Charcoal gas stove

By Vuthisa


This blog post aims to provide the reader with some background on charcoal stove usage as well as charcoal burn characteristics.  Vuthisa developed a unique charcoal stove, able to extract and burn harmful Carbon Monoxide gases inherent to all types of charcoal.

Jiko charcoal stove

We discovered that charcoal use by households is not a new concept and constitutes the primary urban fuel in most of Africa and it is estimated (2003) that approximately 250 million people cook with charcoal. The prevailing tendency in household fuel usage has been to move away from wood fuel towards charcoal for reasons ranging from smokeless burn, ease of use, easy storage, no insect infestation, no need to air-dry, cost effective to transport and high temperature burn.

Rural village in the Eastern Cape provinceSeveral intervention studies have also shown that switching from wood to charcoal can substantially reduce respiratory infections, which may also account for the move over to charcoal. Much of the world’s charcoal feedstock is not plantation wood and the unsustainable harvesting of biomass result in widespread deforestation, thereby handing charcoal its bad reputation. In our context, countries like South Africa (and most developing countries) with well managed commercial plantations and exotic invaders however can provide a sustainable supply of charcoal for household end-use applications. In our opinion improved charcoal stoves should only be sold to communities if the charcoals are produced from carbonised invasive alien vegetation or managed commercial plantations. See our Welcome post in this regard. The manufacturing process is also very polluting and wasteful and there is a serious need of improved charcoal kilns. Join the Portable Kiln Google Group, which I started in order to improve the efficiency of this design or for more information visit this information page and join our design challenge.

More modern fuels such as paraffin- and LP Gas are becoming more popular than fuel wood for cooking and space-heating, but have led to several deaths due to accidental shack fires or lethal gas leaks. Burning charcoal conventionally inside a home is a hazardous and potentially fateful undertaking due to the dangers of Carbon Monoxide (CO) poisoning. I highly recommend Carbon Monoxide Poisoning – A Medical Dictionary, Bibliography, and Annotated Research Guide to Internet References.

Some experts agree however that if issues of concern related to CO such as ventilation and education can be successfully addressed, the widespread implementation of improved charcoal cook stoves should be considered. Traditional charcoal burning stoves such as the metal and ceramic Jiko and Loketto were designed to retail cheaply and provide durability during extended usage, which they do, but failed to address the problem of Carbon Monoxide (CO) poisoning once the occupants go to sleep.

Vuthisa decided to investigate charcoal burning by developing and field testing many prototypes. Feedback from stove users indicated that charcoal can be very abrasive on metal surfaces in direct contact with flames and due to the rapid heating and cooling tendencies of a charcoal fire. Charcoal burned in coal or fuelwood stoves reduced the lifetime of these stoves significantly. Refractory ceramics (and low-density clay bricks) offered the best results as it insulates the fuel from the stove body, but also allows combustion temperatures to rise above 600°C for complete combustion of volatiles.

We discovered that the volatile Carbon Monoxide (CO), a fuel in its own right should instead of being vented off be re-combined with pre-heated Oxygen (O2) from the air in a process termed Gasification. This results in a LP gas-like flame, venting harmless CO2. The process occurs spontaneously and the charcoal fuel batch will burn out in its entirety within 90 minutes from lighting the stove. Depletion of Oxygen levels in a poorly ventilated room can therefore not occur and CO issuance build-up remains below Health and Safety limits.

Best Burn Method

We found it is possible to light the stove indoors with minimal particulate issuance by top lighting the stove using kindling (visit to see the advantages of the top down lighting technique). We monitored CO build-up inside the room with a Draeger X-am 5000 CO monitor, maintaining adequate ventilation. The maximum CO ppm (parts per million) recorded was 30 ppm over a 1.5 hour period. Once the occupants gets exposed to levels of around 200 ppm for extended periods they will experience nausea, headaches and vomiting. Higher levels of around 1000 ppm for example, have far more serious consequences, including falling into a coma and never waking up.

