Marcelo Valadares Galdos

Atributos químicos e produção de milho em um latossolo vermelho eutroférrico tratado com lodo de esgoto

A utilizacao de lodo de esgoto como fertilizante orgânico ou condicionador do solo, tem-se tornado cada vez mais atraente, pelos altos custos e impactos ambientais relacionados com os demais metodos de disposicao, pela presenca de nutrientes vegetais e materia orgânica no lodo e pela necessidade de reducao de custos na agricultura. No entanto, em sua composicao, pode conter metais pesados, microrganismos patogenicos e compostos orgânicos toxicos. Visando estudar os efeitos da aplicacao de lodo de esgoto em areas agricolas, foi realizado um experimento, com duracao de dois anos agricolas, para determinar alteracoes em propriedades quimicas do solo, principalmente sobre os teores de P, Cu, Ni e Zn em um Latossolo Vermelho eutroferrico, de textura argilosa, cultivado com milho. O experimento consistiu na aplicacao de lodo de esgoto em duas doses comparadas a uma testemunha com adubacao quimica. Para analise de rotina das propriedades quimicas e do teor de Ni do solo, foram coletadas amostras nas profundidades de 0-0,05; 0,05-0,10 e 0,10-0,20 m apos a colheita do milho no primeiro e no segundo ano. Foi feita, tambem, uma extracao sequencial de P em amostras da camada de 0-0,05 m, na seguinte ordem: CaCl2 (P biologicamente mais disponivel); NaHCO3 (P disponivel); NaOH (P ligado aos oxidos de Fe e Al); HCl (P ligado a Ca) e digestao nitrico-perclorica (P residual). A producao do milho foi maior nos tratamentos com aplicacao do lodo. Os teores disponiveis de P no solo onde foi aplicado lodo foram semelhantes aos do tratamento sem lodo e com adubo quimico. Entretanto, a aplicacao do lodo aumentou as fracoes labeis e moderadamente labeis do P na camada superficial. Os dados indicaram, por outro lado, aumento dos teores de Cu, Ni e Zn no solo e de Zn na planta. Dessa forma, faz-se necessario constante monitoramento do solo onde o lodo de esgoto e aplicado para o controle adequado dos teores de metais.

Net greenhouse gas fluxes in Brazilian ethanol production systems

Biofuels are both a promising solution to global warming mitigation and a potential contributor to the problem. Several life cycle assessments of bioethanol have been conducted to address these questions. We performed a synthesis of the available data on Brazilian ethanol production focusing on greenhouse gas (GHG) emissions and carbon (C) sinks in the agricultural and industrial phases. Emissions of carbon dioxide (CO2) from fossil fuels, methane (CH4) and nitrous oxide (N2O) from sources commonly included in C footprints, such as fossil fuel usage, biomass burning, nitrogen fertilizer application, liming and litter decomposition were accounted for. In addition, black carbon (BC) emissions from burning biomass and soil C sequestration were included in the balance. Most of the annual emissions per hectare are in the agricultural phase, both in the burned system (2209 out of a total of 2398 kg Ceq), and in the unburned system (559 out of 748 kg Ceq). Although nitrogen fertilizer emissions are large, 111 kg Ceq ha−1 yr−1, the largest single source of emissions is biomass burning in the manual harvest system, with a large amount of both GHG (196 kg Ceq ha−1 yr−1). and BC (1536 kg Ceq ha−1 yr−1). Besides avoiding emissions from biomass burning, harvesting sugarcane mechanically without burning tends to increase soil C stocks, providing a C sink of 1500 kg C ha−1 yr−1 in the 30 cm layer. The data show a C output: input ratio of 1.4 for ethanol produced under the conventionally burned and manual harvest compared with 6.5 for the mechanized harvest without burning, signifying the importance of conservation agricultural systems in bioethanol feedstock production.

