General starting point: Liquid manure issue
Liquid manure is a controversial agricultural and economic term in the public eye, which has ultimately found its way into European legislation.
Until the commercial implementation of the Haber-Bosch process for the synthetic production of nitrogen (at the beginning of the 20th century), farm-produced manure such as liquid or solid manure was the most important source of nitrogen for fertilizing fields. Liquid manure had a positive reputation. However, due to the increasing industrialization of agriculture in the areas of animal husbandry and crop cultivation, this has changed.
O Due to the change in feed composition towards more concentrated protein feed, the proportion of NH³ in the slurry has increased (protein that is not digested breaks down into nitrogen components).
O Intensive livestock farming results in ever-increasing quantities of liquid manure being produced in ever-smaller areas and spread on limited land. The consequence, in conjunction with over-fertilization through synthetically produced and naturally occurring nitrogen, is nitrate pollution of the soil and groundwater . Liquid manure has been declared the primary culprit and thus negatively impacted.
O Because the manure from animals with poor rumen fermentation is rich in nitrogen, relatively low in carbon, and high in emissions, it tends to form a floating layer, foam layer, or gas layer on the surface. The portion of the manure beneath this layer then putrefies and produces many toxins. The significantly increased administration of medications, disinfectants from foot baths, and rinse water from milking machines also contribute to the manure becoming a partially toxic product . Left untreated, it is not good food for soil life.
Today, the picture is beginning to change. Liquid manure is increasingly seen as a cost-effective, environmentally friendly alternative to fertilizing with synthetic nitrogen. Its use aligns with the demands of sustainable agriculture .
In addition, new technologies have been developed that combine high-tech with and support nature-adapted agriculture. This transforms liquid manure into a highly effective product capable of binding nitrogen, along with other substances. and added products such as silicon and other trace elements, liquid manure becomes a complex fertilizer or additive at low production costs. Furthermore, the various components necessary for the soil can be applied together, and the price increase of nitrogen components due to higher energy prices can be at least partially offset.
It is gradually becoming accepted among experts that one can make a virtue out of necessity here:
Production of a high-quality fertilizer that significantly reduces NH³ emissions.
Processed slurry, with its high content of naturally converted and bound nutrients, lower NH3 content, and the microorganisms involved, closes the biocycle with the highest soil ecological effectiveness.
Furthermore, manure treatment improves its flowability, which is beneficial for all manure applications and in manure channels. Last but not least, it reduces odor during application. A significant advantage for the population, for farmers, and for the environment.
In general, the biological cycle must be considered in manure production. This includes "pre- and post-treatment" measures such as:
- Animal care with near-natural prebiotic substances and probiotic microorganisms to ensure animal health
- Stable hygiene using suitable means (e.g., fogging of ferments, conditioning of the bedding)
- Liquid manure processing with natural products under suitable storage conditions for a high-performance organic fertilizer
This results in healthy soil and healthy plants, bringing us back to the starting point of the cycle.
Current liquid manure situation in detail
Approximately 95% of ammonia (NH3) emissions in Germany originate from agriculture (German Environment Agency - UBA 2020). According to the NEC Directive (Directive on national emission ceilings for certain atmospheric pollutants), these emissions must be reduced by at least 29% in Germany by 2030 compared to 2005 (UBA 2020).
Especially regarding the handling of organic fertilizers, such as liquid manure, the Fertiliser Ordinance (DüV) prescribes stricter regulations to reduce ammonia emissions. Agricultural operations are now obligated to apply liquid manure with a significant content of available nitrogen or ammonium nitrogen to cultivated arable land only in strips or directly into the soil (DüV, dated 28 April 2020). Due to negative experiences with feed contamination and the high financial burden on farms, farmers have significant concerns about implementing the low-emission, strip-applied application requirement (IG gesunde Gülle 2019).
