One attraction of using hydrochar (HC) and biochar (BC) in soil is their intrinsic affinity for organic contaminants. Oxidative ageing is likely to induce changes in physicochemical properties and functionality. To explore the long-term potential trajectories for corn stalk HC and BC to adsorb organic pollutants, we employed HC and BC exposure in 5% H2O2 to simulate oxidative ageing and get insights into mechanisms of atrazine adsorption on fresh and artificially aged materials. The physicochemical properties of fresh and aged materials were systematically compared using elemental analysis, SSA, FTIR, XPS and SEM-EDS, alongside K2Cr2O7/H2SO4 treatment to assess chemical oxidation stability. Atrazine is a typical herbicide chemical and hydrophobic organic pollutant. Adsorption isotherms of atrazine were used to reveal differences in mechanisms of sorption to BC and HC, by assessment before and ageing. BC freshly produced at 650 °C displayed higher capacity for atrazine sorption than BC produced at 500 °C, with a dominant role for π-π EDA interactions. The sorption capacity of HC freshly produced at 250 °C was higher than for HC produced at 200 °C HC, owing to higher C content and atrazine partitioning into the organic phase. Ageing increased the surface abundance of oxygenated functional groups for BC and HC and diminished bulk aromaticity. After ageing, atrazine sorption by high temperature BC was lower, but for HC it was increased. Such divergent effects must be considered when developing strategies to co-manage contaminants and carbon through the addition of carbonized materials to land.

The production of extra virgin olive oil (EVOO) flavored with diverse spices, herbs, fruits, and vegetables or natural aromas is believed to provide advantageous properties considering either the high nutritional value or biological activity in addition to the flavoring and industrial aspects. The biological activities including antioxidant and antimicrobial properties of Tunisian EVOO obtained from “Chemlali” variety and mixed with chili pepper were investigated. Molecular analyses, including the detection of twelve olive-infecting viruses and Pseudomonas savastanoi pv savastanoi, were performed to ensure that the samples were obtained from healthy olive trees and EVOO quality was not affected. Quality parameters like free acidity, peroxide number, oxidative stability, and specific absorption at K232 nm and K270 nm were also investigated and no significant variation was revealed. The content of minor compounds such as chlorophylls, carotenoids, and total phenols showed minor changes. However, the profiles of the volatile compounds showed remarkable differences, which appeared to be the main factor for the observed variability in consumer acceptance. The results showed for the first time high quantities of polyphenols and ortho-diphenols. Four colorimetric methods were used for the determination of the antioxidant activity, namely DPPH, ABTS, FRAP, and β-carotene test. Compared to the control, a higher level of antioxidant activity was observed for the flavored EVOO. Furthermore, significant results were obtained in the antimicrobial tests. The quality parameters of the mixture showed no alteration compared to the control. Finally, all the measurements and the chemical characterization gave a scientific basis for food technology innovation of new food products.

The present study reports the use of Citrus limetta (CL) residue for cultivating Chlorella sp. mixotrophically to augment production of biodiesel. The cultivation of Chlorella sp. using CL as media was carried out by employing a fed-batch technique in open tray (open tray+CL) and in software (BioXpert V2)–attached automated photobioreactor (PBR+CL) systems. Data showed the limit of nitrogen substituent and satisfactory organic source of carbon (OSC) in CL, causing > 2-fold higher lipid content in cells, cultivated in both the systems than in control. For the cells grown in both the systems, ≥ 3-fold enhancement in lipid productivity was observed than in control. The total fatty acid methyl ester (FAME) concentrations from lipids extracted from cells grew in PBR+CL and in open tray+CL techniques were calculated as 50.59% and 38.31%, respectively. The PBR+CL system showed improved outcomes for lipid content, lipid and biomass productivity, FAME characteristics and physical property parameters of biodiesel than those obtained from the open tray+CL system. The physical property parameters of biodiesel produced from algal cells grown in PBR+CL were comparable to existing fuel standards. The results have shown lower cold filter plugging point (− 6.57 °C), higher cetane number (58.04) and average oxidative stability (3.60 h). Collectively, this investigation unveils the novel deployment of CL as a cost-effective feedstock for commercialisation of biodiesel production.

