Dear Rodrigo,

I did my bachelor´s thesis in 2010 about the characteristics of toilet paper, as my home university was also thinking about the question if the C in the toilet paper could help the process of treating wastewater in decentralised plants close tot he highways, where there is mostly urine and less faeces in the wastewater.

As Florian already said, toilet paper consists mostly of cellulose, the water content varys from 5 to 10 % of the weight. Numbers from 2009 say that in Germany 3.8 Mrd. t/a toilet paper were used. But it’s hard to know all there characteristics, as there are around 100 different kinds of toilet paper with different structure and also different solubility.

I only found 2 numbers concerning the C-content of toilet paper and the amount that is used per person in average. Unfortunately I don’t have the books with me, but the numbers I found in my research were the following (data was given for Germany):

11.5 g COD/(person * day)
[in: Neuartige Sanitärsysteme: Begriffe, Stoffströme, Behandlung von Schwarz-, Braun-, Gelb-, Grau- und Regenwasser, Stoffliche Nutzung. Lehrmaterial der Bauhausuniversität Weimar mit freundlicher Genehmigung der DWA. 2009]

or

5 g undissolved Carbon (Cellulose)/ (person * day), considering 1 g carbon = 1 g CSB in the communal wasterwater (5g cellulose come from 14 sheets toilet paper with a grammage of 30g/m2, if I get it right)
[in: P. Koppe und A. Stozek: Kommunales Abwasser – Seine Inhaltsstoffe nach Herkunft, Zusammensetzung und Reaktion im Reinigungsprozesseinschliesslich Klärschlämme. 1999. ISBN 3-8027-2833-5]

According to a responsible person of the communal wasetwater treatment plant in Jena, Germany, the wasterwater from a paper recycling plant seems to help the processes of the communal WWTP. So there should be a connection between the C-content in paper and wasterwater treatment processes, but not sure how far you can use these numbers for composting processes (as compost piles shouldn’t contain that much water that might be necessary for the solubility).

Therefore I totally agree that test would be necessary. I was wondering for which place or country you are doing the mass balance as the paper quality and amount will vary very strong from country to country.

Best regards,
Sabine

Dear all,

Some data concerning toilet paper:
The daily average consumption in Germany is 15g per person, which is 20 toilet papers. This is very high and of course other applications than anal cleansing are included. More realistic seems to be 7g to 10g per person (10 to 13 papers) (Guttormsen u. Pedersen (1978), Naudascher (2000)).

As part of her dissertation (in German), Naudascher investigated the influence of toilet paper towards the C:N ratio in various compositions. The C:N of toilet paper resulted in an average value of 318. There was not much difference in the tests with and without toilet paper, but a small support of carbon and organic, if bark chips were added (Naudascher, Imke: Kompostierung menschlicher Ausscheidungen durch Verwendung biologischer Trockentoiletten (2000), University of Karlsruhe).

Paper has a C:N ratio from 150 to 1000. Asking some manufacturers, before I published the German book "Komposttoiletten" in 2008, a C:N ratio of 1000 was estimated.

I hope, this is of any help.
Greetings

Wolfgang

I think it might be relevant to bear in mind that the high C materials (toilet paper vs leaves or sawdust) are very different microbiologically. The leaves and sawdust have an organised structure (to micro-organisms) and contribute a wealth of bacteria and fungi, whereas the toilet paper is highly processed and virtually sterile.
Sewage sludge (if referring to solids after WWT) is usually far too wet to compost, has had the soluble nutrients leached away and is anaerobic, slumping when piled.
Faeces and high C materials from UDDT, collected in a region of low humidity or high temperatures, might end up too dry for composting, though could perhaps be vermicomposted.
Biodigestion of pig wastes with useful by-products is explained here: dl.dropboxusercontent.com/u/22013094/Pap...o%20Biodigestion.pdf
I feel sanitation could learn from livestock farmers!

Thanks Florian, I changed my mass balance counting an 45% mass/mass carbon on celulose (C6-H10-O5) using the molecular wheights, and 8,9 kg of toilet paper per year. It raises the c:n in one unit in most of the cases, so it's not very much.

Taking in count that and 500 g daily of solid vegetal wastes, 80% moisture, and 4 times the weight in carbon-rich materials, the balance shows ~40% moisture and c:n ratio ~35, with different carbon-rich additives, that in theory, from a nutrient balance in excel, it's an apropriate pre-compost.


But it's important the areation and the liquids, that i'm not counting in this specific analysis, and maybe it's enough to make the composting fail. According to the compost that I have in my yard (that i'm NOT gonna talk about in my paper, or maybe I will?), the compresion after the firt stages in degradation of humid, unstable organis matter, specially fruits (SPECIALLY WATERMELONS), it's enough to make a compost fail. Dude, the smell in my yard was awfull .

