Biochar, hydrochar and uncarbonized feedstock application to permanent grassland—Effects on greenhouse gas emissions and plant growth

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Highlights

Abstract

Both reductions of greenhouse gas emissions and carbon sequestration have the potential to reduce global climate warming and avoid dangerous climate change. We assessed the sequestration potential as well as possible risks and benefits of carbon amendments (16 ± 4% of soil organic C) from Miscanthus × giganteus in different carbonization stages of a temperate grassland soil together with pig slurry: (1) untreated dried biomass (feedstock), (2) hydrothermally carbonized biomass (hydrochar) and (3) pyrolyzed biomass (biochar) in comparison to a control (only pig slurry application).

The field study was complemented by a laboratory incubation study, followed by a growth experiment with Lolium perenne. In the field, greenhouse gas emissions (CO2, N2O, and CH4) were monitored weekly over 1.5 years and over three months in the lab. Initial nitrogen losses via ammonia emissions after substrate–slurry application were assessed in an additional greenhouse study.

We found that biochar reduced soil and ecosystem respiration in incubation and in the field, respectively. Additionally, biochar improved methane oxidation, though restricted by emissions outbursts due to slurry amendment. It also reduced N2O emissions significantly in the lab study but not in the field. Hydrochar and feedstock proved to be easily degradable in incubation, but had no effect on ecosystem respiration in the field. Feedstock amendment significantly increased N2O emissions in incubation and one year after application likewise in the field. In a growth experiment subsequent to the incubation, only biochar amendment increased L. perenne biomass (+29%) significantly, likely due to N retention. In the field, biochar caused a significant shift in the plant species composition from grasses to forbs, whereas hydrochar significantly reduced yields within two growth periods (2011 and 2012). Ammonia emissions were significantly higher with feedstock and biochar compared to the control or acidic hydrochar. The overall results indicate that biochar is better suited for C sequestration and GHG mitigation in grasslands than hydrochar or the uncarbonized feedstock. However, NH3 emission reductions may only occur when the biochar is neutral or slightly acidic.

Introduction

Biochar, an organic carbon soil amendment, has great potential to alleviate the CO2 accumulated in the atmosphere by sequestration of recalcitrant carbon into the soil (Lehmann, 2007, Glaser et al., 2009). Such a biological sequestration of CO2 would be cost-effective (Blair et al., 2006) and serve as a fast action strategy for climate change mitigation (Molina et al., 2009). Positive effects of biochar amendments on crop yields (Jeffery et al., 2011, Biederman and Harpole, 2013) would provide an additional incentive for its agricultural use. However, before using biochar as a carbon sink and environmental management tool, it must be proven that it remains stable after soil application and that such application does not create adverse effects, e.g. increased greenhouse gas emissions (GHG). Greenhouse gases such as carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4), increase the radiative forcing of the Earthś atmosphere (Houghton et al., 1997) by contributing to ozone depletion (N2O) (Ravishankara et al., 2009) and by interaction with aerosols (CH4) (Shindell et al., 2009). Possible positive feedback effects of biochar or biochar–slurry mixtures on GHG emissions would be detrimental for the field use of biochar as a carbon sequestration tool. To date, the effects of biochar on GHG emissions are rather diverse. They depend on the biochar production process parameters, the feedstock used, the ecosystem and soil properties to which biochar is applied, and the strategy of application and (agricultural) management.

