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In the first part of this article, we discussed Europe’s dual dependence on mineral fertilizers and natural gas—a situation exacerbated by the closure of the Strait of Hormuz—and wondered whether livestock manure could help strengthen the EU’s energy and fertilizer sovereignty. To answer this question, we spoke with Xavier Flotats, Ph.D. in industrial engineering from the Polytechnic University of Catalonia (UPC) and professor emeritus of environmental engineering, with more than 40 years of experience in anaerobic digestion and biogas production from livestock manure.
The potential lies in fertilization efficiency
According to Flotats, based on Eurostat data, livestock manure in the EU contains approximately 8.5–9 million metric tons of nitrogen annually—a considerable amount, but insufficient on its own to replace mineral fertilizer. “If we wanted to replace imported fertilizer units, we’d have to double livestock production, which doesn’t make sense,” he warns. The room for improvement lies elsewhere: in efficiency.
Only 50-60% of the nitrogen in manure is utilized, with losses of up to 40-50% in the form of volatilized ammonia.
With phosphorus, the approach is different: since it is present in greater quantities than crops need, the solution is to separate and store it, which would make it possible to reduce a significant portion of imports.
The issue, therefore, is not just how much nitrogen or phosphorus the manure contains, but how much of it we are actually able to deliver to the crops.
The first step begins below the slats
If we want to use manure as a raw material, the first change must take place even before we start talking about treatment plants. “The first thing is not to waste the resource we have,” insists Flotats.
Nitrogen begins to be lost in the form of ammonia right in the barns. Therefore, one of the key measures is to remove manure as frequently as possible, before the urea hydrolyzes and ammonia emissions increase. Preventing ammonia emissions is not just an environmental measure: we are also preventing the loss of a fertilizer that we would later have to import—a fertilizer that is, moreover, produced using natural gas.
Once out of the barns, the same principles must be followed during storage and application: covered storage areas, minimizing losses, and fertilization techniques that allow the application to be tailored to the crop’s actual needs.
A relatively simple solid-liquid separation, for example, allows the liquid fraction to be used via fertigation during plant growth, when the crop requires nutrients, while the solid fraction can be used to provide organic matter and phosphorus. We don’t always need to start with complex technologies. Part of the potential lies simply in better management.
What about biogas?
Here, Flotats introduces another important point: biogas alone does not solve the nutrient problem.
Anaerobic digestion produces methane and mineralizes some of the nutrients. Much of the organic nitrogen is converted into ammonia forms that are more readily available to plants, facilitating their subsequent agronomic use, but also increasing the risk of ammonia losses if the digestate is not managed properly.
Biogas, however, plays a key role in the overall system:
- It allows for the recovery of renewable energy that might otherwise be lost in the form of emissions.
- It generates revenue that can help finance the investments needed to improve manure management.
But there is one condition: the manure must reach the digester while it is still fresh. Storing manure for months beneath the animals means losing some of the methane and ammonia we intend to recover. That is why Flotats closely links biogas production to the redesign of barns and frequent emptying.
“If we can’t empty it frequently, let’s forget about the gas,” he sums up.
The livestock producer must be part of the business
In areas with high livestock density, another problem arises: nutrients are not necessarily produced where crops need them, and transporting large volumes of slurry—which has a relatively low nutrient content—is expensive and inefficient. As Flotats illustrates, to transport about 60 kg of nitrogen contained in slurry, we may have to move approximately 10 metric tons of the product, whereas that same amount of nitrogen concentrated as mineral fertilizer would fit practically in the trunk of a car.
This is where technologies for the separation, concentration, and recovery of nutrients come into play, as do collective biogas and treatment plants.
For Flotats, a collective plant should not be limited to producing biomethane. It should become a tool for land management, incorporating specialists capable of developing and overseeing fertilization plans, using digital tools, deciding where and when to apply nutrients, and measuring their efficiency. And there is another requirement: livestock farmers must be involved in the business model. The revenue generated from biomethane should help finance the necessary modifications to farms to quickly remove manure, reduce emissions, improve animal welfare, and increase the fertilizer value of the manure. The model, Flotats warns, should not simply consist of a third party buying the manure, extracting its value, and reaping the profits. A biogas plant should improve the region’s environmental indicators: reducing ammonia and greenhouse gas emissions, improving fertilization, and lowering the risk of nitrate pollution.
RENURE: An opportunity that also demands caution
Recent developments in European regulations regarding RENURE (REcovered Nitrogen from manURE) open up the possibility of recovering nitrogen from manure and transforming it into products with properties that facilitate the replacement of mineral fertilizers. For Flotats, this represents an opportunity, but it also calls for caution.
The ease of using recovered nitrogen products should not simply mean applying more nitrogen per hectare. The goal must remain to increase efficiency: ensuring that as much of the applied nitrogen as possible actually reaches the crop rather than ending up in the atmosphere or in waterways.
RENURE, therefore, should not be viewed as a means of increasing the nutrient load in areas that are already oversaturated, but rather as a tool for transforming, concentrating, transporting, and making better use of those nutrients.
From waste to resource... though it always was one
Geopolitical tensions may be accelerating a shift in perception, but Flotats points out that manure hasn’t suddenly become a resource. It has always been one. For centuries, livestock farming and agriculture were closely linked, and nutrients from animals were returned to the soil. The specialization and territorial concentration of livestock production largely disrupted that balance. Restoring it today requires technology, logistics, investment, and knowledge.
Europe is not going to replace all mineral fertilizer or all natural gas with livestock manure. Nor would it make sense to increase the livestock population to achieve that. The opportunity lies in making better use of what we already produce. “Don’t lose ammonia, don’t lose methane, don’t lose phosphorus,” Flotats summarizes.
Perhaps that is the main answer to the question with which we began these two articles. Manure alone will not solve Europe’s energy and fertilizer dependence, but it can become part of a much broader strategy for self-sufficiency. To achieve this, we must stop viewing its management solely as a solution to an environmental problem and start seeing it also as the management of a strategic raw material.
Because every kilogram of nitrogen we manage to conserve and use efficiently is a kilogram we don't need to import. And every cubic meter of methane we recover is energy we don't have to source from elsewhere.