Thanks for the help everybody!!

RodrigoBIS wrote: I need to make a full analisis of the choices that I have when you use a UDDT, and for now I would say that dehydrating it's easier, but I need a full answer with calculus, specially how much carbon rich material I have to add and why. I showed in my last post that with mass balance, equilibrating the c:n ratio to the minimal (~20), using diferent additives, there's a lack of moisture when you reach that ratio, that's why there's a need of water, and also, many references, even in Chile, suport that when you're composting faeces.

Rodrigo, nobody can give you a full analysis of materials that are very varied in a particular situation that you are in. I believe that we are all only telling you the same things - that you need to add a lot of carbon to get faeces to compost and that you are unlikely to need to add water to it. In a confined space you are not going to need to add additional water. Even in a large compost windrow it is unusual that you would need to add water to a co-compost of sewage sludge - usually the problem is that it is far too wet.

Is that volume of carbon rich material gonna diminish considerable with the toilet paper?

The C:N ratio might be affected by the addition of toilet paper, but as I have explained to you above, it is very unlikely to help compost the sludge. You need to add other carbon rich material.

I need the carbon content of toilet paper for make the demonstration. The results I posted of additives are in volume, 7 litres of dry leaves it's too much volume for each defecation, the mass proportion it's in the order of 3 with the faeces, and definitely with a proportion of 5 it's gonna like 10 Lt of leaves, too much. so I want to make it less with toilet paper.

Composting is not something you can work out on a spreadsheet Rodrigo. Toilet paper is not significantly going to affect the C:N ratio of the sludge unless you are adding very large amounts of paper. As I explained above, paper and faeces does not compost together well even if you know the exact C:N rations of the materials you are adding in optimal conditions.

But in a composting vault in a toilet, maybe it's gonna make the composting harder I agree, maybe working in the minimal moisture content required for composting will guarantee a good composting, but adording to the mass balance I showed, there's still a lack of moisture (all values are in the order of 20% moisture)

The problem is not too little water, but too much Nitrogen and too little oxygen.

RodrigoBIS wrote: I need the carbon content of toilet paper for make the demonstration.

Paper is mostly made up of cellulose, and cellulose has a carbon content of 444 g / kg (assuming zero moisture). Question is how much toilet paper is used typically...

I agree with what Joe said, if you want to really know it, you'll need to measure it. Taking fresh material from existing UDDTs could be good for sampling feaces+ toilet paper.

Hi,
there are several difficulties of getting good composting to work inside a toilet. Besides the challenge of maintaining a near optimum C:N ratio and moisture content, the main difficulty is to ensure good aeration. This is not really possible without frequently manually mixing the heap. Another difficulty is to manage the liquids leaking from the composting heap, which is small in quantitiy but highly loaded in organic matter and pathogens, thus you have another waste stream (besides urine and compost) to manage.

All reasons why a dehydration toilet is more easy to handle, the only rule being minimizing liquids getting into the toilet vault.

If you want to do composting, much easier to use UDDTs and then do external co-composting of the dried fecal matter collected from a larger number of UDDTs togehter with other vegetal waste. Then you can do it on a larger scale where moisture and the right mixture of materials can be much easier controlled than in a large number of toilet vaults.

Best regards,
FLorian

I need to make a full analisis of the choices that I have when you use a UDDT, and for now I would say that dehydrating it's easier, but I need a full answer with calculus, specially how much carbon rich material I have to add and why. I showed in my last post that with mass balance, equilibrating the c:n ratio to the minimal (~20), using diferent additives, there's a lack of moisture when you reach that ratio, that's why there's a need of water, and also, many references, even in Chile, suport that when you're composting faeces.

Is that volume of carbon rich material gonna diminish considerable with the toilet paper?
I need the carbon content of toilet paper for make the demonstration. The results I posted of additives are in volume, 7 litres of dry leaves it's too much volume for each defecation, the mass proportion it's in the order of 3 with the faeces, and definitely with a proportion of 5 it's gonna like 10 Lt of leaves, too much. so I want to make it less with toilet paper.

But in a composting vault in a toilet, maybe it's gonna make the composting harder I agree, maybe working in the minimal moisture content required for composting will guarantee a good composting, but adording to the mass balance I showed, there's still a lack of moisture (all values are in the order of 20% moisture)

Also I'm still not clear why you think adding water will help.

Composting is an aerobic microbiological process. Limiting the amount of oxygen by doing it in a confined space will inevitably lead to sub-optimal conditions and may not achieve the sanitation results or mass reduction you expect.

Well a UDDT is a dehydrating toilet and isn't a composting toilet. So you're talking about two different things.

