Solid Pig Manure Research Articles

Can black soldier fly larvae (Hermetia illucens) be reared on waste streams for food and feed? – A safety perspective

Abstract The use of insects as feed and food can be part of the solution towards a circular economy, in case the safety of insect products is assured. Black soldier fly larvae (BSFL, Hermetia illucens) can be reared on different waste streams. However, before BSFL can be legally reared on these streams, the safety of BSFL for feed and food should be assessed thoroughly. This study aimed to investigate several food safety aspects of BSFL grown on waste streams. Therefore, BSFL were reared for 7 days on substrate mixtures of waste streams with similar protein and moisture content. These waste streams included fast food waste (FF), mushroom stem (MS), pig manure solids (PS), poultry meal (PM) and slaughter waste (SW). The substrates, BSFL and the frass were analysed for the presence of metals and veterinary drugs. The substrates and BSFL were also analysed for presence of DNA of ruminant, pig and chicken. Some of the metals accumulated in BSFL, although the concentrations in BSFL (as these would be manufactured as feed) were below maximum limits for feed. Only traces of some of the analysed veterinary drugs were found in the BFSL and no accumulation thereof was observed. DNA of ruminant and pig was traced back in BSFL samples, however, chicken was not. A good understanding of the presence of food safety hazards and possible variance thereof in potential substrates, such as waste streams, and their possible residues in insects is necessary for implementation of this circular way of insect feeding in the food chain.

Safety of black soldier fly (Hermetia illucens) larvae reared on waste streams of animal and vegetal origin and manure

Abstract In Europe, commercial and scientific interest in black soldier fly larvae (BSFL, Hermetia illucens) as a new feed source has grown substantially, primarily because this species can be reared on waste-streams which are otherwise unsuitable. However, before BSFL may legally be reared on such materials, and subsequently fed to livestock animals, safety must be guaranteed. Many hazards could be relevant, depending on the origin of the waste stream. Small- and large-scale experiments were performed in which BSFL were reared on the organic wet fraction of municipal household waste (OWF), kitchen/fast food waste (FFW), mushroom feet stems (MF), pig manure liquid slurry mixed with roadside silage grass (PMLSG), pig manure solids (PMS), and secondary sludge from slaughter waste (SW). Larval yields were highest on the control (chicken feed + water) and the FFW. Substrates and larvae were analysed to determine the presence of heavy metals, acrylamide, pesticides, veterinary drugs, and pathogenic bacteria. Cadmium (Cd) bioaccumulated in larvae reared on all substrates, in line with previous research. Some pesticides and veterinary drugs were found in the substrates: concentrations in the larvae were low, but potential formation of metabolites could be studied further. Acrylamide was present in the FFW, but not in the larvae reared on it: more research is needed to determine the (metabolic) fate. Bacillus cereus and traces of Salmonella spp. were found on some larval samples, but appropriate processing is anticipated to minimize potential risks. Based on these results, we conclude that most tested substrates are suitable for rearing BSFL, and do not appear to present major safety concerns, aside from the need for monitoring Cd concentrations in the substrates, and control measures for pathogenic bacteria. Further verification to account for variance in contamination of substrates is needed for definitive conclusions on the safety.

Can crop yields be secured while reducing phosphorus accumulation in soil? Assessing decades of contrasting fertilizer strategies.

