Ildo Luis Sauer

Digestate is a byproduct of the anaerobic digestion of food waste and can be used as a fertilizer in agricultural production. Combining mineral fertilizers with food waste digestate represents a promising strategy to improve soil fertility and enhance plant nutrition and growth. Therefore, this study evaluated the effects of different proportions of food waste anaerobic digestate combined with mineral fertilization on soil fertility, growth, and the nutritional status of maize (Zea mays L.) plants. The experiment was conducted under greenhouse conditions using a completely randomized design with six treatments: unfertilized control (C0), 100% mineral fertilizer (M100), 75% mineral fertilizer + 25% digestate (M75D25), 50% mineral fertilizer + 50% digestate (M50D50), 25% mineral fertilizer + 75% digestate (M25D75), and 100% digestate (D100), with four replicates. The chemical characterization of the digestate revealed concentrations of 0.70 g kg⁻¹ total N, 0.60 g kg⁻¹ P, 0.60 g kg⁻¹ K, and 1.30 g kg⁻¹ Na. The 100% mineral treatment (M100) supplied 120 kg ha⁻¹ urea, 80 kg ha⁻¹ triple superphosphate, and 70 kg ha⁻¹ potassium chloride, while digestate application rates were calculated based on total N supply, with mineral P and K adjusted proportionally. M25D75 significantly increased cation exchange capacity, base saturation, and soil pH and resulted in higher soil P and Mg concentrations; however, it also increased soil Na concentration and exchangeable sodium percentage (ESP). M25D75, M50D50, M75D25, and M100 promoted higher chlorophyll index, stem diameter, number of leaves, plant height, and shoot dry biomass, as well as higher P, K, Ca, and Mg concentrations in plant tissues. In contrast, the exclusive application of digestate (D100) increased electrical conductivity, exchangeable sodium percentage, and Na concentrations in both soil and plant tissues, resulting in reduced plant growth. Therefore, high doses of digestate may increase the risk of soil sodicity. Overall, the combined application of mineral fertilizers and food waste digestate improved soil fertility, plant nutrition, and maize growth. These findings support the recycling of food waste through its agricultural use as digestate, contributing to circular nutrient management while reducing dependence on synthetic mineral fertilizers.

The University of São Paulo (USP), through its Environmental Policy and under the coordination of the Superintendence of Environmental Management (SGA), has been promoting sustainability initiatives across its campuses. One of the most recent efforts is the USP Sustainability Program (USPSusten), which supports teaching, research, outreach, and shared management activities focused on socio-environmental sustainability, carried out by faculty and postdoctoral researchers. Highlighted projects include: (a) the Bioenergy and Biofertilizer Production Plant (BBPP), which uses organic waste from campus dining halls and green areas at the main campus (CUASO) to produce biogas and fertilizers; (b) a pilot plant for fueling hydrogen-powered buses, with a range of 240 km; (c) photovoltaic energy generation, with the potential to meet up to 27% of contracted electricity demand; and (d) greenhouse gas inventories, based on the GHG Protocol methodology. The BBPP, in operation since May 2021, processes organic waste to generate an average of 2,800 kWh/month, with an average output of 136 kWh per ton of waste. The hydrogen fuel project uses ethanol as a renewable energy source and aims to reduce CO₂eq emissions per capita by up to 72% compared to conventional combustion vehicles. Solar generation has shown economic feasibility for units consuming over 100 MWh/month. The emission inventory, structured through an action-research approach, involves pilot units within USP and highlights the need for improvements in the use of refrigerant gases in buildings and anesthetic gases in hospitals. These integrated efforts demonstrate the University’s commitment to conserving natural resources and enhancing quality of life.

The amount of municipal solid waste (MSW) produced has increased with population growth and consumption patterns. Currently, most waste goes to dumps, although the Brazilian law requires the final destination to be landfills. The latter does not consider the energy lost by these solutions and the carbon footprint that better destinations could avoid. However, not treating the waste correctly aggravates land availability problems, especially in large cities such as São Paulo. Anaerobic digestion is an alternative to traditional waste management, and in addition to treating residues, it generates energy and recovers the nutrients present in MSW. Thermodynamic analyses are still scarce in the literature despite being a known process. This study performed an exergy analysis of an existing biogas plant at the Institute of Energy and Environment of the University of São Paulo with a processing capacity of 20 tons of MSW per day composed of three reactors (430 m³ each) and one internal combustion engine (ICE) of 75 kW. The plant uses MSW as the substrate for anaerobic digestion and generates electrical energy, biogas, and fertilizer for agriculture (digestate). Additionally, the plant operates in cogeneration, as the anaerobic digestion reactor uses the heat produced to generate electrical energy. The results showed that the exergy present in the substrate is 67,320 MJ/day. The products’ exergy flows and the processes’ efficiencies show that the exergy flow of the biogas (44,488 MJ/day) is significantly higher than the exergy flow of the digestate (1455 MJ/day). When considering the cogeneration process, the exergy flow was similar for heat and electric energy as the final products, with 10,987 MJ/day for electric energy and 5215 MJ/day for electric energy. The exergy efficiency of the digestion process was 68.25%, while that of cogeneration (digestate, heat and electric energy) was 26.23%. These results can help identify inefficiencies and optimize processes in an anaerobic digestion plant. Furthermore, thermodynamic analyses of anaerobic digestion found in the literature are mostly based on theoretical models. Thus, this study fills a gap regarding exergy analysis of actual biogas plants.

