Windrow Composting: What We’ve Learned from the Pilot Research and Where We’re Going

Over the past year, the SOIL research team began experimenting with windrow composting, as a method for making our waste treatment and composting process faster. The goal of the research was to improve the efficiency of the composting process in order to be able to accommodate more waste at our site, as well as decrease operational costs. After months of trials, we are excited to share our latest update on the research!  

What’s Windrow Composting?

Windrow composting involves emptying containers of waste (and bagasse) collected from households on SOIL’s service into a pile on the ground (and elongating it into a row) as an alternative to the lined bins we currently use for composting. Following the emptying process, the windrows are turned at least once a week to increase aeration and decomposition to facilitate treatment and transformation of the waste into compost.  

The Experiment

For the purpose of this experiment, SOIL’s research team collected data from 7 experimental piles between May and December 2021, looking at a range of parameters such as maturity age, yield, and quality. Each pile was formed directly on the ground, and covered with non-woven geotextile to maintain humidity and prevent vectors. After 10 days during which the pile temperature rises and kill pathogens, the piles were turned twice a week for a month. After a month, the piles were turned once a week until maturity. Based on visual evaluation by the team, the piles were also watered on demand to maintain desired moisture and humidity levels. After completing the first round of research, the experiment was duplicated again to verify results.  

Results

From these experiments, SOIL obtained some incredible results:  

• Windrow piles are ready in half the time. Windrow composting produced mature compost in 3.2 months on average compared to at least 6.5 months with the standard bin process.
• Compost yields increased by 20%.
• And, according to the site supervisor’s visual inspection, the compost produced through windrow composting has a higher quality with finer particles, and a richer color than the compost produced through bin composting.

 Additionally, with this research, the team has realized that turning the windrow piles early on makes the process less difficult for the composting team: gasses and heat do not accumulate as much at this stage, and the waste is not as compacted.  

“[The team reported that] windrow piles are easier to turn compared to opening bins.” Joasil Luckny (Tidou), assistant site supervisor  

Furthermore, these results indicate that we could potentially scale up the EkoLakay service and reach SOIL’s objective of 8,000 households in the service, without having to obtain more land or build a new site.  

Windrow vs Bin Composting

This experiment has allowed SOIL’s team to gain important insight into the benefits of windrow composting in comparison to our current method of bin composting. Overall, SOIL’s comparative cost analysis shows that bin composting is more expensive than windrow composting – regardless of whether we use a fully manual pile turning process, or invest in mechanical turning equipment. The reduction in treatment time and minimal infrastructure requirements makes manual windrow composting 57% less expensive at our current scale, and to 64% less expensive at our goal of 8,000 households. The ability to mechanize turning the piles comes with a larger up-front cost, but it is estimated to substantially reduce total costs further once established.  

What’s Next

The research team is now moving forward to scale up the project. A transition plan has been developed to phase-out bin composting without having to disrupt the waste treatment service, and we hope to start operating with windrow composting before the end of this year. Once the transition begins, we’ll look into optimizing the turning frequency to maximize results and minimize costs, while also looking into turning equipment to reduce labor. In the meantime, SOIL’s research team is working with an ergonomics consultant to improve bucket emptying processes to ensure that this process is effectively designed using a human-centered approach that minimizes any risk to workers health and safety.  

The SOIL team is excited about implementing the new treatment methodology as a result of this research and the potential it has for our service and the future of waste transformation. SOIL is dedicated to a zero-waste system that can both help protect Haiti from waterborne illness and support more resilient soils that can help Haitian farmers avoid the negative impacts of droughts and other climate events, while increasing food security. We are proud to be a part of the movement to build a greener and more resilient future for Haiti, and we look forward to sharing more updates with you soon!