For the past two years, SERC has been investigating biomass gasification for the Indonesian Sugar Group. Bagasse, a fibrous sugar cane waste product, is burned inefficiently in boilers at the Sugar Group factory. An alternative is gasification, a process of partially oxidizing biomass to produce combustible gases that can be burned cleanly and efficiently in a turbine to produce electricity. We are testing the feasibility of gasifying bagasse in a small-scale gasifier at SERC and investigating the economics of larger gasifiers that could be used by the Sugar Group.
SERC’s gasifier is designed for wood, so we used Douglas Fir and Tan Oak wood chips for our first twelve gasification trials. We used these trials to become comfortable operating the gasifier and to investigate the effects of fuel moisture content on the gasification process. We found that moist wood is consumed more slowly, producing lower concentrations of combustible gases than dry wood. Lower fuel consumption tends to offset lower power output so that overall efficiency does not change significantly with fuel moisture content.
After completing our wood-fueled trials, we moved on to bagasse. As Joe Purdon explained in our spring 2009 newsletter, bagasse was transported from Texas and sun-dried at SERC. We shipped sun-dried bagasse to Biomass Briquette Systems in City of Industry, California, to produce bagasse briquettes. We tested these briquettes in SERC’s gasifier, and we discovered that bagasse briquettes gasify differently than wood chips. Briquettes tend to expand inside the gasifier, forming a solid shelf that obstructs fuel flow. We used smaller briquettes in our second and third trials, and we achieved gasification for about one hour before the shelf was formed. We are now looking for new ways to gasify bagasse briquettes, and we also plan to gasify loose bagasse. We’ll keep you apprised of these efforts in a future issue of our newsletter.