Nitrogen flow in livestock waste system towards an efficient circular economy in agriculture.

The race is on to achieve an important level of efficiency in the attainment of a circular economy in agriculture especially with the aim of sustainable nitrogen management. This cycle in the agricultural sector cuts across livestock farming, agriculture-induced waste generation, recycling and utilization, energy generation, crop production, ecosystem protection and environmental management through the mitigation of climate changes. In this work, we assess the process and functionalities of livestock waste generated from the piggery farm and their combinations with other by-products such as biochar and ash in comparison with mineral fertilization as sources of nitrogen applied in agricultural soil. The experiment was performed in a controlled environment with wheat (Triticum aestivum L.) grown in a neutral and an acidic soil. Pig manure was used as the primary feedstock, fed and processed to biogas and nutrient-rich digestate by the anaerobic digestion process. The results revealed that the co-amendments of pig manure digestate with biochar and ash had complimentary positive effect on measured indices such as mobile potassium, phosphorus, biomass yield and nitrogen use efficiency. The mineral nitrogen fertilizer significantly induced carbon dioxide emissions from day 35 when compared to emissions from the organic amendments. In contrast, the organic amendments influenced nitrous oxide emissions from the onset till day 30 before flattening out. The individual combination of pig manure digestate with biochar and ash had a negative influence on enzymatic activity (dehydrogenase). Soil microbial biomass carbon was induced across all treatments in both soil types. Pig manure digestate + ash and pig manure digestate had 32.1 and 48.8% soil microbial biomass increase in neutral soil and acidic soil, respectively. Overall, the processing and application of single-use amendment or in combination with biochar and ash holds huge potential in the optimization of nitrogen and carbon efficiency towards sustainable soil management via improving soil quality, carbon sequestration and climate change.

Synergetic approach for energy recovery from coastal wastes based on combination of biological and thermal treatment.

Marine biomass is a promising renewable energy source, especially as this waste contains a large amount of cellulose and hemicellulose, which can contribute to convert it into energy products using anaerobic digestion (AD) and pyrolysis processes. This work was focused on a synergetic view of marine coastal waste treatment (seaweed) using two different technologies, anaerobic microbiological co-digestion, and pyrolysis. The experiments were performed with two merged technologies to assess the captured energy from the digestate in case it is contaminated. Anaerobic co-digestion was conducted using a periodic load laboratory bench with a vertical biogas digester. An evaluation of possible product yields and composition during pyrolysis at a laboratory-scale bench has been performed. The products obtained after the thermal treatment analyzed using an online gas measurement system and gas chromatographs Agilent 7890A with TCD detector (for gases) and Agilent 7890A with MS detector (for liquids).The results demonstrated that biogas yield was 174.1 l/kg (DM). Seaweed washed by seawater yields a higher amount of biogas (202.5 l/kg). Meanwhile, seaweed, sewage sludge, and digestate samples subjected to thermal treatment produced 17%, 30%, and 15% of liquids products, respectively. The economic performance assessment showed that the application of the developed merged approach on an industrial scale could provide an economic return of up to 8.3 $/100 kg of waste. Based on that, merged AD and pyrolysis technologies could be adapted as a promising technology to valorize seaweed wastes and utilize them as a new sustainable source for renewable energy.

Comparative analysis of the environmental impact of conventional and precision spring wheat fertilization under various meteorological conditions.

Precision farming is being approached with hopes of discovering new decisions that could aid in managing and reducing the environmental impact of farming systems with increasing frequency. Analysis of the results obtained from a five-year research period has revealed no significant difference in the amount of produce received, irrespective of the fertilization technology (variable-rate fertilization (VRF) or conventional fertilization (CF)) used on spring wheat crops. However, in VRF, nitrogen fertilizer consumption was approximately 19% lower, and the fertilizer use efficiency was higher. The energy assessment of the fertilization technology indicated that the application of the VRF technology reduced the indirect energy inputs by 12.3%, which compared to CF, resulted in an approximately 9% higher energy efficiency and productivity. Meteorological conditions significantly affected not only the spring wheat yield, but also the nitrogen fertilizer consumption, efficiency, and energy indicators such as energy efficiency and productivity. The environmental assessment of these technologies also showed that nitrogen fertilizer accounted for about half of greenhouse gas (GHG) emissions. Thus, the evaluation of these results obtained over the entire five-year research period indicated that when VRF was used, GHG emissions were 9.4% lower than when CF was used.

Energetic and Economic Evaluation of Zero-Waste Fish Co-Stream Processing.

This study evaluates the possibility of recovery of high-quality valuable fish oil and proteins from fish co-streams by traditional means or a combination of several technologies. A techno-economically feasible and sustainable zero-waste process is needed for full utilisation of this co-stream's potential. This study aims to determine the energy efficiency and economic feasibility of four different zero-waste bio-refineries based on salmon filleting co-streams. The study covers four concepts: (I) biogas and fertiliser production from salmon co-streams, (II) fish silage production, (III) thermal processing of salmon co-streams for producing oil, protein concentrate, and meal, and (IV) novel two-stage thermal and enzymatic process for producing high-quality oil and protein hydrolysate, while the solid residue is converted to biogas and fertilisers. Monte Carlo simulation is used to evaluate uncertainties in economic evaluation. The results show that the two-stage processing of fish co-streams leads to recovery of both high-quality marine oil and proteins, showing the largest profitability and return on investment during the economic analysis. It is a more tempting option than the currently used thermal treatment or traditional silage processes. The possibility of producing food-grade fish protein hydrolysate is the biggest benefit here. Concepts studied are examples of zero-waste processing of bioproducts and illustrate the possibilities and benefits of fully utilising the different fractions of fish as fillets, oil, protein, fertilisers, and energy production.