@Christoph, Thanks, I have clarified the text.
The content of the UDDT you can dump in a biogas reactor for sanitization and gas production. The UDT, being a wet system (even anal wash is possible), can be directly over a biogas reactor. Since the ATAD is also a wet processing system, it is likely that methane gas with bad odour is generated. This is actually the case. Given the importance and the danger of global warming, one need to ask how methane gas is avoided, and if the ATAD is a suitable system in this context.

Hi.

We've just finished our 6 month Windmill-ATAD system and can add to the discussion of methane. Surely no one wants to make methane as an integral part of a decentralized system. It is just too dangerous.

Our continuous ORP data shows over a span of wind speeds and an underpowered windmill, reactor liquid never enters the methanogenisis range and except for a brief time span where we "wired" the system to be in the high aerobic range, It was steady in the denitrification range. We had no observable odors. Regards, Jim

Here is the photo of our system, capable of handling 15-20 people. No power, no water needs, no chemicals, low maintenance, cheap (BMGF Grant Requirements) Regards, JWB

All sanitation systems have advantages and disadvantages, wheres we try to reduce these disadvantages. Sanitation systems however, produce methane somewhere along the line, where dry or wet systems.
In relation to sanitation you can possibly define three levels; Private, Public and Global.

Private is appealing to the individual user and includes personal and family health, personal expenses, comfort, recurrent cost, etc.

Public includes the cost of delivering water, the entire sewerage system and the sewage cleaning activity or other communal services that are not individual. These expenses however, are somehow paid for by the individuals through specific tariffs or general taxes. General public health related to no sanitation or better sanitation also falls in this category. When we look at sanitation systems we see that more water results in more sewerage, through which the cleaning also becomes more costly.

Global is related to the impact of human sanitation on the environment. One of the most important aspects is the cleaning of the sewage so that it does not affect negatively all our surface water, irrigation, fish or algae development, etc. The emissions of CO2 and methane gas are part of the global and environmental issues. Human excreta produces methane gas when aerated or in biogas reactors. While the methane gas is captured in biogas reactors and can be burned off to CO2, with other sanitation systems this methane is emitted into the atmosphere. It is 21 time more insulating as a greenhouse gas than CO2. Human faeces composted or aerated including from septic tanks and ATAD is there fore a major contributor to global warming. Global warming in turn leads to permanent melting of more polar ice, larger and more frequent tornadoes, expansion of deserts and more droughts in some regions with resulting food shortages, and excess of rain worldwide causing floods, and not the least of all the rising of sea level with two storeys, requiring a billion people to move to higher land and loss of agricultural land. The book/film "An Inconvenient Truth" gives a short account of the issue.

It is my opinion therefore that all sanitation systems need to be assessed on CO2 and more import on methane emissions (NH4) into the atmosphere and rated. This can be an interesting task for SuSanA. Most likely the least damaging systems are the UDT models in combination with a biogas reactor, from which the biogas is used for cooking.

One more thing. On our next battery of runs, I will monitor lower explosion limits and try to analyze for CO2. This may be months from now. Regards, Jim

Dear Jim,

I was a little surprised when you wrote " Surely no one wants to make methane as an integral part of a decentralized system. It is just too dangerous".

I assume that you don't consider bio-gas technology as too dangerous to use? If so I would be interested in your reasoning.

@ Sjoerd, I agree it would be interesting to look at sustainable sanitation from a global warming perspective as well. As long as we don't tie it up to carbon credits or similar. (I know we disagree there) By the way, here in Nepal we have some bio-gas attached UD toilets, seems to work fine as-long as you have a couple of animals to create enough feed-stock (or connect a lot more toilets).

Kind regards

Marijn Zandee

@marijn. I think that an important priority is to reduce any methane emissions from sanitation systems through the integration of biogas reactors with sewage. At city level the UASB is being used but other city sewerage make the sludge dangerous. Therefore direct toilet based biogas reactor is preferred.

In Nepal the biogas project attaches the house pourflush toilets to their small farm based biogas reactor, but urban development for cluster houses is not yet done. The few cattle produce much more dung of good quality than the household members. When we did the first methane leakage measurements on these small rural biogas reactors (now over 250.000 constructed) it appeared that there was substantial leakage. See sketch. This leakage was not resolved but the project managed to get good carbon credits anyhow, co-financing the management costs.

In developing toilet systems you can forget the carbon credits because you need massive results to make it economic or recover the investments. But when you have large numbers it is a worthwhile financial contribution. If some countries continue to frustrate the Kyoto protocol that financing may not be sustainable.

@Jim. I figure that blowing air through toilet and animal faecs with methane gas produces an explosive mixture. It will be dangerous to burn this mixture off. When not done it contribute strongly to global heating. That is why it is important to quantify the methane production of all sanitation units and design systems that capture the biogas (without air).

We will see. I believe it depends on the oxidation reduction potential. Regards and thanks for pointing out a possible problem to solve. Regards, Jim

Your correct, my comments were only aimed at the windmill ATAD we are developing.
Surely there are 1000s of biogas systems operating safely around the world. Thanks for the correction. Jim

I've analyzed much of the large set of computer-logged data and now have a presentation. After I submit it to BMGF, I will try to submit it to SuSanNa. Probably a couple of weeks. Regards, Jim

Hi Jim,

It sounds like a really interesting project. I was wondering if you have been able to quantify the volume of air produced ie cubic meters per hour or day under varying wind conditions?

Thanks, I thought I saw somewhere and article or publication of how to stop methane production in an aerobic system. Does anyone else remember this? Jim