Figure 6 - available via license: Creative Commons Attribution 4.0 International
Content may be subject to copyright.
The pH value of dairy cow slurry after acidification with sulfuric acid to pH values of 5.5, 4.5, and 3.0 during the storage period of 48 days (means ± SD, n = 3).
Source publication
Acidification of slurry is a common practice to reduce ammonia and methane emissions. Sulfuric acid is usually used for this process. However, this has been criticized due to the high sulfur input into soils. Therefore, the objective of this study is to show the effectiveness of a one-time acidification with alternative acids also in combination wi...
Contexts in source publication
Context 1
... the pH value to 4.5 resulted in a half as strong pH increase as compared with the acidified slurry to pH 5.5 by day 9 (+0.7 and +1.5 pH units, respectively). After 48 days, the difference between these two variants was 0.9 pH units, which approximately equals the initial difference in acidification ( Figure 6 and Table S6). Acidification of the Figure 5. ...
Context 2
... the pH value to 4.5 resulted in a half as strong pH increase as compared with the acidified slurry to pH 5.5 by day 9 (+0.7 and +1.5 pH units, respectively). After 48 days, the difference between these two variants was 0.9 pH units, which approximately equals the initial difference in acidification ( Figure 6 and Table S6). Acidification of the dairy cow slurry to pH 3.0 resulted in a permanently low pH value during the entire storage period. ...
Context 3
... pH reduction could only be observed if slurry is acidified to pH 3.0 ( Figure 6). Apart from that, the pH value of all treatments in our investigation increased again during the storage period of 48 days. ...
Context 4
... Hörnig et al. [49] also observed an increase in pH value because of complete homogenization of the samples in the case of acidified slurry at pH values of 4.3 and 4.8, whereas they found no effect for the samples acidified to pH 3.8 [49]. Possibly, the pH value is then already so low that no more biological conversion processes can take place, and therefore these processes cannot be affected by the atmospheric oxygen ( Figure 6). ...
Citations
... The acidification of the mesophilic faeces digestate reduced the initial pH to 5.2, however, at the end of the experiment the pH had increased to 6.2 as a result of the buffering capacity of the digestate. This increase in pH is similar to what is found for slurry acidified prior to storage (Sørensen and Eriksen, 2009;Overmeyer et al., 2021). On the other hand, the urine that was also acidified to 5.5 maintained a stable pH of around 5.1 until the end of the experiment. ...
... The urine maintained a stable pH (5.4 ± 0.3) throughout the experiment without requiring additional acid. This is in contrast to slurry acidification where re-acidification and thus more acid is needed to maintain a pH of 5.5 because of its high buffer capacity (Sørensen and Eriksen, 2009;Overmeyer et al., 2021). Further, in this research sulfuric acid was used to reduce pH. ...
... A key conclusion of this study is that frequent monitoring and adjusting the pH of DSWs are critical for duckweed cultivation, valorisation, and remediation. Acidification of slurry on farms is a method already employed to reduce greenhouse gas emissions and reduce nitrogen losses [9,62,63]. Furthermore, dairy farms regularly use phosphoric acid to clean milking lines and equipment. Therefore, the idea of acidifying DSW is realistic in agricultural settings. ...
As a result of intensive agriculture, large quantities of liquid wastewaters are produced. Dairy soiled water (DSW) is produced in large volumes during the milking process of cattle. It comprises essential plant nutrients such as nitrogen, phosphorus, and potassium. The physicochemical properties of DSWs are highly variable as per individual farmer practices and seasonality. Currently, DSWs are disposed of primarily through land spreading, which frequently results in environmental pollution through land runoff. As a result of the large volumes produced coupled with the high variability, there are few alternative uses for DSWs, with presently little consideration of possible on-farm valorisation. Through a series of factorial experiments, the suitability of DSW as a novel duckweed (Lemna minor L.) cultivation medium is assessed. Different concentrations and pH values are assessed to determine the optimal conditions to support duckweed cultivation. Under the principles of circular economy, duckweed-based valorisation of DSWs can lead to the production of valuable, high-protein plant biomass that could be incorporated into animal feed to support livestock nutritional requirements. This study identifies the management of DSW's pH as a key growth parameter in the successful cultivation of duckweed to underpin a circular economy approach for valorisation and improved environmental outcomes.