Back to charcoal burning: After the stove is lit, temperatures will continue to rise inside the chamber and more coals will start to combust, although the top layer will be protected by a so-called “pyrolysis wind”. Primary air is drawn up the combustion chamber by virtue of the internal chimney. The stack length has been optimized to control the draft to combine 6 parts air to 1 part fuel, with the secondary air supplying the remaining 6 parts air to resultant 1 part producer gas. Pre-heated secondary air (drawn in along with the primary air before splitting off) will spontaneously interject into the area above the charcoal particles and mix with a constantly escalating supply of producer gas (CO and other volatiles) from the coals. Stoichiometric air/fuel ratio is achieved after approximately 8 to 10 minutes following start-up and gasification commences, the visual clue being a blue flame front forming off the burn plate (catalyst). Most charcoals contain approximately 20 to 30% producer gas, i.e. is not vented during the charcoal manufacturing process and the stove will deplete these supplies in approximately 30 to 40 minutes. The resultant ‘coke’ will also partially gasify and burn to ash over the remaining 30 to 45 minutes. The stove can be operated on a maximum fuel load of 500 grams of charcoal for approximately 1.5 hours. It can use as little as 150 grams of charcoal, sufficient to cook a small meal or for boiling approximately 1 L of water. A full patent was granted in 2006 and is still in force. Double click on video image below to see charcoal stove in action.

We’re not the only ones thinking charcoal gasification has potential in the developing world. See this publication by Ulrich Graf called Low Cost Charcoal Gasifiers for Rural Energy Supply (GTZ, 1994, 49 p.). The publication demonstrates to interested laypersons and experts the conditions and applications under which small charcoal gasifiers can be one option for development within a range of simple energy technologies.

It is also possible to “pipe off” volatiles produced by a charcoal gasifier to run a generator as can be seen in this example:

Or watch this video below showing some of our Bioenergylist discussion group members experimenting with a burner attachment. Double click on the still image below to start video.

I also converted a barbecook® into a charcoal gasifier.  Just to prove the concept as I think flame grilling with charcoal has a lot of potential.


Remainder of mix poured over mold

Bricks extracted from mould and ready to be firedVuthisa partnered up with the University of KwaZulu-Natal’s Ceramic Department in Pietermaritzburg to develop insulated fire bricks. We have made significant progress with our insulated fire bricks, with the mixture consisting of mainly Al2 O3, Fe2 O3, SiO2, CaO, grog and a light-colored refractory clay. An external supplier was contracted to supply the pre-mixed clay in powdered form. The cost per cubic metre is low and lends itself perfectly for this application. The density is lower than what can be achieved with clay mixes that contained sawdust. Our most recent bricks achieved a density of approximately 0.5 g/cm3 which qualifies it as an extremely lightweight yet durable refractory brick. The bricks and the ash filtering base are then joined together via a specially formulated paste-like cement that can withstand temperatures of up to 1300°C to form a hex shaped combustion chamber.

We also have a monolithic, precast, pre-fired, silicon-hardened, fibrous, refractory ceramic sleeve (not replicable outside South Africa) with a density factor of around 0.5 g/cm3, which is being used in our outdoor camping stove.


Stove programs in South Africa have a poor track record (Wood as a source of fuel in South Africa, MV Gandar, 1983). Attention is all too often focused on fuel efficiency, economics and ease of construction at the expense of the socio-cultural environment. It is therefore important to slowly introduce a new stove concept to the target community to test their acceptance of it, but also to demonstrate the advantages that owning such a stove offers. It will be vital to do product acceptance trials in the proposed project implementation area and adopting a successful dissemination technique will take the stove project towards success through inception to maturation. Extension workers should record cooking technique and fuel usage information. The information must be interpreted to fine tune the design specific to the needs of the community.

In summary

It is hoped that by informing a wider audience, strategies can be formulated to improve charcoal making and charcoal burning technologies.

Camping stove to create awareness

Our prototype portable charcoal camping stove aims to highlight the plight of millions of people cooking on inefficient and unsafe charcoal stoves. It is not for sale at this time. Kindly donate (on the sidebar to the right) to help us bring the stove to the market!

