**1. Introduction**

Over the past few decades, the world has seen a rapid increase in energy demand and consumption. Currently, fossil fuels (oil, natural gas, and coal) are the primary source of global energy supply. The combustion of fossil fuels releases greenhouse gases into the atmosphere, resulting in global warming, environmental pollution, and climate change. Due to higher prices and a finite supply of fossil fuels and to reduce greenhouse gas emissions and mitigate climate change, more attention has been given to finding a sustainable long-term alternative to fossil fuels. As a result, renewable energy resources (such as biomass, solar, wind, geothermal, and tidal) are gaining popularity. Biomass, available abundantly at a relatively low cost, is

considered a promising alternative renewable energy source to substitute for fossil fuels. It is a clean, environmentally friendly, and carbon-neutral source of energy. Burning biomass or fossil fuel releases carbon dioxide (CO2), a greenhouse gas. However, when biomass burns, it releases CO2 back into the atmosphere that the plants have absorbed recently by photosynthesis during the growth process producing biomass. Thus, burning biomass does not add to the total CO2 inventory of the earth and is considered carbon neutral. Nevertheless, the overall biomass chain, including planting, harvesting, processing, and transporting, needs to be considered for true carbon neutrality of biomass. In addition, burning biomass releases a variety of pollutants, including carbon monoxide (CO), nitrogen oxides (NOx), and particulate matter [1–4].
