Report after report shows that Raleigh, North Carolina is one of the fastest growing metropolitan areas in the country. One late 2016 study concluded that Raleigh metro’s population will grow by 72 percent in 25 years. Economic growth on that scale is fantastic for business and job opportunities, but it also puts municipal systems on notice that they too will need to keep up. One such operation is the city composting site. With 70 acres already permitted on a 160-acre capacity site, they certainly have the space to manage growing demand. And having just added a brand new Doppstadt SM 617 trommel to their workhorse BACKHUS 21.55 turner, they have the equipment to easily handle the high volume as well.
The site began in the 1990s when North Carolina passed a regulation banning green waste from the landfills. For much of the time since, the yard’s main outcome was simply as a diversion for all that material. Composting happened, but it wasn’t done with the kind of commitment required to generate meaningful results. John Ennis, whose formal title is operations and compliance supervisor, was brought on in late 2016 to run the site and bring it up to expectations. Already, there have been significant changes.
Mastering the Perfect Carbon-to-Nitrogen Ratio
“When I got here we were only using about 12 acres of our permitted 70, so we have been ramping up quite a bit since then,” he explains. “We average about 40,000 tons of intake annually, but that could be increased dramatically when we have our processes ready for it.”
Most of what the compost yard receives is standard yard waste from city collection services, augmented by some customer tipping and the occasional haul of storm debris. The consistency of source material helps make each day a little more predictable, but John admits that the team is still working through the best ratios of carbon and nitrogen to generate maximum yields.
“We’re still a fairly new team and are developing our best practices for blending,” he continues. “We have plenty of space to inventory material so it allows us the flexibility to stockpile brush until we get more nitrogen on our rows, for example. Our goal is to create the right blend with the proper ratios of carbon to nitrogen so the biological composting process can run its course.”
Acquiring the Perfect Stable of Equipment
In 2014, the city purchased a BACKHUS 21.55 turner, which made a serious difference in the effort and time required to turn rows. Late last year they added the new Doppstadt SM 617 trommel screen as well. The new equipment has allowed John to spend time focusing on composting methods without being distracted by underperforming machines or unexpected downtime.
“The BACKHUS turner was here when I got here, and it’s so great to have on our site. Seeing what other sites have to contend with to get their rows turned makes it clear to us how much more advanced our operation is,” John says. “The agitation of the BACKHUS drum contributes to the composting process quite a bit. You really notice the piles wake up after turning. And the capacity of the 21.55 will easily handle future growth as our demand continues to increase.”
Adding the Doppstadt trommel screen relieved the final pinch point in the operation that would occur when compost was ready to sell.
“The Doppstadt had about 25 hours on it when I got here, and we still had the older machine that it replaced on site,” shares John. “That old trommel is probably twice the size of the Doppstadt and generates half as much output. It’s amazing what that Doppstadt can churn out.”
John also appreciates the ease of serviceability on the Doppstadt.
“Clearly this machine was engineered with the mechanic in mind. Everything about it makes is easy to maintain, from the swing-out engine to the hydraulic controls. It allows us to take care of the machine without having to sacrifice production time doing it.”
Perfectly Positioned for Future Growth
With enough permitted space, and a reliable stable of equipment, the City of Raleigh is now well positioned to handle current and future demands on its organic processing. The compost site has been steadily growing at a rate of about 10 percent annually, but John believes they will be experiencing some rapid growth now in the next few years.
“In the last couple of years, as the compost yard has grown its intake, the process of building and turning windrows had not kept up. As a result, material was simply being stored on the site since we had the room but it should have been blending and windrowed,” adds John. “The market was wanting finished product and we didn’t have it to provide because too much of our source material was still in inventory.”
Now that the operation is set up for higher volume, John expects to see that finished product throughput pick up significantly. And not a day too soon either.
“The city itself would take more if we could make it. We have a lot of outside customers coming to pick up product that want more. Now that we have proper equipment, we will be able to make mulch and soil blends too. Creating high-value products, rather than just seeing these materials as an afterthought, will allow us to meet current demand and generate more volume for the future.”
John grew up on a farm. He may not have a long professional history in composting, but he’s been around the true purpose of organics recycling for his entire life.
“It’s just an obvious and natural cycle,” he concludes. “As farmers, anything we could put back in the ground that could help make next year’s crop better, we did. There is no reason at all to throw away organic material.”