Furthermore, according to the German Federal Environment Agency (UBA, 2020), measures using near-surface application technology are insufficient to comply with the limit values. For example, the NEC Directive stipulates a maximum limit of 431 kilotons of ammonia emissions (from 2030 onwards) (Thünen Institute). The only approach currently recognized in the Fertiliser Ordinance (DüV) for reducing NH₃ emissions at the end of the process chain through near-surface application limits the potential for reduction. Previous studies suggest that utilising the cascade effect, for example through housing systems, adapted feeding, or treatment with additives, can lead to a significantly more effective reduction compared to near-surface application alone.
These reduction options, which take effect at the beginning of the process chain, are indeed explicitly mentioned in the Fertiliser Ordinance in paragraph 6 paragraph 3, but are not accepted as an alternative to near-surface application due to a lack of scientifically sound evidence regarding their effectiveness in reducing NH³ emissions (Müller and Aures 2020).
This state of knowledge led to the development of the measurement and testing procedure used here.
Implementation began in January 2019 with and through the IG gesunde Gülle (Healthy Manure Interest Group). In cooperation with the state laboratory in Kassel, under the direction of Dr. Harald Schaaf, the foundation for this measurement and testing procedure was laid. Further development of the method took place in a specially established laboratory in Hebertsfelden, which was provided by Ingrid Bauer from Hebertsfelden, who also spearheaded the development. The project was financed by private donations from farmers and other committed individuals, companies, and organizations. Jens Keim and Ingrid Bauer utilized extensive technical and professional support behind the scenes, which contributed significantly to the project's success.
A professional testing and measurement method was developed, consisting of the NH³ emission test vessel, a calibration fluid, and a protocol. The calibration fluid was developed through numerous individual tests using a trial-and-error approach.
The functionality and suitability of this testing and measuring method was confirmed by the DLG with test report 2012-0032 on behalf of the IG gesunde Gülle (Healthy Manure Interest Group).
The company Extox provided a specially developed "Red Case" for recording the measurement results. Measuring ammonia emissions from organic fertilizers in sample containers under defined framework and laboratory conditions can serve as a basis for investigating the effectiveness of various reduction measures at the farm level and lead to a results-oriented and verifiable reduction of ammonia emissions in agriculture. Furthermore, the development of a reference value enables comparability between measurement results. Recognition as a scientific method is ensured through the development of a standardized measurement and testing procedure.
The primary goal is to establish a scientifically recognized method, independent of measurement technology or compatible with almost any measurement technology, for the verifiable, repeatable and comparable determination of ammonia emissions (e.g. manure) in vessels under definable laboratory conditions. The methodology for measuring ammonia emissions is complex. The Bavarian State Research Center for Agriculture (LfL) and the Technical University of Munich (TU Munich) offered the "Healthy Manure Interest Group" (IG gesunde Gülle) the opportunity to organize an international review of the methodology, provided a detailed method description in accordance with the VERA protocol is submitted. (Müller and Aures 2020)
Overview of the simple and recognized "Red Suitcase" measuring and testing procedure:
- Calibratable measuring technology with defined tolerances
- Replicable emission test vessel for verifiable emission sampling
- defined air velocity
- repeatable and standardizable methodology with defined framework conditions,
- Factors and their parameters, as well as a precisely described procedure.
2. Investigation of the effect of mineral manure additives ( tribomechanically activated ) on the reduction of NH³ emissions
2.1 Hypothesis of the study
By “adding” manure additives based on a product mix of various clay minerals that have been tribomechanically activated*, NH³ emissions are significantly reduced.
*Tribomechanical activation (pulverization process):
Tribomechanical activation is a special micronization process in which the raw materials are not crushed but ground. The particles are accelerated to very high speeds by centrifugal forces. Through a technical redirection of the direction of motion, they collide with each other and thus grind themselves down. This eliminates abrasion (as in ball mills), the material acquires a high base energy, and retains its purity. This means that this process has no effect on the chemical composition of the raw material; on the contrary, the crystal lattices remain intact and are not disrupted. The electrostatic charge, particle surface area, and ion exchange capacity are optimized. The total surface area of the particles is significantly increased, thereby enhancing the reaction rate and efficiency of the physical and electrolytic processes.