Biochar could be beneficial as a soil conditioner in degraded or naturally poor soils by improving nutrient availability and mycorrhiza abundance (Chan et al., 2008, Alvum-Toll et al., 2011). Although it might not be needed as a soil conditioner in fertile temperate soils, an increment of the grassland carbon stocks by carbon amendment may act as carbon sink due to long C turnover times (Scurlock and Hall, 1998). Biochar use in grasslands may even be based on ancient soil types in temperate climates, i.e. chernozems, of which some are assumed to have developed under grassland (steppe) vegetation (Eckmeier et al., 2007). For anthropogenically used grasslands, which are typically used for livestock breeding with considerable amounts of manure and urine accumulation, positive biochar–slurry interactions may offer new ways for reducing GHG emissions (Winsley, 2007). Indeed, Bruun et al. (2011) showed in an incubation study that the addition of 3% fast pyrolysis biochar on a mass basis reduced CO2 and N2O emissions from a slurry amended soil significantly. Biochar and slurry can also reduce the wind erosion of biochar during application and alleviate the odor of the slurry (Blackwell et al., 2009). However, the promising idea of charging biochar with the nutrients contained in the slurry still has to be proven effective. Experiments with biochar and slurry showed that biochar can bind ammonia by surface interactions (Spokas et al., 2012). Furthermore, biochar reduced NO3 and total N leaching from manure-amended soil significantly (Laird et al., 2010, Ventura et al., 2013), with subsequent positive effects on plant-available nitrogen and thus plant growth. Concerning the N-efficiency of ecosystems, ammonia and denitrificatory N losses (including N2O emissions) are very important factors, as well as losses of NO3single bondN by leaching, the main pathways for losses of N from an ecosystem. NH3 losses from grasslands can account for up to 28% (grazed pasture) or 27% (grassland fertilized with pig slurry) of the annual N input (Ball and Keeney, 1981, Pain et al., 1989), depending on farm management practices. N2O emissions can add up to 2–2.2% total N loss of added fertilizer of a grassland ecosystem (Velthof et al., 1996, Clayton et al., 1997).

However, results of biochar effects on ecosystems in temperate climates are still scarce, and the interactions of different biochar–slurry mixtures in the field still have to be elucidated. Consequently, the background of this study was to assess possible risks and chances of carbon amendment co-applied with slurry to a temperate grassland site with a focus on GHG- and ammonia emissions. We hypothesized that, first, the materials would degrade in the sequence of their carbonization grade: feedstock > hydrochar > biochar and that degradation would be measurable in the ecosystem respiration. To assess possible priming effects of biochar on hydrochar or vice versa, we introduced a mixed treatment in the incubation study. Second, we hypothesized that biomass growth will be negatively impacted by hydrochar application, as reported by others who found negative effects on plant germination and growth with hydrochar use in soils (Bargmann et al., 2012, Gajić and Koch, 2012). Third, that biochar will reduce N2O and CO2 emissions (Augustenborg et al., 2012, Case et al., 2012, Dempster et al., 2012), improve CH4 oxidation (Karhu et al., 2011, Liu et al., 2011), and that hydrochar will have rather adverse effects on the GHG balance (Kammann et al., 2012), as shown by incubation studies so far.

Section snippets

Laboratory incubation

A laboratory study was carried out with the same parameters as the field experiment but under controlled conditions. Soil for incubation was taken from the top 15 cm of the experimental field site prior to initiation of the field experiment. The grassland site in Linden, near Giessen, Germany (50̊32′N und 8̊41.3′E) has been managed extensively for decades as grassland with two cuts per year (Jäger et al., 2003). The soil, a haplic stagnosol (WRB, 2006), has a soil texture of 25% sand, 28% clay,

Statistics

Statistics were carried out using Microsoft Excel 2010, SigmaPlot 11.0 and 12.0 and IBM SPSS Statistics Versions 19 and 20. The differences in the cumulated gas fluxes before and after slurry addition, as well as differences in Nmin concentrations among the treatments, were analyzed by one way Anova. Potential differences of cumulated (linearly interpolated) vs measured carbon contents from the incubation were determined using a paired t-test and differences in pH and WHC were determined using

Water holding capacity

Generally, the addition of C-substrates led to an improvement of the soilś WHC. The addition of hydrochar alone (+14%) and mixture with biochar (+25%) led to significant increases of the WHC (t-test, p < 0.05).

