A study from Columbia Climate School calculated the fossil fuel usage of building renewable infrastructure and found that, if installed quickly, future expansion can be powered by lower-carbon forms of energy.
The researchers looked the cost of the green transition in greenhouse gas emissions rather than monetary expenditure.
"The message is that it is going to take energy to rebuild the global energy system, and we need to account for that," said lead author Corey Lesk. "Any way you do it, it's not negligible. But the more you can initially bring on renewables, the more you can power the transition with renewables."
The researchers calculated the possible emissions produced by energy use in mining, manufacturing, transport, construction and other activities needed to create massive farms of solar panels and wind turbines, along with more limited infrastructure for geothermal and other energy sources.
Previous studies have projected that the necessary cost of new energy infrastructure amounts to roughly $3.5tr annually until 2050 to reach net-zero emissions, or up to about $14tr for the US alone in the same period.
At the current pace of renewable infrastructure production, which is predicted to lead to warming in the region of 2.7°C globally by 2100, the researchers estimate these activities will produce 185 billion tons of carbon dioxide.
This alone is equivalent to five or six years of current global emissions – a hefty added burden on the atmosphere.
However, if the world builds the same infrastructure fast enough to limit warming to 2°C, those emissions would be halved to 95 billion tons, the researchers said. Furthermore, ambitious efforts to limit warming to 1.5°C would cost just 20 billion tons in emissions by 2100 – just six months or so of current global emissions.
The researchers believe the estimates are probably quite low as they do not account for the materials and construction needed for new electric-transmission lines, nor batteries for storage which are both highly energy- and resource-intensive products.
Nor do they include the cost of replacing gas- and diesel- powered vehicles with electric ones, or making existing buildings more energy-efficient. The study also looks only at carbon-dioxide emissions, which currently cause about 60 percent of ongoing warming – not other greenhouse gases including methane and nitrous oxide.
Other effects of the move to renewables are hard to quantify, but could be substantial. All this new high-tech hardware will require not just massive amounts of base metals including copper, iron and nickel, but previously lesser-used rare elements such as lithium, cobalt, yttrium and neodymium.
Many commodities would probably have to come from previously untouched places with fragile environments, including the deep sea, African rain forests and fast-melting Greenland.
Solar panels and wind turbines would directly consume large stretches of land, with attendant potential effects on ecosystems and people living there.
"We're laying out the bottom bound," said Lesk of the study's estimates. "The upper bound could be much higher." But, he says, "the result is encouraging."
Lesk said that given recent price drops for renewable technologies, 80 to 90 per cent of what the world needs could be installed in the next few decades, especially if current subsidies for fossil-fuel production are diverted to renewables.
