TLDR: On early-stage analysis, persuading people to soak their beans before cooking could cost-effectively save Sub-saharan Africans money, and modestly reduce carbon emissions. (great uncertainty)
Across East Africa, hundreds of millions of people cook and eat beans multiple times every week. In Uganda where I live, beans make up an estimated 25% of the average Ugandan’s calorie intake and 40% of their daily protein intake. Unfortunately cooking beans takes an absurd amount of time - usually two to three hours using charcoal or wood. The great news is that just soaking beans in water for 6-12 hours reduces cooking time by between 20% and 50% and has no negative effect on bean taste or nutrients  . When we tested soaking vs. not soaking, cooking time reduced by half.
Despite the obvious benefits of massively reduced cooking time using less fuel., very few people in Uganda soak their beans - nobody I know at least. I estimate under 0.5% of Ugandan families soak beans, but likely far less. I couldn’t find any data on bean soaking habits in Uganda or Sub-Saharan Africa in general but I have heard anecdotally that it is common in some countries, perhaps Zimbabwe? (insider knowledge appreciated).
Considering Uganda alone, Ugandans eat an estimated 10-20kg of beans per capita every year . Changing the behaviour of even a small percentage of Ugandans by convincing them to soak their beans, has potential benefits of reduced fuel burned, bringing about a range of environmental, economic and health impacts.
Soaking beans could be IMPORTANT due to the potential environmental, economic and health benefits gained through reduced cooking time. It is NEGLECTED as no organizations we know of are working on mass media or other interventions to persuade people to soak beans. It may be TRACTABLE as people can immediately experience financial benefit from soaking beans through reduced expenditure on charcoal and time gathering firewood.
Potential impact calculations
Uptake: For simplicity, we assume that it may be possible to persuade 1% of Ugandans to change their behavior and soak beans. This is just a guess at what could be the outcome of a moderately successful campaign.
Fuel/time saving: We estimate a 25% time and fuel saving from soaking beans (ref)
Time horizons: If someone starts soaking their beans, once benefits are clear and the change is locked in, it seems likely that they and their family will continue to soak for a long time, possibly even indefinitely. On the other hand, Uganda could electrify faster than expected making much of this analysis obsolete (unlikely), or Ugandans could start eating something other than beans (also unlikely). To be conservative, we have capped our analysis at 5 years of benefit from the campaign.
Counterfactual: For the purposes of this analysis we assume that all of the 1% of Ugandans who will change behaviour to soak beans is due to our intervention. This is somewhat reasonable as there are no current efforts promoting bean soaking, and it is very unlikely people will change their behaviour without a specific promotion campaign
CO2 emissions prevented through soaking
Environmental impact could come through two avenues – CO2 equivalent emissions prevented, and deforestation prevented. Although benefits of preventing deforestation could potentially be large, it is difficult to calculate so here we only calculate the potential CO2 emissions prevented, first through reducing charcoal use, then through reducing woodfire user.
Charcoal: CO2 equivalent saved by bean soaking
About 1 in 3 Ugandans use charcoal for cooking. We estimate the Uganda-wide amount of charcoal use for cooking beans through 2 diffrent methods, then use the average of these estimates for our final calculation.
Charcoal quantity used to cook beans
Method 1 – Start from Charcoal consumption directly
A 2015 Ugandan study estimated that 5000 tons or charcoal are used in Uganda for cooking every day . If we assume that 20% of these are used for bean cooking (conservative given that beans may make up 25% of Uganda’s calorie intake but take longer than other foods to cook), then we estimate that 1000 Tons of charcoal are used daily for bean cooking.
Method 2 - Start from bean use
We estimate dry bean consumption of 15kg per person per year. Through 2 sources (practical and theoretical) we estimate that about 1kg of charcoal is needed to cook 1kg of beans (footnotes). That means if there are 50 million Ugandans, 1/3 of whom are cooking with charcoal, this will account for a yearly consumption of...
15 x 1/3 x 50,000,0000 = 250,000,000 KG of charcoal a year.
Converted into tons per day, this is
250,000,000 / 365 (days) / 1000 (kg) = 684 Tons of charcoal used daily for bean cooking.
We take the average of these 2 estimates (which are encouragingly not so different),
843 Tons of charcoal used daily in Uganda for bean cooking.
If we assume 1% population adoption of bean soaking, and a soaking benefit of 25% less charcoal use then:
0.01 x 0.25 x 843 = 2.11 tons of charcoal burning prevented daily by soaking
We estimate CO2 emissions (About 80% of charcoal emissions arise from very inefficient charcoal production) at 12.5kg released for every kilo of charcoal burned.
= CO2 equivalent emissions saving of 2.11 x 12.5 = 26.4 Tons daily, or 9,627 tons over 1 year, or 48,134 tons of CO2 emissions reduced over 5 years
Wood CO2 equivalent saved by bean soaking
We estimate dry bean consumption of 15kg per person per year. Around 2/3 of Ugandans use wood for cooking. There is enormous variation in quantities of wood used, but we have conservatively estimated 1.5kg of firewood used to cook 1kg of beans, which means if there are 50 million Ugandans, 2/3 of whom are cooking with firewood, this is a yearly consumption of...
15 x 2/3 x 50,000,000 x 1.5 = 750,000,000 KG of firewood used per year for bean cooking.
If we assume 1% of the population adopt bean soaking, and a soaking benefit of 25% less firewood used, then:
0.01 x 0.25 x 750,000,000 / 1000 = 1,875 tons of wood burning saved per year
Wood burning Emissions
Firewood produces about 25% of the CO2 equivalent emissions of charcoal, about 3kg CO2 equivalent for every 1kg burned. So over a 5 year period
1,875 x 3 x 5 = 28,125 tons of CO2 equivalent emissions reduction over 5 years
So total estimated emissions prevention from 1% uptake of bean soaking in Uganda
= 28,125 (firewood) + 48,134 (charcoal) = 76,249 tons of CO2 equivalent reduced
Money Saved by soaking beans
The second potential benefit is money saved through purchasing less fuel. As nearly all firewood is cut locally and not bought, we have not considered firewood here. Nearly all charcoal on the other hand is bought, so we assumed for analysis all was bought.
