Due to climate change, two-thirds of mankind will face water scarcity by 2025, while by 2050, global food production must increase by at least 50% to feed 9 billion people. To overcome water scarcity, 15 million m3/day of untreated wastewater is used globally for crop irrigation, polluting the soil with pathogens, heavy metals and excess salts. Since 10% of the global population consumes food from crops irrigated with wastewater, pathogens transmitted through the food chain cause diseases especially in young children and women. In this paper, we discuss the status of water scarcity and the challenges to food security, the reuse of wastewater in agriculture and the possible risks to human and environmental health. The efficiency of different irrigation systems in limiting the risks of wastewater reuse and the latest regulations of the European Commission on effluent recovery are also presented. Hence, we emphasize that irrigation offers real perspectives for large-scale recovery of wastewater, helping to reduce the deficit and conserve water resources, and increasing food safety, with the express mention that investments must be made in wastewater treatment plants and wastewater must be properly treated before recovery, to limit the risks on human health and the environment.

Seeking to become more climate-friendly and less energy-consuming, the European Union has pledged to cut its greenhouse gas emissions and milestones to achieve this are set to 20 % by 2020, 40 % by 2030, 60 % by 2040 and 80 % by 2050. Due to its abundance, biomass is gaining more and more importance both for the production of thermal energy by direct combustion or gasification of vegetal materials, for electricity and for the production of biofuels. Direct combustion of biomass generates CO 2 , but the process is neutral in terms of greenhouse gas emissions, because the same amount of CO 2 was absorbed by plants from the air during their life cycle. Ecological solid fuels such as pellets have become rapidly a viable alternative to fossil fuels, due to their high energy content, which makes them suitable for use by both small households and industrial consumers. Pellets are obtained from a variety of raw materials such as: agricultural residues, energy crops, forestry and wood residues, used exclusively or mixed and having different physical-chemical properties. This paper presents a summary of literature on the effect of the moisture content on the properties of pellets obtained from various types of biomass. Moisture content of raw material is one of the most important factors that influence negatively the properties of pellets, such as bulk density or mechanical durability during storage and transportation. Energy consumption increases during pelletizing of high moisture biomass, as moisture is a lubricant that lowers friction in the die. Other studies found a positive correlation between pellets durability and optimal moisture (10 %), because water together with the die temperature, pressure and chemical composition of raw material acts like a binding agent that increases pellet quality. Pellets with 5 % moisture have low strength, become brittle, and large amounts of dust are produced during their storage and transportation. Moisture higher than 15 % damages pellets during storage.

Sugarcane is a lignocellulosic crop and the juice extracted from its stalks provides the raw material for 86% of sugar production. Globally, sugarcane processing to obtain sugar and/or ethanol generates more than 279 million tons of solid and liquid waste annually, as well as by-products; namely, straws, bagasse, press mud, wastewater, ash from bagasse incineration, vinasse from ethanol distillation, and molasses. If not properly managed, this waste will pose risks to both environmental factors and human health. Lately, valorization of waste has gained momentum, having an important contribution to the fulfillment of policies and objectives related to sustainable development and circular bioeconomy. Various technologies are well-established and implemented for the valorization of waste and by-products from sugarcane processing, while other innovative technologies are still in the research and development stage, with encouraging prospects. We propose a sustainable sugarcane processing flow and present an analysis of the physico-chemical characteristics of generated wastes and by-products. We emphasize the available possibilities of valorizing each waste and by-product, considering that they are important biomass resources for obtaining biofuels and a wide range of other products with added value, which will contribute to the sustainability of the environment, agriculture, and human health worldwide.

Grinding of cereal seeds is due to the mechanical action of several forces: compression, shearing, crushing, cutting, friction and collision, to which seeds are subjected, depending on the design if the mill used for grinding (roller mill, hammer mill, stones mill or ball mill). By applying these forces, when the mechanical resistance of the particles is exceeded, their division happens in a number of smaller particles of different sizes, geometric shapes, masses and volumes. An industrial wheat mill has several technological phases, starting with coarse grinding of seeds to fine grinding of the resulted milling products, after their sorting in fractions of different sizes. The first technological phase of grinding process, in wheat mills, is gristing or coarse grinding phase, which also consists of several technological passages. A technological passage consists of a grinding machine (roller mill), a machine for sifting and sorting of the resulted milling fractions (plansifter compartment) and, eventually, a machine for the conditioning of semifinal product (semolina machine or bran finisher). In a technological passage, intermediate fractions are obtained, which, by a new grinding, lead to the obtaining of high-quality flour at milling passages (fine grinding). Wheat processing requires a long and gradual transformation into flour. This process takes place after a gradual crushing schedule, from fine to finer, from machine to machine, of wheat seed, respectively of the crushed particles resulting from it. Each grinding operation is immediately followed by a sorting operation by sifting (fig.1) because during grinding, a wide variety of grinded seed particles is obtained.

