Hydrochar enhances growth of poplar for bioenergy while marginally contributing to direct soil carbon sequestration

Abstract

Hydrothermal carbonization (HTC) has been proposed as an alternative method to pyrolysis for producing C-rich amendments for soil C sequestration. However, the use of hydrochar (HC) as soil amendment is still controversial due to the limited information on the potential benefits and trade-offs that may follow its application into soil. This study investigated the effects of HC starting from maize silage on plant growth in a 2-year controlled experiment on poplar for bioenergy and evaluated HC stability in soil by periodic soil respiration and isotopic (δ13C) measurements. HC application caused a substantial and significant increase in plant biomass after one and two years after planting, and no evident signs of plant diseases were evident. Isotopic analysis on soil and CO2 efflux showed that slightly less than half of the C applied was re-emitted as CO2 within 12 months. On the contrary, considering that the difference in the amount of N fixed in wood biomass in treated and not-treated poplars was 16.6 ± 4.8 g N m-2 and that the soil N stocks after one year since application did not significantly change, we estimated that approximately 85% of the N applied with HC could have been potentially lost as leachate or volatilized into the atmosphere as N₂O, in response to nitrification/denitrification processes in the soil. Thus, the permanence, additionality and leakage of C sequestration strategy using HC are deeply discussed.

