SuSanA - Forum Kunena Site Syndication Sat, 25 Oct 2014 06:58:44 +0000 Kunena 1.6 SuSanA - Forum en-gb Re: Pivot Plant: Converting human waste to fuel to finance complete sanitation (Waste Enterprisers Holding and Pivot Ltd, Kenya) - by: pkjha
Yield of degraded sludge from pit latrine vary widely. It depends on medium of cleaning- water or paper etc, soil condition, retention time in pit. Further per capita quantity of human excreta also varies widely in different regions/ countries, also depending on dietary habit- vegetarian or non-vegetarian. I got 220 kg of degraded sludge from a leach pit toilet used by 4 members of a family daily. It was filled in 3 years and sludge was taken out after 2 years of its filling. Soil condition was clay sandy with water table more than 25 meters. It shows 17-18 kg of sludge per capita per year. In case of clay soil or high water table, sludge will have higher moisture content and hence higher weight.

Resource recovery from excreta or faecal sludge Thu, 16 Oct 2014 14:08:06 +0000
Re: Pivot Plant: Converting human waste to fuel to finance complete sanitation (Waste Enterprisers Holding and Pivot Ltd, Kenya) - by: kevintayler
Thanks for the reply from AMurray - sorry that I can't figure out your first name from the post - I did not realize that until I started to reply.

I think that my basic point regarding sludge quantity remains. The 60 litres per person per year figure quoted by EAWAG is based on earlier work and is not necessarily accurate. There is quite a lot of subsequent work on sludge quantities, which generally shows that accumulation rates are lower than this - although higher in Africa than in Asia. The other factor is the solids content of the sludge. This can indeed be quite high, as work by the people in e-Thekwini has shown.

The other factor to take into account is that the solids content of sludge tends to decrease with time so that there will generally be more solids content in fresh sludge than in digested sludge.

Overall, my point is that this is a key figure for the business case and is something that really needs further investigation. My own review of the literature shows that there are major variations in the figures for solid content of sludge.

On the other point, delivery of sludge to the processing site, I think that more will be needed to develop an effective collection and transport system. The system described in the link seems to rely entirely on gulpers and 50 gallon drums, which will presumably be carried in pick-ups. I wonder if anyone has done any analysis of the financial aspects of this. I would have thought that there would be a need for transfer stations with larger trucks to move sludge from residential areas to the processing plant. It would probably be worthwhile to explore different scenarios, bearing in mind Eric Dudley's question - what might go wrong?

I hope that this is helpful

Resource recovery from excreta or faecal sludge Thu, 16 Oct 2014 06:42:54 +0000
Re: Pivot Plant: Converting human waste to fuel to finance complete sanitation (Waste Enterprisers Holding and Pivot Ltd, Kenya) - by: amurray
Thanks for your continued interest and engagement!

In short, you're right. The total solids numbers that Tim quoted are based on our best available information and make assumptions about collection rates, total solids generation, and freshness of the FS upon collection.

However, total solids accumulation on the order of 15 kg/person•year is supported in the literature. Eawag (1998) quotes pit latrine accumulation of 0.06 m3/person•year @ 20% solids after one year. This amounts to 12 kg solids. Cofie (2010) quotes an average daily solids accumulation of 47 g/person, which amounts to 17 kg solids/person•year. I'd also point out that our company was part of the FaME team that worked in Accra, Kampala, and Dakar and the reason the per capita numbers appear low for the latter two cities is that the researchers working on that portion of the study only counted FS that is currently being properly collected and transported to a designated dumping site (whether for treatment or straight disposal). They were intentionally conservative in order to calculate the minimum financial return on the reuse of FS that could be readily accessed.

Like many (dare I say most?) cities in sub-Saharan Africa, the majority of FS generated in the slum/informal settlements of Kampala and Dakar is informally emptied and dumped within the community itself. Mombasa is no exception, however, we're already working with pit latrine emptiers in informal communities to determine effective means and incentives for getting the waste out of the communities and to our production plant. (You can learn more about that work here: )

We'll continue to keep this post updated with our progress and production rates as we learn more.]]>
Resource recovery from excreta or faecal sludge Mon, 13 Oct 2014 13:15:36 +0000
Re: Energy recovery & waste treatment with floating biodigesters (Tonle Sap Lake, Cambodia - LLEE) - by: robhughes I just wanted to update you about this project. Our pilot & demonstrations were fairly successful at showing operation in some quite challenging situations and I'd be willing to share further information for anyone interested.

We have a 4 in 10 chance of receiving AUD$500,000 to further improve the small scale and adaptable biodigesters we have developed and establish the business models and enterprises to make them more widely accessible and scale up. Despite successful and promising pilots and demonstrations we have so far been unable to find funding to continue the work and get it ‘across the line’ to be self-sustaining in the community, but may be about to do that with this grant.

Live & Learn will be partnering with Engineers Without Borders Australia, who will be coordinating the overall project and linking to other strategic partners.

