• Authors:
    • Seabra, J. E. A.
    • Gurgel, A. C.
    • Moreira, M.
  • Source: ENVIRONMENTAL SCIENCE & TECHNOLOGY
  • Volume: 48
  • Issue: 24
  • Year: 2014
  • Summary: This study evaluated the life cycle GHG emissions of a renewable jet fuel produced from sugar cane in Brazil under a consequential approach. The analysis included the direct and indirect emissions associated with sugar cane production and fuel processing, distribution, and use for a projected 2020 scenario. The CA-GREET model was used as the basic analytical tool, while Land Use Change (LUC) emissions were estimated employing the GTAP-BIO-ADV and AEZ-EF models. Feedstock production and LUC impacts were evaluated as the main sources of emissions, respectively estimated as 14.6 and 12 g CO2eq/MJ of biofuel in the base case. However, the renewable jet fuel would strongly benefit from bagasse and trash-based cogeneration, which would enable a net life cycle emission of 8.5 g CO2eq/MJ of biofuel in the base case, whereas Monte Carlo results indicate 21 ± 11 g CO2eq/MJ. Besides the major influence of the electricity surplus, the sensitivity analysis showed that the cropland-pasture yield elasticity and the choice of the land use factor employed to sugar cane are relevant parameters for the biofuel life cycle performance. Uncertainties about these estimations exist, especially because the study relies on projected performances, and further studies about LUC are also needed to improve the knowledge about their contribution to the renewable jet fuel life cycle.
  • Authors:
    • Cederberg, C.
    • Henders, S.
    • Persson, U. M.
  • Source: GLOBAL CHANGE BIOLOGY
  • Volume: 20
  • Issue: 11
  • Year: 2014
  • Summary: The world's agricultural system has come under increasing scrutiny recently as an important driver of global climate change, creating a demand for indicators that estimate the climatic impacts of agricultural commodities. Such carbon footprints, however, have in most cases excluded emissions from land-use change and the proposed methodologies for including this significant emissions source suffer from different shortcomings. Here, we propose a new methodology for calculating land-use change carbon footprints for agricultural commodities and illustrate this methodology by applying it to three of the most prominent agricultural commodities driving tropical deforestation: Brazilian beef and soybeans, and Indonesian palm oil. We estimate land-use change carbon footprints in 2010 to be 66 tCO(2)/t meat (carcass weight) for Brazilian beef, 0.89 tCO(2)/t for Brazilian soybeans, and 7.5tCO(2)/t for Indonesian palm oil, using a 10year amortization period. The main advantage of the proposed methodology is its flexibility: it can be applied in a tiered approach, using detailed data where it is available while still allowing for estimation of footprints for a broad set of countries and agricultural commodities; it can be applied at different scales, estimating both national and subnational footprints; it can be adopted to account both for direct (proximate) and indirect drivers of land-use change. It is argued that with an increasing commercialization and globalization of the drivers of land-use change, the proposed carbon footprint methodology could help leverage the power needed to alter environmentally destructive land-use practices within the global agricultural system by providing a tool for assessing the environmental impacts of production, thereby informing consumers about the impacts of consumption and incentivizing producers to become more environmentally responsible.
  • Authors:
    • Cerri, C. E. P.
    • Deon, M. D.
    • Paladini, A. A.
    • Zani, C. F.
    • Signor, D.
  • Source: REVISTA BRASILEIRA DE CIENCIA DO SOLO
  • Volume: 38
  • Issue: 5
  • Year: 2014
  • Summary: Sugarcane is the main crop used in ethanol biofuel production in Brazil and it may be harvested with or without burning, increasing or decreasing greenhouse gases emissions and soil carbon deposition. In this study, we evaluated the effect of the sugarcane harvest system (with and without burning, at one, three, and six years after the last replanting) on C contents and C stocks in the soil, the physical quality of soil organic matter, and C immobilization in soil microbial biomass. The areas harvested without burning showed higher C content in the surface layer and higher C stocks, regardless of the time after the last replanting. Differences in the physical quality of organic matter mainly occurred in the 53 to 75 µm particle size fraction, in which the C ratio was higher in the unburned areas. In the 0-10 cm layer, harvesting without burning was associated with higher microbial C. Harvest without straw burning is effective in accumulating C in forms with long residence time in the soil.
  • Authors:
    • Ajanovic, A.
    • Haas, R.