... Acidification of pig slurry is known to be an effective method for the inhibition of NH 3 emission associated with agricultural waste processing. Various acids such as acetic acid (Regueiro et al., 2022), hydrochloric acid (Overmeyer et al., 2021), and sulfuric acid (Park et al., 2018;Lee et al., 2022) have been investigated. Sulfuric acid is the most popular method for the mitigation of NH 3 emission because of its low cost and additional sulfur fertilizer effect. ...
... The small CH 4 uptake by IF and TPS is not unexpected, as methanotrophy occurs in well-drained agricultural soils (Serrano-Silva et al. 2014). Inorganic fertiliser does not contain a C source to facilitate methanogenesis (Moreno-Garcia et al. 2020), and thus CH 4 production, and the plasma induction process prevents CH 4 production during slurry storage by acidifying the slurry and reducing its pH (Tooth 2021; Petersen et al. 2012;Overmeyer et al. 2021;Ambrose et al. 2023), so no CH 4 was emitted from IF and TPS upon application. There is the potential for CH 4 to be produced in soil, and then emitted, following the application of slurry due to the anoxic conditions created by rapid C mineralisation after the input of C in the organic fertiliser (Le Mer and Roger 2001;Yuan et al. 2019), this accounts for the elevated CH 4 emissions from PS. ...
The use of livestock waste as an organic fertiliser releases significant greenhouse gas emissions, exacerbating climate change. Innovative fertiliser management practices, such as treating slurry with plasma induction, have the potential to reduce losses of carbon and nitrogen to the environment. The existing research on the effectiveness of plasma-treated slurry at reducing nitrous oxide (N2O) and methane (CH4) emissions, however, is not comprehensive, although must be understood if this technology is to be utilised on a large scale. A randomised block experiment was conducted to measure soil fluxes of N2O and CH4 from winter wheat every two hours over an 83-day period using automated chambers. Three treatments receiving a similar amount of plant-available N were used: (1) inorganic fertiliser (IF); (2) pig slurry combined with inorganic fertiliser (PS); (3) plasma-treated pig slurry combined with inorganic fertiliser (TPS). Cumulative N2O fluxes from TPS (1.14 g N m⁻²) were greater than those from PS (0.32 g N m⁻²) and IF (0.13 g N m⁻²). A diurnal pattern in N2O fluxes was observed towards the end of the experiment for all treatments, and was driven by increases in water-filled pore space and photosynthetically active radiation and decreases in air temperature. Cumulative CH4 fluxes from PS (3.2 g C m⁻²) were considerably greater than those from IF (− 1.4 g C m⁻²) and TPS (− 1.4 g C m⁻²). The greenhouse gas intensity of TPS (0.2 g CO2-eq kg grain⁻¹) was over twice that of PS (0.07 g CO2-eq kg grain⁻¹) and around six times that of IF (0.03 g CO2-eq kg grain⁻¹). Although treating pig slurry with plasma induction considerably reduced CH4 fluxes from soil, it increased N2O emissions, resulting in higher non-CO2 emissions from this treatment. Life-cycle analysis will be required to evaluate whether the upstream manufacturing and transport emissions associated with inorganic fertiliser usage are outweighed by the emissions observed following the application of treated pig slurry to soil.
