# Evaluating alternatives for co-product use in European agriculture: Does regional context matter?

W.J. Vonk, A.G.T. Schut, R. Hijbeek, C.F.E. Topp, Myriam Grillot, M.V.

Odgaard, T. Dalgaard, M.K. van Ittersum

► To cite this version:

W.J. Vonk, A.G.T. Schut, R. Hijbeek, C.F.E. Topp, Myriam Grillot, et al. Evaluating alternatives for co-product use in European agriculture: Does regional context matter?. Science of the Total Environment, 2025, 1003, pp.180698. 10.1016/j.scitotenv.2025.180698. hal-05392650

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# Evaluating alternatives for co-product use in European agriculture: Does regional context matter?

W.J. Vonk<sup>a,*</sup>, A.G.T. Schut<sup>a</sup>, R. Hijbeek<sup>a</sup>, C.F.E. Topp<sup>b</sup>, M. Grillot<sup>c</sup>, M.V. Odgaard<sup>d</sup>, T. Dalgaard<sup>d</sup>, M.K. van Ittersum<sup>a,e</sup>

<figure><img src="image_3.png" /></figure>

## HIGHLIGHTS

* Impacts of co-product use options were compared between four European regions.

* Manure was most important in NL and DK regions, crop residues in FR and SC.

* Manure digestion reduced GHG emissions but lowered effective organic matter inputs.

* Crop residue retention raised EOM inputs, digesting improved the energy balance.

## GRAPHICAL ABSTRACT

### Evaluating alternatives for co-product use in European agriculture: Does regional context matter?

Co-product use options:

<figure><img src="image_4.png" /></figure>

Main model outcomes per region:

<figure><img src="image_5.png" /><figcaption>Table 1: main outcomes compared to the reference scenario in each case study region. Numbers indicate the co-product use.</figcaption></figure>

<table><thead><tr><th>GHG emission</th><th>Energy balance</th><th>EOM additions to soil</th></tr></thead><tbody><tr><td></td><td>(3) +++</td><td>(2) ++</td></tr><tr><td>(1) -</td><td>(1) ++</td><td>(1) -</td></tr><tr><td>(1) -</td><td>(1) ++</td><td>(1) -</td></tr><tr><td></td><td>(3) ++</td><td>(2) ++</td></tr></tbody></table>

## ARTICLE INFO

Keywords:

Regional agricultural systems

Nitrogen flow model

Greenhouse gas emission

Nutrient circularity

Manure

Crop residues

## ABSTRACT

Integrated agricultural systems which connect crops, livestock, industry, and consumers through recycling of co-products potentially reduce losses to the environment and utilise inputs more efficiently. This study assesses how co-product use in agriculture affects food production and its environmental performance in multiple European regions, and evaluates how regional context affects the optimum use of available co-products.

An exploratory nitrogen flow model, including quantification of greenhouse gas (GHG) emissions, effective organic matter (EOM) inputs, and energy use, was applied to assess co-product use options across four European regions: Ariège (Southern France, A-FR), Drenthe (Northeastern Netherlands, D-NL), Fife (Eastern Scotland, F-SC), and the inner Limfjord catchment (Northwestern Denmark, L-DK). Various use options were assessed for three co-product types: manure, crop residues, and household organic waste.

In L-DK and D-NL, more manure was available than in A-FR and F-SC, which strongly affected outcomes of the alternative use options. Manure digestion reduced GHG emission (ranging from -2.0 % to -19.8 % across regions), but EOM soil inputs decreased (-1.1 % to -25.3 %) compared to untreated manure. Crop residue use was important in regions with more cereal production (L-DK and F-SC), improving the regional energy balance when

<footnote><sup>a</sup> Plant Production Systems, Wageningen University & Research, Wageningen, the Netherlands</footnote>

<footnote><sup>b</sup> Scotland's Rural College (SRUC), Edinburgh, United Kingdom</footnote>

<footnote><sup>c</sup> Université de Toulouse, INRAE, INPT, El PURPAN, AGIR, Castanet-Tolosan, France</footnote>

<footnote><sup>d</sup> Department of Agroecology, Aarhus University, Land-CRAFT.dk, Tjele, Denmark</footnote>

<footnote><sup>e</sup> Department of Crop Production Ecology, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden</footnote>

<footnote>* Corresponding author.</footnote>

<footnote>E-mail address: wytse.vonk@wur.nl (W.J. Vonk).</footnote>
digested (+11.1 % to +195.5 %), or increasing EOM inputs when retained (+2.8 % to +15.9 %) compared to residue removal. What happened with household organic waste had less effect on the indicators, because of the small volumes compared to manure and crop residues. Our study suggests that regional context strongly affects the impact of co-product use options on environmental indicators. Prioritization of co-product utilization should mainly consider co-product type and its regional availability.

# 1. Introduction

The need to reduce labour costs and increase labour efficiency and ongoing technological developments drive agricultural specialisation (Schut et al., 2021). As a consequence, the decoupling of sub-systems in agriculture is ongoing, resulting in a strong dependence on imported feeds and fertilisers. In such linear systems the nutrient use efficiency is typically low with large losses and significant environmental impacts (Leip et al., 2011). Despite the adoption of the United Nations Sustain-able Development Goals (SDGs) in 2015, and the introduction of several European action plans (European Commission, 2019), progress towards reaching responsible consumption and production targets in Europe is slow or even stagnating with major persisting challenges for agriculture (Lafortune and Fuller, 2025). Better integration of agricultural systems where crop production, livestock, food industry, and consumers are connected through recycling of available biomass via feed and fertiliser, have the potential to utilise inputs more efficiently, with lower losses (van Loon et al., 2024). In this paper, we refer to biomass in waste streams and by-products as co-products. Management of agricultural co-products such as manure and crop residues takes place on-farm or by exchanging biomass between farms within a region. Co-products - including organic waste streams from industry and households - can also be processed (e.g. composting, anaerobic digestion, or incineration) before being re-used in agriculture. In this study, our focus is on co-products as fertiliser, source of soil organic matter, and for energy production, but some co-products may also have value in agriculture as a resource for the circular economy (Bos and Broeze, 2020), animal feed, or for soil carbon sequestration (de Boer and van Ittersum, 2018).