Abstract. The interest in bioenergy, as a renewable energy source, has increased tremendously in the recent years. Biomass is a renewable source of energy that has an important contribution in reducing the use of conventional fuels and in reducing greenhouse gas emissions to the atmosphere. In this context, an increasing attention is given to the production and use of environmentally friendly biofuels: pellets and briquettes, biogas, biodiesel and bioethanol. Pelleting and briquetting processes have been used for many years to produce densified biomass for fuel applications. Densified biomass fuels such as pellets are preferred as they provide better economic viability for transport, storage and handling. The aim of this review is to examine the main factors that influence the durability of the pellets, (such as: biomass characteristics, moisture content, size reduction, and also the pelleting conditions, including the use of binders, feedstock mixes and operating temperature), because the durability is considered a measure of the quality of the pellets. Pellet durability can also be affected by the storage conditions. The mechanical durability of pellets is the measure of the resistance of densified fuels towards shocks or abrasion in consequence of transport and handling processes. In the paper there are analyzed all the parameters mentioned above for the pellets produced from different types of biomass (cereal residues, wood chips and energy crops), highlighting the influence of each on the process and their sustainability.Keywords: biomass, durability, pellets, energy plants. IntroductionInterest in renewable energy resources has increased in recent years because of the rising energy demand and fuel costs, environmental and national security concerns and finite supplies of fossil fuels. As power generators continue their search for alternative energy sources to coal, biomass remains a promising carbon-based renewable fuel [1]. Biomass is a renewable source of energy that has an important contribution in reducing the use of conventional fuels and in reducing greenhouse gas emissions to the atmosphere. In this context, an increasing attention is given to the production and use of environmentally friendly biofuels: pellets and briquettes, biogas, biodiesel and bioethanol. Biomass is the totality of organic substances occurring in a natural habitat, a distinction being made between phytological and zoological mass [2]. Biomass pellets (wood, wheat straw, rape straw, and peat) as fuels are of great interest for district heating because they can contribute to greenhouse gas emission reductions and provide a more efficient use of local energy resources [3]. Pellets are a suitable biomass feedstock for both heat and power applications, with co-firing in coal-fired power stations currently being their main large-scale application. The industrial trade for wood pellets involves the international bulk transport of more than 10 million tons annually.Production of pellets and the demand have been rapidly increased in Can...

This paper presents theoretical and experimental research studying the influence of process parameters on the quality of biomass pellets. A validated mathematical model was developed, expressing the density of biomass pellets as determined by moisture content, compression pressure, process heat, the initial density of the material, pelleting speed and initial volume of the material. The experiments for determining the influence of these parameters on the compression of biomass into pellets and optimizing the process were conducted on a heated single pellet compression device, using fir sawdust as raw material. To describe and study the process, four input and control parameters were varied—raw material moisture, pelleting speed, maximum force applied and pelleting die temperature. From the experiments, it was noticed that overall, moisture and pressure have the most important effect on the compression process and pelleting speed, and heat applied also affected the process. Pellet density decreased when pelleting speed and material moisture increase and the density increased with a higher compression pressure and higher heat during the process.

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Turkey has a large agricultural area and produces 55–60 million tons of biomass waste/year. This study aimed to obtain bio-briquettes from three types of dried greenhouse wastes and to determine their strength parameters. A prototype of a mobile briquetting machine driven by power take-off (PTO), with hydraulic pistons, and comprising a shredder and grinding or crushing unit with a briquetting pressure in the range of 0–190 MPa, was used. The physical parameters of the obtained briquettes were determined, including density, tumbler and shatter resistance, compression resistance, water intake capacity, and resistance to moisture-humidity. The results of physical and mechanical tests showed that the briquettes are of an extremely high quality. The maximum density, shatter and tumbler resistance were 1143.52 kg·m−3, 99.24% in pepper plant waste, and 98.52% in eggplant plant waste, respectively. Based on the analysis of compression tests obtained under 190 MPa (maximum compaction force of 450 kN), the maximum compression force, compression stress, and specific compression force were found in briquettes made from tomato plant wastes (3315 N, 69.43 N·mm−2, 40.09 N·mm−1, respectively). Overall, the results and variables affecting the strength parameters showed that greenhouse waste biomass is an excellent feedstock for the production of high quality bio-briquettes. The valorization of briquetted greenhouse waste with the proposed prototype contributes to the sustainability of the environment and to a reduction in energy costs for farmers.