Optimizing Curing to Save Time and Space

Added: 2026-05-24

[00:00:00]Can we screen compost after 4 weeks of aerated composting, then complete the curing process in an additional 4 weeks?

[00:00:09]If we could, it would drastically reduce the volume of compost needed to be cured and reduce the amount of space required.

[00:00:19]We can.

[00:00:20]The Comox Valley Regional District constructed a biosolids compost facility in 2004.

[00:00:27]It was an aerated bunker system without door curing. The curing process included windrows that could be turned with a compost turner.

[00:00:36]There were at least three problems with the curing process.

[00:00:40]First, it required a lot of space, which eventually needed to be used for other purposes.

[00:00:46]Second, outdoor curing in a high rainfall climate results in wet compost that's difficult to screen during spring when the demand for compost is highest.

[00:00:58]Third, curing needs to occur on an impervious surface with leachate containment in the high rainfall climate.

[00:01:06]What was supposed to be a simple and inexpensive curing process ended up being costly and ineffective.

[00:01:15]Several improvements were made since 2004.

[00:01:19]First, the bulking agent is kept dry to provide more optimal compost mixes for better composting, especially during the wet winter months.

[00:01:29]Second, the mixing process was improved to save time. We covered that in a previous video.

[00:01:37]Third, the compost in the bunker is mixed after 3 weeks to redistribute moisture, then further aerated for another week.

[00:01:46]Fourth, heat exchangers are included in the primary aerated bunkers to help dry out the compost faster during the wetter winter for The compost is now screened to 3/8 inch after 4 weeks in the aerated bunkers when the compost is dry. The overs are recycled as bulking agent and inoculates the new mixes.

[00:02:08]This reduces wood waste requirement and speeds up the compost process.

[00:02:13]After 4 weeks of aerated composting, the moisture content is below 40% which makes for faster and more efficient screening.

[00:02:23]After screening, the compost looks good.

[00:02:26]It doesn't have odor, it's dry, but it's not mature.

[00:02:30]At this point, the Solvita maturity index is five with a carbon dioxide respiration rate of 6.6 mg of carbon dioxide carbon per gram of organic material.

[00:02:42]Still immature.

[00:02:44]These screen fines now enter a 4-week active curing process that includes moisture management, aeration, and mixing.

[00:02:53]The moisture content after curing is 45%.

[00:02:57]The Solvita respiration index is seven and the respiration rate is 2.2 mg of carbon dioxide carbon per gram of organic matter per day.

[00:03:07]The compost is now mature and goes out as soon as it's ready.

[00:03:12]You can easily see the difference that the 4-week curing process makes. This active curing process saves space, saves time, and produces a dry and high-quality product in 8 weeks.

[00:03:25]Curing compost is not an afterthought.

[00:03:28]It needs to be part of the planning for an optimal composting process.

[00:03:33]And curing compost is not like aging wine or cheese. It's about paying attention and optimizing the microbes in our compost.

[00:03:42]My name is John Paul, a soil scientist and compost specialist.

[00:03:47]Thank you.