In current debates surrounding the scarcity of natural gas, its economization, and supply priorities, mention is often made of artificial fertilizers — without which the world’s population seemingly cannot be fed.
The production of artificial fertilizer requires ammonium, a material that cannot be produced without natural gas. According to the representatives of Germany’s largest chemical companies, this is why their ammonia production is essential and should therefore be given preferential treatment in the allocation of gas supplies.
Ariane Krause is the project coordinator of the zirkulierBAR research project at the Leibniz Institute for Vegetable and Ornamental Crops (IGZ) e.V. and advocates for the recognition of recycled fertilizers from dry toilets. For her, the call “from faeces to fertilizer” is also symbolic of how people deal with resources — because nature knows no waste.
This article first appeared in maldekstra #16. Translated by Sonja Hornung and Marty Hiatt for Gegensatz Translation Collective.
This argument ignores the fact that artificial fertilizer — as well as the industrialized agriculture that depends on it — also massively damages other vitally important natural resources. According to the German Federal Environmental Agency, “the process of artificially fixing nitrogen is the original cause of today’s nitrogen surplus” throughout the planet’s ecosystems, affecting in particular rivers, oceans, and lakes.
The production of conventional nitrogen fertilizers also requires not only natural gas, but also a great deal of energy. In 2015, a study calculated that the production of ammonia-based fertilizers accounted for approximately 2 percent of the world’s energy use between 1900 and 2014. This huge demand for energy was primarily fulfilled by fossil fuels, leading to the release of CO2 into the atmosphere.
That said, the use of artificial fertilizer — or more precisely, synthetic mineral fertilizer — can already be significantly reduced today by integrating human waste into the circular economy without any fundamental restructuring of nutrition or agriculture. This is because human waste contains nutrients that can be recycled as fertilizer to encourage plant growth. If correctly prepared and quality-controlled, up to 25 percent of conventional synthetic mineral fertilizers in Germany could be replaced. Combined with an agricultural transition involving the reduction of livestock farming and plant cultivation for fodder, even less artificial fertilizer would be necessary.
Wasteful Waste Disposal
Approximately 70 years ago, rural areas in Germany were still fertilized using human waste. Since then, flush toilets, water-borne sewage systems, and wastewater treatment plants have been established even in the remotest regions of Germany and Europe, leading to important improvements to hygiene.
However, it has also been shown that a high proportion of nutrients in our wastewater comes from human sewage. Urine, for example, comprises less than 1 percent of the entire wastewater volume, but contributes 70–80 percent of the nitrogen and 45–60 percent of the phosphate found in wastewater. Despite highly technically equipped wastewater treatment, to date, these nutrients are rarely recycled from wastewater, instead leaking into our waterways. There, they contribute to the overabundance of nutrients, leading to eutrophication and putting ecosystem diversity at risk.
Germany-wide, toilet flushing uses over 1 billion cubic metres of fresh water per year. This is more than the volume of the Müritz, the country’s largest inland lake. This is a massive amount of water that must be questioned in light of the heat wave we experienced in the summer of 2022, and are likely to experience again in the future.
After flushing, the toilet’s contents are emptied into the sewage system and flow into the wastewater treatment plant. Here, the nutrients found in human waste are not recovered, but are separated from the wastewater in an energy-intensive procedure, releasing a lot of greenhouse gases in the process.
During the wastewater’s treatment, larger solids sink to the bottom, forming sewage sludge. In order to treat the bacteria and trace substances it contains, this sludge is incinerated. However, burning this substance, which is almost 95 percent water and must first be dried, requires a great deal of energy. This process should be critically examined with regard to its sustainability. Furthermore, leftover toxic substances are either released into the air during incineration, or require landfill disposal.
Phosphorus, which alongside ammonium constitutes an important base material for artificial fertilizer, has become scarce worldwide. For this reason, as of 2018, its extraction from sewage sludge is required by law. Nitrogen, however, is still not recycled in sewage plants, but is simply removed. 10–16 percent of municipal energy demand in Germany is required for the treatment phases of nitrification and denitrification alone, meaning the processes through which nitrogen is extracted from waste and returned into the atmosphere. Despite this, according to calculations by the Federal Environmental Agency, 22 percent of the total nitrogen and 33 percent of total phosphate levels in surface waters in 2016 came from municipal wastewater treatment plants and urban drainage systems.
