Enhancing anaerobic digestion models for high loads and stressed conditions: integrating thermodynamics and new metabolic pathways

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INRAE presentation

The French National Research Institute for Agriculture, Food, and Environment (INRAE) is a major player in research and innovation. It is a community of 12,000 people with 272 research, experimental research, and support units located in 18 regional centres throughout France. Internationally, INRAE is among the top research organisations in the agricultural and food sciences, plant and animal sciences, as well as in ecology and environmental science. It is the world’s leading research organisation specialising in agriculture, food and the environment. INRAE’s goal is to be a key player in the transitions necessary to address major global challenges. Faced with a growing world population, climate change, resource scarcity, and declining biodiversity, the Institute has a major role to play in building solutions and supporting the necessary acceleration of agricultural, food and environmental transitions.

Work environment, missions and activities

About INRAE-LBE

The Laboratory of Environmental Biotechnology (LBE) at INRAE is a world-leading research institute dedicated to innovative environmental technologies. We focus on developing sustainable solutions to address pressing global environmental challenges. Our interdisciplinary team of scientists and engineers works collaboratively to advance the field of environmental biotechnology, with a particular emphasis on resource recovery, wastewater treatment, and bioenergy production.

Job description and scientific context

Anaerobic digestion (AD) is a core solution for the transition from waste treatment to resource recovery. AD possesses a high potential for renewable energy recovery as biogas (mainly methane, CH₄) from waste. Nowadays, 50 million micro-digesters and 132,000 full-scale digesters are operating globally for waste management and energy recovery, and the global energy generation potential from major feedstocks (including liquid wastewater and solid waste) by AD can meet 23-32% of the world’s coal consumption or 16-22% of the electricity consumed (World Biogas Association, 2019).

As experimental research can only investigate a limited number of conditions due to the cost and human resource limitations, AD mathematical modelling has been largely applied to further understand microbial interactions among different clades, for process optimization, and for scenario simulation (Regmi et al., 2019). The reference model for AD, the IWA Anaerobic Digestion Model 1 (ADM1) (Batstone et al., 2002) was initially developed to describe digestion of sludge from wastewater treatment plants, which was the primary application of digesters at the time. However, as AD is now applied to a broad variety of waste streams, including agricultural residues, food waste, or industrial effluents, adaptation and extension of the reference model have become necessary. In particular, recent studies have highlighted the need to modify the ADM1 to accurately represent the underlying processes in stressed digesters (i.e., fed with concentrated substances) (Pastor-Poquet et al., 2018).

This PhD project is part of the European doctoral network LeAD (Leveraging Anaerobic Digestion through environmental stressors; https://cordis.europa.eu/project/id/101168769). The current knowledge and the information gathered from dedicated stressed AD systems will be formalized using novel mechanistic models based on ADM1. The developed model will consider non-ideal corrections (Capson-Tojo et al., 2020), thermodynamics (Patón and Rodríguez, 2019), and relevant pathways such as syntrophic acetate oxidation and chain elongation (Capson-Tojo, Astals and Robles, 2021), which are omitted in most modelling efforts. This will provide comprehensive information on stressed AD, extending the applicability of the model to virtually any digesters and aiding to develop strategies for stable operation.

Key Objectives

• To develop a novel model including syntrophic acetate oxidation and chain elongation, and incorporating thermodynamic constraints
• To generate experimental data using continuous reactors operated under stressed conditions, including high organic load, elevated total ammonium concentration, saline conditions, and load shocks
• To define the structure of the model and validate with independent datasets

Specific Tasks

• Development, calibration, and validation of mechanistic models for AD
• Incorporation of thermodynamic constraints into mechanistic models
• Setup, operation, and follow-up of continuous AD reactors
• As final result, a modified ADM1 model adapted to high loads and stressed conditions should be obtained

Training and skills

Requirements

• Academic Background: MSc degree in Environmental/Chemical/Bioprocess Engineering, Biotechnology, or a related field.
• Skills (recommended): experience in bioprocess mechanistic modelling; analytical and laboratory skills, experience running bioreactors; scientific communication and writing skills.
• Attributes: self-motivated, able to work both independently and as part of a team, and enjoys supervising students.
• Language: fluent use of English; knowledge of French is an advantage but not required.
• Motivation: the candidate should be enthusiastic and outgoing when searching for solutions to challenges that will arise during the experimental work. The candidate should aim for scientific output in top conferences and scientific journals.

INRAE's life quality

What We Offer

• Cutting-edge research environment: work in a state-of-the-art laboratory equipped with the latest technologies in environmental biotechnology. The equipment is fully shared, so you will have access to all the facilities.
• Mentorship and training: receive guidance from leading experts in the field and access to a comprehensive training program.
• Collaborative network: engage with a dynamic team of researchers and industry partners, both nationally and internationally.
• Funding and resources: competitive stipend and funding for research-related expenses, including conference travel and publications.
• Career development: opportunities for professional development, including workshops, seminars, and networking events.
• Work atmosphere: You will be part of a team that takes their work very seriously. We pride ourselves on fostering a collaborative and supportive atmosphere where researchers and interns work together in a dynamic and friendly environment to drive innovative solutions for environmental sustainability.
• Great working conditions: 30 days of holidays per year (+ 15 if time recovery is affected); support for parenting; access to inexpensive collective restaurants; flexible schedule; access to on-site sports facilities; sunny weather.
• Planned secondments at top universities: (i) University of Galway under the supervision of Guangxue Wu for 3 months, working on r/K strategists and visiting GlasPort Bio for industrial training; (ii) to Politecnico di Torino under the supervision of Silvia Fiore for 3 months, working on biochar addition to stabilise AD.
• Salary (gross): 3957 €/month.

Specifically, the PhD will learn how to develop, calibrate, and validate mechanistic models, and how to setup and monitor AD reactors. For the latter, the candidate will use state-of-the-art analytical and monitoring equipment. The PhD candidate will have the support of experienced researchers and technicians.

How to apply

I send my CV and my motivation letter