Quantification of tropical soil attributes from ETM+/LANDSAT-7 data

The characterization of physical and chemical soils attributes is a pressing necessity for the agricultural land management optimization in many countries. Currently, soil analyses are performed by chemical treatments in a laboratory, generating environmental and time‐consuming problems. Remote sensing techniques can be faster and cheaper than conventional methods, do not generate chemical residues and are non‐destructive to the samples. The objective of the present work was to determine a remote sensing technique to estimate soil physical and chemical attributes in the regions of Paraguaçu Paulista and Rio Brilhante, in the States of São Paulo and Mato Grosso do Sul, respectively, Brazil, using reflectance data obtained by a sensor located in orbit. Fieldwork was performed to validate orbital data. A total of 110 soil samples were collected representing 43,000 h for the development of spectral models. Landsat‐7 ETM+images were atmospherically corrected and transformed to reflectance. The soil samples observed in the field were located by GPS and evaluated in the orbital image. The method used consists in a detailed investigation of the spectral data, in which the spectral curve, the position of the data in a graphic dispersion, the colour compositions and the pixel cursor values are evaluated. Spectral models were determined to quantify soil attributes. Soil samples from a different area had their attribute contents determined by the models. The attributes studied were sand, silt, clay, pH (CaCl2), organic matter, phosphorus, potassium, calcium, magnesium, aluminium, hydrogen, cation exchange capacity (CEC), sum of cations (SC) base saturation (BS) and aluminium saturation (AS). The results showed weak correlations with some soil attributes, such as SC, K, Ca, Mg, Al and P. High correlations (reaching 0.86) were obtained with sand, clay, silt, OM, CEC and H. On the other hand, validation procedure indicated that the best attributes for quantification were clearly clay (0.61) and sand (0.5). Therefore, there is strong evidence that these attributes can be predicted in similar landscapes, using the multiple‐linear equations developed in this study. This knowledge can be useful in many ways in agriculture, such as soil mapping, determining soil attributes, determining soil information in difficult access regions, and diminishing traditional soil analyses with environmental protection.

Technical and economic assessment of trash recovery in the sugarcane bioenergy production system

Mechanized sugarcane (Saccharum spp.) harvest without burning has been increasingly adopted in Brazil, increasing trash availability on the field. This study aims at showing the importance of using an integrated framework tool to assess technical and economic impacts of integral harvesting and baling trash recovery strategies and different recovery rates as well as its implications in the sugarcane production, transport and processing stages. Trash recovery using baling system presents higher costs per unit of mass of recovered trash in comparison to system in which trash is harvested and transported with sugarcane stalks (integral harvesting system). However, the integrated agricultural and industrial assessment showed that recovering trash using baling system presents better economic results (higher internal rate of return and lower ethanol production cost) than the integral harvesting system for trash recovery rates higher than 30 %. Varying trash recovery fraction, stalks productivity and mean transport distance for both integral harvesting and baling systems, sensitivity analyses showed that higher trash recovery fractions associated with higher stalks yields and long transport distances favors baling system, mainly due to the reduction of bulk load density for integral harvesting system under those conditions.

Direct N2O emission factors for synthetic N‐fertilizer and organic residues applied on sugarcane for bioethanol production in Central‐Southern Brazil

The production and use of biofuels have increased rapidly in recent decades. Bioethanol derived from sugarcane has become a promising alternative to fossil fuel for use in automotive vehicles. The ‘savings’ calculated from the carbon footprint of this energy source still generates many questions related to nitrous oxide (N2O) emissions from sugarcane cultivation. We quantified N2O emissions from soil covered with different amounts of sugarcane straw and determined the direct N2O emission factors of nitrogen fertilizers (applied at the planting furrows and in the topdressing) and the by‐products of sugarcane processing (filter cake and vinasse) applied to sugarcane fields. The results showed that the presence of different amounts of sugarcane straw did not change N2O emissions relative to bare soil (control). N‐fertilizer increased N2O emissions from the soil, especially when urea was used, both at the planting furrow (plant cane) and during the regrowth process (ratoon cane) in relation to ammonium nitrate. The emission factor for N‐fertilizer was 0.46 ± 0.33%. The field application of filter cake and vinasse favored N2O emissions from the soil, the emission factor for vinasse was 0.65 ± 0.29%, while filter cake had a lower emission factor of 0.13 ± 0.04%. The experimentally obtained N2O emission factors associated with sugarcane cultivation, specific to the major sugarcane production region of the Brazil, were lower than those considered by the IPCC. Thus, the results of this study should contribute to bioethanol carbon footprint calculations.

