A Review of Trade-Offs in Low ILUC-Risk Certification for Biofuels—Towards an Integrated Assessment Framework

Abstract

Indirect land use change (ILUC) is considered a significant challenge, resulting from an increasing demand for biomass and bioenergy. On a political level sustainability certification of biomass-derived products is discussed as one potential instrument to manage the risk of ILUC. However, extending existing schemes towards a credible and reliable certification approach to account for ILUC-risks is still an open challenge. To develop such a certification instrument, so-called “additionality practices” are gaining relevance. Such practices include measures that an individual producer can adopt to provide an amount of biomass in addition to the business-as-usual feedstock production. This applies in particular to the certification of low ILUC-risk biofuels through voluntary certification schemes recognised by the European Commission. To date, however, no studies have been conducted that examine how such schemes account for potential trade-offs that may arise from the use of additionality practices. In preparation of an integrated assessment framework for low ILUC-risk certification, this study presents a gap analysis that examines whether such trade-offs are considered already in existing sustainability certification schemes for biofuels. In this way, we have found trade-offs that are preferentially addressed by the schemes, e.g., biodiversity loss, on the one hand, and considerable gaps for certain trade-offs, e.g., resource depletion, on the other. In addition, we identified biomass cultivation on unused land as the most promising additionality practice. Most schemes already have certification instruments in place to verify the large number of trade-offs that could be identified as preferentially addressed for this additionality practice. Moreover, only a few new criteria and indicators need to be developed for the small number of gaps found for biomass cultivation on unused land. Finally, this paper recommends future work to verify the scientific evidence of existing certification instruments for the trade-offs addressed and to develop assessment approaches for the identified gaps.

1. Introduction

Direct and indirect land use change (DLUC & ILUC) effects represent significant risks resulting from an increasing demand for biomass and bioenergy, induced by international trade in global markets [1,2]. In international trade, sustainability certification of biomass-derived products can help to understand and verify risks and establish a certain level of sustainability [3]. Product value chains are becoming increasingly complex as a result of globalization and outsourcing [4]. Therefore, standards and certification schemes can play an important role in co-regulated markets to pursue sustainable value chains [5]. Co-regulation is characterised by a combination of sustainability obligations for value chains in specific sectors, legislated by countries, and private control mechanisms (e.g., certification schemes) that allow companies to demonstrate compliance with these sustainability obligations [6]. A prominent example of such a co-regulatory approach is the use of private voluntary certification schemes recognised by the European Commission (EC) to assess biofuels [7]. These biofuels must meet a set of mandatory sustainability criteria, such as the conservation of high-carbon or highly biodiverse land, required to count towards the bioenergy targets set out in the European Union (EU) Renewable Energy Directive (RED) [8]. Therefore, to verify compliance with these sustainability criteria, voluntary certification schemes have been developed, focusing specifically on biofuel and bioenergy production and taking sustainability principles into account [9]. As biofuel consumption increases over time, the role of voluntary certification schemes to account for ILUC effects becomes increasingly important [10].

However, the development of a credible and reliable certification approach to address ILUC is still an open challenge [11]. To develop such a certification instrument, a risk-based approach aimed at certifying biofuels with low ILUC-risk has been discussed at the political and scientific level over the last decade [12]. Finally, at the policy level, the EU RED 2 has set out a low ILUC-risk approach for the certification of sustainable biofuels [13]. As recently reviewed, this approach is characterised by the use of practices that an individual producer can adopt and that aim to reduce ILUC risks by increasing relative efficiency and providing an additional amount of biomass compared to a reference case [14]. To date, however, there are no studies or publications available which analyse what trade-offs might arise from the use of additionality practices and whether and how voluntary certification schemes developed for certifying biofuels address these trade-offs.

In preparation of an integrated assessment framework for low ILUC-risk certification, this paper presents a gap analysis of potential trade-offs that may arise from the use of additionality practices. In this sense, a gap analysis is either a tool or a process for determining the difference between the current state and a desired future state of a system [15]. The following examples show various approaches to gap analysis that are used in research on the sustainability certification of biobased products. For example, Majer et al. 2018 identified relevant gaps in relation to existing certification criteria by comparing the results of a comprehensive literature review on certification schemes and standards with the trends and opinions formulated in expert interviews they conducted [11]. Moosmann et al. 2020 compared the main sustainability risks in the biobased economy identified in an expert survey with an inventory of policy documents on the biobased economy at EU and EU Member State level identified in a desktop research [16]. Mai-Moulin et al. 2021 developed a set of effective sustainability criteria for bioenergy based on a review of the sustainability criteria in the RED 2 and in existing national legislation and voluntary certification schemes, with the aim of identifying possible gaps and good practices in certification [17].

In

Table 1. Abbreviations used in the article. Own table.

Abbreviation	Full Form
2BSvs	Biomass Biofuels Sustainability Voluntary Scheme
AFi	Accountability Framework initiative
AP	Additionality practice
AP Chain integration	Improved production chain integration of byproducts, waste, and residues
AP Increased yield	Increased agricultural crop yield
AP Livestock efficiencies	Improvements in livestock production efficiencies
AP Loss reduction	Reduction in biomass losses
AP Unused land	Biomass cultivation on unused land
BIKE	Biofuels production at low ILUC Risk for European sustainable bioeconomy
CORSIA	Carbon Offsetting and Reduction Scheme for International Aviation
DLUC	Direct land use change
EC	European Commission
EoL	End-of-Life
EU	European Union
GHG	Greenhouse gas
ILUC	Indirect land use change
ISCC	International Sustainability and Carbon Certification
ISEAL Alliance	International Social and Environmental Accreditation and Labelling Alliance
ISO	International Standard Organization
LCC	Life cycle cost
LUC	Land use change
RED	Renewable Energy Directive
RSB	Roundtable on Sustainable Biomaterials
RSPO	Roundtable on Sustainable Palm Oil
RTRS	Round Table on Responsible Soy
SAF	Sustainable aviation fuels
SOC	Soil organic carbon
SQC	Scottish Quality Farm Assured Combinable Crops
STAR-ProBio	Sustainability Transition Assessment and Research of Bio-based Products
SURE	Sustainable Resources Verification Scheme
TASCC	Trade Assurance Scheme for Combinable Crops
UFAS	Universal Feed Assurance Scheme
WHO	World Health Organization

, all abbreviations which we have used in this paper are shown.

1.1. Additionality Practices

Additionality practices are defined as any improvement process, increasing the efficiency of already used resources, and any measure that enables the planned use of previously unused resources for the production of an additional amount of biomass compared to a baseline scenario. In addition, additionality practices avoid displacement effects of existing users and are produced under schemes appropriate for the sustainability certification of low ILUC-risk biomass-derived products (modified from [13,14,18,19]). Table 2 provides an overview of additionality practices that are potentially to be applied in the sustainability certification of low ILUC-risk biomass, identified by the STAR-ProBio project [19] and a recent review of additional literature and practices [14]. For each additionality practice, the authors identified potential methods for implementation and verification in certification practice.

Since the publication of Sumfleth et al. 2020 [14], the EC has adopted an Implementing Regulation on 14 June 2022 that addresses, among other things, criteria for low ILUC-risk certification. It focuses particularly on increased agricultural crop yields and biomass production on unused land, as well as how to demonstrate the additionality of low ILUC-risk biomass. In particular, for increased agricultural crop yield, the regulation proposes so-called “yield increase additionality measures” that economic operators can apply to increase their yields and produce additional biomass eligible for low ILUC-risk certification. These measures are grouped in categories, such as mechanization, multi-cropping, and management. For example, management includes the following additionality measures: (1) soil management, (2) fertilization, (3) crop protection, (4) pollination, and (5) other (to leave room for innovation). Because these measures are intended to increase crop yields without compromising sustainability, the regulation emphasizes the need to consider trade-offs between short-term yield increases and medium- or long-term deterioration of soil, water, and air quality, as well as pollinator populations and the homogenization of agricultural landscapes [20]. The assessment of such trade-offs represents one of the key challenges for low ILUC-risk certification presented in Table 2.

Table 2. Overview of additionality practices (AP) with their main characteristics, an example of an approach for determining the amount of low iLUC-risk biomass, and challenges for certification practice, modified from [14,19]. Own table.

