The pursuit of sustainable energy production through the conversion of agricultural waste into different bioenergy resources is of paramount importance given its potential to mitigate environmental impact while meeting energy demands. In this review, a comprehensive overview of the technologies for the biochemical and thermochemical conversion of agricultural waste into bioenergy is provided. A summary of the process of its conversion into different bioenergy products such as biogas, bio-oil, and biofuel is provided, in addition to the potential advantages and challenges faced using different biomass conversion technologies. The review highlights the potential of agricultural waste valorization to address the current energy demand while at the same time contributing to environmental benefits and greenhouse gas emission reductions. Moreover, this review highlights some significant gaps for improvement. These include the challenges in the pretreatment of agricultural waste biomass in optimizing the conversion rates and lowering the required energy consumption throughout the process while enhancing both the quantity and quality of the output. Some recommendations are proposed to address the identified challenges. These include the need for further studies for a thorough assessment to evaluate the efficacity and sustainability of agricultural waste valorization technologies. Assessment methods such as life cycle assessment (LCA), life cycle analysis (LCA), net energy ratio (NER) calculations, life cycle costing (LCC), as well as techno-economic assessment (TEA), are recommended, together with collaboration among governments, farmers, and researchers, as well as the integration of cutting-edge technologies to enhance various aspects of agricultural waste, optimizing the conversion process, cost efficiency, time management, and labor requirements, consequently boosting the conversion efficiency and product quality.

Foodwaste (hereinafter, FW) is the most voluminous solid waste and its amount is growing rapidly all over the world. The turning of FW into biogas via anaerobic fermentation is widely recognized as an environmentally responsible and economically reasonable option. Based on the knowledge obtained from agricultural biogas stations, the current methods of FW fermentation management are based on balancing the ratio of total carbon and nitrogen. However, it was repeatedly and independently reported that the stability of this process is low, resulting in many concessions in terms of prolonged hydraulic retention time or reduced biogas yield. Hence, biochemical as well as economic performance of the process is balanced by mixing of FW with agricultural residues. FW samples of various origin were collected and biochemically analyzed. The data indicate that FW originating from homes and luxury restaurants tends to be lignocellulose-based, whereas the levels of crude fiber (25% up to 27%) are higher than those from agricultural feedstock (18%). In contrast, FW from school canteens and inexpensive restaurants tends to be starch-based with high levels of amyloids (21% up to 23%) and fat (5% up to 7%). A novel method better reflecting the bioavailability of carbon and nitrogen to anaerobic consortia is proposed. It is demonstrated that the previous optimization methods could somehow reflect the availability of nutrients in agricultural feedstock, as carbonaceous and nitrogen sources are relatively equally biodegradable. Nevertheless, the biodegradability of FW is considerably different, which is why higher amounts of proteins and lipids lead to increased levels of ammonia and sulfide, resulting in an inhibitory effect on the metabolism of anaerobic consortia. Optimizing the anaerobic fermentation of FW by the new method outperforms the previous technique and makes it possible to process FW more intensively, or, more precisely, with higher profitability and lower proportion of ballast agricultural feedstock.

The share of renewables is rising rapidly, especially in developed countries. Biogas production from purpose-grown phytomass is undergoing the fastest growth. The trend is linked to the production of vast amounts of fermentation residues. However, it has been repeatedly and independently reported that intensive or long-term application of fermentation residues into arable land changes soil structure, resulting in sharp degradation of its fertility. This is now compensated by more intense use of agrochemicals and additional agrotechnical operations such as biochar addition. However, the increased cost is beginning to threaten the economic sustainability of biogas production. Given the fact that the production of biogas from purpose-grown phytomass has become a strong pillar of the electricity grid, the threat to soil fertility may endanger its stability. The quality and quantity of soil organic matter (SOM) and in particular its stable organic fractions with ion-exchange properties (SOF) that determine soil fertility, or, more precisely, the transport of nutrients and their availability for plant growth, were investigated in detail. A novel, undemanding and quick method allowing the analysis and interpretation of SOM and its SOF was proposed and compared with conventional methods. It was confirmed that the adaptation of the new method enables farmers to better choose organic and mineral fertilizers and corresponding agronomic operations, so the soil can provide higher yields and an increased water retention capacity (up to 7%), which results in improved water retention during extreme rainfalls or droughts, altogether lowering the cost of purpose-grown phytomass, or, more precisely, improving the economy of biogas production. Abbreviations: SOM: Soil organic matter; SOF: Stable organic fractions of SOM with ion-exchange properties; WRC: Water retention capacity; ARC: Air retention capacity; TOC: Total organic carbon; CEC: Cation exchange capacity; HA: Humic acids; FA: Fulvic acids; NHSOM: Non-humified soil organic matter; PSOM: Primary soil organic matter; C_ox: Oxidizable carbon

This paper considers the evolution of processes applied in agriculture for field operations developed from non-organized handmade activities into very specialized and organized production processes. A set of new approaches based on the application of metaheuristic optimization methods and smart automatization known as Agriculture 4.0 has enabled a rapid increase in in-field operations’ productivity and offered unprecedented economic benefits. The aim of this paper is to review modern approaches to agriculture machinery movement optimization with applications in sugarcane production. Approaches based on algorithms for the division of spatial configuration, route planning or path planning, as well as approaches using cost parameters, e.g., energy, fuel and time consumption, are presented. The combination of algorithmic and economic methodologies including evaluation of the savings and investments and their cost/benefit relation is discussed.

The research suggests a production method of insulating composites created from lignocellulosic agricultural biomass with fungal mycelium as a binder agent and offers a deeper investigation of their thermophysical properties. Particularly, the samples were meticulously evaluated for density and thermal conductivity. The function was built on the suggestion by the authors regarding the thermal conductivity-weight ratio indicator. The metric was initially introduced to assess the correlation between these parameters and was also applied to qualitatively evaluate the biocomposite among other commonly used natural insulations. An applied polynomial trend analysis indicated that the most effective densities for the wheat, hemp, and flax, which were 60, 85, and 105 kg·m⁻³ respectively. It was determined that the optimal density for wheat and hemp composites corresponded to values of 0.28 and 0.20 W⁻¹·kg⁻¹·m⁴·K of the coefficient, respectively. These values were superior to those revealed in other common natural insulating materials, such as cork, cotton stalks, hempcrete, timber, etc. As a result, the proposed insulating material may offer numerous opportunities for application in industrial settings of civil engineering.

From the moment it was first indicated that use of aluminum chloride during purification of drinking water might be one of the triggers of Alzheimer’s disease, it took only a few years to almost abandon this practice worldwide. Now, two years after the initial evidence was presented that the cheapest possible replacement for aluminum chloride (ferric hydroxide, better known as ferrous sludge) significantly threatens soil fertility, there is almost no action. A robust case study was conducted among European drinking water treatment plants. First, it is reported that some samples of ferrous sludge can reduce phosphorus availability by more than 70%. This creates a precondition for a significant reduction in fertility over a decade. Because the legislation usually responds to similar findings with great delay, the extent to which managers of drinking water treatment plants are willing to change process settings by themselves has also been assessed. The findings obtained allow us to expect that a long continuation of this hazardous practice can be expected, since managers of drinking water treatment plants show little willingness to switch from the ongoing questionable technology (harmful to nutrient cycles in soil) to environmentally favorable (though slightly more costly) solutions.