DEMONSTRATION FACILITY INDUSTRY NEWS


producing carbon dioxide. Part of ZeaChem’s intellectual property is the care and feeding of bugs such as Moorella. “We create the right environment for the bugs to multiply and do their work,” explained Eggeman. “The speed at which they do this is incredible.”


The ZeaChem process ZeaChem’s patented process converts biomass into concentrated acids, esters and alcohols. At the Boardman, Oregon, demonstration facility, the process starts with wood chips from poplar trees, a fast- growing fibre source in the Pacific North-West, which rivals the speed of eucalyptus. The front-end is mostly supplied by Andritz. “Many traditional pretreatment methods are not effective when applied to feedstocks with high lignin content, such as forest biomass,” said Turner. “This is where Andritz has an advantage.” Pretreatment combines mechanical, thermal and chemical actions. On the mechanical side, the goal is to achieve uniform size reduction of the biomass. The chemical side


removes barriers in the biomass so that ZeaChem’s bacteria and other micro-organisms can work their magic during fermentation. Key Andritz equipment includes a live-bottom presteaming bin, a lock hopper, a steam mixing screw – and then the heart of the process, the horizontal pretreatment reactor. The reactor uses Andritz’s advanced dilute acid steam explosion (SteamEx) technology – a two-stage process to heat the biomass, add dilute acid and then rapidly release pressure. This causes the water inside the biomass to ‘explode’ the fibres, converting them to very small particles.


The softened cellulose and lignin is ‘refined’ in an Andritz disc mill and the sugar streams from the wood are filtered in an Andritz filter press before being sent to ZeaChem’s fermentation process. The filtered cellulose can be sent through the process again to extract the remaining sugars or it can be sent to ZeaChem bioreactors for enzymatic saccharification before entering the fermentation process.


Micro-organisms convert the sugars into organic acids (when


Brian O’Neill with the ‘Seed Tank 0’ vessel where the first 2 ml of Moorella is placed to start the fermentation process.


using bacteria) or ethanol (when using yeast) during fermentation. In the case of Morella, as little as 2 ml of the bacteria starts the


process. From this small ‘seed,’ fermentation is scaled up in a series of tanks, ultimately into three 40,000 gallon (150 cu m)


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