Effective management of co-products in agriculture is essential to reduce external inputs and prevent negative impact on the environment, while maintaining or even increasing land productivity. Existing liter-ature on co-products often focusses on single environmental or pro-ductivity indicators, potentially overlooking trade-offs and pollution swapping (De Vries et al., 2015). The losses associated with misman-agement of co-products, e.g. manure or crop residues, result in eutro-phication, acidification, greenhouse gas (GHG) emissions and phosphorus (P) saturation of soils. Decades of soil P surpluses have saturated large agricultural areas (Schoumans and Chardon, 2015; Fischer et al., 2017) and, depending on soil wetness, N surpluses lead to the emission of nitrous oxide (N₂O), strongly contributing to global warming (Myhre et al., 2013) or nitrate (NO₃) in ground and surface waters that may also contribute to secondary N₂O emissions. Addi-tionally, excessive nitrogen (N) deposition and acidification following ammonia (NH₃) emission from manure may reduce biodiversity in sensitive nature areas (Payne et al., 2017). At the same time, proper application of co-products to the field could benefit the organic carbon balance in the soil, with positive effects on soil structure and water retention (Urra et al., 2019). Additionally, the need to import nutrients (e.g. feed or fertiliser) may decrease when optimizing the recycling of nutrients from available co-products in the region, increasing nutrient circularity (van der Wiel et al., 2021; Lessmann et al., 2023). An assessment of trade-offs and synergies between several production and environmental indicators, such as done in the present study, may pro-vide better insight in the best options to recycle co-products in agriculture.

In future scenario studies, where the livestock sector and manure excretion are expected to decrease with a shift in diets (Bouwman et al., 2013; van Selm et al., 2023), efficient utilization of alternative nutrient

sources will become more important. Co-products, other than manure, are not often included in agricultural models (Dougherty et al., 2023; Lafortune et al., 2025), or considered as external inputs whose avail-ability does not reflect local conditions. Furthermore, comparative analysis across multiple contrasting regions is needed to support locally tailored policies. Most nutrient circularity studies at a regional level have focused on livestock-dense regions with excess nutrients (van der Wiel et al., 2021). However, co-product management options and their impact on various indicators may differ between regions, for instance depending on the type and number of livestock present or land use for crops or grasslands. Hence, studying the effect of co-product use stra-tegies embedded in the local context focussed on improving agricultural production and reduce environmental impact may support local au-thorities in decision making towards reaching sustainability targets.

This study quantifies the regionally available co-products, and as-sesses how co-product use in agriculture affects food production and the environmental performance in four contrasting European regions, to inform prioritization of co-product use options in different contexts. We focus on three co-product types, comparing alternative uses for: 1) manure – comparing direct application with anaerobic digestion; 2) crop residues – assessing removal, retention, and anaerobic digestion; and 3) household organic waste – evaluating the differences between not being used in agriculture, use after composting, and use after anaerobic digestion. To analyse the feasibility and trade-offs of these use options, key agronomic and environmental indicators were quantified, including food N production, GHG emissions, net agricultural energy balance, effective organic matter (EOM) inputs to the soil, soil N surplus, and N losses.

# 2. Material and methods

Co-product use options were evaluated for four European case study regions. The case study regions all include (varying types of) crop pro-duction and livestock husbandry but they differ in their land-use and agricultural system. In each region, N balances were constructed using a nutrient flow analysis approach. Based on these N balances, several productivity and environmental indicators were quantified, including food N production, GHG emissions, agricultural energy balance (energy consumption and production), effective organic matter (EOM) inputs to the soil, soil N surplus, and N losses. The indicators were assessed in all regions for several use options per co-product type, expressed per hectare of agricultural land included in the model selection.

## 2.1. Case study regions

Four European case study regions are included: Ariège, southern France (A-FR); Drenthe, northeastern Netherlands (D-NL); Fife, western Scotland (F-SC); the (inner) Limfjord catchment, located in north-western Denmark (L-DK). In total, including nature, water, and urban areas, Ariège is the largest region (approx. 489,000 ha), followed by Drenthe (268,000 ha), the Limfjord catchment (260,000 ha), and Fife (133,000 ha). Agriculture plays an important role in shaping the land-scape in all regions, with a land use larger than 50 % of the total area in all regions except Ariège (A-FR: ~41 %, D-NL: ~63 %, F-SC: ~67 %, L-DK: ~63 %). In Ariège, a large part of the land is unused or protected nature area, mostly in the foothills and mountains of the Pyrenees. The human population density, used to estimate available household organic waste production, is highest in Fife (4.2 inhabitants per ha farmland), followed
by Drenthe, the Limfjord catchment, and Ariège with 3.0, 1.1 and 0.8 inhabitants per ha farmland respectively.

Livestock density is highest in the Limfjord catchment and Drenthe, with dairy, pig, and poultry production, while Ariège and Fife have a lower density with mainly dairy, beef, and sheep (Fig. 1). The share of cereal crops is the largest in Fife and the Limfjord catchment, while grassland is more important in Ariège and Drenthe.

## 1. Ariège, France (FR)

Ariège is a region located in south-western France, marked by its topography: hillside plains in the north (<500 m of elevation), piedmont area and mountains in the south (>900 m, the Pyrenees), and an intermediate area. In 2020, there was 2265 farms. Between 2010 and 2020, the department lost 15 % of its farms, while the average farm size increased to 59.6 ha (+20 %). More specifically, the number of livestock declined, and the number of farms with cattle and sheep declined by 22 %. This matches with the French national trend. In 2020, most farms were livestock oriented (58 % of the farms), mostly producing bovine (27 %) and sheep (17 %), crop-oriented (22 %) or mixed (12 %). Grassland covers a large share of the agricultural land (including temporary, permanent and grazed woods), followed by cereal crops and other crop types (Fig. 1).

Eighteen percent of the total land is labelled as "nitrogen sensitive" area, restricting the quantity of nitrogen applied to crops, as well as effluent management. This mostly covers the northern part of the department, where most crops are grown. Fifty percent of the total land area is included in a regional park ("parc naturel regional"), including

10 % protected as "Natura 2000" area. These areas are mostly located in the south-western part of the department, which mostly corresponds to piedmont and intermediate area. Most ruminant livestock graze in summer pastures in the Pyrenees between June and September.

For co-product management, most of the manure is directly deposited in the fields during grazing or is used directly on the livestock farm. Due to the topography of the region, the roads are steep and twisty, resulting in a long journey between the northern (mostly crop farms) and southern (mostly livestock farms) areas. Co-products such as manure and straw can be exchanged but their transportation cost is high. Since 2021, in the hillside plains, a biogas plant has been established, mostly aiming to digest crop residues, sourcing most of its feedstock from seed maize fields.

