What are the primary takeaways of your research?A
What we did is compare the current trajectory of fuel use in low- to middle-income countries – which largely uses what are considered unhealthy fuels – to a world in which those populations transition to fuels that are considered entirely clean at the point of use over the next 20 years.
What we found is that if people switch mostly to grid-based electricity or liquefied petroleum gas (LPG) or a combination of those, we will see large reductions in cumulative carbon dioxide (CO2) emissions and CO2 equivalents, as well as a dramatic reduction in pollutants that inflict potent near-term damage to the climate, known as short-lived climate forcers. This will likely result in a cooler planet at the end of this 20-year transition period.
So we’re comparing this business-as-usual world to a fully clean cooking world.
The reason we’re doing this is because there’s a lot of interest in shifting people over to cleaner cooking technologies. Polluting fuels such as wood, charcoal and kerosene carry a huge burden on health and the environment, but there are questions about which fuels might be the best choice.
Because LPG is derived from either petroleum or natural gas, and grid-based electricity, for most of the world, is also produced from fossil fuels, people raise concerns because anything that’s related to fossil fuels poses a risk to the climate. So we’re trying to understand whether this transition to LPG, which we’re very confident would result in lower health risks, would carry a climate burden – whether it would lead to additional warming or not, and if so, how much? Or if it doesn’t, how much less warming would there be?
We made several different scenarios, and I’ll focus just on the on the LPG-dominant scenario for now. We took the low- to middle-income countries and built a model in which we forced everybody who would be using polluting fuels in the future, based on our business-as-usual assumptions, to use LPG, gradually between now and 2040. What we found was the transition would result in a reduction of nearly all pollutants we were tracking. Some dramatically so, almost to zero, and some moderately so.
Specifically, we found that cumulative emissions of CO2 equivalent would decrease by about 3 billion tons. This is equivalent to the annual emissions from about half a billion cars. That’s about one-third of the automobile fleet on the planet today.
We also find a dramatic reduction in short-lived climate forcers, specifically black carbon, but also organic carbon, volatile organics and carbon monoxide. When you stop emitting those, particularly black carbon, you get rapid cooling because they impose an immediate climate response.
These findings are relevant for billions of people. Give us a quick picture of the population studied here or who is affected by this research and how they’re cooking.A
What we see today throughout low- and middle-income countries is predominant reliance on what the World Health Organization considers polluting fuels. Those are biomass-based fuels, wood and charcoal and crop residues, as well as fossil coal that people use in a small group of countries, and kerosene. Cooking with biomass causes about 3 million premature deaths each year due to household air pollution.
Mainly we’re looking at sub-Saharan Africa and parts of South and East Asia, as well as some of the poorer countries in Latin America and Central Asia.
We see some active fuel transitions underway in some countries. Our business-as-usual scenario accounts for lessening dependence in some regions, but for sub-Saharan Africa, the population that’s reliant on solid fuels is still expected to grow for the foreseeable future. If we do nothing, we’ll see several hundred million more solid fuel users in sub-Saharan Africa – another United States’ worth of population – in the next 20 years. So it’s particularly relevant for that region.
If solid fuel use is declining in other parts of the world, why is it set to grow in sub-Saharan Africa?A
Out of the whole world, that region is at the earliest stage in what might be considered a natural progression of an energy transition, and a lot of it boils down to resource availability – poverty, lack of infrastructure and lack of ability to deliver what we consider modern energy services.
Much of the discussion on cooking fuel centers around climate polluting emissions and health impacts, but how else does a reliance on biomass affect people and the planet?A
A couple different ways. One, when woody biomass – so trees, shrubs, et cetera – are harvested, the landscape can typically recover because landscapes have the ability to generate that biomass. But when the resources are harvested at a rate that’s faster than the landscape can naturally produce, then you see a degradation over time. You see stocks of biomass slowly declining. You take a little, a little comes back. You take a lot, only a little still comes back. Overharvesting wood fuels can lead to degradation, so you get a decline in wood stocks and carbon stocks that can have spinoff effects on biodiversity and other ecosystem services. It can affect hydrology, runoff or evapotranspiration, things like that.
And then relying on food fuel also places a huge burden on people’s time. In many places, there’s a gendered component to that and women or young girls are the ones collecting wood. As fuel becomes more scarce, collection times become longer, distances required become longer. It’s a physical burden and also places increasing demand on people’s time. In some places, there’s also a risk of gender-based violence associated with fuel collection.
These spinoff effects don’t necessarily apply everywhere, but they’re certainly relevant for millions of people and worth paying attention to.
Can you describe the various scenarios explored in this study?A
I mentioned and described in a little detail the business-as-usual scenario. We focused mostly on full transition scenarios, which we realize is not possible, but if we if we wanted to describe the impact in terms of emissions, this would be an upper bound.
So we defined three different full transition scenarios – one in which, like I said earlier, we replace all polluting fuels with LPG by 2040.
