Insights into hydrothermal treatment of biomass blends: Assessing energy yield and ash content for biofuel enhancement.

This study explores the Hydrothermal Carbonization (HTC) treatment of lignocellulosic biomass blends, delving into the influence of several key parameters: temperature, additive nature and dosage, residence time, and biomass composition. Rapeseeds, Pinus radiata sawdust, oat husks, and pressed olive served as the studied biomasses. One hundred twenty-eight experiments were conducted to assess the effects on mass yield (MY), energy yield (EY), higher heating value (HHV), and final ash content (ASH) by a Factorial Experimental Design. The derived model equations demonstrated a robust fit to the experimental data, averaging an R2 exceeding 0.94, affirming their predictive accuracy. The observed energy yield ranged between 65% and 80%, notably with sawdust and olive blends securing EY levels surpassing 70%, while rapeseed blends exhibited the highest HHV at 25 MJ/kg. Temperature emerged as the most influential factor, resulting in an 11% decrease in MY and a substantial 2.20 MJ/kg increase in HHV. Contrastingly, blend composition and additive presence significantly impacted ASH and EY, with all blends exhibiting increased ASH in the presence of additives. Higher initial hemicellulose and aqueous extractive content in raw biomass correlated proportionally with heightened HHV.

Hybrid porous media gasification of urban solid waste pre-treated by hydrothermal carbonization.

Global population growth and rising consumption levels have significantly increased resource use and energy demand, leading to higher greenhouse gas concentrations and increased waste output. As a result, alternative waste treatment methods for sustainable municipal solid waste (MSW) management are crucial. This research evaluates the efficiency of integrating hydrothermal carbonization (HTC) and gasification for an optimized MSW biomass blend. HTC was conducted for one hour at 220°C in a 5 L reactor, followed by gasification in a hybrid porous medium gasifier. The study investigated the effects of different filtration speeds on combustion temperature and hydrogen concentrations. The results showed that a filtration speed of 35 cm/s resulted in a maximum combustion temperature of 1035.7°C. The temperature remained consistent across filter speeds, while higher velocities yielded higher hydrogen concentrations. Additionally, increasing the filtration velocity raised temperatures in the hybrid bed while increasing the volumetric fraction of biomass decreased maximum temperatures. This research contributes to the understanding of merging HTC and gasification for MSW biomass blend treatment, aiming to reduce environmental impacts and costs while promoting renewable resources for long-term energy production.

An environmental assessment for municipal organic waste and sludge treated by hydrothermal carbonization.

Climate change is the world's greatest challenge today, the reason why it is urgent to optimize industrial processes and find new renewable energy sources. Hydrothermal carbonization (HTC) is one of the Waste-to-Energy technologies with greater projections due to its operative advantages. However, for its large-scale implementation, there are challenges related to the variability of the composition of the waste biomass and the seasonal and geographical availability. This research applied the Life Cycle Analysis methodology to evaluate the environmental impacts caused by three biomasses blends as raw material in the HTC process at laboratory scale. The blends analyzed considered different organic fractions of municipal solid waste (food and pruning) and sewage sludge. The results showed that blend 1 had a lower environmental impact for the case of production in the experimental laboratory level, compared with blends 2 and 3. This is mainly due to its greater calorific value and mass yield, which allows obtaining more hydrochar compared with the other blends, increasing the energy efficiency of the process. Also, between 87.94% and 98.00% of the energy reduction is required to obtain neutral impacts regarding the energy requirements in the experimental laboratory level scenario and the Chilean energy matrix. The processing of blends in HTC has excellent potential in a context where municipal solid wastes have been disposed in sanitary landfills or dumps, as in most emerging countries. Since this study incorporated data from the literature, future studies should perform an elemental analysis to provide experimental and differentiated data.

Valorization of oat husk by hydrothermal carbonization: Optimization of process parameters and anaerobic digestion of spent liquors.

