• Energy Research

Among environmental issues related to intensive livestock activity, emissions to air from manure management are of increasing concern. Thus the knowledge of the effect of treatment application on subsequent emissions from manure is required to assess the environment impact of management solutions. This work addresses the effect of anaerobic digestion and phase separation on emissions during storage by studying nitrogen losses from lab-scale stores and field pilot-scale stores of a co-digestate cattle slurry and its respective separated fractions. Lab-scale experiment was carried in temperature-controlled room where each fraction (untreated, separated liquid and separated solid) was stored in duplicate for a period of 32 days in 30 L vessel. Pilot-scale experiment was carried out both during the cold season and during warm season for 90 days of storage. In both experimentations samples of the manure were analysed periodically for total Kjeldahl nitrogen (TKN), total ammonia nitrogen, dry matter and volatile solids and pH. These analyses allow estimating nitrogen losses in different storage conditions. Effects of mechanical separation and season were assessed by ANOVA (Wilcoxon test, P<0.05). In temperature controlled conditions nitrogen losses measured account for 13% and 26% of TKN for unseparated and separated slurries respectively. In field conditions during cold season nutrient losses were limited. On average unseparated and separated slurries lost respectively 6.8% and 12.6% of their initial TKN content. Much higher were the TKN losses from the slurries examined in warm season where losses raised up to 40% of the initial TKN content. Generally mechanical separation increases nutrient losses, but the differences were not significant in field conditions. The results highlighted that nutrient losses, in particular the nitrogen ones, can be considerable especially during summer storage. The latter, in case of separated slurries, are mainly related to the liquid fraction, which is responsible for up 92% of the losses. When phase separation after anaerobic digestion is used, mitigation options, as covers or slurry acidification, are advisable in order to limit the negative environmental impact.

Sustainable development and reducing natural and energy resource consumption are the focus of the policies of many institutions. In this context, livestock farming is one of the major anthropogenic sources of GHG and acidifying gas emissions and requires comprehensive analysis to minimise its ecological footprint. For this reason, it is beneficial to analyse the various processes within this production sector to reduce the consumption of resources, particularly water and soil consumption; reduce energy consumption; and try to valorise the biowaste produced, especially manure, byproducts and wastewater. Reusing residual bioresource and organic waste offers the possibility of valorising a discarded product and, at the same time, reducing the consumption of natural resources. For this purpose, biorefinery processes allow bioresources to be transformed into bioproducts or bioenergy. Therefore, this study investigates the application of biorefinery processes to animal-derived waste, aiming to extract valuable resources while curbing resource consumption. This review analysed 293 scientific papers on biorefinery processes published in the last 11 years applied to livestock biomass to extract relevant information to understand the evolution of this topic and formulate hypotheses regarding future research di- rections. The analysis strongly emphasizes energy production and a growing interest in insect cultivation. In the coming years, one of the most significant challenges will be the successful transfer of technologies and processes from experimental research to the applied industry. To do this, it will be necessary to reduce costs, exploit economies of scale, improve process management, and develop synergies between different industrial sectors to implement smart circular economy systems. Overall, this review aims to clarify the hypothesis driving research in this area and emphasizes the tangible applications of findings within the broader context of sustainable resource management.

Ammonia (NH3) emissions deriving from the management of livestock manure have a significant environmental impact, and therefore it is important to reduce them. Among the available options, the process of NH3 stripping is promising to remove NH3 from manures and digestates recovering it as a mineral fertilizer (e.g., ammonium sulfate) that is more widely adoptable on farms. The traditional stripping process takes place in batches; however, in this study, a continuous process was evaluated using a lab scale plant in which four reactors were used in series with different hydraulic retention times (HRTs) of 12 or 20 days. The NH3 recovery of each reactor was studied for the liquid fraction of pig slurry, dairy cattle slurry and digestate, applying simple headspace aeration. For 20 days of HRT, totals of 92%, 83% and 67% of NH3 were stripped from the digestate, pig slurry and dairy cattle slurry, respectively. For 12 days of HRT, total NH3 recoveries were 83%, 60% and 41% for the digestate, pig slurry and dairy cattle slurry, respectively. The inlet NH3 concentration and inlet total alkalinity had a positive and negative effect, respectively, on the specific NH3 removal rate for each reactor. Stripping NH3 on farm scale can abate NH3 emissions in response to the environmental concerns of European policies.

