Disposal of heavy doses of coal/bagasse ash in sugar cane fields in Mauritius
| MSI08P4315 | |
| Soobadar, A Ng Kee Kwong, K F | |
| Disposal of heavy doses of coal/bagasse ash in sugar cane fields in Mauritius | |
| University of Mauritius Research Week 2008: Sustainable Development and Innovation, The University of Mauritius, Réduit, Mauritius, 1-5 September 2008 | |
| Conference paper | |
| 2008 | |
| En | |
| En | |
| In response to the reform of European Union Sugar Regime imposing a 39 per cent decrease in the price of sugar, the sugar industry in Mauritius is moving towards one of renewable biomass where the use of bagasse and coal to produce electricity will result in the generation of around 20,000 T of coal ash in the intercrop season and an equivalent amount of bagasse ash in the crop season. Large scale application on agricultural lands of bagasse and coal ash has been touted as the most economically and environmentally sound way of disposal. Studies in the temperate regions have shown that the application of ash to crops can improve chemical and physical soil properties and also provide essential nutrients such as boron, calcium, potassium and sulphur to the growing plant especially in soils of poor fertility. However the applications of ash can also raise heavy metals concentrations in soils. Moreover, the loading of ash to soils is dictated by its salt content whose solubility may cause salinity problems in soils, resulting in increases of electrical conductivity which may retard plant establishment and growth but also affect the soil and groundwater quality. For sustainable soil management and water quality purpose, the long term fate of coal or bagasse ash needs to be carefully monitored. Indeed the loading of soils with heavy metals to amounts well above natural concentrations without any prospects of their removal is not an ecologically sound practice. For these above reasons field trials have been conducted to accurately assess the impact of the disposal of high doses of coal and bagasse ash on cane production and on the heavy metal content in soil and water. Four sites (Belle Rive, Pamplemousses, Union Park, and Médine) with three treatments (chemical fertilizer at recommended rate, 50T/ha coal ash and 100T/ha coal ash) replicated four times in a randomized complete block design have been laid down. Concurrently lysimeter studies have been set up at Belle Rive (annual rainfall >3500mm) and at Réduit (annual rainfall <1500mm) to determine whether the application of ash could result in the contamination of groundwater by heavy metals. Coal ash was applied to the lysimeters at both sites at three rates namely, 0, 50 and 100 T/ha in two replicates. The concentrations of heavy metals in soil, plant and lysimeter leachates following digestion with aqua regia were measured using a Perkin Elmer 700 Atomic Absorption Spectrophotometer fitted with a Graphite Tube Atomizer and Flow Injection. Field data have shown that high rates application of coal ash (50 and 100 T/ha) at planting may have an adverse effect on cane and sugar yields. In general, because the concentrations of heavy metals in coal ash used in this study were well below the ceiling limits established by the United States Environment Protection Agency (USEPA), soil samples taken at 1, 12 and 24 months from plots which have received 50T and 100T/ha coal ash, have shown that the concentrations of copper (Cu), zinc (Zn), nickel (Ni), manganese (Mn), lead (Pb) and mercury (Hg) were not significantly different from the plots where only chemical fertilizers were applied. Furthermore samples taken at yearly intervals from different parts of the cane plant (cane, top, trash) which have been grown on plots receiving coal ash did not show any significant difference in heavy metal content from those of the control (chemical fertilizers only) plots. Data obtained during the lysimeter study demonstrated that leaching of heavy metals down the soil profile will not impair the quality of the groundwater. In conclusion, there is little risk of groundwater contamination by heavy metals from ash and the uptake of heavy metals in plant is negligible and will not constitute a hazard to the quality of the sugar produced. However high doses of ash are nevertheless not recommended on account of negative effects on sugar cane production. | |
| 2008-11-28 | |
| En | |
| CHEM |