Biochar Produced from Anaerobically Digested Fiber Reduces Phosphorus in Dairy Lagoons

Abstract

This study evaluated the use of biochar produced from anaerobic digester dairy fiber (ADF) to sequester phosphorus (P) from dairy lagoons. The ADF was collected from a plugged flow digester, air-dried to <8% water content, and pelletized. Biochar was produced by slow pyrolysis in a barrel retort. The potential of biochar to reduce P in the anaerobic digester effluent (ADE) was assessed in small-scale filter systems through which the effluent was circulated. Biochar sequestered an average of 381 mg L P from the ADE, and 4 g L ADF was captured as a coating on the biochar. There was an increase of total (1.9 g kg), Olsen (763 mg kg), and water-extractable P (914 mg kg) bound to the biochar after 15 d of filtration. This accounted for a recovery of 32% of the P in the ADE. The recovered P on the biochar was analyzed using P nuclear magnetic resonance for P speciation, which confirmed the recovery of inorganic orthophosphate after liquid extraction of the biochar and the presence of inextractable Ca-P in the solid state. The inorganic phosphate was sequestered on the biochar through physical and weak chemical bonding. Results indicate that biochar could be a beneficial component to P reduction in the dairy system.

Effectiveness of Biochar for Sorption of Ammonium and Phosphate from Dairy Effluent

“…In comparison, typically reported CEC values for soil components include <5 cmol c kg −1 for sand, <10 cmol c kg −1 for oxides, <15 cmol c kg −1 for Kaolinite, <150 cmol c kg −1 for smectite, and <250 cmol c kg −1 for bulk organic matter (OM) in soil (Brady and Weil 2008). Biochar has been reported to sorb dissolved ammonium (NH 4 + ) (Lehmann et al, 2002), nitrate (NO 3 − ) (Mizuta, 2004), phosphate (PO 4 3− ) (Beaton et al, 1960; Streubel et al, 2012), and other ionic solutes (Radovic, 2000) as well as hydrophobic organic pollutants (Accardi‐Dey and Gschwend, 2002; Gustafsson, 1997) from solution. Biochar derived from different biomass materials was shown to sorb phosphorus and nitrate from aqueous solutions (Emerson, 1921; Peech and English, 1943; Roller and McKaig, 1939; Sowden and Atkinson, 1949).…”

“…Studies have verified that biochar can act as an important carrier of organic pollutants (Chen et al, 2007) and heavy metals (Meena et al, 2005). Recent studies have also discussed the potential of biochar as a way of recovering nutrients from agricultural water such as dairy effluent (Streubel et al, 2012; Taghizadeh‐Toosi et al, 2012b). The term recovery is used here because the ultimate goal is to use biochar to sorb some of the nutrients from dairy effluent and apply the nutrient‐enriched biochar as a soil fertilizer.…”

Removal of nitrate, ammonia and phosphate from aqueous solutions in packed bed filter using biochar augmented sand media

“…A number of researchers reported that biochar had little capacity for PO4 3-removal [6,12]. On the other hand, others reported that biochar has the capacity to remove or enhance phosphorus removal [4,5,7,13]. The apparently conflicting findings can be explained by the fact that the characteristics of biochar depend on the parent biomass and preparation conditions which affect their adsorption capacity of different chemicals [9,14].…”

Animal Manure Residue Upgrading and Nutrient Recovery in Biofertilisers

“…Streubel et al (2012) demonstrated that biochar produced from anaerobic digester dairy solid fraction could be used to sequester P from dairy lagoons, through physical and weak chemical bonding, indicating that biochar could be a beneficial component to P reduction in dairy production systems. Biochar could also be blended with compost (Steiner et al, 2010) in order to retain NH 4 + and prevent NH 3 volatilisation, which could increase the value of the biochar once the compost is applied to soil.…”