Bio-reactors could help reduce N runoff

This woodchip bio-reactor on a farm in Maryland USA, was visited by John and Catherine Ford.

Woodchip bio-reactors could be among the solutions for New Zealand farmers striving to reduce nitrogen runoff to waterways, say John and Catherine Ford, who have seen such a system in action.

“The most interesting research we saw in the United States that could have applications in New Zealand was the bio-reactors, by Dr Tom Fisher and Tim Rosen.

“Bio-reactors can reduce nitrates in water by as much as 90 per cent and phosphates 75 per cent,” says John, who with Catherine won the 2015 Gordon Stephenson Trophy and National Ballance Farm Environment Award.

The couple, who also won the Bay of Plenty Balance Farm Environment Awards supreme award that year, are drystock farmers on Highlands Station in the Lake Tarawera catchment, which has been farmed by the Ford family for 85 years.

As part of their national prize, the couple elected to undertake a three-week study tour to the US last year. “We wanted to see what McDonalds did with our bull beef, and what farmers were doing to improve water quality around Chesapeake Bay.”

Chesapeake Bay

The Fords wanted to visit Chesapeake Bay because they were aware of work to improve the bay’s water quality and believed some of what was being done could have relevance to New Zealand, and Rotorua’s lakes in particular.

Chesapeake Bay is about three-quarters of the area of New Zealand but has 18 million people, and is governed by six states; New York, Virginia, Maryland, Delaware, Pennsylvania, and West Virginia.

It was the Midshore River Keepers’ Conservancy group which installed the first wood chip bio-reactor in Maryland. Designed to intercept and treat groundwater, reducing the amount of nitrogen runoff to rivers, it involved digging a trench 100 foot long by 20-foot-wide and four feet deep, lined with a 20mm pond liner. A downstream box and an upstream outfall were installed.

Denitrifying bacteria

The system works by diverting water from the farm’s field tile and drainage system through the woodchip, which is host to denitrifying bacteria that live on the carbon in the wood. The bacteria consume the nitrogen in the water and release harmless nitrogen gas to the air. Scientists working on the scheme say it replicates a natural swamp or woodland system.

John and Catherine believe the system could be an effective and relatively low cost method for New Zealand farmers to reduce leaching of nitrogen into waterways.

Landowners in the US are encouraged to undertake environmental protection work by what the Fords describe as “absolutely huge levels” of subsidisation by the Government.

“Farmers’ attitude was to only do environmental work if it was subsidised. When we told them how much work New Zealand farmers did without subsidies they were impressed, but also thought we were absolutely crazy to do it without government assistance.

Heavy subsidies

“Farmers that had done some environmental work which they called Best Management Practices, such as cover crops, fencing streams, riparian planting, or bio reactors, did so with an agreed Farm Environment Plan with agency they were dealing with.  

“None of these plans were imposed on landowners, they were all agreed to between farmer and agency, and as a result both parties showed a strong commitment to the plan.

“This was an important difference between our situation in New Zealand where the imposition of rules is prompting some landowners into confrontation with councils rather than the genuine collaboration we saw in the US.

“Of course, the subsidies help immensely with the attitude difference. But it also reflects the key difference in our societies where the US value personal freedom above fairness and NZ the reverse.”

John and Catherine also say that compared to New Zealand, the US has an extremely complicated political system with the extra levels of government, from local, county, state, and federal political bodies, plus non-government organisations.

“This level of complication and the sheer size of these organisations will make any change to their agricultural, environmental, and subsidy policies very slow.”

The couple did also get to see what happens to the meat they produce, which is exported to the US.

One billion patties a year

“We went to the McDonalds plant in Fresno, which was built adjoining a beef plant owned by Cargill Ltd.   “The McDonalds plant processes 160 ton of meat into hamburger patties each day, which equates to about one billion patties a year. Thirty per cent of the meat used is frozen ‘95 per cent lean’ meat imported from New Zealand and Australia,” says Catherine.

“We saw cartons of Riverlands and Silver Fern Farm meat being used while we were there. Our frozen meat is blended with the higher fat percentage meat sourced from the adjoining Cargill plant to make the ‘perfect’ McDonalds meat patty.”

John and Catherine’s full report of their visit to the US is available at: