General starting point of the manure issue
Manure is a controversial agricultural and economic term in the public eye, which has ultimately found its way into European legislation.
Farm-grown manure, such as liquid manure or dung, was the most important source of nitrogen for fertilizing fields until the commercial implementation of the Haber-Bosch process for synthetic nitrogen production (early 20th century). Liquid manure had a positive reputation. Due to the advancing industrialization of agriculture in the areas of animal husbandry and cultivation, a change has occurred:
O Due to the change in feed composition towards more concentrated protein feed, the proportion of NH³ in the manure has increased (protein that is not digested decomposes into nitrogen components).
O Due to factory farming, ever-increasing amounts of manure are produced in ever-smaller spaces and are spread on limited areas. The result, combined with over-fertilization with synthetic and natural nitrogen, is nitrate pollution of the soil and groundwater . Manure has been declared the primary culprit, thus giving it negative connotations.
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 below this layer then decomposes and produces numerous toxins. The sharp increase in the use of medications, disinfectants from footbaths, or rinse water from milking machines also causes the manure to become a partially toxic product . If untreated, it is not a good food for soil life.
Today, the picture is beginning to change. Manure is increasingly seen as an inexpensive, environmentally friendly alternative to synthetic nitrogen fertilization. Its use meets the demands of sustainable agriculture .
In addition, new technologies have been developed that combine high-tech with and support agriculture adapted to nature. This makes manure a highly effective product that can bind nitrogen. Together with other substances and added products such as silicon and other trace elements, the manure becomes a complex fertilizer or additive with low production costs. Furthermore, the various components necessary for the soil can be applied together, and the price increase for nitrogen components due to higher energy prices can be at least partially offset.
It is gradually becoming clear to experts that one can make a virtue out of necessity:
Production of a high-quality fertilizer in which NH³ emissions can be significantly reduced.
Treated manure, with its high content of naturally converted and bound nutrients, its lower NH³ content and the microorganisms involved, closes the biological cycle with the highest soil ecological effectiveness.
Slurry treatment also improves the flowability of the slurry, which is beneficial for all slurry applications and in slurry channels. Last but not least, it reduces odor during application. A major benefit for the population, farmers, and the environment.
In general, the biological cycle must be considered in manure production. "Pre- and post-treatment" through:
- Animal supply with natural prebiotic substances and probiotic microorganisms to ensure animal health
- Stable hygiene with suitable means (e.g. nebulisation of ferments, conditioning of bedding)
- Manure processing with natural products under suitable storage conditions for a high-performance organic fertilizer
This results in healthy soil and healthy plants, which brings us back to the starting point of the cycle.
Current manure situation in detail
Around 95% of ammonia emissions (NH³ emissions) in Germany come from agriculture (Federal Environment Agency - UBA 2020). According to the NEC Directive (Directive on National Emission Ceilings for Certain Air Pollutants), these emissions must be reduced by at least 29% in Germany by 2030 compared to 2005 levels (UBA 2020).
The German Fertilizer Ordinance (DüV) stipulates stricter regulations to reduce ammonia emissions, particularly with regard to the use of organic fertilizers such as liquid manure. Agricultural holdings are required to apply liquid manure with a significant content of available nitrogen or ammonium nitrogen only in strips on the soil in the case of cultivated arable land or to apply it directly into the soil (DüV, dated April 28, 2020). Due to negative experiences with feed contamination and the high financial burden on the farm, farmers have serious concerns about implementing the near-ground and strip-application requirement (IG gesunde Gülle 2019).
In addition, according to the UBA (2020), the measures for ground-level application technology are insufficient to reduce emissions below the limit values. According to the NEC guideline, an upper limit of 431 kilotons of ammonia emissions (from 2030) must be observed (Thünen Institute). The only approach recognized to date in the DüV for reducing NH³ emissions at the end of the process chain through ground-level application limits the reduction possibilities. Previous studies suggest that utilizing the cascade effect, for example, through the husbandry system, adapted feeding, or treatment with additives, can lead to a significantly more effective reduction compared to ground-level application alone.
Although these reduction options, which are effective at the beginning of the process chain, are explicitly mentioned in paragraph 6, paragraph 3 of the DüV, they are not accepted as an alternative to near-ground 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 method used here.
