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.

Ammonia recovery from air stripping process applied to landfill leachate treatment.

The leachate is a type of effluent from landfills containing high concentrations of ammonia, even after normal treatment procedures are applied. Due to its characteristic, the leachate can adversely impact the environment and public health. Leachate treatment seeks to remove a series of compounds with adverse characteristics present in this type of effluent. Ammonia nitrogen is the main problem, easily observed in concentrations near 2000 mg/L. The effluents with high concentrations of ammonia nitrogen can stimulate the growth of algae, reduce the dissolved oxygen in rivers, and cause toxicity on the aquatic biota, even in low concentrations. Many research for treatment methods aiming to remove this compound, specifically, have been increasingly deeper, mainly by physical-chemical processes. This study aimed to test the process of air stripping in a closed system and pilot scale, applied on leachate treatment of landfills, to remove the high concentrations of ammonia nitrogen and its recovery by the chemical absorption of ammonia on phosphoric acid, resulting in a product with potential application as agricultural fertilizer, the ammonia phosphate. The leachate flows used were 9, 18, 20, and 40 L/h, and the air flows were 1800 and 3600 L/h. Calcium carbonate (standard grade), commercial hydrated lime (CHL), and sodium hydroxide (standard grade) were used for pH adjustments. To the ammonia recovery, three flasks were used with 2.5 L of a phosphoric acid solution of 0.12 and 0.24 mol/L. The air stripping tower removed an average of 98% of ammoniacal nitrogen, with an operating time of 4 to 9 days. The volume of air consumed to remove 1 g of ammoniacal nitrogen varied from 9, 91, and 21.6 m3. The ammonia recovery was about 92% using a phosphoric acid solution, producing the ammonia phosphate.