César Sáez-Navarrete

An exploratory study of peat and sawdust as enhancers in the (bio)degradation of n-dodecane

Current practice for dealing with oil spills involves the use of adsorbent materials to contain the pollution prior to bioremediation of the contaminated soil and adsorbent. This work presents a study of the effects of bioavailable carbon sources in the adsorbents peat and sawdust as organic nutrients for microorganisms specialized in degrading n-dodecane in soil and sawdust contaminated with hydrocarbon mixtures. An experimental bioremediation system was developed using n-dodecane, biomass adapted to n-dodecane, inorganic nutrients and the two adsorbents (sterilized). Bioreactors containing peat enhanced cell growth the most and also evolved more CO2. An advantage of peat is that its soluble carbon sources can sustain higher cell densities compared to sawdust, and this may prove decisive when cultivating endogenous microorganisms for the aerobic bioremediation of soils contaminated with hydrocarbons. However, at the end of the 68-day experiment slightly higher n-dodecane removal was identified in the system containing sawdust-n-dodecane (99.6%) than in that with peat-n-dodecane (98.5%), evidencing the higher hydrocarbon retention capacity of peat. Based on this study, the use of sawdust instead of peat is recommended when an adapted inoculum is available for aerobic bioremediation of organic contaminants, whereas the use of peat is advisable to boost cell densities in order to improve the probability of sustaining a viable biomass in unfavorable conditions.

CO2 adsorption on agricultural biomass combustion ashes

Carbon capture and storage has become an alternative means of confronting global warming. Further research and development into adequate and low-cost materials is required for CO2 adsorption technologies.Samples of fly ash, bottom ash and their respective pellets, produced from wheat bran combustion, were characterized and tested to assess their capacity for CO2 adsorption at different temperatures. Neither the ashes nor their pellets were subject to prior thermochemical activation.The bottom ash sample and its pellets showed a higher adsorption capacity for the majority of the temperatures studied. The pelletized bottom ash reached the maximum adsorption capacity (0,07 mmol CO2/g), followed by the non-pelletized bottom ash (0,06 mmol CO2/g); both at an adsorption temperature of 25°C.CO2 adsorption of bottom ash, from the combustion of wheat bran (agricultural biomass), by a physical adsorption mechanism was demonstrated whereas with the fly ash sample, CO2 adsorption by both physical and chemical adsorption mechanisms was identified.