GasAbate additive + Compli360 dosing system for slurry tanks containing pig slurry

Description and technical details

The automatic dosing system containing the active ingredient GasAbate + Compli360, manufactured by GlasPort Bio Ltd., is suitable for use in open slurry tanks with the aim of minimising emissions from stored slurry during the storage period. Table 1 sets out the key product characteristics.

The dosing system consists of a storage container (IBC) containing the liquid active ingredient, a dosing pump – the operating time of which can be recorded electronically – and several stainless-steel lances. 

During installation, the lances are fitted into the slurry tank and permanently secured. The ends of the lances are installed in such a way that any escaping GasAbate + Compli360 can rise and take effect as evenly as possible within the slurry tank. Safety regulations must be observed during use and installation. The information in the safety data sheet must be followed. Personal protective equipment (PPE) must be worn.

Warranty

The manufacturer offers a warranty of 1 year, subject to the product being used correctly.

Table 1: Product characteristics for the treatment of pig slurry (manufacturer’s specifications)

The test is based on the DLG test framework for external slurry storage facilities, which was drawn up in collaboration with the Technical Committee for process-integrated mitigation measures. Large parts of the test framework are identical to the ‘VERA test protocol for covers and other emission-reducing technologies to reduce gaseous emissions from farm manure storage facilities, Version 3:2018-07’.

The test involves measurements to determine emission reductions on a pilot scale. Several identical plastic containers were used for this purpose, which were operated in a case-control mode. The purpose of this arrangement is to compare the emissions from a container holding untreated farm manure (control) with those from a container holding treated farm manure (case). The reduction is calculated from the difference.

Key process-related parameters (e.g. slurry temperature, ambient climate data and dry matter content or slurry composition) were recorded regularly and taken into account in the analysis.

Four identical tanks were available at the test site for the trial. Two tanks containing homogenised pig slurry were tested using a case-control design. For strategic reasons, the applicant decided to carry out duplicate determinations, although this is not strictly required under the DLG test framework. For this reason, all four available tanks were used for the measurements. An overview of the experimental design is shown in Table 3. Table 4 sets out the characteristics of the tanks. All tanks can be climate-controlled and are not exposed to direct sunlight. A fan in the outlet opening of each container ensures ventilation of the slurry surface, with the exhaust air being separated from the supply air as far as possible via a duct. The air velocity across the slurry surface was set at 0.1 to 0.3 m/s and was continuously recorded and stored.

During the test, care is taken to ensure that both the manufacturer’s specific requirements regarding the addition of the active substance (e.g. TM content) and standard industry requirements (e.g. agitators) are taken into account. The slurry was sourced from nearby livestock farms, agitated and distributed into the test containers 24 hours before measurements began.

The tests measured ammonia (NH₃), methane (CH₄) and nitrous oxide (N₂O). Odour samples were also taken from all containers in order to determine technical efficiency. 

Table 3: Experimental setup for determining emission reductions in pig slurry

Tests were carried out on a pilot scale using several slurry tanks. The test results are based on a comparison between treated and untreated slurry, with the tanks being filled with identical slurry in each case. The results are summarised below.

The test under warm ambient conditions (summer) took place in June and August 2024. The measurements under cooler ambient conditions (autumn) took place in October and November 2024. The composition of the slurry, with ranges of variation across all test containers, is shown in Table 5. The temperature ranges in the test containers used are shown in Table 6.

During the summer measurement period, the average outdoor temperature was 17.0°C and the average relative humidity was 80.4 %. In autumn, the average temperature was 6.9°C and the average relative humidity was 90.3 %.

During the test, foaming occurred in some of the test containers. This mainly occurs during the dosing process and can be attributed to the shape of the containers. This phenomenon tends to occur more frequently in containers with a small diameter-to-height ratio.

Table 5: Composition of pig slurry before and after the series of tests

Table 6: Temperature and humidity in all test containers

[1] Sensor temporarily out of action

Odour

The average odour-causing substance mass flows generated by the untreated slurry tanks (control group) were 237,270 GE/h in summer and 225,558 GE/h in autumn. Following treatment with the additive, values of 65,868 GE/h (summer) and 30,801 GE/h (autumn) were achieved. This represented a reduction of 72.2 % in summer and 86.3 % in autumn. On average over the year, emissions were reduced by 79.3 %. The results are shown in Table 7.

Table 7: Results of the olfactometric odour measurement

Ammonia

During the study, elevated ammonia emissions were observed in some of the treated slurry tanks, and the difference in the fall measurement was statistically significant. However, due to uncertainties in determining the dry matter content, the observed effects should be interpreted with caution. A NH3-reducing effect could not be demonstrated in this study. A supplementary analysis of the greenhouse gas impact in CO2 equivalents shows that the indirect climate impact of the increased NH3 emissions is of minor significance compared to the significantly reduced CH4 emissions. The overall positive climate impact of the CH4 reduction thus remains largely intact. The certification is limited to the reduction of methane and odour.

Methane

The results of the methane measurements were consistently good. In summer, emissions were reduced by 79.8 %, in autumn, the figure was 71.6 %, making a combined total of 75.7 %. The results are shown in Table 8.

Nitrous oxide

No significant reduction in nitrous oxide was detected over the entire duration of the test. The reduction in nitrous oxide following the addition of GasAbate + Compli360 was barely measurable and cannot be statistically substantiated. However, nitrous oxide concentrations in all slurry tanks remained at a very low level. An increase in nitrous oxide emissions resulting from the addition of Gas­Abate + Compli360 can therefore be ruled out.
 

Table 8: Results of methane measurements in pig slurry

Survey

The survey of three farmers yielded predominantly positive results. Two of the three farmers added the additive to their tanks of pig slurry, whilst one farmer used a tank of cattle manure. As the set-up is identical and the method of application differs only slightly, the statements from all three farmers can be taken into account equally in the survey.

The automatic dosing was found to be particularly convenient. This meant that the time required by the operators was kept to a minimum. The fact that there was no need for additional stirring was also well ­received. A follow-up survey carried out at one of the three farms two years after installation revealed that even the operation of a mobile agitator had not caused any visible damage to the pipework. However, all operators would like to have a control display (if no logger station has been installed) or remote monitoring (e.g. via a mobile app). An alarm relay or an additional level sensor in the IBC container could also be bene­ficial. Installation should be carried out by the manufacturer’s qualified personnel.

The time required was stated as ten minutes per week, provided that the active ingredient (IBC container) does not need to be replaced; otherwise, an additional two hours per IBC container should be allowed for.
All participants in the survey would use the technology again at any time if its positive effects were con­clusively proven.

Documentation

The operation of the dosing pump can be recorded via a data logger (optional) and saved in tabular form, including the date and time. In addition, purchase receipts for the active ingredient can be collated. This enables regulatory authorities to monitor the sustainable use of the dosing system.