On Climate Change Mitigation: SOIL Research Updates

bags of compost

As the devastating impacts of climate change continue to mount around us, especially in vulnerable frontline communities like the ones SOIL serves in Haiti, we’re more motivated than ever to grow SOIL’s climate-positive sanitation solution, which transforms a public health crisis facing cities around the world into a restorative solution for the planet. Visit this page to learn about how SOIL's regenerative sanitation service helps communities adapt to the impacts of climate change.

On Mitigation:

During the ecological composting process, the microbial revolution that takes place in the compost bin eliminates harmful pathogens and transforms human waste into safe, nutrient-rich compost. As the microbes do this important work, they breathe out greenhouse gases, mostly in the form of carbon dioxide, methane, or nitrous oxide, depending on the conditions of the compost pile.

SOIL's research partners Dr. Rebecca Ryals and Dr. Gavin McNicol hypothesized that SOIL’s treatment process would have a smaller greenhouse gas footprint compared to other waste treatment alternatives because the compost process is aerobic, or done in the presence of oxygen. Aerobic conditions foster microbial life that breathes out carbon dioxide, as opposed to methane which is 34 times more powerful at trapping heat. In contrast, pit latrines produce anaerobic environments and are hotspots of methane emissions (they are responsible for 1% of global human-caused methane emissions). So, quantifying greenhouse gas emissions and observing the underlying conditions in which they are produced is critically important in understanding the potential for ecological sanitation systems to reduce emissions.

The research team measured greenhouse gas emissions from SOIL’s two composting treatment facilities, along with nearby waste stabilization ponds and a field where waste was known to be disposed of without further treatment. What they found was that the waste stabilization ponds produced very little nitrous oxide, but massive amounts of methane gas. At SOIL’s composting site, a small portion of the initial carbon and nitrogen embedded in the incoming material escaped to the atmosphere as methane (0.1 – 0.5%) or nitrous oxide (0.05 – 0.3%). Ultimately, both of SOIL’s  waste treatment sites had smaller greenhouse gas footprints than the waste stabilization ponds and field. This means that not only is SOIL’s composting process good for the climate in that it’s emitting less greenhouse gases into the atmosphere, but it also means that those valuable carbon and nitrogen molecules that are retained in the compost can instead be returned to the soil to support plant growth.

Reduced Greenhouse Gas Emissions


Combined methane and nitrous oxide emissions (in units of CO2 equivalents to factor in difference in global warming potential) were lowest at both of SOIL’s waste treatment operations compared to waste stabilization ponds and the untreated disposal of septic and latrine waste.

The researchers noticed something else that was very interesting about SOIL’s compost operations. At SOIL’s composting site in Port-au-Prince, the gases emitted was 12 times higher than the site in Cap Haitien, mostly in the form of methane emitted from the compost piles. This was an exciting discovery because it indicates that there are ways to optimize the compost process to minimize gaseous losses. Since methane is emitted in anaerobic environments, they hypothesize that practices that reduce the moisture content and improve air flow of the piles will minimize emissions. So, the team spent another year conducting controlled experiments to test various compost management practices that could influence microbial activity and greenhouse gas emissions. Stay tuned for updates on what they learned later this year!

Learn about how SOIL’s restorative sanitation systems help communities adapt to conditions created by climate change here: On Climate Adaptation. Many thanks to Dr. Rebecca Ryals, Gavin McNicol, Kate Porterfield, Stephen Heisey, and Naomi Jun.

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