Using a chelating agent to generate low ash bioenergy feedstock

Abstract

Inorganic elements present in lignocellulosic biomass and introduced during harvesting and handling of the feedstock negatively affect biomass conversion to fuels and products. In particular, alkali and alkaline earth metals act as catalysts during thermochemical conversion, contribute to reactor degradation, and decrease the yield and quality of the reaction products. In this study, we investigated an approach to reduce ash content of switchgrass. Several reagents (chelating agents ethylenediaminetetraacetic acid (EDTA) and citric acid, as well as acetic acid, sulfuric acid, and water) under various extraction times (5, 10, 15, and 20 min) were tested using a microwave-assisted extraction method. After the extraction, mass loss, total ash, individual inorganics, and concentration of sugars in the hydrolyzates were measured. EDTA afforded the highest inorganics removal, with near complete extraction of alkali and alkaline earth metals K, Ca, and Mg, and high removal of S and Si. Citric acid and sulfuric acid removed similarly high amounts of K, Ca, and Mg as EDTA, but less Mg, P, S, and Fe. Additionally, extraction with water resulted in near complete removal of K; however, more modest removal of other inorganics was observed compared to other treatments. The mass loss was significantly higher in the sulfuric acid extractions due to hydrolysis of the structural carbohydrates, while EDTA resulted in little carbohydrate degradation due to the more neutral pH conditions. This study illustrated the benefits of extracting with chelating agents, as opposed to mineral acids, to remove inorganics and improve biomass quality.

Environmentally Friendly Process for Recovery of Wood Preservative from Used Copper Naphthenate-Treated Railroad Ties

“…This supports the replacement of EDTA with the more environmentally friendly chelating agents PDA and HEDP for removal of copper and biomass inherent inorganics. Additionally, it is noteworthy to point out that both potassium and sodium are completely extracted from the ties using only water, which is consistent with what has been reported in the literature . With all chelating agents, as well as with water, extraction efficiency significantly decreases with increasing thermal desorption severity.…”

“…Although thermal treatment is an effective method for recovery of the organic fraction of wood preservatives, CN contains an additional inorganic fraction not found in creosote that remains in the biomass after desorption. Many inorganics such as alkali and alkaline earth metals in particular have been reported to possess undesired catalytic effects on thermochemical conversion processes such as pyrolysis. − The presence of copper and these other metals leads to a decrease in yield and intensification of physical and chemical issues such as slagging, clogging, and degradation of reactor walls from corrosion and deactivation of catalysts . Chelating agents are often used as an extraction method for the removal of inorganics from biomass, including those that have these detrimental effects.…”

“…12−14 The presence of copper and these other metals leads to a decrease in yield and intensification of physical and chemical issues such as slagging, clogging, and degradation of reactor walls from corrosion and deactivation of catalysts. 14 Chelating agents are often used as an extraction method for the removal of inorganics from biomass, including those that have these detrimental effects. One of the most common of these chelating agents is ethylenediaminetetraacetic acid (EDTA), which has shown high efficiency in heavy metal removal from preservative-treated wood.…”

Treatment of Cattle Manure by Anaerobic Co-Digestion with Food Waste and Pig Manure: Methane Yield and Synergistic Effect

“…Lignocellulosic biomass is a complex mixture of organic (cellulose, hemicellulose, lignin, etc.) and inorganic (ash) substances, and an increase in the number of fibrous compounds can lead to an increase in ash content [ 21 ]. Additionally, the application of hydrated lime to cattle bedding for disinfection purposes (personal communication with the farm owners) appears to have contributed to the high fixed solids content of CM.…”

Improving the Quality of Crop Residues by the Reduction of Ash Content and Inorganic Constituents

“…(without degrading hemicellulose, cellulose, and lignin). For instance, Edmunds et al (2017) found that ethylenediaminetetraacetic acid (EDTA) nearly completed extraction of alkali and alkaline earth metals such as K, Ca, and Mg, and high removal of S and Si of switchgrass by using a microwave-assisted extraction method. Besides, nitrilotriacetic acid (NTA) and ethylenediiminopropanedioic acid (EDDM) are biodegradable comparing to EDTA.…”