Emission quantification from the agricultural sector, and especially from livestock manure management, is relevant for assessing mitigation strategies and for inventory purposes. There are different direct techniques used to monitor emissions from quiescent surfaces. Common techniques include the closed static chamber and the open dynamic chamber. The aim of this study was to evaluate and compare different direct methods, two dynamic hoods and one static hood, for monitoring NH3 and greenhouse gas (GHG) emissions (N2O, CO2, and CH4) from different emission sources. These sources are ammonia solutions and different by-products of manure (compost, liquid fraction of digestate, and solid fraction of pig slurry). The use of dynamic hoods, despite their differences in size, operation, and applied air flux, presents comparable emission rates for all emissions and compounds assayed. These rates are always higher than those obtained using static hoods. Therefore, it can be concluded that the use of dynamic hoods is a valuable technique for refining the indirect estimation of emissions.

The aim of this 5-year study was to evaluate the technical, economic, and environmental performances of a collective-based integrated treatment system for bioenergy production and nutrients removal to improve the utilization efficiency and reduce the environmental impact of land applied livestock manure. The study involved 12 livestock production units located in an intensive livestock area designated as nitrate vulnerable zone with large N surplus. The treatment system consisted of an anaerobic digestion unit, a solid–liquid separation system, and a biological N removal process. Atmospheric emissions and nutrient losses in water and soil were examined for the environmental assessment, while estimated crop removal and nutrient utilization efficiencies were used for the agronomic assessment. The integrated treatment system achieved 49% removal efficiency for total solids (TS), 40% for total Kjeldahl nitrogen (TKN), and 41% for total phosphorous (TP). A surplus of 58kWh/t of treated manure was achieved considering the electricity produced by the biogas plant and consumed by the treatment plant and during transportation of raw and treated manure. A profit of 1.61 €/t manure treated and an average reduction of global warming potential by 70% was also achieved. The acidification potential was reduced by almost 50%. The agronomic use of treated manure eliminated the TKN surplus and reduced the TP surplus by 94%. This collective integrated treatment system can be an environmentally and economically sustainable solution for farms to reduce N surplus in intensive livestock production areas.

Livestock buildings in rural areas are increasingly recognized for their environmental impact, yet few studies provide applied, scenario-based evaluations to guide retrofit interventions. While the existing literature acknowledges the environmental burden of livestock facilities, it often lacks operationally grounded analyses applicable to real-world agricultural contexts. This paper proposes an original integration of experimental climatic monitoring and life cycle assessment (LCA) to evaluate retrofit scenarios for energy efficiency in real poultry farming contexts. Based on an accurate climatic monitoring campaign conducted on-site during the spring and summer periods, relevant data were collected on air temperature, humidity, wind speed, and solar radiation affecting two poultry tunnels in central Italy, highlighting the need for thermal mitigation. The comparison between the observed operational scenario and the hypothesized improved scenario, involving energy supply from photovoltaic sources, evaluated using the PVGIS tool, demonstrated a significant reduction in environmental impact, with a 33.4% decrease in global warming potential and a 26.1% reduction in energy consumption. This study combines experimental on-site climatic data collection with comparative environmental evaluation using LCA methodology. The LCA approach, which guided the entire study, highlighted how the energy efficiency gained through solar panels adequately offsets their production and maintenance costs over the long term. These findings offer a replicable model for energy retrofits in rural livestock facilities, contributing to both environmental goals and rural resilience.

Collective manure processing facilities to reduce nutrient loads and produce renewable energy are often proposed as feasible solutions in intensive livestock production areas. However, the transferring of effluents from farms to the treatment plant and back to farms, as well as the treatment operations themselves, must be carefully evaluated to assure the environmental sustainability of the solution. This study evaluated the global warming potential (GWP) and acidification potential (AP) of a collective treatment plant for bioenergy production and nitrogen removal as an alternative strategy to conventional on-farm manure management systems. Two manure management scenarios were compared: manure management on individual farms and management by a collective treatment plant. Data were collected at a collective processing plant and at the individual farms of the consortium to estimate emissions of CO2, CH4, N2O, NOx, NH3 and SO2. The plant receives manure from 21 livestock production units, treating 660 tonnes day−1 of manure. The GWP and AP indicators were calculated to evaluate the potential impact of the two management solutions. The collective solution reduced both GWP (−52%) and AP (−43%) compared to manure management separately by each farm. Further improvement might be obtained in both indicators by introducing mitigation techniques in farm manure storage and manure application to soil.