Facilities for land spreading of livestock manure with a minimal loss of nutrients
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Application of an acidic reagent resulting in a decreased pH, which may be desired for the inactivation of pathogens and/or reduction of especially ammonia emissions.
The main objective of acidification of liquid manure is to lower the level of pH in the manure, and thereby increase the concentration of ammonium (NH4-N) at the expense of ammonia (NH3) – which will result in reduced free ammonia emission.
Tank for sulphuric acid (http://www.jhstaldservice.dk).
Addition of acid to the slurry leads to a decrease of the slurry pH, whereby the amount of ammonia nitrogen increasingly is transformed into ammonium (NH4+) that does not evaporate. By adding 4-6 kg concentrated sulfuric acid (H2SO4) per 1,000 kg pig slurry reduces the slurry pH to between pH 5.5 and 6.0. The acidification unit to treat the slurry, consists of the following main components: valve pit, process tank and acid tank. When processed, the manure from a number of slurry basins in the stable is pumped to the process tank via the valve pit. In the process tank, sulfuric acid is added so that the slurry pH is decreased to 5.5 (target), during stirring and combined with aeration. After treatment, the main part of the slurry is pumped back to the basins in the stable, while the rest is pumped to the storage tank. Treatment frequency depends on the slurry pH measured before each treatment, meaning the frequency increases with increasing initial pH. Normally, all the slurry in a herd will be treated 1-3 times daily. All processes are controlled and monitored automatically.
Effects on air (emissions):
Effects on water/soil (and management):
By adding 4-6 kg concentrated sulfuric acid (H2SO4) per 1,000 kg the pig slurry pH can be reduced up to pH value of 5.5-6.0. The acidification process has proven to be able to reduce the ammonia emission from pig houses and slurry storage by 65-70 %.
Net energy consumption - explanation:
Pedersen (2004) calculated an increased consumption of approx. 3 kWh/m3 slurry by using slurry acidification. The calculation is based on runtime and pump power and is therefore subject to some uncertainty. For the Infarm plant located in Randers (Report 4. Annex B), treating 10,000 m3/y the estimated electricity consumption is 1.8 kWh/m3.
Reagent 1 - explanation:
In the process there will be added approximately 4-6 kg concentrated sulfuric acid (H2SO4) per 1,000 kg pig slurry. The amount of reagent needed to attain a given pH is linked to the alkalinity of the manure. Treatments such as nitrification or CO2 stripping may help in reducing such reagent requirements (possible volatilization must be considered).
Ammonia is concentrated in the manure/slurry. Consequently, if the target of the adopted treatment is to concentrate nutrients in a fertilizing product (as pellets or concentrates obtained in evaporation or drying processes), acidification must be considered as a pre-requisite or pre-treatment for those process combination.
There is a basic investment in the range of 100,000 € at farm level (including storage tanks, pumps and controllers) but dependent on farm size and types of stables and other local parameters.
Quantifiable income - text:
Acidification of slurry is a technology that reduces ammonia emissions from both stables, storage facilities and at land application. Based on standard figures for manure (2008) it can be estimated that net saving is 17-19 kg NH3-N volatilization from stables, storage facilities and at application per. animal unit using acidification in pig houses. Acidification of manure means that the content of nitrogen in the manure at storage is 7-13% higher than in normal manure handling. By application with trail hoses of acidified slurry a 20-25% increase in fertilizer effect (bio-availability) is expected (Kai et al., 2008), while the nitrogen effect by injection of acidified slurry is not increased, because of the high nitrogen effect of injection already (Sørensen and Eriksen, 2009).