An example of theoretical carbon credit revenue in Mexico

Carbon credits, fuel-efficient stoves and greenwashing

Carbon credits, also known as carbon offsets, are a way to measure and trade reductions in greenhouse gas emissions. Fuel-efficient cookstove projects reduce greenhouse gas emissions from burning coal, charcoal, fuelwood, dung and other biomass fuels. The amount of reduced greenhouse gas emissions from fuel-efficient stove depends on both its combustion efficiency, and its usage frequency given the common practice of stove stacking, where households use a variety of stoves to accommodate different cooking practices. Furthermore, a fuel-efficient cookstove’s theoretical combustion efficiency, as measured in laboratory settings, can be higher than actual combustion efficiencies seen in development settings, due to imperfect usage of the stove, or wear and tear. This and other issues in measuring carbon credits such as leakage has led in recent years to appearances of project “greenwashing” and has lowered carbon credit values for fuel-efficient cookstove projects(1) .

Carbon savings in solar cooking

Whereas fuel-efficient stoves generate less smoke and greenhouse gases than traditional three-stone fires, solar cookers are able to cook food without any fuel, generating zero smoke or greenhouse gases, and the risk of lower-than-advertised combustion efficiency is not applicable. Indeed, solar cookers’ ability to reduce greenhouse gases depends solely on their usage frequency.

Solar cooking social benefits garner higher carbon credit prices

In addition, solar panel and box cookers can be left unsupervised for hours at a time to solar cook foods slowly and evenly (like a crockpot), freeing women of the burden of chopping wood, tending to the fire, and stirring the pot to prevent burning the food. This allows women to engage in productive activities such as going on errands, attending to their children or gaining employment. These additional social benefits have earned some solar cooking projects “Gold Standard” certification, and higher carbon credit prices. Whereas most cookstove carbon credits typically sell for $5 to $10 per metric tonne of carbon dioxide equivalent (2), some with social benefits will garner over $25 per metric tonne of carbon dioxide equivalent. (3)

 
Theoretical estimated carbon credit revenues for SHE’s Mexico solar cooking projects

SHE does not currently manage any solar cooking projects certified for carbon credits, as the certification process is rigorous and expensive, making it cost-effective for projects upwards of 5000 solar cookers. We are in discussions with carbon brokers on the possibility of initiating such large-scale projects.

As an example of how carbon credits could support the spread of solar cooking, we examine the potential net revenue from the distribution of Haines Pop Open solar cookers in rural Mexico, where the predominant cooking method is the traditional wood-fired brasero, similar to a three-stone fire. Our studies show that solar cookers mainly replace the use of this “brasero,” used for cooking large slow-cooking dishes such as beans and rice, soups, and meat stews, dishes that are usually eaten at a late lunch around  2 pm. The gas stove is typically used sparingly for making coffee in the morning and heating up leftovers for dinner. This explains why participants typically report using their solar cookers 2 or 3 times per week but saving up to 50% of their fuelwood.

1) Baseline fuelwood consumption – 2704 kg/household/year

SHE’s baseline studies of cookstove usage in rural communities in Oaxaca, Mexico showed an average fuelwood consumption of 52 kg per week per household. That’s 2704 kg per household per year. According to this study about rural Mexican households, households that used a traditional stove exclusively for cooking consumed an average of 3.3 kg of fuelwood per adult per day. Households that used a traditional stove in combination with an LPG stove consumed an average of 2.7 kg of fuelwood per adult per day.”  Our baseline survey results in 2017 fall within that range, with an average consumption of 7.4 kg per household per day. If each household has 2 adults, that’s 3.7 kg per adult. If each household has 3 adults (grandparents, etc..), that’s 2.4 kg per adult per day.

