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In recent years, various thermochemical processes have been studied to obtain bioenergy. Hydrothermal carbonization (HTC) has proven to be a convenient alternative since it allows biomass with high moisture and ash content to be processed without prior drying processes, obtaining a biofuel with up to 20 to 30 % more calorific value compared to biomass. However, the main challenge is determining optimum points of increase in calorific power and energy performance to transform it into economically feasible. This study proposes the study and optimization of the HTC process with two Chilean biomasses: sawdust (Pinus radiata) and rapeseed (Brassica napus). Mass yield (MY), higher heating value (HHV), and energy yield (EY) were analyzed by applying a Design of Experiments (DoE) with three factors and two levels (23). The variables used and their levels were temperature (T): 190 - 250 °C; time (t): 60-120 min; and biomass/water ratio (B/W): 8 - 14 % for rapeseed and 10 - 16 % for sawdust. For sawdust, increasing the temperature from 190 to 250 °C raised HHV by 23 % and lowered MY (by 21 %) and EY (by 18 %). Rapeseed HHV showed an increase of 23 %, while MY and EY decreased by 11 and 14 %. In the statistical analysis, the most influential variables for both biomasses were temperature and the B/W ratio, similar to what was found in previous studies. New operating points were determined to maximize the HHV of the hydrochar using the Response Surface Methodology and the equations obtained from the DoE (R2 above 0.98). The results achieved were higher than the average indicated in the literature. For sawdust, an EY of 77 % and an HHV of 28.6 MJ/kg (+48 %) were obtained at 280 °C, 100 min, and a B/W of 13 %. On the other hand, for rapeseed, EY=49.2 % and HHV=29.1 MJ/kg (+37 %) were achieved at 280 °C, 90 min, and a B/W ratio of 10 %. [ABSTRACT FROM AUTHOR]

It is known that residential wood combustion (RWC) is an important source of fine particle emissions. The purpose of this work was to characterize the chemical composition of the particulate matter present in the Temuco urban atmosphere during winter, specifically the polycyclic aromatic hydrocarbon (PAH) profile, because PAHs are considered to be among the key compounds in particulate matter toxicity. During the 2008 winter monitoring campaign, samples of particulate matter with aerodynamic diameters of ≤10 (PM10) and ≤2.5 (PM2.5) μm were taken on days with contamination episodes. Sixteen U.S. Environmental Protection Agency (EPA) PAH compounds were extracted with toluene and determined by gas chromatography–mass spectrometry (GC-MS). The results show that phenantrene was the predominant compound associated with particulate matter, at a concentration range between 300 and 600 ng m−3, 18 times higher than the second most abundant PAH compound. High-molecular-mass compounds such as dibenz[a,h]anthracene, benzo[g,h,i]perylene, and indeno[1,2,3,c,d]pyrene were also found, but they were minorities in the set. It was recognized from the PAH concentration ratios of the Temuco atmospheric aerosol that the main contamination source was in fact residential wood combustion; although not all the concentration ratios evaluated match the reported reference values, probably due to the kind of biomass used, the characteristics of Chilean heating appliances and climate. [ABSTRACT FROM AUTHOR]

A simple and sensitive method for the detection and enumeration of microbial s-triazine-degrading microorganisms in soil was designed. The procedure is based on the ability of some microbes to use s-triazines, such as simazine, atrazine, and cyanuric acid, as sole nitrogen source. It employs the respiration indicator 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) to detect metabolic activity and the most-probable-number (MPN) enumeration in microtiter plates. The method was used to identify simazine- and cyanuric acid-degrading activities in agricultural soils treated with the herbicide simazine. The MPN-TTC method showed that the number of simazine- and cyanuric acid-degrading microorganisms increased four weeks after the herbicide simazine had been applied.