Wood Biomass Ash (WBA) from the Heat Production Process as a Mineral Amendment for Improving Selected Soil Properties

Abstract

This research concerned the possibilities of the natural management of ash, which is a waste product obtained in the process of burning wood chips in a bio-heating plant. The basis of the research was a pot experiment, which was carried out in a greenhouse of the University of Warmia and Mazury in Olsztyn, Poland. This experiment dealt with the influence of increasing doses of wood biomass ash added to soil on selected soil properties. The soil used for the pot experiment was taken from the arable layer (0–25 cm) of the soil. It was characterized by acidic reaction, low salinity, and an average content of total carbon (TC). The test plant was corn. Soil analysis after plant harvest showed an increase in pH and a significant improvement of soil sorption properties, without causing an excessive increase in soil salinity. In addition, a significant increase in the content of available K, P, and Mg was observed, which at the highest dose of WBA reached: 121.9; 109.3, and 41.33 mg kg−1 of soil, respectively. The content of trace metals: iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), cadmium (Cd), lead (Pb), cobalt (Co), chrome (Cr), and nickel (Ni) in the soil was quite varied but did not exceed the permissible values for agricultural soils. The content of available forms of these trace metals at the highest dose of WBA was, respectively, 1004, 129.9, 8.70, 2.08, 5.54, 0.195, 1.47, 0.97, and 1.92 kg−1 of soil. The results confirmed the significant fertilizing potential of wood biomass ash.

Role of Woody Biomass Ash Material in Immobilization of Cadmium, Lead and Zinc in Soil

“…In turn, the share of Pb av in Pb tot occurred after the introduction of the highest BA dose (90 g pot −1 ), and the share of Zn av in Zn tot decreased significantly at the BA doses of 60 and 90 g pot −1 . The obtained results can be explained by the fact that BA application increased the soil reaction [4,8], and this results in the transformation of heavy metals, including Cd, Pb [31,32], and Zn [33] into unavailable (insoluble) forms. Moreover, the addition of BA increases soil porosity and aeration and thus improves the ability to conduct cation exchange and retain nutrients and water in soil [4].…”

“…Moreover, the addition of BA increases soil porosity and aeration and thus improves the ability to conduct cation exchange and retain nutrients and water in soil [4]. BA application increases the C tot content in the soil and increases CEC [8], which also promotes the immobilization of heavy metals in the soil [32,33]. Amendments that immobilize pollutants in the soil reduce the leaching of trace elements and, at the same time, their bioavailability [33,34].…”

“…If BA comes from a reliable source that guarantees a pure and homogeneous raw material, then it contains specific, stable amounts of minerals and trace elements [4]. Due to the abundance of BA in nutrients, including macroelements (Ca, K, Mg, P, Na) and microelements (Zn, Fe, Mn, Cu, B), the application of this material to the soil should be considered first, as it has been proven to have a positive effect on soil properties [4,8]. BA, characterized by a negligible level of xenobiotics, can be used as a substitute for lime in agriculture or for the reclamation of degraded land to improve soil properties.…”

“…There is relatively little information in the literature on the immobilization role of BA that these materials can play in relation to toxic substances contained in the soil. However, the potential of BA in improving soil properties associated with an increase in pH is quite well known [4,8], as it is able to increase the sorption complex [8] and increase retention in relation to nutrients [8,13,14] and water [4]. The above information provides the basis for indicating the possibility of immobilizing heavy metals in soils as a result of the soil application of BA.…”

“…Additionally, the storage of BA can in turn cause the migration of metals and other pollutants not only to soils but also to waters [6]. Due to the few mentions in the literature about the potential role of BA in Cd immobilization [8], the purpose of the research undertaken was to verify these few reports.…”