Increasingly, effluents from the treated wastewater are also a key source of the pharmaceutical residues, such as antibiotics, found in our waterways. Studies from the German Federal Environmental Agency have already detected multi-resistant bacteria in surface waters as a result. The removal of these traces is technically possible through what is known as the “fourth purification stage”, which deploys activated carbon as a filter material. However, according to the Federal Environment Agency’s assessment, upgrading existing wastewater treatment plants to include this stage is, in most cases, not economical in light of the large volumes of wastewater that would require treatment.
Another Fertilizer Is Possible
Technical systems engineered to separate water and nutrient cycles could be effectively and efficiently used to prevent leakage and facilitate recycling. A separate and more water-efficient collection of human faeces would enable the focused treatment of undiluted substances, with the aim of killing off pathogens, removing contaminants, and safely recycling nutrients. In this way, medication residues, for example, can be effectively removed from recirculating systems with modern filter technologies — a process more easily implemented if only a small fraction of wastewater needs to be treated.
Unlike in conventional wastewater treatment plants, here, the spread of nutrients, pollutants, and trace substances into soil and waterways can be prevented. Over the last ten years, an active network has been developing worldwide that aims to further the development of sustainable sanitation systems, goaded both by scientific research and private interests. Their goal is not to do away with centralized sewage treatment plants and associated sanitary systems completely. Rather, the idea is to further develop wastewater systems and prepare them for the future wherever it is ecologically, economically, and technically possible and/or necessary. New, decentralized, and water-efficient recycling systems would then complement centralized and linear infrastructure on an individual and flexible basis.
Today, many exciting examples demonstrating how things can be done differently already exist.
In Sweden, for example, the production of a powdery solid fertilizer made out of urine has been tested out as part of the EU research project REWAISE. This process has already been applied by Dutch water authorities, while a Swiss company has produced the first legal liquid fertilizer from separately collected urine. The German Aerospace Centre has also used the C.R.O.P.® biofilter to develop a process for producing a multi-nutrient liquid fertilizer using treated urine. All these processes meet health and safety requirements, and even remove drug residues. They could also be used to treat animal manure or fermentation residues from biogas units.
In Germany, there are only two companies — Finizio in Eberswalde and Goldeimer in Hamburg — that are investigating the production of humus fertilizer from the contents of dry toilets. If this product were to circulate, it would be categorized as an organic NPK fertilizer which would additionally be considered beneficial to the climate due to its positive effect on building soil humus.
The inhibition of this development is due not to a lack of innovation or technological development, but to an unclear legal situation. Unlike with other source materials such as wastewater sludge, liquid animal manure, or bio-waste, which are already used as fertilizers, there is no regulation for human excretions collected separately from wastewater systems. The Circular Economy Waste Management Act (KrWG) comes closest to addressing the matter. According to this law, material recovery (recycling) has priority over energy recovery. It would therefore be logical to assign faecal matter — if collected separately from wastewater — to waste law, instead of wastewater law, as various legal assessments have already suggested.
Additionally, a clear legal framework is still lacking, including an updated fertilizer regulation that allows the use of quality-controlled recycled fertilizer from human waste. The foundation of German fertilizer law is a conclusive “approved list” that names the substances from which fertilizer may be produced. Faeces and urine are not yet listed, which would be a precondition for their use — particularly because these substances are also not included in the EU Fertilizer Products Regulation.
In May 2020, the German parliament accepted the coalition’s motion to “sustainably ensure water provision and sanitation for all,” which calls, among other things, for “ensuring the comprehensive involvement of agriculture as one of the main actors for an intact circular economy within the framework of international water governance”. Furthermore, the motion calls for “advocating for sanitation to be understood as a business sector and working to ensure that human waste is used as a resource, in accordance with the principle of circular economy, through productive sanitation systems”.
As the war in Ukraine has painfully shown, it is necessary to drastically reduce the use of gas, providing additional motivation for change in this context. Instead of following short-sighted logics of practical constraint that favour environmentally harmful artificial fertilizers, we need to accelerate a turnaround in sanitary and food production systems.