• Energy Research

Municipal and agricultural biowaste are a significant portion of the global waste stream and represent an environmental challenge that must be addressed sustainably. The literature on the topic has increased dramatically, and a bibliometric analysis is a necessary guide through this ever-growing production. This study gives an objective overview of the state of the art and topic evolution of biowaste within sustainability/circular economy frameworks. This bibliometric analysis serves as a starting point for further qualitative research, while offering opportunities for future collaborations. Two parallel searches were conducted in Scopus, agri-food/agricultural (2391 papers) and municipal (264 papers) biowaste within sustainability/circular economy concepts, and analyzed with VosViewer (version 1.6.20.0) and Excel (version 1808). This review analyzes the following: annual scientific production and countries involved, showing the US and Italy as leaders on both topics; most productive authors (only 0.2% wrote at least five papers) and affiliations and underlying international, even if static, collaborations; most influential publications and sources (Science of the Total Environment, Journal of Cleaner Production, Sustainability); evolution of keywords over time; and strengths and limitations of the bibliometric approach. It also highlights the potential for future research and collaboration. Furthermore, it underlines waste management’s evolution from a sustainable point of view towards a circular economy approach and differences between municipal and agricultural biowaste scientific production.

Wood chips represent one of the most popular biomass fuel in latest cogenerating plants and in small heating systems. This fuel, being characterized by low bulk density, requires high transportation costs. This obstacle can be overcome by wood chips densification. The authors investigated the energy benefit of wood chips densification for transport operations for "short supply chain" as defined by the Italian government for the biomass fuel subsidy scheme. Three different woods (poplar, chestnut and a mixture of spruce and eastern white pine) chips and six different tractor's trailed trailers were investigated. The total specific energy (kJ kg-1) required to transport a defined quantity of wood chips, the energy saving ratio (%) from chips' compaction and the breakeven distance (km) between raw and compressed chips were calculated. The results highlights that densification process of wood chips is an interesting opportunity to improve the transport energetic convenience. The benefit of wood chips densification is strongly affected by raw wood chips density values and by trailer characteristics: the benefit is maximum when the density of compressed wood chips to be transported attains the vehicle theoretical density

In recent years, agricultural robotics has received great attention in research studies, being considered a way to address some important issues of the agricultural sector, such as precision agriculture, resources saving, improvement of safety conditions, and shortage of human labor. These issues are particularly relevant in greenhouse production systems, where many highly repetitive and sometimes dangerous operations are still required to be performed by humans. The purpose of the present review is providing an overview of the research conducted in recent years related to robotic automation for greenhouse applications. The currently available literature about robots and automated solutions for greenhouse applications has been reviewed through the consultation of international databases of journals. A total of 38 publications were included after screening and the information related to each retrieved automated solution was classified. The research highlighted great variability among studies, which often describe automation solutions designed for specific crops and define the specific “supporting tasks” necessary for the completion of a “main task”. Specifically, the technologies used for guidance and navigation systems, crop detection and fruit grasping system, spraying system, and other minor supporting tasks have been described. Furthermore, a critical appraisal of the main challenges of the sector and future research directions are provided.

Biomass, in particular wood, has become a fundamental renewable energy source that can replace fossil fuels in many applications, from eating to electricity production. Wood chips are one of the most popular biomass fuel in latest cogenerating plants and in small heating systems. This fuel has low bulk density and needs large volumes in handling and transport operations. These obstacles, common to many biological residues, can be overcome by densification. This study reports the effects of the compressing pressure on the demand of energy required in briquetting, final bulk density and durability of briquettes manufactured from wood chips. An hydraulic press was used to produce briquettes in controlled conditions. Five pressure levels (20, 30, 50, 80 and 110 MPa) and three different types of wood chips (PC - hybrid poplar, CC - chestnut, and MC - mixture of spruce white pine) were investigated. The study shows that the different pressures adopted significantly affect the specific compression energy, the final density and the durability of the compacted samples. Equations were developed to predict compact density and the specific compression energy required by the densification process. The specific compression energy values obtained in this study (18-58 kJ kg-1) were significantly lower than the specific energy required to manufacture pellets made from biomass feedstock (typically 19-90 kJ kg-1). Furthermore, chestnut wood chips with pressure at 110 MPa resulted in the maximum briquettes bulk density and durability.

<div class="section abstract"><div class="htmlview paragraph">Biomethane is a valuable alternative to fossil fuels, specifically in transport sector, contributing to “energy security” and “carbon neutrality”. Though at present, research has mainly invested in the automotive sector, the demand for alternative and low environmental impact fuels is growing. Hence, in the scope of energy transition, also in the agricultural sector machinery manufacturers have started developing the first solutions able to reduce the environmental impact of tractors. In addition, on-farm biomethane production would represents a great opportunity for the development of more “circular” systems producing renewable energy from “residual biomass” (e.g. livestock effluents, agricultural waste). Under this framework, the TOBIAS project, launched in 2020 and funded by the Piedmont Region (North-western Italy), is aimed to investigate the development and application of a biomethane supply chain for agricultural tractors engines. The project involves both industrial and academic partners: FPT Industrial, the project-leader, focusing on development and industrialization of the engines; STC srl, providing support to R&amp;D; DIMSPORT srl, integrating engines and biomethane fuel systems; Torino Crea Engineering srl, specialized in the construction of special vehicles; Hysytech srl, skilled in gas treatment and recovery; CNR-STEMS, focusing on the assessment of the system sustainability and promoting the advancement and dissemination of knowledge and technologies. The project will lead to the development of two biomethane-powered prototypes, one wheeled and one crawler. The development will consist of: i) vehicle and engine components design; ii) engine construction and testing to identify optimal operating conditions; iii) tractors configuration for the use of compressed or liquefied biomethane; iv) field-tests to determine vehicle performance (power, torque, consumption, etc.) in real conditions; v) demonstration of the specialized biomethane-powered tractors while performing agricultural operation in a vineyard and on-farm refueling. In the present contribution, project framework, preliminary results and future implications are discussed.</div></div>

Biomass pelletization has been proven to be a suitable option for the alternative use of animal waste aimed at lowering livestock farming environmental load. Despite this, the definition of the operative parameters for proper management of pellet quality is still on the go. In this research, swine manure solid fraction was composted with and without addition of sawdust as bulking agent and the bulk underwent compaction process into pellets at two levels of moisture (10% and 25%). The results of the investigation show that sawdust addition affect the surface of the pellets while pelletization of bulk biomass at 25% of moisture, showed better preservation of some important characteristics (e.g. total N, Humification rate) throughout the pelletization process. Proceedings of the 25th European Biomass Conference and Exhibition, 12-15 June 2017, Stockholm, Sweden, pp. 1318-1323

Silage is one of the typical systems to preserve biomass usually oriented from corn, sorghum, wheat, grass, and other forage and perennial crops. A critical task within the logistics operations in silage production, i.e. harvesting, transporting, and compacting, is the management of the biomass flow, in connection with the biomass storage system and the required conditions of the stored product depending on its further purpose of use. A key issue in large-scale silage production operations is the matching of the material processing capacity of forage harvester with the material removal capacity of transport units and the material processing capacity of the compactor, in order to maintain a steady material flow. This allows for the optimisation of the working chain.

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.