Preface

Agricultural wastes (AW) can be defined as the residues from the growing and processing of raw agricultural products such as fruits, vegetables, meat, poultry, dairy products and crops. Agricultural wastes can be in the form of solid, liquid or slurries depending on the nature of agricultural activities. Furthermore, agricultural industry residues and wastes constitute a significant proportion of worldwide agricultural productivity. Although the quantity of wastes produced by the agricultural sector is significantly low compared to wastes generated by other industries, the pollution potential of agricultural wastes is high on a long-term basis. This book discusses the characteristics, types and management options for agricultural wastes.

Chapter 1 - Agricultural wastes (AW) can be defined as the residues from the growing and first processing of raw agricultural products such as fruits, vegetables, meat, poultry, dairy products and crops. AW can be in the form of solid, liquid or slurries depending on the nature of agricultural activities. Agricultural industry residues and wastes constitute a significant proportion of worldwide agricultural productivity. Although the quantity of wastes produced by the agricultural sector is significantly low compared to wastes generated by other industries, the pollution potential of agricultural wastes is high on a long-term basis. The opportunity and feasibility for recycling these wastes comes from two directions: the care for environment reflected by new sets of rules and regulation and the potential to add value to these wastes by adding positive elements. Moreover, they can be used as precursors in many other sectors such as membranes, biosorbents or activated carbons for the removal of dyes, organic molecules, heavy metals and fertilizers. Different types of agricultural wastes, i.e., deoiled soya, coconut shell, neem leaves, hyacinth roots, rice husk, rice straw, rice bran, lemon leaf, tea waste, potato plants wastes, tomato wastes, sesame hull, garlic peel, peanut hull, carrot stem, carrot leave, barley straw, banana stalk, olive stones, almond shells, peach stones, apricot stones, cherry stones, grape seeds, Trapa natans husk, bamboo, doum-palm seed coat, walnut shells, rose seed, pine sawdust and coir pith are ideal raw materials for different industrial applications due to their low cost, non-toxic content and their abundance. The final products derived from agricultural wastes have shown equal or even better properties compared to conventional products concerning separation, adsorption and fertility. Previous studies and projects dedicated to the development of AW treatment technologies focused mainly on the reduction of the wastes organic load and on the reduction or the recovery of valuable substances and succeeded to develop suitable technologies and methods. However, if land distribution is planned the organic load and the toxic substances of treated wastes should not be the only issues of concern. Specific care should be taken also for inorganic constituents and especially for K, Cl-, NO3-, SO42-, P, Mg, Fe, Zn and others, since the very high concentrations disposed on soil change its quality properties drastically, while electrical conductivity and the concentrations of inorganic soil constituents such as K, P, Fe, Cu remain high even after many years from the last disposal. These practices must take into account important specific local conditions, such as waste characteristic, soil type, background levels of nutrients and pollutants for soil, water and plants, the climate, the relevant crops and the local agricultural practices. Emphasis will be given on specific knowledge and technologies developed so far in Mediterranean countries, their impacts, and constraints and knowledge gaps. Furthermore, policy issues for AW use in Europe and especially in the Mediterranean countries at various levels will be considered. Therefore the aim of this study is to examine the properties and uses of new products derived from agricultural wastes and to research and advance agricultural practices with the use of treated agricultural wastes by recycling nutrients and water from treated agricultural wastes.

Chapter 2 - The design of new food products and agricultural practices have generated a wide diversity of co-products and effluents that often contain a high load of organic matter, from which valuable compounds could be isolated. The surplus and concomitant underutilization of these streams establish serious economic and environmental challenges. Whey, a main co-product arising from cheese manufacturing, was previously considered an environmental pollutant but it is now regarded as a source of many valuable compounds. Among current applications, the production of whey protein concentrates and isolates via ultrafiltration represents the major industrial revenue arising from this stream. The recovery of whey proteins generates an enormous volume of another co-product known as whey permeate. This stream has a high organic load being primarily composed of lactose and minerals. However, recent scientific literature demonstrates the presence of other compounds such as oligosaccharides and peptides, possessing unique bioactivities. Because of the worldwide increase in cheese production, the utilization of whey permeate is under strong scrutiny, with many different strategies being developed to add value to this waste stream. The development of feasible industrial processes to transform, isolate and recover valuable compounds is a key step towards the mitigation of environmental and economic problems arising from constant evolution of our food industry. This chapter focuses on the current utilization and research efforts to valorize whey permeate, where specific processing and environmental challenges are addressed along with the state-of-the-art of the processes and utilizations for the naturally occurring compounds in whey permeate, as well as the valuable products that can be generated from this stream.