But you are right, to do efficient composting you need large amounts of carbon rich material, I think five times as much as the volume of faeces is a pretty good estimate. Which is one of the reasons composting toilets do not actually work very well in some circumstances.

I'm not sure a composting system is the best for the situation you describe. Why don't you want to just have it as a dehydration toilet?

I was definitely talking about Urine Diverting composting toilet. For me in this moment, I don't have the resources or the equipment for making measurements of c:n ratio, so I depend on estimations. A few of you said that there's no need of adding water in a composting UDDT because the idea is to keep everythnig dry. That would be right if you're talking about dehydration toilets, but i'm making an analisis in the limitant factor of a composting UDDT. I read in a reference (that cpuldn't find again, sadly), that there's need of adding 4 to 5 times the weight of the faeces of carbon-rich materials for composting. I already have a few conclusions in how hard is to make this unit work, at low investing, with a training of the new user that can't last more than a afternoon. For not keeping my doubt, I started to make mass balances with the carbon, nitrogen,density, volume and moisture content in microsoft excel, mixing faeces with one additive at a time. My first criteria was to leave the C/N ratio a litle higher than 20. The result was HUGE VOLUMES OF RICH CARBON MATERIALS NEEDED, and reduced content of moisture, than can be equilibrated with water adding, reaching ~40% moisture if you add 200 cc of water after each defecation. This huge volumes made me believe that extra carbon from toilets paper can reduce the big amount of carbon-rich materiales needed, and I need the carbon content of toilet paper for making that. Or the other way, add that amoun of carbon-rich material, but instead of water, add the solid waste, that certainly has a lot of water (~80% sounds fine for me). It sounds crazy but the mass balance says that.I share you a few data in the input and the output, I think that maybe can be a mistake in the data.

Considering
-Faeces: 70% moisture, 150 [g] each defecation, c:n =8, %N=7%

I wrote the input, and the results of increasing the volume added until c:n its the minimal (~20)

Sawdust: 8% moisture, density 80[g/Lt],c:N 511, %N=11%.
-Results: 32% moisture, c:n 20 if 3 litres after each defecation is added.

Dry leaves: 10% moisture, density 70[g/Lt], c:n 54, %N=7%
-Results: 26% moisture,c:n 20 if 6 litres of leaves are added.

Thatch: 10% moisture, density 70 [g/Lt], c:n 80, %N=0,7%
-Results: 28% moisture, C:N 22 if 5 litres afeter each defecation.

Wood chips: 8% moisture, density 140[g/Lt], c:n 560, %N = 0,09%
-Results: 30% moisture, C:N 21 if 2 litres of chips area added.



I'm makins this work with a group of engineers here in Valparaíso, Chile for install units in rural areas. We already installed a few units that works, but definitely by dehydration and maybe a little composting (we used sawdust, crushed barks and ashes, in UDDT units, and a little size redution was observed). We are making a technical evaluation with the composting process, motivated by the 90% volume reduction reported by Clivus Multrum, the better sanitary results, and better fertilizer powers. But it's not practical having 90% of size reduction, if I have to put a bucket of more than a gallon of dry leaves after each defecation(only imagine doing that thing after poo, it's simply not comfortable). Maybe with an automatic system with a flush with crushed leaves afeter defecation or huge chambers for reaching thermofilic compost it's gonna work, but we have to make ir cheap.

Also you have to know that is is gonna be in rural areas, with old people, who haven't heard anything about ecosan systems in his life, and also, a high-society school boy (me) is gonna come and tell him how he has to poo? It has to be an easy task, and it doesn't get easier if I have to indicate the new users "you have to add this bucket of leaves after each defecation, and 200 cc of water, in this brand new toilet that separates you're urine (Diverting urine by the first time IT'S A SHOCK FOR THE USER),and also, you have to full this tank with leaves every week"

Not diverting urine it's not a choice, maybe it's gonna increase moisture, but with the high nitrogen content, it's gonna increase the carbon-rich materiales required (80% of nitrogen in sewers comes from urine).

Hope you speak spanish, we were on TV YEAAAAHHH: thank you susana partners for your interest in helping me with my research, i share a little note about us:

I'm definitely not pretending to be any kind of expert in the use of UDDTs, so I can only concur with Chris on that. In my view, a properly functioning composting system is always preferable to the processes going on in a UDDT - but I know others think differently.

I had some experience of co-composting faeces (actually it was pressed sludge) with paper waste and it didn't go well. I'd have to look up to see if there are studies of it, but I think the physical properties of the paper makes it less useful in a composting scenario than other potential materials.

As Chris and Elisabeth have indicated above, it is entirely possible that the original questioner is mistaking the processes inside a UDDT for composting.