  • Source: APPLIED ENERGY
  • Volume: 135
  • Year: 2014
  • Summary: In the early 2000s high expectations existed regarding the potential contribution of biofuels to the reduction of greenhouse gas emissions and substitution of fossil fuels in transport. In recent years sobering judgments prevailed. The major barriers for a further expansion of biofuels are their high costs (compared to fossil fuels), moderate ecological performances, limited feedstocks for biofuel production and their competition with food production. The objective of this paper is to investigate the market prospects of biofuels up to the year 2030. It focuses on the three currently most important regions for biofuels production and use: the US, EU and Brazil which in 2010 accounted together for almost three-quarters of global biofuel supply. Our method of approach is based on a dynamic economic framework considering the major cost components of biofuels and corresponding technological learning with respect to capital costs. Moreover, for the analysis of the competitiveness of biofuels with fossil fuels also taxes are considered. The most important result is that under existing tax policies biofuels are cost-effective today and also for the next decades in the regions investigated. However, their potentials are restricted especially due to limited crops areas, and their environmental performance is currently rather modest. The major final conclusions are: (i) To reveal the real future market value of biofuels, a CO 2 based tax system should be implemented for all types of fuels providing a neutral environmental incentive for competition between all types of fossil and renewable fuels; (ii) Moreover, the research and development for all types of biofuels, but especially for second generation biofuels, has to be intensified.
  • Authors:
    • Gisladottir, G.
    • Zinn, Y. L.
    • Mayes, M. A.
    • Jagadamma, S.
    • Russell, A. E.
  • Source: Article
  • Volume: 213
  • Year: 2014
  • Summary: Dissolved organic carbon (DOC) transported from the soil surface is stabilized in deeper soil profiles by physicochemical sorption processes. However, it is unclear how different forms of organic carbon (OC) compounds common in soil organic matter interact with soil minerals in the surface (A) and subsurface (B) horizons. We added four compounds (glucose, starch, cinnamic acid and stearic acid) to the silt- and clay-sized fraction (fine fraction) of A and B horizons of eight soils from varying climates (3 temperate, 3 tropical, 1 arctic and 1 sub-arctic). Equilibrium batch experiments were conducted using 0 to 100 mg C L-1 of C-14-labeled compounds for 8 h. Sorption parameters (maximum sorption capacity, Q(max) and binding coefficient, k) calculated by fitting sorption data to the Langmuir equation showed that Q(max) of A and B horizons was very similar for all compounds. Both Q(max) and k values were related to sorbate properties, with Q(max) being lowest for glucose (20-500 mg kg(-1)), highest for stearic acid (20,000-200,000 mg kg(-1)), and intermediate for both cinnamic acid (200-4000 mg kg(-1)) and starch (400-6000 mg kg(-1)). Simple linear regression analysis revealed that physicochemical properties of the sorbents influenced the Q(max), of cinnamic acid and stearic acid, but not glucose and starch. The sorbent properties did not show predictive ability for binding coefficient k. By using the fine fraction as sorbent, we found that the mineral fractions of A horizons are equally reactive as the B horizons irrespective of soil organic carbon content. (C) 2013 Elsevier B.V. All rights reserved.
  • Authors:
    • De Oliveira Ferreira, A.
    • Briedis, C.
    • Machado Sá, M. F.
    • Tivet, F.
    • De Moraes, A.
    • Lal, R.
    • Dos Santos, J. B.
    • De Moraes Sá, J. C.
    • Eurich, G.
    • Farias, A.
    • Friedrich, T.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 6
  • Year: 2013
  • Summary: Inventories of C and N footprints on a landscape scale are essential tools for estimating C offsets from agricultural emissions. Therefore, the aims of this study conducted in the subtropical humid ecosystem in southern Brazil were to: (i) conduct a soil-specific inventory of landscape soil C and N stocks with reference to soil order, soil texture, and land use/management type; (ii) estimate accretion rates for soil organic C (SOC) and total N (TN) for areas managed under no-till (NT) practices management with reference to native vegetation (NV) based on this inventory; (iii) generate a map of C stocks for each land use system; and (iv) calculate estimated C offset for the region through the use of NT compared to conventional tillage (CT). Soil samples were collected at 324 points to a 1-m depth from the entire region. Soil texture and duration of NT had a strong influence on C and N stocks. The average soil C stock across all types of soils for depths of 0-40 and 40-100 cm was 57.0 and 43.0%, respectively. The extrapolation of C stored in the 0- to 40-cm depth based on the NT management for 11 and 20 yr for 1.52 million hectare (Mha) was 9.08 ± 0.62 Tg (1 Tg = 1012 g) representing 11.9% of the C stored in all soil orders. The long-term of C sink capacity by conversion of arable land from CT to NT in this region is 33.2 Tg of CO2, with the C offset of 22.5% of all anthropogenic emissions.
  • Authors:
    • Halvorson, A. D.
    • Jantalia, C. P.
    • Follett, R. F.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 3
  • Year: 2013
  • Summary: Conventional tillage (CT) with high N rates and irrigation is used more frequently than no-till (NT) for growing continuous corn (Zea mays L.) in the central Great Plains of the United States. The objective of this study was to evaluate soil organic C (SOC) stocks throughout the soil profile as well as the potential for maintaining or sequestering SOC within the soil profile (0- 120 cm) under irrigated, continuous corn as affected by NT and CT and three N rates. Isotopic δ13C techniques provided information about the fate of C added to soil by corn (C4-C) and of residual C3-C from cool-season plants grown before this study. Relative contributions of C4-C and C3-C to SOC stocks after 8 yr were determined. Retention of C4-C from corn was measured under NT and CT. Nitrogen fertilization slowed losses of C3-C and improved retention of C 4-C. No-till was superior to CT in maintaining SOC. Deep soil sampling to 120 cm and the use of stable C isotope techniques allowed evaluation of changes in SOC stocks during the 8-yr period. Change in SOC under NT vs. CT resulted from greater loss of C3-C stocks under CT throughout the soil profile. Irrigated corn has a low potential to sequester SOC in the central Great Plains, especially under CT. The results of this study indicate that stability of the soil organic matter and its perceived "recalcitrance" is altered by environmental and biological controls. © Soil Science Society of America.