2.2 Measurement method: “Ammonia emission potential with the red suitcase” according to the method of the IG-Gesunde Gülle (Healthy Manure Interest Group).
The measuring technology used, the "Red Suitcase," is a sample-aspirating system employing an electrochemical NH₃ sensor. This technology allows for real-time measurement of the ammonia concentration. Control and visualization are performed via a PC. Automatic documentation of the measurement, including report generation, is available in PDF format. The determined NH₃ value (ppm) is based on the average of 60 individual measurements taken during the last minute. In addition to the NH₃ measurement sensors, the temperature of the sample and the supply air (°C), as well as the volume flow rate (l/h), air pressure (hPa), and relative humidity (%) can be simultaneously recorded and electronically documented every second.
See the scientific work by Anna-Maria Bissinger, chapters 5.2-5.3.
"Measurement method for determining current ammonia emissions from various substrates based on scientifically sound and verifiable NH³ emission determination with permanent system calibration" II./3 Literature review and problem statement
At the end of the investigations, a so-called NH₃ emission protocol is generated . This protocol forms the basis of this measurement and testing procedure. It describes the precise, standardized procedure and includes all defined parameters and components. Factors such as spatial and environmental conditions, most of which have already been mentioned, are specified and defined therein. When using NH₃-Stable-Mobile, the underlined parameters are automatically recorded and documented. If other measurement techniques are used, the values must also be recorded by certified devices. The following list of parameters must be documented and adhered to:
- Room temperature
- Room humidity
- air pressure
- Measured volume flow
- pH value of the substance
- Type and designation of the measuring technology
- Empty measurement
- Initial calibration or calibration measurement before each measurement series
This documentation is an important component for demonstrating and verifying compliance with the defined parameters and ensuring the comparability of measurement results. The NH₃ emission protocol must be attached to each sample measurement result.
2.3 Experimental setup and execution of barrel tests with slurry additives
Basic requirement: Use of the "appropriate liquid manure":
- Homogenization by stirring before extraction
- untreated
- pH value greater than 7
- Initial value in ppm between 40 and 80 AEP (Ammonia Emission Potential)
- Temperature: kept constant at max. 12°C throughout the entire experiment
- No sunlight on the barrels, that distorts the results.
- Simultaneous measurement of other parameters such as ammonium, total nitrogen, C/N ratio, etc.
2.3.1 Different formulations
Formulations of purely mineral-based and tribomechanically activated slurry additives from the brands KALKMEISTER and STEINKRAFT were tested. The mixing ratios differed in each formulation.
Recipe No. 1
Recipe No. 2
Recipe No. 3
Recipe No. 4
The liquid manure was filled into 60-liter barrels. Each barrel contained 50 liters of liquid manure.
2.3.2 Experimental setup
O 1 control tank of untreated slurry and 1 slurry tank with the respective slurry additive
O The mixing ratio corresponded to 15 kg of slurry additive per m³ of slurry. Based on this ratio, the respective slurry additive was stirred into the barrels.
O The manure tanks were located in a place where the temperature remained constant (max. 12 degrees Celsius) and they were not exposed to any solar radiation.
Zero measurement: All existing untreated homogenized barrels were measured before treatment . This confirmed the uniformity of the existing slurries.
1st measurement: after 30 hours
2nd measurement: after 10 days
3rd measurement: after 14 days
All barrels were briefly stirred before each measurement and before the slurry was removed. Each measurement was performed twice to confirm the accuracy of the results. If a measurement deviated, it was repeated.
The mean value was used for the statistical analysis.
The temperature of the slurry during measurement was always 20 (+/- 0.5) degrees Celsius (heated in a microwave or water bath). The untreated barrel was included as a control measurement in every test.
3. Results
3.1. Tabular presentation of the results
3.2. Graphical representation of the results
3.3 Verbal description of the results
The current study has shown that all tested slurry additives achieve a high NH3 binding capacity. Two of the four formulations tested performed particularly well in the long-term trial (after 14 days), achieving NH3 binding rates of 33.63% to 36.91%. Reductions of >30% are generally considered exceptional. It should be noted that a decrease in the AEP (ammonium nitrate level) was observed at the same pH value. Furthermore, the slurry remained very homogeneous and exhibited high flowability throughout the entire investigation period. It should also be noted that the additives bind the organic nutrients in the slurry.