2) Fuelwood savings – 811 kg/year/solar cooker at conservative 30% savings
SHE’s one-year pilot project evaluation showed an average usage of 3 times per week, and 47% of users claiming a dirty stove substitution rate of over 50% during the sunny season. Previous studies showed a usage decrease of less than half during the cloudy season. SHE’s five-year evaluation of the “Solar Cooking Ambassador Program” in Oaxaca, Mexico, carried out in December 2022, found an average usage of 2.9 times per week for solar cookers that were 4 years old on average. For this example study, we will use the very conservative estimates for our calculations of 30% savings in fuelwood over the whole year. Given our previous estimate of fuel consumption of 2.7 tonnes per year, that gives us fuelwood savings of: 2704 kg x 30% = 811 kg per year per household (or solar cooker). Since the vast majority of these households owned one solar cooker, we can simplify this to fuelwood savings of 811 kg per year per solar cooker.

4) Carbon price ($15) and annual revenue – $19.5/solar cooker/year
As explained earlier, carbon prices for cookstove projects vary widely. Let’s go with a conservative carbon credit price of $15/tCO2 for a solar cooker project with positive social impacts. That gives us a revenue of: 15 t/CO2 x 1.3 tCO2/solar cooker/year = $19.5/solar cooker/year

5) Carbon revenue over solar cooker life – $53.2/solar cooker
A Haines Pop Open can last over 5 years with proper care. Let’s use a conservative average lifetime of 4 years. The potential carbon revenue over these 4 years would be:
$19.5/solar cooker/year x 4 years = $78/solar cooker

6) Net carbon revenue per solar cooker – $28/solar cooker
The net revenue accounts for the cost of the Haines solar cooker and its dissemation, including delivery, training, maintenance and support over its 4-year lifetime. In the past in small Haines solar cooking pilot projects, typically for 10 to 40 solar cookers, the project budget has been close to $100 per solar cooker, given fixed costs for training, monitoring, evaluation and reporting to funders. At larger scales required for carbon credit projects, we can expect the cost per solar cooker to go down. The at-cost price for a Haines Pop Open solar cooker is around $35. Let’s go with a conservative scaled-up project cost of $50 project costs per solar cooker. That gives us a net revenue of: $78 – $50 = $28 per solar cooker.

In summary:

Net revenue per solar cooker = ((Annual fuelwood consumption/household (tonnes) x household fuelwood savings (%) x Emissions Factor for C02 for traditional unvented wood stove (IPCC value of 1.644) x carbon credit price (USD/tCo2) x Haines solar cooker lifetime (years)) – solar cooker cost (USD)

Net revenue per solar cooker = ( 2.7 tonnes/household x 30% x 1.644 x $15/tCO2 x 4 years) – 50 USD = $28/solar cooker.

In other words, even with conservative estimates, carbon credits would cover the costs of Haines Pop Open solar cookers and their dissemination,  leaving $28 per solar cooker as profit.

Your contributions can help us achieve the goal of developing solar cooker projects that are ready for carbon certification. Please donate today!

 

References
(1) African Business. May 30th, 2024. “Can clean cooking recover from carbon price slump?” Accessed in 2023: https://african.business/2024/05/energy-resources/can-clean-cooking-recover-from-carbon-price-slump

(2) Peter Sainsbusy. Carbon Risk. November 22, 2023. “Repost: How the other half cooks.” Accessed in 2023 at: https://carbonrisk.substack.com/p/repost-how-the-other-half-cooks

(3) Gold Standard. “Solar Cooking for Refugee Families in Chad.” Accessed 2023 at https://marketplace.goldstandard.org/products/solar-cooking-refugee-families-chad?_pos=1&_sid=519bf3de1&_ss=r

(4)  Rufus Edwards. WHO Indoor Air Quality Guidelines:  Household fuel Combustion Review 2: Emissions of Health-Damaging Pollutants  from Household Stoves. p. 16. Accessed in 2023: chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://www.newdawnengineering.com/website/library/Papers+Articles/WHO/WHO%20IAQ%20Guidelines,%20Rev%2002.pdf

(5) Shailesh Telang. Feb 12, 2012. How to calculate carbon emissions from a fuel wood cooking stove? Accessed in 2023 at:
<https://greencleanguide.com/how-to-calculate-carbon-emissions-from-a-fuel-wood-cooking-stove/>