Biochar obtained from eucalyptus, rice hull, and native bamboo as an alternative to decrease mobility of hexazinone, metribuzin, and quinclorac in a tropical soil.

Mobile herbicides have a high potential for groundwater contamination. An alternative to decrease the mobility of herbicides is to apply materials with high sorbent capacity to the soil, such as biochars. The objective of this research was to evaluate the effect of eucalyptus, rice hull, and native bamboo biochar amendments on sorption and desorption of hexazinone, metribuzin, and quinclorac in a tropical soil. The sorption-desorption was evaluated using the batch equilibrium method at five concentrations of hexazinone, metribuzin, and quinclorac. Soil was amended with eucalyptus, rice hull, and native bamboo biochar at a rate of 0 (control-unamended) and 1% (w w-1), corresponding to 0 and 12 t ha-1, respectively. The amount of sorbed herbicides in the unamended soil followed the decreasing order: quinclorac (65.9%) > metribuzin (21.4%) > hexazinone (16.0%). Native bamboo biochar provided the highest sorption compared to rice hull and eucalyptus biochar-amended soils for the three herbicides. The amount of desorbed herbicides in the unamended soil followed the decreasing order: metribuzin (18.35%) > hexazinone (15.9%) > quinclorac (15.1%). Addition of native bamboo biochar provided the lowest desorption among the biochar amendments for the three herbicides. In conclusion, the biochars differently affect the sorption and desorption of hexazinone, metribuzin, and quinclorac mobile herbicides in a tropical soil. The addition of eucalyptus, rice hull, and native bamboo biochars is a good alternative to increase the sorption of hexazinone, metribuzin, and quinclorac, thus, reducing mobility and availability of these herbicides to nontarget organisms in soil.

Low vacuum thermochemical conversion of anaerobically digested swine solids.

This work provides data on the production of biochar from the pyrolysis of the solid phase of swine effluents following anaerobic biodigestion. The study involved the low vacuum thermochemical conversion by environmental scanning electron microscope (ESEM) in a thermoregulated hot-stage tungsten SEM. The feedstock was characterized by FTIR, ESEM and energy dispersive X-ray analysis (EDS). The charred feedstock at peak temperatures of 300°C, 400°C, 500°C, 600°C, 700°C, and 1000°C were assessed by SEM and EDS. For each pyrolysis experiment, the exhaust gases were monitored by photoacoustic spectroscopy. SEM/EDS indicated that for increasing peak temperature in low vacuum pyrolysis, the mass losses are greater and the proportion of mineral particles such as P, Ca and Mg in the biochar. Photoacoustic spectroscopy showed that low vacuum pyrolysis is responsible for emissions of toxic gases NH3 and SO2 and radiative trace gases, especially N2O above 600°C.