Abstract: The high-value valorization of biomass-derived resources and the eco-friendly remediation of nitrogen-laden wastewater represent pivotal challenges for realizing dual-carbon targets and advancing the circular economy. Under mild operational conditions, an electrocatalysis strategy enables the conversion of biomass-derived platform molecules, namely 5-hydroxymethylfurfural, furfural, and lactic acid, into high-value fine chemicals (e.g., 2,5-furandicarboxylic acid and furoic acid). This anodic oxidation process can be coupled with cathodic nitrate reduction to synthesize valuable ammonia, thereby establishing a synergistic “waste treats waste” paradigm that substantially enhances resource utilization and economic viability. Unlike existing reviews that address discrete electrocatalytic reaction systems separately, this work focuses on thermodynamic synergy mechanisms and bifunctional catalyst design principles for coupled electrolytic systems. A central viewpoint is that anodic biomass oxidation is not merely an energy-saving alternative to the oxygen evolution reaction; rather, it functions as a modulable reaction unit that requires precise coordination with cathodic nitrate reduction in terms of molecular reactivity, electron transfer stoichiometry, and electrolyte microenvironment. This work systematically compares 5-hydroxymethylfurfural, furfural, and lactic acid as representative anodic substrates based on their functional group characteristics and oxidation extents. Specifically, 5-hydroxymethylfurfural undergoes a six-electron oxidation to 2,5-furandicarboxylic acid via intermediates such as 2,5-diformylfuran or 5-hydroxymethyl-2-furancarboxylic acid; furfural follows a two-electron oxidation pathway to furoic acid; and lactic acid proceeds via C—C bond cleavage to yield pyruvate, acetate, or fully oxidized species. This comparative analysis demonstrates that substrate molecular structure, pH-dependent chemical stability, intermediate transformation pathways, and catalyst-tunable pathway selectivity collectively determine the compatibility between anodic reactions and nitrate reduction. This review also elaborates on the reaction pathways and catalyst engineering strategies for electrocatalytic nitrate reduction. Comparative thermodynamic analysis, electrolyte condition screening, and electrode catalyst requirement assessment collectively indicate that the coupling of biomass oxidation and nitrate reduction is governed by three intercorrelated core variables: potential matching, pH compatibility, and reactor geometry. Potential matching dictates overall energy efficiency; pH compatibility regulates substrate stability, intermediate evolution, and catalyst durability; and reactor geometry controls mass transport, ion migration, and in-situ product separation. These three parameters constitute a universal evaluation framework for assessing the feasibility of integrating diverse anodic oxidation reactions with cathodic nitrate reduction. Future research should shift from the independent optimization of single-electrode performance toward holistic system-level integration. Promising directions include the design of bifunctional electrocatalysts with asymmetric active sites, intrinsic defects, heterointerfaces, or tandem catalytic centers to balance anodic and cathodic kinetics; evaluation of long-term durability in real nitrate-containing wastewater and crude biomass-derived feedstocks; and integration of techno-economic analysis with life-cycle assessment to identify practical pathways for green ammonia synthesis and biomass upgrading.