AgroTechnologyATLAS

Effects on air (emissions):

• The acidification proces can reduce risk of gaseous emisssions (COV, CH4, NH3) and odour problems. A Danish study has shown that frequent adjustment of the pH of pig slurry in a pig house (fattening pigs) with 1/3 drained floor and 2/3 slats reduced ammonia volatilization by 70% (Pedersen, 2004). Acidification of slurry also results in reduced ammonia volatilization from the slurry storage. A single trial (Kai et al., 2008) estimated losses from acidified slurry being less than 20% of the emission from an untreated uncovered storage facility. Ammonia losses during storage of manure are expected to be reduced by 50% compared with untreated slurry with naturally established crust (floating layer). Acidification of slurry reduces ammonia volatilization during and after field application as well. An experiment has shown that the accumulated ammonia measured seven days after application with trailing hoses was about 67 % lower for acidified pig slurry compared to untreated slurry (Kai et al., 2008). A possible effect of adding more acid and thereby lowering pH further will be minimum, because nearly all ammonia will be as ammonium at pH 5.5. There have been conducted olfactometric odor measurements for the two trials of acidification of slurry in slaughter houses (Pedersen, 2004 and 2007). The experiments showed no statistically significant effect in terms of odor by acidification. There are examples, that increased odor problems have been discovered locally around the process tank of the acidification unit. Elimination of the problem by mounting a carbon filter at the process tank. A laboratory study has shown that emissions of methane from the sulfuric acid treated cattle slurry was 90% lower than the untreated control slurry by measurements over 100 days in a semi-field systems (Petersen and Eriksen, 2008). Another laboratory study showed that emissions of methane from cattle manure stored for seven weeks was 67% lower than the untreated slurry (Hansen, 2008). The experiments provide no basis for clarifying the effect of acidification of slurry, but it can be concluded that acidification has a markedly negative effect on methane production during storage. The effect on methane emissions from pig stables and storage of pig manure is not known but it is expected that there will be a significantly reducing effects due to the ongoing acidification and aeration of the slurry. There are not assumed any net effect of slurry acidification on nitrous oxide emissions. Only through the substitution of nitrogen in commercial fertilizers with saved ammonia volatilization in the field fertilizer level, you can expect a lower nitrous oxide emission (IPCC, 2006).

Effects on water/soil (and management):

Other effects:

• The acidic media can inhibit some pathogens or microorganisms growth. The impact of this process over pathogens survival must be evaluated.

• The acidic media can inhibit some pathogens or microorganisms growth. The impact of this process over pathogens survival must be evaluated.

Conversion efficiency:

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).

Investment cost:

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).