If it grows fast, Rich Roseberg likes it. If it sucks up sewage sludge, he wants it.
The Oregon State University soil scientist has a nursery full of sludge suck-ups at OSU's Southern Oregon Research and Extension Center at Medford.
Poplars are most popular. Kenaf is keen. Giant Chinese silver grass is a giant among grasses. But Roseberg's favorite is bamboo.
"Some bamboo species can grow 60 feet in 12 weeks," he noted. "They can take up a lot of water or, better yet, sludge."
Roseberg works closely with folks at the City of Medford sewage treatment plant, where sewage goes into the plant and stabilized sludge (biosolids) and treated effluent come out. Those folks want a good way to dispose of sludge and treated effluent.
Roseberg wants more. "Agriculture is limited by lack of water here and in most of the western United States," he said. "Sewage effluent could be a valuable irrigation water resource, not just a disposal problem."
And more. "Why not grow something of value with the effluent-like something for the huge fiber niche in this part of the country?" he said.
That's why bamboo piqued his interest. There is a strong market for bamboo shoots, fresh and frozen, especially among Asian populations. They wholesale for $2 a pound. In southern Oregon, you could grow a ton an acre-$4,000 worth.
There's also a market for bamboo poles for building construction, furniture, laminated flooring and decorative fencing. It might take seven to 15 years to get bamboo big enough for that market. In the meantime, the plant can perform a soil remediation service.
"As far as I'm concerned, what really counts is how much nitrogen and other sewage sludge components the bamboo will take up," Roseberg said. "We don't have all the numbers yet. But we'd estimate that a mature, 30-foot-tall growing clump would take up 10 gallons a day."
That would help Medford and sister cities a lot.
From April through October, the sewage treatment plant produces about 20 million gallons of effluent a day. In agricultural terms, that's 10,000 acre-feet-enough to supply 3,000 acres of crops like alfalfa, sweet corn and silage corn.
So far so good. After all, this is farming country. Presently, Medford's excess treated effluent goes into the Rogue River. "We have an excellent treatment plant, so the effluent is of very good quality," Roseberg said. But what happens as the city grows, sewage effluent increases, and farms make way for urban sprawl?
There is a bit of nitrogen and phosphorus in the effluent. While the amount is small by treated sewage standards, nitrogen and phosphorus can cause algae growth. Algae can reduce the oxygen in the water and stress the fish. Of more concern is the water temperature. Salmon need temperatures in the 50s to thrive. Sewage effluent could raise the temperature as high as the 70s, depending on the volume of discharge into a particular river.
"In the case of Medford, the temperature increase of the Rogue River due to effluent discharge is slight, less than a degree," Roseberg said. "But here the river flow is high and temperatures are cold due to the way Lost Creek Dam is built and operated. In general, however, effluent from treatment plants in Oregon and the rest of the West have a larger temperature impact due to usually smaller stream size and background temperatures that are fairly high to start with."
Larry Blanchard, water reclamation division construction manager for the City of Medford, said the city is in the process of renewing its sewage treatment permit with the Oregon Department of Environmental Quality. He said the city's collaborative effort with OSU will help ensure standards are met for permit renewal. Also, it will give the city a long-range plan to safely and effectively deal with effluent.
At this point City of Medford effluent increases Rogue River temperature in the summer by only three tenths of a degree Fahrenheit. "But DEQ might decide even that's too much," Blanchard said.
In the winter, effluent handling is no problem. Temperatures are cool and rains dilute the effluent. In the summer, Medford sludge is hauled to farm fields. We've done that for years with no effect on the soil but to increase its fertility," said Blanchard.
But times are changing. Medford is growing fast. DEQ is tightening restrictions. The city's project with Roseberg and OSU provides insurance for the long haul.
Right now the city-OSU project includes two acres. One acre is planted with poplars and the rest is split between giant Chinese silver grass (Miscanthus giganteus), kenaf and pasture grasses. OSU and the city monitor the site to see if the effluent has any negative effects on the soils. So far there are none.