Title of AP	Main Characteristics	Example of an Approach for Determining the Amount of Low iLUC-Risk Biomass	Challenges for Certification Practice	References
AP Unused land 1	Taking an unused plot of land into agricultural production without expanding and replacing existing (biomass) users; Land that has not been used to provide services for a certain period of time in the past (e.g., abandoned, degraded, or marginal land).	Actual amount of harvested feedstock: Definition of unused land; Site-specific investigation to demonstrate unused land status; Assessment of land use rights; Assessment of land cover and land use; On-site audit to verify the results of the site-specific investigation (optional); Determination of amount of low ILUC-risk biomass based on actual yields and the size of the previously unused area.	Assessing potential trade-offs; Avoiding free-riding issue; Defining reliable and reproducible criteria for selection of unused land, applicable worldwide; Demonstrating additionality; Developing tools for the selection of appropriate land; Considering low intensity land users, e.g., shifting cultivation.	[21,22,23,24,25,26,27]
AP Chain integration 2	Increasing the number of products manufactured directly from existing, but inefficiently used or unused biomass; Integrating biomass into other land-based production systems (e.g., livestock feeding), to use existing arable land for biomass production; Applicable in feedstock production (e.g., wheat straw) and biomass conversion (e.g., oilseed meal).	Establishing a positive list of EoL products: Definition of whether a material is an End-of-Life (EoL) product, such as waste; Determination of a feedstock-region combination based on EoL product; Certification scheme publishes a periodically updated positive list including feedstock-region combination; If only a share (%) of the total annual production of the EoL product can be included in the positive list, only this part is low ILUC-risk.	Assessing potential trade-offs; Avoiding free-riding issue; Demonstrating additionality; Developing a single indicator from a variety of partially different approaches; Identifying potential byproduct, waste, or residue streams; Weighing between simplicity and high effort in identifying suitable biomass streams.	[21,22,23,25,26]
AP Livestock efficiencies 3	Increasing the productivity per unit area without taking more land into production (e.g., increase in cattle density per ha); Establishing a livestock productivity baseline to compare that with an above-baseline improved productivity; Amount of biomass produced on land become available from above-baseline livestock productivity could be certified as low ILUC-risk.	Low ILUC-risk potential (cattle production): Definition of a baseline with no change in cattle productivity; Comparison of the baseline with productivity improvements per animal or animals per hectare; Area become available by increasing productivity per unit area; Amount of biomass, which can be produced from this area could be low ILUC-risk.	Adjusting the approach to arable farms cultivating cropland; Assessing potential trade-offs; Avoiding free-riding issue; Demonstrating additionality; Determining baseline livestock productivity and above-baseline livestock productivity; Transferring this approach developed for regional ILUC-risk assessment to an indicator, tailored for certification.	[28]
AP Increased yield 4	Efficiency improvements of an existing area of arable land; Establishment of a baseline crop yield to compare that with an above-baseline crop yield; Above-baseline crop yield and resulting amount of biomass could be certified as low ILUC-risk.	Moving trendline yield: Trendline yield is compared to a dynamic baseline yield, which bases on yields of similar producers in the same region; Trendline moves each year in relation to the actual observed yields; First year trendline based on yields of year 0 and 1; Second year trendline based on yields of year 0, 1, and 2, etc.	Assessing potential trade-offs; Avoiding free-riding issue; Considering yield variations; Demonstrating additionality; Determining baseline yield and above-baseline yield; Selecting an appropriate yield data source.	[21,22,23,24,25,26,29]
AP Loss reduction 5	Increasing the efficiency of a product value chain by reduction of biomass losses to produce additional biomass; Additional amount of biomass is used directly for the production of biobased products that could be certified as low ILUC-risk; Applicable in feedstock production (e.g., post-harvest losses) and biomass conversion (e.g., biorefinery concepts).	Low ILUC-risk potential (post-harvest loss reduction): Definition of a baseline with no change in post-harvest losses (expressed in mass fractions of losses); Comparison of the baseline with a post-harvest loss reduction scenario; Amount of biomass prevented from being lost in the post-harvest loss reduction scenario could be certified as low ILUC-risk.	Assessing potential trade-offs; Availability of consistent data (e.g., post-harvest losses); Avoiding free-riding issue; Demonstrating additionality; Determining baseline and loss reduction scenario; Transferring this approach developed for regional ILUC-risk assessment to an indicator, tailored for certification.	[28,30]

¹ Biomass cultivation on unused land, ² Improved production chain integration of byproducts, waste, and residues, ³ Improvements in livestock production efficiencies, ⁴ Increased agricultural crop yield, ⁵ Reduction in biomass losses.

Table 2. Overview of additionality practices (AP) with their main characteristics, an example of an approach for determining the amount of low iLUC-risk biomass, and challenges for certification practice, modified from [14,19]. Own table.

Title of AP	Main Characteristics	Example of an Approach for Determining the Amount of Low iLUC-Risk Biomass	Challenges for Certification Practice	References
AP Unused land 1	Taking an unused plot of land into agricultural production without expanding and replacing existing (biomass) users; Land that has not been used to provide services for a certain period of time in the past (e.g., abandoned, degraded, or marginal land).	Actual amount of harvested feedstock: Definition of unused land; Site-specific investigation to demonstrate unused land status; Assessment of land use rights; Assessment of land cover and land use; On-site audit to verify the results of the site-specific investigation (optional); Determination of amount of low ILUC-risk biomass based on actual yields and the size of the previously unused area.	Assessing potential trade-offs; Avoiding free-riding issue; Defining reliable and reproducible criteria for selection of unused land, applicable worldwide; Demonstrating additionality; Developing tools for the selection of appropriate land; Considering low intensity land users, e.g., shifting cultivation.	[21,22,23,24,25,26,27]
AP Chain integration 2	Increasing the number of products manufactured directly from existing, but inefficiently used or unused biomass; Integrating biomass into other land-based production systems (e.g., livestock feeding), to use existing arable land for biomass production; Applicable in feedstock production (e.g., wheat straw) and biomass conversion (e.g., oilseed meal).	Establishing a positive list of EoL products: Definition of whether a material is an End-of-Life (EoL) product, such as waste; Determination of a feedstock-region combination based on EoL product; Certification scheme publishes a periodically updated positive list including feedstock-region combination; If only a share (%) of the total annual production of the EoL product can be included in the positive list, only this part is low ILUC-risk.	Assessing potential trade-offs; Avoiding free-riding issue; Demonstrating additionality; Developing a single indicator from a variety of partially different approaches; Identifying potential byproduct, waste, or residue streams; Weighing between simplicity and high effort in identifying suitable biomass streams.	[21,22,23,25,26]
AP Livestock efficiencies 3	Increasing the productivity per unit area without taking more land into production (e.g., increase in cattle density per ha); Establishing a livestock productivity baseline to compare that with an above-baseline improved productivity; Amount of biomass produced on land become available from above-baseline livestock productivity could be certified as low ILUC-risk.	Low ILUC-risk potential (cattle production): Definition of a baseline with no change in cattle productivity; Comparison of the baseline with productivity improvements per animal or animals per hectare; Area become available by increasing productivity per unit area; Amount of biomass, which can be produced from this area could be low ILUC-risk.	Adjusting the approach to arable farms cultivating cropland; Assessing potential trade-offs; Avoiding free-riding issue; Demonstrating additionality; Determining baseline livestock productivity and above-baseline livestock productivity; Transferring this approach developed for regional ILUC-risk assessment to an indicator, tailored for certification.	[28]
AP Increased yield 4	Efficiency improvements of an existing area of arable land; Establishment of a baseline crop yield to compare that with an above-baseline crop yield; Above-baseline crop yield and resulting amount of biomass could be certified as low ILUC-risk.	Moving trendline yield: Trendline yield is compared to a dynamic baseline yield, which bases on yields of similar producers in the same region; Trendline moves each year in relation to the actual observed yields; First year trendline based on yields of year 0 and 1; Second year trendline based on yields of year 0, 1, and 2, etc.	Assessing potential trade-offs; Avoiding free-riding issue; Considering yield variations; Demonstrating additionality; Determining baseline yield and above-baseline yield; Selecting an appropriate yield data source.	[21,22,23,24,25,26,29]
AP Loss reduction 5	Increasing the efficiency of a product value chain by reduction of biomass losses to produce additional biomass; Additional amount of biomass is used directly for the production of biobased products that could be certified as low ILUC-risk; Applicable in feedstock production (e.g., post-harvest losses) and biomass conversion (e.g., biorefinery concepts).	Low ILUC-risk potential (post-harvest loss reduction): Definition of a baseline with no change in post-harvest losses (expressed in mass fractions of losses); Comparison of the baseline with a post-harvest loss reduction scenario; Amount of biomass prevented from being lost in the post-harvest loss reduction scenario could be certified as low ILUC-risk.	Assessing potential trade-offs; Availability of consistent data (e.g., post-harvest losses); Avoiding free-riding issue; Demonstrating additionality; Determining baseline and loss reduction scenario; Transferring this approach developed for regional ILUC-risk assessment to an indicator, tailored for certification.	[28,30]

¹ Biomass cultivation on unused land, ² Improved production chain integration of byproducts, waste, and residues, ³ Improvements in livestock production efficiencies, ⁴ Increased agricultural crop yield, ⁵ Reduction in biomass losses.