Implementation began in January 2019 with and through the IG gesunde Gülle (Healthy Manure Association). The foundation for this measurement and testing method was laid in collaboration with the state laboratory in Kassel under the direction of Dr. Harald Schaaf. Further development of the method took place in a specially equipped laboratory in Hebertsfelden, which Ingrid Bauer from Hebertsfelden made available and drove the development forward. The project was financed through 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 led to the success of the entire project.
A professional test measurement method was developed, consisting of an NH³ emission test vessel, a calibration fluid, and a protocol. The calibration fluid was developed based on numerous individual tests using the trial-and-error method.
The functionality and suitability of this testing and measuring method was confirmed by the DLG on behalf of the IG gesunde Gülle with the test report 2012-0032.
The company Extox provided a specially developed "red suitcase" for recording the measurement results. Measuring ammonia emissions from organic manure in sample containers under defined framework and laboratory conditions can serve as a basis for investigating the effectiveness of various reduction measures at the individual farm level and lead to a result-oriented and verifiable reduction of ammonia emissions in agriculture. Furthermore, the development of a reference value enables comparability between the measurement results. Recognition as a scientific method is ensured by the development of a standardizable measurement and testing procedure.
The primary objective is to establish a scientifically recognized method that is independent of measurement technology or compatible with almost any measurement technology for the verifiable, repeatable and comparable determination of ammonia emissions (e.g. liquid manure) in containers under definable laboratory conditions. The methodology for measuring ammonia emissions is complex. The LfL and the Technical University of Munich have offered the IG Gesundes Gülle the opportunity to organize an international review of the methodology upon submission of a detailed method description in accordance with the VERA protocol. (Müller and Aures 2020)
Description of the simple and recognized measuring and testing method “Red Suitcase” at a glance:
- Calibratable measuring technology with defined tolerances
- replicable emission test vessel for verifiable sampling of emissions
- defined air speed
- 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 “mixing” 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 ground rather than crushed. The particles are accelerated to a very high degree by centrifugal forces. By technically redirecting their direction of motion, they collide with each other and thus crush themselves. This eliminates abrasion (as occurs with ball mills), imparting high basic energy to the material and maintaining its purity. This process has no effect on the chemical composition of the raw material; on the contrary, the crystal lattices remain intact and are not broken down. The electrostatic charge, the particle surface, and the ion exchange capacity are optimized. The total surface area of the particles is greatly increased, thus increasing the reaction rate and capacity 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
The measurement technology used, the "Red Case," is a sample-aspirating system using an electrochemical NH³ sensor. This technology allows ammonia concentration to be measured in real time. Control and visualization are handled via PC. Automatic measurement documentation and report generation are also available, including in PDF format. The determined NH³ measurement value (ppm) is based on the average of the 60 individual measurements taken during the last minute. In addition to the sensors for NH³ measurement, the temperature of the sample and the supply air (°C), as well as the volume flow (l/h), air pressure (hPa), and relative humidity (%) can be simultaneously recorded and electronically documented every second.
See 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 research and problem definition
At the end of the tests, a so-called NH³ emissions report is obtained . The NH³ emissions report 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 general conditions, most of which have already been mentioned, are specified and defined there. 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 using certified devices. The following excerpt of the 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 series of measurements
This documentation is an important component for proving and verifying compliance with the defined parameters and ensuring the comparability of the measurement results. The NH³ emission report must be attached to each sample measurement result.
2.3 Experimental setup and implementation of barrel tests with slurry additives
Basic requirement: Use of the “right manure”:
- Homogenization by stirring before removal
- untreated
- pH value greater than 7
- Initial value in ppm between 40 and 80 AEP (ammonia emission potential)
- Temperature: constant at max. 12°C throughout the entire experiment
- no sunlight on the barrels, this distorts the results
- Simultaneous measurement of other parameters such as ammonium, total nitrogen, C/N ratio, etc.
2.3.1 Different recipes
Formulations of purely mineral-based and tribomechanically activated manure additives from the KALKMEISTER and STEINKRAFT brands were tested. The mixing ratios varied in each formulation.
Recipe No. 1
Recipe No. 2
Recipe No. 3
Recipe No. 4
The manure was filled into 60-liter barrels. 50 liters of manure were poured into each barrel.
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 manure additive per m³ of manure. Based on this, the respective manure additive was stirred into the tanks.
