• Authors:
    • Jones, R.
    • Hatfield, J. L.
    • Chan, A. S. K.
    • Parkin, T. B.
    • Jarecki, M. K.
  • Source: Journal of Environmental Quality
  • Volume: 37
  • Issue: 4
  • Year: 2008
  • Summary: The interactive effects of soil texture and type of N fertility (i.e., manure vs. commercial N fertilizer) on N2O and CH4 emissions have not been well established. This study was conducted to assess the impact of soil type and N fertility on greenhouse gas fluxes (N2O, CH4, and CO2) from the soil surface. The soils used were a sandy loam (789 g kg-1 sand and 138 g kg-1 clay) and a clay soil (216 g kg-1 sand, and 415 g kg-1 clay). Chamber experiments were conducted using plastic buckets as the experimental units. The treatments applied to each soil type were: (i) control (no added N), (ii) urea-ammonium nitrate (UAN), and (iii) liquid swine manure slurry. Greenhouse gas fluxes were measured over 8 weeks. Within the UAN and swine manure treatments both N2O and CH4 emissions were greater in the sandy loam than in the clay soil. In the sandy loam soil N2O emissions were significantly different among all N treatments, but in the clay soil only the manure treatment had significantly higher N2O emissions. It is thought that the major differences between the two soils controlling both N2O and CH4 emissions were cation exchange capacity (CEC) and percent water-filled pore space (%WFPS). We speculate that the higher CEC in the clay soil reduced N availability through increased adsorption of NH4+ compared to the sandy loam soil. In addition the higher average %WFPS in the sandy loam may have favored higher denitrification and CH4 production than in the clay soil.
  • Authors:
    • Kallenbach, C. M.
  • Volume: MS Thesis.
  • Year: 2008
  • Authors:
    • Wirth, T.
    • Pape, D.
    • Archibeque, S. L.
    • Johnson, K. A.
    • Kebreab, E.
  • Source: Journal of Animal Science
  • Volume: 86
  • Issue: 10
  • Year: 2008
  • Summary: Methane production from enteric fermentation in cattle is one of the major sources of anthropogenic greenhouse gas emission in the United States and worldwide. National estimates of methane emissions rely on mathematical models such as the one recommended by the Intergovernmental Panel for Climate Change (IPCC). Models used for prediction of methane emissions from cattle range from empirical to mechanistic with varying input requirements. Two empirical and 2 mechanistic models (COWPOLL and MOLLY) were evaluated for their prediction ability using individual cattle measurements. Model selection was based on mean square prediction error (MSPE), concordance correlation coefficient, and residuals vs. predicted values analyses. In dairy cattle, COWPOLL had the lowest root MSPE and greatest accuracy and precision of predicting methane emissions (correlation coefficient estimate = 0.75). The model simulated differences in diet more accurately than the other models, and the residuals vs. predicted value analysis showed no mean bias (P = 0.71). In feedlot cattle, MOLLY had the lowest root MSPE with almost all errors from random sources ( correlation coefficient estimate = 0.69). The IPCC model also had good agreement with observed values, and no significant mean (P = 0.74) or linear bias (P = 0.11) was detected when residuals were plotted against predicted values. A fixed methane conversion factor (Ym) might be an easier alternative to diet-dependent variable Ym. Based on the results, the 2 mechanistic models were used to simulate methane emissions from representative US diets and were compared with the IPCC model. The average Ym in dairy cows was 5.63% of GE (range 3.78 to 7.43%) compared with 6.5% +/- 1% recommended by IPCC. In feedlot cattle, the average Ym was 3.88% (range 3.36 to 4.56%) compared with 3% +/- 1% recommended by IPCC. Based on our simulations, using IPCC values can result in an overestimate of about 12.5% and underestimate of emissions by about 9.8% for dairy and feedlot cattle, respectively. In addition to providing improved estimates of emissions based on diets, mechanistic models can be used to assess mitigation options such as changing source of carbohydrate or addition of fat to decrease methane, which is not possible with empirical models. We recommend national inventories use diet-specific Ym values predicted by mechanistic models to estimate methane emissions from cattle.
  • Authors:
    • Laird, D. A.
  • Source: Agronomy Journal
  • Volume: 100
  • Issue: 1
  • Year: 2008
  • Summary: Processing biomass through a distributed network of fast pyrolyzers may be a sustainable platform for producing energy from biomass. Fast pyrolyzers thermally transform biomass into bio-oil, syngas, and charcoal. The syngas could provide the energy needs of the pyrolyzer. Bio-oil is an energy raw material ([~]17 MJ kg-1) that can be burned to generate heat or shipped to a refinery for processing into transportation fuels. Charcoal could also be used to generate energy; however, application of the charcoal co-product to soils may be key to sustainability. Application of charcoal to soils is hypothesized to increase bioavailable water, build soil organic matter, enhance nutrient cycling, lower bulk density, act as a liming agent, and reduce leaching of pesticides and nutrients to surface and ground water. The half-life of C in soil charcoal is in excess of 1000 yr. Hence, soil-applied charcoal will make both a lasting contribution to soil quality and C in the charcoal will be removed from the atmosphere and sequestered for millennia. Assuming the United States can annually produce 1.1 x 109 Mg of biomass from harvestable forest and crop lands, national implementation of The Charcoal Vision would generate enough bio-oil to displace 1.91 billion barrels of fossil fuel oil per year or about 25% of the current U.S. annual oil consumption. The combined C credit for fossil fuel displacement and permanent sequestration, 363 Tg per year, is 10% of the average annual U.S. emissions of CO2-C.
