Manure Slurry Research Articles

An Experimental Field Trial Investigating the Use of Bacteriophage and Manure Slurry Applications in Beef Cattle Feedlot Pens for Salmonella Mitigation.

Post-harvest Salmonella mitigation techniques are insufficient at addressing Salmonella harbored in cattle lymph nodes, necessitating the exploration of pre-harvest alternatives that reduce Salmonella prior to dissemination to the lymph nodes. A 2 × 2, unbalanced experiment was conducted to determine the effectiveness of pre-harvest treatments applied to the pen surface for Salmonella mitigation in cattle. Treatments included manure slurry intended to mimic pen run-off water (n = 4 pens), a bacteriophage cocktail (n = 4), a combination of both treatments (n = 5), and a control group (n = 5) that received no treatment. Environment samples from 18 feedlot pens and fecal grabs, hide swabs, and subiliac lymph nodes from 178 cattle were collected and selectively enriched for Salmonella, and Salmonella isolates were sequenced. The combination treatment was most effective at reducing Salmonella, and the prevalence was significantly lower compared with the control group for rump swabs on Days 14 and 21. The treatment impact on Salmonella in the lymph nodes could not be determined due to low prevalence. The reduction on cattle hides suggests that bacteriophage or water treatments applied to the feedlot pen surface may reduce Salmonella populations in cattle during the pre-harvest period, resulting in reduced contamination during slaughter and processing.

Acidification increases efficiency of Lemna minor N and P recovery from diluted cattle slurry

Livestock slurry is high in N and P and as such is a valuable fertiliser, however, poorly timed or overapplication can result in the eutrophication of surface water. As a result, the agricultural industry is subject to increasingly stringent slurry management regulations, leading to interest in novel methods of recovering nutrients from wastewater. This study investigated the potential for using Lemna minor to recover N and P from slurry over a five-week trial, assessing whether previously reported increased growth on acidified wastewater translates into greater nutrient removal. It was hypothesised that acidifying diluted slurry with H2SO4 would lead to greater (i) reductions in total ammonia nitrogen (TAN) and PO43- concentrations and (ii) cumulative N and P uptake by L. minor, relative to unamended diluted slurry (control). Consistent with previous studies, L. minor growth was significantly higher in the acidified treatment relative to the control, with greater reductions in PO43- concentrations also observed in the acidified treatment. Contrary to the first hypothesis, the same was not observed for TAN, where final concentrations were lowest in the control despite poor growth on this medium. Consistent with the second hypothesis, greater cumulative L. minor N uptake over the five-week trial was observed from the acidified treatment, with L. minor uptake accounting for 94.8 % of the reduction in inorganic N concentration, relative to 7.5 % in the control. Cumulative P recovery from the acidified treatment was also significantly higher than in the control, with L. minor uptake accounting for 99.5 % of the reduction in the inorganic P concentration of the acidified diluted slurry, relative to only 18 % in the control. Our findings have important implications for the operation of duckweed growing systems in practice. We show that lowering pH enabled efficient PO43- recovery, to the point where its concentrations may have been limiting to growth. Lowering pH also increased the proportion of N and P removal directly attributable to L. minor uptake, increasing the efficiency of the nutrient recovery process whilst also minimising the amount of N lost via other pathways such as gaseous emissions.

Low-Temperature Vacuum Evaporation of Ammonia from Pig Slurry at Laboratory and Pilot-Plant Scale

