Valorisation of human excreta for recovery of energy and high-value products : a mini-review

The current approach to managing waste is one of the major reasons for ecosystem imbalances. In many parts of the world, human excreta is indiscriminately dumped in the environment, leading to the entry of high concentrations of nutrients and pathogens. In urban sanitary systems, nutrients are often not recovered, but large amounts of natural resources (e.g. water) are used for treating wastes at the expense of the environment. These practices are unsuitable and pose risks to human health and the environment, as such current efforts are geared towards providing on-site sanitation and opportunities for nutrient and resource recovery. This mini-review summarises the efforts to valorise human waste and process routes for the recovery of value-added products. These involve a review of ecological sanitation, systems that safely collect and treat human waste in situ and advanced waste-to-energy systems to convert recovered materials to fuels, heat and/or electricity. Focus is given to low-cost technological solutions that offer ecological benefits and opportunities to recover useful products. The barriers and opportunities to the adoption of on-site sanitation and appropriate technologies are discussed, considering current limitations and potential benefits. There are opportunities to recover useful products from human wastes; however, further research is needed to ascertain the value and impact of recovered products