There are 10 finalists, and there is currently a public online vote that will determine at least one of the 4 grantees, and may influence the result of the other 3. So it would be very helpful if you could vote for “Engineers Without Borders Australia”, here: , or here:

Additionally, if you could further publicise this and encourage voting, it could be very helpful. There are facebook, twitter, and website links below for your use.

The biodigesters are designed to not be dependent on subsidies, ideal ground conditions, or large numbers of animals, which are some of the main barriers to an otherwise quite appropriate technology. Let me know if you would like more info that isn’t covered in this thread above!

Thanks a lot!
Resource recovery from excreta or faecal sludge Mon, 06 Oct 2014 04:46:27 +0000
Re: Nitrification reactor set up - by: winniek [Start of Page 4 of the discussion]

I will start with suspended biomass and ensure the biomass isn't washed out and recycling just incase.
Thanks a lot.]]>
Resource recovery from excreta or faecal sludge Sun, 31 Aug 2014 15:39:31 +0000
Re: Nitrification reactor set up - by: kudert Resource recovery from excreta or faecal sludge Sun, 31 Aug 2014 15:13:12 +0000 Re: Nitrification reactor set up - by: winniek Thanks for the attached and I have already read through the paper.
I was thinking of using this "hybrid membrane-aerated biofilm reactor (MABR) was
used for the nitrification experiment" as i believe i wont have easy access to the Kaldnes rings.
I have seen the reactor but if you have more pictures of it. I would be grateful as i will get a better understanding on the set-up]]>
Resource recovery from excreta or faecal sludge Sun, 31 Aug 2014 15:08:42 +0000
Re: Nitrification reactor set up - by: kudert 4+. Since nitrification lowers the pH value, this amount of ammonium is not lost during distillation (except for a very small fraction). I attach a paper, in which we describe the fate of ammonia during distillation in more detail.]]> Resource recovery from excreta or faecal sludge Sun, 31 Aug 2014 14:50:42 +0000 Re: Nitrification reactor set up - by: winniek did you anaylse the effluent N- concentrations, i.e. NH4+, NO2- and NO3- ? is so what was were there.
If the urine was partially nitrified does it mean only 50% of ammonium was converted to N03- . In that case what happened to the rest of the NH4+ when the effluent proceeded to the vacuum distiller]]>
Resource recovery from excreta or faecal sludge Sun, 31 Aug 2014 14:44:08 +0000
Re: Nitrification reactor set up - by: kudert
In our current system we use biofilm carriers. The fill rate is about 60%. The biofilm carriers are mixed by aeration and the oxygen concentration is therefore close to saturation. The maximum ammonia oxidation rate is about 400 gN/m3/d. The minimum hydraulic retention time can be calculated based on the ammonia concentration in the influent and the ammonia oxidation rate. For example, if the ammonia concentration in the influent is 4000 gN/m3/d, the hydraulic retention time will be 5 days, because half of the ammonia is oxidized.
The pH has to be kept in a narrow range by adjusting the influent rate. If the influent concentration and the temperature are constant, this can done by hand otherwise you might want to use a process controller, which keeps the pH in a narrow range of 0.1 units by switching the influent on and off. An optimal pH value is 6.
A detailed description of our pilot reactor can be downloaded at:

Let me know, if you need any additional information.
Resource recovery from excreta or faecal sludge Sun, 31 Aug 2014 13:16:48 +0000
Re: Nitrification reactor set up - by: winniek I am interested in carrying out a similar lab experiment and i would want to know more about the reactor set up that you used. What type of reactor, what was the flow rate the Hydraulic retention time , the volumes the concentration of the Dissolved oxygen. Basically the methodology and reactor set up. Thank you very much]]> Resource recovery from excreta or faecal sludge Wed, 27 Aug 2014 10:43:01 +0000 Re: Pivot Plant: Converting human waste to fuel to finance complete sanitation (Waste Enterprisers Holding and Pivot Ltd, Kenya) - by: kevintayler
Thanks for your earlier answer. This topic has stimulated my interest. I have been working on other aspects of FSM over the last 3 years but have not really looked at re-use options.

I would like to return to my initial question concerning the amount of dried sludge available. Based on a population of 1.2 million, the 50 tonnes of dried solids per day requires around 15kg of dried solids per person per year. I assume that the 50 tonnes per year applies to total solids (TS). I gave some rough calculations in my earlier email, based on figures from South Africa but I have done some further research, using information from both the FAME report on Accra, Dakar and Kampala and older studies of septic tanks from Europe and North America. (See for the FAME report).

All these studies give per-capita TS production figures of the order of 2 - 4kg/yr.The only exception is Accra where the figure for public latrine sludge comes out at 13.8kg/c.yr but this is assuming that sludge production is 730 litres per capita per year, which is very high and presumably reflects the fact that almost fresh faeces is regularly removed from public toilets.

Based on these figures, I think that the 50 tonnes per day figure is optimistic, if it refers to total solids. It may be that it refers to partially dried solids but this would have implications for the calorific value. A study conducted for the work in Accra, Kampala and Dakar arrived at a figure of 17.3 MJ/kg total solids (TS). (See and clearly the TS figure is the relevant one.

