Effects of hydrotreated vegetable oil on emissions of aerosols and gases from light-duty and medium-duty older technology engines

Unlocking pilot-scale green diesel production from microalgae

Microalgae have emerged as a promising source of biomass to produce renewable biofuels due to their ability to synthesize high-energy density compounds of commercial interest. This study proposes an approach for pilot-scale oil extraction, purification by fractional distillation, hydrocarbon characterization by gas chromatography coupled to mass spectrometry (GC-MS), evaluation of physicochemical parameters of the produced hydrocarbons, preliminary cost analysis, and challenges and future opportunities for green diesel on a commercial scale. Here, the microalgae Tetradesmus obliquus was cultivated in 12 m³ photobioreactors using biodigested swine waste as a culture medium. The resulting biomass was subjected to drying and harvesting, followed by oil extraction using a hot solvent extraction method, followed by distillation to purify the compounds. Three different extraction and distillation experiments were conducted, each using different solvent combinations. The results obtained revealed that extraction with a solvent blend, composed of hexane and ethanol, provided more significant yields compared to extraction with pure hexane. GC-MS analysis showed the presence of alkanes and alkenes in the oil samples, and the proportion of solvent used in the extraction directly influenced the production of alkanes. Additionally, specific hydrocarbons such as 4-methyl-1-decene, 8-heptadecene, 1-pentadecene, 9-heneicosene, and 2-dodecene were identified. The evaluation of the physicochemical parameters demonstrated that the calorific value of the distilled oil samples is within the range of typical values for petroleum diesel. However, it was observed that the distilled oil samples had higher sulfur content compared to conventional diesel. Regarding the cost analysis, it was found that it varies depending on the experimental conditions. In particular, the process using a solvent mixture of 70% hexane and 30% ethanol proved to be more economical than the others, since it extracted a greater quantity of oil with a lower initial biomass requirement. In summary, this microalgae-derived hydrocarbon production process is promising and offers insights for compound purification and future biofuel applications.

Direct-reading instruments for aerosols: A review for occupational health and safety professionals part 2: Applications

Direct reading instruments (DRIs) for aerosols have been used in industrial hygiene practice for many years, but their potential has not been fully realized by many occupational health and safety professionals. Although some DRIs quantify other metrics, this article will primarily focus on DRIs that measure aerosol number, size, or mass. This review addresses three applications of aerosol DRIs that occupational health and safety professionals can use to discern, characterize, and document exposure conditions and resolve aerosol-related problems in the workplace. The most common application of aerosol DRIs is the evaluation of engineering controls. Examples are provided for many types of workplaces and situations including construction, agriculture, mining, conventional manufacturing, advanced manufacturing (nanoparticle technology and additive manufacturing), and non-industrial sites. Aerosol DRIs can help identify the effectiveness of existing controls and, as needed, develop new strategies to reduce potential aerosol exposures. Aerosol concentration mapping (ACM) using DRI data can focus attention on emission sources in the workplace spatially illustrate the effectiveness of controls and constructively convey concerns to management and workers. Examples and good practices of ACM are included. Video Exposure Monitoring (VEM) is another useful technique in which video photography is synced with the concentration output of an aerosol DRI. This combination allows the occupational health and safety professional to see what tasks, environmental situations, and/or worker actions contribute to aerosol concentration and potential exposure. VEM can help identify factors responsible for temporal variations in concentration. VEM can assist with training, engage workers, convince managers about necessary remedial actions, and provide for continuous improvement of the workplace environment. Although using DRIs for control evaluation, ACM and VEM can be time-consuming, the resulting information can provide useful data to prompt needed action by employers and employees. Other barriers to adoption include privacy and security issues in some worksites. This review seeks to provide information so occupational health and safety professionals can better understand and effectively use these powerful applications of aerosol DRIs.

Effects off hydrogenated vegetable oil (HVO) and HVO/biodiesel blends on the physicochemical and toxicological properties of emissions from an off-road heavy-duty diesel engine

In this study, the regulated emissions, gaseous toxics, and the physical, chemical, and toxicological properties of particulate matter (PM) emissions from a legacy off-road diesel engine operated on hydrogenated vegetable oil (HVO) and HVO blends with biodiesel were investigated. This is one of the very few studies currently available examining the emissions and potential health effects of HVO and its blends with biodiesel from diesel engines. Extended testing was conducted over the nonroad transient cycle (NRTC) and the 5-mode D2 ISO 8718 cycle. Nitrogen oxide (NOx) emissions showed statistically significant reductions for HVO compared to diesel, whereas the biodiesel blends statistically significant increases in NOx emissions. PM and solid particle number reductions with pure HVO and the biodiesel blends were also observed. Low-molecular weight polycyclic aromatic hydrocarbons (PAHs) were the dominant species in the exhaust for all fuels, with pure HVO and the biodiesel blends showing lower concentrations of these pollutants compared to diesel fuel. Our results showed that the oxidative stress and cytotoxicity in PM emissions decreased with the use of biofuels. Notable correlations were observed between PM emissions and oxidative stress and cytotoxicity, especially elemental carbon and particle-phase PAH emissions.