ContextA balanced phosphorus (P) use in agriculture, where P fertilizer input matches crop offtake, is necessary to avoid accumulation of P in soil that is a chronic source for diffuse P loss. Moreover, mineral P fertilizers produced from rock phosphate is a limited resource, and identification of alternative P fertilizer sources such as animal manures that secure yields without P surpluses is therefore essential for sustainable P use. ObjectiveThe objective was to explore crop productivity and soil P accumulation after long-term input of different P fertilizer sources. Moreover, Olsen-P contents in soil were determined to evaluate if crop yields and P balances were reflected in measures of available P. MethodsOn a coarse sandy soil installed in lysimeters under field conditions, crop yields and P surpluses from 1992 to 2022 were quantified as affected by P fertilizer source (annual additions of solid pig manure, pig slurry and mineral fertilizer) since 1975. All lysimeters received mineral nitrogen (N) fertilizers according to the crop demand. Olsen-P contents in the upper soil layer (0–25 cm) were measured over three decades, and vertical distribution of P in soil down to 140 cm depth was studied at the end of the experimental period. ResultsFor oats, barley, pea and beet root, long-term fertilization with solid pig manure at a rate of 15 kg P ha-1 year-1 resulted in similar yields as after fertilization with 30 kg mineral P ha-1 year-1. After 30 years, the build-up of P in soil was much lower after solid pig manure inputs (accumulation of 8 kg P ha-1) than after mineral P fertilization (accumulation of 51 and 434 kg P ha-1 in soil receiving 15 and 30 kg mineral P ha-1 year-1, respectively). The long-term fertilizer treatments affected Olsen-P levels in the upper soil layer with highest Olsen-P contents (>40 mg P kg-1) after fertilization with 30 kg mineral P ha-1 year-1. Only maize benefitted from high Olsen-P levels and generous input of mineral P, whereas the yield potential for the other crop types could be reached at low to moderate Olsen-P levels after long-term additions of solid pig manure. More P was found in the deep soil layers (65–140 cm) after addition of pig slurry than solid pig manure. ConclusionsThe results showed that solid pig manure was a valuable P source that had the potential to replace mineral P fertilizers without compromising crop productivity, while ensuring low P surpluses. ImplicationsThis study suggests that the Olsen-P test could not stand alone in predicting P requirement but should preferably be supplemented with knowledge on fertilizer source, crop type and P offtakes to ensure a more balanced fertilizer P use.

Weed community dynamics under repeated fertilization with different nutrient sources over 5 years

Soil fertility management through the application of synthetic fertilizer or livestock manures is crucial to maintaining the productivity and profitability of cropping systems. Little, however, is known about the response of weed communities to different livestock manure nutrient sources. As weed communities with increased diversity are considered part of more sustainable agroecosystems, it is necessary to find management practices that result in diverse weed communities of acceptable densities without negative impacts on crop productivity. Here, we monitored the effect of five nutrient sources, with similar goals for nitrogen (N) management, including synthetic fertilizer, liquid pig manure, two types of solid pig manure, and solid dairy manure on the weed community in a five-year (2008-2012) study. The abundance, species richness, Simpson’s diversity, Simpson’s evenness, and species turnover in weed communities were assessed over time. Crop biomass, mid-season plant-accessible soil nitrate-N, and pre-season soil phosphorus were determined. The application of liquid pig manure or synthetic fertilizer enhanced crop biomass likely through increased crop accessibility to N. The continued use of these sources of nutrients over time, contributed to low density, low species richness, and low diversity weed communities, particularly through the decline of broadleaf weed species. Liquid pig manure and synthetic fertilizer treatments were lower in weed density and diversity than solid manures. Solid manure treatments were associated with increased weed densities and reduced crop biomass; however, these nutrient source treatments resulted in more diverse weed communities. Regardless of the nutrient treatments, we observed drastic declines in weed community abundance, species richness, and diversity in drier years. Our study suggests that a management practice that increases the accessibility of N to the crop, possibly through a mixture of solid manures and synthetic fertilizers or liquid pig manure, may be ideal for promoting a profitable cropping system with decreased densities and improved diversity in weed communities. Technological advances that provide more precise placement of solid manures to increase the accessibility of N to the crop, may further contribute to achieving such profitable and multifunctional agroecosystems.

Anaerobic Digestion of Pig-Manure Solids at Low Temperatures: Start-Up Strategies and Effects of Mode of Operation, Adapted Inoculum, and Bedding Material.

The objective of this study was to obtain start-up strategies for the operation of a dry anaerobic digestion (DAD) system treating pig-manure (PM) solids at low-temperatures, and evaluate the effects of operation mode, adapted inoculum, and bedding material on the performance. A DAD system coupled with an inoculum system (two-stage DAD) was operated at 20 ± 1 °C to digest PM solids (Total Solids, TS: 27%) with wheat straw or woodchips as bedding materials (TS substrate-mixture: 45%) using a liquid inoculum. Static DAD was also operated in parallel for comparison purposes. Overall, the percolation–recirculation mode of operation was superior to the static mode; the former had more than a 3-fold increase in specific methane yield in cycle 3. Using the adapted inoculum in cycle-2 improved methane yield by 7% and 26% for cycles 1 and 3, respectively, under the percolation–recirculation mode of operation. In addition, the digestate resulting from the digestion of woodchips + PM solids had better physical characteristics than wheat straw + PM solids. Thus, anaerobic digestion of pig-manure solids at low-temperatures with appropriate start-up strategies, inoculum, and bedding material is a promising technology for transforming PM solids into biogas and using its digestate as biofertilizer.