The calculation in my earlier email, based on information from South Africa, gives a higher per-capita TS figure. Interestingly, the South African figures are taken from pit latrines with very low water contents - typically around 65 - 75% depending on depth. At these moisture contents, sludge will not be liquid and will have to be dug out.

One last point about the FAME calculations is that they assume high per-capita sludge volumes, 573 litres per person per year in the case of Dakar and around 290 litres per person per year in Kampala. These figures are much higher than those generally quoted in the literature (20 - 70 litres per person per year for pit latrines and leach-pits and 70 - 100 litres per person per year for septic tanks (mainly based on research in Europe and North America).

Overall, it seems to me that there are quite a lot of uncertainties here. Perhaps the next step after determining the technical viability of the approach should be to carry out more detailed assessment of the total amount of dried sludge that will actually be available. One point to note here is that there is a need to accurately assess both the TS content of septage and the amount of septage produced, neither of which is easy. The FAME reports do try to cross-check, using different approaches but I would still be worried about their assumptions on per-capita production.

I hope that this is helpful

Resource recovery from excreta or faecal sludge Thu, 21 Aug 2014 09:37:02 +0000
Re: Pivot Plant: Converting human waste to fuel to finance complete sanitation (Waste Enterprisers Holding and Pivot Ltd, Kenya) - by: timwikoff
Great questions and thanks for your interest in our work! We are currently under construction in Mombasa as well as working on some parallel projects for the sourcing of FS from the poorer areas of the city. Therefore, I'll have to ask for patience from the audience on answers to some of these questions - we would like to have specifics from the plant in full operation before spouting off.

Kevin to address your specific questions on volumes available we did a similar calculation and based that on the total population living in and very near Mombasa of 1.2 million people. Our estimate came to 50 tons per day. I don't have our formula or source off the top of my head but can get it for you. I believe we used WHO for our per person per day estimates but I'll have to check.

In terms of collection rate, we are estimating 80% collection at full scale - we are anticipating a minimum of a 2-3 year ramp up time to get there.

The other important aspect of collection that I should note is that we don't plan to do much of it ourselves. The parallel work we have running is to figure out the best incentives for local entrepreneurs to bring us sludge. We would love to pair technology coming from other Gates grantees with local business people in Mombasa and enable a thriving local market for sludge. The other avenue to pursue, again with Gates grantees is partnering with firms that are experts in collection but not "productizing" the FS. Firms like Sanergy or WSUP come to mind. But before we are able to do any of that, we need to get our demonstration plant built so that we fully understand our internal economics and operations and can go to potential partners with a solid proposal.]]>
Resource recovery from excreta or faecal sludge Fri, 08 Aug 2014 18:29:13 +0000
Re: Pivot Plant: Converting human waste to fuel to finance complete sanitation (Waste Enterprisers Holding and Pivot Ltd, Kenya) - by: kevintayler
I would like to follow up on Chris Canaday's question about the economic costs of the system. It would also be useful if you could provide some further information on how you plan to go to scale.

You say that the present plant can produce about 5 tonnes of fuel per day. You don't say what the ratio of fuel produced to feedstock of dried sludge is but I assume that it is not more than one.

Long-term sludge accumulation rates are typically of the order of 25 - 50 litres per person per year. According to the work done by Nwaneri et al in South Africa, the average water content of the top metre in a pit latrine, the part from which sludge is most likely to be removed is about 75%. Assuming that sludge removal equates to 40 litres per person per year, that equates to about 10kg of dry solids per year. The population of Mombasa is around 1 million so the amount of dry solids generated if every person in the city used a pit latrine and the sludge from all these pit latrines was collected, the amount of dry solids available would be about 10,000 tonnes per year or about 27 tonnes per day. My question here is whether there will be enough sludge to keep your proposed 40 tonnes per day plant going, bearing in mind that it will be hard to get 100% coverage of sludge collection services. Many people in peripheral areas are likely to build a new pit rather than empty their old one.

The economic question concerns the relationship of the cost of bringing all sludge to a single treatment site (as opposed to more localized solutions that involve less transport)and the sales potential from the fuel produced by the process. My impression is that the transport costs are going to be rather high. A related point is the balance between the fuel produced and the fuel used in bringing sludge to the treatment point.

I guess that you have looked at these points so it would be good if you can expand on them.


Kevin Tayler]]>
Resource recovery from excreta or faecal sludge Fri, 08 Aug 2014 13:14:25 +0000
Re: Faecal sludge to biodiesel (Columbia University, USA and Kumasi, Ghana) - by: psewor This results calls for critical rethinking to save our water bodies and also health of the people.
Your design if adopted would add value to human waste (that is from "waste to money").

I have carried out critical comparative case study analysis between Ghana and United Kingdom on treatment and disposal of liquid waste, its effect on water bodies. The book can be found at Amazon online library.

I wish you all the best.]]>
Resource recovery from excreta or faecal sludge Thu, 07 Aug 2014 08:32:02 +0000