O setor energético impacta significativamente o meio ambiente e aproximadamente 70% do uso final de energia elétrica no setor industrial estão em motores elétricos. Na indústria brasileira o consumo de eletricidade em motores representa 68%. A indústria 4.0 (I4.0) tem relação direta com a eletrônica e recursos computacionais. Este trabalho discute, no contexto da transição energética, as políticas e os padrões mínimos conhecidos como Minimum Energy Performance Standard (MEPS) e as etiquetas - uma das principais formas de apoiar a eficiência energética diretamente no nível do produto, fazendo-se uma análise da linha do tempo dos padrões globais de desempenho de eficiência mínima para motores elétricos. Avalia-se a norma IEC (International Electrotechnical Commission) que define classes de eficiência IE1 a IE4. Estas classes são denominadas por Standard, High Efficiency, Premium Efficiency e Super-Premium Efficiency, conforme a National Electrical Manufacturers Association. A nova classe IE5 Ultra-Premium Efficiency ainda não foi definida em detalhes, mas está prevista para produtos potenciais em uma edição futura da norma. São examinadas as principais tecnologias que podem ser aplicadas aos sistemas motrizes no âmbito da I4.0 como os variadores eletrônicos de velocidade (VEV), os Motores Síncronos de Imã Permanente (MSIP) e os Motores Síncronos de Relutância (MSREL) que permitem aos motores excederem os limites de eficiência IE4 e IE5. Conclui-se que estas duas tecnologias de motores tendem a ser fundamentais para o aumento da eficiência e para a redução das emissões de gases de efeito estufa, reduzindo o impacto de sistemas motrizes, em direção à transição energética e para uma matriz de baixo carbono.

Residual rights are the right to choose asset uses not specified in the contract. They are essential in situations of uncertainty. The current energy transition presents a greater variety of assets. Moreover, it is impossible to anticipate all relevant states that the assets and the environment can embody, making it impossible to optimize them contractually. Furthermore, there is consensus that the transition must occur quickly, which means high levels of investment in new specific assets. How should we distribute property rights to maximize social benefits in a context with specific and dispersed assets? Because of the complementarity between network and distributed resources, this article questions the premise that deverticalization is invariably beneficial to consumers and argues for the need to revise the concept of network and develop the regulatory implications of such a reconceptualization. We defend the need to evaluate alternative network concepts considering the technological repertoire available to operationalize them. When considering the technological repertoire available today, characterized by the competitiveness of information and communications technology (ICT) and distributed resources, we should recognize the inherently incomplete nature of the contracts signed between network operators and users.

Desenvolvimento e Meio Ambiente addresses socioenvironmental issues

The rapid expansion of distributed generation leads to the integration of an increasing number of energy generation sources. However, integrating these sources into electrical distribution networks presents specific challenges to ensure that the distribution networks can effectively accommodate the associated distributed energy and power. Thus, it is crucial to evaluate the electrical effects of power along the conductors, components, and loads. Power-flow analysis is a well-established numerical methodology for assessing parameters and quantities within power systems during steady-state operation. The University of São Paulo’s Cidade Universitária “Armando de Salles Oliveira” (CUASO) campus in São Paulo, Brazil, features an underground power distribution system. The Institute of Energy and Environment (IEE) leads the integration of several distributed generation (DG) sources, including a biogas plant, photovoltaic installations, and a small wind turbine, into one of the CUASO’s feeders, referred to as “USP-105”. Load-flow simulations were conducted using the PowerWorld^TM Simulator v.23, considering the interconnection of these sources. This dataset provides comprehensive information and computational files utilized in the simulations. It serves as a valuable resource for reanalysis, didactic purposes, and the dissemination of technical insights related to DG implementation.

Utilities, policymakers, regulators, free market, and prosumers share a common interest in understanding whether benefits associated with such increased of DERs outweigh costs. To dimension and qualify B/C relationship, there are intrinsic variables relative to DERs' technical-economic arrangement and standard mechanisms used for its compensation: NEM, feed-in policies, etc. Other side, DERs must be adjusted on established regulatory framework, tariff schemes and utility revenue models. In this article, these three ambits are analyzed including a Brazilian southeastern region user's case study connected to MV network with DG measured data. Thus, some guidelines are pointed for the comprehensive implementation of DERs from the perspective of those involved.

Distributed generation, which is mainly deployed with PV systems that benefit economically prosumers, has soared in use in Brazil. Despite this, PV capacity in excess may cause technical issues which concern planning engineers who have adopted rules of thumb to screen interconnection requests without any detailed study. Recently, the hosting capacity concept has been employed to assess how much PV capacity a distribution grid can host without deteriorating grid parameters, reliability, or power quality. A steady-state and worst-case-based scenario was used to run deterministic power flow simulations to estimate the hosting capacity of a specific radial circuit at a campus of the University of São Paulo, referred to as “USP-105”. Although the result may be not completely accurate, it was found that USP-105 can accommodate 103% of its peak load or 4970.6 kW of PV power, which reduced the circuit’s annual peak load by 9%. Another finding was that hosting capacity increased when PV-DG deployment was dispersed along the circuit rather than concentrated on a single location (e.g., closest, or furthest to the substation). Utilities may therefore benefit from a simple and quick assessment to obtain an overview of how specific circuits behave on PV deployment and indicate which locations are technically more beneficial.