Optimizing the Composting Process: Research Updates from Port-au-Prince
Gavin McNicol, who has long been active in SOIL’s research partnership with Dr. Rebecca Ryals, had the opportunity to visit us at SOIL’s composting waste treatment site just outside of Haiti’s capital city in earlier this year. In 2016, Gavin joined Dr. Ryals ongoing research investigating SOIL’s climate impact and helped spearhead research on the optimal conditions for the composting process. Gavin took a moment to share an update on the ongoing research as well as a sneak peek on a new research project that we are working on in Port-au-Prince with SOIL’s readers in this guest blog:
Wrapping Up Research on Optimal Composting Conditions
After over a year of moving around for different postdoctoral research positions, I was finally able to come back and visit SOIL in Port-au-Prince. My goals for this trip were to wrap up work we had begun two years ago, help set up a new experiment on the contents of liquid that drains from compost piles, and, of course, to reconnect with my friends and colleagues at SOIL!
The composting process is driven by microbial communities in the compost pile that are sensitive to conditions like temperature and oxygen. We installed sensors in the composting piles in Cap-Haïtien alongside SOIL’s composting team to better understand optimal composting conditions throughout the thermophilic composting process, initially hoping to gather three to six months of data. In the end, we have collected data from the piles for over a year!
Now it’s time for us to analyze all the data that we have collected and compare the dynamics of greenhouse gases that we have studied in other research to the dynamics of temperature and oxygen. We are particularly interested in emissions of methane and nitrous oxide, the two most important non-carbon dioxide greenhouse gases, both affecting the climate mitigation potential of ecological sanitation.
We hypothesize that greenhouse gas emission will generally be higher during the peak temperatures of the thermophilic composting phase, with methane emissions dominating when oxygen is low, and nitrous oxide increasing when oxygen is more available. We will share updates from this research when we have them. Check back to the SOIL blog for the results and to learn more about what it means for SOIL’s treatment process’ comparative climate impact!
Moving Ahead on New Research
During my visit to SOIL’s composting site at Titayen (just outside of the capital, Port-au-Prince), I helped set up another research project to help SOIL make data-driven decisions for composting infrastructure investment in the future, with the potential to help inform best practices for ecological sanitation practitioners around the world.
Gas emissions aren’t the only way that carbon and nitrogen is lost from compost piles throughout the composting process. The leaching of liquid out of the base of the compost pile also represents a flow path for nutrients and potential pathogens. Though SOIL mitigates the risk of environmental contamination by treating runoff onsite, we want to better understand how to prevent the run-off from happening in the first place.
During this trip, I was able to help launch a new experiment to assess how using different lining materials in composting bins impacts the leaking from the piles. This data will help ecological sanitation services like SOIL decide where and when they can use a natural soil lining as a base, and when they need to install a more impermeable material like cement. We are using nine tension lysimeters to measure the rate that leached liquid filters down into the soil underneath the pile and and what the liquid contains.
After giving the soil a few months to settle around the lysimeters, we will start collecting data from new compost piles and the open control area. In the meantime, we have plenty of work to do finalizing our results from the greenhouse gas experiments and continuing to build a body of scientific knowledge to support the replication of ecological sanitation systems around the world.
Read more about SOIL’s ongoing climate change research here.
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Feature photo credit: Gavin McNicol
May 12, 2019 (2:53 pm)
We place corrugated glassfibre (not fibreglass) sheets at the bottom of our wood composting boxes and then cover the bottom 20% (sides) with builders plastic – or any waste plastic that will stop urine or water leaking from the bottom of the box. It can also be replaced by placing 35mmx35mm brandering (wooden strips) approximately 5cm apart at the base of the box, and cover it with durable plastic sheeting, again covering approximately 30cm of the sides as well. The corrugated sheets (run-of ends)protrude the plastic and the one side of the box by 13-15cm. We position a gutter under the run-of and collect the liquid in a container – pouring it back onto the compost. Although we are still trying to find a Varsity or any research institution to assist us with a research project – our trial and error compost is moist and full of earthworms after 5-6 months in summer and 7-8 months in winter.
June 23, 2019 (11:01 am)
Is this at the SOIL composting facility in Haiti?
What volumes of leachate are being collected? Is the pile exposed to the rain?
I think that the soil under the compost pile can deal with small amounts leachate, without contaminating groundwater (as long as the site is not too sandy) and that this ability will improve over time, as the microbial community develops. Also, deep-rooted plants and trees can be planted around the site to improve this treatment and recycle the nutrients present.