Department Sanitation, Water and Solid Waste for Development

Resource recovery

Resource recovery, market based approaches, and business models, are key to sustainable management.
Resource recovery, market based approaches, and business models, are key to sustainable management.

Resource recovery from treatment products are a key aspect of sustainable management of sanitation, and can contribute to benefits such as stimulating proper operation and maintenance of a treatment plant, reducing pressure on local resources, and offsetting operation costs. As part of an engineering design approach, a focus on resource recovery can also support in defining treatment objectives where official standards do not exist.

Resource recovery from faecal sludge can have many different forms and product types, such as fuel, nutrients, feed, materials, and (irrigation) water. As referenced below in publications, previous work of the Management of Excreta, Wastewater, and Sludge (MEWS) research group has included production of various forms of solid fuel endproducts, including demand as an industrial fuel, carbonization through optimizing slow-pyrolysis processes, co-processing faecal sludge with other organic wastes, and pelletization for use as a fuel and to enable faster drying. Much of this work is summarized in the literature review, To Char or Not to Char , including how to select a treatment technology for producing a solid fuel endproduct. Also see below for use of plants from planted drying beds as an animal feed, and recommendations for optimal operation of planted drying beds.

When deciding on what faecal sludge endproduct is most appropriate, it is important to consider which products are desirable from a financial and market perspective, along with social and cultural considerations, embedded in an appropriate integrated planning approach. However, since markets for faecal sludge endproducts frequently do not exist, we developed the Market Driven Approach (MDA), a tool that helps to determine the market attractiveness of a future faecal sludge endproduct in a local context.

Planning for sustainable implementation also includes developing resource recovery based business models. As part of the RRR initiative (Resource, Recovery, and Reuse), MEWS contributed to a comprehensive overview of resource recovery focused business models for the waste and sanitation sector published by IWMI.

Current and previous collaborators

  • University of Dar es Salaam
  • Makarere University
  • NWSC
  • CREEC
  • Bioburn
  • Zürich University of Applied Sciences (ZHAW)
  • Cheikh Anta Diop University
  • Waste Enterprisers Ltd

Current funding

  • SDC (funding)

Previous funding

  • Symphasis Foundation
  • REPIC (Renewable Energy & Energy Efficiency Promotion in International Cooperation)
  • EU SPLASH
  • SDC
  • SECO

Publications | Technologies

Pyrolysis of dry toilet substrate as a means of nutrient recycling in agricultural systems: potential risks and benefits

Biochar is increasingly being applied as a soil amendment in agriculture. Biochar is typically produced from plant biomass and contains relatively low amounts of plant nutrients (e.g., N, P, and K), thus providing limited fertilizer value. Human excreta contains plant nutrients that could be recycled to create sustainable agricultural nutrient cycles. This study investigated the potential of biochar derived from a dry toilet substrate as soil amendment. The substrate consisted of urine, faeces, and wood chips, and was pyrolyzed at 500–650 °C for 10 min. The biochar was analyzed for plant available P, water leachable P and K, carbon stability, pH, electrical conductivity, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dioxins, and germination tests with barley and lettuce were conducted to estimate the biochar fertilizer value and potential bio-toxicity. The biochar contained 25.0 ± 1.0 g N/kg dry mass (DM), 33.1 ± 2.1 g P/kg DM and 20.7 ± 0.2 g K/kg DM. 65% DM P was extractable by formic acid solution, 31.7% DM P and 60.5% DM K were water leachable in a ten-day column water-leaching experiment. The biochar complied with European regulations for PAHs, PCBs, dioxins and heavy metal concentrations, except for Zn and Ni. Germination of salt-resistant barley was not affected by biochar doses < 50% DM, while salt-sensitive lettuce germination was inhibited at doses ≥ 2% DM, indicating that the dry toilet substrate biochar induced salt stress. Based on these results, it is recommended that urine separation should be considered for biochar of excreta, which could reduce salt stress while maintaining concentrations of “fixed” or bioavailable nitrogen. Graphic Abstract: [Figure not available: see fulltext.]
Bleuler, M.; Gold, M.; Strande, L.; Schönborn, A. (2021) Pyrolysis of dry toilet substrate as a means of nutrient recycling in agricultural systems: potential risks and benefits, Waste and Biomass Valorization, 12, 4171-4183, doi:10.1007/s12649-020-01220-0, Institutional Repository

