Farms in Australia have an opportunity to earn income from crop and animal waste streams. Queensland in particular has a network of coal seam gas pipelines crossing farmland. These could be exploited to make and sell bio-methane on farms with renewable energy.
This avoids the need for construction of connections to Australia's electricity grid, and the wait for approval to connect solar and wind farms to the grid.
One tonne of bio-methane stores approximately 55 gigajoules of energy. It consists of 750 kilograms of carbon and 250 kilograms of hydrogen.
Biomass created on farms, whether crop waste or animal waste, is a mixture of carbon, hydrogen and oxygen. It represents solar energy stored by photosynthesis in plants that have removed the carbon from the atmosphere.
Biomass containing carbon and hydrogen to make one tonne of bio-methane would also contain about two tonnes of oxygen.
If the biomass was, say, sawdust, the quantity required to make one tonne of bio-methane would be two tonnes dry weight with a moisture content of about 30 percent - equal to one tonne of water.
To start the process of bio-methane production, an initial supply of hydrogen is needed.
After the process has begun, steam that is a by-product of making bio-methane would be converted to hydrogen and oxygen in a steam electrolyser using renewable energy.
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The hydrogen made in this step would then be used to create more bio-methane, and more steam. An external hydrogen supply is not needed to continue the production of bio-methane.
Also note that no supply of water is needed. The process obtains the water for electrolysis from the biomass that is used to make bio-methane.
Recent articles on the process include:
- Methane Production from the Pyrolysis–Catalytic Hydrogenation of Waste Biomass, and
- Hydropyrolysis to produce biomethane from pine sawdust.
This approach to making bio-methane stores renewable energy from two sources:
- The solar energy stored by the plants that made the biomass via photosynthesis, and
- The renewable energy from wind and/or solar photovoltaic panels that splits the hydrogen from oxygen in the steam electrolysis step.
Other advantages include:
- There is no need to wait for the cost of making "green hydrogen" to become viable.
- There is no need to wait for the development of hydrogen supply lines to be built.
