Paper recycling, an electricity hog, may spike CO2 — study

Source: By David Iaconangelo, E&E News reporter • Posted: Wednesday, October 28, 2020

Recycling more paper won’t do much to lower greenhouse gas emissions and might even raise them — unless global recyclers switch to renewable electricity, according to a new study.

Published in Nature Sustainability this month by researchers at Yale University and University College London, the study looked at how the global production and disposal of paper might be changed in order to cut emissions over the next three decades. Paper currently accounts for 1.3% of greenhouse gas emissions.

The findings were surprising, said lead author Stijn van Ewijk, a postdoctoral associate at Yale’s Center for Industrial Ecology. “We found that recycling, all else being equal, makes no difference or even leads to a small increase [in emissions],” he said.

The problem is that recyclers tend to “pulp” their waste paper — that is, break it down and mix it into the raw material for new paper — using either fossil fuels or grid electricity. Often the electricity is derived from gas or coal.

Papermakers that source their raw material from trees, conversely, often get both power and heat from a low-carbon byproduct of the wood pulp known as “black liquor.”

If the entire world recycled all of its waste paper without new policies to decarbonize electricity, greenhouse gas emissions could rise by as much as 10%, according to the study.

That finding suggests that when it comes to paper production, the issues of forest conservation and emissions reductions may have a more complex relationship than many people think. Members of the public often see conservation and climate action as entwined. And EPA’s waste reduction models show that more recycling would cut greenhouse gas emissions as well, chiefly because there would be more forest left to suck up CO2.

The team from Yale and University College London didn’t try to calculate how that assumption of larger forests around the globe would affect their findings.

“You have to be very sure of that [relationship between recycling and larger forests], if that’s what you’re depending on for emissions benefits,” said van Ewijk. “It’s very hard to estimate.”

Nor did they derive U.S.-specific results from their models. “You have to keep in mind that it’s a global market for pulp and paper,” van Ewijk added.

The authors also cautioned that their findings shouldn’t be taken as discouraging recycling.

Rather, it highlighted the importance of renewables, they said. Substituting renewables for fossil fuels as a source of grid power or on-site electricity would do more to cut recycling-related greenhouse gas emissions than any other step through 2050, they found.

If the world undertook a “radical” increase in paper recycling while transitioning to carbon neutral power by 2050, it would reduce emissions by 6% annually over that period, according to the research.

“Cleaning up the energy supply really makes the big difference. That’s going to get you to the climate targets [in the Paris Agreement],” said van Ewijk.

Combining clean electricity with reforms of landfill practices could bring those reductions as high as 10%, according to the paper. That could include capturing methane from landfills — an especially useful tool for recyclers, which could use the methane to generate heat instead of fossil fuels.

Other technologies, like hydrogen and carbon capture, aren’t readily available at scale to reduce emissions from industrial heat processes, van Ewijk pointed out.

“These aren’t things we can offer as a recommendation,” he said. “There’s no easy answer to the question of how we will generate a lot of low-carbon heat in the future.”