Livestock manure has a high ammonium content that can limit its direct application on soil as a fertiliser in nitrate-vulnerable zones. Treatment technologies that are able to extract ammonium from livestock manure allow it to be concentrated in small volumes, making it cheaper and easier to transport and use as fertiliser in crop areas where there is a deficit of nitrogen. This study proposed using low-temperature vacuum evaporation to treat pig slurry in order to obtain marketable products that can be used as fertilisers and help close the nitrogen cycle. Two different configurations and scales were used. The first was a seven-litre laboratory-scale evaporator complemented with a condenser, a condensate trapper, an acid trap and a vacuum pump operated at −90 kPa vacuum pressure and at three different temperatures: 50.1 ± 0.2 °C, 46.0 ± 0.1 °C and 45.3 ± 1.3 °C. The second, Ammoneva, is an on-farm pilot-scale evaporator (6.4 m3), capable of working in four-hour batches of 1 t of liquid fraction of pig slurry with an operating temperature of 40–45 °C and −80 kPa vacuum pressure. The laboratory-scale evaporator, which features several novel improvements focused on increasing ammonia recovery, showed a higher nitrogen removal efficiency from the liquid fraction of pig slurry than the on-farm pilot plant, achieving 84% at 50.1 °C operation, and recovering most of it in ammonia solution (up to 77% of the initial nitrogen), with 7% of the ammonia not recovered. The Ammoneva pilot plant achieved a treated liquid fraction with 41% of initial nitrogen on average, recovering 15% in the ammonia solution in the acid trap; so, the NH3 gas absorption step needs to be further optimised. However, due to the simplicity of the Ammoneva pilot plant, which is easily placed inside a 20-foot container, and the complete automation of the process, it is suitable as an on-farm treatment for decentralised pig slurry management. The implementation of the novel design developed at laboratory-scale could help further increase recovery efficiencies at the pilot-plant scale.

Organic Manuring in Freshwater Aquaculture and Its Impact on Pond Ecosystem and Fish Health: An Overview

The use of organic manure in aquaculture had been practiced since centuries in India, China and other Far East countries. Sustainability of aquaculture farming depends upon ecofriendly, economically and socially viable culture systems. The recycling of organic wastes for fish culture serves the dual purpose of cleaning the environment by avoiding the problem of waste disposal and providing economic benefits. The recycling of animal dung/wastes in fish ponds for natural fish production is important to sustainable aquaculture and to reduce expenditure on costly feeds and fertilizers which form more than 60% of the total input cost. Integrating aquaculture with animal husbandry results in the most rational utilization of organic manures. However, the indiscriminate use of these manures in fish ponds, instead of improving the pond productivity, may also lead to pollution causing negative impact on the dissolved oxygen regime of the fish ponds and may cause problems to fish health. Therefore, it is necessary to understand the standard doses of these wastes which would keep the physico-chemical parameters of pond water in a favorable range required for the survival and growth of fish. When organic manure is applied in aquaculture ponds, best results are obtained with its frequent applications. Judicious organic manuring of fish ponds can eliminate the need for supplementary feeding. Although a lot of work has been done on the utilization in fish culture ponds, of animal manures, particularly farmyard manure, poultry droppings, cow dung and biogas slurry which are suitable substitutes for costly feeds and fertilizers. In the present review, an attempt has been made to elucidate the present status of organic manuring in fish culture systems and its impact on pond ecology and fish health.

Mitigation of greenhouse gas emissions in pasture-based dairy-beef production systems

