**1. Introduction**

The future energy demand is projected to rise further in accordance with ever-growing population. In addition to this, global energy consumption relies on non-renewable sources (like coal, petroleum, and natural gas) and those depleting day by day [1]. Moreover, the growth in greenhouse gas emissions from fossil fuel usage generates major menace to the climate. Therefore, it is imperative to search for environmentally and sustainable resources and utilize them to their full potential in light of biofuels. Biomass, as a renewable energy source, can be widely viewed as a promising alternative, because of its numerous applications, especially biofuels and bio-fertilizers [2]. There are several bio-refinery platforms that will be capable of processing biomass feed-stocks, which are the key intermediates between biomass feed-stocks and their value-added products. The bio-refineries usually add value to biomass supply chains through the production of various bio-based products. Selection of biomass has numerous advantages such as (a) abundant availability of precursor material; (b) environmentally friendliness; and (c) biodegradability and sustainability. In a typical bio-refinery, by using appropriate technologies, biomass by-products can be processed to generate various high-valued fuels. The bioenergy

#### **Figure 1.**

*Comparison of common thermochemical conversion techniques.*

sector has many major platforms, for example, syngas from gasification, fuel and fertilizer from anaerobic digestion, sugars from starch, extraction of cellulose, hemicellulose and lignin from biomass, solid carbon and bio-oil from pyrolysis, etc. A comparative ideology of thermochemical conversion technologies is illustrated in **Figure 1**.

Much research has been conducted on converting industrial and agricultural waste into valuable products [3, 4]. Still, this research topic is emerging because of its abundant scope for future energy demands. However, agricultural residue is prominent in energy conversion policies. Primarily, rice straw, rice husk, wheat straw, sugar cane bagasse, bamboo, areca nut shells, corn cob, coconut shells, etc., were used to produce energy fuels [5–9]. Apart from that, a vast range of oilseeds can be grown in India due to its diverse agro-ecological conditions and these all are coming under two major categories, such as edible oil seeds and non-edible oil seeds. The oil seeds are used for extraction of either edible oils or other purposes. In general, extraction of kg oil seeds can produce 250–350 g of oil [7], however, 650 g of residue seed cake is also obtained in the process of oil extraction [8].

Consequently, almost 65% of residue will available at the end of the extraction process. Some portion of extracted residue from edible seeds such as soybean, ground nut, flax seeds, sunflower, and etc., can be used as feed material for animal and the remaining unused. But, the residue from non-edible seeds contains toxic compounds, which limit their utilization as edible material. Hence, the oilseed residue (OSR) especially from non-edible seeds can be a potential material to produce biofuels [9], instead of unused. To convert oil seed residue (OSR) into valuable biofuels, thermochemical or bio-chemical conversion techniques can be used [10].

Thermochemical conversion involves thermal cracking of chemical organic bonds of biomass (OSR) into solids, gases, or liquid form [10]. Possible thermochemical conversion processes are torrefaction, pyrolysis, gasification, and liquefaction. The interest has been increasing day by day toward thermochemical conversion, because

*Production of Biochar from Oilseed Residue (Deoiled Cakes): State-of-the-Art DOI: http://dx.doi.org/10.5772/intechopen.114228*

it is user friendly and sustainable too. However, in bio-chemical conversion, specified bacteria (yeast) may be used to digest or convert biomass into different biofuels. Biochemical conversion includes anaerobic digestion, alcoholic fermentation, transesterification, and so on. Compared to bio-chemical conversion methods, thermochemical process has superior qualities. The final product obtained from thermochemical process has higher carbon content, lower volatile matter, and reduced contaminants. Also, it is more energy-efficient method and can mitigate the release of harmful emissions and pollutants. Hence, the subsequent categories in thermochemical conversion technique are discussed as follows.