Operating parameters for three resource recovery options from slow-pyrolysis of faecal sludge

Slow-pyrolysis is a treatment technology that is being explored for treatment of faecal sludge (FS) from onsite sanitation technologies. Next to pathogen inactivation, the technology produces treatment products. Revenues from these products could offset treatment costs and contribute to financially viable sanitation. In comparison to lignocellulosic biomass and other biowastes, little information is available on operating parameters for FS pyrolysis to produce char for different resource recovery options. In Kampala, Uganda, this bench-scale study investigated the influence of two major operating parameters, hold time (10, 20 and 40 minutes) and pyrolysis temperature (350, 450 and 600 °C) for pyrolysis of FS into char for solid fuel production, soil enhancement and carbon sequestration. Hold time: 10 min was the most suitable hold time for all resource recovery options as char characteristics had only minor variations between hold times. Temperature: Char characteristics identified 350 °C as the most suitable for fuel production and 450 or 600 °C for carbon sequestration. FS char had characteristics for soil enhancement comparable to biowaste and lignocellulosic biomass chars, with heavy metal concentration exceeding guideline concentrations. The most suitable temperature needs to be selected based on plant and soil type, and legal regulations.
Gold, M.; Cunningham, M.; Arnheiter, R.; Schönborn, A.; Niwagaba, C.; Strande, L. (2018) Operating parameters for three resource recovery options from slow-pyrolysis of faecal sludge, Journal of Water Sanitation and Hygiene for Development, 8(4), 707-717, doi:10.2166/washdev.2018.009, Institutional Repository

To char or not to char? Review of technologies to produce solid fuels for resource recovery from faecal sludge

Resource recovery from faecal sludge can take many forms, including as a fuel, soil amendment, building material, protein, animal fodder, and water for irrigation. Resource recovery as a solid fuel has been found to have high market potential in Sub-Saharan Africa. Laboratory- and pilot-scale research on faecal sludge solid fuel production exists, but it is unclear which technology option is most suitable in which conditions. This review offers an overview and critical analysis of the current state of technologies that can produce a dried or carbonized solid fuel, including drying, pelletizing, hydrothermal carbonization, and slow-pyrolysis. Carbonization alters fuel properties, and in faecal sludge, it concentrates the ash content and decreases the calorific value. Overall, a non-carbonized faecal sludge fuel is recommended, unless a carbonized product is specifically required by the combustion technology or end user. Carbonized and non-carbonized fuels have distinct characteristics, and deciding whether to char or not to char is a key judgement in determining the optimal solid fuel technology option. Based on the existing evidence, this review provides a decision-making structure for selecting the optimal technology to produce a faecal sludge solid fuel and identifies the top research needs prior to full-scale implementation.
Andriessen, N.; Ward, B. J.; Strande, L. (2019) To char or not to char? Review of technologies to produce solid fuels for resource recovery from faecal sludge, Journal of Water Sanitation and Hygiene for Development, 9(2), 210-224, doi:10.2166/washdev.2019.184, Institutional Repository

