Valorisation of Human Excreta for Recovery of Energy and High-Value Products: A Mini-Review

Abstract

The current approach to managing waste is one of the major reasons for ecosystem imbalances. In many parts of the world, human excreta are 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.

Nutrient dynamics during composting of human excreta, cattle manure, and organic waste affected by biochar

“…About 2 billion people lack access to basic sanitation, and of these, 673 million practice open defecation (WHO, 2019). This situation, combined with poor or inexistent waste management systems, make dumping of human excreta and other organic waste in streets, drains, and riverbanks a common practice (Langergraber & Muellegger, 2005; Orner & Mihelcic, 2018; Somorin, 2020). As a consequence, water polluted with fecal material and pathogens endangers public health (WHO, 2019).…”

Assessment ofAegle marmelosFruit Extracts as Organic Insecticide forSpodoptera exiguaonAllium ascolanicum

“…For further action, control with organic pesticides [48,49,46] should be linked to applying organic farming to A. ascolanicum cultivation. All organic waste -agricultural waste, livestock waste, kitchen waste, leftover food, and human excrement from pit latrines and septic tanks [50][51][52][53][54][55] can return to A. ascolanicum plantations to maintain and increase soil fertility. With anaerobic processing in individual or communal biogas digesters [56][57][58], a double benefit will be obtained, i.e., biogas -clean and renewable energy, and two types of organic fertilizers, i.e., solid and liquid fertilizers which are beneficial for agricultural crops [59][60][61][62].…”

Applied smouldering for co-waste management: Benefits and trade-offs

“…Smouldering combustion is emerging as a valuable application for many environmentally beneficial purposes such as: (i) land remediation [1], (ii) hazardous liquid management [2,3], (iii) decentralized sanitation [4,5], (iv) pyrolysis/torrefaction [6][7][8][9][10], (v) wastewater sludge treatment [11][12][13], (vi) organic waste treatment [14][15][16], and (vii) resource recovery/generation [17][18][19][20]. In all these cases, smouldering can be harnessed to generate energy from traditionally problematic wastes, such as those with high moisture contents (e.g., biomass sludges [15,21,22]) and low volatility (e.g., coal tars and heavy oils [2,3,[23][24][25]).…”