Sustainable biodiesel production from oil crops: The impact of bio-nutrient recycling on yield and farmer technology acceptance

Circular utilization of biowaste through biofuel production is a key priority for many waste-producing facilities seeking to internally supply biofuels and to reduce greenhouse gases. This study assesses the role of biowaste sewage sludge (SS) and its combination with biomass ash (SS+BA) in fertilizing perennial castor beans in temperate regions, emphasizing circular waste management and biofuel production. A combined approach of field experimentation and biodiesel quality analysis was implemented using two castor bean genotypes, comparing the effects of biowaste against both unfertilized and traditional fertilized controls. The introduction of biowaste nutrients significantly enhanced various plant growth parameters, leading to notable increases in seed, oil, and biodiesel yields compared with the control group. The highest yields of biodiesel and solid oil cake were recorded in the second year, with SS treatment yielding 1549 L ha −1 and 1958 kg ha −1 , results that were comparable to those from SS+BA. The quality parameters of the castor bean biodiesel met established standards, with the exception of kinematic viscosity and flash point, which necessitate blending with diesel. Analysis using the Technology Acceptance Model (TAM) indicated that castor bean serves as an efficient biodiesel input, with the intention to use influenced by perceived benefits, barriers, and attitudes towards agricultural application. Ultimately, the study concludes that the proposed approach for biodiesel production offers a sustainable and promising option for on-farm utilization. • Fertilizing biowaste improved castor bean production for inedible oil. • Nutrient-rich biowaste boosted oil and energy yields in castor plants. • The Black Sea coast of Turkey is suitable for perennial castor bean cultivation. • A strategy for integrating biodiesel production and utilization is proposed.