**1. Introduction**

Waste is unavoidable as long as human continues to live and engaged in economic activities. Most of the waste generated are either recycled or dumped in landfills, where it decomposes over a period of decades or even centuries. More than 50% of the energy content of municipal

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

solid waste (MSW) originates from biogenic matter both in developed and developing countries. However, the disposal of the organic fraction of waste in landfill has dire consequences on the environment including the generation of methane, which can pose a threat or contribute to the greenhouse effect. Some landfills have sought to collect methane, which may be used for fuel; nonetheless, the conversion to methane takes place on long time scales, wastes much of the internal energy of the waste, and is rather ineffective in recovering much of the available energy content of the waste.

from biological sources is refers to as biogenic carbon. However, biodegradable waste with high moisture content is often difficult to utilize the full energy potential of the waste due to

Bio-Drying of Biodegradable Waste for Use as Solid Fuel: A Sustainable Approach for Green…

http://dx.doi.org/10.5772/intechopen.77957

91

The carbon content of any waste depends on the waste components. The relative proportions of biogenic and fossil carbon also depend upon the waste components, as do other important factors such as the calorific value or energy content. The calorific value of waste is how much (chemical) energy is stored in the waste per tonne that could potentially be converted into useful electrical or heat energy when burned. The term calorific value is synonymous to the heating value. The higher the calorific value, the more energy can potentially be captured from the waste. Different waste components have different individual calorific values i.e. food waste tends to have a relatively low value due to its high water content while plastic has much higher energy content. The variation of different proportions of these wastes will therefore significantly impact on the overall calorific value. This brings to forth the composition of waste as it affects many of the overall properties of the waste including both the calorific value and the biogenic content of the fuel.

According to literature, a number of pre-treatment technologies such as Mechanical Sorting Plant, Mechanical Biological Treatment (MBT) and Mechanical Heat Treatment (MHT) have been research and developed. These treatment techniques apply mechanical sorting and processing techniques to remove recyclates, moisture, and shred and/or homogenize the waste to create some kind of refuse derived fuel (RDF) or solid recovered fuel (SRF). However, in this study, bio-dried material obtained from bio-drying process was used to ascertain the fuel properties of the final product. Bio-drying technology, as a waste to energy conversion technology, aims at removing water by microbial activities, is regarded as a good option in reducing the moisture content of wet organic wastes [16]. The essence of this technology is to reduce the volume of waste sent to landfills which in turn will benefit short time storage and

Whereas some technologies can cope with a broad range of calorific values and water content of the waste fuel, others require much more specific levels to operate efficiently. Additionally, the biogenic content of waste also affects the technologies that are suitable to deliver environmental benefits. Thus, having a good understanding of composition in terms of calorific value and biogenic content is essential for planning and designing energy from waste solution. Hence, the main objective of this research is to characterize bio-dried material produced by bio-drying from biodegradable/biogenic and non-biodegradable/non-biogenic materials

Bio-drying, a concept similar to composting, aims at removing or reducing water from biodegradable waste with high water content and increasing the treatability and subsequent utilization value of the bio-dried material. In other words, it is the utilization of the heat released during the decomposition of biodegradable waste in order to reduce the moisture content and partially stabilize the waste. The removal or reduction of moisture contents in bio-drying process

transportation, and provides alternative energy source as fuels for industries.

based on biogenic and energy content of the waste material.

**2. Bio-drying process**

its limited lower heating value (3–6.7 MJ/kg) [15].