## 2. Drenthe, the Netherlands (NL)

Drenthe is a province located in the north-east of the Netherlands. The province has a diverse landscape including mixed and specialized arable and livestock farms, where agriculture is still an important economic activity. The north-east of the province consists of former peat soils, which were used for turf extraction but are now mainly sandy soil with high levels of inert carbon from peat residues. Mainly arable farms are located here with a typical 1:2 rotation of starch potato alternating with sugar beet or spring barley. Onion and lilies are increasingly cultivated in the region. Towards the south-west, more dairy farms with grassland and silage maize can be found on sandy soils. In addition, intensive pig, poultry and some goat farms (note that goats were excluded from the present analysis) with little or no land are located

<figure><img src="image_6.png" /><figcaption>**Fig. 1.** Livestock production and agricultural land use in the four case study regions, as included in this model study: Ariège (A-FR), Drenthe (D-NL), Fife (F-SC), and the Limfjord catchment (L-DK). Livestock production (LU ha⁻¹) is shown on the left. A detailed representation of the agricultural area is shown on the right. Crop groups included in this study are shown with the surface of the squares indicating their respective cultivation areas for each region (dark green = grassland, light green = silage maize, yellow = cereals, orange = oil crops, red = root & tubers, pink = legumes). The pictures are exemplary for the agricultural landscapes in each region.</figcaption></figure>
across the entire province. A small share of the agricultural area in the province is occupied by greenhouse horticulture and fruit cultivation. From the currently available manure in Drenthe, approximately 20 % is used for biogas production via digestion (Smit et al., 2021). In 2021, there were seven active co-digesters and one large mono-digester in Drenthe, while smaller on-farm mono-digesters are also present.

Nature is protected in dispersed patches across the whole region, mainly consisting of forest, heathland, and some drifting sands. Nitrogen oxides and NH₃ emissions with subsequent N deposition and acidification are linked to the decline in nature quality. Policies to reduce these emissions put pressure on the present and new agricultural activities in Drenthe. This is especially the case for intensive livestock farms with large NH₃ emissions. Buyout schemes have been proposed to reduce NH₃ emissions, but so-far have not led to large emission reductions. There are 14 protected so called “Natura 2000” areas in Drenthe, of which 12 have been labelled “nitrogen sensitive” (Van Dobben and Van Hinsberg, 2008).

### 3. Fife, Scotland (SC)

Fife is located on the east coast of Scotland, between the Firths of Forth and Tay. It represents a broad spectrum of land classes from highly productive land with productive clay soils, rich in organic matter, and relatively freely drained to poor grazing lands. The main land use is agriculture. Tourism is also important in the area, particularly along the coastal strip, and Fife is well-known for its 42 golf courses including the championship course at St. Andrews. Small pockets of land in the region are used for forestry, nature reserves particularly peat bogs, and urban areas. There are 47 Sites of Special Scientific Interests in the region. The main crops grown in the area, apart from grassland, are spring barley, winter wheat and potatoes. Fife is also an important region for vegetable production, mainly brassicas, for human consumption. The main livestock enterprises in the region are beef breeding and finishing units, and sheep enterprises are common. Fife has few dairy farms. There are also a small number of intensive pigs and poultry units. Typically, the farms are managed conventionally. Many of the farms in Fife are mixed arable-livestock farms. However, typically the farms are disconnected with little collaboration. Nevertheless, there is growing interest in sheep farmers collaborating with arable farmers to graze the sheep over the winter on cover crops or winter cereals. There are also opportunities in the region for alternative utilization such as increased use of brewing products or residues from vegetable production.

### 4. Limfjord catchment, Denmark (DK)

The Danish site is situated in Northwestern Jutland and represents part of the Limfjord catchment. The area is dominated by soils with a sandy-loamy texture, developed on Weichel Ice Age glacier moraine material (about 0–70 m above sea level). The main land use is agriculture with highly specialized but integrated arable and livestock farming systems, which has been the main land use for many decades (Lohrum et al., 2024). This long-term intense usage of the land for agriculture, with high N inputs, has resulted in a eutrophicated Limfjord estuary with a poor ecological status (Erichsen and Timmermann, 2023; Kronvang et al., 2023). Therefore, relative to the overall situation in Denmark, this region has some of the highest N reduction targets (set to fulfil the goals of the European Water Framework Directive).

One initiative towards a cleaner fjord is to reduce nitrate leaching via the inclusion of more leys with grass in the crop rotations (or more permanent grasslands). Harvested grass can be used for protein-extraction through a biorefinery process, as a substitute for imported protein crops. In addition, significant biogas production already takes place in the region, and new large scale biogas plants are being built to process manure and other co-products, including grass and food industry waste, into renewable biogas energy. The biogas remnants (digestate) is further processed into biochar which is recycled back to

the local fields as fertiliser and/or soil conditioner, thereby contributing to circularity of the system. All this is promoted by new policies to promote a green transition and lower nitrogen losses and greenhouse gas (GHG) emissions, including subsidy schemes for environmentally friendly practices and the introduction of a GHG emission tax.

### 2.2. Modelling impacts of co-product management across four case studies

In this study, the N flow model developed by Vonk et al. (2025) was used to analyse the performance of co-product use options for the agricultural systems of the four European case study regions. A detailed model description including all equations is available in Vonk et al. (2025). A short summary is provided in Sections 2.2.1 and 2.2.2, including details for some model additions and updated data sources to parameterize the model. The model was designed to quantify production and environmental indicators for scenarios of improved nutrient cycling in agriculture at farm and regional level. Here, the N flow model was deployed to analyse the agricultural production system with crop and livestock production, including biogas and composting plants (Fig. 2). Aspects of the agricultural system which were assumed to be unaffected by changes in co-product management, such as pesticide use or energy production from solar systems and agrivoltaics, were outside the system boundaries for this analysis.

#### 2.2.1. Agricultural components represented in the model

In each region, a selection of most important crop and livestock types was included in the model. Crop areas were obtained from regional agricultural census data, excluding crop types with small area (e.g. vegetable crops or beans in NL) or crops with no data available needed to quantify the regional N balances (e.g. fruit orchards in SC). Livestock activity data was obtained from regional agricultural census data, aligned to match the livestock categories used by Eurostat. These categories were required for quantification of the livestock N balances (Section 2.2.2), but the corresponding livestock numbers were unavailable because the selected regions in this study did not fully match the Eurostat’s geographical regions. This meant that some regional census livestock categories needed to be merged to match the Eurostat categorisation. Livestock numbers and crop area of the selected livestock and crop types in this study are provided for each region in Supplementary Information (SI-Tables 1 & 2).