Some people buy charcoal by the sack which is around 1000 shillings per kg, but most buy charcoal in small quantities, which is far more expensive at around 2000 shillings per kg. For our estimate we have split the difference and used 1500 shillings per kg
Using the previous estimate of 2.1 tons of charcoal saved daily
2,100kg x 365 days x 1500 Ugandan Shillings = 1,149,750,000 Shillings saved yearly
= 5,759,750,000 Shillings saved over 5 years =
about 1.5 million US dollars saved by Ugandans on charcoal burning
Other Potential benefits not calculated
1) Health – We have not calculated potential health benefits or reduction in cooking time due to unclear benefits. Although in theory soaking beans could significantly reduce respiratory diseases through less smoke exposure, a 2020 Givewell assessment of the medical benefit of clean cookstoves showed no clear evidence of health benefits through use of cooking stoves, similar to other systematic reviews. As a doctor this seems insane not to calculate the benefits of having significantly less smoke in your lungs every day, but we’ll leave it there for now.
2) Time saved. Although soaking beans would save Ugandans an absurd amount of aggregate time, the concrete benefits aren’t clear, especially in rural areas where time isn’t really a limiting factor to productivity. In urban areas there are sure to be productivity and income benefits through time saved by soaking beans, but these benefits are difficult to calculate.
3) Deforestation prevented. Deforestation and biodiversity loss from burning charcoal and wood are huge, but this potential benefit wasn’t estimated here due to lack of clear data (but am open to ideas as this could be important)
Behaviour change is always difficult and the non-soaking of beans is an ingrained norm in Uganda, but there are reasons to think change might be possible.
Why Bean Soaking ma be tractable
1. Many people don’t know soaking beans speeds up cooking. For some people, the new knowledge alone might be enough to change behavior. Most behavior change is attempted on behavior people already know about but don’t do, which is harder.
2. Financial incentive. There is a clear and immediate financial incentive to soak with less money spent on charcoal
3. Bean soaking may be common in other countries (low certainty). I have heard anecdotes that in some countries (potentially Zimbabwe and South Africa), bean soaking is more common. This might be a sign that soaking is a realistic behavior
4. Lack of obvious cultural objections. Although obviously the current culture is to not soak beans, I don’t think there will be strong cultural barriers to bean soaking.
5. Institutions may have strong incentives. Institutions use an estimated 19% of Uganda’s charcoal, and may have more incentive than individuals to change due to the huge potential cost-savings for institutions. Institutions are also heavy bean consumers, as most institutions in Uganda cook beans almost daily.
However other successful behavior change interventions examples may be more tractable than bean soaking. For example people already want their kids to be vaccinated, they are already convinced of the benefit but can easily forget. This makes vaccine text reminders very effective in changing behavior, probably more than could be expected in soaking beans.
Why Bean Soaking might not be tractable
1. Cooking norms are hard to change. When people are in the habit of cooking the same way they
2. Misinformation. After a few very casual discussions, we have already identified potential beliefs which may hinder uptake, such as that soaking may reduce nutrients, or worsen the taste of the beans
3. Suspicion of intentions of external actors: All behaviour change campaigns in Uganda, whether vaccination for covid, or family planning interventions are met with understandable skepticism
Overall Cost-effectiveness Estimate
So if 1% of Ugandans START soaking their beans, we conservatively estimate in 5 years
- 1.5 million dollars saved by Ugandans
- 76,249 tons of CO2 equivalent emissions reduced
- Unquantified Health, time and reduced deforestation benefits also possible
If a 300,000 dollar promotion program had a 20% chance of convincing 1% of Ugandans to soak beans, it would be effectively Expected Value cost neutral over the 5 year time horizon (or better if money is worth more to Ugandans than it is to us), with the environmental and other benefits a “bonus”. This might be optimistic, but seems reasonable.
Another cost neutral possibility is if a 300,000 dollar program had a 10% chance of convincing 1% of Ugandans to soak bans, and a 1% chance of convincing 10% of Ugandans to soak beans.
If benefits exceeded our conservative assumptions of only a 1% behavior change and a 5 year time horizon, there is a small chance of much larger benefits. There is even a tiny (?<0.1%) chance of a “bean soaking” movement which spread across East Africa and would have enormous impact.
With great uncertainty, a concerted effort to increase bean soaking in Uganda could be cost-effective.
How to help 1% (or more) of Ugandans soak their beans?
Perhaps the most obvious route to behavior change here would be through Mass Media Campaigns similar to those used in childhood vaccination reminders, or HIV safety education. Village health workers could also be deployed to move between homes. Women’s savings and loans groups could also be a high yield medium for sharing this information. There may well be many options too
I was surprised that the potential financial benefit could be this high for soaking beans. On the other hand, potential CO2 emissions prevented was far lower than I expected. Its a pity I couldn't lump in other potential benefits like time in town and deforestation prevented as well. I haven’t included error ranges (which are large) in this analysis because I am lazy, and its a preliminary assessment only.
I would LOVE to hear any criticisms, corrections of math or any other insights. There could well be large mistakes, even orders of magnitude. Thanks for reading this analysis of a slightly odd potential cause/intervention!
Thanks to Harry and Meg for the idea, and Tibo for helping with the analysis and proofreading. These wonderful people aren’t on the forum yet, but maybe they can be convinced soon - but behaviour change is hard ;).