Leaching and nitrous oxide (N₂O) emissions can represent substantial nitrogen (N) losses from chemical fertilizers, and slow-release fertilizers (SRFs) can mitigate these effects. Thus, biochar can be an alternative from an agronomic and environmental point of view to synthesize SRFs due to its physicochemical characteristics. We investigated the effect of nitrogenous organomineral fertilizers (OMF-N) formulated based on activated biochar on N losses by leaching and N₂O emissions. The OMF-N were developed from a dry mechanical pelleting process with different biochar and urea proportions (2:1; 1:2, and 1:4). Three experiments were conducted using four fertilizer sources (urea, OMF-N 2:1, OMF-N 1:2, and OMF-N 1:4): i. to analyze the kinetics of N release from OMF-N at times: 5, 15, 30, 60, 90, and 120 min; ii. for N₂O emission analysis determined at 3, 6, 10, 14, 24, 44, 54, 64, 74, 84, 104, and 118 days after application to the soil; and iii. for a double factorial design that was adopted to analyze N leaching, consisting of the combination of applying 160 kg N ha⁻¹ of fertilizers in PVC columns at different depths (20, 40, 60, and 80 cm) and analyzed at five times (1, 7, 14, 21, and 28 days). FTIR spectroscopic analysis, specific surface area, porosity, and surface morphology showed physicochemical interactions of N of the OMF with biochar; the N from the OMF interacts physically and chemically binds to the functional surfaces of biochar, delaying the dissolution flow. The OMF-N proved capable of retaining 48% to 60% more NH₄⁺ and reduced the release of N_total from urea from 27% to 60%, as well as reduced N₂O emissions from 47% to 66%. Although absolute CO₂ emissions intensified with the application of OMF-N, its use provides C sequestration in the soil to due to the recalcitrant C of the biochar, which results in a positive input-output balance in the system. The NO₃⁻ concentration profiles revealed that the OMF-N application was able to reduce leaching in the soil to a depth of 80 cm. These studies enabled better understanding of the processes involved in the biochar:urea interaction and revealed that biochar can be used as an organic matrix in the synthesis of SRF.

The objective of this work was to evaluate the development and quality of clonal seedlings of teak (Tectona grandis) grown in substrate with two types of biochar. The assay was carried out in a randomized complete block design, with ten treatments and four replicates: CS, commercial substrate, composed of pine bark and vermiculite at a ratio of 4:1; NS, nursery substrate composed of carbonized rice husk and coconut fiber at 1:1; and the remaining treatments were composed of the inclusions of biochar (BC) or activated biochar (BCA) in the CS, at the proportions of 25, 50, 75, and 100%. The development and quality parameters of seedlings were evaluated 90 days after striking the minicuttings in the substrates. BCA substrate additions at 25, 50, and 100% allowed for a development of height and stem diameter comparable to that of the NS. Biochar without the activation procedure does not improve quality parameters of seedlings, in comparison with the commercial substrate. The use of 25% activated biochar added to the commercial substrate is enough to improve seedling growth performance to the same level as that provided by the already validated NS.

Conduziu-se este estudo com o objetivo de avaliar a eficiência de fertilizantes organominerais fosfatados sobre o desenvolvimento inicial de mudas de eucalipto. O experimento foi realizado no viveiro de mudas da empresa Flora Sinop, em tubetes de 50 cm³. Foram avaliados três fertilizantes organominerais fosfatados, formulados a partir da mistura, em diferentes proporções, de superfosfato triplo, fosfato natural reativo de Bayovar, conteúdo ruminal de bovinos de corte, biochar e cama-de-aviário. Essas fontes foram aplicadas em mistura com o substrato comercial, em quatro níveis de P (1,4; 2,5; 3,6 e 4,7 mg dm-3) + tratamento referência. As parcelas foram compostas por 16 mudas do clone de eucalipto (Urograndis - I144). As mudas ficaram por 70 dias em desenvolvimento, após foi determinado: massa seca da parte aérea (MSPA), massa seca de raízes (MSR), teor de P na parte aérea e o índice de eficiência agronômica. O fertilizante organomineral composto por fosfato natural reativo de Bayovar + conteúdo ruminal apresentou eficiência similar ao tratamento referência.

