Biomass gasification using organic materials (ideally waste materials which would otherwise go to landfills) is the best way to either directly produce hydrogen from the “syngas” it produces, or generate electricity into the local power grid, from which users can create hydrogen in their homes, and factories. If society is to become hydrogen economy based it will have to be done in a sustainable manner without adding to the production of greenhouse gases, and as a result to global warming.
A few years ago the technical news press were full of the idea of a hydrogen economy. The idea was, and still is a sound one, especially as far as the pressing need to reduce urban pollution which in so many cities is reaching crisis point largely due to vehicle emissions. The worst emissions are from motor vehicle exhausts and especially dangerous are the small soot particules from deisel vehicles.
What the early proponents of hydrogen powered vehicles did not appreciate is that although the cities would be much cleaner if all vehicles were hydrogen fuelled and emitting only water, the production of the hydrogen (often overnight in the garage using electric power and water) would entail inefficient use of electrical power. As most of our electricity in all but a few nations is created from carbanaceous (climate change inducing) fuels the idea of hydrogen powered transport would be in danger of accentuating climate change. Hence, one problem would have been solved but only at the expense of another much bigger one.
However, as biomass gasification, done in the right way, can be fully sustainable it does give society the opportunity to have its cake and eat it. That is clean sustainable hydrogen for our city's vehicles and a clean hydrogen economy overall.
The concept of mainstream large scale commercial gasification technology is that biomass is converted into a gaseous mixture of hydrogen, carbon monoxide, carbon dioxide, and other compounds by applying heat under pressure in the presence of steam and a controlled amount of oxygen (in a unit called a gasifier). In the process the molcules forming the biomass are broken apart chemically by the heat, steam, and oxygen to which they are subjected. This sets into motion chemical reactions that produce a synthesis gas, or "syngas". This gas although it starts as a mixture of primarily hydrogen, carbon monoxide, and carbon dioxide, it can then be shifted through further reactions to increase the hydrogen gas content. At the same time the operator can reduce the carbon compounds and finally the carbon dioxide can be scrubbed out and captured for long term storage underground to minimise and even reduce global warming.
The hydrogen gas is actually produced by steam during the gasification of charred cellulosic material. The yield from steam gasification increases with increasing water to sample ratio.
Hydrogen production systems based on thermochemical gasification of biomass typically therefore consist of the following basic steps:
- pre-treatment
- gasification
- gas cleaning
- upgrading and separation.
The development of the technology is progressing and in essence depends on the successful integration of these steps. Ideally, technical and economic analysis is carried out to select the optimum technology for the available feedstock in order to produce a synthetic gas product of the necessary quality for the target application.
If you are wondering whether to support the introduction of a biomass gasification plant in your area, this is something which you should strongly support for the environmental advantages of this process.