Bio-mix is a fuel derived from the raw mixture of different non-edible oils to enhance the saturation level. In this study, raw oil mixture was transesterified to form bio-mix methyl ester (BMME). Fuel properties of BMME was measured and results showed that saturated fatty acids (SFA), cetane number (CN), and oxidation stability (OS) were increased, whereas density, viscosity, HHV, flash point, iodine number, and acid number were decreased for BMME as compared to individual biodiesels. Brake specific energy consumption (BSEC) of BMME was higher than diesel fuel but similar to individual biodiesel, while brake thermal efficiency (BTE) was lower than diesel fuel but higher than the individual biodiesel. (NOₓ) and CO₂ emission of BMME was found lower (approximately 20%); meanwhile, smoke opacity and CO emission biodiesel increased compared to diesel fuel, whereas (HC) emission of BMME was lower at low load condition but it is increased at high load. Bio-mix fuel could be the good replacement of diesel fuel.

The higher areal productivity and lipid content of microalgae and aquatic weed makes them the best alternative feedstocks for biodiesel production. Hence, an efficient and economic method of extracting lipid or oil from aquatic weed, Salvinia molesta is an important step towards biodiesel production. Since Salvinia molesta is an unexplored feedstock, its total lipid content was first measured as 16 % using Bligh and Dyer’s method which was quite sufficient for further investigation. For extracting more amount of lipid from Salvinia molesta, methanol: chloroform in the ratio 2:1 v/v was identified as the most suitable solvent system using Soxhlet apparatus. Based on the literature and the preliminary experimentations, parameters such as solvent to biomass ratio, temperature, and time were identified as significant for lipid extraction. These parameters were then optimized using response surface methodology with central composite design, where experiments were performed using twenty combinations of these extraction parameters with Minitab-17 software. A lipid yield of 92.4 % from Salvinia molesta was obtained with Soxhlet apparatus using methanol and chloroform (2:1 v/v) as solvent system, at the optimized conditions of temperature (85 °C), solvent to biomass ratio (20:1), and time (137 min), whereas a predicted lipid yield of 93.5 % with regression model. Fatty acid methyl ester (FAME) analysis of S. molesta lipid using gas chromatograph mass spectroscopy (GCMS) with flame ionization detector showed that fatty acids such as C16:0, C16:1, C18:1, and C18:2 contributed more than 9 % weight of total fatty acids. FAME consisted of 56.32, 28.08, and 15.59 % weight of monounsaturated, saturated, and polyunsaturated fatty acids, respectively. Higher cetane number and superior oxidation stability of S. molesta FAME could be attributed to its higher monounsaturated content and lower polyunsaturated content as compared to biodiesels produced from C. vulgaris, Sunflower, and Jatropha.

The study represents a comprehensive analysis of engine exhaust emission variation from a compression ignition (CI) diesel engine fueled with diesel-biodiesel blends. Biodiesel used in this investigation was produced through transesterification procedure from Moringa oleifera oil. A single cylinder, four-stroke, water-cooled, naturally aspirated diesel engine was used for this purpose. The pollutants from the exhaust of the engine that are monitored in this study are nitrogen oxide (NO), carbon monoxide (CO), hydrocarbon (HC), and smoke opacity. Engine combustion and performance parameters are also measured together with exhaust emission data. Some researchers have reported that the reason for higher NO emission of biodiesel is higher prompt NO formation. The use of antioxidant-treated biodiesel in a diesel engine is a promising approach because antioxidants reduce the formation of free radicals, which are responsible for the formation of prompt NO during combustion. Two different antioxidant additives namely 2,6-di-tert-butyl-4-methylphenol (BHT) and 2,2′-methylenebis(4-methyl-6-tert-butylphenol) (MBEBP) were individually dissolved at a concentration of 1% by volume in MB30 (30% moringa biodiesel with 70% diesel) fuel blend to investigate and compare NO as well as other emissions. The result shows that both antioxidants reduced NO emission significantly; however, HC, CO, and smoke were found slightly higher compared to pure biodiesel blends, but not more than the baseline fuel diesel. The result also shows that both antioxidants were quite effective in reducing peak heat release rate (HRR) and brake-specific fuel consumption (BSFC) as well as improving brake thermal efficiency (BTE) and oxidation stability. Based on this study, antioxidant-treated M. oleifera biodiesel blend (MB30) can be used as a very promising alternative source of fuel in diesel engine without any modifications.

Different microalgae species produce varying quantity and quality of the lipids. Fatty acid methyl ester composition, which comprises both saturated and unsaturated contents, critically affects biodiesel properties. Current study compares six locally isolated microalgae strains belonging to three classes (Trebouxiophyceae, Chlorophyceae, and Cyanophyceae) on the basis of lipid content and biodiesel properties. All the six species are grown in similar condition up to the late stationary phase, and their lipid content and fatty acid methyl ester composition are measured experimentally. Multi-criteria decision analysis (MCDA) tool has ranked Calothrix species (class Cyanophyceae) on the top, owing to better cetane number, density and oxidation stability; whereas Chlorococcum species (class Chlorophyceae) is ranked second because of its higher lipid content, better cold flow property, and low viscosity. Property analysis of these two species is extended in the enlarge temperature range for five properties, vapor pressure, latent heat of vaporization, liquid density, liquid viscosity and vapor diffusivity, which are important in spray and combustion modeling. It is found through detailed property estimation that Chlorococcum sp. is a more suitable species in comparison with Calothrix sp. as it is having better properties and its lipid content is much higher than that of Calothrix sp. Although the properties of microalgae biodiesel are poorer in comparison with conventional diesel fuel, a greater number of such studies will help in understanding the requisite changes as required for microalgae biodiesel–based engine and their properties as compared with conventional diesel.

Biodiesel and single cell oils obtained from oleaginous yeasts grown in industrial waste are attractive alternatives to the conventional fuels. However, there are only few articles dealing with the stability of the microbial biofuels. Hence, this study aimed at characterizing the storage time of biodiesels using Rancimat methods. The microbial oil and the biodiesel obtained from microbial oil have been characterized with storage stability due to various oxidizing and thermal damage. Here, the microbial fuels were subject to Rancimat analysis and found to have high thermal-oxidative stability of 18 and 8.78 h for biodiesel and oil, respectively. The storage stability resulting from storage conditions was extrapolated for biodiesel and oil and has been found to be 1.62 and 0.54 years, respectively. The infrared spectroscopic analysis reveals the degree of oxidation found after the induction time was reached and shows the characteristic peaks for degradation products. Gas chromatography revealed the compounds that were responsible for the stability as well as the amount of degradation products left.

The present work analyzes the effect of antioxidants on engine combustion performance of a multi-cylinder diesel engine fueled with PB30 and PB50 (30 and 50 vol.% palm biodiesel (PB)). Four antioxidants namely N,N′-diphenyl-1,4-phenylenediamine (DPPD), N-phenyl-1,4-phenylenediamine (NPPD), 2(3)-tert-Butyl-4-methoxyphenol (BHA), and 2-tert-butylbenzene-1,4-diol (TBHQ) were added at concentrations of 1000 and 2000 ppm to PB30 and PB50. TBHQ showed the highest activity in increasing oxidation stability in both PB30 and PB50 followed by BHA, DPPD, and NPPD respectively, without any negative effect on physical properties. Compared to diesel fuel, PB blends showed 4.61–6.45% lower brake power (BP), 5.90–8.69% higher brake specific fuel consumption (BSFC), 9.64–11.43% higher maximum in cylinder pressure, and 7.76–12.51% higher NO emissions. Carbon monoxide (CO), hydrocarbon (HC), and smoke opacity were reduced by 36.78–43.56%, 44.12–58.21%, and 42.59–63.94%, respectively, than diesel fuel. The start of combustion angles (SOC) of PB blends was − 13.2 to − 15.6 °CA BTDC, but the combustion delays were 5.4–7.8 °CA short compared to diesel fuel which were − 10 °CA BTDC and 11°CA respectively. Antioxidant fuels of PB showed higher BP (1.81–5.32%), CO (8.41–24.60%), and HC (13.51–37.35%) with lower BSFC (1.67–7.68%), NO (4.32–11.53%), maximum in cylinder pressure (2.33–4.91%) and peak heat release rates (HRR) (3.25–11.41%) than baseline fuel of PB. Similar SOC of − 13 to − 14 °CA BTDC was observed for PB blended fuels and antioxidants. It can be concluded that antioxidants’ addition is effective in increasing the oxidation stability and in controlling the NOx emissions of palm biodiesel fuelled diesel engine.