The search for sustainable solutions for biodegradable waste management represents a challenge not only for the waste management sector but also for the agricultural and industrial sectors. The enormity of this problem intertwined with the aforementioned issues associated with landfilling led to the introduction of the Landfill Directive of 1999 by the European Union (EU). According to the Landfill European Directive 1999/31/EC, member states are required to only landfill wastes that have been preliminary subjected to treatment or require a phased reduction in the amount of biodegradable waste disposed of to landfill [1]. Biodegradable waste refers to any waste that is capable of undergoing anaerobic or aerobic decomposition, such as food and garden waste, and paper and paperboard [2]. Similarly, the Energy Information Administration (EIA) of the Environmental Protection Agency (EPA) of the United States defines biodegradable/biogenic waste as any waste produced by biological processes of living organisms. Based on the definition by the EU and inter alia [3, 4], it is clearly that the concept of biodegradable waste is wide and regards not only the production of food waste at household level; however, it includes all agricultural waste. The UNEP estimates that the decay of organic proportion of municipal solid waste contributes about 5% of global Greenhouse Gas (GHG) emissions annually [5]. In curbing this menace, a number of technologies for waste treatment such as composting (organic fertilizer), landfilling, anaerobic digestion and thermal methods have been developed [6]. However, the implementation of some of these techniques has been hindered due to the high implementation costs and other related environmental concerns.

By virtue of these concerns and in line with the new European Union Landfill Directive (1999/31/EC), this has motivated research into the development of technologies to reduce the impact associated with landfilling of waste [7–9]. Consequently, composting has been identified as an alternative method for transforming the organic fraction of waste into a potentially safe, stable and sanitary product that can be used as a soil amendment or an organic fertilizer [10]. Nonetheless, high operational cost, low quality of final product and long residence time (30-50 days) associated with composting have hindered wider application of this technology as inept for waste treatment [11, 12].

Energy from the biogenic part of waste is considered as one of a number of options that either have the greatest potential to help in a cost effective and sustainable way in waste management. Although, energy recovery may not be the first option according to the waste hierarchy, this option becomes paramount when the material is generated and considered as waste [13]. The EU directive categorized waste incineration either as a disposal or energy recovery technology depending on the energy efficiency of the incineration plant [14]. Thus, the operation and design of the aforementioned process highly require the knowledge of its thermal properties or the biogenic fraction of the waste. The carbon stored in waste originated from biological sources is refers to as biogenic carbon. However, biodegradable waste with high moisture content is often difficult to utilize the full energy potential of the waste due to its limited lower heating value (3–6.7 MJ/kg) [15].

The carbon content of any waste depends on the waste components. The relative proportions of biogenic and fossil carbon also depend upon the waste components, as do other important factors such as the calorific value or energy content. The calorific value of waste is how much (chemical) energy is stored in the waste per tonne that could potentially be converted into useful electrical or heat energy when burned. The term calorific value is synonymous to the heating value. The higher the calorific value, the more energy can potentially be captured from the waste. Different waste components have different individual calorific values i.e. food waste tends to have a relatively low value due to its high water content while plastic has much higher energy content. The variation of different proportions of these wastes will therefore significantly impact on the overall calorific value. This brings to forth the composition of waste as it affects many of the overall properties of the waste including both the calorific value and the biogenic content of the fuel.

According to literature, a number of pre-treatment technologies such as Mechanical Sorting Plant, Mechanical Biological Treatment (MBT) and Mechanical Heat Treatment (MHT) have been research and developed. These treatment techniques apply mechanical sorting and processing techniques to remove recyclates, moisture, and shred and/or homogenize the waste to create some kind of refuse derived fuel (RDF) or solid recovered fuel (SRF). However, in this study, bio-dried material obtained from bio-drying process was used to ascertain the fuel properties of the final product. Bio-drying technology, as a waste to energy conversion technology, aims at removing water by microbial activities, is regarded as a good option in reducing the moisture content of wet organic wastes [16]. The essence of this technology is to reduce the volume of waste sent to landfills which in turn will benefit short time storage and transportation, and provides alternative energy source as fuels for industries.

Whereas some technologies can cope with a broad range of calorific values and water content of the waste fuel, others require much more specific levels to operate efficiently. Additionally, the biogenic content of waste also affects the technologies that are suitable to deliver environmental benefits. Thus, having a good understanding of composition in terms of calorific value and biogenic content is essential for planning and designing energy from waste solution. Hence, the main objective of this research is to characterize bio-dried material produced by bio-drying from biodegradable/biogenic and non-biodegradable/non-biogenic materials based on biogenic and energy content of the waste material.
