Effect of secondary phase formation on the carbonation of olivine

Large-scale olivine carbonation has been proposed as a potential method for sequestering CO2 emissions. For in situ carbonation techniques, understanding the relationship between the formation of carbonate and other phases is important to predict the impact of possible passivating layers on the reaction. Therefore, we have conducted reactions of olivine with carbonated saline solutions in unstirred batch reactors. Altering the reaction conditions changed the Mg-carbonate morphology. We propose that this corresponded to changes in the ability of the system to precipitate hydromagnesite or magnesite. During high-temperature reactions (200 °C), an amorphous silicaenriched phase was precipitated that was transformed to lizardite as the reaction progressed. Hematite was also precipitated in the initial stages of these reactions but dissolved as the reaction proceeded. Comparison of the experimental observations with reaction models indicates that the reactions are governed by the interfacial fluid composition. The presence of a new Mgsilicate phase and the formation of secondary products at the olivine surface are likely to limit the extent of olivine to carbonate conversion. © 2010 American Chemical Society

Issues of Rice Policy in the Lower Mekong Basin

The commercialisation of rice farming in the Lower Mekong Basin has been at the centre of that region’s remarkable journey out of poverty and food insecurity since the 1970s. A development strategy that centred on opening rice farming to productivity-enhancing investments had the double effect of increasing the incomes of large numbers of poor rural households while generating a marketable surplus to supply the rapidly growing urban population at low prices. The growth in export demand further added to the incomes of rice farmers in the more productive parts of the Basin. Thus, a development pathway emerged that was driven by political necessity to be broadly based and inclusive. However, the very success of this pathway has created new policy issues, requiring adjustments in the long-term emphasis on the intensification of smallholder rice production. The growth in production has led to a decline in prices while costs have been increasing. This has led to pressure from rice farmers for price support. Related policy issues include the persistence of smallholdings, the growing preference for more diversified farming systems, the role of the processing and exporting sectors, and the changing physical environment in the Basin. This chapter examines policies influencing access to resources (specifically, to land, water, and technology), the management of farm activities (whether specialised in production of high-quality rice or diversified into production of non-rice crops), and the appropriation of value (as determined by interventions in the marketing and pricing of paddy and rice)