Aplicação de glicerina bruta residual da produção de biodiesel em agroecossistemas

Abstract

On the search for energetic sources that might reduce the environmental impacts caused by the use of fossil fuels, biodiesel has became an economically viable and totally renewable alternative. However, there are some problems that must be solved for biodiesel be considered completely renewable. Among these problems, special attention must be given for creating possibilities to use the byproducts generated. Hence, this work was developed with the objective of evaluating the alternative of disposal residual crude glycerin of biodiesel production on agroecosystem, aiming to observe the effects of different residue concentrations on chemical and biological soil characteristics, on plant development, without promoting environmental contamination. For that, an experiment was carried out in randomized blocks design, with seven replicates. Treatments were organized according to factorial scheme 4 x 3, where four were the glycerin (residue) concentrations (L ha-1): 0; 48.7; 146.1 and 292.2; and three were the incubation periods, considering 0, 30 and 60 days. Lettuce was used as the bioindicator species. For analyzing microbial activity, an experiment was developed in laboratory, with completely randomized design and five treatments. Soil samples of 100 g were incubated during 36 days with the same concentrations of crude glycerin, besides soil and glycerin absence. During this period, 11 evaluations were performed to measure CO2 released, in each sample. For evaluating the effects of crude glycerin on plant germination, other experiment was carried out in laboratory, using heary beggaticks achenes. Experimental scheme was randomized blocks, with five replicates and the same previous glycerin rates, but with different origins of the residue (laboratory and biodiesel mill). Residue disposal promoted the enhancement of soil organic matter, organic carbon, pH, cationic exchange capacity, phosphorous and potassium. However, residue application reduced the percentage of base saturation (V%); although, it increased the sodium content. Residue disposal was negative to lettuce in all concentrations. For rates up to 143.83 L ha-1, crude glycerin stimulated soil microbial activity, being a positive indication for further studies related to agricultural soils. On the other side, glycerin applications reduced hairy beggarticks root protrusion, even in the smallest rates. Crude glycerin has sodium levels that limits its application on the soil.