Chapter 3 - The olive tree is extensively cultivated in countries of the Mediterranean basin; the area currently under cultivation covers roughly 5.5 106 ha in the EU and 11.0 106 ha in the world. By-products from olive culture and related industries, such as prunings, leaves, olive pomace, and olive stones, are interesting materials for the production of energy, food, fertilizers and other chemicals due to the large available feedstock and their chemical composition. Olive stones are by-products derived from the olive oil extraction industry and from manufacturing of pitted-table olives. Basically, there are two current ways for valorization of olive stones: thermochemical (energy source by combustion, gasification or pyrolysis) and biochemical (ethanol and xylitol production) conversion. Bioconversion of olive stones can also provide other high added-value products such as xylooligosaccharides or natural antioxidants (tyrosol and hydroxytyrosol). Finally, comparison of the different procedures and potential future applications will be discussed as well.

Chapter 4 - Billion metric tons of agricultural residues are generated every year from industry worldwide that may be considered one of the most abundant, cheap and renewable resources on earth. However, they are normally incinerated or dumped causing environmental problems such as air pollution, soil erosion and decreasing soil biological activity. The reuse of these residues not only prevents environmental concerns, but also can provide farmers the opportunity of a second income from plantation. The incorporation of agricultural residues into polymer matrices is currently a trending topic in research due to the relatively high strength, stiffness and low density of natural fibres present in these residues. Nut by-products, such as almonds (brown hulls, shells and seeds coating) or walnuts (shells), among others, have been used as reinforcement in polymeric materials due to their desirable properties: low density and cost, availability, recyclability, environmental friendliness, total degradation without emission of toxic compounds in composting conditions, and good mechanical properties. On the other hand, nut residues (peanuts, almonds, hazelnuts, chestnuts, walnuts, pecan nuts or pistachios) are rich in bioactive compounds which can be extracted and further used as potential natural additives in food packaging materials with antioxidant and/or antimicrobial activity. In this chapter, different strategies for reusing nut by-products in polymer materials obtaining high value-added materials either as reinforcement or as a source of active compounds are reviewed. Finally, the utilization of gums is currently in the spotlight of the chemical industry.

Chapter 5 - Rice (Oryza sativa L.) is a very important component of human diet for many people around the globe. Rice world production is approximately 680 million tons year and Asia leads world harvesting. This is an important source of biomass, especially because there is a tendency to rationalize the use of crude oil and derivatives. Enhancing the utilization of biomass may help to avoid climate and environmental problems. The industrial processing of rice generates some byproducts, such as rice bran and broken rice. Both components can be used as nutritional constituents and they will not be discussed in this work. On the other hand, agricultural residues are relevant in the process, especially rice hull, which accounts for about 20% of the rice crop. This work presents some relevant aspects about the utilization of rice hull. There are many possible applications in different areas, including fermentation and production of ethanol, preparation of cellulose, synthesis of inorganic materials, such as pigments, zeolites, cements, composites, fillers, among others.

