Last week I traveled to Buena Vista—a small town about an hour southeast of Sacramento—to visit Buena Vista Biomass Power. This plant is an older lignite power plant that has recently been re-powered to combust biomass fuel. The plant is designed with a net output of 18.5 megawatts (MW) and is currently producing around 15 MW. The plant’s fuel supply manager John Romena is confident that the plant will be at full capacity this summer. The facility utilizes a bubbling fluidized bed (BFB) boiler that combusts biomass in a controlled manner, heats water to steam which then enters a turbine-generator to make electricity.  One advantage of BFB boilers is that it is possible to combust very low moisture content fuel compared to a traveling grate design.
As a third year chemical engineering student at UCSB seeing this plant in person was an eye-opening changeup to the hours I have spent in a classroom. I have done countless flowcharts and used them to calculate output temperatures and pressures, and various flow rates, but walking into the control room was unlike anything I have ever seen. Watching and learning from the supervisors illustrated just how complex this plant is.

As it was explained to me the stoichiometric amount of oxygen in the reactor must be carefully regulated, too much and the biofuel is not combusted fully, reducing the power output. However too little and a dangerous combination of explosive gases builds up and could potentially destroy the boiler. This among multitudes of other variables are shown and monitored on the various control screens.

Although not a particularly large plant, by comparison to coal or natural gas power plants, simply walking around instilled a sense of awe in me. The first thing we were shown was the unloading area, where full size trucks filled with literally tons of woodchips are picked up like Tonka trucks and dumped. Not knowing what to expect, this certainly showed what this plant was capable of.  After, we saw the piles upon piles of woodchips, which I guess could have covered a football field at least 20 feet deep, the necessary fuel for just 15 days of operation. This fuel requires very careful storage as the heat that builds up in the interior can, and often does cause fires.  Next was the cooling system that condenses the steam after it exits the turbine, while losing minimal moisture to atmospheric evaporation. Finally we saw the massive turbine and the generator, and ended in the control room.

What really impressed me about this process looking back was how clean it was. I didn’t think much of it at the time but there were no emissions to be seen. We have all had campfires (if not contact me and we will make one ASAP) and seen the amount of smoke produced by just a couple of logs. Here at this plant there was over a truckload (about 15 bone dry tons) of wood being burned every hour without anything resembling smoke being produced; it was truly an engineering masterpiece. I was on the fence about biofuels and their effect on the environment but this facility, which previously burned lignite, a dirty form of coal, now combusts green wood waste, agricultural residues and material from forest restoration projects. Without biomass power plants this material would either be landfilled or open-burned creating terrible pollution.

Further Information:
There are currently approximately 28 operational biomass power plants in California.  Our power plants page has a Google Map showing the location and operational status of facilities.  If you want to learn more about the process that is used to make electricity from biomass check out our factsheet.

Jack Hogan is a Chemical Engineering student at University of California Santa Barbara who is currently working for the Woody Biomass Utilization Group at UC Berkeley.