Studies on the effect of storage of beet (Beta vulgaris) for ethanol production

Abstract

High oil prices in the 1970's stimulated interest in production of fuel ethanol from beet and since by extending storage of beet, expenditure on ethanol plants could be reduced. Trials were undertaken to determine storage losses and effects on fermentation of extracts. Investigations involved three years of clamp trials and two laboratory experiments using machine and hand harvested beets in open meshed (onion) bags placed inside clamps. Sucrose and invert sugars were determined using HPLC and ethanol with GLC.

Rot increased with length of storage. Thiabendazole reduced rotting more than procymidone, iprodione and vinclozolin. Benomyl + iprodione, thiabendazole + procymidone and thiabendazole showed similar results. Anti-dessicants with thiabendazole were most effective. Increased temperatures increased rotting and sugar loss. Beet overwintered in the ground did not rot and had similar sucrose levels to 10° storage. The predominant pathogens were Botlylis cinerea, Fusarium avenaceum, F. culmorum, F. sambucinim, Phacidiopycnis tuberivora, Pizoma betae and Penicillium spp.

Sucrose and total sugars decreased during storage. Thiabendazole reduced sugar loss compared to controls in two out of three years and slowed the rate of invert sugar formation. Frost damage and high temperature increased invert sugars and storage loss. Weight and sugar losses were similar to those reported from Europe.

Ethanol produced from extracts of beet incubated with Saccharomyces cerevisiae at 30° showed fungicides and anti-dessicants had no effect on fermentation rate or efficiency. Specific fermentation rates were higher for sugar than fodder beet. Fermentation efficiencies were between 70% to 84%.