Recirculation of biomass ashes onto forest soils: ash composition, mineralogy and leaching properties

Abstract

In Denmark, increasing amounts of wood ashes are generated from biomass combustion for energy production. The utilisation of ashes on top of forest soil for liming purposes has been proposed asan alternative to landfilling. Danish wood ash samples were collected and characterised with respect to chemical composition, mineralogy and leaching properties (batch leaching at L/S 2 and 10L/kg, and pH-dependent leaching at 10L/kg). Large variations in the ash liming properties were observed (ANC: 1.8-6.4meqH/g), indicating that similar soil application dosages may result in different liming effects. High contents of Ca, Si, P, K and Mg were observed in all samples, while the highest contents of S and N were found in fly ashes and mixed ashes (combination of fly and bottom ashes). Similarly, the highest contents of some trace metals, e.g. Cd, Mo and Se, were observed for fly ash. Releases of major, minor and trace elements were affected significantly by pH: high releases of PO, Mg, Zn, Cu and Cd were found for acidic conditions relevant to forest soils, while the highest releases of Mo and Cr were observed in alkaline conditions. Mineral phases were selected based on XRD analyses and the existing literature, and they were applied as inputs for the geochemical modelling of pH-dependent leaching. Mineral dissolution was found adequate for a wide range of major elements and nutrients, while the description of trace elements could be done only for parts of the pH-range. Content and leaching of PAHs were observed below detection limits. The source-term release of Ca, K, Mg, Mn, and P in acidic conditions relevant to forest soils was higher than ten years of atmospheric deposition, in contrast to the relatively low release of Al, Fe and Na. The potential release of Cd was found to be the most critical element compared with soil quality criteria, whereas the maximum theoretical loads of Ba, Cd, Cr, Sr, Mo, Ni, Pb, Sb, Se, Sn and V were relatively low.

Total RNA-sequencing reveals multi-level microbial community changes and functional responses to wood ash application in agricultural and forest soil

“…DOC and phosphate concomitantly increased. Several factors may contribute to this: (I) pH dependent changes in solubility (Evans et al , 2012; Maresca et al , 2017), (II) release from dead organisms incapable of coping with the wood ash or wood ash induced changes to the soil system, (III) increased mineralization rates after wood ash application (Bååth & Arnebrant, 1994; Vestergård et al , 2018) and (IV) the phosphorous in the bio-ash (Pitman, 2006; Maresca et al , 2017).…”

“…We homogenized the ash by sieving (2 mm). Maresca et al (2017) provide a list of mineral nutrients and heavy metals in the ash.…”

“…However, wood ash application affects several soil physicochemical parameters important to the structure and function of microbial communities; e.g. pH, electrical conductivity and dissolved organic carbon (DOC), (Ohno & Susan Erich, 1990; Demeyer et al , 2001; Pitman, 2006; Augusto et al , 2008; Maresca et al , 2017; Hansen et al , 2017). As the soil micro-biota carries out an array of key biochemical processes (Blagodatskaya & Kuzyakov, 2013), knowledge of its response to disturbance is important; not least in production soils due to potential impact on soil fertility.…”

Efecto del pretratamiento con ácido sulfúrico diluido sobre la hidrólisis enzimática del Panicum maximum

“…Fracción sólida Fracción líquida [36]. Los cationes tienden a neutralizar una proporción del ácido sulfúrico empleado en algunos pretratamientos de biomasa para producción de etanol [17].…”

Wood ash and water availability in the production of Paiaguás-grass

“…In this context, the use of waste such as wood ash in agriculture has become an alternative. It can be applied to the soil as fertilizer and as a neutralizer of soil acidity and may provide nutrients to the soil, such as calcium, magnesium, potassium, phosphorus and micronutrients, essential elements for plant growth and development (Hansen et al, 2018;Maresca et al 2017;Ingerslev et al, 2011). There is evidence that the increase in pH is greater in soils with low pH and low organic-matter content (Ohno, 1992), characteristics of tropical soils.…”