Biological acidification of pig manure using banana peel waste to improve the dissolution of particulate phosphorus: A critical step for maximum phosphorus recovery as struvite

Traditional disposal of agricultural bio-waste such as pig manure and banana peel waste poses an environmental nuisance. The uncontrolled disintegration of these waste materials decomposes to toxic effluent and methane a greenhouse gas twenty-one times more potent than carbon dioxide at trapping heat in the atmosphere, which is detrimental to the climate by elevating temperatures. Agricultural bio-waste is rich in nutrients that include nitrogen and phosphorus. Selectively separating these nutrients from the solid phase to produce high value products has been envisaged as an effective method of waste valorisation. This study aims to investigate the solubilisation of phosphorus (P) during anaerobic digestion (AD) of pig manure with banana peel waste as the co-substrate. The objective was to enhance the biological dissolution of the phosphorus from solid pig manure to the aqueous phase as this is envisaged to subsequently ease the recovery of P as a concentrated product via crystallization. Thereafter, phosphorus is used as a slow-release mineral fertilizer. Biological acidification was effective in reducing the pH to less than 6.50 from an initial pH of 7.28 at higher doses of BPW >100 g/L. Maximum dissolution of total phosphorus of 75% was observed at a pH of 5.40. Multiple regression analysis was used to correlate pH, banana peel waste concentration, and the anaerobic digestion time (ADT) to optimize the dissolution of P as this was deduced to be occurring at a low pH. A 2nd order polynomial was deduced to best fit the data with an R2 value of 0.90. The p values for the HRT and banana peel waste concentration were both <0.05 showing that both variables had a strong influence on the pH.

Soil nitrous oxide emissions associated with conversion of forage grass to annual crop receiving annual application of pig manure

The disruptive land-use change during forage grass conversion to annual crop can be critical for determining nitrous oxide (N2O) emissions, but this is an understudied period. We measured soil N2O fluxes (using closed static vented chambers) together with potential environmental drivers of these fluxes from liquid pig manure (LPM) and solid pig manure (SPM) applied to an annual crop (ANN) and perennial forages (FPP) that was converted to annual crop. Unamended plots were used as a control (CON). The results showed that in 2013, average soil nitrate-N was significantly higher on the recently converted FPP (ranging from 19 to 83 mg N kg−1) than the continuous ANN plots (from 16 to 35 mg N kg−1). The recently converted perennial forage system produced three times greater N2O than the continuous annual system, which is likely a result of accelerated N mineralization from the accumulated soil organic matter (over 4 yr) and grass residues of the recently killed forage grasses. However, during the second year of the study when the FPP plots were reseeded to perennial grasses, the system emitted 30% less N2O than the ANN system. These results suggest that including perennial forage grass in rotation with annual crops can provide N-saving and climate change mitigation benefits; however, some of the N stored in the soil would be lost when the perennial grass plots are cultivated to grow annual crops.

A major pathway for carbon and nitrogen losses — Gas emissions during storage of solid pig manure in China

This study investigated the carbon (C) and nitrogen (N) gas emissions (N2O, NH3, CO2 and CH4) from solid pig manure management in China. Gas emissions were quantified from static piles over 60 days during summer in China's Yangtze River Basin, using Drager-Tube and static chamber-gas chromatography techniques. High emissions of NH3 and N2O were observed at the early stage of storage, but high emission of CH4 occured later during storage. Overall, 62% of the total C in the original pile was lost; CO2 and CH4 emissions accounted for 57 and 0.2% of C lost respectively. Over the same time, 41% of the total N in the original pile was lost; NH3 and N2O emissions accounted for 15 and 0.3% of N lost respectively. The volatilization of NH3 during storage in summer was 4.56 g NH3 per kg dry weight. The total greenhouse gas (GHG) emissions during storage accounted for 67.93 g CO2 equivalent per kg dry weight; N2O and CH4 contributed to 46 and 55% of total GHG emissions respectively. Given China's major role in pig production, further attention should given to pig manure management to mitigate its contribution to atmospheric pollution.

