Economic Utilization of Forests for Bioenergy

Two recent issues have reinvigorated bioenergy research activity within the Northern Research Station. One is the groundswell of interest in mitigating global climate change by reducing atmospheric carbon dioxide (CO₂) accumulation. Bioenergy from harvested wood results in “no net carbon addition”, because the CO₂ released from wood is not from additional fossil fuels, into the new forests that grow back to replace the harvested one. Second is the increasing cost and threats to national security associated with crude oil imports. The Northern Research Station (NRS) has worked with the U.S. Department of Energy since the first OPEC oil embargo in 1973.

Research Studies

Predicting and Mapping Biomass of Poplar Energy Crops in the North Central United States
Populus species and hybrids (i.e., poplars) have demonstrated high yield potential in the North Central United States as short-rotation woody crops (SRWCs). However, the ability to predict biomass yields for sites not currently in SRWCs is limited. As a result, stakeholders are also limited in their ability to evaluate different areas within the region as potential supply sheds for wood-based bioenergy facilities. A reliable method for predicting biomass productivity across the region is needed; preferably, such a method will also lend itself to generating yield maps that stakeholders can readily use to inform their decision-making processes.

Breeding and Selecting Poplar for Biofuels, Bioenergy, and Bioproducts
Hybridization of poplars occurs naturally among certain taxonomic sections, as well as from planned breeding efforts. Given that most of the variability of poplars is at the species level, both intra- and inter-specific hybridization have been vital tools for producing progeny that outperform either or both parents for biologically and economically important traits. It is important to refine breeding, testing, and selection protocols so that new, superior poplar genotypes can replace their underperforming counterparts.

Genetics and Genotype × Environment Interactions Affecting Adventitious Rooting and Early Establishment of Poplar Energy Crops
Gaining knowledge about the genetics and genotype × environment interactions affecting adventitious rooting is important for energy crop production. First, rapid and extensive rooting reduces establishment costs by permitting the use of unrooted cuttings as commercial stock rather than rooted cuttings. Second, assuming concomitant and well-balanced shoot development, rapid and extensive rooting promotes early growth, reducing vegetation management costs and the time period to crown closure. Third, rapid and extensive rooting that is stable in the face of varying environmental conditions can increase the period of time during which successful planting can occur, increasing operational flexibility.  

Sustainable Production of Woody Energy Crops with Associated Environmental Benefits
Increasing human population levels at regional, national, and global scales have heightened the need for proper management of residential and industrial waste. Contaminants from this waste stream have polluted water, air, and soil much faster than traditional technologies could remediate the problem. Therefore, we are combining intensive forestry and waste management methods to increase the potential for producing woody crops for energy and fiber, along with decreasing the environmental degradation associated with waste disposal and subsequent waste water production.

Phyto-Recurrent Selection: A Method for Selecting Genotypes for Phytotechnologies
The success of certain phytotechnologies has prompted the use of wastewaters as a combination of irrigation and fertilization for woody crops such Populus species and their hybrids (i.e., poplars). A common protocol for such efforts has been to utilize a limited number of readily-available genotypes with decades of deployment in other applications, such as fiber or windbreaks. However, it is possible to increase phytoremediation success with proper genotypic screening and selection, followed by the field establishment of clones that exhibited favorable potential for clean-up of specific contaminants. While such efforts are limited for environmental remediation, centuries of plant selection success in agronomy, horticulture, and forestry validate the need for similar approaches in phytotechnologies. 

Salt Tolerance and Salinity Thresholds of Woody Energy Crops Irrigated with High-salinity Waste Waters
There is a need for environmental practices that merge intensive forestry with waste management. Producing short rotation woody crops for energy, fiber, and environmental benefits requires adequate irrigation and fertilization, which can be supplied via waste waters including landfill leachate. Yet, leachate often contains elevated levels of salts such as chloride and sodium that cause leaf chlorosis and necrosis, decreased biomass accumulation, and increased mortality. Therefore, there is a pressing need to learn about the response of poplar energy crops when salts are taken up into root, leaf, and woody (stem + branch) tissues, as well as identifying thresholds of salt concentrations and salinity that can be recommended for these crops in both field testing and production plantations.

Carbon Implications of Poplar Energy Crops Throughout the Energy Supply Chain
Woody production systems and conversion technologies are needed to: maintain healthy forests and ecosystems, create high paying manufacturing jobs, and meet local/regional energy demands. Poplars are dedicated energy crops that can be strategically placed in the landscape to conserve soil and water, recycle nutrients, and sequester carbon. However, key environmental and economic uncertainties preclude broad-scale production of biofuels/bioproducts from poplar wood. Therefore, building on decades of research conducted at our Institute and throughout the region, we are evaluating the fate of carbon in soils and woody biomass, soil greenhouse gas emissions, and conversion efficiency barriers throughout the energy supply chain.

An Approach for Siting Poplar Energy Production Systems to Increase Productivity and Associated Ecosystem Services
Highly productive poplars grown primarily on marginal agricultural sites are an important component of our future Midwest energy portfolio. Additionally, poplars can be strategically placed in the landscape to conserve soil and water, recycle nutrients, and sequester carbon. These purpose-grown trees are vital to reducing our dependence on non-renewable and foreign sources of energy used for heat and power. Establishing poplar genotypes that are adapted to local environmental conditions substantially increases establishment success and productivity. But, it is difficult to predict field trial success in landscapes where the crop has not been previously deployed.