The hydrothermal carbonization (HTC) optimization of oat husk was performed using a response surface methodology. Furthermore, anaerobic digestion (AD) of spent liquor and hydrochar addition were evaluated in the biomethane potential (BMP) test. Results found that temperature influences the most in the studied responses (i.e., mass yield (MY) and higher heating value (HHV)). Optimal hydrochar MY (53.8%) and HHV (21.5 MJ/kg) were obtained for 219.2 °C, 30 min, and 0.08 of biomass/water ratio. A successful prediction capability of the optimization approach was observed, archiving an error < 1% between predicted and validated responses. The BMP experiment showed the feasibility of spent liquor as a potential substrate to be treated by AD (144 NmLCH4/gCOD). Hydrochar boosted the methane production of spent liquor increasing up to 17% compared to digestion with no hydrochar addition. These findings provide new insights regarding oat husk valorization by integrating HTC and AD for energy production.

The black carbon dispersion in the Southern Hemisphere and its transport and fate to Antarctica, an Anthropocene evidence for climate change policies.

Black carbon (BC) has been measured in Antarctica's air, and its global warming effect can potentially speed up the ice melting in the most solid water reservoir of the planet. However, the primary responsible sources are not well evidenced in this region. The dispersion of black carbon emissions from the Southern Hemisphere was conducting using atmospheric chemical transport model and we compared the results with satellite registries from March 1st to April 30th in 2014. The emission inventory considered the anthropogenic and biomass burning emissions from global datasets. The largest and most populated cities in Southern Hemisphere showed the higher emission of BC. As a result, the average daily concentrations of atmospheric BC were around 4 ng/m3 in most regions of Antarctica according to its pristine characteristics. We analyzed fifteen relevant sites in coastal zones of Antartica and some peaks registered by the satellite records were not replicated by model outputs and it was mainly associated with the lack of emissions. Finally, we made simulations in the same period without biomass burning emissions and we observed decreased concentrations of BC in the range of 20-50%. As a result, we show that the black carbon transportation from the continental land to the polar region took place in 17-24 days during the Austral summer and the biomass burning emissions were the primary source. Black Carbon deposition in Antarctica is not permanent, but the uncontrolled emissions from Southern Hemisphere can increase its transportation to the white continent and make its accumulation during the period when the weak polar vortex occurs.

Black and organic carbon fractions in fine particulate matter by sectors in the South Hemisphere emissions for decision-making on climate change and health effects.

Some databases report global emissions of certain pollutants. Emissions Database for Global Atmospheric Research (EDGAR) project is one of these, which also records emissions by sources. In this study, the emissions of black and organic carbon and fine particulate matter from the EDGAR database were used as an input to process it in the Sparse Matrix Operator Kernel Emissions (SMOKE) model. We showed the spatial distribution of the fraction of black and organic carbon in particulate matter from each source in the Southern Hemisphere. Also, we extracted these ratios for several cities in the domain of analysis. The results and methodology of this study could improve the emission inventories with bottom-up methodology in areas without information located at Southern Hemisphere. Also, it could be relevant to obtain better performance in air quality modeling at the local level for decision-making on climate change and health effects.

Biodegradation of benzo[α]pyrene, toluene, and formaldehyde from the gas phase by a consortium of Rhodococcus erythropolis and Fusarium solani.

Polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs) are important indoor contaminants. Their hydrophobic nature hinders the possibility of biological abatement using biofiltration. Our aim was to establish whether the use of a consortium of Fusarium solani and Rhodococcus erythropolis shows an improved performance (in terms of mineralization rate and extent) towards the degradation of formaldehyde, as a slightly polar VOC; toluene, as hydrophobic VOC; and benzo[α]pyrene (BaP) as PAH at low concentrations compared to a single-species biofilm in serum bottles with vermiculite as solid support to mimic a biofilter and to relate the possible improvements with the surface hydrophobicity and partition coefficient of the biomass at three different temperatures. Results showed that the hydrophobicity of the surface of the biofilms was affected by the hydrophobicity of the carbon source in F. solani but it did not change in R. erythropolis. Similarly, the partition coefficients of toluene and BaP in F. solani biomass (both as pure culture and consortium) show a reduction of up to 38 times compared to its value in water, whereas this reduction was only 1.5 times in presence of R. erythropolis. Despite that increments in the accumulated CO2 and its production rate were found when F. solani or the consortium was used, the mineralization extent of toluene was below 25%. Regarding BaP degradation, the higher CO2 production rates and percent yields were obtained when a consortium of F. solani and R. erythropolis was used, despite a pure culture of R. erythropolis exhibits poor mineralization of BaP.

Emission factors for PM2.5, CO, CO2, NOx, SO2 and particle size distributions from the combustion of wood species using a new controlled combustion chamber 3CE.

