Schools use fish waste to help grow plants

Programs at Poly, elsewhere provide hands-on science lessons

n a science classroom the size of a commercial garage, high school students are clipping back the wild, lush plants growing out of a tank of water. Their harvest is delicious: peppery greens, spicy watercress and robust lettuce.

All of this bounty comes from small pots of soil suspended on plastic foam in a tank of water that is rich with fish feces. For the students at Baltimore Polytechnic Institute, the classroom’s aquaponic laboratory has been a chance to combine the study of environmental science with a smattering of chemistry, biology and engineering.

Poly’s program is similar to those in 23 schools in 14 counties in Maryland. Most schools have aquaculture programs and only grow fish in large tanks, but a few schools are taking the process one step further by immersing students in aquaponics — in this case engineering systems that use nitrogen-rich fish feces to grow plants.

The first aquaculture program was started about 20 years ago at South Carroll High School in Carroll County through a partnership with Maryland Sea Grant, a program which promotes environmental science education. The aquaculture laboratories have since spread through the state,

Ieach adapted to suit the needs of individual schools. Students at many schools are growing striped bass and perch, two species found in the brackish Chesapeake Bay. At Poly, the students are growing tilapia, a freshwater species, that allows them to also use fresh water to grow their vegetables. Seniors in an environmental science class have become fascinated by aquaponics as a sustainable agricultural practice.

The class is learning “a better way to feed everyone in the world,” said Franklin Portillo, 17, who is so interested in the process that he stays after school to help keep the system running properly. He and several other students said they are now considering majoring in science in college.

“You can produce a lot of food in a small space,” said Xander Easton, 17. “This is an example of one of those potential agricultural solutions for world hunger.”

The plants are growing quickly under LED grow lights and in the nitrogen-rich water circulated in the tanks. The greens they can’t give away are being recycled into compost.

William Wolfe, who heads the school’s engineering department, and Jeff Reeser, a biology teacher, started the program several years ago with 200 students whom they challenged to design and build a closedloop system that grows fish in four tanks, each the size of a single bed. The water from those tanks then flows into several other tanks growing plants and using the fish feces as fertilizer.

There were many failures along the way. Pipes burst. Roots grew into pipes and backed up the system. Water tanks overflowed in classrooms and seeped into the school’s hallway. Their first plants died because they experimented with putting the plants in the same tank as the fish.

Wolfe and Reese now laugh about the classroom disasters. They could have built the system with student help in three to six weeks, but they wanted the students to do it on their own, using their knowledge of engineering, chemistry and biology, and to figure out the process through trial and error.

They knew the students would learn as much from their failures as from their successes. It was worth the six-month wait for students to design a system that works.

The aquaculture program at South Carroll High School was established by a teacher and Adam Frederick, assistant director for education at Maryland Sea Grant, which is part of the University System of Maryland and a network of organizations working to preserve and restore the Chesapeake Bay and other state coastal waters.

Frederick said aquaculture labs need continuous monitoring of the water quality to help identify signs that the system is in danger. In university research laboratories, this monitoring is done with expensive equipment that most schools can’t afford.

So Poly’s teachers turned to Harry Berman, a retired NASA employee with a specialty in systems engineering, for help finding a solution. Berman said he was bored in retirement and found Poly a fun place to volunteer. He came up with a U-shaped computer work station that uses old Dell computers and routine equipment to help monitor the system. Students can now look at the monitors to check for problems.

Frederick said the system “solved a stumbling block for us” and has been picked up by many other schools.

Another flaw in the student system, they said, is that it needs a different fish food. The fish in their tanks are now fed ground-up fish, which is not a sustainable model.

“It is bad that we are feeding them fish right now because tilapia are vegetarian,” Portillo said.

Several top Poly students spent two summers interning at a Johns Hopkins University laboratory trying to find the right algae to feed tilapia. They finally came up with one, but that algae species would need a much larger space to grow than is available at Poly. For now they are trying to grow duckweed, which they hope will satisfy their fish.

Poly is one of two schools in the city with the aquaculture program. Green Street Academy also has a laboratory for middle school students. Carroll County Public Schools has made the largest commitment and now sustains an aquaculture laboratory in every high school.

James Peters, who is in charge of secondary science throughout Carroll County, said a research class offered in high school has made it easy for many students to get involved in aquaculture.

“It is student-based research. Kids carry out an investigation with an aquaculture and environmental theme,” Peters said. “From beginning to end they conduct that research. … They learn all the skills for research. How to present and defend it. What response are they going to have if it fails.”

Failure is viewed as a chance to teach students how to persevere.

“It is enjoyable to watch,” Peters said. “You can see the growth in their education.”

Carroll County teacher Judy Plaskowitz said the aquaculture program has been valuable for all students, not just top science students. Even students with limited math skills can learn how to take samples and measure dissolved oxygen in the water, she said.

“They are working with plants. They are working with fish,” she said. “They feel they have something they are responsible for when they come to my classroom. It has a broad appeal.”