imaging on the edges of single layer micromechanical cleavage graphene (MCG) was carried out. The intensity of disorder-induced Raman feature (D band at ~1350 cm-1) was found to be correlated to the edge chirality: it is stronger at the armchair edge and weaker at the zigzag edge. This shows that Raman spectroscopy is a reliable and practical method to identify the chirality of graphene edge and to help in determination of the crystal orientation. The determination of graphene chirality is critically important for fundamental study as well as for applications.Comment: 14 pages, 3 figures, 1 tabl

Self-Assembled Chiral Photonic Crystals From Colloidal Helices Racemate

Chiral crystals consisting of micro-helices have many optical properties while presently available fabrication processes limit their large-scale applications in photonic devices. Here, by using a simplified simulation method, we investigate a bottom-up self-assembly route to build up helical crystals from the smectic monolayer of colloidal helices racemate. With increasing the density, the system undergoes an entropy-driven co-crystallization by forming crystals of various symmetries with different helical shapes. In particular, we identify two crystals of helices arranged in the binary honeycomb and square lattices, which are essentially composed by two sets of opposite-handed chiral crystal. Photonic calculations show that these chiral structures can have large complete photonic bandgaps. In addition, in the self-assembled chiral square crystal, we also find dual polarization bandgaps that selectively forbid the propagation of circularly polarized lights of a specific handedness along the helical axis direction. The self-assembly process in our proposed system is robust, suggesting possibilities of using chiral colloids to assemble photonic metamaterials.Comment: Accepted in ACS Nan