Improved SSS!

SSS stands for shit supply system. It is the first step in an innovative system where human excrements is transformed into biogas and fertilizer. This SSS can easily be made from materials available in the household. An open invitation is extended to the residents of droevendaal to participate.

The S(hit) is collected in a container, lined with newspaper, placed inside the toiletbowl. Some saw dust is added to soak up moisture, and reduce smell.

The S is quickly dropped into a trash can outside the front door. Because of the sawdust and newspaper, the contents are dry, thus there is very little odour. In addition, the trash can has a tight lid so, only a slight odour occurs when opening the lid.

From here, there are two options. Composting or Anaerobic Digestion. In my system we use AD. The contents of the trash can are delivered once every few days, or as needed to the reactor, where they are mixed with digestate or water, and chopped into slurry (roughly 5% solids) by a drill with a blade on the end.

The slurry is then dropped taken through a valve into the insulated reactor (100L) where biogas is produced. The reactor is maintained at 35 C and occasionally stirred by hand. Electricity consumption of the drill and heater system is much lower than biogas energy produced, but varies througout the year depending on ambient temperature.

The liquid effluent is emptied into a bucket or jerry can and used as fertilizer. It can be pasteurized at 70 C for 1 hour to fulfill EU ABPR. This liquid has minimal odour, and very little organic matter. It is basically water with nutrients.

The biogas from the system is collected in a floating inverted drum, which is connected to the reactor and also the kitchen stove.

In the kitchen, one element is connected to the biogas pipe. The pressure from the weight of the floating drum is sufficient for a strong flame (there is no pressure regulator on the gas pipe). Roughly 15 minutes of cooking can be achieved, per person per day with excreta and newspaper. Adding degradable kitchen waste can double the gas production.

Gorilla Blackwater Plant

UPDATE: February 2010: Struvite from seawater and urine process demonstrated in Savu, Indonesia. A lot of interest from local students and farmers, who said they would save their urine, try the process, dry the struvite and use it instead of imported phosphate fertilizer.

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The Gorilla Blackwater Plant

(Wageningen, The Netherlands)

Prepared by Kealan Gell
November 1, 2009

Summary
The project converts the blackwater, or human excreta, from one student household into biogas and fertilizers, which are safe for food production. Compared to conventional sewage treatment and food production, this system reduces resource depletion, pollution and greenhouse gas emissions.

Quote
Let us abandon all consumption and pollution. Let us just eat and excrete.

Actors
Residents of Droevendaalsesteeg 87, 93, and 99, Wageningen, the Netherlands
Designed and operated by Kealan Gell
Some equipment donated by Dr. Gatze Lettinga
Support and inspiration from countless people and organizations, especially the
Community Composting Network, UK

Description
Urine is collected in a unisex odor-proof urine collection vessel, as shown in Figure 1. Urea is hydrolyzed in the collection vessel. Seawater, a source of magnesium ions, is added at a 1:4 volumetric ratio of seawater to urine (Figure 2). Mixing and settling, each for 15 minutes followed by decanting, produces 0.10 mm diameter struvite crystals, which are air-dried, shown in Figures 3 and 4. Struvite (12% P by mass) has a similar effectiveness, plant availability and P content to triple super phosphate (19% P by mass). Feces are collected in a dry toilet, covered with sawdust or paper to eliminate odor as shown in Figure 5. Feces are then mixed with paper and ground food waste, pasteurized at 70 C for 1 hour, and digested to produce biogas and safe liquid fertilizer, which includes stable organic matter. Digester is show in Figure 6. Currently electricity is used for heating the digester and pasteurizer, however in the
future, biogas will be used. Biogas is currently used for cooking, Figure 7. The liquid fertilizer, Figure 8, is applied in the garden. Fertilizer products contain very low levels of pathogens, metals, hormones and pharmaceuticals. Tests have been done to ensure compliance with Dutch soil regulations, EU animal byproducts regulations and Dutch fertilizer regulations. An evaluation of this system should consider the alternative impacts of conventional sewage treatment and fertilizer production, including drinking water treatment and delivery, sewage transportation network, energy used for carbon and nutrient removal and loss, and phosphate fertilizer mining, depletion of P, processing and transportation, as well as overall self sufficiency, resilience and pollution.

Figure 1. Urine collection vessel



Figure 2. Before (left) and after (right) sea water addition

Figure 3. Drying struvite crystals

Figure 4. Microscopic photos of struvite crystals

Figure 5. Dry toilet with saw-dust

Figure 6. Anaerobic digester with insulation and heater

Figure 7. Biogas cooking

Figure 8. Digestate, liquid mineralized fertilizer