Production of biochar from olive mill waste and remediation of heavy metal contaminated soil

Place: Bari, italy, Europe
Sustainable management of natural resources Sustainable management of natural resources
Total Budget: € 0,00 | Period: From January 2011 To March 2014


Solid Olive mill waste (pomace) is an abundant biomass of high environmental polluting impact in the Mediterranean region. Biochar production through slow pyrolysis was revealed to be an interesting tool to transform this waste rather than leaving it for natural decay or spreading it as fertilizer in agricultural soils which causes a significant environmental deterioration leading to soil, air and ground water pollution. Converting it into biochar through slow pyrolysis, characterizing it and testing its potential uses was considered. Biochar amendment showed promising results in reducing the tomato absorption of Ni, improving its growth, reducing metal content in the plants’ tissues, its uptake and translocation from the roots to the shoots indicating an immobilization effect. On a multi-contaminated soil (Cu, Pb, Zn), biochar amendment resulted in metals sequestration allowing better plants growth, higher protein content and an improved soil habitat for bacteria and earthworms.  


Parthenope University of Naples - Italy

Lead applicant

Hasselt University - Belgium

Initiative partner

Hasselt University is an independent innovative university which is regionally anchored and has a pronounced international orientation. The university stands for excellence in education, top research in spearhead fields and active engagement in innovation and entrepreneurship. The overall objective is to combine academic excellence with economic and social relevance. The university aims to widen participation, addressing all talents, and inspires its students and staff to develop their full potential in a dynamic environment. Hasselt University targets students with attractive undergraduate, graduate and PhD programmes which are research-led and characterised by a high academic level and the integration of lifelong employability skills. The programmes are supported by a range of innovative and effective teaching and learning forms.

Mediterranean Agronomic Institute of Bari - Italy

Initiative partner

L'Istituto Agronomico Mediterraneo di Bari-IAMB è la struttura operativa italiana del CIHEAM, istituito con Legge 932/1965 ed opera in 4 aree tematiche: - Gestione del suolo e delle risorse idriche; - Protezione integrata delle colture frutticole mediterranee; - Agricoltura biologica mediterranea; - Agricoltura, alimentazione e sviluppo rurale sostenibili. La formazione continua prevede corsi di aggiornamento anche a distanza rivolti a giovani dell’Area Mediterranea, Balcanica e del Vicino Oriente. L’Istituto svolge inoltre attività di ricerca applicata per migliorare la qualità della formazione con il coinvolgimento diretto dei corsisti nella ricerca e garantire un valido supporto alla progettazione e realizzazione di iniziative di partenariato. L’IAMB assiste le istituzioni, sia a livello centrale sia locale, per l’identificazione, la formulazione e l’esecuzione di progetti di cooperazione nei Paesi mediterranei al fine di promuovere la sicurezza alimentare e lo sviluppo sostenibile.

The best practice is framed within a PhD research work in Environment, resources and sustainable development and in Biology. The olive mill waste treatment using pyrolysis to produce biochar can be a valuable tool for the management and the neutralization of its phyto-toxic effects. The output product (biochar) can be used as soil amendment in marginalized land and contaminated soils TO SEQUESTER METALS, To restore soils and TO IMPROVE THEIR FERTILITY. Enhancing such efficient in-situ remediation with biochar is a promising way that will notably revalorize the marginalized and abounded lands to be re-used in agricultural to counter the challenges of the increasing world population and its nutrition.

The main innovation of this initiative is to explore the possibility of transforming the olive pomace into useful output product. Pyrolysis used as a transformation technology of the waste into biochar was revealed to be a valuable tool by reducing considerabley the amount of waste and producing an interesting carbon stable biochar. The possible use of biochar derived from olive mill waste as soil amendment was investigated for the aim of reducing mobility, bioavailability and toxicity of the metals in a soil. Consequently, marginalized and abounded soils, contaminated lands surrounding factories and smelter zones can be amended with biochar, to improve soil chemical and biological quality, to ameliorate the overall ecosystems and to enhance plant establishment and re-vegetation. 

Olive pomace pyrolysis A snapshot of the pyrolyser and the biochar output product

The olive oil industry is one of the most heavily polluting ones. Olive-mill waste, the byproduct of the olive oil production causes relevant environmental problems. The treatment of such residues, characterized by high content in organic matter, mainly phenolic compounds, and high salt concentration, is limited by technical and economical constraints and by the scattered pattern of olive mills location in the concerned regions. Pyrolysis might offer efficient recycle of this phyto-toxic biomass. This biomass conversion technology represents a valuable tool to
(1) Manage the olive mill solid waste, reducing its impact on the environment;
(2) Produce biochar which sequester relevant quantity of C;
(3) reduce the emission of greenhouse gases;
(4) Produce a soil amendment in the aim of improving soil physical chemical and biological properties and can be used in the remediation of heavy metal contaminated soils.

Main results achieved:
- Slow pyrolysis reduced considerably the volume and weight of the toxic olive mill waste.
- The produced biochar incorporated in a multi-metal contaminated soil reduced total and exchangeable metals.
-Common beans grew better in biochar-amended soil and displayed lower shoot and root metal concentrations. Based on morphological parameters and stress enzymes capacities in beans leaves and roots, phytotoxicity index indicated a shift from slightly toxic to non-toxic soil.
-Microbial communities had higher activity, higher richness and more diversity in biochar-amended soil indicating biochar efficiency in sequestering the metals and restoring soil microbial life. Biochar application was efficient in total suppression of earthworms mortality, improved their growth and their reproduction capacity indicating a better habitat.
- Improved soil chemical and biological quality ameliorating the overall ecosystem allowing plant establishment and re-vegetation. 