As the main contribution to this regulation, a guideline for low ILUC-risk certification has been developed [31]. This is based on a low ILUC-risk methodology and an approach to pilot projects in specific regions to test this methodology [32]. The methodology is derived from the requirements for low ILUC-risk certification of biofuels set out in the RED 2 (see [13]) and the Delegated Act 2019/807 (see [18]) and is developed for yield increase projects and projects that take unused, abandoned or severely degraded land into production. For yield increase projects, a management plan including a dynamic yield baseline and the results of an additionality test is checked in a baseline audit. The additionality test is based on an analysis of the financial attractiveness or non-financial barriers of the project. Projects that take unused, abandoned, or severely degraded land into use must demonstrate the status of the land. For example, an economic operator must demonstrate that the land has been used for food or feed production in the past and that the cultivation of food or feed has ceased for biophysical or socio-economic reasons. In the case of abandoned and severely degraded land, additionality does not have to be verified by means of an additionality test. For other unused areas, however, an additionality test is mandatory [32]. It needs to be noted that the issue of demonstrating additionality and avoiding free-riding are important to any additionality practice, as can be seen in Table 2. In addition, the results of applying the methodology in each pilot project have been published [33,34,35,36,37].

The project BIKE (Biofuels production at low ILUC Risk for European sustainable bioeconomy) published a report on criteria and indicators taking into account the additionality practices of increased crop yield and growing crops on abandoned or severely degraded land for low ILUC-risk certification [38]. In another outcome of this project, a meta-analysis shows that there are significant opportunities in Europe to grow additional, environmentally friendly oil and lignocellulosic crops for biofuels using sustainable agronomic practices to increase the yield of such crops and to grow biomass on unused, abandoned and degraded land [39]. An outcome of the STAR-ProBio project is a practical, user-friendly tool for estimating the ILUC-risk of individual biomass feedstock producers, which also identifies how the use of certain additionality practices, such as increased agricultural crop yields, could substantially reduce this risk [40]. The project GOLD investigates the production of low ILUC-risk biofuels by growing selected high-yielding lignocellulosic crops on contaminated land, which can be attributed to the additionality practice of biomass cultivation on unused land [41].

A recently published study proposes to develop a national strategy to mitigate the risks of ILUC from industrial palm oil expansion in large palm oil producing countries such as Indonesia and Malaysia. To this end, the study proposes an ILUC mitigation approach that could be applied as a novel additionality practice specifically in low ILUC-risk palm oil certification. The approach concerns industrial oil palm farms. The palm oil of these producers could be certified low ILUC-risk if the producer establishes one or both of the following two options: (1) integrating annual crops of small-scale crop farms that have been displaced and become landless as a result of the expansion of large-scale oil palm producers into immature oil palm plantations, and (2) integrating livestock of small-scale livestock farms that have been displaced and become landless as a result of the expansion of large-scale oil palm producers into mature oil palm plantations. With the integration of the displaced small-scale farms in the industrial oil palm farms, these small-scale farms do not need to take new land into production to maintain their production. Therefore, the palm oil produced on the large-scale oil palm farms that integrate displaced small-scale farms does not induce ILUC and can be certified as low ILUC-risk palm oil [42].

The International Sustainability and Carbon Certification (ISCC) considers, as part of the CO₂ emissions mitigation instrument CORSIA (Carbon Offsetting and Reduction Scheme for International Aviation), the following additionality practices: (1) yield increase, (2) cultivation on unused land, and (3) use of byproducts, residues or wastes for low land use change (LUC) risk sustainable aviation fuels (SAF) feedstock production [43].

From the developments described above, we conclude, on the one hand, that there is an urgent need (EU policy framework for low ILUC-risk biofuels) and a high level of interest (research projects, publications, and practical applications of certification approaches for low ILUC-risk biofuels) for the additionality practices studied in [14]. Therefore, potential trade-offs that may arise from the use of these additionality practices are also likely to be of interest to policy makers, researchers, biofuel producers and certification practitioners. On the other hand, the additionality practices identified in [14] currently appear to represent the state of the art for certifying biofuels with low ILUC-risk. In particular, increased agricultural crop yield, biomass cultivation on unused land, and improved production chain integration of byproducts, waste, and residues appear to be of relevance for low ILUC risk policies and certification practices, as the work presented above shows.

1.2. Objective and Structure

This paper aims to determine whether or not voluntary certification schemes recognised by the EC address a particular trade-off that may arise from the use of additionality practices.

To achieve this aim, the next section describes the methodological approach for an inventory of potential trade-offs and a gap analysis. This is followed by the results of the current state of trade-offs considered by sustainability certification schemes, including gaps. Then the findings are discussed, focusing on the usefulness of addressing the identified trade-offs in certification, the quality of the trade-offs identified and recommendations for the evaluation of certification instruments for trade-offs addressed by the schemes and developing certification approaches for the identified gaps. The final section concludes with the study’s contributions to the development of an effective assessment framework for low ILUC-risk certification.

2. Materials and Methods

As shown in Figure 1, we apply a multi-step approach for the gap analysis. In the following sections, each step is described in detail.

2.1. Analysis of Trade-Offs from Low ILUC-Risk Practices in Literature

2.1.1. Literature Review on Trade-Offs

For the inventory of trade-offs, in the first step, we consider the trade-offs identified in the STAR-ProBio project [19] and supplement them with our literature review using the Scopus literature search engine, considering the keywords shown in

Table 3. Keywords used in the literature search for the trade-offs for each additionality practice. Own table.

AP	Keywords
AP Unused land	“assessment” AND “abandoned land” OR “degraded land” OR “marginal land” OR “unused land” AND “conversion” OR “cultivation” OR “expansion” AND “impact” OR “risk” OR “trade-off”
AP Chain integration	“assessment” AND “by-product” OR “co-product” OR “residue” OR “waste” AND “biobased” OR “bioenergy” OR “biofuel” OR “biomaterial” AND “improvement” OR “integration” AND “impact” OR “risk” OR “trade-off”
AP Livestock efficiencies	“assessment” AND “cattle” OR “livestock” OR “pasture” AND “productivity” OR “efficiency” OR “yield” AND “improvement” OR “increase” OR “intensification” AND “measure” OR “practice” AND “impact” OR “risk” OR “trade-off”
AP Increased yield	“assessment” AND “agriculture” OR “arable” OR “crop producer” OR “farm” AND “crop productivity” OR “crop yield” AND “improvement” OR “increase” OR “intensification” AND “measure” OR “practice” AND “impact” OR “risk” OR “trade-off”
AP Loss reduction	“assessment” AND “biomass loss” OR “crop loss” OR “food loss” OR “harvest loss” OR “postharvest” OR “post-harvest” AND “reduction” OR “mitigation” AND “impact” OR “risk” OR “trade-off”

. We only consider peer-reviewed scientific journal articles in English language. To obtain the most comprehensive overview of potential trade-offs, we take into account original studies as well as reviews and meta-analyses.

Given these requirements, we select for a review of the literature those sources that address a trade-off that meets the following definition. A trade-off is an undesirable effect, occurring from the conflict between the primary objective of an additionality practice and the measure that an economic operator applies to implement such a practice. In this sense, the primary objective of an additionality practice is to produce an amount of biomass in addition to the business-as-usual feedstock production for biofuels, and thereby reducing the individual ILUC-risk. The measure, in turn, refers to the way in which such an additionality practice could potentially be realised in the practice of biofuel feedstocks production. This approach is consistent with the proposals for yield increase additionality measures as set out in the requirements for low ILUC-risk certification in the EU Implementing Regulation, as well as the required consideration of potential trade-offs [20].

