Ralf, you are also conducting research at the Technical University of Hamburg-Harburg on the question of the extent to which supposedly problematic waste such as urine and feces could be used today to build humus. Do we produce the alternatives for artificial fertilizers in our own bodies every day??
Almost all of the nitrogen that humans metabolize is excreted as urine; for phosphorus, it's about half that amount. Other macronutrients for plants, such as potassium, sulfur, calcium or magnesium, are often scarce in soils, while they are found in varying amounts in human excrement. However, feces are not feces. A healthy person who eats a wholesome diet has the whole range of high quality substances in his feces, especially if he does not take pharmaceuticals. If we want to use feces, we should therefore take those of health-conscious people.
You are also thinking about how to alternatively disinfect and supply entire cities and their surrounding areas with wastewater. So, does the use of excrement require all inhabitants to find alternatives for their pharmaceutical consumption?
The change in consciousness that we are currently witnessing can very quickly lead to things that are normal for us today – such as taking pills – appearing absurd within a few years. We can already collect what is clean today. We are developing a flexible toilet system for urban and rural use.
At the moment we are working experimentally with simple camping toilets at our institute. We do not use the chemicals intended for this purpose, but rather the microbial mixture for lactic acid fermentation developed by Terra Preta pioneer Jurgen Reckin. You could also just use sauerkraut brine. With the right lactic acid-bacteria mixture, which we are currently researching, it is possible in principle to collect excrement odorlessly and hygienically in any home, even in the city. Therefore, we are developing a toilet suitable for everyday use, with which this will be possible. What still needs to be solved is transportation to the countryside, because there is usually not enough space for composting in the city.
It is always said that compost from human excrement should not be used to fertilize food crops.
You should wait about ten years before growing food on a fecal compost. Substances from feces and sewage go to plants, which feed on microorganisms, among other things. Our research and the literature say the same thing: The plant absorbs substances dissolved in water, as well as pathogenic germs that can concentrate in leaves, because the water evaporates and these substances accumulate.
Ten years sounds like a long time, but in fact it is not. After about two to three months of proper worm composting in the summer, this compost could be put into the soil, where it could first be used to plant wood for a firewood plantation, for example. Households produce much larger quantities of kitchen waste anyway; excrement accounts for only a third of waste, and with garden green cuttings, its share is even lower.
What is the legal situation in Germany regarding the operation of composting toilets??
The matter is double-edged: On the one hand, the waste ordinance is very progressive with the requirement for recycling. In the wastewater sector, these laws actually also apply, but are counteracted there by contradictory laws. It is mandatory to have a flush toilet, but at the same time no law forbids to put a Terra Preta toilet next to it. Therefore everything is possible. As long as the excrements are collected as recyclable materials, I am within the scope of the Closed Substance Cycle Waste Management Act and am therefore not liable to prosecution under wastewater laws. They only become wastewater when the will to dispose of them exists and they are introduced into a wastewater system. In some federal states, however, there is extremely restrictive legislation on wastewater.
Is the need for terra preta sanitation greater in other parts of the world?
Two billion people have only pits, and in many areas there are flush toilets but no wastewater treatment at all. Groundwater is thus contaminated to an unbelievable degree, millions of people die. Introducing composting toilets in such countries can be a lifesaver. But development will only move forward if we push these systems forward. My institute is one of the very few in the world that deals with the subject at all, because there is hardly any research funding for products whose export hardly promises any profit.
Soil improvement is extremely important here, too, and we'd better start now. The global external supply can collapse very quickly. If we ever have to live on relatively little land, every gram of humus is important.