CONTEXTAgriculture and food systems contribute significantly to climate change. Greenhouse gas (GHG) emissions intensity from beef production are high when compared to other livestock production systems and, therefore, mitigation of these emissions is urgently required. In many countries dairy-beef is making a large and growing contribution to total beef output thereby reducing net emissions given the lower emissions intensity of beef originating from the dairy herd when compared to specialized beef-cow systems. GHG emissions from dairy-beef systems can be further reduced by adopting best practice and mitigation technologies. OBJECTIVESThe objectives of this study were to (1) evaluate a range of management practices to reduce GHG emissions for pasture-based beef cattle production systems, (2) model the individual and combined impacts of these management practices on GHG emissions from dairy-beef systems, and (3) identify any trade-offs between GHG emissions mitigation, farm profitability, food security and land use. METHODSA farm level bioeconomic systems model was modified to evaluate spring-born, steer production systems finishing cattle at differing slaughter ages and from contrasting forage-based finishing diets (grazed grass or grass silage, each supplemented with concentrates). Mitigation measures included earlier slaughter age, optimal slurry management, urease inhibitors for nitrogen (N) fertilizers, replacing cereals with ‘by-products’ in concentrate feed rations and incorporating clover in grassland pastures. RESULTS AND CONCLUSIONSCombining mitigation strategies reduced dairy-beef systems GHG emissions intensity by an average of 21%. Incorporating clover in grassland pastures was found to be the most profitable stand-alone mitigation strategy increasing net margin by an average of 18%. Substituting by-products for barley in a concentrate ration converted all systems into net producers of human edible protein; otherwise, steer systems finishing at pasture during the third grazing season were the only net producers of human-edible protein. However, finishing at pasture during the third grazing season increased GHG emissions per animal and per kilogram of beef carcass. SIGNIFICANCEWithin a grass-based dairy-beef system, such as that modelled in this study, a number of complementary GHG emissions mitigation strategies can be implemented, without making substantive changes to the production system, while simultaneously improving farm profitability.

Contribution of Manure-Spreading Operations to Bioaerosols and Antibiotic Resistance Genes' Emission.

Manure spreading from farm animals can release antibiotic-resistant bacteria (ARB) carrying antimicrobial resistance genes (ARGs) into the air, posing a potential threat to human and animal health due to the intensive use of antibiotics in the livestock industry. This study analyzed the effect of different manure types and spreading methods on airborne bacterial emissions and antibiotic resistance genes in a controlled setting. Cow, poultry manure, and pig slurry were spread in a confined environment using two types of spreaders (splash plate and dribble bar), and the resulting emissions were collected before, during, and after spreading using high-volume air samplers coupled to a particle counter. Total bacteria, fecal indicators, and a total of 38 different subtypes of ARGs were further quantified by qPCR. Spreading poultry manure resulted in the highest emission rates of total bacteria (1011 16S gene copies/kg manure spread), Archaea (106 16S gene copies/kg manure), Enterococcus (105 16S gene copies/kg manure), and E. coli (104 16S gene copies/kg manure), followed by cow manure and pig slurry with splash plates and the dribble bar. Manure spreading was associated with the highest rates of airborne aminoglycoside genes for cow and poultry (106 gene copies/kg manure), followed by pig slurry (104 gene copies/kg manure). This study shows that the type of manure and spreading equipment can affect the emission rates of airborne bacteria, and ARGs.

Response surface optimization of chemical coagulation for solid–liquid separation of dairy manure slurry through Box–Behnken design with desirability function

Discharging livestock manure slurry without proper treatment causes various environmental and sociological problems. Chemical coagulation is a widely used and easily applicable method for treating such wastewater. However, the technique requires optimization to enhance coagulation efficiency while minimizing chemical usage. In this study, we propose an efficient, low-cost, and environmentally safe chemical coagulation method for solid–liquid separation of dairy manure slurry. Experiments were conducted in laboratory jar tests using dairy manure slurry to investigate the impact of coagulants, specifically polyaluminum chloride (PAC) and cationic polyacrylamide (CPAM), as well as pH, on the process of solid-liquid separation. Preliminary ranges of PAC, CPAM, and pH were estimated through single-factor experiments. Coagulation optimization and modeling were performed using the response surface methodology (RSM) with the Box-Behnken design (BBD), wherein the desired goal of each parameter was set to maximize solid–liquid separation efficiency while reducing chemical dosage to maintain residual aluminum (Al) concentrations below water quality standards. Numerical optimization predicted that the optimal dosages were 75 mg/L of PAC and 35 mg/L of CPAM at pH 7. Under these conditions, removal efficiencies of 99% for turbidity and 97% for chemical oxygen demand (COD) were achieved, with a minimal residual Al concentration of 0.045 mg/L. Positive zeta potential values in the treated water confirmed complete separation of negatively charged solids in the dairy manure slurry. The response values predicted by BBD aligned with the experimental results, and the analysis of variance (ANOVA) demonstrated the predictability and accuracy of the response models. Consequently, this study highlights the practical application of RSM with BBD in optimizing chemical coagulation using PAC and CPAM to achieve efficient solid–liquid separation in livestock wastewater while maintaining low residual Al concentrations.