In the next step, we have inventoried the identified trade-offs in an Excel 2016 spreadsheet for further analysis.

2.1.2. Aggregation of Trade-Offs into Categories

Since the approach described in the last section resulted in a large number of trade-offs, we grouped the trade-offs into 20 categories to keep them to a manageable number. To determine the categories, we grouped the trade-offs based on environmental factors, such as those defined in the Environmental Impact Assessment Directive 2014/52/EU, like population and human health; biodiversity; land, soil, water, air, and climate; material assets and landscape [44]. In cases where we found multiple trade-offs for one category from the same literature source, we considered these studies only once for the corresponding category. For simplicity, this paper will use the term “trade-off” for the trade-off categories in the following.

To analyse the identified trade-offs, we count the number of literature sources that deal with a specific trade-off category.

2.1.3. Differentiation of the Trade-Offs According to Their Frequency in the Literature

We distinguish the trade-offs according to the frequency with which they are addressed in the literature reviewed. For this purpose, we differentiate between trade-offs that are frequently addressed and those that are infrequently addressed. Frequently addressed trade-offs are relevant to more than half of the additionality practices and are addressed in more than three literature sources. In contrast, infrequently addressed trade-offs are relevant to less than half of the additionality practices and are addressed in fewer than or exactly three literature sources.

2.2. Analysis of Voluntary Certification Schemes Recognised by the EC

For the inventory of criteria and indicators, in the second step, we select sustainability certification schemes based on their relevance to the certification of biomass and biofuels sustainability criteria required by the EU renewable energy policy framework. As

Table 4. Analysed voluntary certification schemes recognised by the European Commission (EC) [45]. Own table.

Voluntary Certification Scheme	Type of Feedstock(s)	Type of Fuel(s)	Geographic Coverage	Chain of Custody Coverage	Analysed Standard Documents
Biomass Biofuels Sustainability Voluntary Scheme (2BSvs)	Agricultural biomass (including wastes and residues)	All	Global	Full fuel chain	[46,47]
Better Biomass	Agricultural biomass (including wastes and residues)	All	Global	Full fuel chain	[21]
Bonsucro EU	Sugar cane (including residues)	First-generation bioethanol and advanced bioethanol, (solid) biomass fuels produced from bagasse	Global	Full fuel chain	[48]
International Sustainability and Carbon Certification (ISCC EU)	Agricultural biomass (including wastes and residues)	All	Global	Full fuel chain	[49]
KZR INiG system	Agricultural and forest biomass, wastes and residues	All	Global (primarily Poland)	Full fuel chain	[50,51,52,53]
REDcert	Agricultural biomass (excluding high-ILUC risk feedstocks), waste and residues	All	Global (selected countries for which REDcert has adopted a “country profile”)	Full fuel chain	[54]
Red Tractor Farm Assurance Combinable Crops & Sugar Beet Scheme (Red Tractor)	Agricultural biomass (combinable crops and sugar beet)	Biofuels derived from combinable crops and sugar beet	United Kingdom (primarily England and Wales)	Farm to first intake point	[55]
Roundtable on Sustainable Biomaterials EU RED (RSB EU RED)	Agricultural biomass (including wastes and residues)	All	Global	Full fuel chain	[56]
Round Table on Responsible Soy EU RED (RTRS EU RED)	Soy	Biofuels	Global	Full fuel chain	[57,58]
Scottish Quality Farm Assured Combinable Crops (SQC)	Agricultural biomass (combinable crops)	Biofuels derived from combinable crops	United Kingdom (primarily in Scotland)	Farm to first intake point	[59]
Sustainable Resources Verification Scheme (SURE)	Agricultural and forest biomass (including wastes and residues)	Biomass fuels	Global	Full fuel chain	[60]
Trade Assurance Scheme for Combinable Crops (TASCC)	Agricultural biomass (combinable crops and sugar beet)	Biofuels derived from combinable crops and sugar beet	United Kingdom	Trading, transport, and storage stages from farm gate to first processor	[61]
Universal Feed Assurance Scheme (UFAS)	Agricultural biomass (combinable crops and sugar beet)	Biofuels derived from combinable crops and sugar beet	United Kingdom	Trading, transport, and storage stages from farm gate to first processor	[62,63]

shows, we analyse those schemes that have so far been formally recognised by the EC under the RED 2 (EU 201/2001), as of 22 September 2022 [45].

2.3. Gap Analysis in Certification Schemes

For the gap analysis, we examine whether, in the first step, the criteria and indicators of the voluntary certification schemes address the identified trade-offs. In doing so, we consider a trade-off to be addressed by the schemes under study if we can find at least one certification criterion or one indicator that considers the characteristics of the particular trade-off. In contrast, we evaluate a trade-off as not addressed by the schemes if we cannot find a criterion or an indicator that take into account the characteristics of a trade-off.

2.4. Allocating the Results of the Gap Analysis to the Additionality Practices

In the final step, we map the results of the gap analysis to the individual additionality practices. To do so, we combine the results of the inventory of trade-offs with the findings on whether these trade-offs are addressed in the voluntary certification schemes studied.

3. Results

3.1. Inventory of Potential Trade-Offs

We analysed a total of 179 studies published between 2000 and 2021, which we refer to in

Table A1. References of the reviewed literature dealing with trade-offs grouped by additionality practices. Own table.

Trade-Off	AP Unused Land	AP Chain Integration	AP Livestock Efficiencies	AP Increased Yield	AP Loss Reduction
Atmospheric pollution	[71]	[132,133,134,135]	[92,136,137,138,139,140]	[66,106,141,142,143]
Biodiversity loss	[71,106,144,145,146,147,148,149,150,151,152,153,154]	[155,156]	[92,157,158,159,160]	[66,68,92,106,154,161,162,163,164,165]	[84]
Change in commodity price					[69]
Decline in ecosystem service provision	[71]			[71]
Economic inefficiency	[71,149,166]	[167,168]	[75,92]	[73,169,170]	[100,107,171,172]
Food insecurity			[75,79,173]
Gender inequality			[79,158,174]	[175]
GHG emissions	[71,106,146,147,150,151,176,177]	[81,132,135,178,179,180,181,182,183,184,185,186,187]	[75,136,137,138,139,188,189,190,191,192,193,194,195,196]	[92,104,163,197,198,199,200,201,202]	[111,203,204,205,206,207,208,209,210]
Harm to local population	[71,150,151,211,212,213]	[82,167,214]	[215]		[216]
Hazardous work		[217,218]	[86]		[84]
Human disease		[135,186,217,219,220,221,222,223]	[86,136,138,140,224]	[66,92,106,143,225]	[84,98,208,226,227]
Increased economic expenses	[71,147,150,166,228]	[88,135,178,182,185,220,229,230,231,232,233,234,235]	[92,236,237]	[92,170,238,239]	[100,216,240]
LUC	[71,110,241]		[90,136,192]	[110,169,242]
Livestock disease and abuse			[92,243,244,245,246,247,248,249,250,251]
Resource depletion	[252]	[132,183,186,220,231,235,253,254]	[75,136,188,193,194,196,255,256]	[92]	[69,95,171,257,258]
Soil quality depletion	[71,146,150,163,168,200,259,260,261,262,263]	[104,132,133,134,135,168,178,221,234,264,265,266,267,268,269,270]	[75,92,106,136,137,138,139,150,188,192,194,195,236,255,271,272,273,274]	[66,71,92,97,104,106,143,163,201,202,239,275,276,277]
Spread of resistant pests				[278]	[84,98]
Waste disposal increase			[136]		[100]
Water depletion	[71,200,228,252]	[71,155,156,186,235,254]	[136,193,194,195,279]	[66,102,106,163,202,252,280,281]
Water pollution	[71,146,252,259,282]	[133,134,135,183,186,223,266,283,284]	[136,137,138,139,157,188,192,255,273,285]	[66,71,104,106,143,152,163,202,286]	[84,208,226]

. Of these, about two thirds were published between 2015 and 2021. In our analysis, we were able to identify a total of 108 potential trade-offs associated with the implementation of additionality practices for low ILUC-risk biomass supply. Due to the high number of identified trade-offs, we have grouped them into 20 categories. For each trade-off category, we present a definition and, for illustration, an example in

Table 5. Aggregated trade-offs with a definition, an example, and references to projects or publications that use similar terms, respectively. Own table.