Below-ground plant biomass and nitrogen uptake of perennial forage grasses and annual crops fertilized with pig manures

The aim of this study was to determine the importance of below-ground (root) plant biomass and nitrogen (N) uptake with perennial cropping system (PCS) as a mechanism of reducing nitrate leaching. The experimental design was a split plot with main plot being cropping system [annual cropping system (ACS) versus PCS] and subplots being manure treatment [N-based liquid pig manure (LPM), N-based solid pig manure (SPM), and a control with no manure addition (CON)]. The ACS was seeded to barley (Hurdeum vulgare L.) and canola (Brassica napus L.) in the spring of 2014 and 2015, respectively, whereas the PCS was seeded to a mixture of timothy (Phleum protense L.) and orchard (Dactylis glomerata L.) grass in the fall of 2013. LPM and SPM were applied to meet N requirement of each crop in spring of each year. In 2014, above-ground and root biomass were collected at harvest and in 2015, above-ground and root biomass were collected at mid-season. The PCS had significantly greater root biomass and N uptake than ACS in both years. Root biomass in PCS ranged from 5.3–9.7 Mg ha−1 compared to a range of 1.1–1.5 Mg ha−1 in ACS. Consequently, root N uptake in PCS ranged from 43 to 118 kg N ha−1 in both years while that in ACS was 9–20 kg N ha−1. In 2014, PCS had significantly greater above-ground N than ACS, whereas in 2015, PCS had significantly greater above-ground N than ACS in the LPM only. This study shows that the differences in nitrate leaching between the two cropping systems as previously determined from field core lysimeters at the same plots was mainly due to differences in root N uptake (34–98 kg N ha−1) between the cropping systems rather than above-ground N uptake. It is important that studies comparing N losses by ACS and PCS should consider the role of plant root biomass in N recovery.

Nitrogen- or phosphorus-based pig manure application rates affect soil test phosphorus and phosphorus loss risk

Pig manure is an effective source of plant nutrients that must be properly managed to prevent these nutrients from reaching surface and ground water. We conducted a 3-year study in southern Manitoba to investigate how the choice of cropping system and manure management practices affect soil test phosphorus (STP) concentration and loss of phosphorus (P) to groundwater. The experiment had a split-plot design with two cropping systems (annual and perennial) as main plots, and five nutrient management treatments as subplots: N-based liquid pig manure, P-based liquid pig manure, N-based solid pig manure, P-based solid pig manure and an unfertilized control. We did not measure an appreciable increase in STP concentration below the 0.15 m depth. However, manure application at an N-based rate resulted in increased STP concentration in the 0–0.15 m depth interval. After 3-year, STP concentration in the N-based treatments (48 and 43 mg Olsen P kg−1 for solid and liquid respectively) were significantly greater than for the P-based treatments (26 and 17 mg Olsen P kg−1 for solid and liquid respectively). The mass of P in the leachate was small, ranging from a low of 1 g P ha−1 in 2009 to a high of 100 g P ha−1 in 2011. Both P- and N-based manure application rates produced no apparent risk of P leaching at our site, but the N-based manure application rate increased STP concentration in the surface soil, which could lead to the loss of P in surface runoff.

Nitrogen and phosphorus uptake from solid and liquid pig manure in perennial and annual cropping systems

Applying pig manure in excess of crop demand can result in nutrient loss to water bodies. We studied the effect of liquid and solid pig manures and their N- and P-based application rates on yield and nutrient uptake in annual and perennial cropping systems for 3 yr. The experiment had a split-plot design with five nutrient management treatments including liquid-N (annual N-based liquid pig manure), liquid-P (P-based liquid pig manure once every 5 yr), solid-N (annual N-based solid pig manure), solid-P (P-based solid pig manure once every 5 yr), and control (no manure). The liquid-P treatment showed high apparent nitrogen and phosphorus recovery (ANR and APR, respectively) in each cropping system and yields similar to that of the liquid-N treatment. The solid-N treatment had the smallest ANR in the perennial cropping system (9%–27%) and also the smallest APR in both cropping systems (typically &lt;4%) possibly due to N deficiency and high P application rate. The current formula for estimating organic N mineralization overestimated the available N, particularly for solid pig manure, reducing crop yield. Based on the ANR obtained in this study, a more appropriate coefficient is 10%–15% of the organic N from solid pig manure for no-till perennial cropping systems.

