Economic Feasibility of Mesquite Biomass for Electricity Production: Projections of the Long-Term Sustainability of Two Harvest Options

Mesquite and similar woody plant species occupy over 28 million hectares in the southwestern USA and often negatively affect the rural economic sector by reducing livestock forage production, increasing bare ground, and interfering with livestock handling. Current control methods that temporarily suppress the growth of these woody plants include herbicide sprays, mechanical treatments, and prescribed fire. One alternative to current control practices is to utilize mesquite biomass for electricity generation. This study examined the economic feasibility of mesquite biomass as a potential bioenergy feedstock for electricity production using a Faustmann-type model with five mesquite biomass accumulation scenarios, which take into account variations in rates of standing biomass accumulation and tree density reestablishment after harvest with the aboveground-only (AG) harvest option or the whole-plant (WP) harvest option. The estimated regrowth functions were then incorporated into a modified version of the Faustmann model to determine the optimal harvesting length of mesquite that maximizes the net present value of a power plant using mesquite biomass. Results indicated that mesquite biomass has economic potential to be a source for electricity generation. A long-term bioenergy harvest system with regrowth following AG harvest was much more cost-effective than reestablishment from germination of new seedlings after WP harvest, even though harvest cost is higher in the AG than that in the WP harvest option. In addition, the utilization of mesquite for bioenergy would enhance other more traditional income streams from these lands including livestock grazing and wildlife hunting leases (with patterned harvesting of mesquite) and would reduce herbicide or mechanical costs that ordinarily are necessary for woody plant control. Compared to conventional coal, a lower economic return was found when the mesquite biomass was used for electricity production, but a possible carbon emission tax would make mesquite biomass competitive with conventional coal.