Sewage sludge application on cultivated soils: effects on runoff and trace metal load

The use of sewage sludge in agricultural soils as a macro and micronutrient source and as a soil conditioner has been one of the alternatives for its disposal. However, sewage sludge contains trace metals, which are potential sources of pollution. The goal of this study was to evaluate the effect of sewage sludge application on surface water contamination through runoff when it was applied in a soil cultivated with corn. The effect of sludge application on the concentration and load of copper, nickel and zinc and the volume of runoff water and sediment were evaluated. The experiment was set up in plots used to study erosion losses in Campinas, Sao Paulo State, Brazil. The soil is a clayey Rhodic Hapludox. Three treatments were studied: no sewage sludge, sewage sludge to supply the N required by the crop and twice that amount, with four replications. The water and sediment lost by runoff were measured after each rainfall, and sampled for chemical analysis. The volumes of water and sediment lost by runoff decreased after sewage sludge application. The waste application increased trace metal concentration in the runoff water and sediment, especially zinc, which was present in high concentration in the sewage sludge used. Nevertheless, the load of trace metals transported from the plot was mostly dependent on the total runoff volume. Most of the Cu, Zn and Ni losses were via sediment, and occurred in a few highly erosive rainfall events in the period studied.

Quantifying soil carbon stocks and greenhouse gas fluxes in the sugarcane agrosystem: point of view

Strategies to mitigate climate change through the use of biofuels (such as ethanol) are associated not only to the increase in the amount of C stored in soils but also to the reduction of GHG emissions to the atmosphere.This report mainly aimed to propose appropriate methodologies for the determinations of soil organic carbon stocks and greenhouse gas fluxes in agricultural phase of the sugarcane production. Therefore, the text is a piece of contribution that may help to obtain data not only on soil carbon stocks but also on greenhouse gas emissions in order to provide an accurate life cycle assessment for the ethanol. Given that the greenhouse gas value is the primary measure of biofuel product quality, biorefiners that can show a higher offset of their product will have an advantage in the market place.

Biogeochemical research priorities for sustainable biofuel and bioenergy feedstock production in the Americas

Rapid expansion in biomass production for biofuels and bioenergy in the Americas is increasing demand on the ecosystem resources required to sustain soil and site productivity. We review the current state of knowledge and highlight gaps in research on biogeochemical processes and ecosystem sustainability related to biomass production. Biomass production systems incrementally remove greater quantities of organic matter, which in turn affects soil organic matter and associated carbon and nutrient storage (and hence long-term soil productivity) and off-site impacts. While these consequences have been extensively studied for some crops and sites, the ongoing and impending impacts of biomass removal require management strategies for ensuring that soil properties and functions are sustained for all combinations of crops, soils, sites, climates, and management systems, and that impacts of biomass management (including off-site impacts) are environmentally acceptable. In a changing global environment, knowledge of cumulative impacts will also become increasingly important. Long-term experiments are essential for key crops, soils, and management systems because short-term results do not necessarily reflect long-term impacts, although improved modeling capability may help to predict these impacts. Identification and validation of soil sustainability indicators for both site prescriptions and spatial applications would better inform commercial and policy decisions. In an increasingly inter-related but constrained global context, researchers should engage across inter-disciplinary, inter-agency, and international lines to better ensure the long-term soil productivity across a range of scales, from site to landscape.

Environmental Sustainability Aspects of Second Generation Ethanol Production from Sugarcane

Sugarcane-derived ethanol from Brazil has a high output to input energy ratio and high greenhouse gas savings compared to fossil fuels. Current ethanol production is based on first generation (1G) technology, which ferments the sugars extracted from sugarcane stalks. Cellulosic ethanol (2G) can be produced from what is currently considered agricultural and agro-industrial residues (straw and bagasse), and also from dedicated high biomass-producing crops. 2G ethanol provides an opportunity to intensify production, obtaining more energy per unit of area cropped and potentially reducing the environmental footprint. Straw removal from the field has more negative than positive consequences for the environment and the production system, but the effects need to be evaluated at the site and regional levels. The use of bagasse as feedstock should be evaluated using life cycle assessment methods to account for its alternative uses as raw material and in cogeneration. Energy cane, a vigorous and rustic crop selected for total biomass production rather than for sucrose, is a promising feedstock for 2G ethanol. The presence of rhizomes, a deep root system, and intensive tillering contribute to erosion control, crop longevity, and soil carbon sequestration. There is a need for more long-term experiments focusing on soil quality, nutrient cycling, greenhouse gas emissions, and crop production using innovative techniques such as stable isotope labeling and intensive soil flux measurements with automatic chambers to understand the impact of removing crop residues for bioenergy production and of using high-biomass dedicated crops. Process-based models are useful in sustainability assessments of 2G sugarcane ethanol production since they take into account site and regional variability in soil biogeochemistry, climate parameters, management practices, plant genetic traits, and the interactions of these factors. The integration of models and geographic information systems allows for regional assessments of the potential impacts of bioenergy production, contributing to the identification and promotion of sustainable pathways for cellulosic ethanol production.