Complex sentence: In June 2006, a U.S. Senate hearing was told the current cost of producing cellulosic ethanol is US $2.25 per US gallon (US $0.59/litre), primarily due to the current poor conversion efficiency.
Split into simpler sentences: In June 2006, a U.S. Senate hearing was told that the current cost of producing cellulosic ethanol is US $2.25 per US gallon (US $0.59/litre). This is primarily due to the current poor conversion efficiency.