Persistence of Antibiotic Resistance Genes Varies with Particle Size and Substrate Conditions in Recirculating Streams.

Antibiotic resistance (AR) determinants are enriched in animal manures, a significant portion of which is land-applied as a soil amendment or as fertilizer, leading to potential AR runoff and microbial pollution in adjacent surface waters. To effectively inform AR monitoring and mitigation efforts, a thorough understanding and description of the persistence and transport of manure-derived AR in flowing waters are needed. We used experimental recirculating mesocosms to assess water-column removal rates of antibiotic resistance genes (ARGs) originating from a cow manure slurry collected from a dairy farm. We quantified the effect of three benthic (i.e., bottom) substrate variations and particle sizes of manure slurry on water column removal rates. Overall, we observed variation in ARG behavior across substrate treatments and particle sizes. For ARGs associated with small particles, removal rates were higher in mesocosms with a substrate. tetW was typically removed at the highest rates across particle size and treatment, followed by ermB and blaTEM. Our data suggests that both substrate character and particle size exert control on the fate and transport of ARGs in surface waters, laying the foundation for future research in this area to establish a predictive framework for AR persistence and fate in flowing waters.

Biochar–coupled organic fertilizer reduced soil water-dispersible colloidal phosphorus contents in agricultural fields

Soil water-dispersible colloidal phosphorus (WCP) presents high mobility, however, the regulatory effect of biochar-coupled organic fertilizer is rarely known, especially under different cropping patterns. This study investigated the P adsorption, soil aggregate stability, and WCP in three paddy and three vegetable fields. These soils were amended with different fertilizers (chemical fertilizer, CF; substitution of solid-sheep manure or liquid-biogas slurry organic fertilizer, SOF/LOF; substitution of biochar-coupled organic fertilizers, BSOF/BLOF). Results presented that the LOF averagely increased the WCP contents by 50.2% across the sites, but the SOF and BSOF/BLOF averagely decreased their contents by 38.5% and 50.7% in comparison with the CF. The WCP decline in the BSOF/BLOF-amended soils was mainly attributed to the intensive P adsorption capacity and soil aggregate stability. The BSOF/BLOF increased the amorphous Fe and Al contents in the fields in comparison with the CF, which improved the adsorption capacity of soil particles, further improving the maximum absorbed P (Qmax) and reducing the dissolved organic matter (DOC), leading to the improvement of > 2 mm water-stable aggregate (WSA>2mm) and subsequent WCP decrease. This was proved by the remarkable negative associations between the WCP and Qmax (R2 = 0.78, p < 0.01) and WSA>2mm (R2 = 0.74, p < 0.01). This study manifests that biochar-coupled organic fertilizer could effectively reduce soil WCP content via the improvement of P adsorption and aggregate stability.

Adapted business model canvas template and primary market research for project-based learning on management of slurry

Adapted business model canvas template and primary market research for project-based learning on management of slurry

Effects of atmospheric and manure surface conditions on H2 S emissions from an in-ground finisher hog manure slurry tank.

Hydrogen sulfide (H2 S) emitted by livestock operations can be detrimental to human health. The storage of hog manure is a significant agricultural source of H2 S emissions. H2 S emissions from a ground-level Midwestern hog finisher manure tank were measured for 8-20 days each quarter over a 15-month period. After excluding 4 days with outlier emissions the mean daily emission was 1.89g H2 S m-2 day-1 . Mean daily emission was 1.39g H2 S m-2 day-1 when the slurry surface was liquid and 3.00g H2 S m-2 day-1 when crusted. Emissions however were not significantly different whether the surface was liquid or crusted when differences in temperature were considered. Diurnal variation in emissions was not correlated with air temperature, water vapor saturation deficit, or wind speed when the manure surface was crusted but was positively correlated with these variables when the surface was not crusted. Daily H2 S emissions were modeled according to two-film theory incorporating resistance approach with limited success. Additional emissions measurements with greater documentation of the manure liquid composition and crust characteristics are needed to assess the component transport resistances in the emissions model.