Title 1	Definition 2	Example 3	Reference
Atmospheric pollution	Contamination of the indoor or outdoor environment by any chemical, physical or biological agent that modifies the natural characteristics of the atmosphere.	Increased use of fertilizers to increase crop yields causes tropospheric smog and ozone depletion.	1 [64] 2 [65] 3 [66]
Biodiversity loss	Reduction of any aspect of biological diversity (i.e., diversity at the genetic, species and ecosystem levels) in a particular area through death (including extinction), destruction, or manual removal.	Intensive tillage might result in a potential negative relationship between increased crop production and in-field habitat deterioration.	1 [64] 2 [67] 3 [68]
Change in commodity price	Increase or decrease in the market price of a globally traded product (e.g., food).	A food loss intervention could affect the demand for food (e.g., consumers may not need to purchase as much food) or the supply of food (e.g., producers lose less volume during the production process), both of which could affect market prices	1 [64] 3 [69]
Decline in ecosystem service provision	A negative trend in the benefits that humans derive from ecosystems and that maintain conditions for life on Earth, e.g., provisioning services like food.	Optimizing agricultural production exclusively can lead to functional simplification of landscapes, which in turn limits the ability to provide multiple ecosystem services.	1 [64] 2 [70] 3 [71]
Economic inefficiency	A system, method, or action in which a large portion of the input (e.g., material) is wasted, with the consequence that converting it into a particular output (e.g., product) reduces the revenue.	Increasing the planting density (plant population) as a crop management practice of maize in semi-arid and sub-humid agro-ecological zones in Tanzania has a high probability of economic failure.	2 [72] 3 [73]
Food insecurity	Unavailability of food in sufficient quantity and appropriate quality to meet the need for nutritious food for normal growth and an active and healthy life for a human at all times.	High concentrate consumption by ewes in sheep farming systems, which are human-edible, could threaten food security.	1 [64] 2 [74] 3 [75]
Gender inequality	A situation in which sex and/or gender determine different rights and dignity for women and men, which are reflected in their unequal access to or enjoyment of information, services, justice, resources, benefits, and responsibilities.	As livestock systems become more productive and generate more income, they become more economically attractive to men, and women lose control over assets and the income they generate.	1 [76] 2 [77,78] 3 [79]
Greenhouse gas (GHG) emissions	Emission of gaseous components of the atmosphere that have the property of absorbing the infrared radiation (net heat energy) emitted by the Earth’s surface and radiating it back to the Earth’s surface (greenhouse effect).	Residue removal can cause a decreasing SOC [soil organic carbon], which can lead to a loss in carbon stocks, thus increasing GHG emissions.	1 [64] 2 [80] 3 [81]
Harm to local population	A situation in which the livelihoods, rights of use, and access to resources of local people are affected by the extraction or use of resources and globalised trade of resources or products.	Using agricultural residues to produce biofuels can reduce the number of materials used by smallholder households for cooking and energy generation.	3 [82]
Hazardous work	Working conditions or activities that promote work-related accidents and diseases that may result in loss of life, injury, or other adverse health effects to workers.	The use of contact insecticides in grain storage to reduce post-harvest losses may result in increased direct toxicity to operators and increased risk to worker safety.	1 [64] 2 [83] 3 [84]
Human disease	An impairment of the normal state of a human being that interrupts or modifies its vital functions.	Bioaerosols from intensive livestock farms have the potential to increase asthma prevalence in livestock farmers, and children living or attending schools near such farms.	1 [76] 2 [85] 3 [86]
Increased economic expenses	A positive trend in the amount of money an economic operator needs or uses to do or buy something.	Separately collected organic fraction of municipal solid waste for the production of biofuels can increase production costs of such biofuels.	1 [76] 2 [87] 3 [88]
Land use change (LUC)	Change from one land use category (e.g., forest land, cropland, grassland) to another.	Cultivation of larger quantities of feed needed to increase productivity of beef and dairy products can lead to deforestation.	1 [64] 2 [89] 3 [90]
Livestock disease and abuse	An impairment of the normal condition or an inappropriate treatment of an animal kept by humans for the production of animal products.	Breeding animals designed for high productivity may experience a greater number of health problems (e.g., mastitis in dairy cows).	2 [91] 3 [92]
Resource depletion	The quantity of a non-renewable resource, like fossil fuel or mineral extracted and used, and/or the part of the harvest, logging, catch, and so forth of a renewable resource, like biomass used faster than the resource stock can be replaced.	The less biomass (e.g., post-harvest losses of food) is lost the more food is packed and therefore, more packaging is needed. This in turn increases the demand for resources for the packaging materials and thus accelerates the depletion of resources.	2 [93,94] 3 [95]
Soil quality depletion	A human-induced negative trend in the soil health status resulting in a diminished capacity of the ecosystem to provide goods and services for its beneficiaries.	Monocropping systems that aim to increase crop yields can result in soil degradation through wind and water erosion.	1 [64] 2 [96] 3 [97]
Spread of resistant pests	Increase in pests that are no longer affected by the use of pesticides on agricultural land, or biomass storage and transport due to genetic changes or mutations.	Increased use of synthetic insecticides to reduce post-harvest losses can lead to the development of genetic resistance and promote the spread of treated pests.	3 [98]
Waste disposal increase	A positive trend in the quantity of a substance or object that the holder discard or intends or is required to discard.	Reducing food waste increases the amount of food supplied on the market. This lowers food prices, which encourages the purchase of additional goods. Additional packaging of these goods increases the amount of waste.	2 [99] 3 [100]
Water depletion	Physical shortage of available freshwater resources to meet human and environmental demands in a given area, caused by human activities.	Irrigated farming with the aim of increasing crop yields can result in high water use for crop production, which can significantly reduce available water resources.	1 [64] 2 [101] 3 [102]
Water pollution	Release of substances into subsurface groundwater or surface waters (e.g., rivers) caused by human activities to the extent that the substances impair beneficial uses of the water or the natural functioning of ecosystems.	Excessive application of nitrogen fertilizers to increasing crop yields has negative environmental impacts such as eutrophication of water bodies.	1 [64] 2 [103] 3 [104]

¹ Reference using term or title for similar trade-off; ² Reference for definition; ³ Reference for example.

.

As shown in

Table 6. Number of literature sources that address a particular trade-off, broken down by additionality practices and distinguished in frequently addressed (green fields) and infrequently addressed (blue fields) trade-offs (see references in Table A1). Blank fields indicate trade-offs that are not relevant to the additionality practice in question. Own table.

Additionality Practices	Atmospheric Pollution	Biodiversity Loss	Change in Commodity Price	Decline in Ecosystem Service Provision	Economic Inefficiency	Food Insecurity	Gender Inequality	GHG Emissions	Harm to Local Population	Hazardous Work	Human Disease	Increased Economic Expenses	LUC	Livestock Disease and Abuse	Resource Depletion	Soil Quality Depletion	Spread of Resistant Pests	Waste Disposal Increase	Water Depletion	Water Pollution
AP Unused land	1	13	0	1	3	0	0	8	6	0	0	5	3	0	1	10	0	0	4	5
AP Chain integration	4	2	0	0	2	0	0	13	3	2	8	13	0	0	8	17	0	0	6	9
AP Livestock efficiencies	6	5	0	0	2	3	3	14	1	1	5	3	3	9	8	18	0	1	5	10
AP Increased yield	5	10	0	1	3	0	1	9	0	0	5	4	3	0	1	14	1	0	8	9
AP Loss reduction	0	1	1	0	4	0	0	9	1	1	5	3	0	0	5	0	2	1	0	3

, we found the highest number of literature sources that address trade-offs for the AP Livestock efficiencies and the fewest for the AP Loss reduction. In addition, we can identify trade-offs that are frequently and infrequently addressed in the literature.

As shown in Figure 2 and Figure 3, we can determine that half of the trade-offs are frequently addressed in the literature and the other half are infrequently addressed. In addition, we can identify trade-offs that are of concern to almost all additionality practices, e.g., biodiversity loss, greenhouse gas (GHG) emissions, increased economic expenses. In contrast, there are trade-offs that are relevant to only one or a few additionality practices (the additionality practice to which they are relevant can be found in brackets), e.g., gender inequalities (AP Livestock efficiencies, AP Increased yield), spread of resistant pests (AP Increased yield, AP Loss reduction), livestock disease and abuse (AP Livestock efficiencies).

