Peat Moss

January 21, 1998

As a result of our WEB site, we had a call from Northern Bay Peat in Maine in regards to pressing peat moss. Expecting something like our local Spanish moss, we had them send some 5-gallon pails of sample. What we received more closely resembled mashed potatoes.

When we saw that it was not possible to squeeze water out by working it in our hands, we figured that a press aid would be required. A press aid is some fibrous material that is added so that water can be removed by a screw press. Typically people use rice hulls, cottons seed hulls, or peanut shells. On more expensive products like apple juice, they will use bleached paper pulp or Weyerhaeuser Silvacel.

For a press aid we used what we think should be available locally for the cost of hauling: paper mill sludge. It had some fiber content and it worked great.

The results of the moisture analyses were as follows:
Inbound as-received peat moss: 90% moisture
Material after blending 25% by weight
of paper mill sludge:
79% moisture
Press cake with light cone pressure: 72% moisture
Press cake with medium cone pressure: 63% moisture

We would not expect to operate at much below 63% moisture. This is because screw press capacity would drop off at high cone pressure.

The biggest technical hurdle would be to find a device that would feed the material into a press. The blend of peat moss and press aid had a tremendous tendency to bridge and not feed. We think a Twin Screw Supercharger would force the material into the press.

The client asked about using a Vincent triple pass dryer. We explained that the cost of operating a dryer would be prohibitive in comparison to the value of the final product.

Issue 14