Faecal sludge as a solid industrial fuel: a pilot-scale study

Revenues from faecal sludge (FS) treatment end products could offset treatment costs and contribute to financially viable sanitation. In urban sub-Saharan Africa, energy-producing resource recovery has the potential to generate greater revenue than use as soil conditioner. In contrast with wastewater sludge, the technical feasibility of using dried FS as solid fuel in industries has not been investigated. This study evaluated it through characterization of dried FS from drying beds and by assessing the combustion performance in two pilot-scale kilns, in Kampala and Dakar. Results from the fuel characterization demonstrate that dried FS had comparable fuel characteristics as wastewater sludge considering calorific value and ash content. The calorific values and ash contents were 10.9–13.4 MJ/kg dry matter (DM) and 47.0–58.7%, respectively. Results from pilot-scale experiments suggest that dried FS can be effective in providing energy for industries. Temperatures in pilot-scale kilns fueled by FS were 800W C, sufficient for curing of clay bricks, and 437W C, sufficient for waste oil regeneration. In Kampala and Dakar, an estimated 20,000 tons of FS DM per year accumulate. Tapping the industrial fuel market and financial benefits could be realized through optimization of onsite sanitation and treatment technologies.
Gold, M.; Ddiba, D. I. W.; Seck, A.; Sekigongo, P.; Diene, A.; Diaw, S.; Niang, S.; Niwagaba, C.; Strande, L. (2017) Faecal sludge as a solid industrial fuel: a pilot-scale study, Journal of Water Sanitation and Hygiene for Development, 7(2), 243-251, doi:10.2166/washdev.2017.089, Institutional Repository

SEEK (sludge to energy enterprises in Kampala): co-processing faecal sludge for fuel production

The goal of this project was to improve the resource-recovery value of faecal sludge treatment products. A market assessment identified coffee husks, spent grain, and sawdust as optimal organic wastes to co-process with faecal sludge to increase its fuel value. Drying times of faecal sludge to 90% solids were reduced by half with co-pelletizing with these organic wastes. Briquettes produced with char had comparable heating value, fuel performance, and emissions to charcoal briquettes currently being sold. Use of pellets as a fuel was tested in a gasifier and in several industrial clay kilns (after crushing). High ash content led to clinker formation in the gasifier, but performed well in kilns. The potential market for co-processed faecal sludge fuels is high in Kampala, Uganda, especially among industries, however, the market for pellets needs to be developed.
Ward, B. J.; Gold, M.; Turyasiima, D.; Studer, F.; Getkate, W.; Maiteki, J. M.; Niwagaba, C. B.; Strande, L. (2017) SEEK (sludge to energy enterprises in Kampala): co-processing faecal sludge for fuel production, In: WEDC conference 40, 2808 (6 pp.), Institutional Repository

Novel plant species for faecal sludge drying beds: survival, biomass response and forage quality

This study investigated the ability of forage plant species that have not previously been used in the treatment of faecal sludge to grow in planted drying beds. Experiments were conducted in 11 L and 25 L pots with layers of sand and gravel to replicate drying beds, and three loading rates (100, 200, 300 kg TS/m2*year). Plant density with faecal sludge was increased for Echinocloa colona, Echinochloa crus-galli, Echinochloa pyramidalis, Paspalidium geminatum, and Paspalum vaginatum (196, 64, 171, 170 and 98% respectively), whereas Eleusine indica and Imperata cylindrica had reduced growth with faecal sludge (−21, −80%, respectively). Protein, minerals, nutrients and fibers as metrics of forage quality all indicated that the species in these trials improved with growth in faecal sludge drying bed conditions. Different species should be selected based on treatment objectives, for example E. crus-galli had optimal forage production characteristics at 200 and 300 kg TS/m2*year loading rates, whereas P. geminatum and P. vaginatum at 100 and 200 kg TS/m2*year. This study suggested that in addition to E. pyramidalis – E. crus-galli, P. geminatum, and P. vaginatum are also good candidates for treatment of faecal sludge with simultaneous forage production to offset treatment costs.
Gueye, A.; Mbéguéré, M.; Niang, S.; Diop, C.; Strande, L. (2016) Novel plant species for faecal sludge drying beds: survival, biomass response and forage quality, Ecological Engineering, 94, 617-621, doi:10.1016/j.ecoleng.2016.05.027, Institutional Repository

Results from FaME (Faecal Management Enterprises) – can dried faecal sludge fuel the sanitation service chain?