Size and composition of colloidal phosphorus across agricultural soils amended with biochar, manure and biogas slurry

The long-term application of organic amendments like manure, biochar and biogas slurry can increase phosphorus (P) levels in agricultural soils; however, at present, it's not clear how this affects the P association with different mobile water-dispersible colloidal particles (Pcoll). Thus, this study aimed to assess the effects of the long-term application of different organic amendments on the abundance, size and compositional characteristics of Pcoll. For this purpose, a total of 12 soils amended with the above three organic amendments were sampled from the Zhejiang Province, China, and Pcoll were fractionated into nano-sized (NC; 1–20 nm), fine-sized (FC; 20–220 nm), and medium-sized (MC; 220–450 nm) by a combination of differential centrifugation and ultrafiltration steps. These three Pcoll forms together accounted for 74 ± 14% of the total soil solution dissolved P content, indicating that Pcoll release was a key process in the overland P transport from these soils. Soils treated with biochar showed lower Pcoll contents than those treated with manure or slurry alone; this effect should be further explored in a controlled inductive research approach. Compositional analysis showed that inorganic P was the predominant Pcoll form in the NC (54 ± 20%) and FC (63 ± 28%) fractions, but not in the MC (42 ± 26%) fraction. Among the three fractions, the organic carbon (OC)–calcium (Ca) complex was the major carrier of NC-bound Pcoll, MC-bound Pcoll was better correlated with OC–manganese/iron/aluminium colloids than with OC–Ca colloids, and both of these phenomena co-occurred in the FC fraction. The current study provides novel insights into the impact of various carbon amendments on the propensity for P loss associated with different soil mobile colloidal fractions, and will therefore, inform future agronomic and environmental-related policies and studies.

Logistical considerations and challenges in deploying virtual biomethane pipelines to serve on-farm biogas plants

On-farm anaerobic digestion plants served by virtual biomethane pipelines may be used in areas with no gas grid infrastructure access to improve manure (slurry) management and to produce and deliver renewable gas. A modelling analysis of a simulated virtual biomethane pipeline is presented whereby gas is collected from 100 on-farm biogas plants fed with slurry and grass silage feedstocks and delivered to a market entry point (depot). In total, 7 scenarios are presented in the analysis. In scenarios 1–4, the biogas is upgraded on-site by the digester operator, the biomethane is collected by the haulage vehicle(s) and transported to a single depot. The impact of an additional depot on vehicle routing is investigated in scenarios 5 and 6. Scenario 7 investigates the use of a mobile-upgrading and compression unit, which would allow biogas plant operators to forego the installation and operation of biogas upgrading facilities. In scenario 3 (which considers the largest capacity biomethane haulage vehicles and a single delivery depot) all 100 anaerobic digestion plants are visited over the course of one week using 4 routes, with a total aggregated distance travelled of 205 km. Scenario 7 requires a total routing distance in excess of 613 km to visit all 100 biogas plants and requires long routing times and periods of downtime at each site due to the slow upgrading speed of the mobile unit. The weekly greenhouse gas emissions due to vehicle routing from each scenario are calculated. Assuming diesel-fuelled haulage vehicles, scenario 7 routing results in 431 kg CO2-eq week−1, a 167% increase in vehicle route emissions compared to scenario 3 (161 kg CO2-eq week−1). Additionally, whilst the mobile-upgrading unit may alleviate financial challenges, they carry significant logistical challenges, and their resultant higher routing emissions will impact the sustainability of the collected biomethane. Biomethane fuelled haulage vehicles may address this concern if the biomethane is sustainably sourced.