In line with creating awareness around issues concerning indoor air pollution, we also promote the clean-burning StoveTec Rocket stove. Click here for more information.

Enquiries welcome via our Contact us page or visit the News link from time to time for updates.


Is it better to burn wood or charcoal?

By Kobus Venter

Is it better to burn wood or charcoal? Half the World’s population of nearly six billion people prepare their food and heat their homes with coal and the traditional biomass fuels of dung, crop residues, wood and charcoal  (Inheriting the world: The atlas of children’s health and the environment, by Bruce Gordon, Richard Mackay and Eva Rehfuess, WHO 2004). In China, India and Sub Saharan Africa, up to 80% of urban households use biomass fuels for cooking. Wood fuel usage is the most predominant with charcoal a close second. What is their respective influence on global warming? Sorry, but this post will not attempt to discuss this complex issue, because the reality is that for most people struggling with energy security, saving the environment is not exactly high on their list. The following paragraphs will instead focus briefly on the burning characteristics of wood and charcoal, because in many cases availability and affordability of the fuel type will dictate which fuel type is being used.

Typically wood has an energy value of between 14 and 18 MJ/kg when burned. Charcoal has an energy value of around 29 MJ/kg, in other words charcoal burns hotter than wood, but when not insulated or not receiving sufficient air supply (including secondary air), the absence of flames or fast flowing CO2 gases will result in less efficient cooking due to a lower heat transfer efficiency (HTE). In other words with conventional charcoal burning (glowing embers) the pot will receive radiant and infrared heat, with the pot positioned close to the coals. Wood burning flames (especially from open fires) tend to ‘lick’ the pot and transfer heat more effectively, but contain products of incomplete combustion (PIC), also known as ‘particulates’, that are harmful to humans when inhaled. In many instances households cannot afford to purchase or install chimneys that remove the smoke. The flames (yellow colored) will also tend to blacken cooking pots. Indoor smoke inhalation gives rise to pneumonia and other respiratory infections – the biggest killer of children under five years of age. Indoor air pollution (IAP) is responsible for nearly half of the more than 2 million deaths each year that are caused by acute respiratory infections (ARI). Good ventilation and improved cooking stoves can dramatically reduce children’s exposure to smoke. Vuthisa currently promotes the StoveTec stove which is very fuel efficient (conserves wood) and emits 70% less smoke. Visit for more information.

Charcoal is preferred over wood as a cooking fuel in many parts of the world because it does not produce smoke, is easier to transport and ready to use in a convenient dry- and broken-up form. Charcoal burning however produces large amounts of Carbon Monoxide (CO) which is harmful to humans when exposed to very high levels. Increasing air flow through the charcoal emits more CO, so if you don’t mix secondary air with the CO and insulate the fuelbed to raise temperatures to spontaneously combust that mix, you’re better off with a glowing ember burn. Most charcoal stoves (i.e. Ceramic Jiko) are not designed around this principle and won’t be much different to your barbecue, whereby you vent all the gases first and then cook on the glowing embers. There is anecdotal evidence that family members have succumbed to CO poisoning, but families using charcoal are very aware usually of it’s dangers and allow for adequate ventilation. Why is CO harmful to humans? Let me explain: The effect of high levels of exposure to CO can be lethal, but even low levels of exposure can have harmful effects. CO diffuses rapidly via blood vessel membranes. Once it’s present in the bloodstream, CO binds to hemoglobin 200 times more readily than oxygen. This forms carboxy-hemoglobin (COHb). COHb reduces the oxygen carrying capacity of the blood and impairs the release of oxygen from hemoglobin. The neurobehavioral effects include impaired coordination, tracking, and driving ability. Cognitive performance is impaired at COHb levels as low as 5%. During exposure to a fixed concentration of CO, the COHb concentration increases rapidly at the onset of exposure. This levels off after about three hours, and reaches steady state after 6 – 8 hours of exposure. Headaches, nausea and loss of consciousness occur at COHb levels of 25-40%. Permanent brain damage and death follow if COHb levels exceed 45%. Vuthisa developed a safe charcoal stove over the last few years to address this very issue.

