Over recent years, recycling and sustainable energy have become increasingly important to businesses, to do their part for the environment, and be seen as an environmentally conscious business.
Some of the processes currently in place for generating sustainable energy are new and innovative designs – others, however, have been around for centuries. The likes of wind and hydropower are both well known and effective forms of generating energy, but there are other means, which have been around for just as long, that are only just starting to snowball in popularity, in the renewable energy world.
Gasification, a process where a set of chemical reactions convert a carbon-containing feedstock into a synthetic gas, has been around for hundreds of years (as early as the 1800’s). Recently it has seen a spike in popularity.
What is it, and how does it work?
Gasification process takes a limited amount of oxygen, a carbon-containing feedstock (such as coal, wood, gas or biogas or even waste) and steam and cooks them under intense pressure to generate the synthetic gas or syngas.
Coal Gasification
Using coal in the gasification process doesn’t require a boiler, but instead makes full use of a gasifier which is a cylindrical pressure vessel. The coal will enter the vessel from above, with steam and oxygen being pumped in from below. The gasifier will then heat up, and can reach temperatures of up to 1,400 degrees Celsius – this level of heat causes the coal to go through various chemical reactions.
Firstly, the oxidation of the coal’s carbon components releases heat and helps to further fuel the gasification process and reaction. Pyrolysis occurs as the coal’s more volatile matter breaks down into several different gasses and leaves behind char, which is a charcoal like substance. Syngas is then produced, as reactions transform the remaining carbon in the char to a gas-like mixture.
The main output of Syngas is hydrogen and carbon monoxide – these can both be combusted, cleanly, in gas turbines to produce electricity. The other option is to convert the syngas substance to a natural gas, methane. This occurs when cleaned gas is passed over a nickel catalyst, which causes carbon monoxide and carbon dioxide to react with the hydrogen and thus form methane.
Wood Gasification
Whilst using coal as part of the gasification process is considered to be fairly clean, it still uses a non-renewable fossil fuel as its core ingredient, which will eventually come back to bite you. Wood, on the other hand, doesn’t comes with this problem – it makes use of biomass gasification, which is very much the same as coal gasification, except for it is more renewable and can take a variety of different feedstock.
Agricultural residues and food waste
Energy crops, often grown specifically for the purpose of biomass gasification feedstock
Forestry leftovers(wood, bark, even deadwood)
Urban wood (wood based debris from construction sites such as pallets or scaffold walkways)
The simple process
The feedstock is inserted into a gasification vessel
The vessel is heated
A very small amount of air/oxygen is pumped into the vessel
This breaks up the molecules in the feedstock and recombines them to form Syngas
Syngas can be used to make fuel, chemicals, fertilisers and products as well as electricity