title: Effects of solid-liquid separation on recovering residual methane and nitrogen from digested dairy cow manure.
abstract: The feasibility of optimizing methane and nitrogen recovery of samples obtained from farm biogas digester (35 degrees C) and post-storage tank (where digested material is stored for 9-12 months) was studied by separating the materials into different fractions using 2, 1, 0.5 and 0.25 mm sieves. Mass-balances revealed that digested material mainly consists of <0.25 mm (60-69%) and >2 mm (18-27%) fractions, while fractions between 2 and 0.2 mm made the rest. Incubation of solid fractions >0.25 mm of digester material at 35 degrees C resulted in specific methane yields of 0.060-0.085 m(3)kg(-1) volatile solids (VS) during initial 30-50 d and 0.16-0.18 m(3)kg(-1)VS at the end of 340 d incubation. Similarly, fractions >0.25 mm of post-storage tank material produced 0.055-0.092 m(3)kg(-1)VS and 0.13-0.16 m(3)kg(-1)VS of methane after 30-50 d and after 250 d, respectively. Methane yields for fractions <0.25 mm of post-storage tank was 0.03 m(3)kg(-1)VS after 30-50 d and 0.05 m(3)kg(-1)VS after 250 d compared to 0.20 m(3)kg(-1)VS and 0.41 m(3)kg(-1)VS, respectively for the same fraction of digester material. Separation of digested cow manure into solids and liquid fractions to recover methane may be feasible only for post-storage tank material and not for digester material. Nitrogen management would not be feasible with neither material as total nitrogen and ammonium-nitrogen concentrations were equally distributed among the segregated fractions.
authors.affiliation: Department of Biological and Environmental Science, University of Jyväskylä, FIN-40014, Finland. plk@er.dtu.dk
authors.forename: P L N
authors.initials: PL
authors.lastname: Kaparaju
authors.forename: J A
authors.initials: JA
authors.lastname: Rintala
mesh_terms: D000818:Animals; D001673:Biodegradation, Environmental; D019149:Bioreactors; D002417:Cattle; D005591:Chemical Fractionation; D003612:Dairying; D005240:Feasibility Studies; D005260:Female; D005285:Fermentation; D008372:Manure; D008697:Methane / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry*; D012037:Refuse Disposal / Q000379:methods*
chemical_list: D008372:Manure; D009584:Nitrogen; D008697:Methane