The objective of this research was to determine emission factors (EF) for particulate matter (PM2.5), combustion gases and particle size distribution generated by the combustion of Eucalyptus globulus (EG), Nothofagus obliqua (NO), both hardwoods, and Pinus radiata (PR), softwood, using a controlled combustion chamber (3CE). Additionally, the contribution of the different emissions stages associated with the combustion of these wood samples was also determined. Combustion experiments were performed using shaving size dried wood (0% humidity). The emission samples were collected with a tedlar bag and sampling cartridges containing quartz fiber filters. High reproducibility was achieved between experiment repetitions (CV<10%, n=3). The EF for PM2.5 was 1.06gkg-1 for EG, 1.33gkg-1 for NO, and 0.84gkg-1 for PR. Using a laser aerosol spectrometer (0.25-34µm), the contribution of particle emissions (PM2.5) in each stage of emission process (SEP) was sampled in real time. Particle size of 0.265µm were predominant during all stages, and the percentages emitted were PR (33%), EG (29%), and NO (21%). The distributions of EF for PM2.5 in pre-ignition, flame and smoldering stage varied from predominance of the flame stage for PR (77%) to predominance of the smoldering stage for NO (60%). These results prove that flame phase is not the only stage contributing to emissions and on the contrary, pre-ignition and in especial post-combustion smoldering have also very significant contributions. This demonstrates that particle concentrations measured only in stationary state during flame stage may cause underestimation of emissions.

Elucidating the key role of the fungal mycelium on the biodegradation of n-pentane as a model hydrophobic VOC.

The role of the aerial mycelium of the fungus Fusarium solani in the biodegradation of n-pentane was evaluated in a continuous fungal bioreactor (FB) to determine the contribution of the aerial (hyphae) and non-aerial (monolayer) fungal biomass. The experimental results showed that although the aerial biomass fraction represented only 25.9(±3)% on a dry weight basis, it was responsible for 71.6(±4)% of n-pentane removal. The FB attained a maximum elimination capacity (ECmax) of 680(±30) g m(-3) h(-1) in the presence of fungal hyphae (which supported an interfacial area of 5.5(±1.5) × 10(6) m(2) m(-3)). In addition, a mathematical model capable of describing n-pentane biodegradation by the filamentous fungus was also developed and validated against the experimental data. This model successfully predicted the influence of the aerial biomass fraction and its partition coefficient on the n-pentane removal, with EC decreasing from 680(±30) g m(-3) h(-1) to values of 200(±14) g m(-3) h(-1) when the dimensionless partition coefficient increased from 0.21(±0.09) with aerial biomass to 0.88(±0.06) without aerial biomass.

Sensitivity analysis of biodiesel blends on Benzo[a]pyrene and main emissions using MOVES: A case study in Temuco, Chile.

Temuco is one of the most highly wood-smoke polluted cities in Chile; however, the diesel mobile sources are growing very fast in the past 10 years and so far very few studies have been done. The main goal of this research was to develop a 2013 emission inventory of criteria pollutants and Benzo[a]pyrene (BaP) and to evaluate the use of six biodiesel blends of 0%, 1%, 4%, 8%, 12%, and 20% by volume of fuel in diesel motors from the vehicle fleet within the mentioned areas using the Motor Vehicle Emission Simulator (MOVES). Input parameters for the base year 2005 were estimated to implement and adapt the model in Chile, while results of NOx, PM10, PM2.5, NH3, CO2 equivalent and SO2 were compared with the Chilean Emission Inventory estimated by the model "Methodology for the Calculation of Vehicle Emissions." The 2013 emissions reduced with respect to 2005, in the majority of the contaminants analyzed, despite the 47% increase in the annual miles traveled. Using biodiesel blends, an emission reduction was estimated at up to 15% in particulate matter, BaP, and CO for the year 2013, as well as an increment of 2% in NOx emissions, attributed to low sulfur content (50 ppm) in the diesel and the antiquity of the vehicle fleet. The results obtained gave evidence of the influence of the biodiesel use in the pollutant emissions to improve the Chilean air quality, as well as providing a strategy for this air quality management.

Assessing Polycyclic Aromatic Hydrocarbons (PAHs) using passive air sampling in the atmosphere of one of the most wood-smoke-polluted cities in Chile: The case study of Temuco.