CO2 emissions and carbon balance

Carbon dioxide (CO2) effluxes during the three months incubation period were in the order: feedstock > hydrochar > hydrochar–biochar mix > control  biochar, p = 0.001) (Fig. 1A and B). In the period prior to slurry application, CO2 emissions were significantly reduced in the biochar treatment (81%

Soil and ecosystem respiration and C stability

We measured soil respiration in the incubation (experiment without plants) and ecosystem respiration (Reco) in the field (experiment with plant cover). In the field, plant growth in the GHG measurement plots was not significantly different among treatments. Thus, we argue that significant effects observed in the field were predominantly related to differences in soil respiration.

In the incubation study, soil CO2 efflux was reduced in the biochar treatment before slurry application, whereas

Conclusions

Our hypothesis of a degradation rate in the order biochar < hydrochar < feedstock was confirmed by the results of the incubation study and priming effects of biochar on hydrochar degradation or vice versa were not observed. In the field, increased CO2 emissions from the degradation of the carbon amendments have not been observed; biochar even lowered the emissions significantly compared to the control plots.

The hypothesis that hydrochar would reduce plant growth was confirmed by results from the

Acknowledgments

We thank the agricultural centre Eichhof, Bad Hersfeld, Germany, for providing us with Miscanthus feedstock from a long term field experiment. Hydrothermal carbonization was kindly carried out by Julian and Anke Schwark. The production of the biochar material was carried out by Helmut Gerber, Pyreg GmbH, Bingen. Slurry was kindly provided by the Upper Hardthof Farm (Giessen University, institute for animal breeding and domestic animal genetics). We acknowledge the support of R. Pfanschilling

References (124)

  • D. Chadwick et al.

    Methane fluxes following slurry applications to grassland soils: laboratory experiments

    Agric. Ecosyst. Environ.

    (1997)
  • A. Cross et al.

    The priming potential of biochar products in relation to labile carbon contents and soil organic matter status

    Soil Biol. Biochem.

    (2011)
  • E. Eckmeier et al.

    Pedogenesis of chernozems in Central Europe—a review

    Geoderma

    (2007)
  • D. Focht et al.

    Sequential reduction of nitrate and nitrous oxide under field conditions as brought about by organic amendments and irrigation management

    Soil Biol. Biochem.

    (1979)
  • J. Gulledge et al.

    Different NH4+-inhibition patterns of soil CH4 consumption: a result of distinct CH4-oxidizer populations across sites?

    Soil Biol. Biochem.

    (1997)
  • A. Hilscher et al.

    Degradation of grass-derived pyrogenic organic material, transport of the residues within a soil column and distribution in soil organic matter fractions during a 28 month microcosm experiment

    Org. Geochem.

    (2011)
  • L. Hrapovic et al.

    Intrinsic degradation of volatile fatty acids in laboratory-compacted clayey soil

    J. Contam. Hydrol.

    (2002)
  • B.W. Hütsch

    Methane oxidation in non-flooded soils as affected by crop production—invited paper

    Eur. J. Agron.

    (2001)
  • S. Jeffery et al.

    A quantitative review of the effects of biochar application to soils on crop productivity using meta-analysis

    Agric. Ecosyst. Environ.

    (2011)
  • D. Jones et al.

    Short-term biochar-induced increase in soil CO2 release is both biotically and abiotically mediated

    Soil Biol. Biochem.

    (2011)
  • C. Kammann et al.

    Seasonal variability and mitigation options for N2O emissions from differently managed grasslands

    Environ. Pollut.

    (1998)
  • C. Kammann et al.

    Elevated CO2 stimulates N2O emissions in permanent grassland

    Soil Biol. Biochem.

    (2008)
  • K. Karhu et al.

    Biochar addition to agricultural soil increased CH4 uptake and water holding capacity—results from a short-term pilot field study

    Agric. Ecosyst. Environ.

    (2011)
  • O. Knowles et al.

    Biochar for the mitigation of nitrate leaching from soil amended with biosolids

    Sci. Total Environ.

    (2011)
  • D. Laird et al.

    Biochar impact on nutrient leaching from a Midwestern agricultural soil

    Geoderma

    (2010)
  • Y. Luo et al.