In Sub-Saharan Africa, sanitation needs for the majority of the urban population are met by onsite sanitation technologies. Cities grapple with management of faecal sludge (FS) once these technologies become full, while at the same time the urban economy is resource intensive. The FaME (Faecal Management Enterprises) project addressed both of these issues by identifying untapped markets for FS treatment products. Industries have a high fuel demand and FaME demonstrated that dried FS could be used as a solid combustible in industrial kilns. Existing treatment technologies were adapted for fuel production, and its application was demonstrated in two pilot kilns. Historically used as a soil conditioner, processing of FS to a solid biofuel could provide higher revenues, thereby providing a financial incentive for stakeholders to enhance FS management service along the entire sanitation chain.
Gold, M.; Niang, S.; Niwagaba, C. B.; Eder, G.; Murray Muspratt, A.; Diop, P. S.; Strande, L. (2014) Results from FaME (Faecal Management Enterprises) – can dried faecal sludge fuel the sanitation service chain?, In: WEDC conference 37, 2026 (6 pp.), Institutional Repository

Fuel potential of faecal sludge: calorific value results from Uganda, Ghana and Senegal

This research tested the viability of using faecal sludge (FS) as solid fuel – an end use that could unlock an environmentally and financially beneficial replacement for disposal oriented FS management, while replacing fossil energy. FS samples were collected from pit latrines, septic tanks, drying beds and stabilization ponds in three cities, Kumasi, Dakar and Kampala. For each sample, the average calorific value, solids and water content, and their variation with source and age were determined. The average calorific value of untreated FS across the three cities was 17.3 MJ/kg total solids (TS), which compares well with other biomass fuels. The age of FS did not affect its calorific value, nor did the reduction in COD that occurred while it was in drying beds. The TS content of FS depended on its source but ranged from 1 to 6% for sludge from septic tanks and pit latrines, respectively. Harnessing net energy from FS requires partial drying. The results indicate that sufficient drying occurs within two weeks in open-air drying beds, or in a matter of days with simple drying bed innovations.
Murray Muspratt, A.; Nakato, T.; Niwagaba, C.; Dione, H.; Kang, J.; Stupin, L.; Regulinski, J.; Mbéguéré, M.; Strande, L. (2014) Fuel potential of faecal sludge: calorific value results from Uganda, Ghana and Senegal, Journal of Water Sanitation and Hygiene for Development, 4(2), 223-230, doi:10.2166/washdev.2013.055, Institutional Repository

Faecal sludge – from waste to solid biofuel?

Research in urban areas of Senegal, Ghana and Uganda proved that there are widely untapped markets for faecal sludge end-products as financial drivers to sustain reliable and safe faecal sludge management. As a fuel, it especially shows promise as an industrial energy resource and a means to generate revenue.
Gold, M.; Murray, A.; Niwagaba, C.; Niang, S.; Strande, L. (2013) Faecal sludge – from waste to solid biofuel?, Sandec News, 14, 8, Institutional Repository

Faecal sludge drying beds: increasing drying rates for fuel resource recovery in Sub-Saharan Africa

