# Circular Economy Applied to Organic Residues and Wastewater: Research Challenges

Benedicte Bakan, Nicolas Bernet, T Bouchez, Rachel Boutrou, J.M. Choubert, P. Dabert, Christian Duquennoi, Vincenza Ferraro, Diana Garcia-Bernet, Sylvie Gillot, et al.

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## ► To cite this version:

Benedicte Bakan, Nicolas Bernet, T Bouchez, Rachel Boutrou, J.M. Choubert, et al. Circular Economy Applied to Organic Residues and Wastewater: Research Challenges. Waste and Biomass Valization, 2022, 13 (2), pp.1267-1276. 10.1007/s12649-021-01549-0. hal-03325254

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Submitted on 25 Aug 2021

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# Circular Economy Applied to Organic Residues and Wastewater:
Research Challenges

Bénédicte Bakan¹ ID · Nicolas Bernet² ID · Théodore Bouchez³ ID · Rachel Boutrou⁴ ID · Jean-Marc Choubert⁵ ID · Patrick Dabert⁶ ID · Christian Duquennoi³ ID · Vincenza Ferraro⁷ ID · Diana García-Bernet² ID · Sylvie Gillot⁵ ID · Jacques Mery³ ID · Caroline Rémond⁸ ID · Jean-Philippe Steyer² ID · Eric Trably² ID · Anne Tremier⁶ ID

Received: 20 May 2021 / Accepted: 15 August 2021

© The Author(s) 2021

## Abstract

To move today's agricultural and urban systems towards tomorrow's circular economy and respond to climate change, it is imperative to turn organic residues and wastewater into resourceful assets. This article discusses the changes that are needed in research to drive this paradigm shift and to go from a “losses and waste” situation to a “resource and opportunities” ambi- tion. The current lines of research aim to maximise the use and value of biomass or organic residues and wastewater and propose new organisational schemes driven by technical innovations. Exploring the pathways to a sustainable future through many domains let us identify five challenges to structure the research efforts and find circular bioeconomy solutions for organic residues and wastewater: (1) proposing innovative processes and integrated multi-process systems; (2) promoting the emergence of multi-scale and cross-sectoral organisations; (3) developing multi-performance evaluation methods, (4) rethinking research-society intersections, and (5) enhancing research-legislation interactions. We end by outlining prospects for moving forward past current limitations: beyond increasing knowledge, research will continue its own transition. Our responsibility today is not to think about what we could do for a better world but what we should do to make our ever-changing world even better and more sustainable.

## Graphic Abstract

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**Keywords** Biotechnology · Circular bioeconomy · By-product valorisation · Impact of science · Sustainability · Waste management

**Statement of Novelty**

This article is a position paper from researchers involved in engineering related to bioeconomy and having a long-term expertise in the coordination of collaborative projects. As such, its main interest is to gather all-important multidisciplinary aspects. The manuscript provides a framework by identifying five challenges for future research. The novelty is to assemble them in one location in a coherent framework in which researchers and engineers can think about their research and fully realize what they are in charge in. Even if some ideas may sound familiar, in each of the five sections, the challenges are briefly illustrated by examples from diverse biomass and waste valorisation that could inspire anyone involved in this field.

**Introduction**

For the past century, society has grown along a linear paradigm of extracting resources on one side of the planet to transform, exploit and most often dump residues in other places of the world, resulting in a total disconnection within natural organic and inorganic matter cycles. This is the case of the extraction of petroleum, coal, phosphorus, rare earths, raw materials used in animal feed, and even for the production of materials such as plastics. Modern value chains are often split into separate areas in the world between extraction, production, consumption and waste, which does not facilitate life-cycle approaches and circular bioeconomies. Furthermore, this globalised pattern of intensive resource use charts a trajectory to near-total depletion [1–3] with ‘colateral’ damage and impacts. They include climate change, water, air and soil pollution, loss of biodiversity and, ultimately, threaten the continued health and geopolitical stability of the planet.

