How environmentally friendly is wood pellets as a fuel source?

Europe has high hopes that wood will replace coal, but the industry has been criticized for rising carbon emissions and air pollution.

In search of a clean source of energy, an interesting option was found – compressed wood pellets. Softwood and hardwood from the forests of South America are dried, pressed into pellets 2-2.5 cm long, then burned as fuel in power plants, mainly in the United Kingdom and Europe, to heat homes and businesses.

Under rules set by the Paris Climate Agreement and reaffirmed by European regulators this summer, burning wood for electricity is considered carbon neutral, as long as the trees are replanted. Wood pellet companies claim that this type of fuel is an alternative to coal and is based on a sustainable resource – forests that will grow again in the future and absorb carbon dioxide from the atmosphere.

Many researchers and environmental organizations claim the opposite is true: burning wood results in the same air pollution as burning coal, and the requirement of carbon neutrality is a mistake that will increase emissions and inevitably lead to further warming of the planet. Moreover, it takes from several decades to half a century to restore the felled forests, and, according to climatologists, the planet simply does not have such an amount of time.

“It’s really simple,” says John Sterman, professor of management and director of the Sustainability Initiative at MIT’s Sloan Business School. – You are emitting carbon dioxide into the atmosphere right now, today. At the same time, the resumption of tree growth takes time, and it is not certain that this will happen at all. Perhaps you will absorb the emitted carbon dioxide from the atmosphere in a few decades or a century. It’s a killer adventure.”
In 2018, Sterman and two colleagues published a study in Environmental Research Letters in which they calculated that carbon dioxide emissions from burning wood are actually higher than from burning coal, because wood contains more moisture even when it is dried and pressed into pellets, and is a less efficient source of energy. The study says it will take 44 to 104 years for new tree seedlings to absorb this excess CO2 and make wood a cleaner fuel than coal. (A wide range of studies indicate that some forests grow faster than others.)

Stimulation of the production of wood pellets

In Washington, provisions to boost wood pellet production have been included in a massive $1.2 trillion infrastructure investment bill signed on Monday, November 2, 2021 by President Joe Biden, as well as in a social and climate change spending bill. worth $1.75 trillion, which is being discussed in Congress. On November 4, a group of 100 forest ecologists, climate scientists, and ecosystem experts, including Sterman, signed an open letter to President Biden and Congress calling for these provisions to be removed from the bills.

The infrastructure investment bill, now in law, approved an additional 30 million acres of federal public land for logging over the next 15 years. The law also provides logging opportunities for wood pellet plants and restricts the National Environmental Policy Act, which requires the US Forest Service to study the environmental impact of actions taken before making such decisions. The new law also provides subsidies for the development of carbon capture and storage (CCS) technologies in factories that produce and burn wood pellets.

As for the larger budget conflict resolution bill still under negotiation, the Innovation from Wood section also provides subsidies for logging on both federal and private lands, as well as subsidies for forest biomass energy, wood pellet production, and cross-country – glued timber (a type of prefabricated wood panels used in house building).

In their letter, the scientists argued that stimulating more commercial-scale logging to generate electricity by burning forests “ignores the advice of hundreds of climate scientists and foresters who have previously informed Congress that these industries significantly increase greenhouse gas emissions and exacerbate climate change. a crisis”.

Not all experts share this view. Bob Abt has been researching the ecology and economics of southern forests for over 40 years and is Distinguished Professor of Natural Resources at North Carolina State University. Abt says that by balancing economic and environmental conditions, greenhouse gas emissions from the use of wood pellets can be less than emissions from the use of coal. In order for this equation to work, so that the amount of carbon emitted by burning wood to generate electricity today is offset by tree growth in the future, several requirements must be met.
First, says Abt, forest land owners should grow fast-growing trees, such as pines or mixed hardwoods found in the south. The same process will not work as well in the forests of New England or the Pacific Northwest, as reforestation in these regions takes much longer. Secondly, it is necessary to ensure that landowners who sell wood to pellet producers, continued to use their lands to grow commercial breeds. Abt says that as the demand for electricity generated by burning wood rises, so will the price of wood. This will serve as an incentive for forest land owners to grow the forest to maturity, rather than converting the same land into grazing land or agricultural land for growing seasonal crops, or selling it to developers.

A 2017 study by scientists at Oak Ridge National Laboratory found that the sprawl of residential areas, trucking routes and shopping complexes could also threaten forest development. “Urbanization – currently the biggest cause of deforestation in the southeastern United States – is more likely to spread to forest landscapes if forest land owners do not have sufficient opportunities to generate income from the sale of their timber,” the report says.

If land that is forested to produce wood pellets is used for other purposes in the future, then the carbon that is released into the atmosphere today from burning pellets to generate electricity will not be reabsorbed by such trees in the future. This means that wood pellet manufacturers’ patent claims for carbon neutrality may depend on the price that owners in North Carolina, Georgia or Mississippi can get for their land – something that is difficult to predict for decades to come.

The issue of power generation

Abt thinks using forests for energy may not be ideal, but it’s a step in the right direction. He says all possible solutions to the climate crisis need to be considered. “As for the wood coming from the south,” says the expert, “I can say with confidence that in most cases it is better than coal.”

In countries like the UK where there is no domestic supply of natural gas, there is a big push to burn wood pellets.

For example, the British company Drax in 2013 converted the largest coal-fired power plant in the island state in North Yorkshire into a thermal power plant for burning pellets. The company now produces enough electricity for 4 million homes, with wood pellets imported from the US. According to Ali Lewis, head of media and public relations at Drax, Drax currently operates 13 pellet plants in the US and Canada and is building three more in Arkansas.

Lewis says companies like Drax use the tops of the trees, the undergrowth and small branches from each tree, material that is often wasted in other woodworking industries such as lumber or paper.
Thinning trees and shrubs helps keep the forest resilient to insects and fires, the company says. “The scientific approach to sustainable forestry is clear – active forest management brings economic and environmental benefits – this results in better quality trees, more wildlife and healthier forests,” Lewis wrote in an email to WIRED. “It’s also vital to protecting forests from wildfires, pests and diseases.”

Drax plans to introduce carbon capture and storage (known as BECCS) biomass energy technology at several new plants in the UK and Europe, Lewis said. The first BECCS unit at Drax could be commissioned in 2027 and the second in 2030. The idea is to capture carbon dioxide emissions from pellets before they enter the atmosphere, turn the gas into a liquid form of CO2, and then send it to permanent storage on the bottom of the North Sea, says Drax.

Lewis says that each new BECCS installation will capture four metric tons of CO2 per year. “A total of eight metric tons will make Drax’s carbon capture project the largest CCS project in the world,” Lewis wrote. “It also means that Drax will capture more CO2 than it emits throughout its operations, creating a negative carbon footprint for the company.”

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