Bio-acidification and enhanced crusting as an alternative to sulphuric acid addition to slurry to mitigate ammonia and greenhouse gases emissions during short term storage

Abstract

Several solutions are today proposed to farmers to minimize ammonia (NH 3 ) emissions during storage. In the present study, special attention was given to slurry acidification and slurry crust enhancement and our objective was to assess the effect of slurry bio-acidification using sugar and cheese whey as an alternative to sulphuric acid, and the potential of rice bran as crust enhancer on NH 3 and greenhouse gases emissions during storage. Both the cheese whey and the rice bran are materials, available in large amounts, with low commercial value in some EU regions as Portugal and its use, at farm scale, will be a win-win situation. Sugar is also a good alternative to acid attending its relatively low value. A laboratory experiment was performed for 2 months with five treatments: non-treated cattle slurry (CTRL), slurry treated with sulphuric acid (ACID), slurry treated with sugar (SUGAR), slurry treated with cheese whey (WHEY) and rice bran applied on the slurry surface (RICE). The SUGAR treatment led to a reduction of NH 3 emissions by 45% relative to CTRL while WHEY and RICE resulted in a reduction of 68% and 25%, respectively. Nevertheless, this effect of SUGAR and WHEY was shorter than in ACID, since NH 3 emissions started to be observed in those 2 treatments after 31 and 35 days of storage, respectively. Nitrous oxide emissions remained close to zero in ACID and SUGAR. RICE led to the highest emissions of carbon dioxide (CO 2 ) releasing almost 5% of carbon present in the initial mixture (slurry þ rice bran) and presented the highest methane emissions. The ACID and SUGAR led to a significant decrease of the total greenhouse gas (GHG) emissions. Our results indicate that bio-acidification using a source of sugar could be a good alternative to H 2 SO 4 to reduce simultaneously NH 3 and GHG emissions during storage.

Bio-Acidification of Animal Slurry: Efficiency, Stability and the Mechanisms Involved

“…One of the main concerns when adding easily degradable sources of C to slurries is the increase in C, especially through CH 4 emissions. Methane fluxes in non-preacidified treatments were in the range of previous studies by Kavanagh et al (2021), Prado et al (2020) and Bastami et al (2016). The addition of substrates promoted an initial peak in CH 4 release during the first week in all treatments, except for RS-glu2-ferm50 (Fig.…”

“…Bastami et al (2016) demonstrated 70 % and 31 % reductions in CH 4 emissions with a 7 % and 7.7 % inclusion of brewers' spent grain and milk, respectively. The addition of 3-33 % sugar beet residues resulted in an NH 3 volatilisation reduction of between 5 % and 26 % (Clemens et al, 2002), while 50 % inclusion of cheese whey reduced NH 3 volatilisation by 68 %, but equal GHG emissions were observed relative to the control (Prado et al, 2020). A recent study showed a 67 % reduction in NH 3 emissions from cattle slurry amended with 5 % sugar beet molasses, and CH 4 reductions ranging from 15 % to 70 % with a larger inclusion of the substrate (Kavanagh et al, 2021).…”

Slurry Acidification as a Solution to Minimize Ammonia Emissions from the Combined Application of Animal Manure and Synthetic Fertilizer in No-Tillage

“…Consequently, the acidified pig slurry amendment reduced the susceptibility of urea to nitrogen losses by ammonia volatilization. Despite sulfuric acid already being used at a farm scale, promising additives should emerge from several studies [38,39], helping to make slurry acidification more viable by decreasing the risk associated with the handling of hazardous products as well as the cost involved.…”

Dairy Slurry Application to Stubble-Covered Soil: A Study on Sustainable Alternatives to Minimize Gaseous Emissions

“…Soil moisture was adjusted to be close to 70% of soil water-holding capacity (WHC) in all pots. Ammonia fluxes were measured by a dynamic chamber technique based on the model depicted in [37], following the methodology described in [12]. To this end, a polyvinyl chloride chamber (Ø = 210 mm, h = 200 mm, area = 0.035 m 2 ) was used to cover the ground surface.…”