#### 2.2.2. Quantification of nitrogen flows

First, the model quantified the amount of N in key biomass flows through the regional agricultural system (Fig. 2). Model components include soil, food- and fodder crops, livestock, manure storage and a biogas and a compost plant. All in- and outflows and flows between compartments were quantified. The entry point for parameterizing the model was to incorporate region specific data as much as possible, capturing both biophysical (e.g. climate, soil type) and management (e. g. type of fertiliser, model of manure application) differences between regions in the model. However, to ensure a consistent data collection methodology across all regions - while being as region specific as possible - a combination of region specific, country specific, and broadly applicable data was used. This approach minimizes the risk of variation in model outcomes due to methodological differences. All parameter values and corresponding literature sources can be found in SI-Tables 3–5.

In the livestock component of the model, the N flows (N in feed, milk, meat, and excretion) were fixed per livestock type. Hence, the types and total number of livestock in each region determined the total feed requirements, N in milk and meat, and total N excreted. Livestock feed N intake, production, and excretion were based on country specific statistics of feed-use, energy and protein requirements, and livestock production data collected by Eurostat (Hou et al., 2016). These country specific values for feed use, production, and N excretion were assumed
<figure><img src="image_7.png" /><figcaption>**Fig. 2.** Conceptual framework of the model used. (Adapted from Vonk et al. (2025)).</figcaption></figure>

to be representative of the regional animal production efficiencies. Manure and urine N excretion can be deposited during grazing or collected in storage, both prone to gaseous N losses quantified with IPCC (N₂O) and European environmental agency (EEA) emission factors (NH₃). Most housing systems were based on slurry manure, where urine and solid manure are mixed in storage, but solid systems were also included for Scotland and France. The manure collected in storage can be treated with anaerobic digestion, also leading to some NH₃ losses. The manure or digestate left after subtraction of losses during storage was assumed to be available for application to the field, an input to the crop compartment of the model Next to livestock manure, crop residues and household organic waste can also be digested anaerobically and are then available for application in the crop compartment. During the digestion process, organic carbon is converted into methane (CH₄), and part of the organically bound N is mineralised into ammonium and nitrate. Methane production and N mineralisation during anaerobic digestion depend on the substrate quality, quantified using a C and N mass balance approach with parameters for carbon biodegradability and N mineralisation potential obtained from the SYS-Metha model (Bareha et al., 2021). The production of household green waste biomass was based on a country specific average green waste production per inhabitant, multiplied by the number of inhabitants in each region (Favoino and Giavini, 2024). Household green waste could also be composted, also leading to C and N losses quantified using emissions factors from EEA and IPCC. Manure, digestate, and compost which are left after subtraction of losses during storage and/or treatment are available for application to the field.

In the crop compartment, all available organic amendments are distributed equally among all crops. Manure available for application was equal to the manure excreted by housed livestock in the region. Manure and urine excreted during grazing is directly left on grassland used for grazing, assuming that all permanent and ley grasslands are grazed with equal intensity. Manure and digestate application was bound to (legal) maximum allowed N (and P when in place) application rates. Synthetic fertiliser was then added until the region and crop

specific maximum application norm was reached. This means that more synthetic fertiliser will be used if there are less organic amendments available. When there was no application norm in place, recommended rates were used as maximum for synthetic fertiliser application. N losses from organic and synthetic fertilisation or soil amendments were quantified using IPCC (N₂O) and EEA (NH₃) emission factors, accounting for regional differences in climate, mode of manure application, and synthetic fertiliser type. For example, sod injection of slurry manure was assumed as most common application mode in L-DK, which is partly in and partly on top of the soil, while we assumed injection in D-NL which is only beneath the surface, both with different NH₃ emission factors. Crop yields were quantified with region specific yield response curves to allow crop yields to change under different N fertilisation regimes. Nitrogen from synthetic fertiliser and organic amendments (manure, digestate and compost) was converted into first-year effective N using fertiliser replacement factors which are based on mineral N content of the organic amendment and the mode of application. Another N input was N fixation by legume crops and grassland, here based on crop yield and a crop specific fraction of total N which is fixed by rhizobia (Herridge et al., 2008). More details about the quantification of N flows can be found in Vonk et al. (2025).

### 2.2.3. Indicators for productivity and the environment

Multiple specific indicators were derived from the calculated N and associated biomass flows, including food N production (total N in crop and livestock products produced in the region), GHG emissions, the agricultural energy balance consisting of consumption and production of energy, effective organic matter (EOM) inputs to the soil, soil N surplus, and total regional N losses. Food N production, soil N surplus, and total regional N losses were derived directly from the calculated N flows. The other indicators were derived from the N balances and activity data (i.e. crop area and livestock population) using conversion factors. A detailed description of the model and indicators including equations is available in Vonk et al. (2025). In summary, GHG emissions were based on IPCC emission factors for CH₄ and N₂O emissions, converted into CO₂
equivalents using their global warming potential (GWP-100) (IPCC, 2021). Carbon dioxide emission from the direct use of fossil energy was also included, based on diesel use per ha on cropland and average energy use in keeping livestock. Indirect energy use also included energy use to produce synthetic N fertiliser (Kränzlein, 2008), and the energy required for the production, transport, and processing of imported feed (GLFI, 2023). Transport within the region was not included. Methane emissions from enteric fermentation, manure storage, biogas production (due to leakage and cleaning of the installation), and compost plants were included (Fig. 2). Furthermore, N₂O emissions from manure storage, grazing, application of organic amendments, application of synthetic fertiliser, decay of crop residues left in the field and production of compost were quantified (Fig. 2).

Changes in the supply of organic matter is quantified from the amount of (above- and belowground) crop residues and organic amendments applied to the soil and multiplied with a humification co-efficient to derive amounts of effective organic matter input, which is the organic matter still present in the soil one year after application. Nitrogen flows in manure, compost, and crop residues (the basis of the modelling approach) were converted to organic matter using standard values for N and organic matter content of the co-products. For digestate, organic matter content was calculated based on a mass balance approach to account for the amount of C which is converted into CH₄ and CO₂ during digestion to make sure that the organic matter concentrations of the digestate aligned with their untreated substrates.

## 2.3. Co-product use options

The same co-product use options were compared for all four regions (Fig. 3), focussing on practices and techniques which are currently available, but not per se implemented at scale in each region. For manure, field application of manure (the reference co-product use) was compared to anaerobic digestion of manure and subsequent application of digestate. Only manure which was considered available for digestion was treated, so this excludes grazing manure. Crop residues were either removed from the field (reference), retained in the field or anaerobic digested and later applied to the field as digestate. Only crop residues were considered which can practically be removed from the field. Residues from potato for example are never removed from the field or treated. This means that only crops with a straw-like crop residue (e.g. wheat, barley, sunflower, oil seed rape) are considered in the scenarios, while other major crop residues from e.g. potato or sugar beet always remained in the field. Household organic waste is removed and not used in agriculture (reference), composted and then applied as compost to the field, or digested anaerobically and applied as digestate to the field.

