Sustainable Campus: Reducing Environmental and Financial Burdens by Using Pruned Branches for On-Campus Energy

Abstract

Sustainability activities on university campuses are an important part of building a sustainable society. As a part of this effort, the present study quantitatively evaluated the reduction in greenhouse gas (GHG) emissions and disposal costs upon use of pruned branches for on-campus energy use in a Japanese university. The pruned branches are currently used off campus as fuel for biomass power generation, whereas the proposed systems include their on-campus use for heating through wood-chip heaters in a greenhouse or through wood stoves in buildings. The GHG balance was evaluated using a life-cycle assessment, and the cumulative costs over a 20 y period were estimated. Using pruned branches for on-campus heating was 70–180% more effective in reducing GHG emissions than the current off-campus power generation system. Using branches for heating eliminated the emissions produced by the transportation of pruned branches off campus and had higher thermal efficiency than power generation, which was conducive to the replacement of larger quantities of fossil fuel. In addition, the payback period of the proposed systems was estimated at 2 and 4 y for wood stove and wood-chip heater systems, respectively. For the 20 y period, the cumulative costs can be reduced by approximately 20%.