The challenge of closed-loop urban waste recovery

As urban populations increase, urban waste management is becoming a crucial issue for regional stakeholders. Through the European Decisive project, Irstea and its partners are drawing up an innovative management approach based on local recovery and set within a circular economy context. Three years on from the launch of Decisive, the first demonstration site near Lyon will be inaugurated and introduced to the public on November 14. This is an opportunity to review the progress of this promising project with Anne Trémier, project coordinator and Irstea research engineer.

Receiving 7.7 million euros of funding, the Decisive project was picked as part of a call for projects by the European H2020 program [1], which aims to discover innovative urban waste management solutions. How is the Decisive proposal innovative compared to existing solutions?

Anne Trémier: Currently, waste is collected and then exported relatively far from where it is produced to be processed and recycled. In Decisive, we plan to recover waste as close as possible to where it is produced. By looking at Irstea’s previous work on local processing for household waste (particularly composting), we noticed that when individuals know where their waste goes and how it will be recycled, they produce less of it. This led to the idea of implementing a circular waste management process: I buy supplies, therefore I produce waste; I collect the waste which I then recycle into resources that can be used immediately. The aim is to provide large-scale local recycling based on the circular economy. The ultimate result should be a reduction in waste production through improved resident engagement, energy and transport savings, and eventually, more sustainable development for urban areas.

To ensure the success of this concept, the Decisive partners are focusing on small or micro-scale anaerobic digestion. What will this method look like?

Anne Trémier: As with the traditional anaerobic digestion process, the “miniature” method will produce biogas, which can be reused directly as energy, and digestate (anaerobic digestion residue), which can be used to create a high value-added product such as biopesticides. To ensure the process is compatible with a dense urban environment, we expect to create facilities that will be able to process a maximum of 200 tons of biowaste per year [2], which is equivalent to the amount of waste produced by a neighborhood of 800 to 1000 households. Our main technological challenge is how to implement an anaerobic digestion process that is adapted to this scale, has low power requirements so that its energy balance remains positive, but which is also simple to use, compact yet reliable to meet local requirements (safety, regulations).

Decisive was launched in 2016; what progress has been made to date?
Anne Trémier: We have developed the basic concept for this local method two specific tools to help implement it. The first is a decision-making tool that will help local communities use their current waste recovery strategy to evaluate the increased value that implementing a local, decentralized system would provide, comparing technical, environmental, economic and social indicators. Additionally, at Irstea, we have designed a spatial planning method for these sites. Using geographic information system (GIS) tools along with data on the biowaste resources for a specific area and existing constraints (regulations, logistics, etc.), this second tool can be used to map out the best locations for waste management centers in the area. Designed for local communities as well as consultancy firms and other biowaste management operators, these tools will soon be available through an online platform from the Decisive project website.

Another notable development is the installation of a micro-scale anaerobic digester (based on existing commercial technologies) in real conditions, at the Ecully horticultural school near Lyon. Fed by the school cafeteria and nearby hotels and restaurants in Lyon, this demonstrator was launched in October to establish the feasibility of local management for the whole sector. In other words, it will close the loop, transforming biowaste into energy and fertilizers that can be used directly on site to grow vegetables.


Laboratory pilot
Laboratory pilot for the micro-scale anaerobic digester developed by the OPAALE team

Aside from the organizational issues, what is that status of the planned micro-scale anaerobic digester process?

Anne Trémier: In order to use as little water and energy as possible, we used Irstea’s expertise in anaerobic digestion to develop an innovative process of continuous, dry micro-scale anaerobic digestion that is self-sustaining with regular inputs of biowaste and no additional water requirements. Using this unique process, for which a patent application has been filed, we designed a laboratory pilot that has been operational for a year and is capable of treating 20 liters of waste at a time. We are currently building another prototype, capable of treating up to 100 liters of waste, which will be used to test the process under real conditions using biowaste from an office cafeteria. In parallel, our Spanish partners at the Autonomous University of Barcelona, responsible for investigating the production of biopesticides using digestate, have validated the method [3] and relevance of the molecule obtained. The process is now being tested at an existing industrial anaerobic digestion facility.

What do you think is the greatest obstacle that needs to be overcome before your proposed waste management method becomes a reality?

Anne Trémier: If we only use current economic and financial indicators, we already know it will be difficult to find a successful business model. Our biggest challenge is creating models that can assess economic, social and environmental indicators equally and determine the conditions in which the approach can become viable, or even essential. It is a significant change to implement.
Decisive project profile
  • Name: A decentralized management scheme for innovative valorization of urban biowaste
  • Total cost: 8.7 million euros - Contribution by the European Union: 7.7 million euros
  • Coordinator: Anne Trémier, Irstea
  • Dates: 2016-2021
  • Partners: 14 European partners from the academic and private sectors
  • Decisive project Website


Decisive presented at the European Workshop on Bioeconomy

To identify the research needed to create a sustainable bioeconomy that incorporates the finite limitations of the planet, INRA, Irstea and IFPEN, in partnership with the French Ministries of Agriculture and Food, Higher Education, Research and Innovation, and Ecological and Solidarity Transition and the German Federal Ministry of Food and Agriculture are organizing a European workshop on bioeconomy on October 29 and 30, 2019 in Paris. During this event, Anne Trémier will discuss the initial results and future aims of the Decisive project as part of the “circular urban bioeconomy” theme.


Further information

[1] This project received funding as part of the European Union’s Horizon 2020 research and innovation program (no. 689229).

[2] In contrast, existing small agricultural anaerobic digestion facilities process between 1000 and 2000 tons of organic waste per year.

[3] The method involves growing the Bacillus thuringiensis microorganism, known for its insecticide properties, on the anaerobic digestate.