Biochar research activities and their relation to development and environmental quality. A meta-analysis

Biochar is the solid product that results from pyrolysis of organic materials. Its addition to highly weathered soils changes physico-chemical soil properties, improves soil functions and enhances crop yields. Highly weathered soils are typical of humid tropics where agricultural productivity is low and needs to be raised to reduce human hunger and poverty. However, impact of biochar research on scientists, politicians and end-users in poor tropical countries remains unknown; assessing needs and interests on biochar is essential to develop reliable knowledge transfer/translation mechanisms. The aim of this publication is to present results of a meta-analysis conducted to (1) survey global biochar research published between 2010 and 2014 to assess its relation to human development and environmental quality, and (2) deduce, based on the results of this analysis, priorities required to assess and promote the role of biochar in the development of adapted and sustainable agronomic methods. Our main findings reveal for the very first time that: (1) biochar research associated with less developed countries focused on biochar production technologies (26.5 ± 0.7%), then on biochars’ impact on chemical soil properties (18.7 ± 1.2%), and on plant productivity (17.1 ± 2.6%); (2) China dominated biochar research activities among the medium developed countries focusing on biochar production technologies (26.8 ± 0.5%) and on use of biochar as sorbent for organic and inorganic compounds (29.1 ± 0.4%); and (3) the majority of biochar research (69.0±2.9%) was associated with highly developed countries that are able to address a higher diversity of questions. Evidently, less developed countries are eager to improve soil fertility and agricultural productivity, which requires transfer and/or translation of biochar knowledge acquired in highly developed countries. Yet, improving local research capacities and encouraging synergies across scientific disciplines and countries are crucial to foster development of sustainable agronomy in less developed countries. © 2017, The Author(s)

Analysis and modeling of vadose zone gas transport : modeling methane emissions from landfills

Includes bibliographical references (pages [95]-102)The movement of gases between the soil and the atmosphere can occur by both diffusion and convection. This thesis examines the potential driving and controlling forces of gas movement through the vadose zone. A three-dimensional gas diffusional model was developed and tested with field data. Field instruments for the continuous monitoring of subsurface pressures and temperatures were developed and surface methane emission values were obtained from three landfill sites in California, Illinois, and Alabama. These emission values were compared to the developed gas diffusional model (LMEM [Landfill Methane Emission Model]) for the quantification of methane emission from the surface of landfills. The developed LMEM model differs from previous gas transport models in that it deals with the soil separately from the gas diffusion algorithm. The soil is handled as an obstruction in the flow path versus modifying the gas diffusional coefficient to account for the soil matrix. In this fashion, different soil characteristics can be more accurately modeled. The model’s dependency on soil moisture, porosity, and depth of cover were also examined. The collected field pressure and temperature data indicate a strong correlation between the air temperature and shallow subsurface pressures (15 %). The model predicted the surface methane emissions better at the semi-arid site (California) than at the humid sites (Illinois and Alabama). However, even though the model overestimated the absolute magnitude of the methane flux at the humid sites, the direction of the flux still was accurately determined. This discrepancy at higher moisture contents exists because of the oversimplification in the moisture algorithm of the model. The moisture interactions in the model were all assumed to follow Henry’s law. The model was found to be highly sensitive to moisture and porosity conditions in the shallow (<25 cm) soil. As the thickness of the cover increased the sensitivity of the model to these variables decreased.M.S. (Master of Science

Impact of Biochar on Earthworm Populations: A Review

Despite the overwhelming importance of earthworm activity in the soil system, there are a limited number of studies that have examined the impact resulting from biochar addition to soil. Biochar is part of the black carbon continuum of chemo-thermal converted biomass. This review summarizes existing data pertaining to earthworms where biochar and other black carbon substances, including slash-and-burn charcoals and wood ash, have been applied. After analyzing existing studies on black carbon, we identified that these additions have a range from short-term negative impacts to long-term null effects on earthworm population density and total biomass. Documented cases of mortality were found with certain biochar-soil combinations; the cause is not fully understood, but hypothesized to be related to pH, whether the black carbon is premoistened, affects feeding behaviors, or other unknown factors. With wood ashes, negative impacts were overcome with addition of other carbon substrates. Given that field data is limited, soils amended with biochar did not appear to cause significant long-term impacts. However, this may indicate that the magnitude of short-term negative impacts on earthworm populations can be reduced with time

Sorption of ammonium and nitrate to biochars is electrostatic and pH-dependent

Biochars are potentially effective sorbents for NH4+ and NO3- in water treatment and soil applications. Here we compare NH4+ and NO3- sorption rates to acid-washed biochars produced from red oak (Quercus rubra) and corn stover (Zea mays) at three pyrolysis temperatures (400, 500 and 600 °C) and a range of solution pHs (3.5-7.5). Additionally, we examined sorption mechanisms by quantification of NH4+ and NO3- sorption, as well as Ca2+ and Cl- displacement for corn stover biochars. Solution pH curves showed that NH4+ sorption was maximized (0.7-0.8 mg N g-1) with low pyrolysis temperature (400 °C) biochar at near neutral pH (7.0-7.5), whereas NO3- sorption was maximized (1.4-1.5 mg N g-1) with high pyrolysis temperatures (600 °C) and low pH (3.5-4). The Langmuir (r2 = 0.90-1.00) and Freundlich (r2 = 0.81-0.97) models were good predictors for both NH4+ (pH 7) and NO3- (pH 3.7) sorption isotherms. Lastly, NH4+ and NO3- displaced Ca2+ and Cl-, respectively, from previously CaCl2-saturated corn stover biochars. Results from the pH curves, Langmuir isotherms, and cation displacement curves all support the predominance of ion exchange mechanisms. Our results demonstrate the importance of solution pH and chemical composition in influencing NH4+ and NO3- sorption capacities of biochar.Global Climate and Energy Project [640 60413992-112883-A]Open access journal.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Understanding Activation Effects on Low-Temperature Biochar for Optimization of Herbicide Sorption

Activation treatments are often used as a means of increasing a biochar&rsquo;s sorption capacity for agrochemical compounds but can also provide valuable insight into sorption mechanisms. This work investigates the effects of H2O2 activation on a low-temperature (350 &deg;C) grape wood biochar, evaluates subsequent changes to the removal efficiency (RE) of cyhalofop and clomazone, and elucidates potential sorption mechanisms. Activation by H2O2 decreased the biochar pH, ash content, and C content. Additionally, the biochar O content and surface area increased following activation, and Fourier transform infrared spectroscopy (FTIR) data suggested a slight increase in surface O groups and a decrease in aliphatic C. Cyhalofop RE significantly increased following activation, while clomazone RE was unchanged. The increased sorption of cyhalofop was attributed to pH effects and charge-based interactions with biochar O moieties. Results from this study suggest that H2O2 activation treatments on low-temperature biochars may improve the removal of organic acid herbicides but are of little value in optimizing the removal of polar, non-ionizable herbicides

Genetic Variation for Life History Sensitivity to Seasonal Warming in Arabidopsis thaliana

Climate change has altered life history events in many plant species; however, little is known about genetic variation underlying seasonal thermal response. In this study, we simulated current and three future warming climates and measured flowering tim