I don’t advocate charcoal usage over wood, because of the wasteful manner in which charcoal is made and the charcoal trade destroys naturally occurring forests and contributes to global warming. There are signs that governments are trying to regulate the industry by introducing more efficient charcoal-making kilns and establishing plantations to ensure sustainability of the timber source. In Namibia, millions of hectares of encroachment bush is being converted to charcoal and sold to neighboring South Africa as barbecue charcoal. South Africa itself (according to the most recent South Africa Yearbook) is plagued with alien plant infestations, totaling more than 10 million hectares, about eight percent (8%) of the country’s land surface area. The rate of spread is alarming and their numbers are projected to double over the next 15 years.  More recently Vuthisa Technologies started to convert slashed invasives into charcoal and biochar using Emission Reducing Biochar kilns in a project known as the Vuthisa Biochar Initiative.

My verdict: It seems there is no clear winner, just spare a thought for the millions of people that rely on either wood or charcoal for their day to day survival.


Air conditioners and the environment: Tips to improve indoor air quality

By Vuthisa

My blog hopes to alert people’s attention to indoor air pollution in the developing world – but what about the developed world? In the next couple of weeks I plan to post some more articles related to indoor air pollution in developed economies. Since most of us like to control our micro environments I figured air conditioners would be a good place to start.

The Good: The use of air conditioners raises productivity and worker morale in the work place by providing a comfortable working environment and is more increasingly being used in residential areas.

The Bad: The power required to run air conditioning consumes fossil fuel, depleting reserves, and adding to global warming. Artificially changing the temperature from ambient levels confuses the body’s regulating mechanisms, designed to synchronize our bodies with seasonal variations and lowers resistance to infection – infections we are more likely to get as a result of breathing recycled air.

The effect of air conditioning on the environment does not concern this particular post, but we might be able to lessen the impact on the environment:

By supporting companies that sell systems that use safer refrigerants in order to stop ozone layer depletion; develop energy-efficient air conditioners and recover refrigerants from used air conditioners.

Switching to mini-duct; ductless or split air conditioning systems, although in some cases more expensive, are more energy-efficient, which means less greenhouse gases.

See these useful hints to increase your indoor air quality below provided by Rosalind Dall who has a personal blog dedicated to help people consume less energy and purify indoor air:

Rain and high humidity may bring moisture indoors, creating dampness, mold and mildew – big problems for healthy indoor air. Check your roof, foundation and basement or crawlspace once per year to catch leaks or moisture problems and route water away from your home’s foundation.

Help keep asthma triggers away from your house by fixing leaks and drips once they start. Standing water and moist areas encourage the growth of dust mites, fungus – some of the most common triggers that can worsen asthma. Use a dehumidifier or AC unit when needed, and clean both regularly.

High amounts of moisture in your home increase dampness and the growth of mold, which not only damage your house but threaten health. Install and run exhaust fans in bathrooms to get rid of unhealthy moisture and odors out of your home.

Ventilate your kitchen stove directly outside or open a kitchen window when you cook. Keeping emissions (including cooking odors and particles) outside of your home prevents dangerous fumes and particles from harming you or your family.

Here are some ways to save energy (and improve your home air quality):

Be sure your thermostat is located in a spot that isn’t too cold or hot. Install an automatic timer to maintain the thermostat at 68°F (20°C) during the day and 55°F (12.8°C) during the night time.

Use storm or thermal windows in colder areas. The layer of air between the windows acts as insulation and helps maintain the heat inside where you want it. Also if you haven’t already, insulate your attic and all outside walls.

Insulate floors over unheated spaces like your basement, any crawl spaces and your garage.

Close off the attic, garage, basement, spare bedrooms and storage areas. Heat just those rooms that you use, seal gaps around any pipes, wires, vents or other openings that could transfer your heat to areas that are not heated.


