We have collected some of the frequently asked questions related to acidification of slurry, and we have answered them below.
Do you have any other questions, please feel free to contact us, here.
How much does your system reduce ammonia emissions?
64 % from pig barns (documented by VERA)
50 % from cattle barns (documented by VERA)
How much acid is to be used to achieve this effect?
Around 6-8 kg / m3 – it depends on the amount of dry matter content in the slurry. The more solids in the slurry, the more sulfuric acid we need to acidify.
1 liter of sulfuric acid = 1.8 kg
Why do you use sulfuric acid?
We use sulfuric acid with 93-96 % purity because it is a stable acid that works effectively in changing ammonia NH3 into ammonium NH4+, which is a plant available N-form that does not evaporate. The sulfur content in sulfuric acidified slurry is usefull for crops in fields. Sulfuric acidified slurry does not damage concrete and inventory in the barn. And last but not least, sulfuric acid is very cheap!
Can other acids be used for acidification of slurry?
Sulfuric acid has in many tests proved to be the most effective acid. Acidification of slurry requires great knowledge and experience of working with acid in the slurry . A knowledge that we have built over the last more than 15 years.
When not working correctly with acids in slurry, you risk the carbon dioxide levels to increases uncontrollably, which transfers to intense foam building. There can be formed C2H6S [Dimethylsulfide] that smells extremely unpleasant, and reduces the acid effect. With insufficient knowledge about the process there is also a risk of forming dangerous H2S [hydrogen sulphide].
When using other acids, for example, nitric acid, there is a risk of damaging inventory (corrosion of iron). The acid is strongly oxidizing, and the high content of organic matter in slurry typically means that approx. 1/3 of the acid goes to the formation of carcinogenic nitrous gases [NO2]. Nitric acid is typically about three times more expensive than sulfuric acid. And it comes only in lower concentration (66%) and thus decreased effectiveness when acidifying.
Is sulfuric acid dangerous?
Sulfuric acid in pure form is potentially very harmful, but in a JH NH4 + acidification system, acid is stored and handled in a closed system – the farmer is, and should never come, in contact with the sulfuric acid! Delivery of sulfuric acid to the sulfuric acid tank is carried out only by trained personnel who have an ADR certificate and are used to handle acids.
Is hydrogen sulphide (H2S) a problem in the acidified slurry?
No! Hydrogen sulfide is formed by microorganisms, which at the low pH of the acidified slurry cannot multiply. Acidified slurry is therefore associated with a much lower content of hydrogen sulphide than normal slurry.
Hydrogen sulfide builds up preferably in static slurry. In barns where the slurry is acidified, the slurry is in constant moving, meaning that the conditions for the forming of hydrogen sulphide is not present.
What is the amount of sulfuric acid in the slurry when it is acidified?
The sulfuric acid is used only to alter the chemical balance in the slurry, there is no pure sulfuric acid in the slurry after treatment.
What is the amount of N increases in the slurry when it is acidified?
10-15% in barns with full acidification.
What about other greenhouse gases – are they also reduced when acidifying?
Yes, nitrous oxide and methane emissions from stable and storage are also reduced significantly with acidification of slurry.
From when will the investment in an acidification system be economically profitable?
The system is economically profitable from the first day – in animal welfare, lower disease pressure and more N in the slurry. Higher yields – up to 15% – by using acidified slurry with more plant-available N will be available after the first slurry spreadings.
Are there other suppliers of slurry acidification systems?
The JH NH4+ system is patented and the only system that can acidify the slurry inside the stable, reducing emissions of ammonia (nitrogen) from both stable, storage and fields. Other systems only reduce emissions from the field.
The JH NH4 + systems have a proven effect on ammonia emissions and are therefore included on the VERA technology list as well as offered in Denmark as Best Available Technology (BAT).
We already have an existing barn. Can your product be implemented in it?
Our experience is that slurry systems in 80 % of the existing stables can be converted to acidification.
To meet environmental requirements of bringing down ammonia emissions when expanding a farm, it will often be necessary to establish acidification in both new buildings and a part of the existing stables.
How much extra work will I get if I choose to implement your system?
Compared to traditional slurry systems the only extra works is in controlling pH and make sure there is always sulfuric acid available in the tank. This is done by a single reading on the control screen. The handling of slurry is fully automatic, no more slurry plugs must be lifted for manually sluicing slurry out. On the contrary, implementing a JH NH4+ system should result in significant time savings!
Does is smell unnecessarily in the barn, when the barn is emptied and filled with pH-regulated slurry again?
No. We do not empty slurry pipes completely, as it will result in slurry ventilation. The air which is pumped back into the barn, is the same air, which is already inside the barn.
Does pH-regulated slurry require increased need for supply of lime on fields?
Theoretically you need to supply agricultural lime, but in practice the actual need is marginally.
What is the use of nitrogen in acidified slurry?
Field trials demonstrate that the use of N in acidified, pH-regulated slurry is:
Pig slurry 95% versus about 70% in non-acidified slurry (Source: Danish Institute of Agricultural Research)
Cattle slurry is about 65% versus about 40% in non-acidified slurry (Source: Danish Institute of Agricultural Research)
Is acidified slurry harmful to concrete and inventory?
There has been carried out extensive studies of the influence of acidified slurry on different concrete qualities.
The conclusion is that constructions that use standard concrete qualities (added 15% fly ash) are not expected to have durability problems over a 25 year time period.
For existing livestock facilities acidified slurry is expected not to pose any significant risk to constructions, provided that the concrete otherwise meet the requirements of the relevant environmental classes.
CtO’s recommendations can be downloaded (Document produced by Aalborg Portland) here: Concrete quality_Aalborg_Portland (EN)
Can you log operation of the system?
Yes, the operation is logged and can be followed via cell phone or on your computer over the Internet.
Is there a more simple / cheap version for acidifying slurry?
No, it will never be more simple and cheap. The only thing we need to install a system is a slalom channel inside a cattle barn and a vucuum system in a pig barn.