In another, we replace all polluting fuels with electricity, but allow LPG to continue to grow at its business-as-usual rate, which in many regions is already quite high. So in that scenario, we still find a roughly equal mix of electricity and LPG users in 2040.
And then in a third scenario, we replaced everything with electricity, including LPG, to see what would happen.
Then we made one more realistic, but very modest, scenario that we called our intermediate scenario, and in that, we just doubled the rate of LPG uptake.
Our intermediate scenario doesn’t result in much difference, but you could argue that it’s probably the most realistic, unless people will look at this research and say, “Oh, we’ve got to mobilize trillions of dollars to get this done.” The intermediate path still sees significant emissions reductions, but doesn’t really lead to much climate impact.
Did one stand out as most impactful, or are looking at nuanced trade-offs with each scenario?A
If we focus on the extreme scenarios, overall, they all have relatively similar impacts on CO2 equivalent changes, so CO2, methane and nitrous oxide. They all have similar, very dramatic reductions in short-lived climate forcers, specifically black carbon and organic carbon. And similar impacts on temperature. Where they differ are in emissions of some pollutants that have a minimal climate impact, but have a measurable health impact.
Take black carbon, which is a component of soot or particulate matter. That’s a concern for climate. But just breathing particulate matter is really bad for people, and that’s the main source of health impacts from household air pollution and from burning polluting fuels. And when we talk about this burden of disease, millions dead every year, that’s mainly from particulate matter. There are other pollutants, though, that also pose a health concern.
If you switch from burning wood to burning gas, you increase NOx emissions (nitrous oxide and nitrogen dioxide). There’s no avoiding it. NOx can cause respiratory problems and is a concern for health, but the impact is small in comparison to the impacts from burning wood or charcoal indoors.
Here’s where the trade-offs come in. If we take an LPG-heavy route, we get more NOx, but a lot less of nearly everything else. If we go with grid-based electricity, we get less NOx, but more sulfur emissions in the form of sulfur dioxide and other sulfur oxides (SOx for short). Worldwide, 40% of electricity production comes from coal – in China and India it’s nearly 80%. Coal contains sulfur, and while it can be controlled, there are still some emissions, particularly in LMICs where regulations aren’t as stringent as in the US or EU. So with the current and near-term future grid, you get higher SOx emissions. Like NOx, SOx causes respiratory problems. It also contributes to acidification and other environmental impacts.
So these are two major trade-offs depending on which pathway you take. But we need to stress that the health impacts of both NOx and SOx pale in comparison to cooking indoors with wood or charcoal.
Do we know some of the best practices or best ways to roll this out? Or is this something that needs more research?A
If you look at the countries that have succeeded in achieving widespread access, many, but not all, have relied on some form of subsidy. That’s a risky path. It’s costly, they’re hard to remove once they’re in place, they’re politically fraught. But it’s worked in in some places, and it’s worked better in some than others.
There are specific ways that you can roll out subsidies that are recognized to be better than others. For example, with a blanket subsidy where you just cut the price of LPG for everybody and you cut the price at the point of sale, you’re selling it below cost and the government pays the difference to the distributors or the producers. That tends to be captured by wealthier people who don’t necessarily need the subsidy or who would be buying it anyway, and it also tends to divert resources away from its intended use. You’ll find commercial outlets using it for restaurants, or that it’s used to fuel automobiles. So that’s not the best approach. And that is the approach that many Latin American countries used in the past, although many of them have introduced reforms.
India is a good example of rolling out a subsidy that is more targeted and minimizes the potential for fraud. In 2016, they rolled out a program specifically targeting poor households. They had already seen a lot of growth in LPG, which had become quite popular for wealthier, middle-class households. But it wasn’t penetrating the poorest of the poor.
(Prime Minister Narendra) Modi’s government rolled out a huge scheme to encourage adoption of LPG among 80 million rural households that are all considered below poverty line. What they did was attack the two cost streams associated with LPG: the initial purchase of the stove and first fuel cylinder, and the continuing cost of every refill. The government heavily subsidized the initial acquisition, so a basic stove, regulator and first cylinder were essentially free for poor households. It they wanted a slightly fancier stove, they could buy it at discount and finance the rest on favorable terms. They also then subsidized subsequent refills. The government linked the refill subsidy to a bank account to minimize fraud. So when people purchased refills, they had to purchase them at full price and then get the subsidy as a rebate paid into their bank account as opposed to just buying at a reduced price.
And they did it. India met their target. By mid-2019, 80 million households had signed up. That’s nearly the population of the United States, assuming four people per household.
But they didn’t necessarily keep refilling the cylinders. It’s not a resounding success, but if you look at energy transitions in history, they tend not to play out over years. They tend to play out over decades. It definitely accomplished a necessary first step towards providing universal access, which is what the SDGs say we should all be aiming for, and lays the foundation for broader, deeper transition in the future.