Chapter 6 - Biorefining has been defined by the International Energy Agency as the sustainable processing of biomass into a spectrum of marketable products and energy. The concept of sustainability, defined by the World Commission on Environment and Development, arose as consequence, among other reasons, of the energy crisis derived from the imminent depletion of the fossil resources. Thus, a global mindset change is required to face the present scenario, through the reconcilement of three important pillars: economical, societal and environmental issues. Since the current energy system results unsustainable because of imbalance concerns that will have environmental, economical and geopolitical implications far into the future, the sustainable development should be achieved by learning how to use/reuse our resources. In this sense, the use of biomass as a source of products and energy is not new, but its use under a sustainable perspective may imply interesting novelties. With this aim, the Biorefinery outlook should be constructed fulfilling some requirements such as the responsible and optimal exploitation of resources, the application of energy efficient processes and the accessibility of the resulting energy and products, i.e., a compliance in terms of a viable, bearable and equitable development. The available source of biomass (the biorefinery feedstock) determines not only the range of products obtained in the Biorefinery, but also the more or less specific technology and the optimal conversion pathway required for its transformation. These three parameters (feedstock, technology and conversion pathway) allow classifying the biorefining processes, and their combination offers a huge range of possibilities for the biomass exploitation. The use of agricultural wastes in a biorefinery concept offers a promising perspective of sustainable development. The agricultural activity generates significant quantities of lignocellulosic residues (over 60% of the total crop) that are usually left on the cropland or incinerated to prevent the spread of pests and uncontrolled fires. Against the high availability of this biorefinery feedstock, some other issues appear concerning the use of agricultural residues as bioproducts source: volume variability, crop seasonality, low density, heterogeneous chemical composition, localized generation ... These factors are negatively considered when agricultural wastes are proposed as biorefinery feedstock. In the present work, several crop residues (woody and non-woody wastes) were chemically characterized for determining their contents of the main lignocellulosic components (cellulose, hemicelluloses and lignin). Other biomass components, such as moisture and ash, were also determined. In addition, hot water and weak soda solubilities were measured in order to establish the treatability of these agricultural wastes in a biorefinery concept. According to the results, and after an exhaustive crop production assessment, some biorefinery scenarios were proposed considering different worldwide agricultural productions.

Chapter 7 - Large amounts of wastes arising from industrial processing of agricultural products constitute alternative renewable bioresources potentially attractive for bioenergy generation and/or for the manufacture of other useful products. Their conversion additionally contributes to reduce environmental pollution. The present chapter examines thermochemical conversion of the wastes generated from industrialization of an agricultural product into biofuels and/or products potentially applicable for environmental remediation. The selected wastes arise from industrial processing of whole branches (leaves and twigs) from a native evergreen tree Ilex paraguariensis, belonging to the Aquifoliaceae family, for the manufacture of yerba mate. It is a widespread product massively consumed in Southern Latin America countries to prepare a popular herbal tea-like beverage. The commercial final product generally contains less than ~ 35% twigs, since they provide an unpleasantly bitter taste to the infusion, and therefore huge quantities of unused twigs emerge as a by-product. Kinetics for the pyrolysis of the twigs is characterized by non-isothermal thermogravimetric analysis from room temperature up to 900 °C to obtain information for the proper design of full-scale pyrolyzers. A deactivation model which assumes an overall first-order process and considers the physicochemical changes taking place in the biomass with the pyrolysis course through variations of the reaction rate constant with the temperature and solid conversion enables a proper representation of the experimental data over the whole temperature range, with estimated energy activation values between 49 and 137 kJ mol-1. Likewise, yield and characteristics of the three kinds of pyrolysis products, comprising bio-char, bio-oil, and gases, are examined from experiments conducted in a bench-scale fixed-bed installation at temperatures in the range 400 - 700 °C. Gas yield increases with increasing temperature, attaining 43% at 700 °C, while the biochar yield decreases from 30% to 20% with temperature rise. Yield of the bio-oil attains a maximum (53%) at 500 °C, likely arising from the competition between primary formation of volatiles, at relatively low temperatures, and secondary degradation of the condensable vapors at the higher temperatures. All the pyrolysis products could be used in energy applications. The obtained biochars with higher heating value (HHV) of 23 - 24 MJ kg-1 have potential as environmentally friendly solid biofuel and could be employed for the manufacture of briquettes mainly for domestic use. Accounting for their high stability, as judged from the molar O:C ratio, another possible application could be incorporation of the biochars into the soil for the storage of atmospheric carbon. In turn, the bio-oils show organic fractions with HHV between 28 and 33 MJ kg-1. Density values of the as-produced liquids (~1 kg dm-3) are rather higher than those for conventional hydrocarbon fuels due to their higher contents of oxygen and water. The crude bio-oils could be directly burnt or subjected to further upgrading to attain characteristics similar to those of fuel-oil. Pyrolysis of the twigs yields low to medium heating value-gases (5 - 11 MJ m-3), mostly composed by CO2, CO, CH4 and H2. Gas composition depends on the temperature, even though CO2 is the major generated species, followed by CO. Proportion of CO2 decreases with temperature, particularly at 700 °C, accompanied by enhancements in the HHV of the gaseous mixtures, as a consequence of compositional variations, attaining a maximum value of 11 MJ m-3. They might contribute to the energy sustainability of the process. Besides, phosphoric acid activation of the yerba mate twigs at pre-established moderate conditions leads to good quality activated carbons with well-developed porous structures characterized by textural parameters (BET surface area of ~ 1000 m2 g-1; total pore volume of 1cm3 g-1) comparable to those of commercially available samples.

