Chemical and structural analysis of enhanced biochars: Thermally treated mixtures of biochar, chicken litter, clay and minerals Y. Lin a , P. Munroe a,⇑ , S. Joseph a , A. Ziolkowski b , L. van Zwieten c , S. Kimber c , J. Rust c a School of Materials Science and Engineering, The University of New South Wales, Sydney, NSW 2052, Australia b School of Environmental and Life Sciences, The University of Newcastle, NSW 2258, Australia c Wollongbar Primary Industries Institute, 1243 Bruxner Highway, Wollongbar, NSW 2477, Australia highlights " Enhanced biochars were prepared based on torrefaction of biochar and mineral phases. " Torrefaction was effective in minimising nitrogen losses from feestocks. " Higher processing temperatures promoted enhanced dissolved organic carbon content. article info Article history: Received 24 August 2012 Received in revised form 21 November 2012 Accepted 23 November 2012 Available online 25 December 2012 Keywords: Biochar LC-OCD Dissolved organic carbon Chicken litter abstract In this study biochar mixtures comprising a Jarrah-based biochar, chicken litter (CL), clay and other min- erals were thermally treated, via torrefaction, at moderate temperatures (180 and 220 °C). The objectives of this treatment were to reduce N losses from CL during processing and to determine the effect of both the type of added clay and the torrefaction temperature on the structural and chemical properties of the final product, termed as an enhanced biochar (EB). Detailed characterisation indicated that the EBs con- tained high concentrations of plant available nutrients. Both the nutrient content and plant availability were affected by torrefaction temperature. The higher temperature (220 °C) promoted the greater decomposition of organic matter in the CL and dissociated labile carbon from the Jarrah-based biochar, which produced a higher concentration of dissolved organic carbon (DOC). This DOC may assist to solu- bilise mineral P, and may also react with both clay and minerals to block active sites for P adsorption. This subsequently resulted in higher concentrations of plant available P. Nitrogen loss was minimised, with up to 73% of the initial total N contained in the feedstock remaining in the final EB. However, N availability was affected by both torrefaction temperature and the nature of the clay minerals added. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction The poultry industry generates large volumes of chicken litter (CL). This is rich in plant nutrients, such as nitrogen and phosphorus, consequently CL has for some decades been applied to agricultural soils as an organic ffertilizer (Faridullah et al., 2008). However, direct land application of untreated CL to soil has many disadvantages, such as the environmental pollution caused by pathogens, ammonia emission, nitrate contamination of groundwater (Nahm, 2003), and soluble P contamination of surface water, especially when CL is over- applied (Faridullah et al., 2008). Composting CL with biomass, such as straw and sawdust, is increasingly considered to be an effective method for recycling surplus manure as a stabilised and sanitised end product, since this process can eliminate pathogens and weeds, reduces both volume and moisture and can generate higher quality fertilizers (Bernal et al., 2009). However, it was found (Ogunwande et al., 2008) that cumulative N loss was up to 71% of the initial total N under optimal conditions during composting, mainly due to vola- tilisation of ammonia. Nitrogen loss decreased both the fertilizer po- tential and economic value of the end product, while causing environmental pollution (Kithome et al., 1999; Bernal et al., 2009; Steiner et al., 2010). To reduce N loss and optimise the C/N ratio, biochar, as a bulking agent, has been used in the composting process (Steiner et al., 2010; Clough and Condron, 2010; Jindo et al., 2012). The total N losses were decreased to 40% (Steiner et al., 2010). However, composting is not always the optimum strategy to recycle organic material produced by animals. Further, this approach is still not widely accepted as a commercially viable process because the composting process is relatively time consuming (Shinogi et al., 2003; Jindo et al., 2012). 0045-6535/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.chemosphere.2012.11.063 ⇑ Corresponding author. E-mail address: p.munroe@unsw.edu.au (P. Munroe). Chemosphere 91 (2013) 35–40 Contents lists available at SciVerse ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere