Cellulosic Ethanol from Forest Biomass and Carbon Sequestration: Nonindustrial Private Forest Owner Operation and the Modeled Impact on Cellulosic Ethanol Carbon Emissions

Abstract

Cellulosic ethanol has long been put forward as a more carbon-neutral fuel source than corn ethanol—trees grown for cellulosic ethanol production sequester carbon from the atmosphere and are less intensive to manage. Limits on the forest’s rate of growth and the limited distance over which forest biomass can be profitably transported mean that forest owners in the vicinity of a woody-biomass biorefinery must be willing to harvest their timber as feedstock. I conducted a survey of 500 nonindustrial private forest, or NIPF, owners in Michigan to understand their management decision-making. The survey found a significant correlation between owners supporting sales of their timber for cellulosic ethanol production and owners desiring to maintain the same forest for carbon sequestration. However, these two ways of using NIPF land to mitigate net carbon emissions are mutually exclusive. I constructed a new computer model, the Cellulosic Ethanol BioRefinery Accounting Model (CEBRAM), which examines this tradeoff of how best to mitigate net carbon emissions using NIPF land. The model was parameterized for current forest species and growth in Michigan. The overall rate of NIPF biomass harvest and provision by NIPF owners to the biorefinery (referred to as ‘participation’) indicated by the survey was 47%. At this participation rate the net carbon balance for the biorefinery calculated on an energy basis was 0.03 MgC/ha over the 40 year simulation. Alternatively, when considering both the biorefinery and C storage in non-participating NIPF land within the transport radius, the net carbon was 10.74 MgC/ha over 40 years. If all the NIPF landscape was forested, 20.2 MgC/ha over 40 years would be sequestered, and to compare the presence of the biorefinery with the opportunity cost of this sequestration potential of the land puts the net carbon calculation at -9.46 MgC/ha over 40 years. This negative net carbon value indicates that more net carbon would be emitted with Brunner M.S. Thesis iii the biorefinery than without it. This analysis indicates that when considering NIPF forest land in Michigan, greater net C sequestration can be achieved through forest growth than through harvest of woody biomass for cellulosic ethanol production.