Diesel Aerosols in an Underground Coal Mine

The case study was conducted in an underground coal mine to characterize submicron aerosols at a continuous miner (CM) section, assess the concentrations of diesel aerosols at the longwall (LW) section, and assess the exposures of selected occupations to elemental carbon (EC) and total carbon (TC). The results show that aerosols at the CM sections were a mixture of aerosols freshly generated at the outby portion of the CM section and those generated in the main drifts that supply "fresh air" to the section. The relatively low ambient concentrations and personal exposures of selected occupations suggest that currently applied control strategies and technologies are relatively effective in curtailing exposures to diesel aerosols. Further reductions in EC and TC concentrations and personal exposures to those would be possible by more effective curtailment of emissions from high-emitting light duty (LD) vehicles.

Retrofitting and re-powering as a control strategies for curtailment of exposure of underground miners to diesel aerosols

A study was conducted to examine the potential of diesel emissions control strategies based on retrofitting existing power packages with exhaust aftertreatment devices and repowering with advanced power packages. The retrofit systems, a diesel oxidation catalyst (DOC) and diesel particulate filter (DPF), were evaluated individually using a US EPA tier 2 (ter 2) engine operated under four steady-state conditions and one transient cycle. The DOC effectively curtailed emissions of CO, and to some extent organic carbon (OC), elemental carbon (EC), and aerosol number concentration. The DPF system offered substantially higher reductions in OC and EC mass and aerosol number concentrations. Both, the DOC and DPF achieved reductions in the aforementioned emissions without adversely affecting emissions of NO2 and nano-sized aerosols. The strategy of repowering with an advanced system was examined using a US EPA tier 4 final (tier 4f) engine equipped with a cooled exhaust gas recirculation system and diesel exhaust fluid-based selective catalytic reduction system, but not with a DPF system. The tier 4f engine contributed substantially less than the tier 2 engine to the EC and OC mass, aerosol number, and CO, NO, and NO2 concentrations. The tier 4f engine was very effective in reducing aerosol mass, NO, and NO2 concentrations, but it was not equally effective in reducing aerosol number concentrations. The implementation of viable exhaust after treatment systems and advanced diesel power packages could be instrumental to the underground mining industry to secure a clean, economical, and dependable source of power for mobile equipment.

Diesel and welding aerosols in an underground mine

Researchers from the National Institute for Occupational Safety and Health (NIOSH) conducted a study in an isolated zone of an underground mine to characterize aerosols generated by: (1) a diesel-powered personnel carrier vehicle operated over a simulated light-duty cycle and (2) the simulated repair of existing equipment using manual metal arc welding (MMAW). Both the diesel-powered vehicle and MMAW process contributed to concentrations of nano and ultrafine aerosols in the mine air. The welding process also contributed to aerosols with electrical mobility and aerodynamic mobility count median diameters of approximately 140 and 480 nm, respectively. The welding particles collected on the filters contained carbon, iron, manganese, calcium, and aluminum.

Exhaust emissions from diesel engines fueled by different blends with the addition of nanomodifiers and hydrotreated vegetable oil HVO

Diesel emissions have a significant impact on the atmosphere, contributing to air pollution, smog and global warming. As a result, diesel exhaust is dangerous to human health. While emissions reduction efforts have often focused on changing engine design or improving aftertreatment, diesel fuel modifications can also play an important role in improving engine efficiency and reducing exhaust emissions. The aim of this work was to examine the potential for emissions reductions under real-world conditions when employing fuel additives. Three different additives were examined, consisting of hydrotreated vegetable oil (HVO) and two commercial additives containing nanoparticles of cerium dioxide and ferrocene. HVO was selected as a renewable fuel, an alternative to commonly used biodiesels with competitive advantages. The new European driving cycle (NEDC) procedure was used to measure emissions of regulated compounds: carbon monoxide, nitrogen oxides, hydrocarbons and particulates (by mass and number) from an 11-year-old passenger car equipped with a diesel engine powered by fuel blends. The fuel blends prepared met the quality requirements for diesel fuel. The results obtained confirm that the application of both HVO and nano-additives to diesel can achieve a significant reduction of carbon monoxide (52%) and hydrocarbon (47%) emissions compared to the B7 base fuel. Particulate emissions (up to 10% by mass of particulates and 7% by number of particulates) were found to be best reduced by adding nanoparticles of cerium dioxide to the B7 fuel (with 30% HVO), while the best results in reducing nitrogen oxide emissions were obtained by adding ferrocene nanoparticles to the B7 fuel with 30% HVO.

