Early-stage sustainability assessment of greywater treatment with Moringa oleifera seed extract and biochar

Access to safe and reliable water remains a significant challenge in much of the Global South, especially in rural areas where greywater treatment infrastructure is lacking. This study presents an early-stage sustainability assessment of a novel system that utilises biochar and Moringa oleifera seed extracts to treat greywater in rural Kenyan households. The proposed solution combines local biochar, a by-product of wood gasification cookstoves, and powdered Moringa oleifera seed cake, a residue from local agroforestry activities. The presented assessment applied a qualitative approach that integrates life cycle, circular bioeconomy, and sustainable sanitation principles. The key sustainability opportunities involved in the assessed system include improved human health and hygiene, the carbon sequestration potential of biochar, greywater reuse, and efficient use of local biomass resources. However, the system also involves risks related to filter media disposal, nutrient loss and system maintenance. The analysis highlights the trade-offs between using Moringa oleifera seed cake for water purification and animal feed. Moreover, the early-stage assessment identifies the need for pilot trials, participatory design and data collection to develop future life cycle analyses and implementation strategies. This integrated approach provides a sound basis for the sustainable development of natural greywater treatment systems that meet the goals of a circular bioeconomy. • A qualitative sustainability assessment method for bio-based water treatment. • Life cycle impact, circular bioeconomy and sustainable sanitation combined. • The assessment identified a major uncertainty linked to filter disposal.