From tailings to biomass: crop trials assess use of tailings beds in biomass production.

• Author: Kelly, Lindsay
• Position: MINING

A long-term research project at Laurentian University is showing promise in using mine tailings to grow crops for biomass.

Over the last three to four years, Peter Beckett and Graeme Spiers, both associate professors at Laurentian University in Sudbury, have headed up the project, which examines the science behind using waste pulp and paper material, over top of mine tailings fields, to produce crops that could eventually be harvested and manufactured into biomass pellets.

"The whole idea, essentially, is, rather than just taking the tailings and wasteland at mine sites and putting grass down, to do something useful with them," said Beckett, who's also a founding member of Sudbury's VETAC (Vegetation Enhancement Technical Advisory Committee). "In this case, it's to try and see whether we could grow crops that one could make into energy fuels."

Researchers have partnered with Glencore and Vale in Sudbury and Goldcorp in Timmins, which have provided the tailings sites. Wood waste has been brought in from paper mills to top the tailings with organic material, and a local farmer has provided the agricultural equipment and expertise.

At the Vale site, paper mill sludge was brought in from Espanola and St. Marys (before that Sault Ste. Marie mill closed), while at the Goldcorp site in Timmins, paper sludge, which has extra nitrogen from producing fine paper, was brought in from Iroquois Falls.

At the Glencore site in Onaping, wood waste was brought in from various operations across Northern Ontario and mixed with municipal compost from Sudbury's landfill.

In all three cases, the organic material was diverted from landfills.

"In the long run, if it works, then you could go on taking extra waste and cover the whole of the tailings and really make them into productive areas, since there's something like 10,000 hectares of tailings in Northern Ontario," Beckett said.

In the experiments, between 25 centimetres and a metre of material is added on top of the tailings and then the crops are planted. Researchers have experimented with a number of crops, including corn, canola, switchgrass, sunflowers and willow.

The fast-growing hybrid willow grows between one and two metres a year, providing lots of fibre to harvest and make into pellets. Switchgrass, another fast-growing species, has also shown promise.

"We actually get pretty good biomass," Beckett said. "We get biomass on the sites which is roughly equal to what the farmers would get in their fields...