Wood and Combination Wood‐Fired Boiler Ash Characterization

Abstract

Ashes resulting from the combustion of wood residues in industrial boilers are characterized relative to (i) macroelement compositions, (ii) trace and heavy metal microelement compositions, (iii) organics, and (iv) polychlorinated dibenzo‐dioxins and ‐furans (PCDD/Fs). Ash compositions, both macro‐ and microelements, are compared with coal ash and limestone. Microelements in wood ashes are also compared with other potential soil amendments such as pulp mill sludges. The impact of burning sludge and combinations of coal and wood residue on ash metal concentrations is presented. Levels of PCDD/Fs in ash resulting from combustion of 100% inland wood residue, salty wood, or bleached mill sludge with wood residue are reviewed, as are the levels of PCDD/Fs in ashes and soot resulting from residential wood combustion. The concentrations of metals in wood ash are comparable to other potential soil amendments. The concentration in wood ash of common organics of environmental concern appears to be negligible. The levels of PCDD/Fs in the ash appear to have a direct correlation with extraneous sources of chloride in the wood fuel.

A Blend of Bioash and Gypsum Utilized for Agro-Environmental Purposes in a Soil Incubation Experiment

“…According to the analyses of several bioashes with different origins the highest mean concentration among microelements was that of Mn (4370 mg/kg), followed by Zn (443 mg/kg), Cu (75 mg/kg), B (110 mg/kg), and Mo (15 mg/kg). Concentration of As, Ni, Cr and Pb varied between 23 and 65 mg/kg, whereas regarding non-essential trace elements the concentrations of Se and Hg (< 0,5 mg/kg), as well as Cd and Co (< 10 mg/kg) proved to be low (Someshwar, 1996).…”

Runoff characteristics in forest plots before and after wood ash fertilization

“…Someshwar (1996) estimated a production of wood ash of about 1.5-3 million tons/year in the USA, originated from the combustion of wood and coal in forest industries. It is also estimated that more than 80% of this residue is land filled without another solution (Campbell 1990).…”

“…However, wood ashes always show high alkalinity -with pH values above 10 in most of the cases - (Demeyer et al 2001, Someshwar 1996, and high levels of Ca and K, and occasionally Mg, in form of oxides, hydroxides and carbonates (Campbell 1990). Elements such as C and N can be present if combustion was not complete, or be volatilised otherwise (Someshwar 1996, Muse andMitchell 1995).…”

“…Elements such as C and N can be present if combustion was not complete, or be volatilised otherwise (Someshwar 1996, Muse andMitchell 1995). Si and Al may appear if sand is adhered to the wood during tree falling operations (Someshwar 1996). Microelement concentrations are very variable, Fe being the most abundant (Someshwar 1996, Ohno 1992, Ohno and Erich, 1990.…”

“…Si and Al may appear if sand is adhered to the wood during tree falling operations (Someshwar 1996). Microelement concentrations are very variable, Fe being the most abundant (Someshwar 1996, Ohno 1992, Ohno and Erich, 1990. According to Someshwar (1996) these ashes have low or very low Se, Hg, Cd and Co contents, and may have high As, Ni, Cr, Pb, B and Mn concentrations.…”