In the pursuit of sustainable energy, the use of trees to produce biofuels has gained significant attention. The southern United States, with its vast forested areas (86% of which are owned privately), has naturally become a hub for the development of renewable energy alternatives from trees.
Forest biomass, which can be converted into energy-producing resources, includes but is not limited to the following:
- Tree trimmings
- Logging slash
- Forest thinnings
- Roundwood that has no other market
- Residuals like sawdust, bark and wood chips from forest product mills
- Other organic matter
In addition to offsetting CO2 emissions, swapping fossil fuels with renewable drop-in biofuels made from trees could also help decrease wildfire risk by prompting the removal of flammable materials like brush, small diameter trees and damaged trees – which could otherwise fuel and intensify wildfire.
By tapping into these emerging biofuel markets, private forest owners have an added opportunity to further grow their forest’s profitability in a sustainable manner.
“Connecting southern forest landowners to the biofuels market could provide additional revenue streams to help landowners maintain the health and viability of their lands,” said Tim Lowrimore, Georgia State Forester. “By keeping forests as forests, our landowner base delivers valuable amenities like fresh air to breathe, clean water to drink and support for the southern economy.”
Wood pellets are a type of biomass fuel made from compressed sawdust, wood shavings and other residual materials. Wood pellets have a high energy density, making them efficient for generating heat and electricity. Their consistent composition, low moisture content and high heat value ensures optimal combustion.
Wood pellets are considered a carbon-beneficial solution to addressing climate change, releasing approximately the same amount of carbon dioxide, when burned, as the trees absorbed during their growth. With private forest owners regenerating an average of 43% more wood than they harvest, the carbon cycle in this case remains balanced despite the carbon released.
According to the U.S. Department of Agriculture, “Pyrolysis is the heating of an organic material, such as biomass, in the absence of oxygen… Because no oxygen is present, combustion does not occur. Rather, the biomass thermally decomposes into combustible gases [including syngas] and biochar.” This process can use lignocellulosic feedstocks, such as forest biomass, to generate these products. While biochar is primarily used as a soil amendment, syngas (synthesis gas), can be used as a biofuel.
Syngas can be used in gas turbines, internal combustion engines or boilers to generate electricity or heat, providing a cleaner-burning fuel option with lower emissions than traditional fossil fuels. Before use, syngas typically undergoes processes to remove impurities, particulate matter and sulfur compounds to ensure optimal performance and reduce potential environmental impacts. It can then be used directly for combustion or upgraded further into a liquid fuel for use in transportation.
Another means of yielding biofuel from forest biomass is through the anaerobic process. With this method, bacteria break down organic matter, without oxygen, to produce a renewable biogas. That biogas may then undergo additional upgrading processes to produce biomethane, which can be injected into the natural gas grid or used as transportation fuel.
Historically, the utilization of anaerobic processes has not included lignocellulosic feedstocks/forest biomass due to its chemical composition – Mainly using sugars to produce ethanol or methanol. However, recent work has honed in on the use of volatile fatty acids found within lignocellulosic feedstocks, and catalytic upgrades to high-octane fuel for internal combustion engines. This may offer promise for commercialization, stimulating the growth of a new biofuel industry, creating job opportunities and enhancing economic development in the South by delivering local resources to reduce dependence on imported fossil fuels.
“The development of drop-in biofuels from lignocellulosic feedstocks represents an exciting opportunity for southern forestry as we transition our transportation infrastructure into a more sustainable, carbon-neutral future,” said Marcus Taylor, Wood Innovations Coordinator for the USDA Forest Service’s Southern Region. “We have made huge strides with respect to electric vehicles, but there are limits to implementing batteries in sectors like aviation and long-distance trucking. Developing transportation fuel markets for low-value woody biomass represents a win for forest management, wood processing and our efforts to mitigate climate change, while maintaining our existing infrastructure and lifestyles.”
The sustainable use of trees as biofuel in the southern United States offers promising avenues for renewable energy and environmental conservation. While drop-in biofuels offer favorable renewable energy solutions, as well as key economic and environmental benefits, their use requires deliberate application and careful resource management to ensure the continued health, vitality and sustainability of our southern forests. It is crucial to ensure that source material for wood pellets and biofuels comes from sustainably managed forests. By adhering to responsible sourcing practices and ensuring the integrity and health of southern forest ecosystems, we can harness the potential of these biofuels while ensuring a balanced approach toward a sustainable future.