‘Pure’ methane from crops

Press, 12 January 1977, Page 3

‘Pure’ methane from crops

PA Dunedin An Invermay scientist has succeeded in producing almost pure methane gas by bacterial action on farm crops. The scientist, Dr D. J. Stewart, has obtained a gas 96 per cent pure by adding a solution of 10 parts per million of nickel or cadmium ions to a fermenting mixture of farm crops. Invermav is an agricultural research station near Dunedin. In the last few years, a great deal of work has been done in producing methane “bio-gas” from farm crops, but until Dr Stewart’s experiment the maximum purity normally obtainable had been only about 70 per cent. The gas then requires further purification at added cost. Dr Stewart has completed an economic study to be presented to the third New Zealand Energy Conference in May this year. He estimates that production of bio-gas using the technique he has developed will cost $5 for every million British thermal units (8.T.U.) produced. “This is pretty expensive when compared with the present cost of natural gas,” he said. “But it compares favourably for example with the cost of producing gas

| from coal at the Dunedin gas-i works — $7.90 per million B.T.U. The cost of producing; methane from farm crops also compared favourably! with the present price of | petrol in energy terms — $8 per million B.T.U. Dr Stewart considers it possible that methane from farm crops may become an important commercial fuel, especially when natural gas supplies run out. Dr Stewart's experiments I follow research in the United | States where it was found i that almost pure methane! was produced in research with water weeds. Water: weeds had been used in an i attempt to remove cadmium, nickel, and phenols pollutants! in water. The methane was) produced as an unexpected side effect. Dr Stewart is apparently the first scientist to try the method on fermenting mixtures of farm crops, such as hay, maize, and barley. He is not sure how the metal ions function, but they appear to stop the action of some bacteria-producing impurities and do not affect the action of the methaneproducing bacteria. He plans to have a pilot plant in use at Invermay next year, supplying methane for heating and bunsen burners in the laboratories.