In urban Sub-Saharan Africa, the collection and transport of faecal sludge (FS) typically ends up with FS directly dumped into the urban environment, as safe treatment and disposal options are too expensive or non-existent. Resource recovery from FS treatment, such as dried FS as an industrial fuel, could provide a financial incentive to increase access to FS management services. In Dakar, Senegal, enhanced drying to reduce the footprint of drying beds for fuel production was evaluated. Greenhouses did not increase drying rates over uncovered beds, however, daily mixing of FS on the surface of the beds resulted in a 6 day reduction to achieve 90% total solids (TS). FS was dried to 90% TS in 2 weeks for loading rates of 100 kg TS/m2*year, and 3 weeks for 150 kg TS/m2*year. The results indicate that with simple but innovative adaptations, footprints of treatment plants could be reduced and/or treatment capacities increased by 20%. FS can be adequately dried in Dakar to produce fuel, meaning 8.25 tons of dried FS could currently be produced daily, contributing 31,403 GJ/year fuel to industries. In addition, this financial incentive could reduce FS that is currently discharged untreated to the environment, and provide an additional 116,705 GJ/year.
Seck, A.; Gold, M.; Niang, S.; Mbéguéré, M.; Diop, C.; Strande, L. (2015) Faecal sludge drying beds: increasing drying rates for fuel resource recovery in Sub-Saharan Africa, Journal of Water Sanitation and Hygiene for Development, 5(1), 72-80, doi:10.2166/washdev.2014.213, Institutional Repository

Energy recovery with faecal sludge fuels in Kampala. Gold, M., Turyasiima, D., Studer, F., Tukahirwa, S., Nantambi, S., Arnheiter, R., Bleuler, M., Getkate, W., Schönborn, A., Niwagaba, C, Babu, M., Kanyesigye, C., Strande, L. Sandec News 2016

Identification of fodder plants for treatment with planted drying beds. Gueye, A., Mbéguéré, M., Diop, C., Niang, S., Strande, L. Sandec News 2016

Production of Pellets and Electricity from Faecal Sludge. Gold, M., Niwagaba, C., Studer, F., Getkate, W., Babu, M., Strande, L. Sandec News 2015

Waste heat recovery from industries for faecal sludge drying. Diener, S., Reiser, J., Mbéguéré, M., Strande, L. Sandec News 2012

Waste heat recovery from cement production for faecal sludge drying. Reiser, J., Diener, S., Mbèguèrè, M., Strande, L. 2012

Market driven approach

Market driven approach for faecal sludge treatment products

Inadequate management and treatment of faecal sludge continues to pose risks for public and environmental health. Given the variability of faecal sludge and location-specific nature of solutions, it is difficult to decide on treatment objectives and performance goals for treatment. The Market Driven Approach was developed as a quantitative methodology to determine which faecal sludge treatment products have the highest market potential in a defined location. This methodology provides a way to compare treatment products based on their real value for resource recovery. This paper discusses the results and lessons learned from field-testing in five cities across Africa and South-East Asia.
Andriessen, N.; Schoebitz, L.; Bassan, M.; Bollier, S.; Strande, L. (2017) Market driven approach for faecal sludge treatment products, In: WEDC conference 40, 2807 (6 pp.), Institutional Repository

Market driven approach for selection of faecal sludge treatment products

The goal for selecting treatment products based on resource recovery, is to define appropriate levels of treatment based on the desired end-use; generate revenue to offset treatment costs; and help ensure adequate operation of treatment plants, as they are producing a product to meet customer demand.
This market driven approach provides a framework to explore potential markets for faecal sludge treatment products. As markets vary significantly based on the local context, it is essential not to make assumptions based on experiences in other regions. The market driven approach can be applied in any context and region and provides a way to consistently and comparably determine potential market applications for faecal sludge treatment products. This information can then be used as a basis to evaluate appropriate market and business model strategies.
Implementation of this market driven approach requires a certain level of technical knowledge of faecal sludge management. A minimum level of required knowledge is covered in the following chapters from Faecal Sludge Management: Systems Approach for Implementation and Operation, which can be downloaded for free at www.sandec.ch/fsm_book (Strande et al. 2014): [...]
Schoebitz, L.; Andriessen, N.; Bollier, S.; Bassan, M.; Strande, L. (2016) Market driven approach for selection of faecal sludge treatment products, 30 p, Institutional Repository

A value proposition: resource recovery from faecal sludge—can it be the driver for improved sanitation?

