New replacements for natural gas

A great many gasification technologies exist - all of which were developed before the price of solar PV panels fell dramatically. 

 This fall in the price of solar PV panels  has ground-breaking implications for natural gas replacements. 

All plant material is assembled inside plant cells from water and carbon dioxide using solar energy. The process is photosynthesis and it stores solar energy. Bush fires burn ferociously because of the amount of solar energy stored in plant material such as leaves, wood and grass. 

All reactions that store solar energy in plant material are minor variations of:

• One molecule of carbon dioxide from the air is split into a carbon atom and an oxygen molecule, 
• The oxygen molecule is released into the atmosphere, and 
• The carbon atom is added to a cross-linked molecule of plant material (such as cellulose or lignin) together with one molecule of water.

This simplified model could be represented:

(CH₂O)_n + CO₂ + H₂O =>  (CH₂O)_(n+1) + O₂

The resulting plant material can be considered approximately to be cross-linked collections of carbon atoms with one water molecule for each carbon atom. 

Because of the collapse in the price of solar PV panels, all existing methods of making replacements for natural gas from plant material use some of the energy embedded in the plant material, creating carbon dioxide and methane. 

It is inevitable that the methane created embodies LESS energy than was present in the plant material. 

The low cost of solar PV panels crucially changes the feasible processes for making methane from plant material. 

The plant material can be reacted with pure hydrogen, and NOT oxygen, to make methane and water vapour at a high temperature. 

The water vapour can be split into hydrogen and oxygen molecules with high-temperature electrolysis with electricity generated solar PV panels. 

The hydrogen produced by high-temperature electrolysis of water vapour is reacted with more plant material, continuing the conversion of all the available plant material is converted into methane and oxygen. 

There is no carbon dioxide produced, so no carbon dioxide storage is required and the cost of storing carbon dioxide is avoided. 

The methane produced embodies the energy that was available in the plant material PLUS additional energy from the solar PV panels used to electrolyze water vapour into hydrogen and oxygen. 

 

Further reading: "Coupling hydropyrolysis and vapor-phase catalytic hydrotreatment to produce biomethane from pine sawdust" at https://pubmed.ncbi.nlm.nih.gov/37423544/ .