The present study investigates a two-stage process aimed at producing biogas from food waste leachates (FWL) through an experimental approach. The first stage involves biohydrogen production via dark fermentation (DF), while the second focuses on biomethane production through anaerobic digestion (AD). The substrate consists of leachates derived from fruit and vegetable waste, which are introduced into two continuous stirred-tank reactors (CSTR1) with two different inoculum-to-substrate ratios (ISR). Dark fermentation occurs in these reactors. The effluent from the CSTRs is then fed into two additional reactors for methanogenesis. All reactors operated under mesophilic conditions. During the DF stage, hydrogen yields were relatively low, with a maximum of 8.2 NmL H₂/g VS added (ISR = 0.3) and 6.1 NmL H₂/g VS added (ISR = 0.5). These results were attributed to limited biodegradation of volatile solids (VS), which reached only 21.9% and 23.6% in each respective assay. Similarly, the removal of organic matter was modest. In contrast, the AD stage demonstrated more robust methane production, achieving yields of 275.2 NmL CH₄/g VS added (ISR = 0.3) and 277.5 NmL CH₄/g VS added (ISR = 0.5). The system exhibited significant organic matter degradation, with VS biodegradability reaching 66%, and COD removal efficiencies of 50.8% (ISR = 0.3) and 60.1% (ISR = 0.5). The primary focus of the study was to monitor and quantify the production of the two biofuels, biohydrogen and biomethane. In conclusion, this study provides an assessment of the two biochemical conversion pathways, detailing the generation of two valuable and utilizable gaseous products. This research examines the process-specific operational conditions governing gas production, with a focus on optimizing process parameters to enhance yield and overall efficiency.

Goat milk and cheese are popular dairy products known for their nutritional value and distinct flavors. The presence of bioactive compounds such as carotenoids and volatile compounds in these products contributes to their sensory characteristics and potential health benefits. This study aims to compare the content of bioactive compounds in goat milk and the cheese that was produced thereof. High Performance Liquid Chromatography (HPLC) equipped with diode array detector (DAD) was used for the quantification of beta carotene and lutein content. The lutein content in milk samples displayed higher values ranging between 0.11 and 0.25 mg/100 g per sample compared to cheese samples. Beta Carotene was not detected in either of the matrices. For the identification of volatile compounds, Solid Phase Microextraction/Gas Chromatography-Mass Spectrometry (SPME/GCMS) were used. The volatile compounds detected were classified into terpenes, ketones, aldehydes, acids and esters. Esters constituted the most abundant group of compounds in all samples. The simultaneous analysis of these compounds provides valuable insights into the nutritional composition, flavor profiles, and potential health benefits of goat cheese and milk. At last, the major elements comparison of milk and cheese products, including Calcium (Ca), Phosphorus (P), Potassium (K), Sodium (Na), Magnesium (Mg), Chlorine (Cl) and Sulfur (S), were quantitatively measured across all samples using a wavelength dispersive X-ray Fluorescence (WD-XRF) to establish their elemental profiles. Milk samples exhibited higher concentrations of Potassium. Conversely, cheese products displayed elevated levels on all the other elements.

According to the European Union data, on average 173 kg per person of total food waste (organic waste) is produced annually, of which 92 kg per person comes from households (organic waste). Food waste is defined as the waste from households, restaurants, canteens, and food industries, as well as markets. The importance of food waste stretches from the environmental pressures to the economic and social impacts. An environmental technology for the biodegradation of food waste is anaerobic digestion. It is a very attractive technique and combines waste treatment and renewable energy recovery. This study investigates the characteristics of food waste leachates from composting buckets and their valorization as a substrate for the anaerobic digestion process. A complete characterization of different food waste leachates was conducted (pH, COD, VFAs, heavy metals, etc.). The food waste leachates proved to be an ideal feedstock for anaerobic digestion. In this direction, batch tests were performed to evaluate the methane yield of the food waste leachates under different operating conditions. Three different SIR ratios were tested (0.5, 1.0, and 1.5). An SIR equal to 0.5 proved to be the best as the higher methane yield was achieved. The removal of the COD under all the operating conditions was higher than 70%, with the higher removal (85.18%) for an SIR equal to 1.5.

The mercury content is among the parameters that characterise the quality of Solid Recovered Fuels (SRFs), which constitute alternative solid fuels of increasing interest. In this study, a direct mercury analyser was utilised in the analyses of SRF samples originating from Automotive Shredded Residues (ASRs). Two SRFs and one liquid reference material were measured to test the accuracy and sensitivity of the instrument. The mean values of the two SRFs and one liquid reference material (RM) were 0.171, 0.324 mg/kg, and 0.141 mg/L. These values were compared with the reference ones as follows: 0.168, 0.382 mg/kg, and 0.137 mg/L. Mercury content was detected in the analysis samples of four different particle sizes (8 mm, 2 mm, 1 mm, 0.5 mm, and 0.25 mm) for each SRF sample in order to demonstrate the direct mercury analyser operation and to compare it as an alternative to mercury determination via atomic absorption spectrometry. The measurements showed that grinding down to 1 mm was sufficient for most SRF cases while grinding down to 2 mm might be enough for a few cases. As an overall conclusion, the direct mercury analyser can be regarded as an efficient laboratory tool, offering a robust alternative to the atomic absorption spectrometry procedure, especially in terms of accuracy, speed, safety, and cost-effectiveness.

This work offers a comprehensive examination of ICP-MS as a higher-level analytical method compared to atomic absorption spectrometry (AAS) and X-ray fluorescence (XRF). Comparisons between the ICP-MS average mean difference and AAS were made with the determination of the concentration of trace elements in the same solid alternative fuel samples, while comparisons between ICP-MS and XRF were made by the determination of the concentration of major elements in the same solid alternative fuel samples, resulting in the superiority of the method. The results of the relative mean differences (RDMs) between ICP-MS (7.56%) and XRF (9.42%) regarding the concentration of major elements compared with the reference values in solid biofuel samples, while the RDMs for the solid recovered fuel samples were 8.9% for ICP-MS and 12.27% for XRF. The same procedure was followed for the determination of the concentration of trace elements with ICP-MS and AAS, thus obtaining the results for solid biofuel samples (average %RMD_ICP-MS = 12.77 and RMD_AAS = 13.9) and SRF samples (average %RMD_ICP-MS = 10.02 and RDM_AAS = 11.10) in relation to the reference values. While acknowledging that the initial cost and complexity of operation may deter some from adopting ICP-MS, the study asserts that the advantages of enhanced precision, sensitivity and speed of analysis validate the investment. Hence, ICP-MS is an extremely important laboratory tool used in modern physics and chemistry and has a wide range of applications: biological materials, high purity reagents and metals, atomic nuclear materials, geological samples and food.