An Overview of the Influence of Biodiesel, Alcohols, and Various Oxygenated Additives on the Particulate Matter Emissions from Diesel Engines

Rising pollution levels resulting from vehicular emissions and the depletion of petroleum-based fuels have left mankind in pursuit of alternatives. There are stringent regulations around the world to control the particulate matter (PM) emissions from internal combustion engines. To this end, researchers have been exploring different measures to reduce PM emissions such as using modern combustion techniques, after-treatment systems such as diesel particulate filter (DPF) and gasoline particulate filter (GPF), and alternative fuels. Alternative fuels such as biodiesel (derived from edible, nonedible, and waste resources), alcohol fuels (ethanol, n-butanol, and n-pentanol), and fuel additives have been investigated over the last decade. PM characterization and toxicity analysis is still growing as researchers are developing methodologies to reduce particle emissions using various approaches such as fuel modification and after-treatment devices. To address these aspects, this review paper studies the PM characteristics, health issues, PM physical and chemical properties, and the effect of alternative fuels such as biodiesel, alcohol fuels, and oxygenated additives on PM emissions from diesel engines. In addition, the correlation between physical and chemical properties of alternate fuels and the characteristics of PM emissions is explored.

Exhaust Emissions and Physicochemical Properties of Hydrotreated Used Cooking Oils in Blends with Diesel Fuel

Hydroprocessing of liquid biomass is a promising technology for the production of “second generation” renewable fuels to be used in transportation. Its products, normal paraffins, can be further hydrotreated for isomerization in order to improve their cold flow properties. The final product, usually referred to as “paraffinic diesel,” is a high cetane number, clean burning biofuel which is rapidly gaining popularity among researchers and the industry. Nevertheless, the costly isomerization step can be omitted if normal paraffins are to be directly mixed with conventional diesel in low concentrations. In this work, nonisomerized paraffinic diesel produced through hydrotreating of used cooking oil (hydrotreated used cooking oil (HUCO)) has been used in 4 blends (up to 40% v/v) with conventional diesel fuel. The blends’ properties have been assessed comparatively to European EN 590 and EN 15940 standards (concerning conventional automotive diesel fuels and paraffinic diesel fuels from synthesis or hydrotreatment, resp.). Furthermore, the HUCO blends have been used in a standard stationary diesel engine-generator set. The blends have been considered as “drop-in replacements” for standard diesel fuel. As such, no engine modifications took place whatsoever. The engine performance and exhaust emissions of steady-state operation have been examined in comparison with engine operation with the baseline conventional diesel fuel.

Effects of FAME biodiesel and HVORD on emissions from an older-technology diesel engine

The results of laboratory evaluations were used to compare the potential of two alternative, biomass-derived fuels as a control strategy to reduce the exposure of underground miners to aerosols and gases emitted by diesel-powered equipment. The effects of fatty acid methyl ester (FAME) biodiesel and hydrotreated vegetable oil renewable diesel (HVORD) on criteria aerosol and gaseous emissions from an older-technology, naturally aspirated, mechanically controlled engine equipped with a diesel oxidation catalytic converter were compared with those of widely used petroleum-derived, ultralow-sulfur diesels (ULSDs). The emissions were characterized for four selected steady-state conditions. When fueled with FAME biodiesel and HVORD, the engine emitted less aerosols by total particulate mass, total carbon mass, elemental carbon mass and total number than when it was fueled with ULSDs. Compared with ULSDs, FAME biodiesel and HVORD produced aerosols that were characterized by single modal distributions, smaller count median diameters, and lower total and peak concentrations. For the majority of test cases, FAME biodiesel and HVORD favorably affected nitric oxide (NO) and adversely affected nitrogen dioxide (NO₂) generation. Therefore, the use of these alternative fuels appears to be a viable tool for the underground mining industry to address the issues related to emissions from diesel engines, and to transition toward more universal solutions provided by advanced engines with integrated exhaust after treatment technologies.