Use of the Solid By-Product of Anaerobic Digestion of Biomass to Remove Anthropogenic Organic Pollutants with Endocrine Disruptive Activity

Anaerobic digestion of biomass has increasing implementation for bioenergy production. The solid by-product of this technology, i.e., the digestate, has relevant potential in agricultural and environmental applications. This study explored the capacity of a digestate from mixed feedstock to remove from water four endocrine-disrupting chemicals, namely the pesticides metribuzin (MET) and boscalid (BOS) and the xenoestrogens bisphenol A (BPA) and 4-tert-octylphenol (OP). The surface micromorphology and functional groups of the digestate were investigated using scanning electron microscopy (SEM) and Fourier-transform infrared (FTIR) spectroscopy, respectively. Results of sorption kinetics showed that all compounds reached the steady state in a few hours according to a pseudo-first-order model in the cases of MET and OP, a pseudo-second-order model for BOS and both models in the case of BPA. Data of adsorption isotherms were fitted to the Henry, Freundlich, Langmuir and Temkin equations. The adsorption of MET preferentially followed the non-linear Freundlich model, whereas the adsorption of the other compounds was properly described by both the linear and Freundlich models. The organic carbon partition coefficients, KOC, were 170, 1066, 256 and 2180 L kg−1 for MET, BOS, BPA and OP, respectively. The desorption of BOS, BPA and OP was slow and incomplete, indicating a phenomenon of hysteresis. In conclusion, the digestate showed a remarkable efficiency in the removal of the compounds, especially those with high hydrophobicity, thus behaving as a promising biosorbent for environmental remediation.

Recent advancements in biochar production according to feedstock classification, pyrolysis conditions, and applications: A review

Biochar is highly valuable in various applications due to its unique physicochemical properties such as high thermal efficiency, high surface area, surface functional groups, and crystal structure. The goal of this review is to establish a systematic strategy of biochar production for applications in various fields. First, the characteristics of biomass as feedstock for biochar production and their classification are discussed according to the types present in nature. Second, the technology for biochar production and the production yield are examined. In thermochemical conversion for biochar production, five major types of pyrolysis processes are suggested, and the production yield is evaluated according to pyrolysis parameters (feedstock pretreatment, operating temperature, heating rate, residence time, carrier gas). In addition, biochar production from pyrolysis of mixed feedstock has recently been suggested; thus, the evaluation of the production yield from co-pyrolysis is included. Finally, analytical techniques for biochar characterization are investigated and the application of biochar in various fields is considered, such as in adsorbents, energy storage devices, and catalysts.

A Model of Catalytic Cracking: Product Distribution and Catalyst Deactivation Depending on Saturates, Aromatics and Resins Content in Feed

The problems of catalyst deactivation and optimization of the mixed feedstock become more relevant when the residues are involved as a catalytic cracking feedstock. Through numerical and experimental studies of catalytic cracking, we optimized the composition of the mixed feedstock in order to minimize the catalyst deactivation by coke. A pure vacuum gasoil increases the yields of the wet gas and the gasoline (56.1 and 24.9 wt%). An increase in the ratio of residues up to 50% reduces the gasoline yield due to the catalyst deactivation by 19.9%. However, this provides a rise in the RON of gasoline and the light gasoil yield by 1.9 units and 1.7 wt% Moreover, the ratio of residue may be less than 50%, since the conversion is limited by the regenerator coke burning ability.

Dissolved organic matter and bacterial population changes during the treatment of solid potato waste in a microbial fuel cell

This study investigated the effect of mixed feeding of anaerobically cultured waste activated sludge (WAS) on the performance of microbial fuel cells (MFCs) in the treatment of solid potato waste. The maximum current densities of the four MFCs was estimated as 36, 5, 10 and 150 mA/m2, with the columbic efficiencies of 6.1, 0.3, 0.9 and 31.1%, respectively. Composition changes of dissolved organic matter (DOM) coupled with its interrelation with electricity generation and total and viable bacterial population at the end of the operation were investigated. The experimental results demonstrated that mixing WAS into solid potato enhanced the presence of the tyrosine-like aromatic amino acids and aromatic protein-like substances from the beginning of the operation and promoted hydrolysis and humification of the solid potato. In the final solution of the anodic chamber, more viable bacteria were detected for the reactors treating solid potato alone and the mixed feedstock with the smaller amount of sludge, where distinct electricity generation was observed.

Product Distribution and Characteristics of Pyrolyzing Microalgae (Nannochloropsis oculata), Cotton Gin Trash, and Cattle Manure as a Cobiomass

Microalgae has proven potential for producing products that are accepted as an alternate energy source. An attempt is made to further improve the efficiency of pyrolysis in terms of product yields and characteristics by adding cotton gin trash and cattle manure as a mixed feedstock (cobiomass). A statistically significant number of treatments were made by mixing different amounts of cotton gin trash and cattle manure with microalgae (Nannochloropsis oculata). These treatments were pyrolyzed at different temperatures (400 to 600 °C ) and product yields and characteristics were analyzed. The pyrolysis of cobiomass resulted in higher yield for bio-oil and char as compared to microalgae alone. An operating temperature of 500 °C was found to be the best suitable for high bio-oil yield. The high heating values (hhv) of bio-oil were observed to be maximum at 500 °C and for syngas and char, the heating value slightly increased with further increase in temperature. Comparatively, the bio-oil (30 MJ/kg) had higher heating values than char (17 MJ/kg) and syngas (13 MJ/kg). The combustible material decreased whereas fixed carbon and ash content increased in char with an increase in temperature. The bio-oil produced from cobiomass had abundant aliphatics and aromatics with low nitrogen content making it a better alternative fuel than bio-oil produced by microalgae alone. The mixing of different biomass helped improving not just the quantity but also the quality of products.