A recent Texas A&M AgriLife Research study to be published in the BioEnergy Research journal, outlines how mesquite, which grows in abundance in some regions of the U.S. southwest, could compliment the overall cellulosic biofuels project.
The paper is based on the study, “Economic and Greenhouse Gas Efficiency of Honey Mesquite Relative to Other Energy Feedstocks for Bioenergy Uses in the Southern Great Plains” (BioEnergy Research Impact Factor: 4.25. 06/2014; DOI: 10.1007/s12155-014-9475-z), and is coauthored by the AgriLife Research team that conducted the study: TAMU economist Dr. Seong Park; Dr. Tong Wang, a Postdoctoral Associate at Texas AgriLife Center; and rangeland ecologist Dr. Jim Ansley — all of the Texas A&M AgriLife Research & Extension Center Vernon campus. They were joined by Dr. Steve Amosson, a Texas A&M AgriLife Extension Service economist in Amarillo.
The researchers note that the US Environmental Protection Agency (EPA) implemented the revised Renewable Fuel Standard (RFS2) in 2010, mandating that a minimum of 16 billion gallons of cellulosic biofuel be produced by 2022. They observe that woody plants growing on native rangelands in the Southern Great Plains (SGP) region of the USA, such as honey mesquite and juniper species, may have potential as bioenergy feedstock, but caution that there are concerns regarding variability in biomass density distribution and high harvest and transport costs.
The objective of this study was to evaluate economic and greenhouse gas (GHG) performances of honey mesquite relative to irrigated and dryland sweet sorghum and dryland switchgrass bioenergy feedstock as delivered to the farm gate, based on four efficiency criteria: 1) biomass production cost, 2) energy cost, 3) GHG offset, and 4) GHG use. The researchers say their results suggest mesquite lags slightly behind switchgrass in the context of biomass and energy efficiency, but observe that mesquite appears superior to the other feedstocks in two categories: GHG offset efficiency and GHG use efficiency once land use change (LUC) effects are accounted for.
They say mesquite as a bioenergy feedstock in the SGP has greater potential if additional benefits such as increased grass production for livestock production and reduction in herbicide costs for mesquite control — both of which would occur as a result of mesquite harvesting. The coauthors conclude that mesquite production values on a per-land area basis are lower than the other feedstocks observed in this comparison and therefore could not supplant those feedstocks entirely, but mesquite does appear to be suitable as a complementary feedstock to contribute to total biomass feedstock demand.
“Bioenergy feedstocks have been promoted globally as potential means to offset greenhouse gas emissions by replacing fossil fuels such as gas and coal,” Dr. Park notes in a TAMU Agrilife news release. “In the U.S., federal support has played a key role in the biofuel industry. Examples include the Renewable Fuel Standard, established with the Energy Policy Act of 2005, and later expanded.”
“The Energy Independence and Security Act of 2007 stipulates the annual use of at least 16 billion gallons of cellulosic biofuels and a cap of 15 billion gallons of corn starch ethanol by 2022,” he continues. “In addition, biofuels are being examined from the standpoint of lifecycle greenhouse gas emission reductions.Despite the initial promise of grain-based biofuels, such as corn, there have been a number of concerns that grain-based biofuel may generate even higher greenhouse gas emissions than fossil fuels. Planting grain-based species could also accelerate the depletion of the Ogallala Aquifer or other scarce water resources.”
“The AgriLife Research study evaluated the economic and greenhouse gas efficiencies of honey mesquite compared to irrigated and dryland sweet sorghum and dryland switchgrass,” Dr. Park further notes. “Despite its higher energy density per pound, mesquite production values on a per-land area basis are lower than other feedstocks observed in this comparison and therefore could not replace them entirely, he said. But, mesquite appears to be suitable as a complementary feedstock to contribute to total biomass demand.”