For the AP Livestock efficiencies, we can find nine and with it the most trade-offs that are frequently addressed. In contrast, our research has shown only four and with it the lowest number of frequently addressed trade-offs for the AP Loss reduction. In comparison, we found eight and with it the highest number of trade-offs that are infrequently addressed in the literature for the AP Livestock efficiencies and the AP Loss reduction. For the AP Chain integration, we are able to identify four and with it the fewest infrequently addressed trade-offs.

3.2. Current State and Gaps Identified

As shown in Figure 4, less than half of the identified trade-offs are addressed in more than half of the certification schemes. This includes the first eight trade-offs in Figure 4 (from biodiversity loss to gender inequality). This, in turn, means that we can reveal more potential trade-offs that are addressed in less than half of the schemes (in Figure 4 from atmospheric pollution to resource depletion). In the latter group, we can also identify significant gaps in addressing particular trade-offs. Increased economic expenses, livestock disease and abuse, and resource depletion are not addressed by any certification schemes analysed.

As shown in

Table 7. Groups indicating how many of the certification schemes studied do or do not address a particular trade-off. Own table.

Group	Number of Schemes	Trade-Offs
Mostly addressed	Addressed by 10–13	Biodiversity loss;
		GHG emissions;
		LUC;
		Decline in ecosystem service provision;
		Soil quality depletion;
		Water depletion;
		Water pollution.
Partly addressed	Addressed by 4–9	Gender inequality;
		Atmospheric pollution;
		Hazardous work;
		Harm to local population;
		Waste disposal increase;
		Food insecurity.
Mostly not addressed (gaps)	Addressed by 0–3	Change in commodity price;
		Economic inefficiency;
		Human disease;
		Spread of resistant pests;
		Increased economic expenses;
		Livestock disease and abuse;
		Resource depletion.

, we can group the trade-offs into three different categories, depending on how many of the certification schemes analysed do or do not address a particular trade-off. In doing this, it resulted in trade-offs that are addressed by the majority of the certification schemes, e.g., biodiversity loss. Other trade-offs are addressed by only a subset of the schemes (partly addressed), e.g., hazardous work. Finally, there are trade-offs that are mostly not addressed by the schemes, representing potential gaps, e.g., economic inefficiency.

3.3. Allocating the Results of the Gap Analysis to the Additionality Practices

As shown in Figure 5, we found that all mostly addressed trade-offs are relevant to the AP Unused land and the AP Increased yield. Of the gaps, only a few trade-offs are relevant to the AP Unused land.

In contrast, our study has shown that only few of the mostly addressed trade-offs in the certification schemes are relevant to the AP Loss reduction. In addition, almost all trade-offs that are mostly not addressed in the schemes are relevant to the AP Loss reduction.

This is followed by the AP Livestock efficiencies and the AP Increased yield, for each of which we can reveal trade-offs that are mostly not addressed in the schemes.

Furthermore, our research has shown that the majority of trade-offs addressed by most of the certification schemes are relevant to the AP Chain integration and the AP Livestock efficiencies. Compared with this, four gaps are relevant to the AP Chain integration.

4. Discussion

4.1. Necessity to Address the Identified Trade-Offs in Sustainability Certification Schemes

Since we have identified a large number of potential trade-offs, the question arises whether there is a need to implement and verify certification criteria and indicators for all trade-offs. To address this question,

Table 8. Potential advantages and disadvantages of extending the analysed voluntary certification schemes to cover the identified trade-offs. Own table.

Advantage	Disadvantage
Increased credibility and reliability of certification schemes through the coverage of additional sustainability topics.	Potentially limited measurability of certain trade-offs (e.g., change in commodity price).
Availability of existing sustainability criteria and indicators for a large number of trade-offs.	Need for specially trained auditors to evaluate the variety of different trade-offs.
Meeting the requirements to account for trade-offs in low ILUC-risk biofuels certification as set out in the EU renewable energy policy framework.	Increase in the complexity of certification standard documents due to large number of criteria and indicators to cover multitude of trade-offs.
Higher market penetration of certification schemes that consider the multitude of potential trade-offs in low ILUC-risk certification.	Potentially large effort for feedstock producers to meet the criteria for the large number of trade-offs.
Comprehensive criteria and indicator sets that are able to address the large number of potential trade-offs in low ILUC-risk certification.	Potentially high costs for certification schemes in developing criteria and indicators for all trade-offs potentially relevant in low ILUC-risk certification.

presents various advantages and disadvantages of extending certification schemes to cover the identified trade-offs.

The STAR-ProBio project emphasizes the need to take potential environmental and social risks into account when developing a low ILUC-risk certification approach that considers the additionality practices examined in this paper [19]. Compared to the STAR-ProBio project, we can identify considerable additional potential trade-offs, e.g., change in commodity price, food insecurity, economic inefficiency.

The BIKE project proposes a set of sustainability indicators to assess the environmental, social, and economic sustainability performances of low ILUC-risk biofuels [105]. According to the authors, environmental trade-offs, such as biodiversity loss, GHG emissions, soil, water, and air quality, as well as economic and social risks, are relevant to the use of the AP Increased yield and the AP Unused land in low ILUC-risk certification. Compared to the indicators developed in the BIKE project, we consider economic trade-offs at a more aggregated level and have identified additional social trade-offs, e.g., food insecurity, gender inequality, hazardous work, and human disease.

According to a paper from the ILUC Prevention Project the AP Unused land, AP Yield increase, and AP Loss reduction could have a significant impact on GHG emissions and other environmental factors such as biodiversity, water, soil, and air [106]. The authors also emphasize the need to analyse trade-offs between environmental and socioeconomic impacts.

Finally, the EU Implementing Regulation specifies that consideration should be given to potential trade-offs that could arise from the implementation of the AP Increased yield and the AP Unused land in low ILUC-risk certification [20]. The regulation emphasizes that the application of additionality practices will not have a negative impact on soil, water and air quality, and pollinator populations, as well as the homogenization of the agricultural landscape.

According to the results of the research projects and the requirements of the EU Implementing Regulation, almost all of the trade-offs we identified are relevant for the production of low ILUC-risk biofuels if the additionality practices we studied are applied. Therefore, we propose to take most of the trade-offs into account when developing a credible and reliable low ILUC-risk certification instrument. However, we especially suggest considering the recommendations on prioritizing the gaps in Section 4.4.2.

4.2. Validity of the Trade-Offs Analysed

4.2.1. Features of the Research Design

Grouping identified trade-offs into categories may, on the one hand, lead to overlaps between trade-off categories, e.g., decline in ecosystem service provision includes other trade-offs such as food insecurity, water pollution, etc. On the other hand, certain trade-offs may be poorly represented because they are grouped under the topic of a trade-off category, e.g., harm to local population covers, amongst others, displacement of smallholder farms, and harm to social structures and local communities.

In some cases, we departed from the methodology for distinguishing frequently and infrequently addressed trade-offs. Among the frequently addressed trade-offs, this concerns livestock disease and abuse. This trade-off is relevant to less than half of the additionality practices (only relevant for the AP Livestock efficiencies) and is addressed in more than three of the literature sources. Among the infrequently addressed trade-offs, there are trade-offs that are addressed in less than or exactly three literature sources but are relevant to more than half of the additionality practices. These are economic inefficiency, harm to local population, hazardous work, and LUC. However, we decided to assign them to the group of infrequently addressed trade-offs because they are addressed in fewer than three literature sources for most additionality practices.

The decision of whether a particular certification scheme does or does not address a trade-off is, in some cases, based on minor differences in the characteristics of a trade-off and the focus of the criteria and indicators required under a scheme. For example, the ISCC considers resource depletion only in terms of energy resource depletion, without considering material resource depletion, which leads us to conclude that this trade-off is not addressed.

Table 9. Uncertainty in deciding whether or not a particular certification scheme addresses a trade-off. Crosses indicate the schemes for which the decision is uncertain. Own table.

Trade-Off	2BSvs	Better Biomass	Bonsucro	ISCC	KZR INiG System	REDcert	Red Tractor	RSB	RTRS	SQC	SURE	TASCC	UFAS
Atmospheric pollution	X						X		X	X
Decline in ecosystem service provision	X						X			X		X	X
Human disease			X	X		X	X	X	X	X		X
Increased economic expenses			X
LUC	X				X	X	X			X		X	X
Livestock disease and abuse							X					X
Resource depletion		X	X	X					X
Soil quality depletion	X				X					X
Spread of resistant pests			X	X		X		X		X		X	X
Waste disposal increase	X						X	X		X			X
Water pollution												X	X

presents other trade-offs related to this limitation.