... In this case NH 3 emissions can be reduced up to 95% or even totally (Husted et al., 1991;Petersen et al., 2012). When acid addition lowers the pH to 5.5 it tends to rise faster, returning to the initial level between 12 and 60 days (Overmeyer et al., 2021; and this also affects NH 3 and GHG emissions. reports a reduction in NH 3 emissions of 70% for pig slurry and 85% for cattle slurry after 60 days from the addition of H 2 SO 4 , as result of a pH rise from 5.5 to approximately 7. Comparable results are shown by Husted et al. (1991) after 21 days from the addition of hydrochloric acid (HCl) at different dosages, highlighting reductions in NH 3 emissions of 35% with a pH lowered to 7.2; 60% with a pH of 6.8; 90% with a pH of 6.5; 100% with a pH of 5.8. ...
... However, its use and effectiveness as a one-time acidification strategy for slurries during long-term tank storage before field application are unknown. The potential of achieving and keeping a constant pH throughout the slurry storage period by one-time acidification can save resources and protect the environment (Overmeyer et al., 2021). ...
... A key benefit in altering slurry pH is mitigation of nitrogen (N) losses to the atmosphere via gaseous NH 3 Overmeyer et al., 2021). Since NH 3 is a nitrogenous compound, the N fertilizer value of the slurry is also increased. ...
... As alternatives to inorganic acids, organic acids (like acetic acid and citric acid) have also been assessed for their efficacy to reduce pH . A typical target pH is 5.5 since, at this range, the NH 4 + /NH 3 equilibrium favours NH 4 + (Overmeyer et al., 2021). Fangueiro et al. (2015) reported up to 70% and 88% NH 3 reduction with H 2 SO 4 during in-house and storage acidification, respectively. ...
... However, high doses of sucrose-rich additives are required to initiate and maintain the fermentation process, and this may not be economically viable since sucrose is often more valuable for other applications. Combining slurry acidification using H 2 SO 4 followed by the addition of glucose and/or sucrose-rich additives has been explored as an alternative (Overmeyer et al., 2021;Regueiro et al., 2022). Preacidification of swine slurry with H 2 SO 4 to pH 5.5 followed by glucose addition (2% and 4%) appeared to maintain pH below 5 more consistently than glucose (2%) treatment alone (Regueiro et al., 2022). ...
This chapter discusses optimizing slurry management in agricultural practices. It begins by first highlighting current decision tools for optimizing manure management, then goes on to review modifying animal slurry pH to enhance its value as a biobased fertilizer through methods such as bio acidification and alkalinization. A section on improving manure management systems to minimize trade-offs is also provided, followed by an overview of combining manure management with anaerobic digestion. The chapter also reviews pre- and post-treatment for anaerobic digestion as well as the optimization of anaerobic digestion operations to optimize digestate quality.
... Acidification or alkalinization require the use of chemical additives, while bio-acidification implies the addition of organic substrates rich in easily fermentable carbohydrates (Fangueiro et al., 2015;Regueiro et al., 2022). Problems associated with the use and handling of strong mineral acids, such as H 2 SO 4 , have long been discussed (Regueiro et al., 2016b;Overmeyer et al., 2021). In addition, the acidification cost by applying 6 L of H 2 SO 4 m − 3 pig slurry can be as high as 2.4 euro m − 3 slurry (assuming a cost for H 2 SO 4 of 0.4 euro per litre), considerably increasing the overall slurry management costs (Prado et al., 2020). ...
... In the work of Regueiro et al. (2022), the pre-acidification of pig slurry to pH 5.5 with H 2 SO 4 followed by the addition of 4% glucose resulted in a reduction of the pH to 3.9, which was maintained until Day 98 of the storage experiment. On the contrary, no pH reduction was observed after the application of glucose (0.01 mol glucose Kg − 1 slurry) in pig slurry pre-acidified to pH 5.5 (Overmeyer et al., 2021). It is evident that the pH level at which slurry is pre-acidified and the amount of labile carbon source added are relevant. ...
... The pH increase observed by all treatments during the second half of the midterm storage can be a result of many factors. According to Overmeyer et al. (2021), storage temperature can have an impact on the slurry biodegradation processes, and therefore, the pH of the slurry increases over time. In the present study, the ambient temperature was controlled at 22 ± 2 • C, a range in which microbial activity is not particularly low. ...
