Gasification is almost as ancient as combustion, but it is less developed because commercial interest in it has not been as strong as in combustion. However, there has been a recent surge of interest in conversion of biomass into gas or liquid due to three motivating factors:

• Renewability benefits

• Environmental benefits

• Sociopolitical benefits

1.4.1 Renewability

Fossil fuels like coal, oil, and gas are good and convenient sources of energy, and they meet the energy demands of society very effectively. However, there is one major problem: Fossil fuel resources are finite and not renewable. Biomass, on the other hand, grows and is renewable. A crop cut this year will grow again next year; a tree cut today may grow up within a decade. Unlike fossil fuels, then, biomass is not likely to be depleted with consumption. For this reason, its use, especially for energy production, is rising fast.

We may argue against cutting trees for energy because they serve as a CO2 sink. This is true, but a tree stops absorbing CO2 after it dies. On the other hand, if left alone in the forest it can release CO2 in a forest fire or release more harmful CH4 when it decomposes in water. The use of a tree as fuel after its life provides carbon-neutral energy as well as avoids greenhouse gas release from deadwood. The best option is new planting following cutting, as is done by some pulp industries. Fast-growing plants like switch grass and Miscanthus are being considered as fuel for new energy projects. These plants have very short growing periods that can be counted in months.