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A novel, multistage, dielectric, packed-bed, plasma reactor has been developed and is used to efficiently destroy environmental pollutants, such as volatile organic compounds (VOCs). A three cell plasma reactor, operated at ambient pressure and low temperatures, is found to be an effective technology for complete VOC remediation in air. The combination of plasma cells in series can significantly improve the efficiency of VOC decomposition, but the combined destruction rate is not simply an additive effect, there is a synergistic enhancement related to the effect on the plasma chemistry of sequential processing in the three cells. At the same time, the formation of byproduct such as NOx is strongly suppressed, and it is possible to remediate toluene and ethylene in air, with no detectable formation of NOx or nitric acid.

This article examines the experience of seven countries in East and Southern Africa with contract farming and outgrower schemes. In such schemes, farmers sell their crops under contract to private or public enterprises for processing or export in return for various price guarantees, inputs and services. The article identifies some of the key determinants of success or failure, evaluates performance and examines the constraints to replication. In most cases, performance in delivering services and providing income increases to farmers has been quite good, although high management costs limit the extent to which this form of organisation could be more widely applied. Looser control, relying more on price incentives and farmer participation, might lower overhead costs while developing management capability among growers.

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