Spent coffee ground characterization, pelletization test and emissions assessment in the combustion process

Industrial development and increased energy requirements have led to high consumption of fossil fuels. Thus, environmental pollution has become a profound problem. Every year, a large amount of agro-industrial, municipal and forest residues are treated as waste, but they can be recovered and used to produce thermal and electrical energy through biological or thermochemical conversion processes. Among the main types of agro-industrial waste, soluble coffee residues represent a significant quantity all over the world. Silver skin and spent coffee grounds (SCG) are the main residues of the coffee industry. The many organic compounds contained in coffee residues suggest that their recovery and use could be very beneficial. Indeed, thanks to their composition, they can be used in the production of biodiesel, as a source of sugar, as a precursor for the creation of active carbon or as a sorbent for the removal of metals. After a careful evaluation of the possible uses of coffee grounds, the aim of this research was to show a broad characterization of coffee waste for energy purposes through physical and chemical analyses that highlight the most significant quality indexes, the interactions between them and the quantification of their importance. Results identify important tools for the qualification and quantification of the effects of coffee waste properties on energy production processes. They show that (SCG) are an excellent raw material as biomass, with excellent values in terms of calorific value and low ash content, allowing the production of 98% coffee pellets that are highly suitable for use in thermal conversion systems. Combustion tests were also carried out in an 80kWth boiler and the resulting emissions without any type of abatement filter were characterized.

Effects of NaOH Activation on Adsorptive Removal of Herbicides by Biochars Prepared from Ground Coffee Residues

In this study, the adsorption of herbicides using ground coffee residue biochars without (GCRB) and with NaOH activation (GCRB-N) was compared to provide deeper insights into their adsorption behaviors and mechanisms. The physicochemical characteristics of GCRB and GCRB-N were analyzed using Brunauer–Emmett–Teller surface area, Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction and the effects of pH, temperature, ionic strength, and humic acids on the adsorption of herbicides were identified. Moreover, the adsorption kinetics and isotherms were studied. The specific surface area and total pore volume of GCRB-N (405.33 m2/g and 0.293 cm3/g) were greater than those of GCRB (3.83 m2/g and 0.014 cm3/g). The GCBR-N could more effectively remove the herbicides (Qe,exp of Alachlor = 122.71 μmol/g, Qe,exp of Diuron = 166.42 μmol/g, and Qe,exp of Simazine = 99.16 μmol/g) than GCRB (Qe,exp of Alachlor = 11.74 μmol/g, Qe,exp of Diuron = 9.95 μmol/g, and Qe,exp of Simazine = 6.53 μmol/g). These results suggested that chemical activation with NaOH might be a promising option to make the GCRB more practical and effective for removing herbicides in the aqueous solutions.

Agroindustry Residues as a Source for Cellulose Nanofibers Production

Our study was motivated by the large amount of crop residues produced in Brazil, which represent underutilized waste biomass and a serious threat to the environment because of the landfilling. For example, even though the corn crop is not popular in Brazil, it is produced in the area of around 18-20 million hectares with an average production of 5-6 t ha-1. That is the reason to seek for the crop residues value-added applications as proposed in the present study. Four Brazilian crop waste biomass: orange bagasse, corn husks, sugarcane straw and coffee residues were used for cellulose nanofibers (CNF) production. CNFs were prepared using alkali treatment, followed by bleaching with sodium chlorite and extraction with oxalic acid. All steps were applied under moderate conditions of temperature and pressure, such as temperature of 120 °C and below, water solutions with chemicals’ concentrations lower that 10% and short sonication pulses. CNFs with diameters in the range 50-70 nm were obtained and products from orange bagasse and corn husks presented high crystallinity indexes (CI), 0.72 and 0.75, respectively. The highest CNF yield was obtained from corn husks (38.5%) followed by sugarcane straw (24.0% with CI of 0.69). CNFs obtained from coffee residues showed a CI value of 0.65 after two bleaching steps. Different CNF morphologies were obtained according to the raw material. The four-crop waste biomass can be considered as excellent starting materials for CNF production in the four-steps process that adds new value to agro-industrial waste and might bring great economical valorization to Brazilian crops production.

Evaluación del proceso de hidrólisis de residuales sólidos del beneficio de café para la producción de enzimas lipasas

El café es uno de los principales productos agrícolas exportados en Ecuador, produciendo una gran cantidad de residuos como pulpa y cáscara (46 %) que se generan durante el proceso de post-cosecha de granos verdes de café. Estos residuos, de naturaleza lignocelulósica pueden ser aprovechados para la obtención de enzimas lipasas, según investigaciones de los últimos años. Sin embargo, para la producción de enzimas, se requieren etapas de pretratamiento del residuo. Este trabajo se centró en establecer las variables de operación del proceso de hidrólisis, previo la obtención de enzimas lipasas a partir de la fermentación de residuales sólidos del café en la etapa del beneficio, utilizando un hongo filamentoso Aspergillus niger como agente biológico de transformación. Dentro del trabajo se efectuó el pretratamiento alcalino del residual en dos corridas experimentales, para un total de 15 variantes: en la primera (9 variantes) se evaluó la concentración de NaOH y tiempo, en la segunda (6 variantes) temperatura y tiempo. Al residual hidrolizado se determinó rendimiento másico, lignina, nitrógeno y proteínas. Los resultados demostraron que el pretratamiento con NaOH al 6 %, 60 min y 121 °C remueve mayor porcentaje de lignina (69,26 ± 2,92 %) y 6 %, 60 min, 25 °C el mayor contenido de nitrógeno (1,52 ± 0,03 %). Mediante ANOVA y Prueba de Múltiples Rangos se determinó que no existen diferencias para 6 %, 60 min y por superficie de respuesta se estableció una temperatura de 35,67 ºC, condiciones utilizadas para la fermentación, obteniendo una actividad enzimática de 37,67 ± 0,58 U/g. Palabra clave: Coffea arabica L, hidrólisis alcalina, lignina, fermentación estado sólido, A. niger. Abstract Coffee is one of the main agricultural products exported in Ecuador, producing a large amount of waste such as pulp and peel (46 %) that are generated during the post-harvest process of green coffee beans. These residues, of a lignocellulosic nature, can be used to obtain lipase enzymes, according to research in recent years. However, for the production of enzymes, residue pretreatment steps are required. This work focused on establishing the operating variables of the hydrolysis process, before obtaining lipase enzymes from the fermentation of solid coffee residues in the beneficiation stage, using a filamentous fungus Aspergillus niger as a biological transformation agent. Within the work, the alkaline pretreatment of the residual was carried out in two experimental runs, for a total of 15 variants, in the first (9 variants) the NaOH concentration and time were evaluated, the second (6 variants) temperature and time. The hydrolyzed residual was determined by mass yield, lignin, nitrogen, and proteins. The results showed that pretreatment with NaOH at 6 %, 60 min, and 121 °C removes the highest percentage of lignin (69.26 ± 2.92 %) and 6 %, 60 min, 25 °C the highest nitrogen content (1.52 ± 0.03 %). Through ANOVA and Multiple Range Test, it was determined that there are no differences for 6 %, 60 min and by response surface, a temperature of 35.67 ºC was established, conditions used for fermentation, obtaining an enzymatic activity of 37.67 ± 0.58 U/g. Keywords: Arabic coffee, alkaline hydrolysis, lignin, solid-state fermentation, A. niger.