**Abstract**

Bioenergy, when compared to traditional fossil fuels, offers clear benefits due to its renewable nature and enormous supply, and so plays a critical role in ensuring energy stability while minimizing net greenhouse gas emission. However, the advancement of bioenergy can produce major environmental changes, the extent of which is unknown. This chapter highlights the overview of bioenergy, available technologies for bioenergy production, environmental implications, challenges, prospects and future work consideration for the successful transition to bioenergy economy. Consequently, a global bioenergy sector producing substantial amount of energy would be required for the transition to a low-carbon energy economy while meeting rising future energy demands.

**Keywords:** bioenergy, biofuel, biogas biophotolysis, combustion, fermentation, gasification, hythane, liquefaction, pyrolysis, trans-esterification

### **1. Introduction**

The world economy has developed within a concept that is heavily dependent on fossil fuel (coal, oil, and natural gas), which supply the vast large proportion of the substrate utilized in the synthesis of fuels and chemicals. The global energy utilization is increasing tremendously, and fossil fuels currently provide around 88% of the global energy. However, due to their finite reserves and non-renewable nature, the long-term exploitation of these limited resource is unreliable [1]. According to projections, the world's energy requirement will rise by a factor of two or three throughout this century [2]. Similarly, the quantities of greenhouse gases (GHGs) in the environment are quickly increasing, with CO2 releases from fossil fuels being the main significant contribution to this increase. It is necessary to cut greenhouse gas emissions to less than half of world emission rates of 1990 as to mitigate the consequences of global warming and climate change [3]. Another significant global concern is energy supply stability, which is complicated by the fact that the vast majority of known traditional oil and gas reserves are located in politically unstable countries.

Bioenergy is an alternative form of basic energy that offers an opportunity for greenhouse gas (GHG) reductions, provided that the feedstocks are exploited from a renewable source and that effective bioenergy technologies are utilized. It is possible that increasing the amount of electricity generated by this form of energy may help to achieve the Framework Convention on Climate Change (FCCC) goals of stabilizing atmospheric concentrations of greenhouse gases below toxic concentrations in the future. Biomass is an alternate provider of chemical feedstock and energy, and biorefining biomass is equivalent to petroleum processing [3, 4]. "A biorefinery," according to the National Renewable Energy Laboratory (NREL), is described as "a system that incorporates biomass transformation operations and technology to synthesize fuels, electricity, and chemicals from biomass" according to National Renewable Energy Laboratory. Furthermore, bioenergy obtained from biological materials has historically been considered to be a significant form of energy that will help to lessen reliance on fossil fuels [5].

The notion of biorefineries is a sustainable strategy to the biomass transformation into useful products that may easily substitute fossil oil refineries, which are used to generate a number of fuels, chemicals, and other by-products from crude oil. Using biomass as a substrate, biorefining is the method of refining a variety of bio-based products such as chemicals, fuels, and power, all of which are utilized as end products. Biofuels are liquid or gaseous fuels that are predominantly derived from biomass. They can be employed to substitute or supplement diesel, gasoline, or other fossil fuels in a variety of uses, including transportation, stationary, portable, and other purposes. Biofuels, such as biodiesel, bioethanol, biogas, and bio-oil, are the most important products of the biorefining industry. When likened to conventional fossil fuels, biofuels have outstanding characteristics in aspects of renewability, relatively clean refining, locally distributed resources, biodegradability and non-hazardous, clean combustion, a favorable economic implication, improved fuel economy, reduced reliance on petroleum oil, and improved health advantages [6, 7]. The application of green technology-based biorefinery approach results in a crude oil non-reliance future, with a prosperous industry dependent on organic and environmentally friendly raw material including agricultural residues, cheese whey, household residues, forest residues, and algae. The advancement in technology makes it possible to produce biofuel from waste raw material in an efficient manner.
