Alco Energy Rotterdam / Bio-refinery

Our bio-refinery processes all our raw material being feed corn in a number of added value products:


Biorefinery - upper


The Alco Energy Rotterdam production process uses corn as raw material. The process uses the starch that is available in the grains, but does not touch the protein rich parts of the grain, which is used as a nutrient of animal feed stock.

 Biorefinery - lower


As starch cannot ferment directly, preparatory steps are required. Corn, for example, is first ground into a coarse powder or flour in a hammer mill or roller mill, and then fed into a mashing system, where it is mixed with water. It then passes through a cooker, where the steam breaks down the starch granules and sterilizes the mash. By the addition of an alpha amylase enzyme, the mash liquefied by breaking down the starch into dextrins. The mash is then cooled and pumped to a fermentor where simultaneous saccharification and fermentation is taking place. This involves the addition of a second enzyme (gluco-amylase) and yeast. During  fermentation, yeast transforms sugars into ethanol and CO2.


The fermentation process is very sensitive to temperature and acidity, which must be controlled very closely. The industrial fermentation at Alco Energy Rotterdam is a batch process, meaning that the entire process is completed in each individual tank of the batch. The cycle will last from 50 to 60 hours at a temperature of 30 to 32 °C, and the resulting product,  called ‘beer’,  has a strength of 16-18 % alcohol by volume


The subsequent distillation process takes place in a distillation column and is used to concentrate and purify the alcohol stream. It is a continuous distillation process. A distillation column brings the ascending vapour and descending beer liquid into contact using disks and donuts. This process leads to a mass transfer. The alcohol vapour is concentrated in the top of the column, while the original liquid stripped of alcohol is discarded as whole stillage at the bottom of the column. During distillation,  impurities such as  ‘heads’ (esters, aldehydes and so forth) and ‘tails’ (such as higher alcohols or fusel oils) are removed. Distillation will produce a raw alcohol of 95 or 96% strength by volume.


The last phase in the process is dehydration where the remaining water is removed to produce ethanol containing less than 0,3 % water — ‘absolute’ or ‘anhydrous’ alcohol. This degree of concentration cannot be achieved through distillation. At Alco Energy Rotterdam, this dehydration process happens through molecular sieves, where alcohol passes through sieves that retain the water molecules.


The whole stillage (beer stripped of alcohol) is further processed in different steps to animal feed. This involves a centrifugation step, separating the fiber fraction (wet distillers’ grains) from the clarified liquid (thin stillage). Thin stillage is evaporated to a syrup (condensed distillers’ solubles). Wet distillers’ grains and condensed distillers’ solubles are then mixed and dried to form DDGS (Dried Distillers’ Grains and Solubles).