title: Nitrogen enrichment potential of biochar in relation to pyrolysis temperature and feedstock quality.
abstract: Nitrogen (N) enrichment of biochar from both inorganic and organic waste N sources has the potential to add economic and environmental value through its use as a slow release N fertilizer. We investigated the sorption of N by, and its release from, biochar made at pyrolysis temperatures of 400, 500 and 600 °C from three feedstocks: poultry litter (PL with a carbon (C) to N ratio (C:N) of 14), softwood chips of spruce-pine-fir (SPF with a C:N of 470), and a 50:50 mixture of PL and SPF (PL/SPF). The prepared biochars were enriched with ammonium nitrate (AN) and urea ammonium nitrate (UAN). PL biochars had the lowest C content (50-56% C), but the highest pH (9.3-9.9), electrical conductivity (EC, 780-960 dS m(-1)), cation exchange capacity (CEC, 40-46 cmol kg(-1)), and N content (3.3-4.5%). While N content and hydrogen (H) to C atomic ratio (H:C) decreased with increasing pyrolysis temperature irrespective of the feedstock used, both pH and EC slightly increased with pyrolysis temperature for all feedstocks. The PL and SPF biochars showed similar H:C and also similar N sorption and N release at all pyrolysis temperatures. These biochars sorbed up to 5% N by mass, irrespective of the source of N. However, PL/SPF biochar performed poorly in sorbing N from either AN or UAN. Biochar H:C was found to be unrelated to N sorption rates, suggesting that physical adsorption on active surfaces was the main mechanism of N sorption in these biochars. There were minor differences between N sorbed from NO3-N and NH4-N among different biochars. Very small amounts of sorbed N (0.2-0.4 mg N g(-1) biochar) was released when extracted with 1 M KCl solution, indicating that the retained N was strongly held in complex bonds, more so for NH4-N because the release of NO3-N was 3-4 times greater than that of NH4-N. NH4-N sorption far exceeded the effective CEC of the biochars, thereby suggesting that most of the sorption may be due to physical entrapment of NH4(+) in biochar pores. The results of this study suggest that biochar can be used to remove excess N from poultry and dairy manure and be a good mitigation option for reducing N leaching and gaseous losses.
authors.affiliation: Faculty of Land and Food Systems, University of British Columbia, Vancouver, Canada. Electronic address: rachhpal.jassal@ubc.ca.
authors.forename: Rachhpal S
authors.initials: RS
authors.lastname: Jassal
authors.affiliation: Institute for Resources, Environment and Sustainability, University of British Columbia, Vancouver, Canada; Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, Canada.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Johnson
authors.affiliation: Institute for Resources, Environment and Sustainability, University of British Columbia, Vancouver, Canada.
authors.forename: Marina
authors.initials: M
authors.lastname: Molodovskaya
authors.affiliation: Faculty of Land and Food Systems, University of British Columbia, Vancouver, Canada.
authors.forename: T Andrew
authors.initials: TA
authors.lastname: Black
authors.affiliation: Institute for Resources, Environment and Sustainability, University of British Columbia, Vancouver, Canada.
authors.forename: Ashlee
authors.initials: A
authors.lastname: Jollymore
authors.affiliation: Department of Chemistry, Langara College, Vancouver, Canada.
authors.forename: Kelly
authors.initials: K
authors.lastname: Sveinson
mesh_terms: D000327:Adsorption; D000818:Animals; D018533:Biomass; D002244:Carbon / Q000032:analysis; D002606:Charcoal / Q000737:chemistry*; D004785:Environmental Pollutants / Q000737:chemistry*; D004787:Environmental Pollution / Q000517:prevention & control*; D052918:Environmental Restoration and Remediation / Q000379:methods*; D005308:Fertilizers / Q000032:analysis; D006358:Hot Temperature; D008372:Manure / Q000032:analysis; D009566:Nitrates / Q000737:chemistry; D009584:Nitrogen / Q000737:chemistry*; D011200:Poultry; D014508:Urea / Q000737:chemistry; D014934:Wood / Q000737:chemistry
chemical_list: D004785:Environmental Pollutants; D005308:Fertilizers; D008372:Manure; D009566:Nitrates; C540010:biochar; D002606:Charcoal; D002244:Carbon; D014508:Urea; D009584:Nitrogen; C006568:ammonium nitrate
keywords: Cation exchange capacity; Nitrogen enriched biochar; Nitrogen release; Nitrogen sorption; Organic wastes; Poultry litter; Slow release N carriers