Chapter 8 - Wastewater from many industries such as textile, leather, paper, printing, food, etc. contains large amount of hazardous dyes. Dyes are not biodegradable and photodegradable due to its synthetic origin and complex aromatic nature. Among various physiochemical processes, adsorption techniques are usually widely used to treat dyes laden wastewater. Although commercial activated carbon is the most widely used adsorbent with large success, its use is limited due to high cost and difficulties in regeneration. Therefore there have been explosive growths in research concerning the use of alternative cost effective non-conventional effective adsorbents in the removal of dyes from aqueous solution. In this research direction, agricultural by-product solid wastes which are available in large quantities worldwide with almost through away price are utilized as effective adsorbents in the removal of inorganics and organics from wastewater. The focus of this book chapter is to review extensive literature information about dyes, its classification and toxicity, various treatment methods and finally dye adsorption characteristics by various agricultural by-products solid wastes as adsorbents. The major objective of this chapter is to organize the scattered available information on the adsorptive removal of dyes from its aqueous solution by raw and treated agricultural by-products. Selectively widely used agricultural solid waste adsorbents in the removal of dyes have also been discussed in details here. Finally mechanism, kinetics and adsorptive behaviour of adsorbents under various physicochemical process parameters have been critically analysed and compared. Conclusions have been drawn from the literature reviewed and few suggestions for future research are proposed.

Chapter 9 - One of the most recent trends in environmental technology is the research turn to green chemistry. It is general accepted that one of the most promising techniques for wastewaters treatment is adsorption. In this basis, numerous adsorbent materials have been synthesized up to now. However, there is a novel concept nowadays, which promotes the use of materials with the lowest possible cost. valuation of them for removing of different pollutants (dyes, cations, anions, etc). In the last years, the instant coffee industry has experienced a constant growth as instant coffee has become one of the most popular kinds of coffee drunk by millions of people around the world. As a consequence, large amounts of coffee grounds, which are the solid residues obtained during the processing of coffee powder with hot water or steam to prepare instant coffee, have been generated worldwide (in the order of 6 millions of tons per year). This work investigates the use of coffee wastes or coffee-based materials as adsorbents for the treatment of wastewaters.

Chapter 10 - At the present time, the demand for energy, goods, and materials is surging because of advanced technology and population growth. However, earth’s resources are limited. For this reason, the issues concerning using resources effectively and converting them into energy are important. Taiwan creates a vast amount of agricultural waste every year, which is traditionally burned and buried. The authors do not reuse and recycle agricultural waste, and air pollution is increased when wastes are burned. Therefore, it is necessary to create methods for recycling and reusing agricultural wastes and to transform them into an energy source. This chapter is separated into two parts. The first part will convert agricultural waste into sugar. Agricultural waste is replete with wood fiber that can be reduced into sugar by a microbial method. The second part will use the biological hydrogen production capability of Clostridium acetobutylicum ATCC824, with sugar being added to the process. Also, this chapter used ultrasonic treatment for the production of biological hydrogen and calculated the natural frequency of ATCC824. The experiment was designed using the Taguchi method for increasing hydrogen production by using an ultrasonic treatment. Our results showed that the best combination is a temperature of 37 °C, 0.5 MHz ultrasonic frequency, 136 mW/cm2 ultrasonic intensity, 10 s exposure time, pH 7.5, and a bacterial concentration of 20%. The outcome of our research can be applied to the production of biomass energy and the research and development of ripening techniques for accelerating fermentable food with biomechatronics.

In: Agricultural Wastes ISBN: 978-1-63482-359-3

Editor: Camille N. Foster © 2015 Nova Science Publishers, Inc.

 
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