As found in previous studies, this study also confirms that the additives react relatively quickly. NH3 binding rates of 9.96% to 25.03% are observed after just 30 hours. However, the maximum NH3 binding is observed after 14 days.
To better contextualize the results presented, it should be noted that a reduction in the NH³ value of approximately...
O 20% = can be described as a good result
O 30% and more = an exceptional result
All mixtures reacted positively in the tests. Two mixtures in particular proved to be especially reactive and therefore effective in the long-term test with regard to NH3 binding:
O Recipe No. 1: KALKMEISTER N-Fix / STEINKRAFT Güllekraft N-Fix
O Recipe No. 2: STEINKRAFT Liquid Manure Power N-Fix Humin
For both formulations, significant NH3 reductions of up to >30% were observed in all study periods. The highest value was measured after approximately 14 days.
4. Conclusion
Here, manure additives were tested, all of which made a very good to exceptional contribution to reducing NH3 by fixing the gas released from the manure. This resulted in a reduction of NH3 emissions from manure application by up to 30% and beyond. The air pollutant is thus significantly reduced.
Two products stood out in the study:
- KALKMEISTER N-Fix / STEINKRAFT Güllekraft N-Fix
- STEINKRAFT Liquid Manure Power N-Fix Humin
The addition of mineral additives before applying the liquid manure offers further advantages for agriculture:
- The application of liquid manure is carried out in conjunction with the application of additional necessary nutrients and trace elements (= 1 operation).
- The odor pollution in the surrounding area is greatly reduced.
- Processed liquid manure contains fewer salts and is not corrosive to plants, which is particularly valuable when applied to grassland.
- Slurry sausages applied with trailing shoes are better utilized with processed slurry and thus cause less contamination in the feed.
- The improvement in feed for pasture farming, in terms of both quantity and quality of grass, is significant.
- Processed manure contains fewer putrefactive substances. Anything that rots and stinks is bad for humans and soil life.
- The additives are natural minerals that are available in sufficient quantities.
- By applying them to the field, they can even permanently return CO2 to the soil by increasing biomass (humus build-up).
5. Recommendation:
We can only recommend the use of the tested additives with regard to their NH³ binding potential, but also because of their positive effect in the soil.
We recommend that all storage facilities/treatment companies add the additive approximately 14 days before application and stir the slurry before application, as otherwise the anaerobic processes could re-establish themselves, depending on how strong or how advanced the initial putrefaction of the slurry is.
Previous studies have shown that the ppm value of slurry can be reduced in advance through feeding practices and stable hygiene (bedding). This makes it more stable and reduces the likelihood of putrefaction. We also generally recommend "moving" the slurry to naturally counteract putrefaction pressure.
The mineral-based and tribomechanically activated manure additives tested in this study simultaneously achieve the following:
§ The liming of the soils is supported by the primarily lime-based slurry additive (KALKMEISTER N-Fix / STEINKRAFT Güllekraft N-fix).
§ The slurry additive, primarily based on the zeolite and leonardite mixture (STEINKRAFT Güllekraft N-Fix Humin), has made a valuable contribution to the urgently needed humus build-up.
§ The tested additives from the brands KALKMEISTER and STEINKRAFT also activate the microbiology and humus formation in the soil, thus making a valuable contribution to soil revitalization.
The dosage of approximately 15kg to max. 20kg per m³ of slurry makes this powerful and natural method of slurry treatment attractive in terms of price and has the potential to more than question the dogma of near-surface application.
In summary, this study provides us with more than initial indications of the positive effect of mineralogical additives on NH³ binding in slurry, and their use is already worthwhile today.
This has encouraged us to document the manure additives in other areas of application, such as in biogas plants.
Ingrid Bauer Measurement Services: www.ingridbauer.de
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