Wood Pellets for UBC Boilers Replacing Natural Gas Based on LCA

Abstract

This report studies the feasibility of replacing natural gas with wood pellets for UBC boilers. A gasification system is proposed to be installed in the UBC boiler house to convert wood pellets into syngas that can be used to displace the energy required from natural gas to produce steam. The environmental impact and the cost of implementation between wood pellet technology (case 2) and natural gas technology (case 1) are compared. The environmental impact for the two cases is compared with life-cycle assessment (LCA). The life cycle of natural gas is divided into the following stages: production, transmission, and final use. The life cycle of wood pellets is divided into the following stages: harvesting, transportation, pellet production, and final use. The environmental and human impacts of each stage are evaluated in terms of global warming potential (GWP), smog formation potential (SF), acid rain potential (ARP), and health impact. Moreover, the operating cost of using wood pellet as the energy source is examined. In addition, potential air emission reduction units that help further minimize the emissions from using wood pellets are investigated. It is found that most local air emissions, especially carbon dioxide, decrease when wood pellet is used. However, when the entire life-cycle is taken into the consideration, the VOC, SOx, and PM emissions increase significantly. Also, a preliminary economic analysis showed that implementation of the new system which utilizes wood pellets and natural gas for the production of steam generates an annual saving of approximately $2 million. Different valuation methods show that using wood pellets is an improvement over natural gas.