System study - Techno/economical reviews of a number of process combinations of ethanol processes and other relevant industrial processes

摘要

The present study has been commissioned by NUTEK. Its aim is to investigate whether there are any possibilities to lower the cost of ethanol production from wood based materials and to what extent co-location of an ethanol plant with other types of plants would aid in this respect. The studied processes are CASH and an enzymatic process. CASH uses acid at high temperature and the enzymatic process uses enzymes for the saccharification of wood. The enzymatic process converts a larger part of the cellulose than the CASH process and thus produces about 50% more ethanol from the same amount of raw material. The yield is however low and even the enzymatic process converts less than 25% of the wood to ethanol. Apart from the ethanol, residues are also produced. These are more than 50% of the raw material or twice as much as the ethanol produced. With a large scale production of ethanol, the market for the by-products would become a critical factor. The proposed process designs have not been tried in mill scale in either case. Especially for the enzymatic process, basic data on which the industrial design of the process could be based are not yet available. The possibility of economical enzyme production e.g. is to our understanding still not shown. For the CASH process the situation is somewhat further advanced but there remain several questions regarding the hydrolysis step. If the enzyme method works as assumed this process has a very important advantage, the higher yield. This results in a lower ethanol production cost and also in less by-product fuel. In all cases the enzymatic process appears to give at least 0.5 SEK/l lower cost than the CASH process. Our conclusion is therefore that the opportunities for synergy effects should be utilised and that the effort should be directed towards continuing the developing of the enzymatic process towards a commercial industrial process