# 3. Results

## 3.1. Co-product availability across regions

The agricultural systems in Drenthe and the Limfjord catchment have the highest stocking density and the highest number of housed livestock compared to the livestock in Ariège and Fife. Therefore, on average, there was more manure available per hectare of agricultural land in Drenthe and the Limfjord catchment (Fig. 4, note that available manure excludes excretion during grazing). Crop production in the Limfjord catchment and Fife consists of relatively large shares of cereals, and therefore these regions produced more crop residues, mainly straw. In terms of N, the share of household organic waste was relatively small in all regions when compared to manure and crop residues. Household organic waste production was the largest in the more densely populated regions (i.e. Fife & Drenthe).

## 3.2. Regional similarities and differences in performance of co-product use options

Manure digestion generally resulted in the largest reduction of GHG emissions (ranging between -2.0 % and -19.8 % in the four regions) compared to the reference due to strongly reduced methane emissions (Fig. 5), with a clear trade-off with EOM inputs to the soil (between -1.1 % and -25.3 %). Crop residues, generally with a higher C:N ratio than manure, showed the largest potential to improve the agricultural energy balance when used for anaerobic digestion (between +11.1 % and +195.5 %) or increase the EOM inputs to the soil when all retained in the field (between +2.8 % and +15.9 %). Household organic waste did not have a large effect on regional GHG emissions, but would either produce some biogas energy when digested (between +3.1 % and +8.2 %), or some additional EOM when composted (between +2.5 % and +4.9 %).

The impacts of the co-product management options depended on the regional context (Fig. 5). In Drenthe and the Limfjord catchment, the improvement of the net energy balance (total energy consumption - production, Fig. 5) from anaerobic digestion of manure was larger than in A-FR and F-SC. The reduction in GHG emissions following manure digestion was similar in D-NL and L-DK.

The largest improvement of the net agricultural energy balance was observed in F-SC following the anaerobic digestion of crop residues. Remarkably, the improvements of the energy balance in percentage by digestion of all crop residues were similar in L-DK and A-FR (Fig. 5), despite large differences in crop residue amounts. In L-DK, biogas from crop residues and the total agricultural energy consumption (mainly due to more energy demanding livestock production) were nearly twice as large when compared to A-FR. In Drenthe (D-NL), only small amounts of crop residue biomass were available resulting in minor effects on both energy production and EOM inputs to the soil compared to the other regions.

<figure><img src="image_8.png" /><figcaption>**Fig. 3.** Co-product types and alternative use options analysed in this study. The co-product uses in the reference scenario are highlighted in grey (Ref).</figcaption></figure>
<figure><img src="image_9.png" /><figcaption>Fig. 4. Co-product availability (in kg N ha⁻¹ of agricultural land) of the three selected co-products in the four case study regions.</figcaption></figure>

There were small regional differences in the outcomes of the household organic waste use options because there were only small amounts of waste available in all case study regions – be it slightly more in D-NL and F-SC than L-DK and A-FR – compared to the other co-products (Figs. 4 & 5).

### 3.2.1. Manure – direct application and anaerobic digestion

In all regions, NH₃-N and N₂O-N losses from storage were lower with daily removal of manure and anaerobic digestion compared to longer storage and direct application of untreated manure (Fig. 6, Storage). This effect was larger in the regions with more manure available (L-DK and D-NL). On the contrary, N losses from application were sometimes higher with anaerobic digestate than with direct manure application (Fig. 6, Application). There was more ammonium and nitrate N in digestate due to breakdown in the organic matter during digestion and less losses during the storage of digestate when compared to manure. Therefore, there was more N available to apply in the anaerobic digestion scenario, leading to more NH₃-N and NO₂-N losses from digestate application. However, in Drenthe, this did not result in higher organic N application rates with respective N losses, because the quantity of organic manure or digestate applied reached the legal limit. The surplus manure and digestate was assumed to be exported from the region. In the other countries, manure availability was always below the legal application limit, even when all the manure was digested.

In the anaerobic digestion use option, the NH₃-N losses from synthetic fertiliser generally decreased (Fig. 6, Application) due to lower synthetic fertiliser N application rates. Lower synthetic fertiliser application rates were observed because digestate contains more first-year effective N compared to untreated manure. Drenthe had less application NH₃-N losses per hectare compared to the Limfjord catchment, despite a higher manure application rate, caused by the different mode of application.

A major benefit of treating manure with anaerobic digestion is the production of biogas energy. At regional level, the largest differences between direct application and anaerobic digestion of manure were observed in Drenthe and the Limfjord catchment which have more manure available (Figs. 4 & 7B). In addition to the production of biogas energy, slightly lowered indirect energy consumption also contributed to an improved net energy balance, caused by the decrease in synthetic fertiliser application. Furthermore, total regional GHG emissions were reduced due to lower CH₄ emission from anaerobic digestion compared to losses during storage of untreated manure. In Drenthe and the Limfjord catchment, total GHG emission reductions per hectare were larger compared to Ariège and Fife which have lower stocking densities.

Food N production was hardly affected by treating manure with anaerobic digestion in all regions. A reduction in EOM inputs to the soil was observed in all regions, because the organic matter content of digestate was lower than untreated manure. Relative to the other regions, an even larger reduction in EOM inputs was observed in Drenthe because the legal placement limit of digestate was reached. Therefore, a small part of the digestate needed to be exported outside of the region. For the same reason, the soil N surplus decreased in Drenthe, but not in

the other regions. In Fife, the decrease in total EOM inputs was the smallest, because the least amount of manure was treated there.

### 3.2.2. Crop residue - remove from the field, retain in the field, anaerobic digestion

Only minor changes were observed when considering specific emissions from the decay of crop residues. Retaining residues in the field slightly increased the field N₂O emissions, compared to removal or digestion of crop residues (Fig. 8). NH₃-N losses from crop residues were slightly higher in D-NL compared to the other regions, mainly originating from decaying sugar beet leaves. With anaerobic digestion of crop residues, there are some NH₃-N losses from the storage of digestate (ranging between 0.1 and 0.7 kg N ha⁻¹ in all regions). When compared to total regional N losses, the impact of crop residues made negligible difference (Fig. 9F).