“Our results suggest that mesquite lagged slightly behind switchgrass when the biomass and energy efficiency were considered,” comments Dr. Wang. “However, mesquite appeared superior to all the feedstocks in two categories greenhouse gas offset efficiency and greenhouse gas use efficiency once land-use change effects were accounted for,adding that the study results are pretty robust as they still hold true in the worst scenario proposed for mesquite.”
Dr. Park says mesquite has even greater potential if additional benefits such as increased grass production for livestock grazing and reduction in herbicide or mechanical removal costs for mesquite control are considered, and that The biggest negative is lower biomass production per acre per year for mesquite compared to other feedstocks.
However, attributes such as no fertilizer, irrigation or weed control costs; the unlimited re-harvest potential every 10-12 years; the ability to harvest year round; and a dry moisture content all help costs and improve carbon efficiencies.
“Additional studies are needed to put mesquites potential into perspective,” Dr. Park observes. “Future research areas could focus on developing a landscape scale, GIS-based decision support system to determine optimum feedstock harvesting and processing logistics on rangelands.”
Release author Kay Ledbetter notes that other potential studies outlined by Dr. Park could determine the rate of ecosystem restoration, hydrological impact, and ecological and economic sustainability of woody harvest, as well as compare these fuels on regional water use and water use efficiencies.
Dr. Seong Park conducts research in various areas of natural resource, including groundwater modeling and the animal manure management system in the Southern Great Plains, with his primary area of focus on analyzing economic dimensions of various management practices to improve economic values of resources.
His research interests include the following objectives:
1. Quantify the economic consequences and impact on water resources of alternative agricultural management practices in the Texas High Plains and Rolling Plains.
2. Develop an economic model of alternative, sustainable bio-fuel production systems using rangeland biomass.
3. Analyze costs and risks associated with alternative methods of improving air quality in livestock production facilities (PM control and GHG emission)
4. Assess the economic feasibility of using animal manures on cropland and grassland and of using manure for energy production with alternative technical approaches.
Dr. Jim Ansley notes on his TAMU Web page that he has always had an interest in ecology and how humans can manage ecosystems for sustainable production of products for mans use and yet maintain healthy ecosystems, and he’s also particularly interested in restoration of degraded ecosystems. His area of study is ecology of shrubs and grasses on rangelands, focused principally on the following long-term objectives:
1. Quantify the ecological impact of woody plant encroachment in grasslands.
2. Develop sustainable technologies to reduce encroachment of woody plants on grasslands and savannas.
3. Determine the potential of woody plants on rangelands for bioenergy uses.
Dr. Steve Amosson has served as an Area Economist for Texas A&M AgriLife Extension Service in the Amarillo District for the past 20 years, with his primary responsibility the 22 counties of the Texas High Plains. He places emphasis on developing educational resources and conducting applied research in support of all segments of the agriculture industry in the areas of marketing, management, finance, policy, and community development.
Dr. Amosson works closely with all levels of the agriculture industry to improve efficiency and profitability and to strengthen farm and ranch management, and has developed creative educational programming and analysis supported by an extensive applied research program that has positively affected clienteles bottom lines. Dr. Amossons recent contributions include the successful producer-oriented Master Marketer Educational Program, the Advanced Topic Series (ATS) of highly specialized seminars for Texas producers, and Personnel Management Seminars for Agribusiness.
Dr. Tong Wang is currently a postdoctoral research associate at Texas A&M AgriLife Research & Extension Center at Vernon, Texas. She obtained her Ph.D. in Economics from Department of Economics at Iowa State University in 2012. She describes her broad research interests as including animal health economics, food safety, sustainable livestock production, bioenergy production and applied econometrics. Her recent research focuses on:
1. Economics of livestock disease control and veterinary services
2. Measurement of the cost-effectiveness of on-farm food safety practices
3. Potential of utilizing invasive woody species for bioenergy production
4. The technical efficiency of cow-calf farms and their greenhouse gas emission
5. Evaluation of ecological, economic and environmental consequences of continuous and multi-paddock grazing in southern tallgrass prairie.
Texas A&M University AgriLife
Texas A&M University AgriLife
Dr. Jim Ansley