    Short term soil priming effects and the mineralisation of biochar following its incorporation to soils of different pH

    Soil Biol. Biochem.

    (2011)
  • M. Maag et al.

    Nitrous oxide emission by nitrification and denitrification in different soil types and at different soil moisture contents and temperatures

    Appl. Soil Ecol.

    (1996)
  • T. Misselbrook et al.

    SE—structures and environment: slurry application techniques to reduce ammonia emissions: results of some UK field-scale experiments

    Biosyst. Eng.

    (2002)
  • C. Müller et al.

    Processes leading to N2O emissions in grassland soil during freezing and thawing

    Soil Biol. Biochem.

    (2002)
  • M.C. Rillig et al.

    Material derived from hydrothermal carbonization: effects on plant growth and arbuscular mycorrhiza

    Appl. Soil Ecol.

    (2010)
  • S. Saarnio et al.

    Biochar addition indirectly affects N2O emissions via soil moisture and plant N uptake

    Soil Biol. Biochem.

    (2013)
  • K. Alvum-Toll et al.

    Biochar as Soil Amendment

    (2011)
  • J.A. Amaral et al.

    Atmospheric methane consumption by forest soils and extracted bacteria at different pH values

    Appl. Environ. Microbiol.

    (1998)
  • A. Amberger et al.

    Stickstofffraktionen verschiedener Güllen und deren Wirkung im Pflanzenversuch

    Z. Pflanzenernahr. Bodenkd.

    (1982)
  • C.A. Augustenborg et al.

    Biochar and earthworm effects on soil nitrous oxide and carbon dioxide emissions

    J. Environ. Qual.

    (2012)
  • P.R. Ball et al.

    Nitrogen losses from urine-affected areas of a New Zealand pasture under contrasting seasonal conditions

  • I. Bargmann et al.

    Keimung, wachstum und nährstoffdynamik in boden und pflanze nach dem einbringen von biokohlen aus hydrothermaler carbonierung (hydrochar) und pyrolyse (biochar)

    (2012)
  • I. Bargmann et al.

    Effects of hydrochar application on the dynamics of soluble nitrogen in soils and on plant availability

    J. Plant Nutr. Soil Sci.

    (2013)
  • V. Barnett et al.

    Outliers in statistical data.

    (1994)
  • E. Beauchamp et al.

    Carbon sources for bacterial denitrification

    Advances in Soil Science

    (1989)
  • C. Bédard et al.

    Physiology, biochemistry, and specific inhibitors of CH4, NH4+, and CO oxidation by methanotrophs and nitrifiers

    Microbiol. Rev.

    (1989)
  • L.A. Biederman et al.

    Biochar and its effects on plant productivity and nutrient cycling: a meta-analysis

    GCB Bioenergy

    (2013)
  • Bischoff, W.-A., Schwarz, A., Pfenning, J., Pyrolyse-und HTC-Kohlen als Bodenverbesserer auf sandigen Böden im...
  • T. Blair et al.

    Avoiding dangerous climate change

    (2006)
  • R. Bol et al.

    Quantification of priming and CO2 respiration sources following slurry-C incorporation into two grassland soils with different C content

    Rapid Commun. Mass Spectrom.

    (2003)
  • N. Borchard et al.

    Sorption of copper (II) and sulphate to different biochars before and after composting with farmyard manure

    Eur. J. Soil Sci.

    (2012)
  • E.W. Bruun et al.

    Application of biochar to soil and N2O emissions: potential effects of blending fast-pyrolysis biochar with anaerobically digested slurry

    Eur. J. Soil Sci.

    (2011)
  • D. Busch et al.

    Simple biotoxicity tests for evaluation of carbonaceous soil additives: establishment and reproducibility of four test procedures

    J. Environ. Qual.

    (2012)
  • M.S. Castro et al.

    Soil moisture as a predictor of methane uptake by temperate forest soils

    Can. J. For. Res.

    (1994)
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