Short-term persistence of ammonium-N following pig manure application is greater with perennial forage grasses than annual crops

A 2-yr study was conducted on a loamy sand soil to compare short-term persistence of ammonium-N in an annual (ACS) and a perennial (PCS) cropping system following pig manures application as a possible explanation for the reduced nitrate leaching from perennial forage grasses. In spring 2014 and 2015, nitrogen-based application rates of liquid (LPM) and solid (SPM) pig manure were broadcast on PCS and ACS plots with incorporation of the manures for ACS plots alone. Following manure applications, soil samples were taken at 0–15 and 15–30 cm depths seven times (2014) and six times (2015) over 2–3 wk period for ammonium-N and nitrate-N concentrations. Ammonium-N (0–15 cm) with LPM peaked 4 d after manure application in ACS (18–29 kg ha−1) and PCS (50–74 kg ha−1) in both years. In both years, persistence of ammonium-N at 7 d was 46%–77% in LPM-amended PCS and 8%–14% in LPM-amended ACS. Ammonium-N measured in SPM-amended ACS and PCS was low after manure application in both years. There was lower accumulation of nitrate-N in PCS than ACS of LPM- and SPM-amended treatments in both years. The greater persistence of ammonium-N in the LPM-amended PCS than ACS coupled with lower percentage increase in nitrate-N in the PCS may account for lower nitrate leaching previously observed for perennial forage grasses at the study location.

Cropping System and Type of Pig Manure Affect Nitrate-Nitrogen Leaching in a Sandy Loam Soil.

The application of livestock manure can result in the loss of nitrate-nitrogen (NO-N) and degrade surface and groundwater. A 3-yr lysimeter study was set up to compare the effect of cropping system and nitrogen (N)- and phosphorus (P)-based pig manure application rates on the loss of water and NO-N below the root zone. The experiment was a split-plot design with annual and perennial cropping systems as the main factor. Five nutrient management treatments were the subplots: N-based liquid pig manure application; P-based liquid pig manure application, N-based solid pig manure application, P-based solid pig manure application, and a control without amendment. The results showed that 40 to 60 kg NO-N ha was lost from the annual plots in 2010 and 23 to 60 kg NO-N ha in 2011, whereas a negligible amount of NO-N was lost from the perennial (<1 kg ha) plots in both years. The application of solid pig manure on a P basis followed by urea in subsequent years reduced the risk of NO-N leaching over the course of the rotation, likely due to immobilization of N by the straw in the solid pig manure. Our study showed that a perennial cropping system consisting of a mixture of grasses has the capacity to receive and utilize significant amounts of nutrients with negligible amount of nutrient leakages to the adjacent environment. The inclusion of grasses in a crop rotation and their use to take up excess nutrients are sustainable practices that will benefit the environment.

Nitrous oxide emissions as affected by liquid and solid pig manures applied to annual and perennial forage crops on a sandy loam soil

Emissions of nitrous oxide (N2O-N) from manure applied to annual crop (AC) and perennial forage (PF) are poorly quantified for the Canadian Prairie Region. This study used static chambers over two growing seasons to assess soil N2O-N emissions from solid pig manure (SPM) and liquid pig manure (LPM) in AC and PF systems on a sandy loam soil. In 2011, when manure application coincided with hot and wet soil conditions, both manure treatments in AC induced N2O-N emission episodes a week later. In the PF, however, only LPM resulted in an N2O-N emission peak after 8 d. In 2012, manure application did not coincide with hot and wet soil conditions, and emission rates were smaller. Overall, the effect of manure type was inconsistent. In 2011, cumulative emissions in AC from LPM and SPM were 5.8 and 7.8 kg N2O-N ha−1, respectively, and in PF were 10.7 and 0.6 kg N2O-N ha−1, respectively. In 2012, cumulative emissions were &lt;1 kg N2O-N ha−1, except LPM in PF. In 2011, LPM had significantly higher emission factor (EF ≍ 7%) than SPM (≤0.2%) in both AC and PF, whereas in 2012 manure type had no effect on EF (≍ 0). Over the two growing seasons and across manure types, EF did not differ between AC and PF. These results suggest that SPM would reduce N2O-N emission relative to LPM when conditions favor intense denitrification.