The City of Medford is studying what properties are available to dispose of sludge and effluent from April through October. City officials estimate 2,000 to 3,000 acres are needed. The two-acre demonstration project will provide fiber crop data for the larger project.
City of Medford officials have an agreement with engineers at CH2M Hill, a consulting firm, to look at alternatives that would keep effluent discharge into rivers at a minimum. Roseberg has been meeting with both groups to discuss options for agricultural re-use of the effluent.
At Woodburn, Oregon, between Portland and Salem, CH2M Hill consulted on a project in which the company Ecolotree planted hybrid poplars at 18-inch spacing in rows 8 feet apart, then irrigated the trees with effluent.
"The narrow spacing made this a good disposal technique," Roseberg said. "But the end product would have to be pulp for paper, the lowest value of the various end products from poplar tree production." But some commercial lumber mills are using poplars to make paper, he noted.
At Medford, hybrid poplar trees were planted at 7 1/2 feet apart with 10 feet between rows. "My hypothesis is that within two to three years, as these trees grow, the effect of the wide-spaced trees will be just as great as with the narrow spacing at Woodburn," said Roseberg. "Also, the wide spacing should allow us to grow trees suited for lumber or even veneer," he added, pointing out that there is a strong demand for poplar veneer in Asian markets.
The hybrid poplars Roseberg is testing include several hybrid crosses between eastern cottonwood (Populus deltoides), and black cottonwood (Populus trichocarpa). These crosses can grow 60 feet tall in seven years.
Another crop that has both a market and good potential for taking up sewage effluent is kenaf (Hibiscus canabinus), an annual crop that can be used to make paper.
"In the South, kenaf grows fast-15 to 20 feet in one season," Roseberg said. We are at the northern limit of kenaf's growing range in Oregon. Still, plants near Medford grow 10 to 12 feet a year. At Corvallis, 200 miles north, they grew only 5 to 6 feet a year.
"Kenaf is an annual, which means it offers more flexibility for crop rotation than other crops we tested," he explained. "When it dies after frost it doesn't fall, so you can bide your time before harvest."
Kenaf is not a tree or a grass. "It's a member of the hibiscus family, related to cotton," Roseberg said. Its best fiber, called "bast," is produced in cells in the outer part of the stem, just below the bark. "This is long fiber used as far back as 4,000 B.C. in Africa and the Far East to make rope, sacks and matting," Roseberg said. "Today, bast has value to make newsprint, good quality office paper and a more natural source of carpet backing. It can also be mixed with other materials to make particleboard.
"Europeans are even using bast in automobiles as they try to increase the recyclable portion of cars," he added. "The fibers are used in place of plastic and vinyl in internal panels, roof linings, door panels and dashboards."
On the inside of kenaf are short, low-quality fibers that are very absorbent. These fibers can be used to make a low-quality paper, kitty litter or oil absorbents.
Roseberg said an advantage of kenaf is that it provides its own weed control and can be used to suppress weeds in other crops. "Kenaf in rotation helps break the weed cycle, especially in areas where you are growing a grass crop and want to control grassy weeds," he said.
Still another crop with possibilities is giant Chinese silver grass (Miscanthus giganteus), a warm-season, perennial grass.
"It grows well under hot, dry conditions," Roseberg said. "It is also cold tolerant, so it goes dormant in winter but comes back in spring. You can harvest it in fall, cutting it at 4 inches, and it still grows back."
Giganteus is used in Europe as a biomass crop, which means it is burned to generate electricity. In the United States, it is sold as an ornamental. It looks like pampasgrass.
"Its fiber quality isn't very high," Roseberg said, "but a market is being explored."
Roseberg said all of the "suck-up" crops he is testing-poplar trees, kenaf, Miscanthus giganteus and bamboo-can outperform agricultural row crops in their ability to take up effluent.
"Now we want to concentrate on making sure these crops can grow well around here and that we have a good market for them," he said. "Mainly, though, we want to document their water and nutrient uptake abilities, because little information is available on some of the crops."