KEY DATA GAPS FOR LIFE CYCLE ASSESSMENT AND POLICY-RELEVANT METRICS

The life cycle assessment evidence base for cassava residue valorization remains fragmented, with reviews highlighting recurring methodological challenges: inconsistent functional units (per ton residue vs. per kg milk), weak primary data on residue handling emissions and losses, uncertain allocation across starch (main product) and residue streams, and highly assumption-sensitive substitution credits (what feed or energy is “displaced”) [29]. For dairy-focused claims, the most critical gaps are (i) farm-level measurements linking cassava residue inclusion to changes in enteric methane intensity, manure emissions, and milk composition under realistic rations, (ii) storage and processing inventories (electricity/fuel for drying, additive production footprints, shrink losses), and (iii) risk management externalities (cost and environmental impacts of rejected batches, detoxification steps, and quality testing) [152]. Policy-relevant interpretation also requires clarity on legal feasibility and governance: circular feed briefings note that some circular resources are permitted while others are constrained, and that regulatory alignment between food and feed systems shapes what circular pathways can scale in practice [149]. This policy point can be stated more concretely. In the European Union, materials placed on the market as feed are governed by feed-marketing legislation and the Catalog of Feed Materials. When a feed material is not yet listed in the Catalog, its first use on the market must be notified through the Feed Materials Register. This illustrates that residue streams can function legally as feed materials when they are specified, placed on the market, and controlled as such, rather than remaining undefined “waste.” By contrast, we did not identify clear jurisdiction-wide legal maximum inclusion limits for cassava pulp in dairy cows; current practical guidance is still driven more by feeding trials than by formal feed-law inclusion caps. Accordingly, the most defensible position for this review is that cassava residues can support circularity and potentially reduce feed–food competition when converted into specification-controlled feed ingredients, but robust claims about net climate benefits or system-wide sustainability should be framed as conditional on context-specific life cycle assessment with transparent boundaries and high-quality primary data.