Bacterial communities of an agricultural soil amended with solid pig and dairy manures, and urea fertilizer

Agricultural management practices impact the bacterial diversity of soil but it is unclear how bacterial communities respond to different nutrient sources. This study examined the impacts of manure and granular urea N additions on the diversity and composition of soil bacterial communities. Bacterial communities in an annual cropping system were examined in the short-term (within season) and medium-term (after three successive annual additions) following manure and urea N applications. Soil samples were collected from an experimental field site in fall 2007 prior to imposition of treatments, and post-planting, mid-season, and post-harvest in 2010 following three successive annual applications. Treatments included: solid pig manure (SPM), solid dairy manure (SDM), granular urea N-fertilizer, and unamended control. Pyrosequencing was used to characterize bacterial communities in soil and the manure added. Psychrobacter was the most abundant genus in both SPM and SDM, however it was not detected in soil. Solid pig manure treatments had greater diversity than urea and control treatments and diversity was greatest at post-harvest in fall than post-planting in spring. In 2010, the relative abundances of many bacterial taxa were affected by treatment and sample season but not their interaction. Where Actinobacteria, Firmicutes, Gemmatimonadetes and Bacteroidetes were significantly different for the urea and manure treatments, Proteobacteria declined in relative abundance over the growing season. Communities of manure and urea treated soils converged with progression of growing season. Redundancy analysis showed SO4−2, NO3− and NH4+ concentrations were significant, explaining 44% of the variation observed in bacterial communities across treatments and sample seasons. In conclusion, bacterial diversity increased with manure treatment and with progression of the growing season, the former being not as a result of introduction of taxa from the manure but likely from nutritional resources provided in the organic amendments.

Physical properties of an Orthic Black Chernozem after 5 years of liquid and solid pig manure application to annual and perennial crops

Pig (Sus scrofa) manure is added to the soil to supply nutrients and improve soil properties. To our knowledge, no direct comparison has been made on the effect of liquid pig manure (LPM) and solid pig manure (SPM) on the physical properties of a prairie soil. This study was established in 2009 at the University of Manitoba’s Ian Morrison Research Station in Carman, Manitoba. The treatment design was a split-plot structure with cropping system as the main plot and manure treatments as subplots. Five years after the study was initiated, soil samples were collected from the 0–10 cm and 10–20 cm depth intervals for determination of bulk density, saturated hydraulic conductivity (Ksat), and water retention at field capacity and permanent wilting point (PWP). For wet aggregate stability, samples were collected from the 0–5 cm layer. Land application of SPM significantly decreased bulk density by 14%, significantly increased Ksatby 110% in the 0–10 cm layer, and resulted in a 30% increase in wet aggregate stability (P &lt; 0.05). In perennial plots, SPM increased water retention at field capacity, PWP, and available water in the 0–10 cm compared with annual plots. This was not the case for LPM-amended soils. We conclude that SPM has the potential as an organic amendment to improve the physical properties of the topsoil.

Spatiotemporal dynamics of phosphorus release, oxygen consumption and greenhouse gas emissions after localised soil amendment with organic fertilisers

Organic fertilisation inevitably leads to heterogeneous distribution of organic matter and nutrients in soil, i.e. due to uneven surface spreading or inhomogeneous incorporation. The resulting localised hotspots of nutrient application will induce various biotic and abiotic nutrient turnover processes and fixation in the residuesphere, giving rise to distinct differences in nutrient availability, soil oxygen content and greenhouse gas (GHG) production. In this study we investigated the spatiotemporal dynamics of the reaction of manure solids and manure solids char with soil, focusing on their phosphorus (P) availability, as current emphasis on improving societal P efficiency through recycling waste or bio-based fertilisers necessitates a sound understanding of their behaviour. Soil layers amended at a constant P application rate with either pig manure solids or char made from pig manure solids were incubated for three weeks between layers of non-amended, P-depleted soil. Spatial and temporal changes in and around the amendment layers were simultaneously investigated in this study using a sandwich sensor consisting of a planar oxygen optode and multi-element diffusive gradients in thin films (DGT) gels, combined with GHG emission measurements. After three weeks of incubation, the soil containing a layer amended with manure solids had a lower overall O2 content and had emitted significantly more CO2 than the non-amended control or the char-amended soil. The P availability from manure solids was initially higher than that from the char, but decreased over time, whereas from the char-amended layer P availability increased in the same period. In both treatments, increases in P availability were confined to the amended soil layer and did not greatly affect P availability in the directly adjacent soil layers during the three-week incubation. These results highlight the importance of placing organic P fertilisers close to where the plant roots will grow in order to facilitate optimal fertiliser use efficiency.