According to the latest FAO (Food and Agricultural Organization of UN) estimates [4], roughly a third of all food produced ends up as residues (by-products and waste), which amounts to about 1.3 billion tons worldwide each year. It results from edible food lost during food production and postharvest handling and from discarded foodstuff such as unsold food, food preparation leftovers and uneaten food from households, restaurants and large producers, as collective caterers and supermarkets [5]. At the same time, according to the World Bank figures for 2016, the world's cities generate 2.01 billion tons of waste per year, with 3.40 billion tons expected in 2050, half of which being organic

waste [6, 7]. All this organic waste induces health-hygiene problems and nuisances that put strong environmental, economic and social pressure on urban centres. However, it is also an underexploited resource that, if better managed, could be used to produce materials, added-value products, soil amendments and energy, to support the development of a more sustainable societal model [8–10], as illustrated for agriculture by-products on Fig. 1. In this regard, scientists (illustrated by a magnifying glass on Fig. 1) lead research to enable (i) a cascade-valorization of food-industry by-products into resource added-value molecules while (ii) minimizing the waste. The development of such research parallels the increasing in the knowledge of the composition of raw materials for their optimal valorization, easing bottlenecks for *ad-hoc* extraction/treatment processes to recover valuable molecules and determining applications for their functionalities in target fields (Fig. 1).

The United Nations, through its 2030 sustainable development goals report [11], states the necessity “to accelerate responses to the world's gravest challenges—from eliminating poverty and hunger to reversing climate change”. This global objective opens wide perspectives for innovation but requires a rethink of usual scientific approaches to adopt a more systemic vision of all sectors of society. Actually, the core idea for initiating innovations can have multiple origins. Innovations can be incremental, by optimising a transformation chain step-by-step, or can stem from scientific discoveries generating new technologies that must then find their way to the market. New regulations, societal demand or economic constraints can also trigger new technology developments or innovative process chain structuration. In the field of organic residues and wastewater management, the role of scientists is no longer to simply reduce and eliminate waste and by-products but to maximise resource recovery in a safe and sustainable way. It is mandatory to face those challenges that will be reinforced with the growing population and the denser cities that are predicted for the near future. In this context, international researchers involved in waste/wastewater management question their role in the innovation process and how their activities are influenced by the new paradigm (from waste to resource), and vice-versa. So, how are researchers working to rise to these challenges? How do they imagine waste-to-value or wastewater-to-resource solutions engaging in the circular economy for today and tomorrow?

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<figure><img src="image_5.png" /><figcaption>**Fig. 1** The role of research scientists in the valorization of agricultural and industrial by-products. Scientists (illustrated by a magnifying glass) enable the processes' design from the fractionation of the agri by-products to the subsequent extraction and purification of high-value molecules. The fields of application are wide like surface cleaning, material and pharmaceutical. Scientists also make it possible to increment processes for a cascade valorization of the by-products.</figcaption></figure>

To do so, they develop innovative sustainable processes including digester and composter that are integrated in systems providing new opportunity for economic development, e.g. energy and heat, and animal feed and soil amendment. Multi-disciplinary approaches such as biochemistry, chemistry, physico-chemistry, microbiology and process engineering are required to ensure an efficient and complete value-chain

## How Can Research Help Forge a Sustainable Future?

For research scientists, the task of imagining a sustainable future is far from straightforward, as it requires a thorough and thoughtful evaluation of all plausible scenarios of soon-to-come patterns of socio-economic changes as well as their impacts on production systems at various scales. A system based on circular economy aims not only to give new added value to bio-waste and residual resources, but also to maintain the value of all types of resources for as long as possible, without harming the environment. In particular, bio-based products, bioenergy and wastewater reuse are key sectors in which research and innovation have a key role to play in the near future to develop technological and chain solutions supporting the deployment of circular bioeconomies [12]. To illustrate the challenges and potential impacts related to circular bioeconomy, one can mention Ronzon and Piotrowskiwe [13] who estimated that 395 million tonnes of dry matter (Tdm) of primary agricultural residues was produced in Europe in 2013 from more than 130 crop commodities, of which 69 million Tdm is collectable as feedstock for the biobased material and bioenergy sectors.

