Plant-based energy cuts iron and steel carbon emissions by nearly half

March 28, 2021

Trees and shrubs could help make steel. (AP Photo/Mary Esch)

As climate change necessitates an increasingly urgent shift away from fossil fuels and toward renewable energy, researchers are exploring strategies for using excess forest trees and shrubs as organic plant-based energy sources in the emissions-heavy iron and steel industry.

Offering Sweden as a case study of a country that can viably sustain such a concept, a study published in the April 2021 edition of Applied Energy delves into the cost effectiveness, availability and feasibility of forest biomass as an energy source. After accounting for supply chain emissions, researchers deemed it a fine choice for the industry, as it appeared to nearly halve carbon dioxide emissions, which heavily contribute to climate change.

Using models and scenario analyses that included inputs such as transportation costs, biomass demand throughout the country's other industries, biomass resource availability and secondary carbon dioxide emissions, the team was able to map out the direct benefits and consequences of using forest biomass in Sweden's iron and steel industry.

"By replacing fossil fuels and reductants [with forest biomass], fossil CO2 emissions during iron- and steel-making can be reduced by 43%," said Chinedu Nwachukwu, a Ph.D. candidate at the Luleå University of Technology and the lead author of the study. 

Sweden is responsible for several million tons of carbon emissions from fossil fuels each year. According to the paper, greenhouse gases emissions from the iron and steel industry account for 34% of carbon dioxide emissions nationally, which corresponded to 10% of all fossil fuel emissions in 2018.

If the researchers' suggestions are applied to other countries they believe are similar enough to use forest biomass, it could help to chip away at staggering amounts of carbon emissions. The U.S. alone contributes around 5 billion tons of carbon dioxide emissions from fossil fuels annually.

The concept of using biomass as a form of energy has existed since the beginning of humankind. When cavemen in the prehistoric era burned wood for heat, that energy was derived from biomass, which is essentially organic matter that can be used as fuel or electricity.

Because plants take part in photosynthesis, energy from the sun is conserved within trees and crops as the plants remove carbon dioxide from the atmosphere. When they're later burned, the hidden gas is released and can be converted into usable energy for human activities. This process returns the carbon dioxide to the environment, providing a zero net gain of emissions. 

Biomass provided the primary mode of energy development until more-affordable fossil fuels were invented in the mid- to late 1800s. But fossil fuels generate extra carbon dioxide emissions, which compound and create dense pollution.

"Fossil fuels are still cheaper to use than any renewable alternative," Nwachukwu explained. "Replacing coal with biomass alternatives is significantly more expensive." 

"However," she continued, "biomass-based gases replacing more expensive fossil fuels — like heavy or light fuel oils — are shown to be cheaper alternatives in our analysis."

The researchers noted that they only considered types of biomass that were the byproduct of processes that would happen anyway, such as harvesting from sawmills. This ensured that potential extensive manufacturing of biomass products wouldn't negate the alternative energy source's benefits by adding to emissions. A common stance about forest biomass is that because wood burns less efficiently, the amount of burning needed would lead to greater emissions overall.

"The emissions coming from using the fuels and reductants derived from these assortments are considered to be CO2 neutral, thus reducing the amount of CO2 emissions that would typically come from fossil fuels and reductants," Nwachukwu said.

The researchers stress that even though their work focuses on Sweden's iron and steel industry, or ISI, the results can be applied to a range of other countries with the supplies to work with biomass in the ways suggested, such as using byproduct that is already available.

"Biomass utilization in the ISI can be implemented in countries having sufficient and sustainable domestic biomass resources," Nwachukwu said. "While Sweden is one of such countries, Canada, China, the USA, France and Finland are some other examples."

She added, "Having supportive national policies, like in Sweden where the government aims toward net-zero CO2 emissions by 2045, was another motivation to investigate strategies to decarbonize the ISI."

As of now, many countries attempt to prevent excessive fossil fuel emissions by imposing penalty fees for industries that go beyond a proposed limit. However, Nwachukwu believes that such a restriction isn't enough.

She called for new policies enforcing mandatory targets for the iron and steel industry to slowly integrate biomass in energy processes. As a caveat, the study did find that the cost of biomass would initially be higher than normal for a country's industry, capping out at a 27% increase in price, but certain tools and incentives could compensate for that.

Additionally, Nwachukwu noted that "a significant challenge" to using biomass is that it can't replace all of the coal and coke fuel used in the dominant process of fossil fuel energy generation, which uses a blast furnace reactor, "due to technical limitations that would affect process operations."

As a solution, she suggests, "Mandatory targets would have to consider other support tools or incentives, since switching to biomass-based fuels and reductants will come at a cost to the ISI."

The paper, "Exploring the role of forest biomass in abating fossil CO2 emissions in the iron and steel industry – The case of Sweden," published in the April 2021 edition of Applied Energy, was authored by Chinedu Maureen Nwachukwu and Elisabeth Wetterlund, Luleå University of Technology; and Chuan Wang, Swerim AB.

Correction: A previously published version of this article referred to Chinedu Nwachukwu by the wrong gender. The error has been corrected. An earlier version also incorrectly stated that the researchers focused on the iron and steel industry because it tends to rely on more expensive fuels. This is not the case.

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