moving it to the solids concentration module 138 helps retain this level of nitrogen during the evaporation process without acidulation of the digestate 116 the evaporation process would result in further lowering the nitrogen content of the liquid digestate due to high ph and higher temperatures which would both enhance the volatilization and loss of ammonia gas in certain embodiments the evaporation step increases the total solid content of the digestate from about 5 to produce a concentrated digestate 140 having about 10 20 total solids by weight and more preferably about 14 20 total solids by weight the concentrated digestate 140 is sent to a high temperature spray dryer module 170 for the next step in the drying process as noted above it will be recognized that in certain embodiments the concentration step can be omitted and the process can proceed as otherwise described below but without concentration of the solids in the digestate optionally prior to entering the evaporation module 138 the ph adjusted digestate 136 is screened utilizing a filter 144 such as screens sieves or other mechanical filtration elements to remove large particles and fibers from the digestate in preferred embodiments the filtration media consists of a plurality of screens ranging from about 100 micron to about 300 micron in a preferred embodiment the filtration element is a 3 d screen of the type capable of removing elongated fibers or materials from the digestate solids fibers 146 removed from the digestate by the filter 144 may be collected and may be blended with the dry fertilizer product to enhance soil recovery in certain embodiments the solids concentration or evaporation module 138 includes a falling film evaporator and in preferred embodiments employs a multi.