## By Proposing Innovative Processes and Integrated Multi-Process Systems

The trajectory of innovation in biomass, organic residues and wastewater management has so far been driven by sanitary and environmental concerns (generally supported by regulation) and economic development needs (including process efficiency and optimisation of energy consumption). Today's research challenges revolve more around developing innovative integrated systems that mobilise smart new approaches and technologies to readapt our transformation and production systems. Flexibility is needed to cope with market-driven changes in substrates and products, and make the multi-process system as sustainable as possible.

In agri-food industry, such as starch and sugar manufacturing industries, the valorization of side streams was already developed to produce a large panel of products. The “whole crop biorefining” also offers a portfolio of various products from grains and plant side streams such as straws and brans, [14, 15]. More recently, intensive investigation was put into reengineering the pretreatment processes conventionally applied to improve plant residues deconstruction and facilitate the recovery of high-value, low-concentration specific fractions. However, concerning animal by-products, innovative and non-conventional processes still need to be
implemented to harness their biological and technical poten-
tial. Here, the concept of “innovation” could materialise
through a raw-matter resource (the discarded animal tissues)
that is largely under valorised worldwide for the recovery of
specialty chemicals (just 1–2% for opotherapy and 1% for
the recovery of gelatine; [16]). Harnessing this innovative
resource requires processes that differ from those conven-
tionally used to convert animal by-products into low-value
products (mainly pet food) which were mainly designed to
minimise the huge amounts generated, estimated to be 20
and 100 million tons worldwide, each year, from fisheries
and meat (cattle, pigs and poultry) respectively, where ca.
5.2 and 16.5 million tons, respectively, arise from the sole
European Union [16].

The concept of environmental biorefinery was also
explored for waste and wastewater treatment [17, 18]. It
involves the incremental integration of mature processes into
existing plants to give added value [9, 19, 20]. For example,
such an approach could reduce the energy consumption of
wastewater treatment plants by a factor of more than 10 and
could even make wastewater treatment plants energy positive
while they represent today about 5% of the energy consump-
tion of a developed country [21]. Although the proposed
technologies are not necessarily disruptive, their integration
into a multi-process system provides new opportunities for
economic development. In the future, combining biologi-
cal and physical–chemical technologies will turn anaero-
bic digestion and wastewater treatment plants into biore-
source factories that goes beyond energy production. This
could produce a wide range of valuable end-products, from
biofuels and bioenergy (via biogas, biohydrogen and alga-
culture) to bio-based platform molecules (H₂, short-chain
or medium-chain organic acids) and biopolymers such as
alginate-like extracellular polymeric substances [22, 23] and
even protein sources [19]. Also of interest are the remaining
elements, which are recalcitrant to biodegradation. They will
be recovered in sludge and digestate that have lower eco-
nomic value but high value in terms of ecosystem services
(e.g., recycling nitrogen and phosphorous but also produc-
ing biopesticides, biosurfactants and composite materials
for agricultural purposes) [24]. Furthermore, improved val-
orisation of sludge and digestate can be performed through
post-treatment as filtration, evapo-concentration, compost-
ing, pyrolysis or co-gasification, etc. [25].

Lastly, introducing sustainability and circularity into pro-
cess development adds a challenge for researchers since it
co-addresses production performance, energy conservation,
environmental safety, and the health–hygiene credentials of
the end-products. Indeed, an optimised multi-process sys-
tem differs from the sum of its individually optimised core
technologies. For example, some processes used to remove
organic micro pollutants (antibiotics, detergents, etc.) or
microbial contaminants (pathogens, virus, etc.) are heavily

energy-intensive, but alternative processes that are less
energy-consuming cannot be developed at the expense of
end-product quality. Downstream usages are also crucially
important to sustain the use of new technologies. Technolog-
ical innovations investigating the effect of anaerobic diges-
tion on digestate quality and the fate of nutrients after soil
amendment give a case-in-point illustration of the kind of
tradeoffs researchers have to handle. Given the high number
of parameters to deal with, it has become crucial to develop
numerical multi-objective optimisation models to design
efficient and sustainable multi-process systems. With this
in mind, it is essential to model basic and applied research
on each of the core technologies and bring them together
into an integrated system to move innovation up towards
competitive industry operation.

