Laurel Valley Farms moves from Conventional to Aerated Phase I Compost
Excerpt from the August 2001 issue of Mushroom News Magazine
9/27/2001

Original article by: Glen Cote - General Manger, Laurel Valley Farms and Carla Blackwell McKinney - Vice President, C-J Mushroom Co.
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In North America, the construction of Aerated Phase I Composting systems has lagged behind several other areas of the world such as Europe, Eastern Europe and Australia. This is changing primarily due to urban movement into rural areas, resulting in odor complaints and in some cases, legal battles from residents. This situation has occurred in several provinces in Canada. A few growers scattered throughout North America have recently been forced into converting composting systems in order to survive.

At Laurel Valley Farms, we faced a similar situation two years ago after a large residential development was constructed next to our compost wharf. From the start, we sought to establish good working relations with our new neighbors, but we also wanted to take an active position in managing our composting operation for any future environmental regulations. So we decided to put the proposed advantages of aerated compost to the test.

In 1999, we began working on a plan to build an aerated system with the intent to first learn how the system worked and then compare the parameters and performance of the aerated compost to our conventional compost over several different seasons. If the results were positive, we were prepared to complete the transition of our farm to totally aerated compost at a later date.

Laurel Valley Farms is a composting facility owned and operated by a group of 10 different mushroom growers located in southern Chester County, PA. We are a large composting operation and we make and ship more than 6,000 cu.yds. per week of compost or roughly the equivalent of 4,500 metric tons of material. Our compost formula consists of 60 percent hay; 40 percent stable bedding blend supplemented with poultry manure. All of the mushroom growing operations we supply compost to are Pennsylvania double wooden bed farms except one that is a Dutch style shelf farm. Phase I compost is shipped from our facility to the individual farms where it is filled into wooden beds and the Phase II process is completed. Each farm manages its own Phase II process and growing operation based on its individual market needs and requirements.

Therefore, compost produced at Laurel Valley must meet the varying needs and growing facilities of all our different growers.

During the early stages of our planning process, we made a list of requirements we felt were necessary to help us decide what kind of aerated composting system to operate.

After studying several different manufactured composting systems available on the market, we decided to build covered bunkers or silos using a high-pressure nozzle floor for aeration. The three-sided covered structure gave us protection from the elements and allowed for future expansion into totally indoor composting if and when it was needed.

Each bunker measures 115 x 30 x 26 feet and can produce up to 1,300 cu. yds. of finished compost. The high-pressure fan system generates pressures up to a 19-inch water column or close to 5,000 PA. This allows us to empty and fill our tunnels with front-end loaders up to a height of 16 ft. The self-contained nature of the system allowed us to build two bunkers to be used as the test system while we continue to make compost the conventional way. With this system, we also could add additional units as needed until we reached full conversion or if we wanted to expand further sometime in the future.

The most important component of the bunker is the control system. Computers measure and monitor the oxygen concentration and the compost temperature. The computer turning the fan on and off on a cycle controls the oxygen concentration in the compost. This ultimately controls the compost temperature. The fan cycle times are adjusted by the computer based upon the oxygen and compost set points we want to maintain in the compost. At this point, we do not use frequency drivers to vary the pressure of the air in the bunkers as the oxygen demand changes.

SUMMARY:

In the fall of 1999, we built two bunkers to test the composting process and to compare it to our conventional process.

After the construction of the test bunkers was completed, we began producing aerated compost. At first, we made compost for one double per week for the first month. Then we made compost for two doubles per week until the first trial crops were harvested. We continued along this approach until we made up to 30 percent of our compost production from the two bunkers. Meanwhile we observed and learned how to operate the system.

We continued to make comparisons of the two composts through the fall of 2000. We analyzed the two composts at fill and spawning for moisture, ash, nitrogen and ammonia. In addition, we tracked its progress through Phase II and into production. What we found was that although the aerated compost cycle was significantly different and shorter than the conventional cycle, as we had hoped, most of the results did not vary significantly at all. In fact we found results from both composts to be quite consistent. After several months of comparisons we concluded our test project was a success.

It became obvious to us early in the testing process that the compost we were producing in the aerated system was good quality and easy to manage both from the perspective of the grower and those of us on the composting wharf. We ran the test project for six months and reviewed the data. As the data was being evaluated, we were confident we could move forward and completely convert to aerated Phase I compost. Five additional bunkers were built in the fall of 2000 and beginning with the first of the year we began shipping 100 percent aerated compost.

Since the beginning of our test program we have found many of the proposed advantages of aerated composting have proved to be true.

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Permission to include this article in the Double T Equipment website granted by Glen Cote, Carla Blackwell McKinney, and The American Mushroom Institute. Visit the American Mushroom Institute online at www.americanmushroom.org.

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