Pelletization of composted swine manure solid fraction with different organic co-formulates: effect of pellet physical properties on rotating spreader distribution patterns

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Gaseous Emissions after Soil Application of Pellet Made from Composted Pig Slurry Solid Fraction: Effect of Application Method and Pellet Diameter

The study aimed at determining ammonia and GHG emissions from soil fertilized with pellets made from composted pig slurry solid fraction and to evaluate the effects of pellet diameter and pellet application method on gaseous emissions. A laboratory scale experiment was carried out investigating two composts: pig slurry solid fraction compost (SSFC) and pig slurry solid fraction mixed with wood chips compost (WCC). The two composts were pelettized in two different diameters—6 and 8 mm—by means of mechanical pelletizer. In total, eight fertilized treatments plus one unfertilized control were included in the experiment. The investigated pellets were applied at the same nitrogen rate (equivalent to 200 kg ha−1) using two different methods (on soil surface and incorporated into the soil). Ammonia (NH3) emission was monitored immediately after pellet application, while nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) were measured on a 57-day incubation period. As expected, ammonia volatilization was not detected from any of the treatments investigated. At the end of the experiment, the cumulative amounts of N2O, CO2 and CH4 ranged from 2.70 mg N-N2O m−2 to 24.30 mg N-N2O m−2, from 601.89 mg C-CO2 m−2 to 1170.34 mg C-CO2 m−2 and from 1.22 mg C-CH4 m−2 to 1.31 mg C-CH4 m−2, respectively. The overall results of the investigation highlighted that application on the soil surface reduced nitrous oxide emission, while the carbon dioxide emission increased significantly with smaller pellet diameter

Energy and pressure requirements for compression of swine solid fraction compost

The excessive amount of pig slurry spread on soil has contributed to nitrate water pollution both in surface and in ground waters, especially in areas classified as vulnerable zones to nitrate in accordance with European Regulation (91/676/CEE). Several techniques have been developed to manage livestock slurries as cheaply and conveniently as possible and to reduce potential risks of environmental pollution. Among these techniques, solid-liquid separation of slurry is a common practice in Italy. The liquid fraction can be used for irrigation and the solid fraction, after aerobic stabilization, produces an organic compost rich in humic substances. However, compost derived from swine solid fraction is a low density material (bulk density less than 500 kgm–3). This makes it costly to transport composted swine solid fraction from production sites to areas where it could be effectively utilized for value-added applications such as in soil fertilization. Densification is one possible way to enhance the storage and transportation of the compost. This study therefore investigates the effect of pressure (20- 110 MPa) and pressure application time (5-120 s) on the compaction characteristics of compost derived from swine solid fraction. Two different types of material have been used: composted swine solid fraction derived from mechanical separation and compost obtained by mixing the first material with wood chips. Results obtained showed that both the pressure applied and the pressure application time significantly affect the density of the compacted samples; while the specific compression energy is significantly affected only by the pressure. Best predictor equations were developed to predict compact density and the specific compression energy required by the densification process. The specific compression energy values based on the results from this study (6-32 kJkg–1) were significantly lower than the specific energy required to manufacture pellets from biomass feedstock (typically 19-90 kJkg–1)

Energy and pressure requirements for compression of swine solid fraction compost

The excessive amount of pig slurry spread on soil has contributed to nitrate water pollution both in surface and in ground waters, especially in areas classified as vulnerable zones to nitrate in accordance with European Regulation (91/676/CEE). Several techniques have been developed to manage livestock slurries as cheaply and conveniently as possible and to reduce potential risks of environmental pollution. Among these techniques, solid-liquid separation of slurry is a common practice in Italy. The liquid fraction can be used for irrigation and the solid fraction, after aerobic stabilization, produces an organic compost rich in humic substances. However, compost derived from swine solid fraction is a low density material (bulk density less than 500 kgm–3). This makes it costly to transport composted swine solid fraction from production sites to areas where it could be effectively utilized for value-added applications such as in soil fertilization. Densification is one possible way to enhance the storage and transportation of the compost. This study therefore investigates the effect of pressure (20- 110 MPa) and pressure application time (5-120 s) on the compaction characteristics of compost derived from swine solid fraction. Two different types of material have been used: composted swine solid fraction derived from mechanical separation and compost obtained by mixing the first material with wood chips. Results obtained showed that both the pressure applied and the pressure application time significantly affect the density of the compacted samples; while the specific compression energy is significantly affected only by the pressure. Best predictor equations were developed to predict compact density and the specific compression energy required by the densification process. The specific compression energy values based on the results from this study (6-32 kJkg–1) were significantly lower than the specific energy required to manufacture pellets from biomass feedstock (typically 19-90 kJkg–1)

Recycling Pig Slurry Solid Fraction Compost as a Sound Absorber

The aim of this investigation was to determine the physical and acoustical properties of compacts made from composted pig slurry solid fraction (SF) in order to assess the potential to recycle this agricultural waste as a sound absorber. The compacts were obtained by compression. The physical parameters investigated were bulk density, durability, and particle size distribution. The acoustical features of the compacts were studied with an impedance tube device in order to verify the acoustic absorption coefficient. Two composts were prepared: pig SF compost without a bulking agent (SSFC) and pig SF compost with wood chips as a bulking agent (WCC). The study’s results indicated that compost particles dimension played a key role in the physical and acoustical properties of the compacts: the smaller the particles, the higher the physical and acoustical properties of the compacts. The densification process increased the bulk density of the investigated composts up to 690 kg m−3 for SSFC and 660 kg m−3 for WWC, with, respectively, medium (77.9%) and low (66.5%) durability. The addition of woody bulking agent significantly reduced the absorption coefficient: the best results, in terms of potential use as a sound absorber, were observed for compacts made from composted pig slurry solid fraction without the addition of wood chips

