(1) Background: VALUEWASTE, a European Commission Horizon 2020 project, is attempting to find new and sustainable sources of protein and fertiliser products using biowaste as a resource. Introducing these products to the market is essential to understand the social acceptance, behavioural changes and socioeconomic impacts related to products and value chains. (2) Methods: The applied framework provides insights from market, socioeconomic, and community acceptance points of view. Initially, we designed the context and targets of the study. The acceptance levels were tested in two study regions: the cities of Murcia (Spain) and Kalundborg (Denmark). Secondly, we established a survey questionnaire (N = 523) combining social acceptance and life-cycle assessment methodology questions. Lastly, we performed a scenario-based workshop discussing behavioural changes related to the introduction of new bio-products to customers. (3) Results: Our study of developing new bio-products (food, feed, fertiliser) from biowaste produced forceful comparative results from the two regions regarding three aspects of social acceptance: market, socioeconomic, and community. (4) Conclusions: The present study, engaging citizens, consumers, producers, and policy makers, provides insights into what is important for the social acceptance of new protein sources for food, feed, and recycled fertilisers from bio-waste in the Murcia and Kalundborg city regions. Our observations, based on analyses applying three dimensions of social acceptance, can be directly applied elsewhere, guiding decision makers on how to fortify social acceptance regarding new circular economy business models and the bioeconomy in Europe.