No abstract

No abstract

The final disposal of organic wastes has become a major challenge with increasing industrialization and population growth. Coffee wastes are examples of this, thus the conversion of these biomasses into biochar through pyrolysis could provide economic and environmental benefits, such as remediation of heavy metal polluted water. Therefore, in this work, biochar produced at 700 °C from spent coffee grounds and coffee parchment were evaluated for Zn removal from aqueous solution. Batch adsorption tests were performed with six Zn concentrations and four replicates for each material. The desorption process was performed sequentially with a pH 4.9 buffer acetic acid solution. Langmuir and Freundlich isotherms were fitted to the adsorption data using non-linear models. Batch adsorption tests showed that the adsorption was strongly dependent on biochar properties. Biochar prepared from coffee parchment was more effective at Zn binding, showing the highest adsorption capacity (0.792 mg g^-1). Nevertheless, both biochars bounded Zn strongly and the adsorption process was not easily reversed.

The coffee industry produces a wide range of organic wastes, some in large amounts, and most of them do not have a well-defined final disposal. The agricultural use of these wastes can be based on the recycling of nitrogen, but their chemical characterization and evaluation with soil under controlled conditions are mandatory. The aim of this work was to evaluate the use of coffee silverskin and expired coffee grounds as organic fertilizers. The wastes were chemically characterized according to CONAMA’S resolution No. 375 and passed through Brazil’s Agriculture Ministry regulation for organic fertilizers and soil conditioners. A greenhouse experiment with Rhodic Ferralsol soil and maize was performed to obtain the agronomic efficiency index (AEI) for nitrogen. The treatments were control (without residue), ammonium nitrate as a mineral reference, and both organic wastes, at a dose of 450 mg of Kjeldahl nitrogen per pot, in triplicate. The data obtained in the characterization were favorable to the wastes as nitrogen sources for agriculture. However, the AEIs obtained were low (0.5 and 7.9% for the expired coffee grounds and the coffee silverskin, respectively) compared to that of the mineral reference (92%). Based on these results, the use of coffee silverskin and expired grounds as organic fertilizers is not recommended but can improve soil attributes and serve as a complementary source of nitrogen and potash.

Biochar derived from coffee waste has been reported as a promising material for heavy metal sorption. However, if the intended use is environmental remediation, knowing the extent to which desorption may occur is critical. Thus, the objective of this work was to evaluate the efficiency of spent coffee ground (SCG) and coffee parchment (CP) biochars pyrolyzed at 700 °C under laboratory conditions, in the sorption of Cd and Pb from aqueous solutions, in a pH range from 2 to 10, and their retention after an induced desorption process with a 2.9 pH acetic acid solution. Both biochars were alkaline, and the initial pH of the solution had a large effect on the sorption capacity of SCG but a small effect on the sorption capacity of CP. The Pb sorption capacity was higher for CP (18.6 mg•g -1 ) than for SCG (11.4 mg•g -1 ), while both biochars had low Cd retention capacities (1.18 mg•g -1 ). Coffee parchment also showed the highest Pb retention (30% to 87%), while for Cd there was no difference between CP and SCG biochars. Our results showed that metal precipitation was the main mechanism for metal immobilization and CP biochar proved to be more reliable than SCG, mainly for Pb, due to its higher sorption capacity and lower metal release by desorption than SCG. These characteristics are particularly important for the use of biochar in environmental remediation.Besides that, the biochar production represents an eco-friendly destination for these feedstocks, contributing to the circular economy.

The agricultural use of biochar has been the focus of much research in the last decade due to the improvement of soil chemical, physical, and biological attributes. Nonetheless, Brazil still has no specific legislation for biochar, limiting its agricultural use.The objective of the present work is to evaluate the use of biochar produced from spent coffee grounds (SCG) and coffee parchment (CP) by slow pyrolysis at 700 °C according to the existing framework of the Brazilian Ministry of Agriculture, Livestock, and Food Supply (MAPA) legislation for organic fertilizer, soil conditioner or plant substrate. Biochar was characterized according to normative instructions No. 17, 31, 61, 7, 5 and 35. Although not required by the addressed legislation, the semitotal content of macro-and micronutrients was also determined. While CP biochar could be used as an organic fertilizer or plant substrate, SCG biochar, due to its higher Ni content and lower than required cation exchange capacity (CEC), did not meet MAPA legislation criteria to allow for its agricultural use. Future regulations can be based on the current standards, and structural attributes, such as total C content, particle size distribution, and complete macroand micronutrient determination should be included. Further research may also indicate the viability of biochar use as a soil conditioner based on a more representative set of biomasses with a higher CEC. These considerations will help to take advantage of the benefits of biochar to soil, contributing to a circular economy, which is still at a difficult stage in Brazil.

Coffee waste-derived biochar was found to immobilize heavy metals in contaminated soil, although there are few studies involving these materials. Given the large amount of waste generated in the coffee industry, this presents a relevant opportunity to contribute to the circular economy and environmental sustainability. Therefore, the objective of this study was to evaluate the effects of the application of biochars derived from coffee grounds and coffee parchment in the remediation of a Cd, Zn and Pb contaminated soil and at the development of jack beans (Canavalia ensiformis) in this area’s revegetation. The biochars were pyrolyzed at 700 °C, and the treatments were: contaminated soil (CT); contaminated soil + calcium carbonate (CaCO3); contaminated soil + 5% (weight (w)/weitght (w)) coffee ground biochar and contaminated soil + 5% (w/w) coffee parchment biochar. These treatments were incubated for 90 days, followed by the cultivation of jack beans for 60 days. Soil samples, soil solution and plants were analyzed for nutrients and heavy metals. The addition of coffee grounds and coffee parchment biochars significantly reduced the contents of heavy metals in the soil compared to the Control (32.13 and 42.95%, respectively, for Zn; 26.28 and 33.06%, respectively, for Cd and 28.63 and 29.67%, respectively, for Pb), all of which had a superior performance than the CaCO3 treatment. Thus, following the observed reduction in the soil soluble fraction of metals, its uptake by the plants was also reduced, especially limiting Cd and Pb accumulation in plant dry matter. In addition, coffee parchment biochar promoted a greater accumulation of nutrients in the shoots, i.e., for K and P (1450 and 21.5 mg pot−1, respectively, dry matter basis) compared to the control (54.4 and 9.3 mg pot−1, respectively). Therefore, coffee parchment biochar use in association with jack beans may represent a viable tool for the remediation of metal contamination concomitantly with revegetation of the contaminated area.

No abstract