The use of biochar technology in Brazil holds significant promise for advancing the principles of a circular economy, addressing pressing environmental challenges, and fostering sustainable development. Despite its great potential, biochar production and scale use remain strikingly limited in Brazil. Here, we explored the multifaceted potential of biochar in Brazil, focusing on its capacity to promote circularity, create novel inputs for agricultural and environmental purposes, and optimize infrastructure for the production and cycling of organic residues from diverse agricultural and energy production chains. Semi-structured interviews were conducted with stakeholders, and a workshop was organized with participants representing universities, public research institutes, private companies, and non-governmental organizations. We analyzed the current Brazilian scenario, identifying the main barriers preventing the widespread use of biochar in the country, as well as possible solutions in the economic, political, technological, R&D, and innovation sectors. Based on this assessment, our results show that stakeholders view the Brazilian biochar sector as emerging but constrained by regulatory uncertainty, market fragmentation, and logistical bottlenecks. They identified five priority levers for change: the creation of clear and credible regulatory frameworks, region-specific strategies for biomass use and on-farm deployment, integration of biochar into robust carbon market mechanisms, strengthening of targeted research and demonstration projects, and development of business models that combine agricultural benefits, carbon removal, and co-products.

This study investigated the effect of biochar addition (14% w/w) on the concentration of nutrient ions present in the leachate from a commercial green roof substrate after contact with rainwater. Biochar sample was produced from wood sawdust at 450 ˚C via slow pyrolysis. The sawdust biochar was characterized by physico-chemical and hydraluic prosperties and techniques including X-ray fluorescence, Fourier transform infrared spectroscopy, X-ray diffraction, Raman and differential thermal analysis. The physical and chemical properties of green roof substrate were also determined. The biochar effectively reduced the total amount of nitrate, sulfate, and phosphate in the leachates relative to the substrate alone but did not show a significant effect on ammonium leaching. The results indicated that wood sawdust-biochar has appropriate characteristics to be applied as a component of substrates, as it has a porous structure and adsorption capacity, as well as adequate physical-hydric properties. In addition, the management of biochar obtained from agricultural waste can contribute to the achievement of the Sustainable Development Goals when used in sustainable alternatives such as green roofing.

O setor agrícola tem gerado e lançado no ambiente toneladas de resíduos advindos tanto das práticas agrícolas como das práticas correlatas ao setor. Vista a necessidade de se obter soluções para formas de tratamento dos resíduos produzidos pelas atividades agrícolas, a utilização da compostagem dos resíduos é uma alternativa. Este trabalho teve como objetivo avaliar as características de compostos gerados pela compostagem de diferentes proporções de resíduos advindos das agroindústrias de processamento de frutas, de abate bovino e processamento de leite. Cinco diferentes concentrações foram testadas em forma de pilhas, sendo variada a concentração do resíduo do processamento de leite (gordura gerada no sistema de tratamento de resíduos do laticínio). Os resultados demonstraram que a utilização desses resíduos leva a uma decomposição eficiente, gerando um composto sem atratividade de vetores, cor escura e cheiro de terra molhada. O valor do pH ao final do processo mostrou-se adequado, com valores próximos de 9,0. A temperatura nas pilhas atingiu pelo menos 45 °C, indicando a sanitização dos compostos. Os valores de concentração de nitrogênio e fósforo foram baixos quando comparados à legislação. A relação carbono/nitrogênio apresentou valores ora dentro ora fora do estabelecido pela legislação. O composto apresenta potencial de utilização como fonte de matéria orgânica, entretanto, a utilização deve ser complementada com outras fontes de nutrientes como nitrogênio e fósforo. Palavras-chave: compostagem, resíduos orgânicos, adubação. CYCLING OF NUTRIENTS THROUGH TRANSFORMATION OF WASTE INTO ORGANIC FERTILIZER ABSTRACT The agricultural sector has generated and released tons of waste in the environment, whether arising from agricultural practices or other practices related to this sector. Given the need to obtain solutions for dealing with the waste produced by agricultural activities, the use of waste composting is an alternative. This work aimed to evaluate the characteristics of compounds generated by the composting of different proportions of waste arising from the agroindustries working with fruit processing, bovine slaughtering and milk processing. Five different concentrations were tested in the form of stacks, with varied concentrations of the waste of milk processing (fat generated in the waste treatment system of the dairy product). The results showed that the use of these waste materials leads to an efficient decomposition, thus generating a compound without attractiveness of vectors, dark colored, and with smell of wet earth. The pH value at the end of the process was adequate, with values close to 9.0. The temperature in the stacks reached at least 45 °C, thus indicating the sanitization of the compounds. The concentration values of nitrogen and phosphorus were low compared to the current legislation. The carbon/nitrogen ratio has presented values both within and beyond the legislation. The compound unveils potential use as a source of organic matter; however, the use should be enhanced with other nutrient sources, such as nitrogen and phosphorus. Keywords: composting, organic waste, manure. DOI: http://dx.doi.org/10.14583/2318-7670.v04n01a05