Answer:

1. There are four types of fermentation: top, bottom, spontaneous and mixed fermentation. Top fermentation beer is made from yeast at relatively high temperature left to ferment for a short period of time. This is beer of the 'special', 'Trappist', 'stout' and 'ale' type. Bottom fermentation beer, on the other hand, ferments over a longer period at low temperature. Pils and Export type. As for spontaneous fermentation beer: these are beers that ferment without any added ingredient. They have a rather sour taste. This is imparted by the natural lactic and acetic acid fermentation process: 'Geuze', 'Lambiek', 'Faro'. Finally, mixed fermentation beers (the South Flanders red beers) are the result of a combination of top fermentation and bacterial flora that convert organic acids and higher alcohols into esters.
   
   
2. Bio-alcohol is alcohol produced on the basis of vegetable crops, such as sugar, maize, potatoes, sunflower, cereals, etc., as opposed to alcohol obtained from petroleum. Bio-alcohol is a renewable starting material, whereas synthetic alcohol is not renewable.

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