The uncertainties in deciding whether or not the criteria and indicators of the studied schemes take into account a trade-off concern almost all certification schemes. This is noteworthy because the studied schemes are recognised by the EC and therefore have to meet at least the requirements set out in the RED 2. This suggests that there is little consistency between most voluntary certification schemes for biofuels, which in turn underlines the urgent need for a harmonised certification approach, mandatory for all recognised certification schemes in addition to the minimum requirements currently defined in the RED 2.

4.2.2. Special Case: Rebound Effects

A rebound effect is characterised by efficiency gains in resource consumption (e.g., in energy consumption) that lead to an effective reduction in the price per unit of resource services, which in turn increases the consumption of the resource and partially offsets the effects of the efficiency gain [107,108,109].

We found rebound effects for the AP Increased yield and AP Loss reduction. For the AP Increased yield, we are able to identify a rebound effect for LUC. For example, intensified crop production can lead to a rebound effect, i.e., making the production process more profitable and encouraging further expansion into natural ecosystems, locally or globally [110]. In addition, we have found rebound effects for the AP Loss reduction for economic inefficiency [107] and GHG emissions [111].

As the examples show, rebound effects are relevant for a number of additionality practices. In particular, for low ILUC-risk certification approaches that include additionality practices characterised by an increase in resource efficiency, such as the AP Livestock efficiencies, AP Increased yield, and AP Loss reduction, it seems necessary to consider potential rebound effects.

4.3. Instruments of the Certification Schemes to Verify Trade-Offs

4.3.1. Similarities and Differences in Trade-Off Verification Methods of the Schemes

We can ascertain that the verification of specific trade-offs varies between the analysed schemes. As shown in Figure 6, this is evidenced by the criteria and indicators already used and implemented in certification practice.

Firstly, there are trade-offs that are addressed mostly by the schemes and for which similar criteria and indicators are used, e.g., biodiversity loss or GHG emissions. Within this group there are trade-offs for which established and recognised methods are used. For example, Bonsucro and Better Biomass use the BioGrace tool for the calculation of GHG emissions [112]. For other trade-offs, such as biodiversity loss, qualitative deficits could be shown for examples of the biodiversity indicators of the RSB [113] and the Roundtable on Sustainable Palm Oil (RSPO) [114].

Secondly, there are also trade-offs that are addressed mostly in the schemes for which different certification instruments are used, e.g., soil quality depletion and water depletion. This is consistent with the findings of Scarlat and Dallemand (2011), who revealed that a number of environmental criteria of certification schemes seem to be formulated in quite different ways [9].

Thirdly, there are trade-offs that are partly addressed by the schemes and for which the schemes use similar criteria and indicators, e.g., atmospheric pollution, hazardous work, and for which the schemes use different verification methods, e.g., food insecurity, harm to local population.

Finally, in almost all cases the schemes use different certification instruments to verify the trade-offs for which we have identified gaps, e.g., human disease and economic inefficiency. This could be explained by the fact that the schemes have less experience with the verification of these trade-offs. For the gaps in particular, the criteria and indicators currently used by the schemes could potentially be expanded. For example, ISCC requires best practices for health risks, while other schemes such as REDcert, Red Tractor, RSB, RTRS, SQC, and TASCC at least require health aspects to some extent.

In conclusion, there is no consensus on how to assess the majority of the trade-offs in certification practice. In these cases, further research is needed to find robust and harmonised certification instruments that could be an appropriate measure to overcome the differences between the assessment and verification approaches.

4.3.2. Readiness of the Certification Schemes to Verify Trade-Offs

About two thirds of the trade-offs inventoried are already largely considered in the certification schemes analysed. This indicates that the schemes seem well equipped to implement a low ILUC-risk certification approach that is based on the additionality practices studied here. In particular, from these trade-offs, we have identified several trade-offs that are mostly addressed in the certification schemes. Assessing these trade-offs could be the minimum requirement for all schemes relevant to sustainability certification of biofuel feedstocks. In this sense, the mandatory sustainability criteria required in Article 29 of the RED 2, e.g., conservation of high-carbon stock and highly biodiverse land, could be extended by requiring an assessment of the other trade-offs which are mostly addressed, e.g., soil quality depletion, water pollution, etc. This would even be a low burden for the schemes, as most of them already have verification instruments for such trade-offs. Other studies also suggest to include mandatory sustainability criteria for the protection of air, soil and water in the RED 2, e.g., [17,115]. However, a recent proposal to amend the RED 2 does not include criteria for the protection of air, soil, and water for biomass produced from agricultural feedstocks [116].

On the other hand, one third of the trade-offs are not or hardly addressed by the schemes. This suggests that appropriate instruments to verify these trade-offs need to be developed and implemented within the schemes under study. In this context, it is important to note that the trade-offs we have identified are merely potential risks. To be sure that the trade-offs have an impact in the practice of low ILUC-risk biomass production, empirical impact assessment studies are needed for verification. If such an assessment shows that a particular trade-off has an impact, certification schemes need to be adapted to address it.

4.4. Recommendations for Developing Assessment Approaches to Verify Trade-Offs in Low ILUC-Risk Certification

4.4.1. Demand for Evaluation and Potential Further Development of Certification Schemes

The study presented here deals with the identification of trade-offs and whether these are considered in voluntary certification schemes for sustainable biofuels. However, the study can only show to a limited extent how the criteria and indicators of the schemes examined address the identified trade-offs (see Section 4.3.1). In this sense, to our opinion, it is necessary to examine the scientific quality of certification instruments that address trade-offs that may arise from the use of additionality practices in low ILUC-risk certification. Therefore, we recommend (1) developing evaluation approaches to verify the scientific soundness of existing certification instruments, and (2) developing assessment approaches that are based on scientific methods and are appropriate for certification practice.

To estimate how relevant a trade-off might be for the development of an effective low ILUC-risk certification approach, we propose to consider the frequency with which a trade-off is addressed in the literature for a given additionality practice, as shown in Figure 5. In this sense, we assume that the frequently addressed trade-offs are highly relevant for the additionality practices under study. Under this approach, there is a greater need to evaluate existing certification instruments for the trade-offs that are frequently addressed than for those infrequently addressed. On the one hand, this approach is simple, practicable and easy to follow. On the other hand, it might not be sufficient to simply count the number of scientific publications that deal with a particular trade-off and conclude from this number that one trade-off is more relevant than another. This is because the examination of a trade-off in the scientific literature does not always depend on its relevance for sustainable biofuel production, but often on political decisions, such as in the case of GHG emissions [117]. There are also other approaches to determine the relevance of a trade-off, e.g., multi-criteria decision-making methods [118,119] and expert interviews [120]. Despite these shortcomings, we decided to assess the relevance of a trade-off based on the frequency with which it is addressed in the literature, as this simple approach is sufficient for a first classification of the identified trade-offs. In further studies, the relevance of individual trade-offs could be analysed using much more complex methods.

We propose to evaluate the certification criteria and indicators for the frequently addressed trade-offs presented in

Table 10. Recommendations for the evaluation of existing and the development of new certification criteria and indicators for trade-offs that could arise in low ILUC-risk certification approaches that apply specific additionality practices. Own table.

Trade-Off	Trade-Off Addressed	Relevance for Low ILUC-Risk Certification Approaches Based on Specific Additionality Practices
Biodiversity loss	Mostly addressed	AP Unused land, AP Increased yield, e.g., EU Implementing Regulation [20]; AP Livestock efficiencies.
GHG emissions	Mostly addressed	All additionality practices.
Soil quality depletion	Mostly addressed	Almost all additionality practices except AP Loss reduction.
Water depletion	Mostly addressed	Almost all additionality practices except AP Loss reduction.
Water pollution	Mostly addressed	Almost all additionality practices except AP Loss reduction.
Atmospheric pollution	Partly addressed	Almost all additionality practices except AP Unused land.
Harm to local population	Partly addressed	AP Unused land.
Economic inefficiency	Mostly not addressed	AP Loss reduction.
Human disease	Mostly not addressed	Almost all additionality practices except AP Unused land
Increased economic expenses	Mostly not addressed	AP Unused land, AP Chain integration, AP Increased yield, e.g., ISCC CORSIA [43].
Livestock disease and abuse	Mostly not addressed	AP Livestock efficiencies.
Resource depletion	Mostly not addressed	AP Chain Integration, AP Livestock efficiencies, AP Loss reduction.

