**1. Introduction**

The reserves of non-renewable energy sources (coal, crude oil, natural gas) gradually get exhausted and their price continually increases. Nevertheless, they cover about four-fifth of the energy consumption [1].

© 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.

In the last four decades, researchers have been focusing on alternate fuel resources to meet the ever increasing energy demand and to avoid dependence on crude oil [2].

**2.1. Biomass**

amount of CO2

and H<sup>2</sup>

complicated.

handling [12].

heating value [13].

**2.2. Thermal conversion processes**

and tar components and a carbon rich solid residue [4].

CO2

neutral carbon cycle of CO2

O [7].

Biomass can generally be defined as any hydrocarbon material which mainly consists of carbon, hydrogen, oxygen and nitrogen. Sulfur is also present in less proportion. Biomass resources include many natural and derived materials such as woody and herbaceous species, wood wastes, bagasse, agricultural residues, waste paper, municipal solid wastes, sawdust, biosolids, grass, food wastes, animal wastes, aquatic plants, and algae, etc. Woody materials are preferred among biomass resources because they contain much higher energy value. Most important feature of biomass is its inherent climate neutral behavior. When biomass is grown in a sustainable way, during the life cycle of biomass production and application, no net

is stored in return in the biomass resource through photosynthesis, which means a climate

energy source replacing fossil fuels because it is produced in nature by photosynthesis from

On the other hand, some biomass properties are inconvenient, particularly its high oxygen content, a low heating value, a hydrophilic nature and high moisture content. Also, the energy accumulation to biomass through photosynthesis has known to be a process of low energy efficiency. The overall energy efficiency from solar energy to biomass energy is 1–3% [8]. Typical disadvantages of biomass are its tenacious and fibrous structure and its heterogeneous composition that makes process design and process control more

Biomass has unique characteristics that necessitate pre-processing before it can be stored, transported or used in various applications. Unlike fossil fuels which are mined at one location, biomass is often available seasonally in small quantities scattered over many locations [9]. Biomass is highly heterogeneous in quality and nature, and is available in low energy density form [10]. It has relatively high moisture content and consequently lower heating value compared to fossil fuels [11]. It is therefore often needs to be pre-treated to improve

Burning biomass in an oxidative environment is the oldest conversion process practiced by man. Combustion, however, does not intend to produce value-added products in the form of fuels, chemicals or materials, as other thermochemical conversion technologies, but only

Thermal conversion processes can be categorized into combustion, gasification, pyrolysis and the emerging torrefaction technology according to the operating conditions. The products of the thermochemical processes are divided into a volatile fraction consisting of gases, vapors

released during the utilization of biomass

http://dx.doi.org/10.5772/intechopen.76100

45

. Biomass is considered as an environmentally friendly alternative

Development of Torrefaction Technology for Solid Fuel Using Renewable Biomass

emits into the atmosphere. The CO2

Among different sources of renewable energy, biomass residues are the most potential raw material due to their inherent capability to store solar energy and amenability to subsequent conversion to convenient solid, liquid and gaseous fuels. Further, biomass is a renewable source of carbon through a global carbon cycle and can be a source to make many chemicals.

With serious concern about deforestation as one of the causes of global warming, especially in developing countries, and need for reforestation to maintain global ecological balance, increasing demand is being made for proper utilization of agro and forestry biomass residues to play the role previously carried out by wood.

Torrefaction is a recently well-known technology which can change biomass properties to become a higher energy quality biofuel. From a viewpoint of chemical components, torrefaction process comprises mainly the removal of oxygen to yield a final solid product. The torrefied biomass product contains a lower O/C ratio compared to the original raw biomass.

Torrefaction occurs through the heating of biomass below 300°C in the absence of oxygen, where moisture and volatile materials are lost. It was first applied in 1939, then in 1984 but forgotten until recently. Published papers and patents issued were from late 2000s to present. It can convert biomass wastes to solid fuel affordably without complications.

The Philippines is mainly an agricultural country with a land area of 30 million hectares, 47% of which is agricultural. The total area devoted to agricultural crops is 13 million hectares distributed among food grains, food crops and non-food crops. Among the crops grown, rice, coconut and sugarcane are major contributors to biomass energy resources. The most common agricultural residues are rice husk, rice straw, coconut husk, coconut shell and bagasse [3].

In order to utilize agricultural crop residues and to improve its biomass properties, there is a need to create new knowledge and apply it to be more productive focusing on creativity and innovation. Agricultural crop residues that are abundant in the Philippines such as coconut leaves [4, 5], cogongrass [5], and rice husk [5], were utilized to produce solid fuel by torrefaction for use as alternative source of energy. The design of the torrefaction process based on the biomass characteristics was researched and developed.