Similarly on regional level, food N production and GHG emissions were hardly affected (Fig. 9) with the alternative use of crop residues. However, biogas from anaerobic digestion of crop residues was found to produce a considerable amount of energy in the regions with relative more crop residue available (L-DK and F-SC). In Ariège, Fife, and the Limfjord catchment, digesting crop residues produced even more energy than anaerobic digestion of manure. On the other hand, retaining crop residues was effective in increasing EOM inputs to the soil, while anaerobic digestion of the residues decreased the EOM input to the soil (Fig. 9D). In the regions with more crop residue available (F-SC and L-DK), soil N surplus slightly increased when retaining crop residues and slightly decreased with anaerobic digestion of crop residues (Fig. 9E). In the regions with less crop residues available (A-FR and D-NL), soil N surplus remained unaffected in all use options.

### 3.2.3. Household organic waste – not used, composting and anaerobic digestion

While there were differences in specific N losses between composting and digesting household organic waste, the regional total effect is negligible because of the low availability of household organic waste (Fig. 4). In all regions, composting led to a smaller increase in N losses than anaerobic digestion of household organic waste (Fig. 10). While the production and storage of compost resulted in some N₂O emissions which do not occur with anaerobic digestion, compost leads to lower NH₃ emissions after application. On the other hand, total GHG emissions of composting are larger than anaerobic digestion. This difference caused by the production of N₂O and CH₄ during the production of compost (Fig. 10).

At regional level, the differences between composting or anaerobic digestion of household organic waste were negligible. Total regional GHG emissions and food N production were hardly changed between use-options and relatively little total biogas energy was produced by anaerobic digestion of household organic waste (Fig. 5). By composting household organic waste, a small increase in EOM inputs to the soil could be reached which was not the case with anaerobic digestion. The percentage increase in EOM input when applying composted household organic waste varied between countries due to the initial EOM input
<figure><img src="image_10.png" /><figcaption>**Fig. 5.** Effect of regional context on the percentual change in greenhouse gas (GHG) emissions, energy balance and effective organic matter (EOM) inputs to the soil in all scenarios compared to the reference use option ("Ref" in Fig. 3: Direct application of manure, Removal of crop residues & Not using organic waste in agriculture).</figcaption></figure>

level (Fig. 5). In Ariège (A-FR), the increase was larger than, for example, in L-DK, because the French region had relatively less EOM input from crop residues in the reference situation (Figs. 7D & 8D).

# 4. Discussion

## 4.1. Regional co-product availability largely determined differences between co-product use options

The analysis of co-product use options in four European regions and the related environmental effects showed that the outcomes were mainly

driven by regional differences in co-product availability. Larger availability of co-products generally meant that alternative use had a greater effect on the indicators. To a lesser extent, other specific regional characteristics also influenced the results. Regional differences in co-product availability were caused by differences in livestock density (manure), cropping system (crop residues), and population density (household organic waste). Similarly, Bedoić et al. (2019) found that industrialised countries in western Europe, with high population density and relatively little land per capita, produced more animal co-products, whereas cereal production in central and eastern Europe generated more plant-based co-products. For example, by applying our model which
<figure><img src="image_11.png" /><figcaption>Fig. 6. Nitrogen losses related to storage (left) and application (right) of manure and digestate. NH₃-N and N₂O-N losses are indicated in kg N ha⁻¹.</figcaption></figure>

quantified and evaluated co-product availability, it was found that in Drenthe and the Limfjord catchment, the improvement of the net energy balance (Fig. 5) from anaerobic digestion of manure was larger than in Ariège and Fife, because more manure was available for digestion in the former regions. Similarly, retaining crop residues or applying compost from household organic waste was most effective to increase EOM inputs to the soil in regions which produced more crop residues or household organic waste (Figs. 4 & 5).

Next to co-product availability, other regional differences also affected indicator results in absolute or relative terms. An example is the effect of the manure management system on GHG emissions. Despite that Drenthe had more manure available for digestion, the reduction in GHG emissions following manure digestion was similar to the Limfjord catchment (Fig. 7C). Slurry based manure systems are the prevailing system in the Limfjord catchment, with anaerobic conditions which favour methanogenesis, while considerable amounts of dry poultry manure are produced in Drenthe with less CH₄ emission (Chadwick et al., 2011). Despite that the absolute effect of changed co-product use may sometimes appear small, it could still be relevant. Namely, other regional characteristics lead to a relative difference in results between the regions, such as the effect of using household organic waste for anaerobic digestion to improve the net energy balance in Ariège and Drenthe. While there was more household organic waste available in Drenthe, the improvement in the net energy balance compared to the reference use was larger in Ariège because the region has less livestock and therefore lower energy requirements (Figs. 4 & 5). The same applied to the increase of EOM inputs to the soil when composting household organic waste, i.e., the increase (compared with the reference) was larger in Ariège than in the other regions, because crops in Ariège receive less organic inputs and have lower crop residue yields.

## 4.2. Trade-offs between net energy balance, GHG emissions, EOM inputs and total N losses

Options for alternative co-product use showed considerable - sometimes synergetic - effects on indicator outcomes at regional level, but some important trade-offs between indicators were also identified. Anaerobic digestion of manure reduced regional GHG emissions and total N losses, while producing energy that improved the net agricultural energy balance. Environmental effects of treating manure with anaerobic digestion have previously been reported, such as reduced CH₄ losses from storage (e.g. Clemens et al., 2006; Sommer et al., 2009), and reducing NH₃ emission by regular removal of manure and storing digestate in closed tanks (e.g. Möller, 2015). We also found that anaerobic digestion of regionally available manure led to a significant reduction in effective organic matter inputs to the soil. While some found that this could reduce long-term carbon sequestration (Nyang'au et al., 2022), others found no evidence of decreased soil C sequestration

(Möller, 2015), suggesting that C losses during digestion are compensated by lower C decomposition after application to the field when compared to untreated manure. Reduced organic matter inputs may possibly have a negative effect on soil life, biodiversity and soil productivity in the long-term, be it via active or relatively stable soil organic matter (Schjønning et al., 2009; Lal, 2016). However, reduced organic matter inputs did not lead to a large reduction in crop production in our model, despite that N supply from the soil to the crop was dynamically linked to organic N in soil amendments, following the approach of Vonk et al. (2025). Another important reason for minimal changes in crop yields was allowing synthetic fertiliser use to compensate for reduced organic N inputs, which was chosen to best reflect current farming practice. When fertiliser use would have been kept constant when analysing co-product use options with less organic fertiliser available, crop production would decrease (Pinsard, 2025). N application from organic fertilisers as fraction of total N applied increased with anaerobic digestion, which reduced synthetic fertiliser dependency. This effect was smaller in Drenthe (NL), where not all digestate could be applied in the region as there was not enough legal placing space left to utilise the additional N available when all manure was digested.

