Evaluating starchy food effluents as potential green inhibitors of calcium carbonate scale in oil and gas production

The development of green scale inhibitors has been the subject of several recent studies aimed at reducing the negative environmental impacts of the oil and gas industry. This work evaluated the potential of saccharides, polysaccharides, and starchy food effluents (washing wastewaters from potato, sweet potato, cassava, and potato peels) as biodegradable substances to inhibit calcium carbonate scale formation. Calcium carbonate precipitation experiments were initially conducted to assess the influence of glucose, maltose, maltodextrin, and soluble starch on the induction time, particle size, and morphology of the precipitates. The presence of these molecules resulted in a delay in the induction time of crystallization, with the delay increasing as the polymer chain size increased. Scanning electron microscopy, X-ray diffraction, and Raman spectroscopy analysis revealed that the saccharides and polysaccharides promoted the formation of calcite with an irregular shape and smaller crystallite size. The polymer chain size also affected the scaling time determined in tube blocking tests conducted in two brine scenarios (more severe and less severe), demonstrating the inhibitory potential of these molecules. However, only soluble starch proved to be effective in inhibiting scale formation in the less severe brine scenario. Based on these preliminary results, starchy food effluents were selected to evaluate their potential for inhibiting scale formation. The effluents from sweet potato and potato peels showed better performance compared to the potato effluent. The sweet potato effluent efficiently inhibited scale formation in the less severe brine scenario, possibly due to the presence of phenolic compounds and other substances, in addition to soluble starch, that also have inhibitory effects. In contrast, the cassava effluent was incompatible with the brines, leading to immediate scale formation in both scenarios.