Rice-Fueled Plant Is Cooking Up a New Way to Produce Electricity
The little factory south of town that converts rice wastes to electricity is a sweet deal for everyone.
It relieves 21 rice mills of the expensive landfill disposal of rice hulls, and spares residents of the Sacramento Valley from the noxious smoke of rice straw burning in the fields.
The Pacific Gas & Electric Co. gets power without the financial and environmental encumbrances. Electricity users may turn on their toasters without visions of oil sheiks or leaking tankers.
Even the makers of concrete, ceramics, glass and computer chips welcome the burning rice’s ash, which is also used to oxidize and solidify toxic waste spills.
Rob Colman, president of Oxford Energy Co., owners of the factory, says electricity produced by his plant will bring in $15 million to $28 million a year at a fuel cost of $3 million to $6.5 million. After paying 33 permanent employees and other expenses, he projects operating income at $6 million to $16 million a year.
Favorable Financing
If that isn’t sweet enough, Colman says Oxford has little of its own money at risk in the $60-million total investment, while keeping majority control. The big money comes from bank and similar financing.
The Floyd Myers Marsh Power Plant, the largest of its kind in the world, has just gone on line to convert about 200,000 tons of rice hulls and straw a year to 29 megawatts of electricity, enough for 35,000 homes. The plant is about 90 air miles northeast of San Francisco.
PG&E; is required by the federal Public Utility Regulatory Policies Act of 1987 to buy power from small producers at “avoided cost”--meaning what it would cost to produce the power itself or buy it elsewhere.
The law has given rise to nearly 900 small electricity producers in PG&E; territory alone, using cogeneration, solid waste, geothermal, solar, hydro and wind sources, all with a total capacity of nearly 10 million kilowatts. And they are still coming, despite the petering out of governmental incentives.
Sighted From Interstate
At first sight from Interstate 5, the plant looms from behind massive embankments of rice hulls covered with black plastic and old tires. Start-up engineer Thomas Stinson says there is little fire danger. Rice hulls by themselves hardly burn.
But when ground into a fine powder and blown through nozzles, the hulls explode into an orange inferno at about 1,600 degrees Fahrenheit.
The rice hulls burned are about two-thirds of the total in one of the world’s richest rice-growing regions. But the straw consumption makes only a small dent. Stinson says the straw content of the fuel now being used is only about one-eighth, being increased gradually to an expected one-third next year.
The performance of the straw as fuel is being monitored under a state research contract. Straw alone has never been used for a power plant. But the potential is huge. Stinson said there’s enough straw available to justify another 40-megawatt plant burning straw alone.
Hulls deliver about 6,000 British thermal units per pound, compared to 4,500 for green wood and 10,000 for coal.
The season for amassing a year’s supply of straw is short and irregular, depending on weather. Also, some growers still think burning the rice stubble is the only way to rid the fields of diseases. They ignore the researchers who say bailing and chemical treatment are better. So it is hard to get them to mow the stalks close to the ground and bail the straw during harvest.
The fuel arrives on bulky double-trailer trucks and is routed through grinder, silos, burners and--as fly ash--the bag house. In the control room, before three color display screens, operators can call on data from 1,100 sensors throughout the plant.
The steam arrives as well water and goes through 23 separate systems before blasting into the split-cycle turbine. Most of the systems are to rid it of chemicals that would cake up the tubes--like the bottom of a teapot. No water leaves the property, except little wisps of steam connected to control and safety devices.
The plant is custom-built. Colman says it should keep humming 20 or 30 years, with the final product going out on three wires slung on a single line of wood poles, and the checks coming in the mail.
