Journal of Hazardous Materials A138 (2006) 211–217 Olive pulp and its effluents suitability for soil amendment A. Nastri, N.A. Ramieri, R. Abdayem, R. Piccaglia, C. Marzadori, C. Ciavatta ∗ Dipartimento di Scienze e Tecnologie Agroambientali, Alma Mater Studiorum, Universit` a di Bologna, Viale G. Fanin 40, I-40127 Bologna, Italy Received 18 October 2005; received in revised form 3 May 2006; accepted 4 May 2006 Available online 15 June 2006 Abstract Olive pulp (OP) and its effluents produced after digestion processes were characterised and their suitability as soil amendment materials were investigated. Results showed that OP and its effluent for hydrogen (EH 2 ) and methane production (ECH 4 ) contain high amount of organic matter, remarkable concentration of nutrients and negligible content of heavy metals. Decreasing concentrations of low molecular weight phenols (monomeric phenols) and increasing amount of humic-like materials were found passing from OP to EH 2 and ECH 4 . The effects on both wheat seed germination and seedlings growth were also investigated. Addition of OP at the highest doses delayed both seed germination and seedling growth. These effects decreased when the OP and its effluents were incorporated into the soil. On the contrary an enhancement of seedlings growth was detected by addition of EH 2 and ECH 4 . Enhancement effects also were found out by addition of lower OP concentrations. The phytotoxic effects decreased when the products were incorporated into the soil. © 2006 Elsevier B.V. All rights reserved. Keywords: Olive pulp; Phenolic compounds; Physicochemical characterisation; Seed germination; Wheat seedling growth 1. Introduction The olive oil industry is extremely important from an envi- ronmental sustainability point of view because of the significant amount of wastes produced that lead to economic, technical and organisational constraints in the adoption of an environmentally sustainable disposal [1–3].The technology for olive oil extrac- tion has progressed significantly since the beginning of the 1970, when the three-phase centrifugation system appeared. It sepa- rates the oil from an aqueous phase (olive mill wastewater) and a solid phase (olive husk) in a continuous process. The main inconvenience of this system is a large production of wastew- aters characterised by a heavy pollutant load [2–5]. Numerous attempts have been made in order to reduce their environmental impact, such as treating them physically, chemically and biologi- cally or applying them directly to soils; nevertheless the disposal of wastewaters continues to be a very difficult process [4]. In the 1990, the olive oil industry has adopted a new con- tinuous centrifugation system with a two-phase decanter, which separates the oil from a solid humid by-product called olive pulp (OP), constituted by variable quantities of olive pulp, stones, ∗ Corresponding author. Tel.: +39 051 2096201; fax: +39 051 2096203. E-mail address: claudio.ciavatta@unibo.it (C. Ciavatta). residual oil and vegetative waters [6,9]. Even though the direct application of OP onto land is an inexpensive way of disposing and recycling nutrients and organic matter, it might be a source of pollution and could have an unfavourable environment impact. Many studies have reported the toxic effects of oil by-products on plants and soil microbial activity, because of their content of monomeric phenolics, fatty acids and mineral salts [5–12]. An interesting alternative for a sustainable disposal of OP is its use in energy recovery. It is a good potential energy source because of its high polysaccharide content and can produce ethanol, hydrogen and methane through aerobic and anaerobic digestion [13]. However, only when the by-products remaining at the end of the digestion processes are eliminated might their use in agriculture as amendments be feasible. The aim of this research, within the UE BIOTROLL 1 Project, was the chemical characterisation of olive pulp (OP) and the effluents arising from its anaerobic digestions for the produc- tion of hydrogen (EH 2 ) and methane (ECH 4 ) and to assess their effect on the germination and the early stages of wheat 1 Research funded by the European Commission (FP5, Quality of life and management of living resources—key action 5), Contract no. QLK5-CT-2002- 02344—integrated biological treatment and agricultural reuse of olive mill effluents with the concurrent recovery of energy sources (BIOTROLL). 0304-3894/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2006.05.108