... The process of manure acidification, where sulfuric or other similar acids are introduced into manure, effectively reduces ammonia emissions, a significant environmental concern in dairy farming. By lowering the pH, this technique inhibits the volatilization process of ammonia, thereby curtailing its release into the atmosphere [78][79][80][81][82]. Moreover, acidified manure presents added benefits for soil health, particularly in enhancing nutrient retention and availability. ...
In recent years, the Canadian dairy sector has faced escalating challenges due to its significant contribution to greenhouse gas emissions, particularly methane. This paper critically examines a spectrum of innovative techniques aimed at mitigating methane emissions within this sector, scrutinizing their cost-effectiveness, efficiency, compatibility with animal welfare standards, and adherence to both existing and prospective Canadian environmental legislations. The discourse begins with an exhaustive overview of contemporary methane reduction methodologies relevant to dairy farming, followed by a rigorous analysis of their economic feasibility. This includes a detailed cost-benefit analysis, juxtaposed with the efficiency and technological advancements these techniques embody. A pivotal aspect of this examination is the alignment of animal welfare with emission reduction objectives, ensuring that the strategies employed do not compromise the health and well-being of dairy cattle. Furthermore, the paper delves into the legislative landscape of Canada, evaluating the congruence of these techniques with current environmental laws and anticipating future regulatory shifts. Performance indicators for emission reduction are critically assessed, establishing benchmarks tailored to the Canadian context. This is complemented by an exploration of the market potential of these innovations, including factors influencing their adoption and scalability in the market. The analysis culminates with a synthesis of case studies and best practices within Canada, offering insights into successful implementations and drawing lessons for future endeavors. This comprehensive approach not only addresses the immediate environmental and health impacts associated with dairy farming emissions but also significantly contributes to the overarching goal of sustainable development in the agricultural sector. The research presented in this paper holds significant implications for the future of sustainable dairy farming, offering a model for addressing environmental challenges while maintaining economic viability and animal welfare.
... Acidification of pig slurry has an influence on the electrical conductivity (EC) of the pig slurry; when sulfuric acid is introduced to the slurry, it dissociates into hydrogen ions (H + ) and sulfate ions (SO 4 2− ), which leads to a decrease in the pH due to the release of hydrogen ions (H + ), thus contributing to a higher electrical conductivity [67], as presented in Table 1. Biological additives presented no significant effects on the electrical conductivity of the slurry and it had almost the same comportment as the control tank, while the pH had a significant effect between the first and fifth week; this can be explained by the microbial degradation of organic matter in the slurry, which results in the formation of carbonate and ammonium [68] and thus leads to an increase in pH value, from 7.41 to 8.2. ...
This study addresses the challenge of mitigating ammonia and greenhouse gas (GHG) emissions from stored pig slurry using chemical and biological additives. The research employs dynamic chambers to evaluate the effectiveness of these additives. Chemical agents (sulfuric acid) and biological additives (DAB bacteria) containing specific microbial strains are tested (a mixture of Rhodopseudomonas palustris, Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus licheniformis, Nitrosomona europea, Nictobacter winogradaskyi, and nutritional substrate). Controlled experiments simulate storage conditions and measure emissions of ammonia, methane, and carbon dioxide. Through statistical analysis of the results, this study evaluates the additives’ impact on emission reduction. Sulfuric acid demonstrated a reduction of 92% in CH4, 99% in CO2, and 99% in NH3 emissions. In contrast, the biological additives showed a lesser impact on CH4, with an 8% reduction, but more substantial reductions of 71% for CO2 and 77% for NH3.These results shed light on the feasibility of employing these additives to mitigate environmental impacts in pig slurry management and contribute to sustainable livestock practices by proposing strategies to reduce the ecological consequences of intensive animal farming.
