Towards the sustainable and circular bioeconomy: Insights on spent coffee grounds valorization

Towards a circular bioeconomy to produce methane by co-digestion of coffee and brewery waste using a mixture of anaerobic granular sludge and cattle manure as inoculum

Coffee processing wastes, such as solid (pulp and husk) and wastewater, co-digested with industrial brewery wastewater, serve as excellent substrates for generating methane in the anaerobic digestion process. This study compared methane production using different compositions of cattle manure (CM) and granular sludge from an Upflow Anaerobic Sludge Blanket (UASB) reactor used in poultry wastewater treatment (GS). Four anaerobic batch reactors (500 mL) were assembled, A (50% CM and 50% GS), B (60% CM and 40% GS), C (70% CM and 30% of GS) and D (60% CM and 40% GS). Equal concentrations of substrates were added to all reactors: pulp and husk pretreated by hydrothermolysis (1 g L-1), coffee (10 g COD L-1) and brewery (1.5 g COD L-1) wastewaters. Assays A, B and C were supplemented with 2 g L-1 of yeast extract, except for assay D. The reactors were operated at 37 °C and pH 7.0. In assay B, the highest CH4 production of 759.15 ± 19.20 mL CH4 g-1 TS was observed, possibly favored by the synergistic interactions between cellulolytic bacteria Christensenellaceae_R-7_group and Methanosaeta archaea, as inferred by genes encoding enzymes related to acetoclastic methanogenesis (acetyl-CoA synthetase). Consequently, the electricity production potential of assay B (45614.08 kWh-1 year-1) could meet the energy demand of a farm producing coffee and beer, contributing to a positive energy balance concerning methane generation.

Energy audit and associated carbon footprint estimation for a Meta Abo brewery

Industrial development in Ethiopia is rapidly increasing, leading to a growing gap between energy supply and demand. To address this, efficient energy utilization in existing industries is crucial. Energy audits identify energy losses and recommend saving measures. Therefore, this study evaluates energy efficiency through an audit and estimates greenhouse gas emissions for a Meta Abo brewery. The indirect method of energy audit and the greenhouse gas protocol of carbon footprint estimation were used to evaluate the energy efficiency and carbon emissions of Meta Abo brewery. The boiler efficiency for Bono Energia and Cochran boilers was found to be 79.2% and 80.9%, respectively. Poor insulation caused an estimated annual fuel loss of 35,350 l (638,768 Ethiopian birr) for steam pipes, while steam leakage resulted in a loss of 31,614 l (571,265 Ethiopian birr). The factory's high electricity expense was attributed to a diesel generator consuming 6000 l/d. Greenhouse gas emissions raised from 9156 to 22,697 tons of CO2 equivalent between 2014 and 2018. Implementing the proposed energy-saving measures could save 20.4 TJ of thermal and electrical energy annually, costing approximately 8.5 million Ethiopian birr, and reduce boiler emissions by 455 tons of CO2 equivalent. Therefore, implementation of these measures is recommended.

Utilization of coffee waste as a sustainable feedstock for high-yield lactic acid production through microbial fermentation

Lactic acid is an important industrial precursor; however, high substrate costs are a major challenge in microbial fermentation-based lactic acid production. Coffee waste is a sustainable feedstock alternative for lactic acid production via microbial fermentation. Herein, the feasibility of coffee waste as a feedstock was explored by employing appropriate pretreatment methods and optimizing enzyme combinations. Coffee waste pretreatment with hydrogen peroxide and acetic acid along with a combination of Viscozyme L, Celluclast 1.5 L, and Pectinex Ultra SP-L achieved the 78.9 % sugar conversion rate at a substrate concentration of 4 % (w/v). Lactiplantibacillus plantarum WiKim0126-induced fermentation with a 4 % solid loading yielded a lactic acid concentration of 22.8 g/L (99.6 % of the theoretical maximum yield) and productivity of 0.95 g/L/h within 24 h. These findings highlight the viability of coffee waste as an eco-friendly resource for sustainable lactic acid production.

PLA Feedstock Filled with Spent Coffee Grounds for New Product Applications with Large-Format Material Extrusion Additive Manufacturing

Food waste and loss generate significant waste such as spent coffee grounds (SCGs) from coffee consumption. These byproducts can be valorized by following circular economy and bioeconomy principles, e.g., using SCGs in polymer-based composites for 3D printing. Although desktop-size material extrusion additive manufacturing is increasingly adopted for biomass-polymer-based composites, the potential of large-format direct extrusion 3D printing systems remains unexplored. This work investigated the thermal, rheological, and mechanical properties of PLA/SCG composites for applications with a large-format pellet extrusion 3D printer. The formulations exhibit minimal degradation at typical 3D printing temperatures of PLA, i.e., ∼190 °C, and limited effects on crystallinity by increasing the SCG weight percentage. The decrease in viscosity due to SCGs improves the printability and layer adhesion, as confirmed by the tensile test results, such as higher ultimate tensile strength and elongation at break values compared to those of the state-of-the-art values. Using pellet feedstocks contributes to limiting the effects of thermomechanical degradation by reducing raw material processing, i.e., avoiding filament extrusion. Using PLA/SCGs formulations was demonstrated through 3D printed complex parts with nonplanar slicing techniques, including a large-scale furniture product, validating large-format pellet extrusion 3D printers for scaling up the use of biomass-filled polymers.

Thermal Contaminants in Coffee Induced by Roasting: A Review

Roasting is responsible for imparting the main characteristics to coffee, but the high temperatures used in the process can lead to the formation of several potentially toxic substances. Among them, polycyclic aromatic hydrocarbons, acrylamide, furan and its derivative compounds, α-dicarbonyls and advanced glycation end products, 4-methylimidazole, and chloropropanols stand out. The objective of this review is to present a current and comprehensive overview of the chemical contaminants formed during coffee roasting, including a discussion of mitigation strategies reported in the literature to decrease the concentration of these toxicants. Although the formation of the contaminants occurs during the roasting step, knowledge of the coffee production chain as a whole is important to understand the main variables that will impact their concentrations in the different coffee products. The precursors and routes of formation are generally different for each contaminant, and the formed concentrations can be quite high for some substances. In addition, the study highlights several mitigation strategies related to decreasing the concentration of precursors, modifying process conditions and eliminating/degrading the formed contaminant. Many of these strategies show promising results, but there are still challenges to be overcome, since little information is available about advantages and disadvantages in relation to aspects such as costs, potential for application on an industrial scale and impacts on sensory properties.

Mechanisms Underlying Neurodegenerative Disorders and Potential Neuroprotective Activity of Agrifood By-Products

Neurodegenerative diseases, characterized by progressive loss in selected areas of the nervous system, are becoming increasingly prevalent worldwide due to an aging population. Despite their diverse clinical manifestations, neurodegenerative diseases are multifactorial disorders with standard features and mechanisms such as abnormal protein aggregation, mitochondrial dysfunction, oxidative stress and inflammation. As there are no effective treatments to counteract neurodegenerative diseases, increasing interest has been directed to the potential neuroprotective activities of plant-derived compounds found abundantly in food and in agrifood by-products. Food waste has an extremely negative impact on the environment, and recycling is needed to promote their disposal and overcome this problem. Many studies have been carried out to develop green and effective strategies to extract bioactive compounds from food by-products, such as peel, leaves, seeds, bran, kernel, pomace, and oil cake, and to investigate their biological activity. In this review, we focused on the potential neuroprotective activity of agrifood wastes obtained by common products widely produced and consumed in Italy, such as grapes, coffee, tomatoes, olives, chestnuts, onions, apples, and pomegranates.