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BIOTROLL
Integrated biological treatment and agricultural re-use of olive mill effluents with the concurrent recovery of energy sources

The olive pulp generated during the two-phase processing of olive oil contains almost 80% (per dry weight) carbohydrates and, thus, could be an ideal substrate for the production of energy in the form of ethanol, hydrogen and biogas (methane). Very limited research has so far been conducted into making value out of this waste. This project will analyse the whole process to find the optimal combination of the different treatment steps that would be most favourable from both an environmental and financial point of view.

Objectives
The objectives of the BIOTROLL project are:
1) to investigate the possibility of biologically producing ethanol from olive pulp
2) to investigate the possibility of biologically producing hydrogen from olive pulp
3) to stabilise the olive pulp and pre-treated olive pulp coming from the ethanol and hydrogen production processes
4) to study and evaluate the recycling of olive pulp and the three types of pre-treated olive pulp resulting from ethanol production, hydrogen production and anaerobic digestion
5) to optimise the different biological processes for the production of ethanol, hydrogen and methane
6) to analyse the optimal process design (combination of the different biological processes) for the recovery of bioenergy sources (ethanol, hydrogen and methane), and the generation of high-quality stabilised effluent with value as a fertiliser and/or soil conditioner.

Progress to Date
The chemical characterisation of the olive pulp and the start-up of laboratory scale bioreactors are currently under way.
Characterisation of the olive pulp has been completed. The use of olive pulp as a potential substrate in the production of bioethanol was pursued applying different means of pre-treatment. The philosophy of the approach was to apply increased severities of treatment prior to fermentations into bioethanol. The conditions assessed were: no pre-treatment and alkaline wet oxidation pre-treatment prior to enzymatic hydrolysis. Evaluation of the potential for bioethanol production was based on: a) the recovery of the different carbohydrates, b) the enzymatic convertibility of the polymeric carbohydrates, and c) the ability of the fermenting microorganisms to produce ethanol from the carbohydrates contained in the olive pulp. The utilization of the raw olive pulp as a potential substrate in production of biohydrogen was investigated by pure extremophilic (70C) bacterial strains and mixed thermophilic (55C) and mesophilic (35C) microbial cultures. Enzymatic pre-treatment of the olive pulp prior the extremophilic fermentation and simultaneous enzymatic hydrolysis with the thermophilic mixed microbial fermentation were tested as well as a way to enhance hydrogen production since wet oxidised olive pulp was found to be inhibitory for the microbial growth on the one hand and free sugars-consuming on the other. Adaptation of mesophilic (35C) and thermophilic (50C) anaerobic mixed cultures to the raw olive pulp and to the pre-treated olive pulp from hydrogen production has been completed. Also adaptation of mesophilic anaerobic mixed culture to the pre-treated (for mesophilic hydrogen production) olive pulp has been started. The anaerobic digestibility and methane potential of raw olive pulp and of effluent from hydrogen production has been assessed performing batch tests. Effluents from the biological treatment of olive pulp for production of hydrogen and methane were characterized chemically and physically. Studies of the suitability of the raw olive pulp and effluents from its anaerobic treatments for hydrogen (EH2) and methane (ECH4) production as fertiliser or soil improving agent were performed by performing plant toxicity tests where the effects of increasing doses of OP, EH2 and ECH4 on the seed germination and on the early stages of plant development were evaluated. Furthermore, an extended literature review has been made concerning the existing mathematical models of the various treatment methods for olive pulp and the formulation of simplified models of the processes performed in various types of bioreactors. The expected detailed kinetic models will be integrated into the reactor models for subsequent simulation studies. Also, efforts have so far been largely devoted on the development of the Life Cycle Analysis methodology in relation to the mathematical models. Suitable environment performance objectives have identified for the olive pulp treatment system, which can be used to guide the decision-making during the Methodology for Environmental Impact Minimisation. The problem formulation of the Life Cycle Analysis has also contributed towards the inclusion of both global supply chain and plant-wide considerations.

Classified in FRUIT, SOIL, NON-FOOD PRODUCTS

Scientist responsible for the project

Professor BIRGITTE AHRING
Anker Engelundsvej 1
2800 Lyngby
Denmark - DK

Phone: +45 45256183
Fax: +45 45883276
E-mail: bka@biocentrum.dtu.dk

References

Project ID QLRT-2001-02344
Organisation TECHNICAL UNIVERSITY OF DENMARK
Area 5.1.1
Start date 01 February 2003
Duration (months) 36
Total cost 1 658 117 €
Total EC contribution   1 549 994 €
Status Ongoing

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