O The slurry tanks were located in a place where the temperature was always constant (max. 12 degrees Celsius) and they were not exposed to solar radiation.
Zero measurement: All untreated homogenized tanks were measured before treatment . This confirmed the uniformity of the manures present.
1st measurement: after 30 hours
2. Measurement: after 10 days
3. 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, a repeat measurement was performed.
The mean value was used for the statistical evaluation.
The temperature of the slurry during the measurements was always 20 (+/-0.5) degrees Celsius (heated in a microwave or water bath). The untreated barrel was included as a control measurement for each measurement.
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 showed that all tested manure additives achieved high NH³ binding rates. 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 is noteworthy that a reduction in the AEP was observed at the same pH value. Furthermore, the manure was very homogeneous and flowable throughout the study period. It's also worth mentioning that the additives also bind the manure's organic nutrients.
As found in previous studies, this study also confirms that the additives react relatively quickly. After just 30 hours, NH³ binding rates of 9.96% to 25.03% were recorded. However, the maximum NH³ binding rate was observed after 14 days.
In order to better classify the results presented, it should be noted that a reduction in the NH³ value of approx.
O 20% = can be described as a good result
O 30% and more = an exceptional result
All mixtures responded positively in the tests. Two mixtures, in particular, proved particularly reactive and therefore effective in long-term testing with regard to NH³ bonding:
O Recipe No. 1: KALKMEISTER N-Fix / STEINKRAFT Güllekraft N-Fix
O Recipe No. 2: STEINKRAFT Güllekraft N-Fix Humin
For both formulations, significant NH³ reductions of up to >30% were observed during all study periods. The highest value was measured after approximately 14 days.
4. Conclusion
Manure additives were tested here, all of which made a very good to exceptional contribution to reducing NH³ by fixing the gases released from the manure. This resulted in a reduction of NH³ emissions caused by manure application by up to 30% and more. This significantly reduces the air pollutant.
Two products were particularly convincing in the study:
- KALKMEISTER N-Fix / STEINKRAFT Güllekraft N-Fix
- STEINKRAFT Güllekraft N-Fix Humin
The addition of mineral additives before applying the liquid manure has further advantages for agriculture:
- The application of manure is carried out with the application of additional necessary nutrients and trace elements (= 1 operation).
- The odor pollution in the environment is greatly reduced
- Treated manure contains fewer salts and is not corrosive to plants, which is particularly valuable when applied to grassland.
- Slurry sausages on trailing shoes are better converted with treated slurry and thus cause less contamination in the feed.
- The forage improvement for pasture-fed animals in terms of grass quantity and quality is significant.
- Treated manure contains fewer putrefactive substances. Anything that rots and smells bad for humans and soil life.
- The additives are natural minerals that are available in sufficient quantities.
- When applied to the field, they can even permanently return CO2 to the soil by increasing biomass (humus buildup).
5. Recommendation:
We can only recommend the use of the tested additives in view of their NH³ binding potential, but also due to their positive effect on the soil.
We recommend that all repositories/treatment companies add the additive approximately 14 days before spreading and stir the slurry before spreading, as otherwise the anaerobic processes could re-establish themselves, depending on how severe or how advanced the initial putrefaction of the slurry is.
From previous studies, we know that the ppm level of manure can be reduced in advance through feeding and stable hygiene (bedding). This makes the manure more stable and reduces the chance of rotting processes taking hold. We also generally recommend "moving" the manure to counteract the rotting pressure naturally.
The mineral-based and tribomechanically activated manure additives tested in this study simultaneously:
§ The primarily lime-based slurry additive (KALKMEISTER N-Fix / STEINKRAFT Güllekraft N-fix) supports the liming of the soil
§ 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 of the brands KALKMEISTER and STEINKRAFT also ensure the activation of microbiology and humus formation in the soil and thus make a valuable contribution to the revitalization of the soil
The dosage of approximately 15 kg to a maximum of 20 kg per m³ of slurry makes this powerful and natural variant of slurry processing attractive in terms of price and has the potential to more than question the dogma of applying the slurry close to the ground.
In summary, this study provides more than initial evidence of the positive effect of mineralogical additives on NH³ binding in liquid manure and their use already makes sense today.
This encouraged us to document manure additives in other areas of impact, such as biogas plants.
Ingrid Bauer Measurement Services: www.ingridbauer.de