Welcome to VUTHISA (pronounced VOO-TEE-SA). VUTHISA is a ZULU word for “to set on fire” or “View This South Africa”, whatever you prefer, has evolved over the years from sharing information on INNOVATIVE GREEN TECHNOLOGIES to designing and building our own BIOCHAR equipment. It is a Closed Corporation and solely owned by Kobus Venter, a single father with a 17 year old son (2018).

The following table outlines some of the projects we have initiated and managed over the last few years, showing the significant monetary resources we have had to secure and generate to execute these projects:


  • VUTHISA BIOCHAR INITIATIVE part funded by EEP-S&EA (Energy & Environment Partnership Southern and East Africa) EEP-S&EA 
  • VUTHISA CHARCOAL PROJECTS part funded by the Department of Environmental Affairs (DEA) , Working for Water Program, employing 74 workers

These projects were concluded in 2016/17 and a clean audit was received for both. We have an overdraft facility with a local financial institution that needs servicing and we require regular cash flow in order to to keep the facility active.

Other projects include the RATCHET PRESS with samples delivered to the United Nations High Commission for Refugees (UNHCR) and a community project involving the Corporate Social Investment program of an international tobacco company.

Picture 1 – Kobus Venter with one of the Ratchet Press units going to the UNHCR

The work starts now however in rolling out our RETORTS nationwide and around the world. SOUTH AFRICA is currently sitting with an unemployment rate of 30% nationwide or some 9 million people and much work can be created along with sustainable income for them.

See this link showing our waste Waste Biomass Beneficiation & Job Creation Solution:

We are a for-profit business and receive no support from the Government and do not qualify for tax deductible donations like NPO’s and other non-profits.

Please support us on Patreon so we can continue with this work.

Go on this journey with us and we will show the fruits of our labor as each project is rolled out. Currently we are working on creating more rigid BIOCHAR systems with automatic auger feed systems to and away from these and improved units. A turn key operation will then process the outflow of surplus waste generated by local industries, such as Sawmills, Vineyards, Farms and other industries.

Thank you!


…and a final footnote and a South African perspective on exotic plant alien infestation…

Background to exotic alien plant infestation

South Africa (according to the most recent South Africa Yearbook) is plagued with alien plant infestations totaling more than 10 million hectares, about eight percent (8%) of the country’s land surface area and 2.5 million hectares of Acacia mearnsii (black wattle) has steadily encroached on our indigenous bush and once pristine riverbeds. The fight against invasive alien plants is spearheaded by the Working for Water (WfW) programme, launched in 1995 and administered through the Department of Environmental Affairs (DEA). This programme works in partnership with local communities, to whom it provides jobs, and also with government departments, research foundations and private companies. The WfW programme is one of the Natural Resources Management Programmes (NRM).  Other programmes include: Working on Fire, Working for Land, Working for Forests and Eco-Furniture Factories.

Although a step in the right direction it has not prevented the further spread of invasive aliens.  The rate of spread is alarming and their numbers are projected to double over the next 15 years. The WfW programme, also aimed at creating employment has been allocated R665,9-million ($83 million USD) in the 2010/11 year, but this amount is not sufficient to contain the problem (Source: CSIR scientists have recently commented: “Although an estimated R6.5 billion was lost every year due to invading alien plants, this would have been an estimated additional R41.7 billion had no control been carried out. This indicates a saving of R35.2 billion every year.”

The main culprit is Acacia mearnsii or black wattle, a hardwood that just so happens to make excellent charcoal. Vuthisa strongly advocates the removal (and stump treatment) of these weeds from riverbanks and open land by converting it to charcoal using our Portable charcoal-making kiln. In Namibia, 26 million hectares of encroachment bush is being converted to charcoal and sold to neighboring South Africa using this method. This kiln is cheap to construct and portable. This will slow the encroachment rate of the invaders and encourage micro-entrepreneurial activity to alleviate the country’s high unemployment rate.