Converting Riparian Restoration Waste to Energy: Testing Tamarisk (Tamarix spp.) Woody Biomass as Fuel for Downdraft Gasification

Abstract

In the course of riparian ecological restoration work, tamarisk biomass is often piled and burned, generating air pollution, or shipped to landfills—a costly alternative. Information on processing and utilizing tamarisk biomass is becoming increasingly valuable in light of the spread of the tamarisk leaf beetle (Diorhabda spp.) as a biological control agent. As beetle populations expand, information on the properties of both green and beetle-killed tamarisk biomass and their suitability as feedstocks for conversion to energy will be useful for land managers seeking to offset the costs of tamarisk removal, restore wildlife habitat and ecosystem function, and reduce wildfire threat posed by standing dead tamarisk. Field trials, feasibility studies, and economic analyses are needed to enable pioneering restorationists and land managers to incorporate tamarisk biomass utilization into their project plans. We collected both green (live) and dead tamarisk impacted by the tamarisk leaf beetle and tested both as fuels for conversion to a clean producer gas via downdraft gasification and then to electricity in a spark-ignited engine/genset at Community Power Corporation in Littleton, Colorado. Both green and dead tamarisk chips were good fuels for gasification, performing more efficiently than a sample of mixed softwood. Further, the data suggest that significantly more energy can be recovered from tamarisk when harvested green, compared to waiting for the tamarisk to die and age. When incorporated into a comprehensive restoration plan, tamarisk appears to have potential to be used as a valuable energy source rather than viewed as unwanted waste.