Capture Carbon

using the Tawi Stove

Why do we need to

Capture Carbon?

The element carbon is all around us. It is one of the main chemical components of every living thing. When things containing carbon, such as wood, coal or charcoal are burnt openly in air, carbon dioxide is released. Carbon dioxide is a polluting greenhouse gas, and as we will explain, preventing too much of it from being released too quickly is extremely important. 

Current carbon dioxide levels in the atmosphere are just over 400ppm. We are constantly told that this level is dangerously high, and then shown dramatic graphs to illustrate how carbon dioxide concentrations have increased since pre-industrial levels. We are also told that this increase is changing our climate; all of which is true. However, I would like to provide some context: The graph below shows historic carbon dioxide levels going back millions of years.

On this timescale, it is easy to see that our current CO2 levels are historically low; in fact, over the last 400 million years, only four times previously have CO2 levels ever been lower! It is also accepted that around double our current level is optimum for many plants; commercial greenhouses often have artificially boosted carbon dioxide levels of around 800ppm, to increase productivity!

(https://skepticalscience.com/co2-higher-in-past.htm)

So what's the problem?

It is all a question of speed. Historically an increase of 100ppm would have taken thousands of years; plenty of time for the world’s ecosystems to adapt. The current increase has happened in a hundred years – it is just too quick for life on earth. Imagine asking someone who does no exercise to run a mile. They could easily do it by gradually building up to it over time, but could not do it immediately; in fact trying might kill them. This is similar to what we are asking our planet to do, and it isn’t coping. That is why we need to act; the earth needs a water stop – time to take a breath!

(https://www.sciencefacts.net/wp-content/uploads/2020/02/Carbon-Cycle-Diagram.jpg)

This chart illustrates the carbon cycle.

Looking at this chart it is easy to see that unless external factors, such as volcanoes, add carbon dioxide to the atmosphere, the net effect of the carbon cycle is to reduce the amount of carbon in circulation, albeit over vast periods of time. Fossil fuels (coal and oil) represent carbon that is locked in a stable form and has fallen out of circulation. As individuals, we can’t readily make coal and oil, but we can make charcoal. Charcoal is also carbon in a stable form. It won’t readily decompose and release its carbon back into the atmosphere as carbon dioxide.

We could just make charcoal in a kiln and bury it in the earth, but isn’t it better to make it in a form that can be put to other uses, while simultaneously harnessing the energy produced to make it? Biochar is exactly this form of charcoal, and cooking on a Tawi stove is a great way to use that energy!

Capturing and releasing carbon can be labelled in a lot of different ways. We’re very proud to say that using our Tawi Stove is carbon negative, but what does that actually mean? Think of it on a sliding scale from negative to positive. Carbon negative processes remove carbon from the carbon cycle, effectively lowering the amount of carbon dioxide in the atmosphere. Carbon neutral processes do not change the amount of carbon dioxide in the atmosphere; that is usually achieved by offsetting carbon positive processes with carbon negative ones. Finally, carbon positive processes are those which add carbon dioxide to the atmosphere; these are the ones we need to reduce. 

Negative

  • Biochar production
  • Bioenergy with Carbon Capture and Storage 
  • Direct Air Capture of carbon dioxide
  • Growing trees

Neutral

  • Renewable energy, wind and solar
  • Carbon offset (doing a carbon negative process to offset a carbon positive one)

Positive

  • Burning fossil fuels
  • Traditional landfill
  • Burning charcoal

Help reduce charcoal use

Many think of BBQ charcoal as being sustainable because it comes from living trees which can be re-grown. However that is far from the truth. Much of the charcoal we burn in the West started life as ancient forest in Africa. The trees that were felled to cook your BBQ burgers will never be replaced. The lands those trees covered will become stratified and barren. The damage done by charcoal production might be out of sight to most enjoying a summer BBQ; but it is very real.

Of course there are alternatives to charcoal BBQs. However, none of them are more sustainable than the Tawi stove, which burns fallen sticks you can collect from your garden or when out for a walk. When it comes to fuel, the environmental impact of the Tawi stove is zero!

Most charcoal in Kenya is burnt using a simple stove know commonly as a ‘Jiko’. While there has recently been a push to encourage people to use ‘biomass’ logs instead of charcoal in these stoves, the reality is that this type of fuel can only be found in densely populated areas; most people who own a ‘Jiko’ live in the countryside and have to burn charcoal. Of more concern is that most of the ‘biomass’ logs sold as a supposedly eco-friendly alternative to charcoal are predominantly made from charcoal powder anyway! Our technology offers an environmentally sound alternative to these charcoal / ‘biomass’ burners; especially for those living in the countryside.

This article by Neel Dhanesha (published on IDEAS.TED.com) provides a good insight into the environmental problems surrounding charcoal production and use.

How do we capture carbon with the

Tawi stove?

When you strike a match, the oxidising agent at the tip generates sufficient heat to ‘gasify’ the wood it’s attached to. This wood gas ignites and continues the gasification process along the match. The wood turns to biochar, which rapidly cools, preventing it from burning away to ash.

This matchstick of biochar is mostly carbon that would have been released into the atmosphere and become carbon dioxide, had the match been allowed to decompose as wood or been burnt down to ash. Each kilo of organic carbon released into the atmosphere through decomposition, or burning down to ash, becomes 3.6 kilos of carbon dioxide, because each carbon atom combines with two atoms of slightly heavier oxygen. Capturing carbon while still in its solid form, by ‘stealing’ it out of the carbon cycle, is more efficient and easier than trying to extract it directly from the air.

The Tawi stove works in much the same way as the match; turning wood into wood gas, which is burnt cleanly instead becoming acrid smoke, and biochar, which cools and stabilises instead of burning away to ash.

The picture to the left shows you what is happening inside the Tawi. As the fire burns back along the stack, the wood left behind is bathed in oxygen-depleted flames. These flames gasify the wood via pyrolysis. The wood gas produced then mixes with air and ignites as it passes up the flue. The high temperature within the flue produces a flame that is almost smoke free. Smoke is basically wood gas that is not hot enough to completely combust.

As you push more fuel into the chamber, the biochar produced collects in the back of the burner, where it cools and stabilises.

Become a

Carbon Farmer

Buy your own Tawi Stove to begin carbon negative cooking at your home. 

Follow us on social media for frequent updates on recipe ideas, what to do with your biochar and new ways in which to use your stove to help the planet. 

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