## 1 Introduction  
A strategic component of Europe's political agenda for sustainable biomass supply is the reduction of indirect land use change (ILUC) impacts associated with its use for conventional biofuels, bioliquids, and biomass fuels. The EU's Renewable Energy Directive II (RED II) mandates the phase-out after 2023 of \"high ILUC-risk\" biofuels (that is, fuels produced from feedstocks associated with significant levels of agricultural expansion into land with high carbon stock) [1, 2, 3, 4]. The RED II also introduces the concept of certified \"low ILUC-risk\" biofuels, bioliquids, and biomass fuels. These are produced from feedstocks that avoid food and feed crop displacement through one of two additional pathways: (i) yield increases from improved agronomic practices, or (ii) cultivation of areas not previously used for crop production (including areas with natural constraints such as unused, abandoned, or severely degraded) [5,6]. These represent an important option to maintain current biofuel shares and further develop their sustainable market potential in Europe from 2023 onwards, especially for sectors with limited short-term decarbonisation alternatives such as aviation, heavy duty road transport, and maritime. Indeed, there is a growing consensus in the EU [7,8] and beyond that the future holds significant risks for gaps in sustainable biomass supply. These gaps will continue to widen as RED II targets become more ambitious, RED II caps become more stringent, and as competition for, e.g., waste oils become more intense. Low ILUC-risk biomass can be seen as an opportunity to plug some of the supply gap by providing a new source of sustainable feedstock material. The issues involved in the concept of low ILUC-risk concern land and crop productivity and agronomic practices; as such, they are strongly related to agriculture and its role as a sink and a source of Greenhouse Gas (GHG) emissions, as well as the mosaic of wider sustainability goals surrounding soils, pollution, biodiversity, and rural communities. In the policy sphere, sustainable carbon cycles [9] and the \"Fit for 55\" EU policy package [10] (including amendments to RED II) will further refine regulatory and support measures for sustainable biofuel development [11], whereas the Common Agricultural Policy (CAP 2023-2028) reinforces climate change mitigation as a key objective for the agriculture sector [12]. The rationale of the low-ILUC concept is rooted in the principle of additionality. A consignment of feedstock can be low-ILUC only if there is evidence that it would not have been produced without the advanced biofuel sector. If such evidence is absent, there is a risk that using the material for biofuels will drive up total demand and hence incentivise unintended agricultural expansion. Research activities in the field of low input biomass resources have intensified during the last decade. Key research themes included the feasibility of restoring land with natural constraints, the biophysical capacity of crops to grow under different agro-climatic conditions, and their economic profitability both in farming land and in land with natural constraints. This paper aims to consolidate this knowledge base by providing a meta-analysis of the biophysical and economic opportunities for low ILUC risk biomass based on current research from six relevant European Union funded projects: Biomass Policies, S2 Biom, MAGIC, PANACEA, SoilCare, and BIO4A (see Table 1). The focus of the analysis is on inedible oil and lignocellulosic biomass crops that could be produced without competing with food and feed markets, are adapted to European agro-ecological zones (AEZ) [13], and can have yield increases from improved agricultural practices--both in conventional land and in land with natural constraints (unused, abandoned, or severely degraded). The paper consists of four sections. Section 2 outlines the methodology and baseline assumptions. Section 3 presents the results in two sub-sections.