  • Authors:
    • Thompson, M.
    • Wershaw, R. L.
    • Martens, D. A.
    • Chappell, M. A.
    • Laird, D. A.
  • Source: Geoderma
  • Volume: 143
  • Issue: 1-2
  • Year: 2008
  • Summary: Most models of soil humic substances include a substantial component of aromatic C either as the backbone of humic heteropolymers or as a significant component of supramolecular aggregates of degraded biopolymers. We physically separated coarse (0.2-2.0 [micro]m e.s.d.), medium (0.02-0.2 [micro]m e.s.d.), and fine (>0.02 [micro]m e.s.d.) clay subfractions from three Midwestern soils and characterized the organic material associated with these subfractions using 13 C-CPMAS-NMR, DTG, SEM-EDX, incubations, and radiocarbon age. Most of the C in the coarse clay subfraction was present as discrete particles (0.2-5 [micro]m as seen in SEM images) of black carbon (BC) and consisted of approximately 60% aromatic C, with the remainder being a mixture of aliphatic, anomeric and carboxylic C. We hypothesize that BC particles were originally charcoal formed during prairie fires. As the BC particles aged in soil their surfaces were oxidized to form carboxylic groups and anomeric and aliphatic C accumulated in the BC particles either by adsorption of dissolved biogenic compounds from the soil solution or by direct deposition of biogenic materials from microbes living within the BC particles. The biogenic soil organic matter was physically separated with the medium and fine clay subfractions and was dominated by aliphatic, anomeric, and carboxylic C. The results indicate that the biogenic humic materials in our soils have little aromatic C, which is inconsistent with the traditional heteropolymer model of humic substances.
  • Authors:
    • Hepperly, P.
    • LaSalle, T. J.
  • Year: 2008
  • Authors:
    • Schlesinger, W. H.
    • Stemmler ,E. A.
    • Jackson, R. B.
    • Finzi, A. C.
    • Ryals, R.
    • Gaindh, D.
    • Ziegler, S. E.
    • Billings, S. A.
    • Lichter, J.
  • Source: Global Change Biology
  • Volume: 14
  • Issue: 12
  • Year: 2008
  • Summary: The impact of anthropogenic CO2 emissions on climate change may be mitigated in part by C sequestration in terrestrial ecosystems as rising atmospheric CO2 concentrations stimulate primary productivity and ecosystem C storage. Carbon will be sequestered in forest soils if organic matter inputs to soil profiles increase without a matching increase in decomposition or leaching losses from the soil profile, or if the rate of decomposition decreases because of increased production of resistant humic substances or greater physical protection of organic matter in soil aggregates. To examine the response of a forest ecosystem to elevated atmospheric CO2 concentrations, the Duke Forest Free-Air CO2 Enrichment (FACE) experiment in North Carolina, USA, has maintained atmospheric CO2 concentrations 200 mu L L-1 above ambient in an aggrading loblolly pine (Pinus taeda) plantation over a 9-year period (1996-2005). During the first 6 years of the experiment, forest-floor C and N pools increased linearly under both elevated and ambient CO2 conditions, with significantly greater accumulations under the elevated CO2 treatment. Between the sixth and ninth year, forest-floor organic matter accumulation stabilized and C and N pools appeared to reach their respective steady states. An additional C sink of similar to 30 g C m(-2) yr(-1) was sequestered in the forest floor of the elevated CO2 treatment plots relative to the control plots maintained at ambient CO2 owing to increased litterfall and root turnover during the first 9 years of the study. Because we did not detect any significant elevated CO2 effects on the rate of decomposition or on the chemical composition of forest-floor organic matter, this additional C sink was likely related to enhanced litterfall C inputs. We also failed to detect any statistically significant treatment effects on the C and N pools of surface and deep mineral soil horizons. However, a significant widening of the C : N ratio of soil organic matter (SOM) in the upper mineral soil under both elevated and ambient CO2 suggests that N is being transferred from soil to plants in this aggrading forest. A significant treatment x time interaction indicates that N is being transferred at a higher rate under elevated CO2 (P=0.037), suggesting that enhanced rates of SOM decomposition are increasing mineralization and uptake to provide the extra N required to support the observed increase in primary productivity under elevated CO2.
  • Authors:
    • Millard-Ball, A.
  • Year: 2008
  • Summary: This paper provides an analysis of the potential to develop a carbon offset protocol for Bus Rapid Transit (BRT) projects, focused on the U.S. voluntary carbon market. It describes experience with the costs, ridership and emission impacts of BRT projects to date, and existing methodologies to quantify the emissions impacts of BRT, particularly those developed for the Clean Development Mechanism (CDM). It then analyzes key issues for a potential protocol, including development of the baseline scenario, quantifying leakages, and ownership of emission reduction credits. The paper concludes by providing an order-of-magnitude estimate of the emission reduction potential.
  • Authors:
    • De Moura, R. L.
    • Klonsky, K. M.
    • Campbell-Mathews, M.
    • Canevari, M.
    • Frate, C. A.
    • Mueller, S. C.
  • Source: University of California Cooperative Extension Publication
  • Year: 2008
  • Authors:
    • de Steiguer, J. E.
  • Source: Rangelands
  • Volume: 30
  • Issue: 2
  • Year: 2008