1.1 Definition

Bioenergy is energy derived or obtained from any fuel that is derived or originated from biomass which includes recently living organisms and their metabolic by-products. Similarly, biofuels are defined as fuels made from biomass resources, or their processing and conversion derivatives [1]. Biomass is defined as all plant and animal matter on the Earth’s surface. Therefore, harvesting biomass such as crops, trees, or dung and using it to generate heat, electricity, or motion, is bioenergy [2]. Biomass is a very broad term that is used to describe materials of recent biological origin that can be used as an energy source or for their chemical ingredients. According to this definition, biomass includes crops, trees, algae, and other plants as well as agricultural and forest residues. It also includes many other materials that are regarded as waste by most people, including food and beverage manufacturing efflu­ents, sludges, manures, industrial organic by-products, and organic fraction of household waste [2]. The word "recent" in the defining statements of bio­mass is of significance, because it eliminates any logical ground for fossil fuels to be considered as such.

Biomass has a number of different end uses such as heating (thermal energy), power generation (electrical energy), and transportation fuels. The term bioenergy is usually used for biomass energy systems that produce heat or electricity, whereas the term biofuels is typically used for liquid fuels for transportation [2]. For example, biofuels include corn ethanol, cellulosic ethanol, biodiesel, algae diesel, biomass-derived methanol, biomass-derived Fischer-Tropsch fuels, and more.

Historically speaking, biomass is the oldest fuel known to humans in all regions of the world. In the current world, biomass is a clean and renewable fuel source that can produce heat, power, and transportation fuels. In the future world, biomass will be a sustainable energy source whose utilization will have little or minimal impact on the environment and climate change.

Biomass may be considered as a form of stored solar energy that is cap­tured through the process of photosynthesis in growing plants. Utilizing biomass as a biofuel or bioenergy source means that carbon dioxide (which
was captured from the air by growing plants) is released back to the air when the biofuel is eventually combusted. Therefore, the system based on biomass energy is carbon neutral, or at least close to being carbon neutral. The term carbon neutral means removing as much carbon dioxide from the atmosphere as we put in, thus leaving a net zero impact on the atmospheric carbon dioxide amount.