**1. Introduction**

Post harvest agricultural wastes are promising materials for generating renewable and eco-friendly energy source and raw materials for chemical and allied industries. Agricultural wastes serving as a potential alternative source of energy and starting renewable materials for industrial productions will definitely bring about reduction in demand for non-renewable petrochemical feed stocks often used by most chemical industries today. Other benefits are efficient carbon cycle and reduction in carbon(iv) oxide (CO2) emissions [1]. Among the agro-wastes, plantbased (lignocellulose) materials are most abundant and disposed indiscriminately, where by constituting nuisance to the environment. Plant-based agricultural wastes are called lignocellulosic materials because their compositions are majorly of lignin and cellulose. Others are hemicellulose, pectin, wax, oil and inorganic matters [2]. These compositions of plant vary from one plant to another. Other factors that

**Figure 1.** *Various forms of biomass conversion techniques.*

contribute to the variation in compositions are age of the plant, processing methods, geological and climatic factor [3, 4]. The plant-based agro-wastes worked on by researchers as energy source and feed stocks for chemical and allied industries are sugarcane bagasse, cola nut pod, cocoa pod, moringa seed pod, oil palm empty fruit bunch, almond leaf, *Bridelia ferruginea* bark, elephant grass etc. [5–9]. Conversion of these agro-wastes to energy source and starting materials for chemical and allied industries will bring a turn around to high dependence on ever depleting and price fluctuating petrochemicals. This will in turn generate wealth from wastes; creating jobs for teaming unemployed youths and keep our environments clean [3].

Several technologies deployed for converting agro-wastes to energy source and precursors for chemical and allied industries are hot acid carbonization by dehydration and anaerobic digestion. Others that are thermally based are torrefaction, pyrolysis, combustion, gasification and hydrothermal process. Among these technologies, pyrolysis is most preferred, because the products which are solid, liquid and gas can easily be stored, transported and handled [10]. **Figure 1** shows summary of various biomass conversion techniques and products obtained. Pyrolysis is a composition of two Greek words, split able into 'pyro' meaning fire and 'lysis' means degradation into many parts. Therefore, pyrolysis can be defined as thermochemical degradation of biomass into biochar (solid carbonaceous material), bio-tar, bio-oil (condensable vapor) and non condensable gases (syngas) in absence or very limited supply of oxidizing agents [10, 11]. Depending on degradation temperature, heating rate and vapor retention time, pyrolysis can be classified as slow, fast or flash pyrolysis. The choice of any of the pyrolysis techniques depends on desired or targeted products [10].