This study addresses human health concerns in the city of Temuco that are attributed to wood smoke and related pollutants associated with wood burning activities that are prevalent in Temuco. Polycyclic Aromatic Hydrocarbons (PAHs) were measured in air across urban and rural sites over three seasons in Temuco using polyurethane foam (PUF) disk passive air samplers (PUF-PAS). Concentrations of ΣPAHs (15 congeners) in air ranged from BDL to ∼70 ng m(-3) and were highest during the winter season, which is attributed to emissions from residential heating by wood combustion. The results for all three seasons showed that the PAH plume was widespread across all sites including rural sites on the outskirts of Temuco. Some interesting variations were observed between seasons in the composition of PAHs, which were attributed to differences in seasonal point sources. A comparison of the PAH composition in the passive samples with active samples (gas+particle phase) from the same site revealed similar congener profiles. Overall, the study demonstrated that the PUF disk passive air sampler provides a simple approach for measuring PAHs in air and for tracking effectiveness of pollution control measures in urban areas in order to improve public health.

Health risks caused by short term exposure to ultrafine particles generated by residential wood combustion: a case study of Temuco, Chile.

Temuco is one of the most highly wood smoke polluted cities in Chile; however, there is scarce evidence of respiratory morbidity due to fine particulate matter. We aimed to estimate the relationship between daily concentration of ultrafine particles (UFP), with an aerodynamic diameter ≤ 0.1 µm, and outpatient visits for respiratory illness at medical care centers of Temuco, Chile, from August the 20th, 2009 to June the 30th, 2011. The Air Pollution Health Effects European Approach (APHEA2) protocol was followed, and a multivariate semi-parametric Poisson regression model was fitted with GAM techniques using R-Project statistical package; controlling for trend, seasonality, and confounders. The daily UFP were measured by a MOUDI NR-110 sampler. We found that results of the statistical analyses show significant associations between UFP and respiratory outpatient visits, with the elderly (population ≥ 65 years), being the group that presented the greatest risk. An interquartile increase of 4.73 µg/m(3) in UFP (lag 5 days) was associated with respiratory outpatient visits with a relative risk (RR) of 1.1458 [95% CI (1.0497-1.2507)] for the elderly. These results show novel findings regarding the relevance of daily UFP concentrations and health risk, especially for susceptible population in a wood smoke polluted city.

Obtaining polycyclic aromatic hydrocarbon concentration ratios and molecular markers for residential wood combustion: Temuco, a case study.

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 < or = 10 (PM10) and < or = 2.5 (PM2.5) microm 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.

Particulate air pollution and health effects for cardiovascular and respiratory causes in Temuco, Chile: a wood-smoke-polluted urban area.

Temuco is one of the most highly wood-smoke-polluted cities in the world. Its population in 2004 was 340,000 inhabitants with 1587 annual deaths, of which 24% were due to cardiovascular and 11% to respiratory causes. For hospital admissions, cardiovascular diseases represented 6% and respiratory diseases 13%. Emergency room visits for acute respiratory infections represented 28%. The objective of the study presented here was to determine the relationship between air pollution from particulate matter less than or equal to 10 microm in aerodynamic diameter (PM10; mostly PM2.5, or particulate matter <2.5 microm in aerodynamic diameter) and health effects measured as the daily number of deaths, hospital admissions, and emergency room visits for cardiovascular, respiratory, and acute respiratory infection (ARI) diseases. The Air Pollution Health Effects European Approach (APHEA2) protocol was followed, and a multivariate Poisson regression model was fitted, controlling for trend, seasonality, and confounders for Temuco during 1998-2006. The results show that PM10 had a significant association with daily mortality and morbidity, with the elderly (population >65 yr of age) being the group that presented the greatest risk. The relative risk for respiratory causes, with an increase of 100 microg/m3 of PM10, was 1.163 with a 95% confidence interval (CI) of 1.057-1.279 for mortality, 1.137 (CI 1.096-1.178) for hospital admissions, and 1.162 for ARI (CI 1.144-1.181). There is evidence in Temuco of positive relationships between ambient particulate levels and mortality, hospital admissions, and ARI for cardiovascular and respiratory diseases. These results are consistent with those of comparable studies in other similar cities where wood smoke is the most important air pollution problem.