Electricity track panels explore lessons learned

By | November 03, 2010

The Southeast Biomass Conference & Trade Show electricity generation track touched on some of the biomass power industry’s most daunting challenges, hosting industry experts who divulged important lessons learned from a variety of projects.

The first panel addressed emission liabilities and current/pending obligations to control them. Panelist Larry Felix of the Gas Technology Institute discussed a hydrothermal biomass pretreatment (HPT) process that will reduce fossil carbon emissions when co-fired with coal. He described the process as essentially putting biomass into hot, compressed water to produce a carbonized residue. “It’s very similar in appearance to torrefied material, but there are some distinguishing characteristics that may make it into a much more advantageous fuel,” he said. “Our mass and energy balances suggest that process economics favor biomass HPT over torrefaction.”

Felix said a study GTI performed for the U.S. DOE several years ago determined that the most efficient way to reduce fossil carbon emissions was to mix biomass and coal. “With 10 percent biomass, you can reduce NOx (nitrous oxide) emissions up to 20 percent, and that’s the best you can do.”

GTI is in the process of designing a process department unit for the HPT technology, a facility that will be located near Birmingham, Ala.

 On the equipment side of emissions control, Charles Cary of Biomass Combustion Systems discussed a system the company is working on that it guarantees will meet the U.S. EPA’s Industrial Boiler Maximum Achievable Control Technology (IB MACT) proposed standards of 0.03 pounds of carbon per million Btu. “It’s basically a biomass combustion system that uses pyrolysized underfire air to gasify the wood, oxidizing the overfire air to complete the combustion process,” he said. “The hot gases are pulled through a boiler that produces either steam or hot water, and then goes through a particulate collection device before going out through the stack.”

The second breakout session under the electricity generation track was centered on implementing successful biomass energy projects.

Panelist Cap Kovarik of Abengoa Bioenergy discussed various successful renewable energy projects that Abengoa has developed over the years, including a biomass power plant in Spain that utilizes crushed olive dregs as a feedstock, a poultry litter-fired power plant in Scotland, and a 70-megawatt cogeneration power plant in Sao Paulo, Brazil, that runs on sugarcane bagasse to produce steam and power for ethanol production.

Kovarik emphasized the need to look to feedstocks indigenous or unique to the region, as well as ways to reduce costs when building plants, such as using modularization. “Have components built in a fabrication shop, and you’ll save a lot of cost,” he said.

Johnny Leggett, senior project manager at Hunt, Guillot & Associates, dispelled common myths in the biomass industry, the first being that biomass will become much cheaper than natural gas. “I can assure you we’ll have low natural gas prices for quite awhile, and those who think they’ll get into biomass because natural gas prices will spike up are probably not using a good strategy.”

Locating a plant next to a fuel and water supply, as well as a connection to the grid, is the most ideal scenario, Leggett said. “The best location would be on the river, with a bridge and a power line crossing it, because I hear people say they will use biomass within a certain radius of the plant and then they realize wood baskets are from river to river and bridges are spaced 35 or 50 miles apart. So they’ll have fuel on one side of the river that they can’t get to, so bridges are important.”

Leggett also urged his audience not to underestimate the amount of space needed for a biomass power facility. “It takes a lot of fuel to run a biomass boiler, one of the first lessons that I see that people learn is that they do not allocate adequate space for all of this fuel,” he said. “The fuel pile itself will be several acres, and you’re going to have a lot of trucks coming in from lots of different sources—it’s a lot of fuel.”

Flexibility in biomass use capabilities is also extremely important, according to Leggett. “In the Southeast, the primary fuel has historically been wood and byproducts from forest industry, but now we’re seeing that there are a lot of opportunity fuels such as chicken litter, corn stover and crop residue. These are fuels of opportunity that may not be available year round, where your trees from the forest will be, so it’s good to build some flexibility into your boiler from the beginning. The lesson learned here is that if you’re thinking of alternate fuels, you need to tell the designer of your plant all of the alternative fuels that may be available so he can do a cost benefit analysis for you.”

Fuel procurement is a full-time job, Leggett emphasized. “It isn’t a duty somebody does; it’s what they do full time. They’re dealing with a lot of different suppliers and it’s a day-to-day thing. Also, get used to short-term contracts. It contradicts everything you hear from financers they want those long-term contracts, but biomass is a spot market. The price will vary from region to region and from time to time, so it’s all based on availability.”