Gas emissions during olive mill waste composting under static pile conditions L. Nasini a, 1 , G. De Luca b, 1 , A. Ricci c, 1 , F. Ortolani b , A. Caselli b , L. Massaccesi a , L. Regni a , G. Gigliotti c, * , P. Proietti a a Department of Agricultural, Food and Environmental Science, University of Perugia, Borgo XX Giugno, 74 e 06121, Perugia, Italy b Regional Environmental Protection Agency (ARPA) Umbria, Industrial Emission Control Service, Via Carlo Alberto Dalla Chiesa, 32 - 05100, Terni, Italy c Department of Civil and Environmental Engineering, University of Perugia, Borgo XX Giugno, 74 e 06121, Perugia, Italy article info Article history: Received 16 September 2015 Received in revised form 2 November 2015 Accepted 2 November 2015 Available online xxx Keywords: Composting Gas emissions Olive mill waste Compost quality abstract This study evaluated gas emissions and chemical parameters during olive mill waste and grape stalk composting for three consecutive years. Each year, a static pile was built, and gas emissions were measured by a stationary chamber custom built for this purpose. The instrument indicated a CO 2 con- centration that was always higher (ranging from 0.33 to 3.33%) in comparison to nearby atmospheric levels the trails, a high rate of NO x at the beginning of each trial (4.4, 5.9 and 3.9 mg Nm 3 in the first, second and third year, respectively) and limited emissions of aldehydes, ammonia, aliphatic amine and VOCs from the composting piles. The TOC concentration decreased by approximately 28% because of the oxidative phenomena typical of the aerobic process. The total N concentration increased slightly (by approximately 24%) during the process. The germination index reached 100% in the three piles, demonstrating the efficiency of the process both in terms of stability and maturity. The overall results indicate that composting the by-products from olive oil extraction and grape transformation leads to the production of a high quality soil organic amendment, even if the environmental impact due to gas emissions must be considered. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction The problem of the olive mill waste (OMW) management con- cerns all countries that produce olive oil. The difficulties of OMW disposal are worsened by its short production time, which spans only four to five months, and by the presence of slow-degrading organic compounds (Altieri and Esposito, 2010). Although Italian law permits and regulates spreading OMW on agricultural soil, this practice is usually difficult and expensive (Altieri and Esposito, 2010). Moreover, the direct agricultural use of OMW can have a negative effect on the environment and crops for its content of potentially phytotoxic, bacteriostatic compounds and a high amount of salts (Gigliotti et al., 2012; Nasini et al., 2013). Many other strategies have been proposed, including composting, which is widely recognised as an eco-sustainable process to reuse organic waste such as OMW (Paredes et al., 2005; Altieri and Esposito, 2010). This practice permits to degrade the toxic compounds pre- sent in the water-soluble organic matter, decreasing the phyto- toxicity of raw materials (Gigliotti et al., 2012). The OMW-derived compost can be used as a soil organic amendment for crops (Alburquerque et al., 2007; Altieri and Esposito, 2008) and as a growing substrate in plant nurseries as a partial or total substitute for peat. Most composting studies have aimed to determine the quality of compost and/or to improve the process, but few studies have considered the environmental impact of composting (Lou and Nair, 2009). In relation to gas emissions, composting not only produces CO 2 and aqueous vapour but also releases smaller quantities of other gases, such as NH 3 , CO, CH 4 ,N 2 O, H 2 S, NO x and volatile organic compounds (VOCs), each with a different impact on air quality * Corresponding author. Permanent address: Department of Civil and Environ- mental Engineering, University of Perugia, Borgo XX Giugno, 74 e 06121, Perugia, Italy. E-mail addresses: agr.nasini@gmail.com (L. Nasini), g.deluca@arpa.umbria.it (G. De Luca), annaricci83@libero.it (A. Ricci), f.ortolani@arpa.umbria.it (F. Ortolani), a.caselli@arpa.umbria.it (A. Caselli), luisa.massaccesi@gmail.com (L. Massaccesi), regni.luca.agr@gmail.com (L. Regni), giovanni.gigliotti@unipg.it (G. Gigliotti), primo.proietti@unipg.it (P. Proietti). 1 These authors contributed equally to the study. Contents lists available at ScienceDirect International Biodeterioration & Biodegradation journal homepage: www.elsevier.com/locate/ibiod http://dx.doi.org/10.1016/j.ibiod.2015.11.001 0964-8305/© 2015 Elsevier Ltd. All rights reserved. International Biodeterioration & Biodegradation 107 (2016) 70e76