Lumberyard
Credit: Mark Stebnicki / Creative Commons

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A new law encouraging the development of wood-fired combined heat and power plants in Maine is drawing praise for its potential to benefit the economy and the environment.

But some climate activists are skeptical, saying questions remain about whether the program will cut carbon emissions as intended. 

The legislation, signed by Gov. Janet Mills in April, establishes a program to commission projects that will burn wood to create electricity and also capture the heat produced for use on-site — heat that would go to waste in a conventional power plant.

Proposals for these facilities are expected to come from forestry or forest products businesses that could use their own wood byproducts to fuel the plants, saving them money on heat and electricity costs and providing an extra revenue stream when excess power is sold back into the grid.

“It’s renewable energy that is produced by local loggers and providing jobs for our local community,” said James Robbins, president of Robbins Lumber in Searsport, Maine, which has operated its own combined heat and power plant since 2018. 

Supporters like Robbins say these facilities will uplift struggling sectors of the economy while helping reach the goals of Maine’s climate plan, which calls for the state to reduce emissions by 80% by 2050. Some environmental activists, however, doubt that wood can ever be an efficient fuel and worry that these projects will in fact increase carbon emissions. 

“This is really an economic development tool to help prop up mills and not a climate solution,” said Greg Cunningham, director of the clean energy and climate change program at the Conservation Law Foundation. 

Economy and environment?

Over the past 15 years, at least four of Maine’s paper mills have shut down, citing competition from overseas, decreasing demand, and soaring energy costs. A sixth had its operations sharply curtailed by an explosion at the facility in 2020.

These closures have meant less of a market for the wood chips and low-grade wood byproducts — often called residual wood — that lumber mills and loggers have generally sold as raw material for paper production. And with less demand, prices fell sharply, Robbins said. 

“It created a huge surplus on the market here,” he said. 

For businesses struggling to find buyers for their residual wood, the opportunity to build combined heat and power plants offers financial benefits. The systems can reduce or eliminate the cost of heating fuel, and the power produced can be sold back to the grid for additional revenue. These facilities could also help the industry as a whole by creating new markets for residual wood, thus buoying prices. 

Robbins Lumber uses the heat generated from its system to power kilns that dry out lumber before sale. The electricity is all sold back into the grid through a power purchase agreement. The arrangement has been doing exactly what it was intended to do, Robbins said.

“We are also burning sawdust, bark, wood chips, and biomass from our outside contractors,” he said. “It’s definitely created a consistent market for residuals, which is what we hoped for.”

Advocates also believe these plants will be environmentally beneficial. If not put to another use, residual wood might otherwise have been left to decompose and release its stored carbon into the atmosphere. Used in one of these systems, however, the wood will displace the fossil fuels that would otherwise have been used to generate the same heat and power. 

“Yes, it’s releasing CO2, but it was going to release CO2 through decomposition anyway,” said Ivan Fernandez, a professor at the University of Maine’s School of Forest Resources and a member of the Maine Climate Council. “As far as what the atmosphere sees, [combined heat and power] is a really good tool in the toolbox in our climate response.”

On-site combined heat and power facilities also make it easier for logging operations to thin small or weak trees from the forest and put that wood to use, Fernandez said. This sort of culling helps the larger trees grow yet more and sequester even more carbon, so there is no new loss of carbon capture because of the removal of the smaller trees, he said. 

Furthermore, the continual growth of new trees allows for the carbon released by burning wood to be naturally recaptured, said Patrick Strauch, executive director of the Maine Forest Products Council. 

“We look at it as a pretty good balance,” he said. “There is no doubt that it contributes carbon to the atmosphere, but our forest resources at the same time are pulling carbon out.”

Climate advocate unconvinced

Not everyone is convinced of the environmental wisdom of wood-fired combined heat and power, however. Burning wood produces more carbon dioxide per unit of heat generated than burning natural gas or heating oil. Many climate advocates worry that the carbon-capture capacity of forests is not enough to offset these higher emissions. 

“There is significant disagreement on whether it is truly carbon neutral and emission-free,” said Jeff Marks, Maine director and senior policy advocate for environmental nonprofit the Acadia Center.

In theory, combined heat and power plants can be 75% to 90% efficient, according to some research. By way of comparison, centralized electric power generation and onsite heat production are 31% and 80% efficient, respectively, according to a report from Pennsylvania State University. 

But many variables can lower that number. Of particular concern with wood is the moisture level of the fuel used: The more water in the wood, the less efficiently it burns. Residual wood from wood harvesting operations is likely to have a higher moisture content than wood from lumber processing. 

Furthermore, the exact rules regulating the new law have yet to be hashed out, leaving more room for doubt, Cunningham said. The law, for example, requires projects to be “highly efficient,” but leaves it to the state Public Utilities Commission to define that term. The legislation also requires a biennial report assessing the success and sustainability of the program but, again, the details are scarce. And the law includes no provisions for the monitoring or enforcement of the rules it creates.  

These factors leave Cunningham skeptical that wood-fired combined heat and power could ever be a climate-smart choice. 

“It will not be highly efficient — it’s not feasible with a wood fuel,” he said. “It will not to any extent be a climate solution.”

The law caps the program at a total capacity of 20 megawatts statewide, a tiny fraction of the 3,344 megawatts of generating capacity the state already has. Still, the climate implications of the new law matter, Cunningham said. 

“The money available in the state of Maine to fight climate change and invest in clean energy programs is finite,” he said. “When any amount of it is siphoned off for an anti-climate program, it’s problematic.”

Sarah Shemkus

Sarah is a longtime journalist who covers business, technology, sustainability, and the places they all meet. She has covered the workings of small-town government in New Hampshire, the doings of alleged swindlers and con men, and the minutiae of local food systems. Her work has appeared in the Guardian, the Boston Globe, TheAtlantic.com, Slate, and other publications. Based in Gloucester, Sarah covers the state of Massachusetts.