Like most modern ethanol plants, all POET plants are powered by natural gas. But for one, that may no longer be the case.
Ethanol itself might be the headlinegrabbing aspect of the biorefining business, but for POET Biorefining – Chancellor, S.D., a series of new projects are quietly helping to reduce the facility’s non-renewable energy needs.
As part of an expansion to increase production from 45 million gallons to 100 million gallons per year, the five-year-old Chancellor plant is embarking on a landfillmethane capture system and solid waste fuel boiler project to burn waste wood. Together, they will greatly offset its natural gas consumption.
When the two projects are completed later this year, the expanded plant will operate at a higher level and produce ethanol at a reduced cost, all while using less natural gas.
The first part of the plant’s improved energy equation is the construction of a solid waste fuel boiler that consumes wood waste to produce steam energy used in the distillation process and for the other general energy needs. This system will help offset, and potentially in time nearly eliminate, the plant’s consumption of natural gas.
“What we are doing is burning a renewable fuel to produce a renewable fuel,” says Rick Serie, General Manager for POET Biorefining – Chancellor.
Increasing the use of renewable fuels will also save the plant money. While the actual future cost savings are ultimately linked to the price of the natural gas offset by construction of the boiler, one of the development criteria for the project was that the boiler be financially feasible. After researching several potential fuel sources, POET found that a biomass fuel stream made the most sense from a cost standpoint.
“This is proven technology in other industries, and has a proven payback,” says Jim Geraets, Alternative Energy Engineer for POET.
Key to this project is an agreement between POET and Mueller Pallets, a regional pallet company based in Sioux Falls, S.D. Mueller Pallets takes in shipping pallets from the surrounding area, inspects and repairs the pallets, then grinds waste wood for a variety of purposes.
“[POET] will be taking as much as 350 tons of wood a day, five days a week,” says Henry Mueller, Coowner of Mueller Pallets. “That’s about 17 semi-trailer loads a day—two football fields covered 220 feet deep with raw materials per year.”
Mueller Pallets has expanded its business to meet the needs of the POET Chancellor plant. In addition to pallet recycling, the company will begin accepting wood from other sources to help meet contract obligations. The company is now able to grind wood from the construction industry, as well as wood that would otherwise end up as landfill at several area dumps. The plant will require mostly dry wood, such as kiln-dried lumber and pallet waste, to burn efficiently. But it will also be able to burn a percentage of so-called “wet wood” from shredded trees and downed branches.
“We’ve contracted with local landfills. They get a lot of trees, and they’re jumping on the bandwagon,” says Margie Mueller, Co-owner of Mueller Pallets.
Adds Henry Mueller, “We’re working with the garbage haulers, and the landfills still get their tipping fees and keep the wood above ground for us to grind so that it doesn’t get buried or burned.”
The second major alternative energy project being developed at POET Biorefining – Chancellor is a system to burn landfill methane gas supplied to the plant by the Sioux Falls Regional Landfill, located 10 miles north of the plant. In 2006, working with a grant from the South Dakota Board of Water and Natural Resources, the Sioux Falls Regional Landfill commissioned a report that recommended a partnership with the Chancellor plant as the best available option to utilize the landfill gas. The state sees many benefits to this partnership.
“Utilizing the gas at the ethanol plant is a form of recycling or reuse,” says Kim Smith, Information Specialist for the South Dakota Department of Environment and Natural Resources. “Collecting the landfill gas for reuse prevents greenhouse gasses from entering the atmosphere. Utilizing the landfill gas reduces the ethanol plant’s reliance on natural gas or other fuel sources, which also has far-reaching energy consumption benefits.”
The landfill takes up 710 acres and serves the five-county region around Sioux Falls. Landfill gas (LFG) is created through the decomposition of solid waste. LFG consists of about 50 percent methane, the primary component of natural gas, about 50 percent carbon dioxide, and a small amount of nonmethane organic compounds. The LFG is collected by a series of wells that extract both the LFG and liquids (leachate) that leach from the buried trash. The LFG and leachate are separated, and the LFG is currently burned off in a flare to destroy the methane, which is a potent greenhouse gas. As the project advances, the landfill will compress the LFG and send it through a lowpressure pipeline from the landfill to the POET plant where it will be used to offset natural gas usage.
“It is a reliable and renewable energy resource,” says Mark Cotter, Director of Public Works for the City of Sioux Falls. “The nice thing about working with the POET Chancellor plant is that they run 24 hours a day and they can take all we can produce.”
When the pipeline is completed and the POET Chancellor plant is operating using the gas in conjunction with its solid waste fuel boiler, both the plant and the city will benefit.
“There is a capital expense for the city and POET with this partnership, but the offsetting benefits are POET reduces its dependence on fossil fuels and the city gains a new revenue stream to offset future operational increases,” says Cotter.
Initially, the boiler and the landfill gas will be used only to provide steam heat for the front end of the ethanol production process. This steam will be used in the actual evaporation and distillation process and to provide for the plant’s other steam energy needs. While this step will eliminate up to 60 percent of the expanded plant’s natural gas consumption, some natural gas will still be used on the back end of the production process for driers that process POET’s Dakota Gold distillers grain products. As the partnership with the Sioux Falls Regional Landfill advances, and as the landfill gas technology is proven, even this natural gas usage can be offset.
“In theory, we could get up to 90 percent replacement of the natural gas usage over time, as landfill gas supply increases,” says Geraets.
There are numerous environmental benefits involved with both the solid waste fuel boiler and landfill methane projects, but controlling the plant’s emissions is also a critical part of the project. The boiler at POET Chancellor will only burn certain kinds of permitted materials. It will be equipped with advanced pollution control and monitoring equipment, and a dry absorbent material known as trona will be introduced into the flue gas to further sequester emissions.
“We’re doing what we can to make the process more efficient,” says Geraets. “We’re [even] paving traffic lanes to keep dust from truck traffic down.”
There are many upfront advantages to using waste wood and landfill gas as fuel sources, but the potential benefits to both POET and the environment extend through to the combustion byproducts. Even the leftover fly ash created by the boiler will find a productive use.
“That can be land-applied as fertilizer or used in concrete,” says Geraets. “It gives you another product from our refinery that we didn’t have before, adding to our diversity.”
In many ways, these improvements at the POET Chancellor facility will serve as a test of the systems and advance the business of ethanol production.
“There are many things that we are validating through this project,” says Geraets. “We’ll be validating the whole system in terms of emission controls, burning this particular fuel and in the material handling side. I do foresee this rolling out to other plants.”