Farmers’ Attitudes toward On-Farm Adoption of Soil Organic Matter in Piedmont Region, Italy

This study aimed at exploring the frequency of use and perceived benefits of application of organic matter to the soil in a group of Italian farmers, investigating also the preferred sources of information, to identify potential interventions to promote the improvement of the soil organic matter. The study has been carried out administering a 21-item paper-and-pencil questionnaire to 44 farmers. The results of the study highlighted that the main perceived benefit linked to soil organic matter application is related to its capacity of increasing productivity, while the aspects related to work pace, production costs, and implications with the climate change appeared to be less relevant. According to the results of the study, web targeted information campaigns for the smaller farms operators and training activities for the bigger farms operators are the most effective solutions to make farmers aware of the importance of increasing soil organic matter content

Reuse of Animal Manure: A Case Study on Stakeholders’ Perceptions about Pelletized Compost in Northwestern Italy

The present study aimed at investigating perceptions and preferences about the use and the chemical characteristics of pellets made from composted animal manure in a sample of Italian farmers and agricultural advisors (Piedmont region, Northwestern Italy). The study encompassed two different steps: At first, the participants were administered a questionnaire about their actual use of pellets and preferences about their chemical characteristics. Then, a subgroup participated into a hands-on experience with different pelletized animal manures and some final questions. Concerning the use of pellets made from composted animal manure, even if the participants affirmed to be interested in using organic pellets and declared to own the appropriate equipment needed for their application, the results indicated that pelletized compost utilization had not yet become a common practice for agricultural crops. The obtained results highlighted a lack of knowledge, especially among farmers, about the importance of some chemical properties of this pelletized organic material. The participants, both farmers and advisors, were particularly attracted by the total nitrogen content of organic pelletized fertilizers, probably because the supplying of nutrients, nitrogen particularly, is the function of fertilizers they were interested in the most due to its direct connection with crop production. The hands-on session allowed the participants to better understand the benefits of the principal chemical properties—organic matter and carbon to nitrogen ratio—of pelletized animal manure compost. On the other hand, organic matter content and carbon to nitrogen ratio, more related with biological fertility and biodiversity of soils, are immediately less interesting and, as the hands-on experience pointed out, require more effort to be appreciated by agricultural operators. Targeted information campaigns and training activities may be developed among the agricultural community to make them aware of the importance of increasing soil organic matter content, and the possible use of pelletized composted animal manure. Further studies should be addressed toward gaining more insights into the beneficial effects of the information and training activities for pelletized compost adoption

Effects of pelletizing pressure and the addition of woody bulking agents on the physical and mechanical properties of pellets made from composted pig solid fraction

This study reports the effects of the addition of different woody bulking agents and pelletizing pressure on the final bulk density, durability and compression resistance of pellets manufactured from composted pig solid fraction. Two pressure levels (3.5 and 5.0 MPa) and three different types of compost (SFC - pig solid fraction, BC - pig solid fraction mixed with woody biochar, and WC - pig solid fraction mixed with wood chips) were investigated. The study shows that the different pressures adopted - in the range of 3.5 to 5.0 MPa - and the addition of woody bulking agents did not significantly affect the physical and mechanical properties of the pellets. However, according to the results of the study, the particle dimension of the woody bulking agents plays a key role in the mechanical properties of the pellets; the smaller the particles, the higher the pellet mechanical properties. The pelletizing process increased the bulk density of the investigated composts, and pellet durability was always high (> 80%). Nevertheless, when comparing the two bulking agents, the best results in terms of final quality were observed for pellets made from pig solid fraction mixed with woody biochar

Factors Influencing Adoption of Compost Made from Organic Fraction of Municipal Solid Waste and Purchasing Pattern: A Survey of Italian Professional and Hobbyist Users

Composting represents an alternative for the management of the organic fraction from municipal waste. However, the adoption of compost made from municipal waste is not yet widespread across all European countries, including Italy. Being ‘professional’ (i.e., farmers and gardeners) and ‘hobbyists’ the most representative categories of compost buyers in Italy, this study investigated their attitude toward municipal waste compost adoption and their purchasing pattern, pointing out criticalities and strategies to promote a wider use of this kind of compost. For the two categories of users, frequency of use of different information, buying habits, opinions on marketing issues, and factors which encourage compost utilization were investigated. The ‘professionals’ and ‘hobbyists’ reported different purchasing behaviors in terms of quantity, frequency, and preferred packaging format. The capability of compost from municipal waste to improve soil characteristics and its low environmental impact were identified as the most significant aspects for users, while availability of economic subsidies was not a determining factor for municipal waste compost adoption. With regard to the information sources, the broader use of personal communication channels like peers’ suggestions may have influence on compost adoption pointing out how social influence can promote sustainable behavior and influence users’ purchasing choices