Using the product environmental footprint to strengthen the green market for sustainable feed ingredients; Lessons from a green biomass biorefinery in Denmark

Finding new and sustainable proteinaceous feed ingredients, especially those produced from locally available resources, is at the top of the agenda of many countries, including Denmark, to become feed protein self-sufficient. Protein concentrate (PC) production via the biorefining of green biomass has attracted considerable interest in recent years since they are more land efficient and productive than soybeans. The biorefining of clover-grass into protein concentrate (GPC) is a promising substitute for soybean and soybean meal, however, the environmental impacts of GPC have not been studied. The Product Environmental Footprint (PEF) method, developed by EU Joint Research Centre for the “Single Market for Green Products Initiative” was employed to assess the environmental footprints of organic GPC. The instructions, methodology, and guidelines detailed in Product Environmental Footprint Category Rules (PEFCR) Feed for Food-Producing Animals were followed to implement this PEF study. The results were intended for in-house management, process improvement, early guidance on the environmental footprint (EF) of compound feeds containing GPC, and the EF of livestock and animal production whose feed ration contains GPC. Our results showed that GPC would have a climate change impact of 1091.47 kg CO2,eq/t GPC. We found that farming/cultivation, more specifically direct emissions from manure slurry, dominated most impact categories, including acidification and eutrophication. The results were found sensitive to the choice of allocation method and very case-specific. For instance, the climate change impact of GPC was higher under economic allocation than direct substation, but the acidification impact was lower in economic allocation than direct substitution. However, the direct substitution method, showed that treating the process residues in biogas plants could result in GPC with lower EFs. The sensitivity analysis confirmed that increasing the clover-grass productivity and decreasing either manure slurry application or nitrogenous emissions from its application are the keys to further decreasing the overall environmental impacts.

Promoting the Circular Economy on an Island: Anaerobic Co-Digestion of Local Organic Substrates as a Possible Renewable Energy Source

The local waste co-digestion is an interesting option to tackle in reduced and isolated areas like the islands. The islands have limited territory and scarce fuel production. Moreover, organic waste can create serious environmental problems in soil, water and air. Anaerobic co-digestion (AcoD) is a technology fulfilling the concept of waste-to-energy (WtE) based on local resources. The valorisation of organic waste through AcoD on an island would prevent environmental impacts, while being a source of renewable energy. In this study, cow manure (outdoor and indoor), pig slurry, bird manure, kitchen waste, sewage sludge and oily lacteous waste produced on Island Terceira (Portugal) were tested in mesophilic -35 °C- Biochemical Methane Potential (BMP) co-digestion assays. The goals were to analyse the recalcitrant and high potential produced waste and to estimate the energetic supply source on the island. The cow manure and pig slurry were used as inocula and specific methanogenic activities (SMAs) were carried out. The results showed that both substrates have a significant methanogenic activity-SMA 0.11 g-COD/(g-VSS.d) and 0.085 g-COD/(g-VSS.d), respectively. All the studied combinations were feasible in AcoD, showing TS removals in the range of 19-37%; COD removals in the range 67-78% and specific methane yields from 0.14 to 0.22 L/gCOD removed, but some differences were found. The modified Gompertz model fitted the AcoD assays (R2 0.982-0.998). The maximum biogas production rate, Rmax. was highest in the AcoD of Cow+Pig+Oily and in the Cow+Pig+Sludge with 0.017 and 0.014 L/g-VSadded.day, respectively, and the lowest in Cow+Pig+Bird with 0.010 L/g-VSadded. In our AcoD studies, the bird manure limited the performance of the process, since it was recalcitrant to anaerobic degradation. On the other hand, the oily lacteous waste showed a great potential in the anaerobic digestion. The estimated biogas production, from the best-studied condition, could cover the 11.4% of the energy supply of the inhabitants. These preliminary results would prevent the environmental impact of organic waste on the island and promote the use of local waste in a circular economy scenario.

