Southwest Environmental Limited

Carbon Sequestration Consultants 

Southwest Environmental Limited can offer consultancy services for Carbon Sequestration & Carbon Storage Projects. We can also design and make lifecycle assessment for proposed sequestration & storage schemes.

Whilst we (humanity) reduce our emissions through efficiency measures and switching to renewables. We also need to consider carbon storage as a means of removing CO2 from the atmosphere.

Most of the below methods are well established, and ready to go to work. All we need is a price for carbon, so that investors can determine accurately what their return will be.

There are numerous methods by which this can be accomplished:

Trees

The most well known carbon sequestration technique is tree planting. A well managed and documented forest maintain in perpetuity, with little or no thinning will sequester around 1000 tons of CO2 per hectare over 80 years.

Extra Benefits

What's more there are also bio-diversity enhancements, and many other positives such as soil retention, water cycle improvements &  run-off reduction. Trees are extremely effective at sequestering carbon because of the quantum tunneling mechanism utlised by photosynthesis. Forest Albedo is also a factor. Ranging from 7% to 20%. Deciduous trees have a higher albedo, and this is an advantage in combating global warming, although this needs to be carefully considered against growth rates.

Problems

We would need a forest to remain in place indefinitely, or for long as it takes to stabalise climate. That is a big ask. And we don't even know what affect the increasing temperatures will do to tree health:

"Diseases such as ash dieback – a fungal disease that impacts numerous species – and acute oak decline, are among the key threats to UK woodlands that have been exacerbated by the climate crisis".

There is also a delay in the sequestration process. Sequestration rate of Carbon is slow for the first 15 years, with increased up take from 15 years to 50 years. Sequestration rate then begins to slow up to 100 years.

In relation to the Newland Oak Cyril E Hart described the tree in 1966 as having taken "200 years to grow, 200 years to exist, and 200 to die".[9]

So based on this anecdote, we can say very roughly that a well founded Oak tree may sequester the carbon is captures up to the age of 200 years. But then owing to decay, disease etc. the carbon will begin to be released. Other species may not last as long. Alders, and Beech for example may only last half as long.

The question as to whether this period of sequestration is long enough is yet unanswered, we will not know until we have made meaningful start on reducing our emissions.

Carbon Capture and Storage

Carbon Capture and Storage is quite a recent idea, perhaps around 10 years old. The Environment Agency released a template permitting process for this type of facility back in 2012. The idea likely preexisted this. There are a number of type of Carbon Capture and Storage:

Direct Capture - Combustion

This is a way of sequestering carbon indirectly as a byproduct of another process. For example burring of coal or bio mass. 

Pre-Combustion Capture

"A pre-combustion system involves first converting solid, liquid or gaseous fuel into a mixture of hydrogen and carbon dioxide using one of a number of processes such as ‘gasification’ or ‘reforming’"

Post Combustion Capture

"CO₂ can be captured from the exhaust of a combustion process by absorbing it in a suitable solvent. This is called post-combustion capture. The absorbed CO₂ is liberated from the solvent and is compressed for transportation and storage. Other methods for separating CO₂ include high pressure membrane filtration, adsorption/desorption processes and cryogenic separation."

Oxy-Fuel Combustion

"In the process of oxy-fuel combustion the oxygen required is separated from air prior to combustion and the fuel is combusted in oxygen diluted with recycled flue-gas rather than by air"

Direct Capture - Sorbtion

For many years CO2 scrubbers have been used in Submarines, Rebreathers and Space Ships to provide breathable air. These scrubber filters are comprised of:

• Amine Scrubbers

• Zeolites such as Sodium Hydroxide or Lithium Hydroxide

• Activated Carbon

• Algae Bio-Reactors

Once manufactured and installed air is forced through the scrubber material, and a certain percentage of the carbon is removed.

The main down side of these method is energy demand, and the capital carbon involved in the manufacture of the sorbtion materials.  However, with the decreasing cost of renewables it may well be possible

Storage

This the interesting part. Once the carbon has been captured we have to find something to do with it. So it cannot get back in to the atmosphere.

Inspiration from Nature