having a desired moisture level for example after washing corn bran fiber it can be ground into a fiber product typically the corn bran fiber is sufficiently dried before grinding so that the fiber can be handled in an efficient manner if the corn bran fiber has too high of a moisture level it can be difficult to handle and process oftentimes the grinding process occurs at a temperature to inhibit bacterial growth in the grinding and related equipment as well as the final product such elevated temperatures can further dry the fiber to an undesirably low moisture level a method of processing e g grinding a corn bran fiber according to the present invention can selectively adjust the flow rate of one or more recycled gas streams as well as the humidity flow rate and temperature of a fresh gas stream to create a combined gas stream that is exposed to the corn bran fiber during such processing so as to provide a desired moisture level in the final corn bran product an exemplary method and system 200 for processing a plant fiber according to the present invention is described with respect to fig2 in the context of grinding corn bran fiber to produce a ground corn bran fiber product having a desired moisture level as shown in fig2 a stream of corn bran fiber 201 is delivered to a grinding apparatus 210 to reduce the size of the corn bran fiber to form a ground corn bran fiber stream 202 after grinding the corn bran fiber in mill 210 the ground corn bran fiber is transferred.