Acidification of slurry to reduce ammonia and methane emissions: Deployment of a retrofittable system in fattening pig barns

Livestock farming, and in particular slurry management, is a major contributor to ammonia (NH3) and methane (CH4) emissions in Europe. Furthermore, reduced NH3 and CH4 emissions are also relevant in licensing procedures and the management of livestock buildings. Therefore, the aim is to keep emissions from the barn as low as possible. Acidification of slurry in the barn can reduce these environmental and climate-relevant emissions by a pH value of 5.5. In this study, an acidification technology was retrofitted in an existing fattening pig barn equipped with a partially slatted floor. The slurry in a compartment with 32 animals was acidified. An identical compartment was used for reference investigations (case-control approach). Several times a week slurry was pumped for acidification in a process tank outside the barn compartment in a central corridor, where sulphuric acid (H2SO4) was added. Then the slurry was pumped back into the barn. In contrast to other systems, where acidified slurry was stored mainly in external storage tanks, in this study the slurry was completely stored in the slurry channels under the slatted floor, during the entire fattening period. The emission mass flow of NH3 and CH4 was measured continuously over three fattening periods, with one period in spring and two periods in summer. On average 17.1 kg H2SO4 (96%) (m³ slurry)−1 were used for acidification during the three fattening periods. NH3 and CH4 emissions were reduced by 39 and 67%, respectively. The hydrogen sulphide (H2S) concentration in the barn air of the acidification compartment was harmlessly low (0.02 ppm). Thus, despite the storage of the acidified slurry in the barn, the system leads to a lower concentration of detrimental gases, which is beneficial for the animals' as well as for the workers’ health. The study shows that it is possible to retrofit acidification technology into existing pig barns. Further investigations shall identify possible measures to reduce the amount of H2SO4 used and thus minimise the sulphur input into the slurry.

Stable C and N isotope variation during anaerobic digestate composting and in the compost-amended soil-plant system

Although the use of composts derived from anaerobic digestates as soil amendments is likely to increase in the future, there is little information concerning the fate of their C and N compounds after their incorporation into soil. This work assesses C and N concentrations and the associated changes in δ15N and δ13C during the composting processes of cattle and pig slurry anaerobic digestates. In addition, the compost effect on C and N fractions and plant uptake were studied during a six-month pot experiment with rosemary plants. The results did not show δ13C and δ15N isotopic discrimination during composting, indicating a previous stabilization of cattle manure and pig slurry during the anaerobic digestion. This fact was also confirmed by the low C losses during the composting processes (1.2-fold and 1.05-fold for the composting piles with cattle and pig slurry anaerobic digestates, respectively). After soil addition, the composts augmented N values (from 0.41 g kg−1 to around 0.56 g kg−1 in low dose and 0.68 g kg−1 in high dose compost amended soils) and δ15N soil values (increases in the range of 50%–156%), but showed only slight differences in C and δ13C values compared to unfertilised control and inorganic fertilized soils. Moreover, the rosemary leaves of the plants grown on the compost amended soils presented higher N and δ15N abundance than control and inorganic fertilized plants. We conclude that δ15N abundance of anaerobic digestate composts is useful to discern its N uptake and could thus be a useful tool to detect whether organic or mineral fertiliser types were used for agricultural production.

N2O emission factors for organic amendments in Japan from measurement campaign and systematic review