Digestion of crop residues showed large potential to produce energy, improving the net agricultural energy balance. Retaining crop residues on the soil did not produce energy, but was the most effective use-option to increase EOM inputs to the soil. Potential indirect effects (e.g. GHG emissions and EOM soil inputs elsewhere) after first exporting the residues outside the region (as was the case in the reference) were not assessed in this study. The overall effect on EOM inputs to soils may therefore be different than shown in this study, for example when straw is exported from the region for mushroom production elsewhere and returns as compost. The large potential for biogas energy production from crop residues is mainly due to the larger carbon content when compared to slurry manures. In this study, digestion of manure, crop residues, and household organic waste were assessed as separate options. Often, several feedstocks are mixed in anaerobic digestion plants to obtain optimal composition of feedstock (C:N ratio, water content) for biogas extraction (Angelidaki and Ellegaard, 2003). In our model, standard values for feedstock characteristics and simple equations to account for changes in C and N concentrations from feedstock to digestate during anaerobic digestion were used, and is therefore well suited to explore systems with anaerobic digestion. More detailed models are available to predict biogas yields, but those often require more parameters or provide little information on the digestate residues and were therefore not suited for our analysis (Bareha et al., 2021).

The effects of alternative uses of household organic waste on the indicators were smaller than manure or crop residues, because only limited quantities were available in all regions when compared to the quantity of manure or crop residues. While we quantified potential availability of household organic waste, suitable for explorative
<figure><img src="image_12.png" /><figcaption>**Fig. 7.** Modelled regional scale impacts for direct application of manure or anaerobic digestion of manure with application of the digestate, in the four regions (Ariège (A-FR), Drenthe (D-NL), Fife (F-SC), and the Limfjord catchment (L-DK)). (A) food and fodder production; (B) the energy balance; (C) greenhouse gas (GHG) emissions; D) effective organic matter (EOM) inputs; (E) soil nitrogen (N) balance and (F) N losses.</figcaption></figure>

comparisons between regions, the actual availability might be different
due to the lack of collection and processing infrastructure or contami-
nation with plastics or heavy metals (Manea et al., 2024). Household
waste comprises the largest share (~65%, Gilbert and Siebert (2022)) of
the organic waste feedstock for composting and digestion in Europe, but
there are other important sources, such as municipal (e.g. roadside
clippings, tree cuttings) or commercial organic waste, which were not
included in this study. Those account for around 26 % of total organic
waste feedstock in Europe (Gilbert and Siebert, 2022). The limited
available household organic waste may still produce some energy when
digested, or provide some additional EOM inputs to the soil when
composted. While Razza et al. (2018) found that increased EOM inputs
from compost application of 35 t/ha would considerably increase long-
term carbon sequestration and soil quality, the effect will be much
smaller with average application rates that are based on the actual
availability of compost from household organic waste (0.4–1.3 t/ha in

our regions). Despite that both alternatives, composting and digestion,
come with additional GHG emissions and/or N losses, these trade-offs
with energy production and EOM inputs were only minor at regional
level. In our reference, GHG emissions related to using organic house-
hold waste outside agriculture were not included in the model. Yet,
other use options like landfill or using household waste for feed would
lead to more GHG emissions compared to composting or digestion,
especially when energy produced with digestion is assumed to (partly)
avoid fossil energy use (Yoshida et al., 2012; van Selm et al., 2025). The
reductions in the imports of synthetic fertiliser were negligible when
using the regionally available compost or digestate from household
organic waste. Others also suggested that recycled household organic
waste can only replace a limited part of agricultural N inputs, even in
urban regions which are net importers of food products (Tamsma et al.,
2024), as most consumed and excreted N by humans is lost via sewage
streams in wastewater treatment facilities.
<figure><img src="image_13.png" /><figcaption>**Fig. 8.** N losses specifically related to crop residues (kg N ha⁻¹) for removal of crop residues from the field, retain crop residues or use crop residues for anaerobic digestion, in the four regions: Ariège (A-FR), Drenthe (D-NL), Fife (F-SC), and the Limfjord catchment (L-DK).</figcaption></figure>

### 4.3. *Model improvements and future research*

Making use of an explorative summary model for regional N flows and publicly available, generic data allowed us to compare co-product use options in different European regions with crop and livestock production. However, this approach limited us to use best available data and methods, which were specific for the individual regions.

Regional specific parameter data were required to assess differences between regions, but limited data availability restricted the differences that could be analysed. Therefore, more general values were sometimes applied to ensure that methodological differences would not influence the model outcomes. Using identical parameters across regions only, however, would make it impossible to compare regions. Applying a combination of more specific and general parameters allowed to capture regional differences in biophysical (e.g. the effect of climate on the N₂O emission or NO₃ leaching) and management characteristics (e.g. effect of N rate on crop yield, mode of manure application on NH₃ losses), but not in all parameters. For example, ammonia emission from manure application depended on the mode of application (i.e. injection, band application, surface spreading), while only a broad distinction between wet and dry climates was made for N₂O emissions from manure application. However, N₂O emission generally increases with injection compared to surface band application (Herr et al., 2019). Other bio-physical aspects, such as occurrence of soil freezing–thawing cycles that could lead to considerable N₂O emission differences between regions (Jungkunst et al., 2006), were also not reflected in the emission factors used.

The methods chosen in this model were also not always the best available, but more suitable for explorative comparison of multiple regions and scenarios. For example we chose to assume equal manure distribution across the entire region, while transport is considered a limiting factor in Ariège for distributing manure to fields further away in the region (Ryschawy et al., 2022). Using farm and field data would allow the spatial variation within the region to be analysed (Kros et al., 2019), possibly leading to different total emissions. To illustrate, wet spots in a region may cause considerably local N losses from denitrification with large GHG emissions, while the average groundwater tables for the region may be deep enough to strongly limit denitrification (Wolf et al., 2005). The same non-linear effect may be true for N leaching hotspots due to N overapplication in certain fields (Gao et al., 2016). Using spatially more detailed data would also allow a better assessment of the import and export of manure. However, we assumed each region utilised its manure to the maximum potential and only exported surplus manure, not allowing the importation of manure from other regions. Furthermore, we based livestock N excretion and production on country level data and Eurostat animal categories (Hou et al., 2016), as regional

estimates were scattered and not always derived using the same methodology. Scaling the country level estimates for N excretion and production according to the livestock numbers at regional level was difficult because uncertainties existed about the precise definition of each livestock category. Also, country-specific estimates for average N fixation in grassland were difficult to obtain, so we opted to use the same value in all regions.