By Promoting the Emergence of Multi-Scale
and Cross-Sectoral Organisations

For years, specialization, centralization and search for an
economy of scale have pushed developers towards high
capacity processes. In this context, the challenge to face
was often process up scaling. Nowadays, the development
of local economies, based on the creation of short food chan-
nels or for example on decentralized waste management,
drives the adaptation of the process scale to a chain or a
territory. However, downscaling of optimised large-scale
processes involves critical issues in terms of scale limit and
end-products production and valorisation. Beyond the tech-
nological aspects, making the chain economically viable
is also a challenge. The need for economies of scale and
return on investment still favours larger centralised facili-
ties, but different scales of processes can probably coexist
within the same territory depending on the resources they
use and the services they generate. Looking for example
at breweries, there are still a small number of large groups
mass-producing big brand beers, but the growing market is
for small ‘craft’ breweries whose economic model is very
different. Waste/wastewater management could follow the
same trajectory, with a few large centralised plants operating
alongside and smaller-sized tailor-made facilities adapted
to each territory and dedicated to specific waste-to-value
streams with higher added value [20]. Another example
of how multi-scale infrastructures can coexist comes from
integrated nature-based solutions for wastewater or leachate
treatment in urban areas, where they are seen as good candi-
date solutions to increase urban resilience while contributing
to the circular water economy [26, 27].

Actually, organisational factors are source of innovation.
A biorefinery or an anaerobic digester system has a radius
of action, i.e. the maximum distance from which resources
can be recovered, which makes it vital to properly size and
localise. For biogas plants, the location of the digester will

<figure><img src="image_6.png" /></figure>
also dictate the valorisation pathway of the biogas, i.e. grid injection, heat and electricity production, or as biofuel. It is also important to consider properly the stability of the organic residues and waste streams to ensure good storage and transport management without degradation and sanitary nuisance that would blunt the extraction yield of target functional molecules.

In this context, why not imagine a future where citizens self-manage their local waste community and profit from it? Such innovative project in circular micro-bioeconomy would require citizens and local stakeholders to become actors in their end-to-end biowaste management chain, from waste collection to process supervision. The drivers for this kind of change in chain pathway are much diverse. They can encompass economics, regulatory pressure, or technology-related constraints, but also reflect a more proactive engagement supported by community consensus, new opportunities or fresh ideologies. Here is a challenge for researchers to meet with companies and many stakeholders to engage in dialogue. In fact, moving outside of his or her core competencies and their comfort zone is a true challenge for everyone. Furthermore, a multisector strategy also hinges on potential complementarities or competition from different economic sectors in the same territory. This makes it important to consider the different by-products generated within a territory, particularly by agro-industry, in order to assess the potential for waste-to-value synergies. The transformation of wastewater treatment plants into recovery facilities of water resource requires a move from a pollution removal scheme to a biorefinery and energy supply scheme.

## By Developing Multi-Performance Methods to Evaluate Systems and Organisations

Efforts to evaluate processes and process chains in a circular bioeconomy run up against several difficulties, partly due to the existing evaluation methodologies and partly due to the lack of data [28, 29]. The first difficulty arises from the constructs of ‘sustainability’ and ‘circularity’ used to define bioeconomy. Sustainability requires that the processes and process chains developed safeguard the environment and support economic activity. It also requires a projection over time of the positive and negative impacts of the process or the sector, sometimes within territorial boundaries. Circularity raises questions about safety and nuisance that are very important issues in the field of wastewater reuse and waste valorisation, especially when there are conflicts over how to use the local resource, as is the case with treated wastewater reuse. Both require new value indicators to be developed and integrated into existing assessment tools such as life cycle assessment and efficient multi-objective optimization [30, 31], as proposed in social life cycle assessment for instance.

Other difficulties arise from multi-scale processes and the complexity of the network created by circularity [32]. The evaluation of multi-scale processes means that chain services that were usually evaluated separately now need to be evaluated as a single process route. Moreover, when a circular bioeconomy network interconnects matter, water and energy flows between three or more stakeholders, it may become extremely difficult to decipher and assess the entire network. Finally, if an innovative process is really disruptive with existing technologies or process chains, researchers need to extrapolate laboratory data to industrial processes with evident uncertainties, making it difficult to assess its risks and benefits compared to existing reference routes [33]. Therefore, new evaluation methods and multi-performance indicators are necessary making this topic of research a rapidly expanding area [34] to be further used for risk assessment and policy development.