Organic amendments are important sources of nitrous oxide (N2O) emissions from agricultural soils. In 2020, the total amount of N in organic amendments applied to Japanese agricultural soils (440 ktN) was larger than that of synthetic fertilizer (374 ktN). However, N2O emissions from organic amendments were estimated by using the country-specific N2O emission factor (EF) for synthetic fertilizer (0.31 % for rice paddy, 2.9 % for tea, and 0.62 % for other crops) in the National Greenhouse Gas Inventory Report of Japan. Thus, we conducted a N2O flux measurement campaign at 12 different experimental sites across Japan to estimate fertilizer-induced N2O EFs for major organic amendments in Japan, that is, poultry manure compost, swine manure compost, cattle manure compost, and organic fertilizer pellets. In addition, we conducted systematic review of N2O emissions and EFs for organic amendments, including data from our measurement campaign and published data from peer-reviewed papers in Japan. The final dataset, including the field measurement campaign and published data, resulted in 404 observations (including synthetic fertilizer and zero-N control) in 29 sites. Results showed that soil type affected EFs, that is, the mean EF of Andosols was lower than that of non-Andosols, which is similar to the case of EFs for synthetic fertilizer. Mean EFs for poultry manure compost, swine manure compost, cattle manure (compost and slurry), and non-animal manure organic fertilizers were 0.83 % (uncertainty range of 2.5th and 97.5th percentile: 0.09 % to 3.46 %), 0.70 % (0.02 % to 2.45 %), 0.39 % (0.00 % to 1.62 %), and 1.16 % (0.41 % to 3.03 %), respectively, when weighted by area of soil types. The mean EF of all organic amendments was 0.84 % (0.00 % to 2.91 %), when the area of soil type and amount of organic amendment used in Japan were considered. Our study provides country-specific EFs to estimate N2O emission from organic amendments in Japan.

Development of an improved solids-liquid separation reactor for floatable & settleable solids in DAF slurry of a slaughterhouse

The dissolved air flotation (DAF) is used widely for wastewater treatment as a primary treatment unit to remove suspended solids (SS) and oil & grease (O & G). However, the less studied part is the management of concentrated slurry from the DAF operation that exhibit both settling and floating nature. It is a common practise so far to further dewater the DAF slurry by decanting centrifuge. This study addresses the problems of dewatering the DAF slurry by developing a simple yet novel solid-liquid separation unit on a pilot scale and its implementation on a full-scale. The DAF slurry (SS:9100 ± 830 mg/L) contained settled and floating or suspended solids (SS) layers of 125 ± 9 and 130 ± 11 mL/L, respectively, and a distinct clear water zone of 744 ± 16 mL/L sandwiched between two. The solid-liquid separation was achieved using two reactors in series. In the first reactor, the settleable solids are separated and the overflow containing floatable suspended solids are taken to the second unit and clear water was recovered from the bottom of the reactor. The SS removal efficiency was ~95 % and the volume reduction of sluryy was 70 % at an overall hydraulic retention time (HRT) of 2 h. The rest of the thickened slurry has SS concentration of 32,174 to 33,866 mg/L indicating effective thickening. As a result of volume reduction, the operation time of decanting centrifuge was also reduced by 70 % and hence a total power saving of 77 to 117 kW/day (for slurry volume of 10 to 15 m3/day).

Optimizing the conditions of anaerobic fermentation in pig manure to produce volatile fatty acids and its efficiency in killing root-knot nematodes

To concurrently control root-knot nematodes and treat pig manure and further clarify the mechanism of anaerobic digestion slurries on nematodes, the optimal conditions for producing volatile fatty acids (VFAs) were studied, and the relationship between the carboxyl group in anaerobic fermentation and the mortality rate of root-knot nematodes was also researched. When the fermentation condition parameters were set as initial pH=10.0, temperature of 25 °C, and total solid (TS) loading of 15%, the largest quantity of VFA production was obtained through orthogonal experiments and range analyses. When the concentration of VFA in the anaerobic fermentation slurry was enhanced to 3.2 g/L, the rate of root-knot nematode mortality was up to 43.3% and was significantly different from that of the control. However, after the concentration of VFA reached 4.3 g/L, no significant difference was observed for the treatments with even higher concentrations of VFA. This indicated that the pig manure slurry with anaerobic digestion exhibited a limited range to kill root-knot nematodes. The results of this study provide a theoretical basis for producing acid from anaerobic digestion in pig manure and for slurry applications.