Bean plants after growing for 15 days (30 days equilibration) Bean plants after growing for 15 days on a metal contaminated soil amended with increasing concentrations of biochar and equilibrated for 30 days
Bean plants after growing for 15 days (90 days equilibration) Bean plants after growing for 15 days on a metal contaminated soil amended with increasing concentrations of biochar and equilibrated for 90 days
Biolog plates: indicator of Microbial activity Biochar amendment improved considerabley the soil microbial activity. The higher rate and the longer periode the biochar was stabilized in soil the higher was the microbial activity.

Ecological restoration of contaminated soils is an important topic with international-wide interest. The results of this research work are relevant, not only for future environmental applications at full scale, but also for scientific knowledge. This work can be considered as a contribution to enhance the ecological restoration and phyto-management of metal-contaminated soils in line with the reuse of organic wastes.
The outcome of this research work can be of high interest for the olive oil industry as it gives a suitable tool to manage its wastes. The interest can be addressed also from farmers, ecologists, environmentalists and decision makers since contaminated soils can be rehabilitated and revalorized, ecological status and ecosystem can be ameliorated and protected and greener eco-friendly technologies can be used.    

This research work brought three academic and research bodies to cope together to achieve the fixed objectives. Professors, Researchers and Students from Parthenope University (Naples, Italy), Uhasselt (Hasselt, Belgium) and the Mediterranean Agronomic Institute of Bari (Italy) were involved at different levels in different steps of the research work. 

The main human ressources involved can be resumed in : 

  • Amine Hmid: PhD in Biology and in Environment, Resources and Sustainable Development (MAIB, UniParthenope, Uhasselt)
  • Prof. Stefano Dumontet : Full Professor, University Parthenope, Naples, Italy. 
  • Prof. Jaco Vangronsveld: Director of the Centre for Environmental Sciences- Hasselt University, Diepenbeek, Belgium
  • Donato Mondelli: MAIB consultant 
  • Dr.Ziad Al Chami : Researcher/Analyst in Agricultural Chemistry at MAIB
  • Wouter Sillen: PhD researcher in the Centre for Environmental Sciences- Hasselt University, Diepenbeek, Belgium. 


The research work didnt face any major difficulty or obstacle. The only challenge that needs to be mentionned was related to the delivery of the pyrolyser kit machine from the United states which took relatively a long time to be shipped to Italy and then some more delay occurred due to complex customs services. All the other steps of the research work project went smoothly. 

This experience proposed sound key findings with important Environmental impact:
 The phyto-toxic waste could be transformed into useful products through pyrolysis (bio-oil, bio-gas and biochar). This process, allowed a biomass reduction up to 73% in terms of mass, answering by consequence to the need of valorisation of this waste and avoiding a polluting burden on the environment.
 Pyrolysis of this waste allowed a production of biochar highly concentrated in carbon that decomposes much slower than leaving it for natural decay, avoiding by consequence the re-emission of greenhouse gases and countering the climate change.
 The biochar product amended into multi-metal contaminated soil reduced the bioavailability of these metals, improved the physicochemical and biological soil functions, provided a better habitat for soil living organisms allowing an ecological restoration and revegetation of marginalized and abounded soils. 

The importance and applicability of the results of this research work are valuable and promissing for Europe and on international scale too. The remediation of marginal land, and notably contaminated soils, in Europe is a major challenge to sustainably increase the (non-food) crop production in line with relevant ecotechnologies and local conversion chains using such plant-based feedstocks instead of fossil carbon compounds and mineral raw materials. Enhancing such efficient in-situ remediation with biochar is a promising way that must be widely assessed. It will notably avoid the land change use of agricultural soils which is a major negative point challenging the increase of the world population and its nutrition. Soils in good conditions play a key role in the food and non food production and therefore the improvement of soil quality by such measures can contribute to the food security and possibly to the energy supply. 

The results of this research work were disseminated through :
 A thesis dissertation available in UniParthenope and Hasselt Universities, presenting the author's research work, methodologies, details and findings, entitled “Production of biochar from olive mill waste and remediation of heavy metal contaminated soil”.
 Oral presentations in international conferences.
 Two peer-reviewed scientific articles:

  • Article published in the journal Environmental Science and Pollution Research (see attached): Olive mill waste biochar: a promising soil amendment for metal immobilization in contaminated soils. Amine Hmid. Ziad Al Chami. Wouter Sillen. Alain De Vocht and Jaco Vangronsveld.
  • Article published in the journal Biomass and Bioenergy (see attached): Production and characterization of biochar from three- phase olive mill waste through slow pyrolysis. Amine Hmid, Donato Mondelli, Saverio Fiore, Francesco Paolo Fanizzi, Ziad Al Chami, Stefano Dumontet.
../file-system/small/pdf ../file-system/small/pdf Scientific Article Olive mill waste biochar: a promising soil amendment for metal immobilization in contaminated soils URL: http://www.ncbi.nlm.nih.gov/pubmed/25146122
../file-system/small/pdf ../file-system/small/pdf Scientific Article Production and characterization of biochar from three-phase olive mill waste through slow pyrolysis URL: http://www.sciencedirect.com/science/article/pii/S0961953414004346#