Acidification of animal slurry– a review

Advanced Processing of Food Waste Based Digestate for Mitigating Nitrogen Losses in a Winter Wheat Crop

“…These values were significantly lower than when the digestate was not acidified (D and D+NI), resulting in NH 3 losses of more than 27% of the total applied N ( Table 4). High NH + 4 content and pH of the digestate facilitate N losses via NH 3 volatilization (Fangueiro et al, 2015a;Möller, 2015) that can account up to more than a 40% of the total applied N if not managed carefully (e.g., Riva et al, 2016;Nicholson et al, 2017). Our results for the digestate treatments when the digestate was not acidified (D and D+NI) are consistent with these studies.…”

“…The variability of the feedstocks, digestate handling, transport, and storage in the local biogas plants and in tanks in the fields before the application could have caused changes in the digestate N content between the initial sampling time and the time of land application. It is well known that open stores (Wang et al, 2014), and the lack of semi-permeable materials to cover the tanks (Börjesson and Berglund, 2007) and protective gas-tight layers (Battini et al, 2014) can lead to large N losses, predominantly via NH 3 volatilization (Petersen and Sørensen, 2008;Fangueiro et al, 2015a), in comparison with the undigested feedstocks. Moreover, the pH of our digestate was 8.24 ± 0.01 at HF and 8.05 ± 0.01 at NW, and according to Muck and Steenhuis (1982), very high losses of NH 3 from digestate occurs above pH 8.0, and small losses below pH 6.0.…”

“…Tiwary et al (2015) reported that 35-65% of the total N applied in digestate can be lost through NH 3 volatilization if the digestate is surface broadcast. Potential methods to reduce NH 3 volatilization include the rapid incorporation of manures and digestates into the soil after application (Möller et al, 2008;Tiwary et al, 2015), soil injection (Riva et al, 2016), bandspreading (Nicholson et al, 2017), and acidification of slurries (Fangueiro et al, 2015a).…”

Alternatives to sulfuric acid for slurry acidification: impact on slurry composition and ammonia emissions during storage

“…Slurry acidification decreases NH 3 emissions efficiently as it modifies slurry characteristics (Fangueiro et al, 2015;Hjorth et al, 2015). This treatment is currently performed at the farm scale in Denmark by addition of concentrated sulfuric acid (H 2 SO 4 ).…”

“…A recent study reviewed the acidification practices and mentioned the need for alternatives, for the optimization of slurry management (Fangueiro et al, 2015).…”