Clean cookstove projects, one of the most popular types of carbon-offset schemes, are probably overstating their beneficial impact on the climate by an average of 1,000%, according to a new study.
Every year, an estimated 3.2 million people die prematurely from household air pollution caused by cooking with smoky fuels such as wood, paraffin or kerosene, which produce about 2% of global greenhouse gas emissions.
Such cooking also drives deforestation and habitat loss, as people cut down trees for fuel. By switching from smoky fuels to cleaner alternatives such as electric cookers, cookstove projects in the developing world can have major health, social and environmental benefits: improving air quality, reducing the amount of time people spend collecting wood and slowing the loss of the world’s forests.
To fund these initiatives, which are often dubbed “nature-based-solutions”, projects sell on the greenhouse gas reductions as carbon credits. Each credit represents a tonne of carbon dioxide – which companies then use to “offset” their emissions, sometimes claiming their products and services are “carbon neutral”.
Improving access to clean cooking facilities features in the UN sustainable development goals, and cookstove-based credits have been on the rise. From May to November last year, figures from the Berkeley Carbon Trading Project show cookstove projects issued the most new credits in the market, comprising about 15% of the total. They also registered the most new projects.
But a new study published in the journal Nature Sustainability has found that cookstove projects that generate carbon offsets are overstating their climate benefits by 1,000% on average.
The findings have been disputed by Verra and Gold Standard, both leading certifiers of carbon credits, which say the evidence in the study does not back the conclusions drawn.
While many offsetting schemes said they were funding “clean” cookstoves, most did not meet World Health Organization standards, according to the assessment by researchers at the University of California, Berkeley.
Analysis of common rules to produce the offsets found that projects were allowed to overstate how often people used the stoves and the resulting benefits for nearby forests, dramatically inflating the benefit to the climate and biodiversity, researchers said.
The findings draw on previous research on the impact of cookstove schemes by development economists, who found they often failed to produce their potential benefits in practice.
Despite the problems, the researchers said the rules on producing carbon credits could be reformed to provide a meaningful source of climate finance that companies could trust. They offer a method that clean cookstove projects can use to avoid overstating their impact, which some of the cookstove companies have already adopted while the paper has been in peer-review.
The lead author, Annelise Gill-Wiehl, a PhD student at the University of California, Berkeley, said: “Comprehensively assessing the five major cookstove offset methodologies, we find that our sample of 40% of the market is 9.2 times over-credited. Extrapolating to the entire market, we find roughly 10 times over-crediting.
“Over-crediting replaces direct emission reduction and other more effective climate mitigation activities, even if some reduction is achieved. Lack of trust weakens the market,” she said.
The study comes amid intense scrutiny of the unregulated voluntary carbon market, with concerns that many schemes are producing huge amounts of worthless carbon offsets.
Barbara Haya, director of the Berkeley Carbon Trading Project, who has been researching carbon credits for 20 years and is co-author of the study, said researchers hoped the quality of credits could be improved.
“A carbon credit market built on exaggerations is destined to fail. Our hope is that the specific recommendations we offer can help make clean cookstoves a trusted source of quality carbon credits,” she said.
Gold Standard, a major carbon credit certifier, disputed the findings of the study. The researchers found that Gold Standard produced the best-quality method for producing offsets, which directly monitored use of stoves, and was only 1.5 times over-credited.
“Gold Standard welcomes academic scrutiny and has engaged extensively with the authors of this study,” a spokesperson said, adding that it had already incorporated some of the ideas and changes discussed in the research.
“It must be stressed that the study neither studied, nor found, over-estimation. The evidence provided does not back the conclusions drawn – which are at odds with the wider academic literature and expert view on this subject.”
In a statement, Verra, the world’s largest carbon standard, said it was disappointed to see continued attention on the study. The non-profit organisation is developing a new methodology for cookstoves, and said the findings did not directly relate to its current methods.
“As detailed in a September 2023 open letter from researchers and experts, there are numerous substantive concerns about this research,” it said.
Verra said the proposed methodology it was developing included changes that “reflect current best practices of project design and implementation”, as well as a number of measuring techniques to check how much the stoves were being used.
“Carbon finance is critical for the implementation/sustenance of improved cookstove projects, which provide access to sophisticated cooking methods and a range of other sustainable development benefits to disadvantaged communities,” it said.
Ben Jeffreys, chief executive of the cookstove company ATEC, which is working with UC Berkeley to measure the benefits more accurately, said he supported the research. “Ensuring ‘a tonne of emission reductions is actually a tonne’ is critical if we are to reach the full potential of the cookstove carbon-market sector,” he said.
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