Media Statement
2 August 1999
HUMAN WASTE MAY BOOST FOREST PRODUCTION
Scientists at Rotorua and Christchurch are looking at how human waste can be spread in plantations as a means of
disposal and as a way of boosting forest production.
"Forested land treatment systems for wastewater have been in New Zealand for more than 10 years," programme leader Mark
Tomer of Forest Research says. "But there are no design or management criteria that enable these systems to be run
sustainably.
"Biosolids applications are being looked at increasingly, because, as improved wastewater treatment technologies
generate more and more sludge, options to sustainably recycle these wastes onto land rather than into water or landfills
must be developed."
Dr Tomer's project, jointly conducted by researchers of Forest Research, Landcare Research, and National Institute of
Water and Atmospheric Research, is supported by the Public Good Science Fund.
Dr Tomer says plantations will probably be preferred because of environmental benefits, nutrient recycling, and less
risk to public health and land amenity values.
"So it's critical that design and operation criteria for land treatment systems be developed based on a scientific
understanding of the fate and effects of these waste materials in the forest ecosystem."
He says the programme has four goals. Three are based on field research in Rotorua's land treatment system for
wastewater in Whakarewarewa Forest. The biggest aims at discovering where wastewater goes and how far, in a small-plot
experiment.
"Thirty-six plots, each five by five metres, have been constructed. Fifteen of these plots are filled with dune sand to
allow an on-site comparison between two soils, sand and the native volcanic soil.
"The results will allow us to determine how effluent treatment and application rate affect the trees, the soils, and
soil leaching, so that we can make specific recommendations on designing and managing land treatment systems."
The second goal, pursued with NIWA scientists, aims at seeing how effluents pass through and affect wetlands.
"This work will help determine how wetlands might best be designed and used to act as a backup system for nitrogen
removal for land treatment systems."
Dr Tomer says the third goal at Rotorua is to work out how forest plantations can be managed to make the most of
nutrient removal and forest production.
The last objective aims at developing sustainable management practices for applying municipal biosolids onto forest
land.
"This is centred at Christchurch. This work is being done in collaboration with Landcare scientists. Effects of biosolid
applications on tree growth and nutrition, and on the chemistry of soil leachates, are being determined. Studies are
being initiated using two long-term field trials, with applications being carried out every three years at two rates of
application."
Further information:
Dr. Mark Tomer, Forest Research, Rotorua. Ph: (07) 347 5899, Fax: (07) 347 9380. Email: mark.tomer@forestresearch.co.nz
Patricia Donovan, Ph: (04)498 7809 Mobile 025 226 4136