Charcoal for renewable energy

Clean charcoal, from freshly havested sources, has the potential to be used as another type of renewable energy. In contrast to solar and wind, it can be stored. It also provides another mode of transmission: transport by land or sea, rather than as electricity by the grid or hydrogen through pipes.

It can be used in a variety of ways:

• As a fuel for heating and cooking. It is far less polluting than wood, which is used in less developed countries on a large scale. Could be used in trendy wood burning stoves with far less atmospheric pollution.
• Thermal power generation. Compared to Drax, production would be local to the source, where most of the polluting byproducts are removed and monetised, and the weight and volume of feedstock, charcoal rather than wood, is reduced.
• Small efficient thermal power generators may be feasible by gasifying the charcoal with steam (water gas) and using a novel turbine.
• If these power generators can also have a rapid startup they can be used to compensate for the variability of other renewable energy sources.
• They would enable local CHP, where the size and location of the plant can be selected to minimise cost of transport of charcoal and the cost of delivery of heat.

Dirty charcoal

The feedstock for urban pyroysis plants would be not freshly harvested and could include domestic rubbish, industrial food waste, disposed medical waste, scrap plastic, and used timber products from demolished buildings and disposed furniture. It would contain contaminants, making it unsuitable for use as a renewable fuel or terra preta. But it can be pyrolysed and yield bio-oil and energy.

Dirty charcoal could be useful:

• The process itself will be removing contaminants from the enviroment.
• Decontamination using charcoal as an absorbant. This will make it even dirtier.
• For industrial uses, like steel production, that depend on coal, dirty charcoal would be a non-fossil substitute.
• As aggregate for a light weight, thermally insulation building material.

The idea is to ramp up the rate of removal of atmospheric carbon by this means until there is a surplus for final sequestration. A final process is carried out to distroy organic contaminants and lock in other contaminants. The dirty charcoal is mixed with glass forming minerals and heated. Glasses are good solvents for any minerals that have been absorbed and lock them into the glass structure. The result will be an inert, stable coke-like material that can be safely disposed of by spreading it out over the earths surface. Ocean trenches and river deltas might be good places to dump it.