Coal, wood and charcoal gasifiers have been used for operation of internal combustion engines in various applications since the beginning of this century. The utilization peaked during the Second World War when almost a million gasifiers were used all over the world, mainly vehicles operating on domestic solid fuels instead of gasoline.
It is important to keep in mind that small gasifiers have been used quite extensively in the past and that they have played a very important part in reducing or eliminating the need for fuel imports in some countries. There is no need, however, in this publication to go deeper into the history of the development of small gasifier technology. Those who are interested in the subject are advised to study the reviews made by the Swedish Academy of Engineering Sciences (43) Kaupp and Goss (20) Skov (36) Bailey (3) Earthscan (12) or the National Academy of Sciences in U.S.A. (32).
Interest in the technology of gasification has shown a number of ups and downs over the last eighty years, as is strikingly illustrated in Fig. 1.1 which reproduces a histogram that plots the number of wood gasification reports referred to in "Chemical Abstracts" since the year 1900.
It appears that interest in gasification research correlates closely with the relative cost and availability of liquid and gaseous fossil fuels. The histogram shows that the number of articles was at an all-time peak in 1979, following a period of low activity in the 1950's and 1960's.
There is an important difference between the earlier periods of high interest and the present situation, however. Earlier, the increase in scientific activity corresponded to an increased number of gasifiers in practical use. The recent increase in scientific interest has not yet resulted in much practical and commercial activity. The reason will be discussed in the last chapter of this publication.