  • Authors:
    • Reis, F. B. D.
    • Chaer, G. M.
    • De Sousa, D. M. G.
    • Lopes, A. A. D. C.
    • Goedert, W. J.
    • Mendes, I. D.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 2
  • Year: 2013
  • Summary: An interpretative framework for microbial biomass C (MBC), basal respiration, and the activity of soil enzymes cellulase, β-glucosidase, arylsulfatase, and acid phosphatase was developed for the clayey Oxisols of the Brazilian Cerrado. Soil samples (0-10-cm depth) were collected from 24 treatments from three long-term experiments and analyzed to determine their microbial attributes and soil organic C (SOC). These treatments presented a large range of Mehlich-extractable P and cumulative corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] yields. The critical levels for the microbial indicators were defined based on criteria similar to those used in soil nutrient calibration tests. The microbial indicators were interpreted as a function of the relative cumulative yields (RCYs) of corn and soybean and the SOC using linear regression models. Adequacy classes for each microbial indicator as a function of the RCY and SOC were established based on the following criteria: ≤40%: low; 41 to 80%: moderate; and >80%: adequate. The critical levels equivalent to 80% of the RCY for MBC, basal respiration, cellulase, β-glucosidase, acid phosphatase, and arylsulfatase were: 375 mg C kg -1, 90 mg CO2-C kg-1, 105 mg glucose kg -1 d-1, 115 mg p-nitrophenol kg-1 h -1, 1160 mg p-nitrophenol kg-1 h-1, and 90 mg p-nitrophenol kg-1 h-1, respectively. Similar critical levels were obtained when SOC was used as the interpretation criterion. The interpretation tables provided in this study establish, for the first time, reference values for the soil microbial indicators based on crop yields and constitute a first approximation. Their applicability to other conditions must be evaluated.
  • Authors:
    • Smith, P.
    • Williams, M.
    • Forristal, D.
    • Lanigan, G.
    • Osborne, B.
    • Abdalla, M.
    • Jones, M. B.
  • Source: Soil Use and Management
  • Volume: 29
  • Issue: 2
  • Year: 2013
  • Summary: Conservation tillage (CT) is an umbrella term encompassing many types of tillage and residue management systems that aim to achieve sustainable and profitable agriculture. Through a global review of CT research, the objective of this paper was to investigate the impacts of CT on greenhouse gas (GHG) emissions. Based on the analysis presented, CT should be developed within the context of specific climates and soils. A number of potential disadvantages in adopting CT practices were identified, relating mainly to enhanced nitrous oxide emissions, together with a number of advantages that would justify its wider adoption. Almost all studies examined showed that the adoption of CT practices reduced carbon dioxide emissions, while also contributing to increases in soil organic carbon and improvements in soil structure.
  • Authors:
    • Adami, M.
    • Aguiar, D. A.
    • de Figueiredo, E. B.
    • Bordonal, R. de O.
    • Rudorff, B. F. T.
    • La Scala, N.
  • Source: Biomass and Bioenergy
  • Volume: 59
  • Year: 2013
  • Summary: Brazil is a major sugarcane producer and Sao Paulo State cultivates 5.5 million hectares, close to 50% of Brazil's sugarcane area. The rapid increase in production has brought into question the sustainability of biofuels, especially considering the greenhouse gas (GHG) emissions associated to the agricultural sector. Despite the significant progress towards the green harvest practices, 1.67 million hectares were still burned in Sao Paulo State during the 2011 harvest season. Here an emissions inventory for the life cycle of sugarcane agricultural production is estimated using IPCC methodologies, according to the agriculture survey data and remote sensing database. Our hypothesis is that 1.67 million hectares shall be converted from burned to green harvest scenarios up to years 2021 (rate 1), 2014 (rate 2) or 2029 (rate 3). Those conversions would represent a significant GHG mitigation, ranging from 50.5 to 70.9 megatons of carbon dioxide equivalent (Mt CO(2)eq) up to 2050, depending on the conversion rate and the green harvest systems adopted: conventional (scenario 51) or conservationist management (scenario S2). We show that a green harvest scenario where crop rotation and reduced soil tillage are practiced has a higher mitigation potential (70.9 Mt CO(2)eq), which is already practiced in some of the sugarcane areas. Here we support the decision to not just stop burning prior to harvest, but also to consider other better practices in sugarcane areas to have a more sustainable sugarcane based ethanol production in the most dense cultivated sugarcane region in Brazil. (C) 2013 Elsevier Ltd. All rights reserved.