• Michael Sherpard

Dinner for Four Billion: A Biomass Gasification Manifesto

Updated: May 7

Four billion humans--that’s half of us on the planet--cook with wood, charcoal, dung, and other biomass.[1] Chronic exposure to unhealthy levels of cooking smoke is one of our greatest sources of misery. It is the leading environmental risk factor for early death in poor countries. We’re talking up to four million premature deaths a year[2]—more than from malaria, tuberculosis and HIV combined. Cooking with biomass costs $2.4 trillion a year in damaged health, lost productivity, climate change, environmental degradation, and time poverty.[3]

In some respects, the challenge is very simple. We must reduce humanity's exposure to cooking smoke. But how?

One attractive option is electric cooking, which is smoke free at the point of use and can be powered by renewable sources. [4] However, providing reliable and affordable electric service across the global south that is robust enough to meet the high power demand of cooking will be very costly and will take decades. Even then, because of longstanding cultural traditions and preferences, many people will continue to use flame to prepare much of their food. So even as we push for broader access to electricity, we must also pursue cleaner forms of fire for our kitchens.

The best know options for “modern” flame based cooking in developing economies include LPG, ethanol, and biogas. Each burns fairly cleanly, but they all have drawbacks and constraints, which I will address in future posts.

There is another lesser known option, however, with the promise of solving the clean cooking challenge for more people, at lower cost, more quickly, more sustainably, and across more geographies than all the other leading candidates--biomass pellets fueling fan-powered gasifying stoves.

Pellet gasification generates a clean, controllable flame like that on a gas stove. It meets international health guidelines, rivaling LPG in cleanliness.[5] The fuel can be locally and sustainably grown. Gasification is so efficient it reduces biomass needs by ninety percent relative to charcoal. So it can dramatically ease pressure on over harvested forests and mitigate climate change while preserving rural livelihoods.

If gasification is so great, why bother making pellets? Why not just use ordinary wood for fuel? The reason is that for gasifying stoves to perform best, they need a fuel that is consistent in form factor, size, and moisture content. Random sticks won’t work well. Instead, wood and other biomass needs to be broken down into tiny particles the consistency of sawdust, dried to a specific range of moisture content, and put through a pelletizing machine akin to a giant pasta maker. Out comes cylindrical pellets a couple inches long and roughly the diameter of a pencil. The intense heat within the dies plasticizes the lignins in the biomass, creating a smooth outer coating that helps repel moisture and keeps the pellets durable and intact for long periods during bagging, transport, storage, and use.

The most economical way to make pellets is at industrial scale, in factories running close to full time, producing four or more tons of pellets per hour. The capital cost of such factories, of trucks and other equipment to transport and handle biomass feedstock and finished pellets, and the gasifying stoves to cook with the pellets, totals around three hundred dollars per household served. That may sound like a lot, but it is considerably less than the cost of expanding electricity access or the LPG supply, distribution, and appliance network to serve everyone, particularly the rural poor.

In addition to lower capital cost than electricity and LPG, pellet gasification has lower fuel cost than other cooking solutions, including charcoal. This makes it very attractive to cash strapped cooks. Pilot programs in the countryside have shown that the rural poor prefer it to cooking with gathered firewood and are willing to barter gathered wood in exchange for pellets.

It is time for the international community to get serious about supporting clean, cost-effective and modern biomass gasification cooking and to see how favorably it can compete with other cooking fuels. It can’t be profitable at small scale. Like grid electricity and LPG, biomass gasification needs to be deployed at utility scale to reach full economic viability. This will require bold action by donor agencies and other funders to provide sufficient concessionary capital to demonstrate and de-risk this approach at commercial size. Once proven, it can attract private investment to fuel further growth.

Fortunately, some pioneering companies are paving the way with pellet gasification cooking in Africa. In future posts we’ll look at some of these ventures, their business models, the lessons they offer for the future, and other key issues in the quest to provide clean cooking for all people.

[1] World Bank, The State of Access to Modern Energy Cooking Services, at p. xx states that 2.8 billion completely lack access to modern cooking, and 1.25 billion have limited access to a modern solution but still rely heavily on traditional cooking. [2] World Health Organization, Frequently Asked Questions Ambient and Household Air Pollution and Health Update 2014 estimates 4.3 million premature deaths per year from household air pollution in 2012. The Institute for Health Metrics and Evaluation puts the count at 1.6 million premature deaths in 2017. https://ourworldindata.org/indoor-air-pollution cites indoor air pollution as the leading environmental risk factor in poor countries. [3] [1] at p. xvii. [4] World Bank, Cooking With Electricity: A Cost Perspective, 2020. [5] Wyatt M. Champion and Andrew P. Grieshop, “Pellet-fed gasifier stoves approach gas-stove like performance during in-home use in Rwanda,” Environmental Science & Technology, May 1, 2019.


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