BANGOR – Conservation, not alternative energy sources, will keep the environment stable, a retired University of Maine professor said Thursday.

“The idea that the wind and the sun is going to make the future like the past is just plain wrong,” said Richard Hill, professor emeritus of the UM mechanical engineering department and a former consultant to the U.S. Department of Energy. “When you see the standard of living, we’re way up there [above other countries] in energy consumption. And that’s irresponsible. The thing to do is to, for crying out loud, reduce the energy consumption.”

Hill was the guest speaker at a Husson College Business Breakfast, which drew an audience of 114 city leaders and representatives from local businesses.

The present amount of carbon dioxide in the atmosphere has not yet become a threat to humans, and the cost of processes to reduce existing carbon levels significantly is prohibitive, Hill said.

Hill rejected biofuels as an efficient source of alternative energy.

To keep carbon dioxide levels from rising, U.S. residents in particular should significantly reduce their energy consumption, Hill said. Human activity continues to add carbon dioxide to the atmosphere in alarming quantities, primarily through combustion of fossil fuels, he said.

Each year, 150 gigatons, or 150 billion metric tons, of carbon are recycled through the atmosphere by plant and ocean activity. The 6 gigatons of carbon humans contribute to the atmosphere simply stays put.

“Look out,” Hill said. “Six thousand gigatons of carbon are still in the earth in the form of oil, coal and natural gas.”

To illustrate the “incredible economic and physical cost” of significantly reducing carbon output, Hill listed several actions that could reduce carbon emissions by 1 gigaton a year, citing data from a British Petroleum publication:

. Double the efficiency of 2 billion cars by requiring that they get 30 miles per gallon.

. Double the number of nuclear plants.

. Create 40,000 square kilometers of solar panels or 4 million windmills to produce hydrogen for fuel-cell-powered automobiles.

. Create 2 million windmills to replace coal-burning energy sources.

. Plant one-sixth of the Earth’s cropland with biomass plantations for ethanol production.

“The cost of making an attack on carbon dioxide in the atmosphere is going to be an incredible cost. It requires a tremendous economic commitment and I just don’t think we’re going to do it,” Hill said.