ARS | Publication request: Use of Biochar to sequester nutrients from dairy manure lagoons

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 12, 2010
Publication Date: N/A

Technical Abstract: We are developing technology to utilize dairy waste as an alternative energy and fertilizer source. The fiber component exiting a GHD™ Plugged Flow anaerobic digester as well as feedstocks from softwood sources were used to produce bio-gas or bio-oil under low temperature pyrolysis, the co-product, biochar was applied to dairy waste water to remove the nutrients nitrogen and phosphorus. Biochars made from the dairy AD fiber and softwood pellet feedstocks were evaluated for their potential to sorb P from a KH2PO4 standard and anaerobic digested dairy effluent (ADE). The P concentrations of the phosphate standard were 55 mg PO4 L-1 and 28 mg PO4 L-1; and ADE 80 mg PO4 L-1 and 40 mg PO4 L-1 respectively. Nearly all (52 mg PO4 L-1 and 27 mg PO4 L-1) of the P from the KH2PO4 standards were found in the filtrate after a 48 h incubation, with < 3 mg PO4 L-1 sorbed by either of the chars. This indicates that these biochars had a minimal exchange capacity to sorb soluble PO4. In contrast, the biochars amended with ADE sorbed nearly all of the P present in the ADE subsample, with only 2 mg PO4 L-1 of the initial 81 mg PO4 L-1 added to the chars found in the filtrate. Olsen P concentrations extracted were approximately10 times higher in the ADE amended biochars than those amended with the P-standard. Olsen P extracts represent the amount of P that will be available to plants over a growing season. Of the initial P in the ADE added to the char, ~20 mg PO4 L-1 was in the form of Olsen extractable P. We hypothesize that the remaining 60 mg PO4 L-1 is in an organic form and bound to the char as a coating rather than anion sorption to an exchange complex.