References Allwright MR, Taylor G (2016) Molecular breeding for improved second generation bioenergy crops. Trends in Plant Science, 21, 43–54. Baronti S, Alberti G, Vedove GD et al. (2010) The Biochar Option to Improve Plant Yields : First Results From Some Field and Pot Experiments in Italy. 3–11. Busch D, Kammann C, Grünhage L, Müller C (2012) Simple biotoxicity tests for evaluation of carbonaceous soil additives: establishment and reproducibility of four test procedures. Journal of Environmental Quality, 41, 1023–1032. Busch D, Stark A, Kammann CI, Glaser B (2013) Genotoxic and phytotoxic risk assessment of fresh and treated hydrochar from hydrothermal carbonization compared to biochar from pyrolysis. Ecotoxicology and Environmental Safety, 97, 59–66. Ceotto E, Di Candilo M (2011) Medium-term effect of perennial energy crops on soil organic carbon storage. Italian Journal of Agronomy, 6, 33. Ceotto E, Castelli F, Moschella A, Diozzi M, Di Candilo M (2016) Poplar short rotation coppice is not a first choice crop for cattle slurry fertilization: biomass yield and nitrogen-use efficiency. Industrial Crops and Products, 85, 167–173. Coleman M, Tolsted D, Nichols T, Johnson W, Wene E, Houghtaling T (2006) Post-establishment fertilization of Minnesota hybrid poplar plantations. Biomass and Bioenergy, 30, 740–749. Del Galdo I, Six J, Peressotti A, Cotrufo F (2003) Assessing the impact of land-use change on soil C sequestration in agricultural soils by means of organic matter fractionation and stable C isotopes. Global Change Biology, 9, 1204–1213. Delle Vedove G, Alberti G, Zuliani M, Peressotti A, Inglima I, Zerbi G (2007) Automated monitoring of soil respiration: an improved automatic chamber system. Italian Journal of Agronomy, 2, 377–382. Eibisch N, Schroll R, Fuß R, Mikutta R, Helfrich M, Flessa H (2015) Pyrochars and hydrochars differently alter the sorption of the herbicide isoproturon in an agricultural soil. Chemosphere, 119, 155–162. Ekpo U, Ross AB, Camargo-Valero MA, Williams PT (2016) A comparison of product yields and inorganic content in process streams following thermal hydrolysis and hydrothermal processing of microalgae, manure and digestate. Bioresource Technology, 200, 951–960. EPA (2007) METHOD 8270D Semivolatile Organic Compounds by Gas Chromatography/Mass Spectrometry (GC/MS). Fang J, Gao B, Chen J, Zimmerman AR (2015) Hydrochars derived from plant biomass under various conditions: characterization and potential applications and impacts. Chemical Engineering Journal, 267, 253–259. Fontaine S, Barot S, Barré P, Bdioui N, Mary B, Rumpel C (2007) Stability of organic carbon in deep soil layers controlled by fresh carbon supply. Nature, 450, 277–280. George C, Wagner M, Kücke M, Rillig MC (2012) Divergent consequences of hydrochar in the plant–soil system: Arbuscular mycorrhiza, nodulation, plant growth and soil aggregation effects. Applied Soil Ecology, 59, 68–72. Han L, Ro KS, Sun K, Sun H, Wang Z, Libra JA, Xing B (2016) New evidence for high sorption capacity of hydrochar for hydrophobic organic pollutants. Environmental Science and Technology, 50, 13274–13282. Joos O, Saurer M, Heim A, Hagedorn F, Schmidt MWI, Siegwolf RTW (2008) Can we use the CO2 concentrations determined by continuous-flow isotope ratio mass spectrometry from small samples for the Keeling plot approach? Rapid Communications in Mass Spectrometry, 22, 4029–4034. Kammann C, Ratering S, Eckhard C, Müller C (2012) Biochar and hydrochar effects on greenhouse gas (carbon dioxide, nitrous oxide, and methane) fluxes from soils. Journal of Environmental Quality, 41, 1052–1066. Kauter D, Lewandowski I, Claupein W (2003) Quantity and quality of harvestable biomass from Populus short rotation coppice for solid fuel use—a review of the physiological basis and management influences. Biomass and Bioenergy, 24, 411–427. Keith A, Singh B, Singh BP (2011) Interactive priming of biochar and labile organic matter mineralization in a smectite-rich soil. Environmental Science and Technology, 45, 9611–9618. Körner C (2017) A matter of tree longevity. Science, 355, 130–131. Kuzyakov Y, Friedel J, Stahr K (2000) Review of mechanisms and quantification of priming effects. Soil Biology and Biochemistry, 32, 1485–1498. Lehmann J, Gaunt J, Rondon M (2006) Bio-char sequestration in terrestrial ecosystems – a review. Mitigation and Adaptation Strategies for Global Change, 11, 395–419. Lehrter JC, Cebrian J (2010) Uncertainty propagation in an ecosystem nutrient budget. Ecological Applications, 20, 508–524. Libra J, Ro K, Kammann C et al. (2011) Hydrothermal carbonization of biomass residuals: a comparative review of the chemistry, processes and applications of wet and dry pyrolysis. Biofuels, 2, 89–124. Malghani S, Gleixner G, Trumbore SE (2013) Chars produced by slow pyrolysis and hydrothermal carbonization vary in carbon sequestration potential and greenhouse gases emissions. Soil Biology and Biochemistry, 62, 137–146. Malghani S, Jüschke E, Baumert J, Thuille A, Antonietti M, Trumbore S, Gleixner G (2014) Carbon sequestration potential of hydrothermal carbonization char (hydrochar) in two contrasting soils; results of a 1-year field study. Biology and Fertility of Soils, 51, 123–134. Mazzoleni S, Bonanomi G, Incerti G et al. (2015) Inhibitory and toxic effects of extracellular self-DNA in litter: a mechanism for negative plant-soil feedbacks? New Phytologist, 205, 1195–1210. Meyer S, Glaser B, Quicker P (2011) Technical, economical, and climate-related aspects of biochar production technologies: a literature review. Environmental Science and Technology, 45, 9473–9483. Naisse C, Girardin C, Davasse B, Chabbi A, Rumpel C (2014) Effect of biochar addition on C mineralisation and soil organic matter priming in two subsoil horizons. Journal of Soils and Sediments, 15, 825–832. Naisse C, Girardin C, Lefevre R, Pozzi A, Maas R, Stark A, Rumpel C (2015) Effect of physical weathering on the carbon sequestration potential of biochars and hydrochars in soil. GCB Bioenergy, 7, 488–496. Ngao J, Epron D, Brechet C, Granier A (2005) Estimating the contribution of leaf litter decomposition to soil CO2 efflux in a beech forest using 13C depleted litter. Global Change Biology, Global Change Biology, 11, 1768–1776. Phillips DL, Gregg JW (2001) Uncertainty in source partitioning using stable isotopes. Oecologia, 127, 171–179. Reibe K, Götz K-P, Roß C-L, Döring TF, Ellmer F, Ruess L (2015) Impact of quality and quantity of biochar and hydrochar on soil Collembola and growth of spring wheat. Soil Biology and Biochemistry, 83, 84–87. Riaz M, Roohi M, Arif MS et al. (2017) Corncob-derived biochar decelerates mineralization of native and added organic matter (AOM) in organic matter depleted alkaline soil. Geoderma, 294, 19–28. Schimmelpfennig S, Glaser B (2012) One step forward toward characterization: some important material properties to distinguish biochars. Journal of Environmental Quality, 41, 1001–1013. Schimmelpfennig S, Müller C, Grünhage L, Koch C, Kammann C (2014) Biochar, hydrochar and uncarbonized feedstock application to permanent grassland—Effects on greenhouse gas emissions and plant growth. Agriculture, Ecosystems and Environment, 191, 39–52. Schimmelpfennig S, Kammann C, Moser G, Grünhage L, Müller C (2015) Changes in macro- and micronutrient contents of grasses and forbs following Miscanthus x giganteus feedstock, hydrochar and biochar application to temperate grassland. Grass and Forage Science, 70, 582–599. Smith P (2016) Soil carbon sequestration and biochar as negative emission technologies. Global Change Biology, 22, 1315–1324. Steinbeiss S, Gleixner G, Antonietti M (2009) Effect of biochar amendment on soil carbon balance and soil microbial activity. Soil Biology and Biochemistry, 41, 1301–1310. Sun K, Ro K, Guo M, Novak J, Mashayekhi H, Xing B (2011) Sorption of bisphenol A, 17α-ethinyl estradiol and phenanthrene on thermally and hydrothermally produced biochars. Bioresource Technology, 102, 5757–5763. Van Acker R, Leple J-C, Aerts D et al. (2014) Improved saccharification and ethanol yield from field-grown transgenic poplar deficient in cinnamoyl-CoA reductase. Proceedings of the National Academy of Sciences, 111, 845–850. Ventura M, Alberti G, Viger M et al. (2015) Biochar stability and priming effect on SOM decomposition in two European short rotation coppices. Global Change Biology Bioenergy, 7, 1150–1160. Wang J, Xiong Z, Kuzyakov Y (2016) Biochar stability in soil: meta-analysis of decomposition and priming effects. GCB Bioenergy, 8, 512–523. Wiedner K, Naisse C, Rumpel C, Pozzi A, Wieczorek P, Glaser B (2013) Chemical modification of biomass residues during hydrothermal carbonization – What makes the difference, temperature or feedstock? Organic Geochemistry, 54, 91–100.