Fate of nitrogen during composting of chicken litter S.M. Tiquia a, *, N.F.Y. Tam b a Department of Food, Agricultural, and Biological Engineering, Ohio Agricultural Research and Development Center (OARDC), The Ohio State University, 1680 Madison Avenue, Wooster, OH 44691, USA b Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, People's Republic of China Received 16 August 1999; accepted 19 August 1999 ``Capsule'': Composting reduced the value of chicken litter as a N fertilizer. Abstract Chicken litter (a mixture of chicken manure, wood shavings, waste feed, and feathers) was composted in forced-aeration piles to understand the changes and losses of nitrogen (N) during composting. During the composting process, the chemical [dierent N fractions, organic matter (OM), organic carbon (C), and C:N ratio], physical, and microbial properties of the chicken litter were examined. Cumulative losses and mass balances of N and organic matter were also quanti®ed to determine actual losses during composting. The changes in total N concentration of the chicken litter piles were essentially equal to those of the organic N. The inorganic N concentrations were low, and that organic N was the major nitrogenous constituent. The ammonium (NH 4 + )-N con- centration decreased dramatically during ®rst 35 days of composting. However, the rapid decrease in NH 4 + -N during composting did not coincide with a rapid increase in (NO 3  +NO 2  )-N concentration. The concentration of (NO 3  +NO 2  )-N was very low (<0.5 g kg 1 ) at day 0, and this level remained unchanged during the ®rst 35 days of composting suggesting that N was lost during composting. Losses of N in this composting process were governed mainly by volatilization of ammonia (NH 3 ) as the pile tem- peratures were high and the pH values were above 7. The narrow C:N ratio (<20:1) have also contributed to losses of N in the chicken litter. The OM and total organic C mass decreased with composting time. About 42 kg of the organic C was converted to CO 2 . On the other hand, 18 kg was lost during composting. This loss was more than half (59%) of the initial N mass of the piles. Such a ®nding demonstrates that composting reduced the value of the chicken litter as N fertilizer. However, the composted chicken contained a more humi®ed (stabilized) OM compared with the uncomposted chicken litter, which would enhance its value as a soil conditioner. # 2000 Elsevier Science Ltd. All rights reserved. Keywords: Composting; Nitrogen; Nitri®cation; Denitri®cation; Organic matter loss 1. Introduction Chicken litter is a mixture of excreta, wood shavings, wastes feed, and feathers which is removed from poul- try houses, and can be applied to soil as an amendment. Composting of this litter prior to application as a fertilizer is recommended to control the spread of pathogens, minimize the production of phytotoxic sub- stances, improve storage and handling, and reduce unpleasant odors (Edwards and Daniel, 1992; Hansen et al., 1993; Tiquia and Tam, 1998a). Composting is also an eective and inexpensive means of stabilizing organic matter (OM; Golueke, 1977). However, the composting changes the nature of the waste and can aect its usefulness as a soil amendment. For instance, composting may aect nitrogen (N) transformations such as N mineralization, ammonia (NH 3 ) volatiliza- tion, nitri®cation, and denitri®cation. N mineralization is of extreme importance because it converts organic N into ammonium (NH 4 + ). NH 3 volatilization and deni- tri®cation may lead to signi®cant losses of N (Martins and Dewes, 1992; Bernal et al., 1996). Such a loss will aect the agronomic quality of the composted product. These losses during composting of animal manure range from 21% upward to 77% (Martins and Dewes, 1992; Rao Bhamidimarri and Pandey, 1996). N losses vary depending on several environmental factors such as aeration, moisture content, and temperature (Bishop 0269-7491/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S0269-7491(99)00319-X Environmental Pollution 110 (2000) 535±541 www.elsevier.com/locate/envpol * Corresponding author. Tel.: +1-330-263-3866; fax: +1-330-263- 3634. E-mail address: tiquia.1@osu.edu (S.M. Tiquia).