## By Rethinking Research-Society Intersections

Researchers play a key role in the diffusion of scientific and technological knowledge in society. However, public acceptance and appropriation of new technologies, products or practices is never a foregone conclusion. What are the obstacles to organic residues and wastewater valorisation? There are several aspects to consider. The first concerns the products obtained from residual matter. Even if socio-economic and legislative landscapes are changing—largely thanks to increasing public awareness of the value of natural resources and the importance of sustainable production ways—consumers are not always receptive to the idea of using products obtained from what is currently considered ‘waste’. This is particularly true for products derived from animal residues, organic waste or treated wastewater [35]. How many people today are ready to use cosmetics made from animal by-products or organic waste? How many are ready to drink purified treated wastewater? This is where research can play a transformative role in helping to change consumer conceptions by bringing the data to demonstrate that molecules obtained from today’s residues are entirely safe and have unique value.

Public readiness to accept a biotech innovation can be interpreted through the construct of Technology Readiness Index (TRI). TRI is defined as “people’s propensity to embrace and use new technologies for accomplishing goals in home life and at work” [36]. For example, the public feedback was estimated for a new technology whose principle is to produce molecules by microbial electrosynthesis that is driven by organic waste oxidation [37]. Analysis identified three main trends of opinion: (i) a group that ‘adhered’ to the new technology on the basis of rational arguments related to the necessity to valorise waste and to positive perception of biotechnologies (high TRI); (ii) a group that
rejected the technology on the basis of rational arguments related to potential negative effects of massive waste treatment processes on waste reduction and negative perception of technologies in general (low TRI); (iii) a group of non-specialists that questioned whether it was possible to scale down the technology for a small community or even a household. This third group was generally well informed about waste-to-value and often referred to recent trends in micro-anaerobic digestion (medium TRI). Major transdisciplinary research, including social science, stakes should then be to first enhance the knowledge of these trends of opinion in the field of environmental biotechnologies, and second assess their impact on the general acceptance of innovative technologies and evaluate whether they are impacted by the involvement of technology researchers in the public debate.

Finally, concerning the installation of new waste treatment plants, public opposition is often characterised through the NIMBY ('not in my back yard') concept [38]. Analysis of many case studies on opposition to anaerobic digestion plants in Europe has found that the limiting steps are rather “non-technological” barriers [39–41] that can be collapsed into four categories: economic (investments, grants), administrative (policy and support measures, overwhelming bureaucracy), market-related barriers (new technologies know-how, supply-chain coordination), and public acceptance issues. Public opposition often relies on the trust citizens are ready to invest in policymakers and business, and includes the concepts of equity in the distribution of costs and benefits of the project. Participatory and community-based research projects have proven to be more successful

than projects sponsored by local institutions, agencies or businesses [38, 42–44]. The experiments reported by Zero Waste Europe demonstrate that new strategies for organic waste management with a better involvement of citizens and better communication among stakeholders can contribute to improved recycling rates and boost local employment [45, 46]. In this aim, the Horizon2020 EU R&I programme subsection ‘societal challenges’ served to frame the DECISIVE project [47] which proposes an innovative biowaste management scheme based on a network of short circuits for recycling urban biowaste in local urban or peri-urban farming. The concept turns biowaste into a resource to produce energy and bioproducts for local farming and food production (Fig. 2).

All these examples underline the need for stronger involvement of local stakeholders, and particularly citizens, and social sciences in innovation processes. With that vision, the European Commission birthed a programme called *SwafS-Science with and for Society* to build interplays between science and society at national and international level. Starting from 2015, the programme set out three strategic priorities: Open innovation, Open science, Open to the world (the ‘three Os’ strategy; [48]). These three Os have revolutionised the whole conception of research, development and innovation and brought a paradigm shift in scientist–policymaker relations. In line with the EU strategy, researchers are increasingly developing projects based on participative science where programmes are co-designed with citizens, stakeholders and end-users. An example was the Companion Modelling approach [49] that created

<figure><img src="image_7.png" /><figcaption>**Fig. 2** The DECISIVE biowaste management concept scheme for recycling urban waste in local urban farming. Food from urban farming is locally consumed at home or in restaurants, thus generating</figcaption></figure>

wastes being themselves treated in a micro anaerobic digester to produce energy and digestate used in urban farming. So that the cycle is closed. A magnifying glass illustrates scientists
a role-playing game (WasteWAG, Ter'Aguas) to guide the
creation and optimisation of sanitation services adapted to
developing countries.

By Enhancing Research–Legislation Interactions

Innovations brought by scientific developments on residual
biomass valorisation may not fit the older established legis-
lative framework; as such, certain bottlenecks in the regula-
tions may warrant review. Even though much progress has
been made on the high-value recycling of agri-food residues
and wastewater, provisional exemptions to governing regula-
tions could, for instance, open a pathway to novel applica-
tions for molecules recovered from that biomass, which in
turn could bring about novel organisational systems and new
forms of employment. In many countries worldwide, the
precautionary principle [50] may be sometimes interpreted
as a damper to innovation and then represent a dilemma for
decision makers in residual biomass valorisation. Recourse
to that principle is generally used when potentially negative
effects from a product or process have been clearly iden-
tified and/or when the scientific data needed to determine
the risk is deficient. Other cases require what the legislative
EU communication calls “examination of the benefits and
costs of action or lack of action”, which should be based on
socio-economic considerations. As also established therein,
scientific research has a crucial role to play, since the pre-
cautionary principle is periodically revised according to the
latest developments and data.

It is now widely accepted that scientific advice is hugely
important for public policy and decision-making [51],
and over the last decade, governance organisations have
increased their commitment to informing policy decisions
with the best scientific knowledge available. This has in turn
generated the creation and expansion of several types of sci-
ence advisory structures in several countries [52]. A hierar-
chy of values and aim to reconcile the diverse and sometimes
divergent interests and expectations of society’s constitu-
ent groups and communities should always guide changes
in regulations. Population wellbeing, environmental stew-
ardship, and new jobs and growth opportunities through a
cleaner and greener production industry (technologies, phar-
maceuticals, food, land fertilisation, etc.) can also coexist
peacefully with profitable industry thanks to academic sci-
entific research bringing new products/processes to market.

In the European Union, independent scientific policy
advice comes through the European Commission's Science
Advice Mechanism, which consists of the Group of Chief
Scientific Advisors and the Science Advice for Policy by
European Academies (SAPEA) consortium composed of
academic researchers. The advisors are consulted each time
science advice based on public research is critical to devel-
oping EU policy and legislation [53]. The recent directive on

waste [54] and the brand new regulation on fertilisers [55]
are both examples of the latest progress made by scientific
research on agriwaste management and valorisation. Direc-
tive EU 2018/851 [53] amends the 2008 text by promot-
ing better waste practices to support the transition toward a
circular economy and guarantee long-term competitiveness
for the European Union. The new regulation on fertilisers
amends the 2003 text by including animal by-products as
sources of nutrients for soil and soil improvers and consid-
ering them as promising raw materials for the production
of innovative fertilisers in a circular economy. Regulation
EC 1069/2009 [56] on animal by-products has thus been
amended, and changes entered into force from 8 April 2020.

To inform these new regulations and support the advisory
groups, results from research have to be mobilised beyond
the scientific literature. Involving researchers in cross-disci-
plinary scientific assessment is a key way forward to gather
worldwide knowledge on a specific question and bring it to
the attention of decision-makers.

Conclusions

Forging new circular bioeconomy pathways is one of the
most exciting challenges for research. It is no easy task, as
it requires a firm cohesive understanding of science, society,
human behaviour, the environment, and regulatory, indus-
trial and economic landscapes in order to strike the right
balance between creativity and practicality as we map out
possible scenarios for the future.

All of this has changed the way researchers conduct
their studies. Just a few years ago, it was still possible
to optimise the productivity or profitability of a process
by focusing on one single factor or on a short to medium
time horizon. Today, processes cannot be understood as
standalone units, and the criteria for optimisation have to
include multiple dimensions and to be analyzed on a long
term. The main consequences are that: (i) processes for
circular economy have to be engineered for modularity
(due to multiple and scarce sourcing channels, variable
quantity–quality of the resources, and other constraints),
for resilience (due to unexpected events such as shortages
in available raw feedstocks) and must combine strong pub-
lic health and safety credentials; (ii) mathematical tools
and multi-criteria optimisation have to be accounted for
and embedded in experimental studies to evaluate the
relevance of their objectives in terms of their economic,
environmental and social dimensions; (iii) public accept-
ance has to be factored in from the beginning and not, as
was often done in the past, after the innovation has been
optimised; (iv) legislation has to be reassessed regularly
to adapt to new scientific knowledge and technical devel-
opments. In addition, in terms of bio-sourced products,
it is important to move forward from producing added-value biomolecules to replace oil-sourced molecules to a bio-functionality paradigm—in other words, it is not the molecule itself that has to be replaced but the service that it brings.

One last important aspect shaping today's studies is the time and geographic scales in which they have to be conducted to avoid inconclusive experiments. To drive change, public and private researchers need the freedom to experiment new technological and organisational systems at relevant spatial (i.e. large) and temporal (i.e. long) scales. This will require longer-term public funding, i.e. some grants running longer than the current 3 to 4-year model, and possibly also at least a temporary readjustment of the current rules and regulations over test territories. With that vision, research will also certainly need to capture public support and consent and committed political backing, which is another challenge in itself.

**Acknowledgements** The authors thank Pascale Manchado-Sarni for her upstream work on food waste and her advice to write this article.

**Author Contributions** Conceptualization: All authors, Formal analysis and investigation: All authors except RB, Writing—original draft preparation: All authors; Writing—review and editing: All authors, Supervision: RB.

**Funding** This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors for the submitted work.

## Declarations

**Conflict of interest** The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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## Authors and Affiliations

Bénédicte Bakan¹ ID • Nicolas Bernet² ID • Théodore Bouchez³ ID • Rachel Boutrou⁴ ID • Jean-Marc Choubert⁵ ID • Patrick Dabert⁶ ID • Christian Duquennoi³ ID • Vincenza Ferraro⁷ ID • Diana García-Bernet² ID • Sylvie Gillot⁵ ID • Jacques Mery³ ID • Caroline Rémond⁸ ID • Jean-Philippe Steyer² ID • Eric Trably² ID • Anne Tremier⁶ ID

<figure><img src="image_8.png" /></figure>

Rachel Boutrou
rachel.boutrou@inrae.fr

Bénédicte Bakan
benedicte.bakan@inrae.fr

Nicolas Bernet
nicolas.bernet@inrae.fr

Théodore Bouchez
theodore.bouchez@inrae.fr

Jean-Marc Choubert
jean-marc.choubert@inrae.fr

Patrick Dabert
patrick.dabert@inrae.fr

Christian Duquennoi
christian.duquennoi@inrae.fr

Vincenza Ferraro
vincenza.ferraro@inrae.fr

Diana García-Bernet
diana.garcia-bernet@inrae.fr

Sylvie Gillot
sylvie.gillot@inrae.fr

Jacques Mery
jacques.mery@inrae.fr

Caroline Rémond
caroline.remond-zilliox@inrae.fr

Jean-Philippe Steyer
jean-philippe.steyer@inrae.fr

Eric Trably
eric.trably@inrae.fr

Anne Tremier
anne.tremier@inrae.fr

1 BIA, INRAE, 44300 Nantes, France

2 LBE, INRAE, Univ Montpellier, 11100 Narbonne, France

3 PROSE, INRAE, Université Paris-Saclay, 92160 Antony, France

4 STLO, INRAE, Institut Agro, 35042 Rennes, France

5 REVERSAAL, INRAE, 69625 Villeurbanne, France

6 OPAALE, INRAE, 35044 Rennes, France

7 QuaPA, INRAE, 63122 Saint-Genès-Champanelle, France

8 FARE, UMR A 614, Chaire AFERE, Université de Reims Champagne-Ardenne, INRAE, 51097 Reims, France

<figure><img src="image_9.png" /></figure>