Phosphorus recovery from pig manure solids prior to land application

Land disposal of pig manure is an environmental concern due to an imbalance of the nitrogen to phosphorus (N:P) ratio for crop production, leading to excess phosphorus (P) in soils and potential risks of water pollution. A process called “quick wash” was investigated for its feasibility to extract and recover P from pig manure solids. This process consists of selective dissolution of P from solid manure into a liquid extract using mineral or organic acid solutions, and recovery of P from the liquid extract by adding lime and an organic polymer to form a P precipitate. Laboratory tests confirmed the quick wash process selectively removed and recovered up to 90% of the total (TP) from fresh pig manure solids while leaving significant amounts of nitrogen (N) in the washed manure residue. As a result of manure P extraction, the washed solid residue became environmentally safer for land application with a more balanced N:P ratio for crop production. The recovered P can be recycled and used as fertilizer for crop production while minimizing manure P losses into the environment.

Determination of the Higher Heating Value of Pig Manure

The ability of using novel method of near-infrared (NIR) spectra to predict the composition and higher heating value (HHV) of dry pig manure was examined. Number of pig manure solid fractions variously pre-treated samples were collected in Denmark, from different pig slurry treatment plants (using mechanical or chemical–mechanical separation) and then analysed for their energy values. These values were determined by conventional method using bomb calorimetry and also calculated based on ultimate analysis. NIR spectra method was successfully applied and reasonable R2 values were obtained for the independent prediction set for nitrogen, ash, and the HHV. NIR also showed ability for predicting which type of treatment plants the samples came from. In addition, new empirical equations, based on ultimate analyses of pig manure solids used for prediction of the HHV was established.

톱밥 및 왕겨 혼합조건이 돈분 퇴비화에 미치는 영향

본 연구에서는 돈분퇴비 제조 시 톱밥소요량을 줄이는 방안을 모색하고자 왕겨의 혼용 효과를 분석하였다. 실험기간 35일 동안 퇴비의 평균 온도는 PM+SD5+RH10 와 PM+SD10+RH5 처리구가 가장 높게 유지되었다. 모든 처리구의 유기물함량 및 OM/N ratio는 시험을 종료한 5주차에서 비료공정규격의 범위를 만족하였다. 퇴비의 중량 감소율은 PIM+SD10+RH5와 PIM+SD5+RH10 처리에서 각각 36.7%와 36.4%로 타 처리에 비해 가장 높았다. 따라서 퇴비의 온도상승과 더불어 무게 감소율을 종합해 볼 때 대조구(PIM+SD15 처리) 대비 PIM+SD10+RH5와 PIM+SD5+RH10처리에서 왕겨를 활용함으로써 톱밥사용량의 약 30-65% 대체가 가능한 것으로 판단된다. A bulking agent is an essential material for composting of high-moisture livestock manure such as pig slurry. Sawdust has been used as the most popular bulking agent but resources are limited in Korea. In this study, the feasibility of rice hull as a bulking agent was examined for composting of solid pig manure. The solid pig manure was mixed with 15% sawdust (PM+SD15), 15% rice hull (PM+RH15), 10% sawdust and 5% rice hull (PM+SD10+RH5), and 5% sawdust and 10% rice hull (PM+SD5+RH10) based on fresh weight. These mixtures were composted for 35 days. The average temperature of the composting file for 35 days was higher in PM+SD10+RH5 and PM+SD5+RH10 than in PM+SD15 and PM+RH15. The mass loss of PM+SD10+RH5 and PM+SD5+RH10 were 36.7 and 36.4%, respectively, which were higher than that of PM+SD15 and PM+RH15. After composting, organic matter content and organic matter/nitrogen ratio in all treatments met the official standards of commercial fertilizers. We concluded that rice hull may be a good bulking agent for pig manure composting when it is used in mixture with sawdust.