There is currently a lack of access to affordable sanitation in urban areas of Sub-Saharan Africa. This study evaluated the potential for resource recovery from innovative faecal sludge treatment processes to generate a profit that could help sustain the sanitation service chain. A total of 242 interviews were conducted in Accra, Ghana; Dakar, Senegal; and Kampala, Uganda to compare markets in different cultural and regional contexts. Products identified to have potential market value include dry sludge as a fuel for combustion, biogas from anaerobic digestion, protein derived from sludge processing as animal feed, sludge as a component in building materials, and sludge as a soil conditioner. The market demand and potential revenue varied from city to city based on factors such as sludge characteristics, existing markets, local and regional industrial sectors, subsidies, and locally available materials. Use as a soil conditioner, which has been the most common end use of treated sludge, was not as profitable as other end uses. These findings should help policy and decision makers of sanitation service provision to design financially viable management systems based on resource recovery options.
Diener, S.; Semiyaga, S.; Niwagaba, C. B.; Muspratt, A. M.; Gning, J. B.; Mbéguéré, M.; Ennin, J. E.; Zurbrugg, C.; Strande, L. (2014) A value proposition: resource recovery from faecal sludge—can it be the driver for improved sanitation?, Resources, Conservation and Recycling, 88(1), 32-38, doi:10.1016/j.resconrec.2014.04.005, Institutional Repository

PURR - Partnership for Urban Resource Recovery. Initial assessment of sludge management and context in five cities: Son La, Lang Son, Hoa Binh, Bac Ninh, and Ba Ria

This summary report provides an overview of the highlights and key findings of the Initial Assessment Study that was conducted in Son La, Lang Son, Hoa Binh, Bac Ninh, and Ba Ria Vietnam as part of the PURR (Partnership for Urban Resource Recovery) Project. The purpose of the Initial Assessment Study was to provide an overview of the current status of sanitation and sludge management, the regulatory environment, and to identify local stakeholders. The study was conducted to develop an understanding of the local context to provide a basis for evaluating reasonable management and treatment options of faecal and wastewater sludge in each of the cities. Faecal sludge is the sludge that is stored in onsite sanitation technologies such as septic tanks and pit latrines. Wastewater sludge is produced in wastewater treatment plants (WWTPs) during the treatment of sewerage. Information in the report includes:
• the national institutional framework,
• the local environmental and socio-economic context,
• the water supply system,
• the wastewater management practices, stakeholders and infrastructures,
• the solid waste collection, transport and disposal system,
• the existing faecal sludge management habits. [...]
Bassan, M.; Dao, N.; Thuy, P.; Hoai, A. V.; Nguyen, V. A.; Strande, L. (2013) PURR - Partnership for Urban Resource Recovery. Initial assessment of sludge management and context in five cities: Son La, Lang Son, Hoa Binh, Bac Ninh, and Ba Ria, 54 p, Institutional Repository

Market Driven Approach Data Collection Tool.  Excel sheet

Market demand, technical and financial feasibility for faecal sludge use as industrial fuel Results from FaME (Faecal Management Enterprises) – can dried faecal sludge fuel the sanitation service chain? Gold, M., Niang, S., Niwagaba, C.B., Eder, G., Murray Muspratt, A., Diop, P.S., Strande, L.  37th WEDC International Conference, Hanoi Vietnam, 2014

Waste Supply and Availability in Hanoi, Vietnam (RRR Project. From Research to Implementation). Schoebitz, L., Nguyen, V.A., Hoa, Huyen, Strande, L. Eawag/Sandec July 2014

Waste Supply and Availability in Kampala, Uganda (RRR Project. From Research to Implementation). Schoebitz, L., Niwagaba, C., Strande, L. Eawag/Sandec May 2014

Kontakt

Nienke Andriessen Project Officer Tel. +41 58 765 5082 Send Mail
Dr. Linda Strande Tel. +41 58 765 5553 Send Mail