Dear Robert,

I have been meaning to start a discussion on Terra Preta Sanitation (TPS), so maybe now is a good opportunity. Let me start by outing myself as a "TPS sceptic".
I find there is quite a bit of "hype" about TPS but very little hard and fast evidence that a "Terra Preta Toilet" is easy to use and well accepted. I assume that its direct counterpart would be a UDDT, thus a Terra Preta Toilet should be better than a UDDT (Ralf Otterpohl used to say the main advantage would be less odour but only if the lid is tightly closed).

One thing that annoys me a little bit is that the same "facts" about the "vast areas" with fertile terra preta soil in the Amazon area are repeated over and over again. Are people just copying from each other? Strangely, the same one or two photos of this type of soil in the Amazon is used time and time again in various papers... (and journalists just love it by the way: "ancient Indio knowledge is rediscovered to solve problems of today...")

There is an MSc thesis in the SuSanA library which includes information about the areas with terra preta soil, and it is actually only a small area that has that type of very fertile soil according to this research:

www.susana.org/lang-en/library?view=ccbktypeitem&type=2&id=796
de Souza Cannavan, F. (2007). Diversidade das comunidades bacterianas em solos de terra preta antropogenica da Amazonia Central e Oriental (in Portuguese) - Diversity of the bacterial communities in Anthropogenic Black Earth from the Central and Oriental Amazon. MSc thesis, Universidade de Sao Paulo, Escola Superior de Agricultura, Brazil.

It is in Portuguese but some additional information in English was provided by Cecilia Carvalho Rodrigues:

Regarding the size, she mentions it in the end of the first paragraph of page 16 (pdf, p.17): “Nevertheless in the same region, one can find one of the most fertile soil in the world, identified as Terra Preta Antrpogênica (TPA) or Terra Preta de Índio, representing a small parcel of Amazon soil, probably covering at least 0.1 to 0.3% (15,500 – 20,700 km2) of the forested area of Amazonia (SOMBROEK et al. 2003)”. This section of her literature review is quite interesting. Regarding the dimension of occurrence, in the first paragraph of page 17 she says: ‘This kind of soil occurs in isolated round spots with differing dimensions (FALESI et al., 1972). The spots typically occupy small areas, around 0.5 and 3 hectares (SMITH, 1980), with however, indications of sites at the Estacao Científica Ferreira Penna – National Forest of Caxiuma (PA), extending over 100 ha. Despite the vast amount of archaeological sites already known, there is not a mapping of all occurrences of the ADE in Amazon.

Regarding the depth, it is generally around 30 to 60 cm, being possible to reach up to 2m deep (SMITH, 1980).

In her abstract, she uses the term ‘Anthropogenic Black Earth’ (ADE) instead of Terra Preta.

Another question for me is: will the conference bring together those people that work on Terra Preta (without excreta) with those that work with Terra Preta Sanitation? I think that would be useful. The "terra preta compost" (without excreta) seems to be quite popular and maybe already a commercial success? See e.g. this website of a German manufacturer: terra-preta.de/ or palaterra.eu/. (although of course I can't tell if their product is a commercial success, only that their website looks very nice and professional).

I just can't see Terra Preta Sanitation work on a large scale (on a small scale with some enthousiasts it may work fine) - if we already have such difficulties with scaling up UDDTs, even though they are bound to be much easier to use than TPS-toilets where I have to add lactic acid bacteria/liquid, keep the lid completely closed etc.

I am looking forward to a debate or conversation with you and others on this topic.

Regards,
Elisabeth