. For each trade-off, potential low ILUC-risk certification approaches based on specific additionality practices are described.

In addition, we propose, to consider the trade-offs that are addressed by the majority of certification schemes to increase the effectiveness of a low ILUC-risk certification approach that takes the additionality practices examined into account. These trade-offs could be most promising for certification schemes, as they are present in almost all schemes studied.

4.4.2. Recommendations for the Development of Effective Assessment Approaches for the Gaps

General Suggestions for Robust and Practicable Certification Instruments

Certification criteria, among other things, (1) are clearly defined so that users can easily understand them without misinterpretation [121,122], (2) consider local conditions [121,123], (3) are enforceable in practice, i.e., the more vague and general the criteria are, the more difficult they are to enforce [122,123], and (4) system boundaries are defined per sustainability criterion to clarify the producer’s responsibility [123]. In addition, the major requirements for methods and indicators for sustainability certification of biofuels are reliability and conceptual soundness, feasibility, i.e., measurability and practicality, and relevance for the end user [113].

For developing verification methods, we recommend to consider reference frameworks that propose key principles for robust and credible sustainability certification schemes, such as the International Social and Environmental Accreditation and Labelling (ISEAL) Alliance, the Accountability Framework initiative (AFi), and the International Standard Organization (ISO) [124]. In particular, we recommend to take the ISEAL’s Credibility principles [125] and ISEAL Codes of Good Practice (such as [126,127]) into account when developing certification instruments for the gaps. This could be complemented with the AFi’s Guidance on Monitoring and Verification [128]. The AFi suggests amongst other guidelines for effective monitoring systems and characteristics of a credible verification process.

Prioritizing the Need to Develop Assessment Approaches for the Gaps

We propose an approach to prioritize the trade-offs for which we have identified gaps in order to develop effective certification instruments. To this end, in

Table 11. Prioritization of the need to develop assessment approaches that are appropriate for trade-offs for which gaps could be identified. Own table.

Trade-Off	AP Unused Land	AP Chain Integration	AP Livestock Efficiencies	AP Increased Yield	AP Loss Reduction	Frequency	Priority Level *
Change in commodity price					X	Infrequently	Very low
Economic inefficiency	X	X	X	X	X	Infrequently	High
Human disease		X	X	X	X	Frequently	Very high
Increased economic expenses	X	X	X	X	X	Frequently	Very high
Livestock disease and abuse			X			Frequently	Low
Resource depletion	X	X	X	X	X	Frequently	Very high
Spread of resistant pests				X	X	Infrequently	Very low

* Priority level: (1) Very low: Trade-off is relevant to less than half of the additionality practices and is infrequently addressed; (2) Low: Trade-off is relevant to less than half of the additionality practices and is frequently addressed, (3) High: Trade-off is relevant to more than half of the additionality practices and is infrequently addressed; (4): Very high: Trade-off is relevant to more than half of the additionality practices and is frequently addressed.

, we present a ranking of the gaps based on two factors: (1) the number of additionality practices for which a gap is relevant, and (2) the frequency with which a trade-off is addressed in the literature (compare Figure 5).

In particular, we recommend developing appropriate assessment approaches for the gaps for which we can determine a very high priority level, such as human disease, increased economic expenses, and resource depletion. In addition, we can determine a high priority level for economic inefficiency. Of all gaps, these trade-offs could be the minimum in developing science-based certification instruments.

For the development of effective certification instruments for the gaps rated as very high and high priority, we recommend considering assessment approaches proposed by recognised institutions and organizations, as well as in the scientific literature. For example, certification instruments for human disease could be based on approaches developed by the World Health Organization (WHO), such as a human health risk assessment (see [129]). To address increased economic expenses, approaches to product life cycle cost (LCC) accounting, such as those proposed by the German Sustainable Building Council, could be a starting point for developing a similar approach for voluntary certification schemes for sustainable biofuels (see [130]). Assessment approaches that consider resource depletion could focus on economically viable circular economy strategies at the product level to improve resource use (see [131]).

In contrast, the priority for developing assessment approaches for the other gaps, such as change in commodity price, livestock disease and abuse, and spread of resistant pests, is much lower. Therefore, these trade-offs could be neglected in the development of certification instruments. However, specifically for livestock disease and abuse, we strongly recommend that schemes implementing a low ILUC-risk certification approach that includes the AP Livestock efficiencies put into practice certification instruments that are appropriate to address this trade-off.

In our opinion, the suggestions made in this section are very important for the development of robust and credible certification criteria and indicators for the identified gaps. However, we must clarify that we can only make very general recommendations on this topic here. In follow-up studies, appropriate assessment instruments for the gaps need to be developed for certification practice according to scientifically sound methods. Such studies could consider the recommendations provided as a starting point.

5. Conclusions

This paper is a contribution to the development of an effective assessment framework for low ILUC-risk certification for biofuels as we can show that (1) many different trade-offs are potentially relevant to the use of additionality practices, (2) there are many certification instruments to cover the multitude of trade-offs, (3) there are trade-offs that are given preferential consideration by the schemes, and (4) there are considerable gaps in certification instruments for certain trade-offs.

Furthermore, this study contributes to the necessity to implement additionality practices in low ILUC-risk certification approaches without compromising sustainability by identifying and analysing trade-offs between the intended short-term outcomes of additionality practices (e.g., increased crop yields) and the medium- to long-term impacts on environmental factors, as required by the EU Implementing Regulation. This EU policy is required by Article 30(8) of the EU RED 2 and has established rules for compliance with the requirements for low ILUC-risk certification of biofuels.

In addition, the paper provides valuable information for evaluating additionality practices that could be effectively implemented in voluntary certification schemes by considering the number of trade-offs that are currently preferentially addressed by the schemes and the gaps identified. This could be supplemented by taking into account those trade-offs that are frequently addressed in the literature reviewed and therefore could potentially be of particular importance to a given additionality practice. Specifically, these trade-offs could be considered to increase the effectiveness of low ILUC-risk certification approaches.

In this regard, the implementation of the AP Unused land is the most promising additionality practice. First, a majority of the preferentially addressed trade-offs are addressed frequently in the literature for this additionality practice. Thus, most schemes have certification instruments to assess them. Second, only few novel certification instruments need to be developed for the small number of gaps found for this additionality practice. In contrast, implementing the AP Loss reduction could be challenging for certification schemes, as we identified the largest number of gaps for this additionality practice. Developing certification instruments for the large number of gaps is likely to be burdensome. However, it should be noted that for the AP Loss reduction, we identified the lowest number of trade-offs overall. In contrast, we can identify the highest number of trade-offs for the AP Livestock efficiencies and also the highest number of trade-offs frequently addressed in the literature. Thus, implementing this additionality practice in a low ILUC-risk certification approach could become very challenging for sustainability certification schemes.

In addition, we can contribute to some extent to the question of how recognised certification schemes address the identified trade-offs and whether the schemes are ready to implement a low ILUC-risk certification approach. The schemes are currently in a position to implement such an approach, as certification instruments already exist for most of the trade-offs. Trade-offs, such as GHG emissions, biodiversity loss, and soil, water, and air deterioration, are already covered by most schemes. However, to some extent, there are existing criteria and indicators that need to be harmonised and reconciled. This is because the certification instruments for trade-offs, such as water depletion and soil quality depletion, vary from scheme to scheme, although such trade-offs are considered in most schemes. In particular, the certification instruments for the gaps differ significantly between the schemes. Therefore, these criteria and indicators need to be substantially adjusted to bring the certification instruments of the schemes into alignment.

To develop credible and reliable certification instruments for low ILUC-risk certification, we propose the following future research. First, a qualitative assessment methodology could be developed to verify that certification instruments addressing a specific trade-off are based on scientifically sound methods. Particular attention can be paid to the trade-offs that are frequently addressed for a given additionality practice, e.g., biodiversity loss for the AP Unused land. Second, assessment approaches could be developed for those certification instruments for which these verifications indicate a weak scientific basis. Finally, assessment approaches could be developed for the identified gaps, particularly considering the gaps for which a very high (such as human disease, increased economic expenses, and resource depletion) and high (such as economic inefficiency) priority level can be determined.