Interesting.

Please expound on your idea of where the fan should be?

Good morning Kathy.
To me this odour problem is one of design. Whilst there is a cost to having a fan creating negative pressure, I am convinced that this is the best way to handle the problem. I am a great supporter of urine diversion for more than just a pathogen risk reducer. The major proportion of odour is related to urine. It is the positioning of the fan that is the important issue. The principle is that the fan should pull the air from the bath/toilet room down into the latrine or compost bin, then vent to the atmosphere, rather than just venting the latrine. The lineal pull of a fan greatly falls away after a lineal run over 300mm, so the intention should be to design in such a way that this pull length works on the bathroom rather than the latrine/compost bin.
A further impediment to odour control is cultural differences resulting in the use of squat plates against pedestals or benches.
Ross

Thank you, Tore.

The results of our odor survey support your points. One additional factor in the level of odor is regular maintenance. Dirty latrines can result in less cleaning which creates a vicious circle. In general, no one solution is going to solve the odor problem, or be useful in all scenarios. In some instances, a filtration, or odor adsorption device could be the best option. Similarly, a fan may improve odor in the latrine, but cleaning may do even more if it is dirty inside.

Lastly, odor control mechanisms that remove odor causing chemicals from the air are very important to larger scale operations that are being developed as part of the Reinvent the Toilet initiative. Drying, burning, and other processes cause odors that are off-putting, and venting such things only moves the issue from the source to the surroundings. Eliminating odors could have a big impact on certain projects viability in the long run.

Kathy on behalf of the Duke odor team

Odor complaints can be one of the key reasons that toilets are not used. In general urine diverting toilets have lower odor levels than non-diverting toilets. In addiiton if you install a vent pipe that is exposed to the sun and goes at least one foot above the roof levels odors are further reduced due to negative pressure and odors being vented outdoors. If in addition you add a trap which can be a petroleum seal or any method to keep urine odors from the toilet area then complaints are reduced to almost zero.

Tore

Dear Sarah,

There a number of positive uses for biochar besides for odor control, including carbon sequestration, soil enhancement, and for filtration purposes, although some can quickly become controversial depending on whom you are talking to.

I recently wrote a review paper for Biomass Controls on biochar and its various uses that you may find helpful. I've attached it to this thread. In addition, I plan on continually updating this paper, and the latest version can be found on Biomass Control's website, under the resources tab, under research papers.

Let me know if you have any questions on its content, hopefully it is useful in giving you a better understanding!

Dear Kathy,
It was interesting to read about the use of biochar for odour control, are there any other positive consequences of using biochar other than odour control? Would the resulting mixture be more valuable for reuse? I have heard a little about the role biochar can play in carbon sequestration, and it reminds me that the opportunities for sanitation in climate mitigation don't get a lot of attention among climate experts.
best,
Sarah

Hi Kathy
It will also be useful to identify whether the toilets studied are actually composting or simply containers for excreta. The term composting toilet is often misleading. Urine-diverting dry toilets receiving ash, lime, sawdust, etc. are not designed to compost. Toilets that simply mix urine and faeces and then wait for emptying are not composting either.

I did a testimony for the Vermont legislature just on this question earlier this year.



Best wishes
--Arno

Hello Mr. Mughal,

Thank you for your interest. As soon as we have completed the survey and analysis of the data, I hope to post it on the forum.

Best Regards,
Kathy

Dear Kathy,

I'm not sure whether I'm on the same page with you, but could you kindly post your full "survey" (would that be a study?) on this forum? That horizontal bar chart is very interesting, and I would like to seek the background details.

Regards,

F H Mughal

Hi Milli,

In case you haven't seen it, this thread regarding odor from composting toilets might be helpful...
forum.susana.org/forum/categories/70-com...omposting-in-general

Below is preliminary data from our odor survey that highlights some of the key factors influencing odor level. It gives some indication of the relative impact each factor has on perceived odor.



We will not be testing any specific type of toilet as part of our study, but rather testing different medium for and methods of reducing odor.

Best Regards,
Kathy

Kathy,

We have used biochar as an odor control medium with good success. There are several low tech production methods. Attached is a link to a paper on biochar we posted earlier this year.

media.wix.com/ugd/7b6861_8f67f15f71ea4d74b906d91ccbf04083.pdf

Best regards,



Jeff

Dear Milli,

While ecosan toilets are usually less prone to smell than pit latrines, as far as I am concerned all of the processes usually used in ecosan toilets can smell. Assuming the toilets are used correctly, proper ventilation is the key to combat odors. What is usually working wonders is the use of a small ventilator (or fan; if nothing else is helping). One or two Watts of power rating are usually enough, so if there is no power supply, a mini solar system with a fan per stand should solve your problems.

For an example, you can have a look at the toilet described at the end of the following set of photos:
www.flickr.com/photos/gtzecosan/sets/72157631160051774/

bucket ecosan toilet by SuSanA Secretariat , on Flickr

bucket ecosan toilet by SuSanA Secretariat , on Flickr

It's a commercially available urine diverting bucket toilet which I have retrofitted with that green went pipe and a small fan (usually used for CPU cooling). The power source was from a solar (12 Volt, less than one Watt). While the toilet was developing an intense stench without the fan, even with the addition of a lot of wood ash, the odors almost completely disappeared with the fan.

Another interesting approach was once mentioned by Cécile on this forum - the addition of cellulosic material which is triggering an enzymatic reaction that is suppressing the formation of odor - see post #12659 here . I think this is a mechanism which deserves to be known a lot more widely in the 'community' (I wasn't aware of it before).

Greetings, H-A