The STRAIGHT Poop

Fibrowatt plants are built in agricultural areas where water value is at a premium.

Early during the development of the Fibrominn Biomass Power Plant in Benson, Minnesota, Fibrowatt was considering the use of a wet cooling tower, which would have used treated effluent from the nearby Benson wastewater treatment plant and water from the water supply wells as cooling water. By using wastewater treatment effluent, Fibrowatt was making a strong commitment to the prudent use of local water resources.

As the design of the plant progressed, during near-drought conditions, questions were asked in the community about the plants impact to local water resources and whether water use could be reduced even further. After evaluating the situation further, Fibrowatt realized it would be able to cut water requirements further by converting to an air-cooled condenser (ACC) for cooling. An ACC is like a giant fan-cooled radiator. While an ACC typically is a little less efficient than a wet cooling tower, it does have a major benefit – no cooling water requirements. As a result of the change to an ACC, the Fibrominn plant cut its design water usage to about 15 – 20% of what originally would have been required for the plant.

With water usage cut so much, where is this water used?

Water is used in the boiler to make steam for generating electricity in a turbine generator. While some of this water is lost as “boiler blow-down”, most of the boiler water is continually cooled and recycled back through the boiler. As a result, the largest percentage of water usage (roughly 75%) is for the emissions control system. Water is used along with urea in the selective non-catalytic reduction (SNCR) equipment for nitrogen oxide reduction. Water is also used for the reduction of sulfur and chlorine emissions in the spray dryer absorber (SDA) in the lime slurry and for quenching the flue gas to help remove the collected sulfur and chlorine salts.

As Fibrowatt continues to improve its process design and performance, a lot of effort has been taken over the past few years to reduce air emissions through improvements to the design of the air emissions control system. Along with improvements to the air emissions control design is expected to come a significant reduction in water usage.

Like the local host communities for Fibrowatt plants, we value the local resources like water and work hard to meet local expectations for good resource management.

Fibrowatt assists area growers with poultry litter removal and then transports the poultry litter in tightly covered trucks on prearranged routes to the facility. The trucks then discharge the litter within a specially designed fuel storage building, which is kept at negative pressure to prevent the escape of odors. The litter is combusted at more than 1,500° F, ensuring the destruction of odor and pathogens. Water is heated in a boiler to produce high-pressure, high-temperature steam, which drives a turbine and generates electricity. The remaining ash by-product is beneficially used as a nutrient-rich fertilizer.

In addition to the experience gained from building and operating three poultry litter-fueled power plants in the United Kingdom, Fibrowatt successfully developed the first poultry litter-fueled power plant in the United States, sited in Benson, Minnesota. In 2007, the Fibrominn Biomass Power Plant began operation, helping meet the State of Minnesota’s commitment to biomass-generated renewable energy. Since the first UK plant began operation in 1992, the technology central to the success of these four plants has been steadily improved, demonstrating Fibrowatt’s long-term commitment to successfully converting poultry litter into electrical power.

A facility is permitted based on the maximum emissions from the facility – referred to as the maximum potential to emit (“PTE”). The PTE is established and based on the use of best available control technology (“BACT”) and is based on the assumption that the unit is operated 24 hours/day, 365 days/year.