This study presents a life cycle assessment (LCA) of decentralized succinic acid production from acid whey and oat pomace, comparing decentralized, small-scale implementation with larger-scale options and explicitly evaluating energy-source driven variability. The novelty lies in explicitly contrasting small-scale decentralization with large-scale operation, and in quantifying the relative contributions of substrate production and energy mix to total environmental impact. The results show that the production of 1 kg of succinic acid generates emissions ranging from 44.7 kg CO₂-eq. (onshore wind power) to 349.5 kg CO₂-eq. (lignite-fired power plants). The study emphasized the importance of including the production process of agricultural products in the assessment of residual materials and showed that agricultural inputs can dominate environmental impacts relative to energy-intensive downstream steps. The study further aimed to determine the economic viability when the process was upscaled to a working volume of 1000 L carried out decentralized. The total capital investment was 595,130 €, with annual operational costs of 264,435 €. Given a production rate of 832 kg per year and an annual revenue of 3993 €, profitability indicators show that the process remains economically unviable under the base-case assumptions. However, the analysis identifies specific levers (e.g., improved yield, higher titer, equipment sharing, and multi-product integration) that could enhance feasibility for local, small-scale biorefineries.