Modelling on higher aggregation levels comes with larger uncertainties (Heuvelink, 1998; Rahimi et al., 2024), while possibilities to verify outcomes are limited. Previously, sensitivity of our model was assessed by looking at the response to changes in parameter values (Vonk et al., 2025). The sensitivity of the model output was quantified by changing one parameter at a time (1 % increase and decrease) and calculating the elasticity index for each parameter-indicator combination. It was found that several indicators were most sensitive to changes in the crop N content and fertiliser response parameters, including food N production, GHG emissions and N losses. Modelled crop yields and fertilisation rates were further checked by personal communication with researchers and statistics from each region. Response curves were slightly modified when crop yields or fertilisation was not matching regionally reported data (SI-Table 3).

This study focused on assessing the alternative use of selected co-products as fertiliser, soil amendment, and feedstock for energy production, and explored the effectiveness of such measures on environmental and productivity indicators. However, an array of other alternative use options (e.g. feed, bio-materials) and relevant co-products (e.g. food industry waste, cover crop biomass) exist, with different effects on productivity and/or environment that could be part of future research. For example, van Selm et al. (2025) found that using consumer waste as animal feed was most effective when aiming to reduce total agricultural land-use, while digestion or composting reduced GHG emissions more. Cover crops or winter cereal grazing has gained interest in Ariège and Fife, and can potentially improve livestock feed autonomy while also providing soil quality benefits (Blanco-Canqui et al., 2015; Planisich et al., 2021). Furthermore, co-products from vegetable and fruit production were not considered in this study. However, Bedoić et al. (2019) pointed towards an important link in countries which produce both animal products and vegetable co-products, such as in the Netherlands and Belgium, often reusing vegetable waste-streams as animal feed. Economic aspects of co-product use were also not assessed in this study, while it has been identified an important driver for farmers. For example in the case of cereal production, farmers may more easily sell their straw when the price is good, perhaps even choosing to increase the production of straw at the detritum of crop yield (Townsend et al., 2018).

The alternative co-product use options that were assessed as single
<figure><img src="image_14.png" /><figcaption>**Fig. 9.** Regional scale impacts for removal of crop residues from the field, retain crop residues or use crop residues for anaerobic digestion, in the four regions (Ariège (A-FR), Drenthe (D-NL), Fife (F-SC), and the Limfjord catchment (L-DK)). (A) food and fodder production; (B) the energy balance; (C) greenhouse gas (GHG) emissions; D) effective organic matter (EOM) inputs; (E) soil nitrogen (N) balance and (F) N losses.</figcaption></figure>

<figure><img src="image_15.png" /><figcaption>**Fig. 10.** N losses and GHG emission specifically related to compost and anaerobic digestate from household organic waste, in the four case study regions: Ariège (A-FR), Drenthe (D-NL), Fife (F-SC), and the Limfjord catchment (L-DK).</figcaption></figure>
measures did not reduce emissions enough to reach proposed regional reduction targets for agriculture in Drenthe (reduction of 41 % for NH₃ and 49 % for GHG emissions, Ros et al. (2023)). In our study, treating all available manure in Drenthe with anaerobic digestion came closest towards reaching the target reductions, with a 19.8 % reduction in GHGs and a 37.1 % reduction in NH₃ emissions. To fully reach the targets, measures for alternative use of co-products must be combined with more structural changes such as a reduction in the regional livestock population.

## 4.4. Conclusion

In this study we show that regional context determined availability of co-products and affected the performance of alternative co-product use options. The presented modelling study combined the quantification of regionally available co-products with an assessment of different use options. Changed manure management was found to be most effective to reduce environmental impact of agriculture in livestock-dense regions, while the effects of crop residues and household organic waste were relatively small. Digestion of manure was most effective to reduce GHG emissions, but had a trade-off with EOM matter inputs to the soil. Crop residue management was important in regions with a relatively large acreage of cereals. Digesting crop residues significantly contributed to improving the net agricultural energy balance, but was also most effective to increase EOM inputs to the soil when retained on the field. Household organic waste is a relatively small biomass stream in each region, but may either produce some energy (anaerobic digestion) or additional soil carbon inputs (composting). Other regional differences like animal type, and manure storage system were also found to be important regional contextual factors.

Increasing self-sufficiency of food and feed has been a recurring subject of debate in the European Union after COVID-19 and geopolitical conflicts. There is an increasing demand for biomass from the region, ranging from soil amendment or feed to biomaterials and renewable energy sources, some of which could be supplied by better utilising co-products. In the end, each kg of co-product can only be used once. Our modelling approach revealed trade-offs and synergies between different indicators for environmental performance and productivity, important to consider when developing policy guidelines or subsidy schemes to promote best practices without unintended side-effects. In conclusion, the prioritization of co-product utilization should first consider the region-specific co-product availability, while setting clear objectives (e.g., environmental impact, agricultural production, and economic factors) to navigate between trade-offs and synergies.

### CRediT authorship contribution statement

**W.J. Vonk:** Writing – review & editing, Writing – original draft, Formal analysis, Data curation, Conceptualization. **A.G.T. Schut:** Writing – review & editing, Conceptualization. **R. Hijbeek:** Writing – review & editing, Conceptualization. **C.F.E. Topp:** Writing – review & editing, Data curation. **M. Grillot:** Writing – review & editing, Data curation. **M.V. Odgaard:** Writing – review & editing, Data curation. **T. Dalgaard:** Writing – review & editing, Data curation. **M.K. van Ittersum:** Writing – review & editing, Conceptualization.

### Declaration of competing interest

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: W.J. Vonk reports financial support was provided by Netherlands Ministry of Agriculture, Fisheries, Food Security and Nature. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

### Acknowledgment

The authors acknowledge the financial support for the MI BICYCLE project through the partners of the Joint Call of the Cofund ERA-Nets SusCrop (Grant N° 771134), FACCE ERA-GAS (Grant N° 696356), ICT-AGRI-FOOD (Grant N° 862665) and SusAn (Grant N° 696231). C.F.E. Topp receives financial support from the United Kingdom Department for Environment Food and Rural Affairs and the Scottish Government Strategic Research Programme. Special thanks go out to all project partners of the MI BICYCLE project for supportive feedback, especially to August Kau Lægsgaard Tidemand from Aarhus University, Lucas Soerensen from INRAE, and Marie Golba Delecourt from the Ariège chamber of agriculture for their help with the regional data collection.

## Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi.org/10.1016/j.scitotenv.2025.180698.

### Data availability

Data will be made available on request.

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